ensc 432-894 ppt part 5a - manufacturing systems

ENSC 432/894: Manufacturing Systems

Part #5: Manufacturing Systems Spring 2013, K. Oldknow

Part 5: Manufacturing Systems

Background Reading:Chapters 13‐15 (Groover)

Assigned Readings:Automated Production Lines (Ch. 16, Groover)Automated Assembly Systems (Ch. 17, Groover)Cellular Manufacturing (Ch. 18, Groover)Flexible Manufacturing Systems (Ch. 19, Groover)

1



Automated Production Lines

2



Automated Production Lines

• Characteristics:– Parts requiring multiple processing operations– Multiple, automated workstations– Workstations linked together by mechanized work transport system

• Conditions for suitability:– High demand– Stable product design– Long product life cycle (several years)– Multiple operations required

• Benefits when conditions are met:– Low direct labour– Low product cost (fixed equipment cost amortized over many units)– High production rate– Minimal work‐in‐progress (WIP) and lead time

3



In‐line configuration

• http://www.youtube.com/watch?v=j4‐F8EZZGAg

4



Segmented in‐line configuration

5

L‐shaped layout

U‐shaped layout

Rectangular configuration



Rotary configuration

6



Transfer System Examples

• Belt‐Driven

• Walking Beam

• Geneva Mechanism

• Other Cam Indexing Mechanisms

7



Storage Buffers

• http://www.youtube.com/watch?v=VoznYktHkXI

8



Application to Machining Systems: Transfer Lines

• http://www.youtube.com/watch?v=2ih2bzoSDo8

9



Analysis: Transfer Lines with no Storage Buffers

• Ideal Cycle Time(Tsi = processing time at station i, Tr = transfer time):

• Production Cycle Time(F = downtime frequency, Td = average downtime per line stop):

10



Analysis: Transfer Lines with Storage Buffer(s)

• Two‐stage System, Limi ng case: Infinite buffer capacity (b = ∞)

• Two‐stage System, Practical case: Finite buffer capacity (b>0)

11



Sample Problem

• 16.27 (Groover): The uptime efficiency of a 20 station automated production line is only 40%. The ideal cycle time is 48 sec, and the average downtime per line stop occurrence is 3.0 min. Assume the frequency of breakdowns for all stations is equal (pi = p for all stations) and that the downtime is constant.

To improve uptime efficiency, it is proposed to install a storage buffer with a 15‐part capacity for $14,000. The present production cost is $4.00 per unit, ignoring material and tooling costs. How many units would have to be produced in order for the $14,000 investment to pay for itself?

12



Automated Assembly Systems

13



Automated Assembly Lines

• Characteristics:– Entities (products) requiring assembly of multiple components– Multiple work stations (assembly stations)– Parts feeding subsystems for workstatinos– Workstations linked together by mechanized work transport system

• Conditions for suitability:– High demand– Stable product design– Limited number of individual components (max. ~12)– Product(s) designed for automated assembly

• Benefits when conditions are met (as with automated production lines):– Low direct labour– Low product cost (fixed equipment cost amortized over many units)– High production rate– Minimal work‐in‐progress (WIP) and lead time

14



In‐line assembly system configurations

15



Dial‐type assembly system configurations

16



Carousel assembly system configurations

17



Single‐station assembly system configurations

18



Analysis: Parts delivery subsystems

• Assuming that parts can be retrieved from the hopper (in random orientation) at a rate f, and that a proportion of parts, θ, pass successfully through selection/orientation for delivery to the feed track:

• Effective delivery rate:

19



Analysis: Multi‐station Assembly Systems

• Letting: q = defect rate for incoming partsm = probability that a defective part will cause a station jam

• We can develop the production cycle time as follows:

20



Sample Problem• 17.10 (Groover): An automated assembly machine has four workstations. The first station

presents the base part, and the other three stations add parts to the base. The ideal cycle time for the machine is 3 sec, and the average downtime when a jam results from a defective part is 1.5 min. The fraction defective rates (q) and probabilities that a defective part will jam the station (m) are given in the table below. Quantities of 100,000 for each of the bases, brackets, pins, and retainers are used to stock the assembly line for operation.

Determine: (a) proportion of good product to total product coming off the line(b) production rate of good product coming off the line(c) total number of final assemblies produced, given the starting component quantities. Of the total, how many are good product, and how many are products that contain at least one defective component? (d) Of the number of defective assemblies determined in above part (c), how many will have defective base parts? How many will have defective brackets? How many will have defective pins? How many will have defective retainers?

21

Station Part identification q m1 Base 0.01 1.02 Bracket 0.02 1.03 Pin 0.03 1.04 Retainer 0.04 0.5

ensc 432-894 ppt part 5a - manufacturing systems

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lowdirectlabour lowproductcost

highproductionrate minimalworkinprogress

automatedproductionlines

part 5

spring2013

conditionsforsuitability

twostagesystem

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