THE DESIGN, PROTOTYPE DEVELOPMENT

AND CONCEPT VALIDATION OF A

CHILE SORTING MACHINE

BY

RYAN HERBON, B.S.

A thesis submitted to the Graduate School

in partial fulfillment of the requirements

for the degree

Master of Science Industrial Engineering

New Mexico State University

Las Cruces, NM

May 2003

2003 by Ryan Herbon

ii

The Design, Prototype Development and Concept Validation of a Chile

Sorting Machine, a thesis prepared by Ryan Herbon in partial fulfillment of

the requirements for the degree, Master of Science, has been approved and

accepted by the following:

Dr. Linda Lacey Dean of the Graduate School Dr. Edward Pines Chair of the Examining Committee Date Committee in charge:

Dr. Edward Pines, Chair Mr. Anthony Hyde, M.S. Dr. Jim Libbin Dr. Linda Riley

iii

VITA

June 17, 1979 Born at Long Beach, California

1997 Graduated from Aliso Niguel High School, Aliso Viejo, California

2000-2001 Student Shop Assistant, Manufacturing Technology and Engineering Center (M-TEC), Student Project Center, New Mexico State University

2001 Received Bachelor of Science in Engineering Technology From New Mexico State University Las Cruces, New Mexico

2001-2003 Project and Design Engineer, Manufacturing Technology and Engineering Center (M-TEC), New Mexico State University

iv

ABSTRACT

THE DESIGN, PROTOTYPE DEVELOPMENT AND CONCEPT

VALIDATION OF A CHILE SORTING MACHINE

BY

RYAN HERBON, B.S.

Master of Science Industrial Engineering

New Mexico State University

Las Cruces, New Mexico, 2003

Dr. Edward Pines, Chair

The Design, Prototype Development and Concept Validation of a

Chile Sorting Machine details the process that went into the design,

development and fabrication of a prototype machine capable of sorting sticks

and other foreign material from mechanically harvested red chile peppers.

The New Mexico Chile Pepper Task Force funded this project in an effort to

assist the processors and producers of red chile in the State of New Mexico.

Chile is grown on 20,000 acres in New Mexico and contributes $418 million to

the States economy.

This project went through four distinct stages consisting of research,

design, prototype development and testing to arrive at an effective design.

v

After research completion, the design began using the Funnel Approach to

Design methodology along with extensive solid modeling and computer

simulation. Prototype development was centered on two major features, the

gap-belt and the color sorter. Upon completion of the prototype, testing,

concept validation and result tabulation where completed in December 2002.

It was found that through the implementation of the chile-sorting machine,

significant reductions could be made in the amount of sticks present in

mechanically harvested chile.

vi

Table of Contents

LIST OF FIGURES ......................................................................................... ix

LIST OF TABLES ......................................................................................... xiv

INTRODUCTION.............................................................................................1

Problem Statement ......................................................................................1

Background..................................................................................................3

Research......................................................................................................7

Cleaning Methods from other Industries...................................................7

Mechanical Harvesters...........................................................................10

Chile Trash .............................................................................................16

Current Cleaning Methods......................................................................18

Rienk Table.........................................................................................19

Modified Rienk Table ..........................................................................20

Air Blower ...........................................................................................22

Finger Rake ........................................................................................24

Rock Tank...........................................................................................25

Counter-Rotating Rollers ....................................................................25

Centrifugal Blower ..............................................................................26

Patented cleaning methods ....................................................................27

Research Summary................................................................................32

METHOD.......................................................................................................34

Initial Design Considerations......................................................................34

vii

Funnel Approach to Design........................................................................37

Chile Sorting Design Using FAD................................................................39

Step 1: Design Requirement ..................................................................39

Step 2: Existing Elements from Research ..............................................39

Step 3: New Elements from Brainstorming.............................................40

Step 4: Product Constraints....................................................................45

Step 5: Combined or Mixed Ideas ..........................................................48

Step 6: Project Constraints.....................................................................49

Non-Tangible FAD Results .................................................................51

Step 7: Prototype Development..............................................................52

Gap-Belt Design .................................................................................52

Color Sorting.......................................................................................58

Color Sensing Concepts..................................................................58

Sensors .......................................................................................58

Machine Vision ............................................................................60

Sensing Methodology ..................................................................61

Color Sorter Removal Concepts......................................................63

Existing Color Sorters......................................................................66

Coffee Bean Color Sorters...........................................................67

WECO Color Sorter .....................................................................69

Operation .................................................................................69

Variables ..................................................................................71

Integration of the Design Elements.....................................................74

viii

Step 8: Prototype Construction...............................................................80

Design Process Summary using FAD........................................................88

TESTING.......................................................................................................90

Test Procedure ..........................................................................................90

Data Collection...........................................................................................93

Chile Sorting Machine Results .................................................................103

Gap Belt Results and Observations..................................................103

Color Sorter Results..........................................................................105

CONCLUSIONS ..........................................................................................107

Technical..................................................................................................107

Economic Impact .....................................................................................110

RECOMMENDATIONS FOR FUTURE WORK ...........................................117

APPENDIX A PROJECT SCHEDULE......................................................124

APPENDIX B CAD DRAWINGS OF THE CHILE SORTING STATION ...129

APPENDIX C THE CENTRIFUGAL BLOWER.........................................136

APPENDIX D THE ADJUSTMENT OF PROTOTYPE VARIABLES.........156

REFERENCES............................................................................................159

ix

LIST OF FIGURES

Figure 1: Mechanically harvested red chile with high trash content.................3

Figure 2: Relatively clean mechanically harvested red chile ..........................4

Figure 3: Hand laborers removing sticks from mechanically harvested red chile...........................................................................................5

Figure 4: The USDA tumbler cleaner...............................................................6

Figure 5: A color sorter designed for use on tomatoes ..................................10

Figure 6: The Boese harvesting machine ......................................................11

Figure 7: The open double helix picking head of a Boese harvesting machine.........................................................................................12

Figure 8: The McClendon chile harvester......................................................13

Figure 9: The open-helix picking head on the McClendon harvester.............14

Figure 10: The Pik Rite pepper harvester......................................................15

Figure 11: The Pik Rite harvesting head .......................................................15

Figure 12: Sonora chile plant.........................................................................17

Figure 13: The popular Rienk table or leaf rail cleaning system with .625 in. spacing .....................................................................................20

Figure 14: The modified Rienk table with a spacing of 1.625 inches to allow pods to fall through and walk sticks off the end....................21

Figure 15: A bottom view of the Boese machine's modified Rienk table .......22

Figure 16: The air blower on the Boese harvester.........................................23

Figure 17: The finger rake cleaning system on the Boese harvester.............24

Figure 18: Counter-rotating rollers cleaning method (Wolf & Alper, 1984) ....25

Figure 19: The centrifugal blower concept design .........................................26

x

Figure 20: The fabricated centrifugal blower bench model ............................27

Figure 21: The helix picking head covered under 1971 Patent # 3,568,419 ......................................................................................28

Figure 22: A top view of the Rienk table patented in 1985 by Patent # 4,507,911 ......................................................................................29

Figure 23: The star-shape Rienk table disc (Patent # 4,507,911)..................29

Figure 24: The cleaning apparatus patented by Rutt and Zook in 1995 ........30

Figure 25: The gapped rod, cleaning device described by patent # 5,287,687 ......................................................................................31

Figure 26: A depiction of the blower cleaning system patented by Oren and Daryl Urich..............................................................................32

Figure 27: An example of the stick trash in mechanically harvested red chile ...............................................................................................35

Figure 28: The Funnel Approach to Design...................................................38

Figure 29: Chile diverting concept .................................................................41

Figure 30: Air separation gap-belt concept ....................................................42

Figure 31: The concept of winnowing the chile material as is done in wheat.............................................................................................42

Figure 32: Vacuum plate concept ..................................................................43

Figure 33: The vacuum plate concept simulated ...........................................44

Figure 34: The gap-belt concept....................................................................45

Figure 35: A force diagram illustrating the forces acting on material located on the incline belt ..............................................................54

Figure 36: Gap belt adjustment mechanism detail.........................................55

Figure 37: The incline belt, variable speed V-belt aligning system ................57

Figure 38: The R55 color sensor from Banner Engineering ..........................59

Figure 39: Lego machine vision concept model.............................................60

xi

Figure 40: The vacuum concept illustrating the action of the vacuum arm moving down to pick up a pod from the material belt.....................65

Figure 41: The vacuum concept illustrating the up stroke of the air cylinder while the four-bar mechanism sweeper knocks the pod from the vacuum tip onto the pod belt ....................................65

Figure 42: The Sortex Niagara color sorting machine ...................................67

Figure 43: The Xeltron color sorting machine................................................68

Figure 44: The operating principles of the WECO color sorter ......................70

Figure 45: The sensor array and reject fingers on the WECO color sorter ....71

Figure 46: The WECO color sorter adjustment panel ....................................72

Figure 47: The box dumper and draper that feed the chile cleaning station............................................................................................75

Figure 48: The design of the incline belt feeding the gap-belt cleaning station............................................................................................76

Figure 49: The designed gap-belt cleaning station interface .........................76

Figure 50: The design of the spreader shield used to spread out the material that has fallen through the gap over the entire 40 inches of the color sorter belt ........................................................77

Figure 51: The design of the spreader bar used to flatten the flow of material into the color sorter ..........................................................78

Figure 52: The control box of the chile-sorting machine that housed the speed controllers for all five motors ...............................................79

Figure 53: The fabrication of the trash belt ....................................................80

Figure 54: The fabrication of the spreader bar...............................................81

Figure 55: Fabrication of the incline belt ........................................................81

Figure 56: A side view of the completed chile-sorting machine .....................82

Figure 57: The final design of the chile-sorting machine to allow for a comparison with the constructed prototype ...................................82

xii

Figure 58: A front view of the completed chile-sorting machine.....................83

Figure 59: Sticks removed vs. pods lost through 20 batches of the gap belt testing .....................................................................................96

Figure 60: The average results of the gap-belt testing ..................................97

Figure 61: The Percentage of rejected material through 20 batches during the testing of the color sorter. ...........................................101

Figure 62: The average results of the color sorting testing..........................102

Figure 63: The retail cost of a chile-sorting machine as affected by level of production................................................................................113

Figure 64: Proposed chute method for the alignment of material on the incline belt ...................................................................................119

Figure 65: Proposed placement of Reject Box to eliminate the stick length constraint of the WECO Color Sorter................................123

Figure 66: The design of the centrifugal blower..........................................136

Figure 67: The manufactured centrifugal blower prototype .........................137

Figure 68: The drive mechanism of the Centrifugal Blower .........................138

Figure 69: Detail of the friction drive wheel..................................................139

Figure 70: The helix shelf of the Centrifugal Blower ....................................140

Figure 71: The intended arrangement of material on the helix shelf of the Centrifugal Blower .......................................................................140

Figure 72: The air first nozzle used on the Centrifugal Blower ....................141

Figure 73: The second air nozzle used on the Centrifugal Blower...............142

Figure 74: Percentage of chile pods exiting through the bottom of the rotating drum during trials of three separate, random batches of material through the Centrifugal Blower ..................................146

Figure 75: Percentage of sticks exiting through the bottom of the rotating drum during trials of three separate, random batches of material through the Centrifugal Blower ......................................147

xiii

Figure 76: Percentage of chile pods stuck on the helix of the rotating drum during trials of three separate, random batches of material through the Centrifugal Blower ......................................148

Figure 77: Percentage of sticks stuck on the helix of the rotating drum during trials of three separate, random batches of material through the Centrifugal Blower ....................................................149

Figure 78: Percentage of chile pods stuck at the bottom of the rotating drum during trials of three separate, random batches of material through the Centrifugal Blower ......................................150

Figure 79: Percentage of sticks stuck at the bottom of the rotating drum during trials of three separate, random batches of material through the Centrifugal Blower ....................................................151

Figure 80: Material arranged on the helix shelf of the Centrifugal Blower ..154

xiv

LIST OF TABLES

Table 1: A classification of the trash present in mechanically harvested

red chile.........................................................................................36

Table 2: The product constraint filter of the FAD process..............................47

Table 3: The remaining design concepts before project constraints..............49

Table 4: The results of the project constraint filter .........................................50

Table 5: The parts and materials ordered from McMaster-Carr for the prototype construction of a chile-sorting machine .........................85

Table 6: The material ordered from Pipe and Metal Supply (PMS) for the manufacture a chile-sorting system prototype ...............................86

Table 7: Parts loaned to the Chile Task Force for the purpose of testing the chile-sorting prototype .............................................................86

Table 8: The labor costs that were used in the construction of the prototype .......................................................................................86

Table 9: Total Costs incurred in the fabrication of the chile sorting machine prototype.........................................................................87

Table 10: Gap-belt results for removal of sticks longer than 8 inches ...........94

Table 11: Gap-belt results of chile pods (small sticks removed)....................95

Table 12: Test results of color-sorter stick removal .......................................98

Table 13: Test results of color sorter removal of discolored pods..................99

Table 14: Test results of color sorter pod loss.............................................100

Table 15: The variables used in the testing of the gap belt .........................104

Table 16: Color sorter variables used at testing ..........................................106

Table 17: Estimated labor cost to manufacture a chile cleaning station similar to the project prototype assuming 80 hours of labor ........111

xv

Table 18: An estimated total cost for a manufacturing company to manufacture a chile cleaning station similar to the project prototype .....................................................................................112

Table 19: Variables used in the calculation of yearly machine cost for a processor or producer .................................................................114

Table 20: The total yearly cost of a chile-cleaning machine to a processor or producer .................................................................114

Table 21: The variables used in the overall economic impact calculations..115

Table 22: The economic impact of a chile-cleaning machine to an individual user and the industry as a whole .................................115

Table 23: Recommended screening process ..............................................117

Table 24: The first batch test results of the centrifugal blower testing .........144

Table 25: Batch 2 Test Results of the Centrifugal Blower ...........................144

Table 26: Batch 3 Test results of the Centrifugal Blower.............................144

1

INTRODUCTION

Problem Statement

The chile industry annually contributes $418 million in economic

activity in New Mexico (Hall and Skaggs, b). However, scarcity of available

labor, increasing labor costs and a 35% loss of chile acreage to Mexico and

other foreign competitors since 1994 are threatening the domestic industrys

survival (Hall and Skaggs, b).

In 1998, the New Mexico Chile Task Force (NMCTF) was formed to

explore ways that new ideas and technologies could help increase the

industrys profitability. The Task Force has more than 100 active members

from private, corporate, state and federal organizations. They represent

growers, processors, researchers, Extension personnel and members of

agricultural support industries (Diemer, Phillips & Hillon, 2001). New Mexico

State Universitys (NMSU) College of Agriculture and Home Economics

coordinates NMCTF efforts.

The NMCTF has identified widespread adoption of machine harvest

technologies as the most important change that the industry must make.

Machine harvest efforts to date have realized considerable success, but that

success has been offset somewhat by the amount of trash and debris

2

introduced into the harvested product. This debris must be removed by hand.

Therefore, NMCTF members have given a high priority to efforts to

developing effective methods of mechanical trash removal (Salton and

Wilson, 2003). In October 2001, the NMCTF asked the Manufacturing

Technology and Engineering Center of NMSUs College of Engineering to

assist in developing a mechanical cleaner. M-TEC saw the project as way to

aid its mission of supporting economic development within the state through

technical assistance. M-TEC agreed to support a graduate student who

would lead the project and report the results in a masters degree thesis.

The focus of this project is to design and build a prototype machine to

effectively remove trash from mechanically harvested red chile without

harming the product. The purpose of the prototype machine is to validate the

design concepts to determine which cleaning processes should be

incorporated into a production-level machine.

This thesis provides documentation for the Chile Task Force. The

information it contains will be disseminated to New Mexico chile producers

and processors.

3

Background

Several equipment manufacturers design and manufacture harvesting

equipment for the red chile industry. While the machines effectively remove

the chile pods from the plants, they also remove an abundance of sticks,

leaves and other debris with the product (Martin, 2002). Chile trash becomes

a liability when it goes to a processing plant because it causes degradation of

chile quality and poses the possibility of damage to expensive processing

equipment (Dave Layton, personal communication, 10/4/2001). Depending

on the time of year that harvest occurs, trash can be a major liability (Figure

1) or a relatively minor problem (Figure 2).

Figure 1: Mechanically harvested red chile with high trash content

4

Figure 2: Relatively clean mechanically harvested red chile

Since 1965, researchers and scientists have experimented with

mechanical sorting methods, with limited success (Marshall, 1984).

Currently, sticks are hand-removed from chile pods in the processing plant.

This method poses two significant problems for processors. The first is that

the cost of employing approximately 15 laborers to remove debris from chile

pods (Figure 3) as the pods are off-loaded from the truck via a conveyor belt.

Hand-labor accounts for 40-60% of chile production cost (Martin, 11/12/2001).

In 2001, it was estimated that hand labor costs $65 a day in the U.S. versus

$6 a day in Mexico (Martin, 11/14/2001). That cost differential makes

competing with Mexican imports extremely difficult (Diemer, Phillips & Hillon,

2001). The second problem is the removal of discarded material from the

processing plant. Debris left in the field may be plowed under to amend the

5

soil for the following years crop. Once it reaches the processing plant, it

must be treated as industrial waste, incurring significant disposal costs.

Figure 3: Hand laborers removing sticks from mechanically harvested red chile

The NMCTF began the chile debris removal initiative in 1998 to

complement the mechanical harvesting process. The first cleaning system

developed through the task force was a device, called a tumbler sorter

(Figure 4), developed by the United States Department of Agriculture,

Agricultural Research Service (USDA, ARS) Southwestern Cotton Ginning

Research Laboratory. A thorough description of the machine can be found in

the Research section of this document. The machine currently does not

work as effectively the chile industry requires.

6

Figure 4: The USDA tumbler cleaner

Because of the sorting machines limited success, the Chile Task

Force was open to new ideas for solving the problem. This led to the initiation

of the research phase of this project to develop an understanding of the

problem that would help generate new, innovative solutions.

7

Research

To obtain information needed to design an effective machine, research

was conducted in five areas: (1) cleaning methods from other industries, (2)

mechanical harvesters, (3) the type of trash found in mechanically harvested

chile, (4) cleaning equipment currently being used and (5) cleaning equipment

that had been tried and patented. The following section contains the results

of the research in these areas.

Cleaning Methods from other Industries

The problem of having trash mixed in with mechanically harvested

crops is a problem that is not unique to the chile industry. In fact, the majority

of mechanically harvested crops have had to overcome this same problem.

Perhaps the most popular example is that of cotton. It took many years for

the ginning process to be effective enough to use widespread mechanical

harvesting. According to Ed Hughs, the Director of the USDA, ARS

Southwestern Cotton Ginning Research Laboratory, the trash removal

process in the chile industry is about 40 to 50 years behind that of the cotton

industry (Ford, 1999). Cotton is one of Americas largest market crops, grown

on more than 16 million acres in the U.S. (Cotton Background, 2002). Chile,

on the other hand, is grown on only 28,000 acres in the United States, with

20,000 of those acres being in New Mexico (All About Chiles, 2002). Farm

8

implement companies saw a valuable market for cotton harvesting

equipment. The chile industry, however, is not deemed large enough to

generate a return on R&D dollars spent in the area of chile machine harvest

(Lenker, 1984).

When cotton is harvested, sticks and seeds are present in the product.

This foreign matter makes up between 1,000 and 2,100 pounds per 500-

pound bale of cotton fiber (Ed Hughs, personal communication, 3/17/2003).

Different types of cleaners are used to remove different types of debris (Holt,

Baker & Brashears, 2002). Small debris, such as leaves, is removed by

conveying the material across an airline after breaking it up with a series of

spiked cylinders. The burs and sticks then are removed by stripping them

from the cotton by using a saw cylinder to seize and pull the cotton across a

series of mechanical scrubbing devices or cleaning bars (Research on

Machinery Management and Process Control for Cotton Gins, n.d.).

Unwanted debris accounts for about 5% of the total lot weight of

mechanically harvested peanuts (Suszkiw, 2001). To sort peanuts from the

debris, such as plant stems, rocks and dirt, the material is fed across three

layers of screens, similar to those used to screen gravel (Blankenship and

Woodall, 1997). Rotating drums made out of mesh material are used to

remove small debris from the peanuts. The mesh drums filter debris attached

to the peanut pods.

9

The separation of dirt clods from mechanically harvested onions can

be accomplished in a unique way. The material falls from the end of a belt

onto a spinning steel roller. When the onions and clods rebound from the

roller, they follow different trajectories. This allows for separation because the

onions travel farther than the clods. This process is then repeated over three

stages. Each stage removes more dirt clods as well as more onions (Coble,

1984).

There are many other examples of cleaning and sorting of crops.

Cranberries are sorted by bouncing them along a bouncing board. The

material that bounces is kept and the material that doesnt bounce is not kept

(Cranberry Bog Tour, n.d.). Blueberries are sorted using a combination of

vibration and an air blower (Donahue, Bushway, Moore and LaGasse, 1999).

The trash problem was taken care of in baby greens by changing

management practices, such as changing their rotation crops (Wood, 2002).

Color based sorting has been used in many crops, although it has not

been used for debris removal. Typically, color is used to sort different colors

of a single product, such as green from red tomatoes, red from green

jalapenos or red from white wheat (Pasikatan & Dowell, 2002). A color sorter

designed for use on tomatoes is shown in Figure 5. Color sorting machines

are used to sort coffee beans, onion flakes, nuts, rice and different types of

seeds. Color sorters also have been used to sort fungi-infected peanuts and

defective pistachios (Pearson & Doster, 1998).

10

Figure 5: A color sorter designed for use on tomatoes

Mechanical Harvesters

Even though the harvesting process is out of the scope of this project,

research was conducted into the harvesters as a way to fully understand the

origin of the trash problem. Currently, there are three major manufacturers of

chile harvesting equipment: Boese, McClendon and Pik Rite Harvesters.

There are numerous differences among these three machine types in how

they harvest and clean the chile.

11

Figure 6: The Boese harvesting machine

The Boese Harvesting Company of Saginaw, Michigan, builds a self-

propelled machine (Figure 6) tailored specifically for the harvesting of chile

peppers. The Boese machine uses a counter-rotating, double-helix picking

head (Figure 7). As the helixes rotate in opposite directions and the machine

moves along the row of chile plants, the plants pass directly between the set

of helixes. As this occurs, the helixes pull the material outward, removing the

pods from the plant. The pods are removed by the combination of the pulling

motion and the vibration that the helixes cause. The pods then land on a set

of conveyor belts on each side of the double helix where they are conveyed

into the machines cleaning apparatus. The Boese machine sends the

harvested material through numerous cleaning processes, including a

12

conveyor-belt cleaning table, to allow hand labor to remove trash from the

pods.

Many regard the Boese machine as the most effective harvester

available because of the multiple cleaning methods incorporated. However,

the cleaning processes also are the source of most complaints about the

machine because the many hydraulically actuated motors make

troubleshooting problems difficult and time consuming. A Boese Harvester

costs approximately $360,000 (Greg Boese, personal communication,

2/5/02).

Figure 7: The open double helix picking head of a Boese harvesting machine

13

Figure 8: The McClendon chile harvester

McClendon harvesters, made in Tulia, Texas, employ a picking head

similar to the Boese machine. The McClendon machine (Figure 8), is a John

Deere cotton picker to which is attached a chile harvesting picking head

manufactured by McClendon. It uses the same counter-rotating, double helix

concept. It, however, has four helixes per row (Figure 9), as opposed to the

Boeses two helixes. The helixes also can be exchanged for fingers to pick

different types of chile. After harvest, the material is transported from the

helixes across minimal cleaning equipment that cleans out small debris

before it is loaded into a holding basket on the machine. McClendon

machines cost about $240,000 (Jim McClendon, personal communication,

2/5/02).

14

Figure 9: The open-helix picking head on the McClendon harvester

The Pik Rite machine (Figure 10) uses a picking mechanism that is

significantly different from that used by McClendon and Boese. It uses two

belts with finger rakes that comb opposite sides of the chile plant. The finger

rakes (Figure 11) lift the plant material, stripping the pods from the plant. This

harvest method is considered most thorough. It leaves few pods in the field

because it can grab everything that has fallen onto the ground as well as the

material stripped from the plant. It also incurs highest amount of trash

content because of its harvesting method. The machine incorporates

15

numerous cleaning methods and a hand cleaning station. The Pik Rite

machine is not self-propelled and requires a tractor to pull it. The machine

costs $130,000 (Jim McDonnel, personal communication, 2/5/2002).

Figure 10: The Pik Rite pepper harvester

Figure 11: The Pik Rite harvesting head

16

Each harvester brand is effective at getting chile pods off of the plant

and each introduces large amounts of trash into the product. This problem is

compounded late in the season, after the first frost kills the plants (Hall &

Skaggs, a). At that point, it is not uncommon for the machines to remove

entire plants from the ground.

Chile Trash

There are several factors that affect the amount of trash in

mechanically harvested chile. The two major factors, besides the brand of

machine used to do the harvesting, are the variety type and the time of

season harvested. B-18 has higher success with machine harvesting

because its pods are removed easily from the plant. Sonora plants (Figure

12) are difficult to separate from the plants (Wall, 2002). Machine harvested

Sonora contains substantially more plant debris (Hall & Skaggs, a). Plant

varieties with an upright habit and an even fruit distribution with fruit sets eight

or more inches above the ground harvest most effectively, with less trash

(Ford, 2000). This is to say that there is a better ratio of pods to sticks.

Harvesting is also improved by having a reduced number of lateral shoots

below the main branching (Palevitch & Levy, 1984).

17

Figure 12: Sonora chile plant

While chile harvesting typically takes place from September to the end

of December, the plant characteristics change distinctly after the first frost.

The first hard frost in southern New Mexico generally occurs in October

(DeWees, 1998). The plants become very brittle after the frost, increasing

exponentially the amount of sticks that break off and are pulled into the

system by the harvester. Chile harvested after the frost is also more difficult

to clean because the weight, density and shape of the pods match more

closely that of the sticks. Throughout the season, the moisture content of the

pods decreases from 7:1 at the beginning of the season to 2:1 at the end

(Rich Phillips, personal communication, 2/4/2002). According to chile

processor Lou Biad, many producers park their mechanical harvesting

18

machines after the frost because it costs more to separate the trash from the

harvested pods than it does to pay a hand harvest crew to harvest the crop

(personal communication, 9/11/2002).

Currently processing plants in the region do not have the volume

capability to process the entire New Mexico chile crop between September

and the first frost. They must lengthen the season into December and

sometimes January in order to level production. To effectively do so, better

cleaning equipment needs to be introduced. The season cannot be extended

earlier into the year because soil temperatures are too low for the germination

of the seeds before the middle of March (Bob Bevacqua, personal

communication, 10/9/2002).

Current Cleaning Methods

The predominant cleaning method, used in almost every situation, is

hand labor. As the material comes into a processing plant, it moves down

conveyor belts where hand laborers remove the sticks from the pods. In

addition, the Boese and Pik Rite harvesting machines incorporate hand-

cleaning stations. Using hand labor for cleaning is not only expensive, but

also dangerous for the workers who may encounter poisonous snakes and

other dangerous elements among the product being sorted.

19

Rienk Table

Currently, several types of cleaning equipment are used widely.

Perhaps the most prevalent is the Rienk table (Figure 13). The Rienk table,

also known as a square tumbler or a leaf rail, is used to sort small trash from

the harvested chile. It has been used since the 1940s (Richey, 1961) for

cleaning dirt from sugar beets (Danisco, 1997). The machine has multiple

rotating shafts with plastic squares mounted on them. Alternatively, spinning

stars have been used for the cleaning of sugar beets (Smith, 1965). The

plastic squares are offset so that the squares from one shaft fit between the

squares on the next shaft. The desired spacing can then be attained by

adjusting both the distance between the shafts and the distance between the

squares on each shaft. Typically, the spacing interval is small enough so that

the pods are conveyed along the top and the trash that is smaller than the

pods falls through and is discarded (Abernathy & Hughs, 2001b). This type of

cleaning equipment is used in most processing plants and on each of the

McClendon, Pik Rite and Boese mechanical harvesters. It has been proven

to be a very effective method for removing small trash from the mechanically

harvested chile.

As the squares rotate, the rotating motion acts as a conveyor, moving

the material from the input to the output side. Using the square shape, the

gaps between squares and the adjacent shafts increase and decrease with

the motion of the squares, allowing the trash to fall through. The cleaning is

20

aided by the bouncing effect attained by the material moving up and down

with the spinning of the squares.

Figure 13: The popular Rienk table or leaf rail cleaning system with .625 in. spacing

Modified Rienk Table

A variation of the Rienk table has been used to separate out trash that

is longer than the pods (Figure 14). This method is employed on Boese and

Pik Rite harvesters and on the research cleaner designed and built by the

USDA, ARS Southwestern Cotton Ginning Research Laboratory. On their

prototype machine, USDA researchers used the same squares as those on

the standard Rienk table, but added more spacing between them. The

spacing is set at 1.625 inches, compared to 0.625 inches on the standard

Rienk table (Abernathy & Hughs, 2002b).

The purpose of the modified table is to convey the sticks that are

longer than the pods off of the table and allow pods and trash smaller than

21

pods to fall through the gaps. The modified Rienk table on the Boese

harvester basically uses the same method but with different-shaped spinning

disks and much more spacing between the shafts. Instead of squares, the

Boese machine uses a finger-shaped spinning media (Figure 15). The Pik

Rite harvester uses a similar system.

Figure 14: The modified Rienk table with a spacing of 1.625 inches to allow pods to fall through and walk sticks off the end

The testing of the modified Rienk table has had mixed results. It does

not always remove all of the trash that is longer than chile pods. Sticks that

are long and straight often turn vertically and fall through the spacing, rather

than being carried along to the discharge section as intended. The table is

however very effective at removing whole plants or sticks with multiple pods

attached.

22

Figure 15: A bottom view of the Boese machine's modified Rienk table

Air Blower

Boese and Pik Rite Harvesters and several farms truck-loading

conveyors use an air blower type of cleaning method. The Boese machines

blower is depicted in Figure 16. It blows a stream of air across harvested

material as it falls from a conveyor, diverting lighter material, such as leaves,

into a different container. The air blower method has acceptable results for

separating out leaf material and pods gutted by insect infestation, but it has

not been effective for sorting heavier types of trash (Joel Tellez, personal

communication, June 11, 2002).

23

Figure 16: The air blower on the Boese harvester

Researchers at the USDA, ARS Southwestern Cotton Ginning

Research Laboratory conducted experiments to determine if an air blower

could be used to sort the sticks from pods based on their relative cross

section to the airflow and relative masses. The results were inconclusive,

with varying rates of separation effectiveness. (Abernathy and Hughs, 2001a)

Moisture content was a major factor in the varying results. Early in the

season, moisture is as high as 7:1, water to chile, making pods much heavier

than the sticks. Because the plants are more pliable, the harvesters are

much more effective and the cleaning is not as critical. Toward the end of the

season, the moisture drops to about a 2:1 ratio (Rich Phillips, personal

communication, 2/4/02), making the pods approximately the same weight as

the sticks. Because plants are brittle, more sticks are harvested and the

weight similarity of sticks and pods makes air separation difficult.

24

Finger Rake

A cleaning method that has been implemented on the Boese

harvesting machines is the finger rake (Figure 17), which strips pods that are

attached to sticks. The fingers are bolts protruding outward from three

counter-rotating drums. The bolts are offset so that as the material is carried

by one drum, the other strips across it, pulling off the pods. The material is

brought into this system by offsetting the first drum from the cleated conveyor

belt that is transporting the harvested material into the machine. This allows it

to grab anything that is over a certain height.

Figure 17: The finger rake cleaning system on the Boese harvester

25

Rock Tank

Chile processing plants generally include a rock tank in their cleaning

processes. The rock tanks purpose is to float the chile across a water bath,

washing the product and allowing heavy trash, such as rocks, to fall to the

bottom. The rock tank also accumulates much of the dirt from the product

and generally needs to be drained several times daily (Vince Hernandez,

personal communication, 9/26/2002).

Counter-Rotating Rollers

Another method of removing attached pods from sticks is to convey the

material through spring-loaded, counter-rotating, rubber-studded rollers

operating at 100 rpm. This conveys the attached pods and sticks into two

pairs of picking elements operating at 1000 rpm (Figure 18). The detached

material, as well as sticks, then falls back onto a conveyor with the material

that was not drawn into the cleaner (Wolf & Alper, 1984).

Figure 18: Counter-rotating rollers cleaning method (Wolf & Alper, 1984)

26

Centrifugal Blower

Another cleaner design that was proposed by M-TEC engineers in

Spring 2002 used a combination of centrifugal force and an air stream to

separate the material within a cylindrical container. The premise was that the

centrifugal force would cause all of the material to arrange itself around the

outside of the container where a ledge was welded to the container. Due to

the different arrangement of the sticks and pods on the ledge, the sticks were

to be blown out the top while the pods were to move to the bottom. A bench

model of this concept, named The Centrifugal Blower, was designed (Figure

19), built (Figure 20), tested and proved not to work. A report of this project is

included in Appendix C.

Figure 19: The centrifugal blower concept design

27

Figure 20: The fabricated centrifugal blower bench model

Patented cleaning methods

An extensive United States patent search was conducted to identify

any patented cleaning methods not in use currently. The majority of the

cleaning patents where part of overall harvester patents. Seven patents were

found that where related to chile harvesting and cleaning of chile peppers.

Descriptions of each follow.

The concept of using a helix head to harvest chile plants was originally

patented in 1971 by W.G Creager Chili Harvester (U.S. Patent #

3,568,419), detailed the use of flexible coils that were of the same type and

function as current helix heads.

28

Figure 21: The helix picking head covered under 1971 Patent # 3,568,419

In 1985, Isaac Wolf and Yekutiel Alper obtained a patent for

Apparatus for Harvesting and Separation of Produce, (U.S. Patent #

4,507,911). Wolf and Alper summarized the implementation of a vegetable

harvester that included variations of the open double-helix picking head and

Rienk table (Figure 22). It also included a description of a separation method

for detaching attached pods by contacting them with a pair of rollers,

essentially running the stem through a ringer. The Rienk table described is

essentially the same one currently used; however, instead of spinning

squares, it used spinning stars (Figure 23).

29

Figure 22: A top view of the Rienk table patented in 1985 by Patent # 4,507,911

Figure 23: The star-shape Rienk table disc (Patent # 4,507,911)

Both Larry Rutt with Robert Zook and Robert Cosimati patented

cleaning machines that use cylinders made of rotating rods. Rutts patent,

30

Cleaning Apparatus, (Patent # 5,427,573) describes a cleaning system

intended to remove sticks and leaves that consists of a rotating cylinder made

of spaced-out rods (Figure 24). Some of the cylinders rods are gear-driven

by the cylinder ends so that they rotate in relation to the rotational speed of

the cylinder. The remaining rods are idlers that are allowed to spin freely as

the drum rotates. The machine also has a rotating auger brush in the center

that conveys the peppers from one end of the cylinder to the other. The

intention is to allow the trash to fall through the gaps while the pods are

conveyed to the end of the drum. Cosimatis device, Patent # 5,210,999,

lacks the internal brush and puts the cylinder on an incline. It also uses

compressed air to aid in the sorting.

Figure 24: The cleaning apparatus patented by Rutt and Zook in 1995

Contained within the patent of a harvester (Patent # 5,287,687),

inventors Oren, Gary and Randy Urich described a similar cleaning method, a

31

table of counter rotating rods. The rods are spaced to allow sticks but not

pods to be pulled through (Figure 25). It is on a table as opposed to the drum

shape of the previously described patents. A similar system was included in

Greg Boeses 2002 patent of a harvest machine (Patent # 6,419,093). Within

his patent, the rollers are described as being adjacent in an attempt to pull

leaves and sticks through, conveying the pods along the top.

Figure 25: The gapped rod, cleaning device described by patent # 5,287,687

In Patent # 5,930,987, Oren and Daryl Urich describe a method of

trash removal similar to that which is employed on the Boese harvester. They

describe using an air stream, acting perpendicularly to the material flow, to

blow off small trash that is lighter than pods (Figure 26).

32

Figure 26: A depiction of the blower cleaning system patented by Oren and Daryl Urich

Research Summary

Although the chile industry has tried many mechanical solutions, they

have not yet developed a clear-cut method for removing all unwanted debris.

The debris problem is a moving target and varies dramatically depending on

when during the season chile is harvested and which machine type is used.

In addition, there is no current system that accurately defines the

classification of the trash material to note the effectiveness of various

machines.

The following information is a summary of key points of the research:

All currently used mechanical harvesters introduce trash. Existing equipment only works well on certain aspects of

cleaning and could be incorporated as part of a screening

process.

33

Existing or commercial machines fail to remove sticks that are longer than pods and sticks that are the same size as pods.

Other industries have successfully used modern technology to overcome similar problems.

Color Sorting Technology may be adaptable to the red chile sorting.

Most industries use multiple stages to remove trash.

34

METHOD

Initial Design Considerations

This project focused only on finding a solution for removing trash and

debris from machine harvested red chile. Red chile pods were considered

good product. Any material brought into the system other than red chile

pods, was defined as trash. This trash fits into five categories: leaves, dirt,

rocks, sticks and discolored pods. The amount of each depends on the type

of harvester used, the variety of chile and the time of year harvested. After

first frost, the increase in the number of sticks harvested becomes so

problematic that mechanical harvesting is almost infeasible. Processors often

reject chile harvested after frost due to the high trash content. For this

reason, the chile-sorting machine must be designed to work effectively after

the frost.

Currently, effective solutions exist for separating out the first three

categories: leaves, dirt and rocks. Therefore, these trash categories are

beyond the scope of this project. Of the last two categories (sticks and

discolored pods), the sticks, such as those seen in Figure 27, constitute the

majority of the trash problem. Sticks have the highest potential to damage

equipment and to degrade the quality of the red chile product. They also are

the most difficult to remove.

35

Figure 27: An example of the stick trash in mechanically harvested red chile

Sticks that are harvested with pods can be classified as follows: sticks

that are shorter than pods; sticks that are longer than pods; and sticks that

are the same length as pods. Within these classifications, there are multiple

subcategories: straight sticks; branched sticks (sticks with multiple nodes);

and sticks with pods attached to them. The latter category also encompasses

whole plants that are sometimes brought into the system by the harvester.

Table 1 lists trash classifications and methods currently available for

separating them from pods.

36

Table 1: A classification of the trash present in mechanically harvested red chile

Category Sub-Category Effective Cleaning Method

Leaves - Rienk Table Dirt - Rienk Table and Rock Tank Rocks - Rock Tank Discolored Pods - No Solution Exists

Sticks Shorter than pods and straight Rienk Table

Sticks Shorter than pods and forked No Solution Exists

Sticks Shorter than pods with attached pods Modified Rienk Table Removes Some

Sticks Same Size as pods and straight No Solution Exists

Sticks Same Size as pods and forked No Solution Exists

Sticks Same Size as pods with attached pods Modified Rienk Table

Sticks Longer than pods and straight No Solution Exists

Sticks Longer than pods and forked Modified Rienk Table removes some

Sticks Longer than pods with attached pods Modified Rienk Table

37

Funnel Approach to Design

The Funnel Approach to Design (FAD) is based on the premise that

the more ideas available for exploration at the beginning of the design

process, the more likely it is that a feasible solution will be found. An analogy

is that of a job search. A job opening is more likely to be filled with a qualified

candidate if a large pool of applicants is available. The timeline of the entire

design, development and concept validation was planned out before FAD

began (Appendix A).

FAD starts with new and existing ideas or inputs based on the design

requirements given by the customer. New ideas are generated through

brainstorming while existing ideas come from research. Both the new and

existing ideas are then filtered through the product constraints, eliminating

any that are infeasible or dont fall within the constraints. The remaining ideas

are analyzed further, researched, combined and filtered through the project

constraints to arrive at two or three concepts that are developed into

prototypes. Figure 28 shows how a large number of ideas can be reduced to

a few workable solutions through FAD.

38

Figure 28: The Funnel Approach to Design

39

Chile Sorting Design Using FAD

Step 1: Design Requirement

The Chile Task Force, considered the customer for this project, gave

the design requirement to M-TEC. The specific design requirement was to

design a machine that could sort red chile pods from sticks. The categories

of sticks that required immediate attention were straight long sticks and sticks

that were the same size as pods.

Step 2: Existing Elements from Research

The following existing elements came from research and the interviews

conducted with processors and producers:

o Rienk Table Uses spinning squares to remove small trash

o Modified Rienk Table Uses spinning disks to remove branched material

o Rotating rods with small gap between them Pulls sticks through the gap

o Saw cylinder Pulls cotton across a stripper bar

o Color-based defect sorters Remove a defective material based on color

o Bouncing Board Accepts material that bounces a certain way

o Best-Management practices Changing the way that the crop is grown to reduce the

number of sticks o Finger rake

Strips pods from attached sticks

40

Step 3: New Elements from Brainstorming

At the beginning of the project, a brainstorming session was held to

produce as many new ideas as possible. As the project matured, new ideas

were generated constantly.

One original idea was to bounce all of the material across a screen and

have a scraper under the screen to pull through any stick ends that stuck

through the screen. The hope was that an end of each stick would protrude

to the underside while the pods would stay completely on the top. The

scraper arm would then pull the stick completely through or cut off a portion of

it. If it cut a portion, then the next portion would need to stick through to be

cut or pulled. In this manner, even a non-straight stick could eventually be

removed one inch at a time.

Another idea was to attempt to arrange pods and sticks in a singular

layer and then devise an electronic method to sense pods and sticks and

divert them one way or another (Figure 29). A plus side to the concept is that

de-stemming could be integrated easily. De-stemming is a process that is out

of the scope of this project but is another that the chile industry would like to

mechanize.

41

Figure 29: Chile diverting concept

Another possible sorting method was to drop the harvested material off

a belt while quickly pulsing an air stream up and toward another belt. The

idea behind it was that material like chile, with a larger cross section would be

blown onto the second belt while other material would fall through the gap

(Figure 30). A similar concept explored was that of winnowing, such as wheat

is separated from chaff. This idea was to put all of the material in a large

container and puff large amounts of air from the bottom to keep the material

suspended (Figure 31). Again, the idea was that by having a larger cross-

section, the pods would eventually filter to the top while the sticks would be

suspended lower in the container.

42

Figure 30: Air separation gap-belt concept

Figure 31: The concept of winnowing the chile material as is done in wheat

43

Another idea explored was a vacuum plate (Figure 32). Numerous

small holes would be drilled in a metal plate and enough vacuum pressure

applied to the holes to hold a pod to the plate if the pod covered more than

four or five of the holes (Figure 33). It was thought that the flat shaped pods

would cover more holes than the narrower sticks. The plate could then be

moved elsewhere and the air pressure released, dropping off the pods. An

alternate method for using a vacuum plate would be to have sensors tell

exactly where pods were and then selectively control which vacuum holes

were to have vacuum applied via electronic valves.

Figure 32: Vacuum plate concept

44

Figure 33: The vacuum plate concept simulated

An alternate brainstormed idea was to run parallel V-belts with small

spacing between them, while vibrating the whole assembly. The pods were

to travel along the belts and the sticks were to fall through the gaps. The

premise was that the vibration would force the sticks into the gaps, where

they could pass through due to their narrower shape.

A similar idea created during the initial brainstorming was the use of a

gap belt. This concept included an inclined belt that would move harvested

material uphill toward a second trash belt. Material would be oriented

parallel to the direction of travel on the belt. Pods would fall through a gap

between the inclined belt and the trash belt, while sticks that were longer than

the gap between the belts would travel onto the trash belt (Figure 34).

45

Figure 34: The gap-belt concept

The following is a summary of the new ideas gathered through

brainstorming.

Pull sticks through a screen Divert pods and sticks based on sensor input Pulse an air stream toward material falling from a belt Winnow the material with an air stream within a container Vacuum plate Drop small trash between V-belts Gap-Belt

Step 4: Product Constraints

Three primary product constraints were involved in the design of the

machine. These constraints were that the sorter could not damage the pods

in any way; it must be able to maintain a flow rate of 48,000 lbs hr 1; and that

46

it must be capable of removing at least 80% of the sticks from the harvested

material. These product constraints were used to initially filter all of the

brainstormed and existing ideas.

It was very important not to break the pods with the cleaning machine.

The producers get paid based on product weight, and the seeds make up a

large portion of that weight. If the cleaning machine damaged the pods, there

would be a high likelihood that seeds would be lost from the product.

The second imposed product constraint was that the system had to be

adaptable to work with the current volume of chile being harvested and

processed. This would prevent the cleaner from becoming a bottleneck in the

production line. The typical volume that goes through a processing plant is

approximately 40 boxes per hour. Each box is 4 ft. by 4ft. by 4 ft. and

contains roughly 1,200 pounds of harvested material (Phillips 2/4/2002). This

is a total flow rate of 48,000 lbs hr -1.

Perhaps the most important product constraint is the requirement that

the machine remove 80% of the sticks. This 80% is a moving target that

changes drastically depending on many factors. Each individual customer

has a different interpretation of what percentages of sticks need to be

removed. Each also has been known to change the required percentage

depending on the current years production.

The results of passing the new and existing ideas through the product

constraints are summarized in Table 2.

47

Table 2: The product constraint filter of the FAD process

Product Constraints

Concepts

Does not harm the

pods

Can maintain 48,000 lb

h-1flow rate

Can possibly eliminate 80% of

the Sticks that are longer

than pods

Can possibly eliminate 80% of

sticks that are the

same size as pods

Does concept Passes Product constraint filter

Bounce on screen and pull sticks through No Yes Yes Yes No Winnow with air Yes Yes No No No Narrow flow and divert sticks based on sensor input Yes No Yes Yes No Long narrow screens for sticks to fall through Yes Yes No No No Blow pods across a gapped belt Yes Yes Yes Yes No Vacuum plate based on shape Yes Yes Yes Yes No Sensor guided vacuum plate Yes Yes Yes Yes Yes Centrifugal force separation Yes No No No No Vibrating v-belts with gaps between them Yes Yes No Yes Yes Gap-Belt Yes Yes Yes No Yes Rienk Table Yes Yes No Yes Yes Modified Rienk Table Yes Yes Yes No Yes Rotating Rods with gap between them No Yes Yes Yes No Saw cylinder No Yes No No No Color based defect sorter Yes Yes Yes Yes Yes Bouncing board Yes Yes No No No Best management practices Yes N/A Yes Yes No Finger rake No Yes No No No

48

Step 5: Combined or Mixed Ideas

In order to find an effective design solution, FAD uses the premise that

if several ideas can be combined into one, then the likelihood of it being

successful increases. For this project, it was possible to combine the gap-belt

with aspects of the V-Belts with gaps between them.

The gap belt requires all of the material to be oriented in the same

way. According to Vince Hernandez of Biad Chili, it is possible to achieve this

orientation by having a conveyor made of multiple V-belts, with alternating V-

belts traveling at different speeds. This method of alignment has been shown

to work in bell pepper processing plants because the faster belt causes one

end of the material to be grabbed and pulled while the other end is held in

place by the slower belt. This occurs until the material rests solely on either a

fast or slow belt and is aligned parallel to the direction of travel. This method

of alignment allows the integration of the V-belts with gaps between them

cleaning concept with the gap-belt cleaning concept. The only aspects that

differ from the original V-belt concept are that the V-belts are no longer going

to move at the same speed and the entire arrangement will be on an angle

rather than flat.

The concepts that remained after the combining and mixing of ideas in

the funnel are summarized in Table 3.

49

Table 3: The remaining design concepts before project constraints

Sensor guided vacuum plate New Idea

Gap-Belt combined with V-Belts with gaps Mixed Idea

Rienk Table Existing Idea

Modified Rienk Table Existing Idea

Color based defect sorter Existing Idea

Step 6: Project Constraints

The next filter the concepts went through was the project constraints

filter. The three project constraints were: 1) the production model machine

had to cost less than $50,000; 2) the machine must be complete for the 2002

harvesting season; and 3) the machine must incorporate ideas never before

tried in the chile industry.

The cost constraint was based on the fact that the machine had to be

affordable for an end user to purchase. The target was to have a production

model that could be purchased by a consumer for less than $50,000. It would

be infeasible for processors and producers to justify the purchase of a

machine that costs much more than that.

There was also a time constraint involved. The prototype had to be

manufactured so that the concept could be validated by the 2002 chile

season. Chile Task Force representatives identified this time frame to

50

demonstrate progress to members and to allow for the thesis to be completed

by April 2003.

The final project constraint filter was that the prototype had to use

innovative or new ideas. The Chile Task Force did not want the same ideas

that had been tried for the last 40 years to be tried again. Their feeling was

that if there was a mechanical way to remove the sticks, it would have been

discovered in the last 40 years. Task Force members felt very strongly that

the solution would be something that had not been tried, most likely because

of its high-tech nature.

Figure 3 summarizes the results of the conceptual ideas passing

through the project constraints.

Table 4: The results of the project constraint filter

Project Constraints

Concepts

Would cost less

than $50,000

Could be completed

by the 2002

harvesting season

Is an Innovative

(not previously tried) idea

for the chile

industry

Does the concept pass the Project Constraint Filter

Sensor guided vacuum plate No No Yes No Gap-Belt combined with V-Belts with gaps Yes Yes Yes Yes Rienk Table Yes Yes No No Modified Rienk Table Yes Yes No No Color based defect sorter Yes Yes Yes Yes

51

Non-Tangible FAD Results

The Funnel Approach to Design yielded several important non-tangible

results. After arriving at several existing and new ideas based on the design

requirement and filtering those ideas through the lists of product and project

constraints, two ideas were decided upon. The two ideas chosen were a gap

belt and a color sorter.

The first idea chosen was to attempt to sort the sticks that were longer

than pods by using a gap-belt concept. The reasoning behind the gap-belt

was that any material that was longer than the gap would travel to the other

side while material that was the size of a pod or shorter would fall through the

gap, assuming that the material could be oriented in a direction parallel to the

direction of travel of the belt. It was also possible to combine the gap-belt

with the spaced apart V-belts cleaning method because the V-belts also could

provide a method for aligning the material.

The second concept was electronic differentiation of the pods from the

sticks, based on color. This was chosen because there was an obvious

difference between the two at all times during the season. At the beginning of

the harvest season, the pods are bright red while the sticks are green.

Toward the end of the season, the sticks turn brown while the pods change to

a darker red. In addition, so many mechanical methods had been tried over

the years that it was felt that perhaps a more high-tech solution could be the

answer to the problem. Color sorting machines have been used by many

52

industries in sorting out product that is not the proper color, but have never

been used in the sorting of product from vegetation trash.

The funnel approach does not end once the concepts have passed

through the constraints. The next step is to develop these concepts into

prototypes. The development of prototypes for the gap-belt and color sorter

is described in the following section.

Step 7: Prototype Development

After the funnel process, the machine development involved design of

physical apparatuses that would be used for the gap-belt and color sorter.

This was accomplished through use of SolidWorks, solid modeling software.

The concepts were initiated, simulated and optimized using this software.

The level of detail involved in the design included clearance fits, bolt sizing

and production / assembly details. The reasoning behind the extensive

computer modeling of the machine was to minimize the fabrication and

assembly problems, therefore eliminating unnecessary labor and material

costs.

Gap-Belt Design

The first concept that was decided upon was a gap-belt concept to

attempt to remove sticks longer than pods. As stated earlier, the concept of

53

the gap belt is that sticks longer than pods would cross the gap and travel on

to the trash belt, while the pods would fall through the gap (Figure 34).

In order for the gap belt to work, it was decided that the incline belt

feeding the gap should be at the maximum possible angle. This would allow

the force of gravity to be overcome by the normal force exerted by the belt.

The sticks and pods would be held on the incline belt longer, increasing the

possibility of the sticks ending up on the trash belt.

The coefficient of static friction, s, between the belt material and the chile pods and sticks was calculated based on experimental data. This value

was then used to determine the theoretical maximum angle for the incline

belt. This calculated angle was between 28 and 39, depending on the material. When using something that is as varied as chile pods and sticks,

the calculation of the coefficient of friction becomes very difficult. The

coefficient, s, varies depending on the moisture content of the material and how much of the material is actually contacting the belt. This is a variant

because of the differences in shape from one pod to the next. The force

diagram (Figure 35) illustrates the three forces acting on a chile pod situated

on the incline belt. The same forces would act on a stick.

54

Figure 35: A force diagram illustrating the forces acting on material located on the incline belt

The gap belt was designed to allow for ease of testing and for ease of

manufacture. It was designed to allow for adjustment in the horizontal gap

distance from a value of no gap up to a 10-inch gap. This allowed for all

different sizes of pods to be accommodated. It also allowed the drop off point

from the incline belt to be five inches above or below the pickup for the trash

belt. The angle of the incline belt, the belt feeding the gap, also was designed

to be completely adjustable from 0 to 50. According to George Abernathy, an engineer at the USDA, ARS Southwestern Cotton Ginning Research

Laboratory, the maximum angle at which chile pods would stick to a belt

without sliding downhill was 30. The concept of the gap belt was dependant

55

on achieving the maximum possible angle of the incline belt. The gap belt

adjustment mechanism is shown in Figure 36.

Figure 36: Gap belt adjustment mechanism detail

The end of the trash belt that was at the gap interface received special

design considerations. Besides being designed to allow for all of the

adjustments to be made, it was necessary to ensure that all of the sticks that

came in contact with the belt would be pulled to the trash side. This was

accomplished by using the smallest size roller available. Using a small roller

also increased the number of possible alignments between the incline belt

and the trash belt. The limiting factor as to how small the roller could be was

the tightest radius that the food grade conveyor belting and the clips that held

that belting together could handle. The manufacturer of the belting

recommended a two-inch diameter minimum roller.

56

The gap belt requires all of the material to be oriented in the same way

in order for the concept to work. This orientation was achieved by having the

incline belt made up of multiple V-belts (Figure 37), with alternating V-belts

traveling at different speeds. According to Vince Hernandez, this method of

alignment has been shown to work in bell pepper processing plants. In order

to get the alternating belts to travel at different speeds, while having a uniform

interface at the gap, the shaft at the upper end of the incline had 27 idler

pulleys on it. The idler pulleys had bearings pressed into them to allow each

to spin independently. Two shafts at the bottom of the incline drove the belts.

The shafts were set several inches apart and had pulleys set-screwed for

every other belt. This caused half of the belts to be slightly longer in order to

reach the rear drive shaft and the other half to be slightly shorter in order to

reach the front drive shaft. The drive system of the gap belt was designed in

accordance with ASAE 211.5 standard for V-belt drives for agriculture

machines (American Society of Agricultural Engineers, 2001). A

horsepower, variable speed, 180 VDC motor powered each drive shaft.

57

Figure 37: The incline belt, variable speed V-belt aligning system

Strips of Ultra High Molecular Weight (UHMW) plastic were used on

the underside of the belts to maintain tension. These strips were crowned so

that the belts in the center of the conveyor system were 0.75 inches higher

than the belts at the outside of the system. Grooves for each belt were milled

in the UHMW plastic to keep the alignment of the V-Belts consistent over the

entire width.

58

Color Sorting

Color sorter operations were significantly more involved than the gap

belt concept. In order to devise the proper color sorting technique, more

experimentation and investigation were required. This investigation went

through three stages of development as listed below:

o Color sensing operations

o Color material removal concepts

o Off the shelf Color Sorters

The WECO Color Sorter

Color Sensing Concepts

Designing a system to use the difference in color between the pods

and sticks was a difficult problem. The primary dilemma occurred in

attempting to find a sensing method that could differentiate between the sticks

and pods. Multiple Internet searches were conducted and several sensor

manufacturers where contacted. Several companies were found that made

sensors that could distinguish color. The majority of the sensors were

photoelectric.

Sensors

One photoelectric color sensor, a R55 from Banner Engineering,

similar to that shown in Figure 38, was purchased for $290 and tested. It was

59

found that the sensor could distinguish between the pods and sticks;

however, it could only do so within a very limited range of about 5/8.

Through further research, it was found that laser color sensors were available

that had ranges up to 13 inches. One such sensor was the SA1M from Idec,

at a price of $1350. It is believed that this sensor could accomplish the job

but that it was too cost prohibitive. All of the concepts for removing the pods

or sticks once the color was determined relied on having an array of the color

sensors aimed at the belt and then having one removal device for each color

sensor. Conceptually, this could be a 36-inch wide belt with a color sensor

and removal device at every inch. That would come to a price of $48,600 for

the sensors alone, putting a production machine far out of the $50,000

acceptable price range.

Figure 38: The R55 color sensor from Banner Engineering

60

Machine Vision

At this point, it was found that LEGO Company manufactured and sold

a simple machine vision system for use on their RCX robots. The system

could operate a switch when a target color was sensed and the system could

distinguish between the color of a pod and a stick. The LEGO system was

very primitive, allowing only three targets and only having the ability to switch

one output on at a time. It was only used as a demonstration of the

possibilities and as a building block from which machine vision was

researched. The model shown in Figure 39 was built to show the Chile Task

Force the capabilities of the vision system and to demonstrate a possible

method for pod removal.

Figure 39: Lego machine vision concept model

Camera for Input

Pod Removal Arm

61

Machine vision was found to be a very complicated and involved

method of sensing. The basic premise behind it is that a camera is attached

to a processor, which analyzes the array of pixels to make some sort of

decision about what the camera sees. From that information, logical

decisions can be executed or measurements can be taken. Through

research, it was found that the majority of machine vision systems focus on

black and white camera inputs. They then determine shapes and sizes based

on the light and dark pixels. Very few color-sensing systems were found. Of

these, the majority could handle fewer than five targets for each setup. With

such a limitation, at least eight of those systems would be required to obtain a

minimum resolution of one-inch over the entire width of a 40-inch wide belt.

The only system that seemed to come close to providing what was

needed was the CV-700 from Keyence. The CV-700 allows for four

programs, each having eight target windows operating simultaneously, giving

the possibility of 32 target areas. The CV-700 costs approximately $7,000 for

a 1-camera setup or $9,000 for a 2-camera setup. A second camera may be

necessary to get adequate resolution over the whole width of a belt and would

feed its data into the same processor used by the first camera.

Sensing Methodology

It was decided that the color sensing method should sense the red

color of the pods, not the green or brown color of the sticks. This was

62

decided upon because the presumably larger cross section should provide an

easier target to sense and extract. A setup to remove sticks would require a

much higher resolution extraction method and also would sense the stems

that were the same color as the sticks, kicking out the stems also.

Unfortunately, stems are attached to pods, causing the pods to get extracted

to the same area as the sticks. Of course, this means that absolutely no

separation is taking place.

If, in a future setup, it becomes necessary to sense the green color of

sticks, it would have to become a two-step processing system. That is to say

that after the processor checked the color of the pixels, it also would have to

check the shape of that green color to determine if it was a stick or a stem.

This shape recognition is an algorithm that is common in the area of digital

machine vision, yet is out of the scope of this project. For this project, it was

only desired to sense a red color and then extract that red color because the

red is unquestionably a pod.

63

Color Sorter Removal Concepts

Once a system for identifying the color of material on a belt was

established, a method for removing the material, either sticks or pods was

required. Once again, the Funnel Approach to Design (FAD) was used to

brainstorm multiple ideas before deciding on one to pursue. Initial

brainstormed ideas included an indexing head with controlled vacuum holes

or a vacuum arm that could move down, pick up material and kick it onto

another belt.

The principle behind the indexing head pick up was as follows: A

sensor could identify all of the sticks and pods on a section of belt. A large

plate, perhaps 36 inches by 36 inches, could descend on the belt. That plate

would have vacuum holes every inch or half inch, controlled by individual

electronic valves. The controller could determine which of the valves to open

and close to pick up only the pods, based on the input from the color sensing

method. The head could then rotate out to the side of the belt where the pods

could then be deposited by releasing the vacuum.

Ideally, while that was occurring, another identical plate would be

removing material from the next section of belt. This concept was not

pursued because of the high cost of manufacturing such a setup. The large

number of valves would place the cost higher than the project constraint of

having a production model under $50,000. High reliability valves would cost

64

approximately $50 each. A one-inch resolution over a 36-inch by 36-inch

vacuum plate would require 1,296 valves. Each plate would cost $64,800 or

$129,600 for the above-mentioned two-plate setup. The setup also would not

pass the product constraint of maintaining a 48,000 lbs h-1 flow rate. It was

anticipated that the belt would need to stop to accomplish the task, therefore,

making it difficult to maintain the high flow rate.

The other concept explored for removing the material of a certain color

was an array of arms that would move vertically, down toward the belt to

vacuum up individual pods. The controller would actuate each arm when the

specified color was viewed. A four-bar mechanism attached to each arm

would operate a sweeper as the arm went down to pick up a pod. The

sweeper would cross the vacuum tip as the arm moved back up, kicking the

pod onto a belt moving perpendicularly to the main belt.

A very positive aspect of this proposed method was that it would not

require the material to be in a single layer. The color sensors would see

whatever was on the top layer and the arm would