1. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 1 Ch 17 Automated Assembly Systems Sections: 1.Fundamentals of Automated Assembly Systems 2.Quantitative Analysis of Assembly Systems

2. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 2 Automated Assembly - Defined “The use of mechanized and automated devices to perform the various assembly tasks in an assembly line or cell”  Fixed automation usually  Most automated assembly systems are designed to perform a fixed sequence of assembly steps on a specific product that is produced in very large quantities

3. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 3 Automated Assembly - Application Characteristics  Where is automated assembly appropriated:  High product demand  Stable product design  The assembly consists of no more than a limited number of components  The product is designed for automated assembly

4. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 4 Typical Products Alarm clocksLight bulbs Ball bearingsLocks Ball point pensMechanical pencils Cigarette lightersPCB assemblies Door mechanismsSmall electric motors Gear boxes Wrist watches

5. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 5 Assembly Processes in Automated Assembly Adhesive bondingSnap fitting Insertion of componentsSoldering Placement of componentsSpot welding RivetingStapling Screw fasteningStitching

6. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 6 Fundamentals of Automated Assembly Systems A typical automated assembly system consists of the following subsystems: 1.One or more workstations at which the assembly steps are accomplished 2.Parts feeding devices that deliver the individual components to the workstations 3.A work handling system for the assembled entity

7. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 7 Control Functions 1.Sequence control 2.Safety monitoring 3.Quality control

8. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 8 System Configurations 1.In-line assembly machine 2.Dial indexing machine 3.Carousel assembly system 4.Single-station assembly cell

9. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 9 In-Line Assembly Machine “A series of automatic workstations located along and in-line transfer system” Either synchronous or asynchronous work transfer used.

10. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 10 Dial Indexing Machine Base parts are loaded onto fixtures or nests attached to a circular dial table, and components are added at workstations located around the periphery of the dial as it indexes from station to station.

11. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 11 Dial indexing assembly machine (Bodine Corp.)

12. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 12 Carousel Assembly System “A hybrid between circular work flow of dial indexing machine and straight work flow of in-line system”

13. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 13 Single-Station Assembly Cell “Assembly operations are performed on a base part at a single location”  A robot is sometimes used as the assembly machine.

14. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 14 Multi-Station vs. Single-Station  Multi-station assembly machine or line  Faster cycle rate  High production quantities  More operations possible  More components per assembly  Single-station assembly cell  Suited to robotic assembly  Intended for lower production quantities

15. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 15 Parts Delivery at Workstations  Typical parts delivery system at a workstation consists of the following hardware components: 1.Hopper - container for parts 2.Parts feeder - removes parts from hopper 3.Selector and/or orientor - to assure part is in proper orientation for assembly at workhead 4.Feed track - moves parts to assembly workhead 5.Escapement and placement device - removes parts from feed track and places them at station

16. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 16 Parts Delivery System at Station

17. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 17 Vibratory Bowl Feeder  Most versatile of hopper feeders for small parts  Consists of bowl and helical track  Parts are poured into bowl  Helical track moves part from bottom of bowl to outlet  Vibration applied by electromagnetic base  Oscillation of bowl is constrained so that parts climb upward along helical track

18. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 18 Vibratory Bowl Feeder

19. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 19 Vibratory Bowl Feeder Photo courtesy Syntron Inc.

20. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 20 Selector and/or Orientor  Purpose - to establish the proper orientation of the components for the assembly workhead  Selector  Acts as a filter  Only parts in proper orientation are allowed to pass through to feed track  Orientor  Allows properly oriented parts to pass  Reorients parts that are not properly oriented

21. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 21 Parts Selection and Orientation (a) Selector (b) Orientor

22. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 22 Feed Track  Moves parts from hopper to assembly workhead  Categories: 1.Gravity - hopper and feeder are located at higher elevation than workhead 2.Powered - uses air or vibration to move parts toward workhead

23. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 23 Escapement and Placement Devices  Escapement device  Removes parts from feed track at time intervals that are consistent with the cycle time of the assembly workhead  Placement device  Physically places the parts in the correct location at the assembly workstation  Escapement and placement devices are sometimes the same device, sometimes different devices

24. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 24 Escapement and Placement Devices (a) Horizontal and (b) vertical devices for placement of parts onto dial-indexing table

25. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 25 Escapement and Placement Devices Escapement of rivet-shaped parts actuated by work carriers

26. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 26 Escapement and Placement Devices Two types of pick-and-place mechanisms for transferring base parts from feeders to work carriers

27. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 27

28. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 28 Quantitative Analysis of Assembly Systems 1.Parts delivery system at workstations 2.Multi-station assembly machines 3.Single-station assembly cells 4.Partial automation

29. 1. Parts Delivery System Let f: rate of removing parts from the hopper  : proportion of components that pass through the selector-orientor process and are correctly oriented for delivering into the feed track f  : effective rate of delivery of components from the hopper into the feed track 1-  :proportion recirculated back into the hopper Assume f  >R c to keep up with the assembly machine ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 29

30. Parts Delivery System High level sensor: a means of limiting the size of the queue in the feed track L f2 : active length of the feed track L c : the length of a component The number of parts that can be held in the feed track (the capacity of the feed track): n f2 = L f2 / L c ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 30

31. Parts Delivery System Low level sensor used to restart the feeding mechanism L f1 : location of the low level sensor L c : the length of a component The number of parts in the feed track at this point: n f1 = L f1 / L c ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 31

32. Parts Delivery System R c : the rate at which parts in the feed track are reduced when the high level sensor is actuated (turns off the feeder) f  - R c : the rate at which the quantity of parts will increase upon actuation of the low level sensor (which turns on the feeder) ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 32

33. 2. Multi-Station Assembly Machines Assumptions: 1.Assembly operations at the stations have constant element times, although they are not necessarily equal 2.Synchronous parts transfer is used 3.There is no internal storage 4.Defective parts can jam the station which results in the shutdown of the entire system ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 33

34. Multi-Station Assembly Machines Let q i : fraction defect rate, i.e. the probability that the component to be added during the current cycle is defective at station i m i : probability that a defect results in a jam at the station i and consequential stoppage of the line Three possible events that may occur at station i 1.The component is defective and causes a station jam with probability p i = m i q i 2.The component is defective but does not cause a station jam with probability (1-m i ) q i A bad part is joined to the existing subassembly 3.The component is not defective with probability 1- q i ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they cu q i rrently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 34

35. Multi-Station Assembly Machines For any station i, (m i q i ) + (1-m i ) q i + (1- q i ) = 1 If m i =m, q i =q, then (m q) + (1-m) q + (1- q) = 1 On an n-station assembly machine [(m i q i ) + (1-m i ) q i + (1- q i )] = 1 If m i =m, q i =q, then [(m q) + (1-m) q + (1- q)] n = 1 ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they cu q i rrently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 35

36. Measures of Performance The proportion of assemblies that contain one or more defective components m i q i indicates that a jam has occured, preventing a defective part (1- q i ) means that a good component has been added So, proportion of acceptable product coming off the line P ap = [(m i q i ) + (1- q i )] which is the yield of good assemblies produced by the assembly machine. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 36

37. Measures of Performance The proportion of assemblies that contain one or more defective components Then, the proportion of assemblies containing at least one defective component is P qp = 1 - P ap = 1 - [(m i q i ) + (1- q i )] If m i =m, q i =q, then P ap = (mq+1-q) n and P qp = 1 - (mq+1-q) n ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 37

38. Measures of Performance The frequency of downtime occurances per cycle, F F= p i = m i q i If no part is added at station i (performing only joining or fastening operation), then p i does not depend on m i and q i. If m i =m, q i =q, then F=nmq ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 38

39. Measures of Performance The average actual production time T p = T c + F T d = T c + m i q i T d If m i =m, q i =q, then T p = T c + nmqT d Actual production rate: R p = 1 / T p (rate of all assemblies made in the system) ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 39

40. Measures of Performance To find the yield rate or (production rate of good assemblies only) ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 40

41. Measures of Performance Line efficiency (includes all assemblies, good and bad) and the proportion downtime D=1-E We treat efficiency and quality of the line as separate issues. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 41

42. Measures of Performance C pc = cost per good assembly C m = cost of materials C o = cost of operating the assembly C t = cost of disposable tooling P ap = the yield (proportion of acceptable assemblies) ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 42

43. 3. Single Station Assembly Machines ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 43

44. 3. Single Station Assembly Machines Let n e = the number of distinct assembly elements that are performed on the machine T ej = element time, j = 1,..., n e T c = cycle time T h = handling time ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 44

45. 3. Single Station Assembly Machines Each component type has a certain fraction defect rate, q j, and there is a certain probability that a defective component will jam the workstation, m j. When a jam occurs, the machine stops, and it takes an average T d to clear the jam and restart the machine. The inclusion of downtime resulting from jams in the machine cycle time gives ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 45

46. 3. Single Station Assembly Machines If no part is added, then q j =0 and m j is irrelevant, so p j T d is included where p j is the probability of a station failure during element j. If m j =m, q j =q, then To determine yield (proportion of assemblies that contain no defective components), we use P ap. Uptime efficiency E=T c / T p ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 46

47. Example 17.4 ElementTimeqmp 140.021.0 230.010.6 340.0150.8 470.021.0 550NA0.012 ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 47 T h = 7 sec., T d =1.5 min. Determine a.Production rate of all product b.Yield of good product c.Production rate of good product d.Uptime efficiency of the assembly machine

48. 4. Partial Automation Reasons for using partially automated production lines: 1.Automation is introduced gradually on an existing manual line 2.Certain manual operations are too difficult or too costly to automate Assumptions 1.Workstations perform either processing or assembly operations 2.Processing or assembly times at automated stations are constant, though not necessarily equal at all stations 3.The system uses synchronous transfer of parts 4.The system has no internal buffer storage 5.Station breakdowns occur only at automated stations ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 48

49. 4. Partial Automation Let n a = the number of automated stations T d = average downtime per occurance p i = the probability (frequency) of breakdowns per cycle (for automated stations that perform processing), given Average actual production time: ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 49

50. 4. Partial Automation For automated stations that perform assembly: p i = m i q i If m i =m, q i =q, then and p=mq Let n w = the number of manual (worker operated) stations So, n= n a + n w ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 50

51. 4. Partial Automation C asi = cost to operate automatic workstation i C wi = cost to operate manual workstation i C at = cost to operate the automatic work transfer mechanism The total cost to operate the line: The total cost per unit produced on the line: ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 51

52. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 52 What the Equations Tell Us  The parts delivery system at each station must deliver components to the assembly operation at a net rate that is greater than or equal to the cycle rate of the assembly workhead  Otherwise, assembly system performance is limited by the parts delivery system rather than the assembly process technology  Component quality has an important effect on system performance - poor quality means  Jams at stations that stop the entire assembly system  Assembly of defective components in the product

53. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 53 What the Equations Tell Us  As the number of stations increases, uptime efficiency and production rate are adversely affected due to parts quality and station reliability effects  The cycle time of a multi-station assembly system is determined by its slowest station  By comparison with a multi-station assembly system, a single- station assembly cell with the same number of assembly tasks has a lower production rate but a higher uptime efficiency

54. ©2008 Pearson Education, Inc., Upper Saddle River, NJ. All rights reserved. This material is protected under all copyright laws as they currently exist. No portion of this material may be reproduced, in any form or by any means, without permission in writing from the publisher. For the exclusive use of adopters of the book Automation, Production Systems, and Computer-Integrated Manufacturing, Third Edition, by Mikell P. Groover. 54 What the Equations Tell Us  Multi-station assembly systems are appropriate for high production applications and long production runs  By comparison, single-station assembly cells have a longer cycle time and are more appropriate for mid-range quantities  Storage buffers should be used on partially automated production lines to isolate the manual stations from breakdowns at the automated stations  An automated station should be substituted for a manual station only if it has the effect of reducing cycle time sufficiently to offset negative effects of lower reliability