2009

David Antuna

GSD

11/25/2009

HNC CAD/CAM SOFTWARE APPLICATIONS ASSINGMENT

“TURNING”

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Table of Contents:

Summary: ................................................................................................................................... 3

1. Introduction. ....................................................................................................................... 4

2. Feed rate. ............................................................................................................................ 5

3. Spindle speed. ..................................................................................................................... 6

4. Depth of Cut. ...................................................................................................................... 6

5. Cutting speed. ..................................................................................................................... 7

5.1 Work Piece Drawing. . ................................................................................................. 9

5.2 Calculation of Optimum Cutting Speeds. ..................................................................... 10

6. Calculation of Power Required for Machining Operations. ............................................. 12

7. Conclusion: ....................................................................................................................... 14

8. References: ....................................................................................................................... 15

9. Report Definitions: ........................................................................................................... 16

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Summary:

The intention of this report is to briefly, explain some of the machining operations that are

involved in the process of TURNING, these are: Cutting Speed, Depth of Cut, Feed Rate and

Spindle Speed.

Also demonstrated will be the mathematical calculations involved in the same process,

using various equations.

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1. Introduction:

The phrase speeds and feeds (or feeds and speeds) refers to two separate velocities in machine tool practice, cutting speed and feed rate. (Brown & Sharpe, Automatic Screw Machine

Hand book :) They are often considered as a pair because of their combined effect on the cutting process. Each, however, can also be considered and analyzed in its own. Cutting speed is the speed difference between the cutting tool and the surface of the work piece it is operating on, It is expressed in units of distance along the work piece surface per time. Feed rate is the velocity at which the cutter is fed, that is, advanced against the work piece. It is expressed in units of distance per revolution for turning and boring (typically inches per revolution (ipr) or millimetres per revolution). It can be expressed thus for milling also, but it is often expressed in units of distance per time for milling (typically inches per minute [ipm] or millimetres per minute). Cutting speed and feed rate together determine the material removal rate, which is the volume of work piece material (metal, wood, plastic, etc.) that can be removed per time unit.

If variables such as cutter geometry and the rigidity of the machine tool and its tooling setup could be ideally maximized (and reduced to negligible constants), then the amount of power (that is, kilowatts or horsepower) available to the spindle would determine the maximum speeds and feeds possible for any given work piece material and cutter material. Of course, in reality those other variables are dynamic and not negligible; but there is still a correlation between power available and feeds and speeds employed.

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2. Feed rate.

Feed rate is the velocity at which the cutter is fed, (Brown & Sharpe, Automatic Screw Machine Hand

book :) that is, advanced against the work piece. It is expressed in units of distance per revolution for turning and boring (typically inches per revolution [ipr] or millimeters per revolution). It can be expressed thus for milling also, but it is often expressed in units of distance per time for milling (typically inches per minute [ipm] or millimeters per minute), with considerations of how many teeth (or flutes) the cutter has then determining what that means for each tooth.

Feed rate is dependent on the:

Surface finish desired. Power available at the spindle (to prevent stalling of the cutter or work piece). Rigidity of the machine and tooling setup (ability to withstand vibration or chatter). Strength of the work piece (high feed rates will collapse thin wall tubing) Characteristics of the material being cut, chip flow depends on material type and

feed rate. The ideal chip shape is small and breaks free early, carrying heat away from the tool and work.

When deciding what feed rate to use for a certain cutting operation, the calculation is fairly straightforward for single-point cutting tools, because all of the cutting work is done at one point (done by "one tooth", as it were). With a milling machine or jointer, where multi-tipped/multi-fluted cutting tools are involved, then the desirable feed rate becomes dependent on the number of teeth on the cutter, as well as the desired amount of material per tooth to cut (expressed as chip load). The greater the number of cutting edges, the higher the feed rate permissible: for a cutting edge to work efficiently it must remove sufficient material to cut rather than rub; it also must do its fair share of work.

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3. Spindle Speed.

The spindle speed is the rotational frequency of the spindle of the machine, (Brown & Sharpe,

Automatic Screw Machine Hand book :) measured in revolutions per minute (RPM). The preferred speed is determined by working backward from the desired surface speed (sfm or m/min) and incorporating the diameter (of work piece or cutter).

The spindle may hold the:

Drill bit in a drill Milling cutter in a milling machine Router bit in a wood router Shaper cutter or knife in a wood shaper or spindle moulder Grinding wheel on a grinding machine. Or it may hold the chuck which then holds the work piece in a lathe. In these cases

the tool bit remains stationery although exceptions may be found such as in thread milling.

4. Depth of Cut:

The easiest cutting parameter to adjust is the depth of cut. (Fox Valle Technical College. Machine

Shop) Doubling the depth of cut in a turning operation will double the metal removal rate

without any increase in cutting temperature. The horsepower consumed will virtually

double, but there will be no reduction in tool life (specific wear per inch of cutting edge

length) assuming the cutting edge can withstand the added tangential cutting force.

However, it is not always possible to increase the depth of cut to gain additional

productivity, since there might not be any remaining material to remove.

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5. Cutting Speed:

Cutting speed may be defined as the rate (or speed) that the material moves past the cutting edge of the tool, (Brown & Sharpe, Cam & Tool Design: Surface Cutting Speeds Chart, p. 5)

irrespective of the machining operation used — the surface speed. A cutting speed for mild steel, of 100 ft/min (or approx 30 meters/min) is the same whether it is the speed of the (stationary) cutter passing over the (moving) work piece, such as in a turning operation, or the speed of the (stationary) work piece moving past a (rotating) cutter, such as in a milling operation. What will affect the value of this surface speed for mild steel, is the cutting conditions:

For a given material there will be an optimum cutting speed for a certain set of machining conditions, and from this speed the spindle speed (RPM) can be calculated. Factors affecting the calculation of cutting speed are:

The material being machined (steel, brass, tool steel, plastic, wood) (see table below) The material the cutter is made from (Carbon steel, High speed steel (HSS), carbide,

ceramics) The economical life of the cutter (the cost to regrind or purchase new, compared to

the quantity of parts produced).

Cutting speeds are calculated on the assumption that optimum cutting conditions exist, these include:

Metal removal rate (finishing cuts that remove a small amount of material may be run at increased speeds)

Full and constant flow of cutting fluid (adequate cooling and chip flushing) Rigidity of the machine and tooling setup (reduction in vibration or chatter) Continuity of cut (as compared to an interrupted cut, such as machining square

section material in a lathe) Condition of material (mill scale, hard spots due to white cast iron forming in

castings)

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The cutting Speed is given as a set of constants that are available from the material manufacturer or supplier, the most common materials are available in reference books, or charts but will always be subject to adjustment depending on the cutting conditions. The following table gives the cutting speeds for a selection of common materials under one set of conditions. The conditions are a tool life of 1 hour, dry cutting (no coolant) and at medium feeds so they may appear to be incorrect depending on circumstances. These cutting speeds may change if, for instance, adequate coolant is available or an improved grade of HSS is used (such as one that includes cobalt).

Cutting speeds for various materials (Based on a plain High Speed Steel cutter)

Material type meters per min feet per min

Steel (tough) 15 - 18 50 - 60

Mild steel 30-38 100-125

Cast iron (medium) 18-24 60-80

Bronzes 24-45 80-150

Brass (soft) 45-60 150-200

Aluminium 75-105 250-350

Table 1 Cutting Speeds Parameters.

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5.1 Work piece Drawing:

The following diagram shows an example of work piece that could be machine/turn in a lathe.

This drawing was made using the design software AUTO CAD.

Table 2 Process of Turning

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5.2 Calculation of Optimum Cutting Speeds:

The following are the results from the calculations made for the cuttings speeds displayed

below.

The calculations where made using the following equation:

RPM = 𝑭𝑬𝑬𝑫

𝑪𝑰𝑹𝑪𝑼𝑴𝑭𝑬𝑹𝑬𝑵𝑪𝑬 =

𝑭𝑬𝑬𝑫

𝝅𝑿𝑫𝑰𝑨𝑴𝑬𝑻𝑬𝑹

CALCULATION OF OPTIMUM CUTTING SPEEDS FOR HARDENED STEEL

DIAMETER OF SHAFT IN MM FEED RATE IN MM/Min. RPM

20 15000 238.7324146

40 15000 119.3662073

60 15000 79.57747155

CALCULATION OF OPTIMUM CUTTING SPEEDS FOR BRONZE

DIAMETER OF SHAFT IN MM FEED RATE IN MM/Min. RPM

20 24000 381.9718634

40 24000 190.9859317

60 24000 127.3239545

CALCULATION OF OPTIMUM CUTTING SPEEDS FOR BRASS

DIAMETER OF SHAFT IN MM FEED RATE IN MM/Min. RPM

20 45000 716.1972439

40 45000 358.098622

60 45000 238.7324146

CALCULATION OF OPTIMUM CUTTING SPEEDS FOR ALUMINIUM

DIAMETER OF SHAFT IN MM FEED RATE IN MM/Min. RPM

20 75000 1193.662073

40 75000 596.8310366

60 75000 397.8873577

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This scatter graph displays the optimum cutting speeds for the various metals shown in this

report.

Table 3 Cutting Speed Calculations.

0

200

400

600

800

1000

1200

1400

0 10 20 30 40 50 60 70

R

P

M

DIAMETER OF SHAFT IN MM

CUTTING SPEEDS

HARDENED STEEL

BRONZE

BRASS

ALUMINIUM

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6. Calculation of Power Required for Machining Operations.

The table below displays the results of the calculations of the power required to turn Ø100

mm bar at the various speeds.

The following equation was used:

Power (W) = 𝑭𝒐𝒓𝒄𝒆 𝑵 𝒙𝑹𝒂𝒅𝒊𝒖𝒔 𝒎 𝒙𝟐𝝅𝒙𝑺𝒑𝒆𝒆𝒅(𝒓𝒆𝒗 𝒑𝒆𝒓 𝒎𝒊𝒏)

𝟔𝟎

CALCULATION OF POWER REQUIRED FOR CUTTING OPERATIONS

DIM. OF SHAFT IN MM RADIUS OF SHAFT IN MM

SPEED IN REV/MIN CUTTING FORCE IN (N) POWER

100 0.05 40 350 73.30

100 0.05 80 350 146.61

100 0.05 160 350 293.22

100 0.05 320 350 586.43

Table 4 Power Required for Machining Operation

0.00

100.00

200.00

300.00

400.00

500.00

600.00

700.00

0 50 100 150 200 250 300 350

P

O

W

E

R

SPEED IN REV PER MIN.

POWER REQUIRED FOR MACHINING OPERATIONS

Power

steel

Bronze

Brass

Aluminium

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As we can see from the table above, the higher the revolution per minute the higher the

power is required to cut/machine an object, in this case a solid shaft of 100mm of diameter.

These actions also influences on the tool life, the reason is simple, as it is stated above, the

higher the revs/min the higher the power is required therefore the harder the tool has to

work.

In this report we have taken four kinds of metal, hardened steel, bronze, brass and

aluminium, so if bronze is taking as a example we can deduct that it will be harder to

machine, therefore it will need a low set of feed and speed and doing so it will required just

the correct amount of power to do the job.

A company that it’s main activity is machining parts, i.e. A nuts and bolts factory, will

depend in it’s ability to maximize the use of the cutting tools, therefore all the machinery

must work with the optimum set up (cutting speed, feed rate & depth of cut) to make the

most of every cutting tool.

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7. Conclusion:

In this report we have learned that in the process of cutting/machining in the context of

TURNING, there is a very fine balance between setting up the optimum cutting speed, feed

rate and depth of cut. This balance if is apply correctly it should create the maximum level of

working condition to obtain the best results from the job in hand.

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8. References:

World Wide Web

In-Text Example

Reference List Example

End Note

Document on WWW

The phrase speeds and feeds refers to two separate velocities in machine tool practice.

Brown & Sharpe,

Automatic Screw Machine

Handbook: Brown and

Sharpe Speeds and Feeds

Chart, p. 222 & 223

Electronic Source Wikipedia the free Encyclopedia. 26 Nov. 2009 (last revision)

http://en.wikipedia.org/wiki/Feed_rate

Document on WWW

Feed rate is the velocity at which the cutter is fed.

Brown & Sharpe, Automatic Screw Machine Handbook:

Electronic Source Wikipedia the free Encyclopedia. 26 Nov. 2009 (last revision)

http://en.wikipedia.org/wiki/Feed_rate

Document on WWW

The spindle speed is the rotational frequency of the spindle of the machine.

Brown & Sharpe, Automatic Screw Machine.

Electronic Source Wikipedia the free Encyclopedia. 26 Nov. 2009 (last revision) http://en.wikipedia.org/wiki/Spindle_speed

Document on WWW

The easiest cutting parameter to adjust is the depth of cut.

Fox Valle Technical College. Machine Shop web pages.

Electronic Source Put on Fox Valle Technical College in year 2000. http://its.fvtc.edu/machshop4/Carbcut/Cutspeeds.htm

Document on WWW

Cutting speed may be defined as the rate (or speed) that the material moves past the cutting edge of the tool.

Brown & Sharpe, Cam & Tool Design: Surface Cutting Speeds Chart, p. 5

Electronic Source Wikipedia the free Encyclopedia. 26 Nov. 2009 (last revision) http://en.wikipedia.org/wiki/Cutting_speed

Picture on the WWW

The term "facing" is used to describe removal of material from the flat end of a cylindrical part.

Copyright © 2009 eFunda, Inc.

Electronic Source Efunda TURNING

http://www.efunda.com/processes/machining/turn.cfm

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9. Report Definitions:

The following is a list of definitions of the structural points that composed this report.

Title Page: The Title page is the very first page of a report and can be composed form

only text with the information about the course to a very elaborate visual page with

colour and pictures about the subject in the report.

Summary: The summary is a shorten version of the subject that has been said or

written in a report or a discussion, containing only the main points.

Table of Contents: This is the page where the content of a report is listed, including

pictures, graphs, tables and external work, all it is shown with its page number.

Introduction: The introduction is the section at the beginning of a report that

summarizes what it is about, also gives the reader the basic facts or skills in a field.

Body/Discussions: This is the main part of a report, when the subject in the report is

presented with all its facts, all the research done and all the support work. i.e.

graphs, tables, photographs etc...

Conclusions: This is the part in a report where after looking in to all the discussions

within the report it brings it in to a formal closure.

References: The reference states to the reader in a list or table of all the information

use to help to complete the report from authors other that the creator of the report.

Appendices: This part in the document is where is set all the separate material that

are part of the report but it has not been made by the creator of the same.

Acknowledgments: In this section of the report the author thanks those who have

help in the making of the report.