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Auto Components Ltd. Case Study

Auto Components Ltd. Case Study


  1. Introduction


Auto Components Ltd. is a medium sized company with five production facilities throughout the U.K. Each plant produces a variety of components for various truck and car manufacturers. Each plant has a certain amount of autonomy and has grown to supply the needs of manufacturers in its vicinity.


A facility located in north Devon has traditionally concentrated on producing small, relatively simple components. Over recent years, much of this work has been put up for competition with Auto Components Ltd. frequently losing business to specialized, more modern suppliers.


One of the few areas where the north Devon facility is still competitive is the production of valves. A variety of such devices are built for a range of applications.


The ZA valve lines produce valves coated with titanium nitride. The coating makes the valves resistant to damage by water, grit or mud. It is also makes the valves expensive. They are therefore only used on luxury sport utility vehicles.


The ZA810 line produces valves of both 20 and 25 cm. Other than the length, these valves are identical in every respect.



  1. The Project


You have been employed by the management of the north Devon facility to produce a comprehensive simulation study of the ZA810 production line.


You are required to produce a professional report for the company detailing the results of your study and the improvement recommendations that you would make to the system. Include any statistical analysis that you perform to support your recommendations. You should make at least 3 improvement suggestions, supported by arguments and data.


The simulation model will be created in the software package Witness. The model must be graphically well presented. Any data that you think will aid in the understanding and verification of the model should be shown dynamically as part of the model display.


It is envisaged that the management will continue to utilise the model after the end of the simulation study, so it is necessary for you to provide documentation explaining the layout and logic of the model.









  1. Assessment


You will be required to submit individually 2 files:



  • The simulation models. The simulation file’s name must include your name (e.g. mod)


  • The Project Report. The report will be submitted. Your report should have a maximum of 1200 words. Tables and graphs are not included in the word count. Your report must include a short executive summary giving a brief description of what was carried out and your findings. The executive summary1 should be no more than 150 words.



Assessment of the project is based upon the Project Report using the following criteria:


a.Documentation of model logic30%
b.Analysis of the results20%
c.Conclusive argument development30%
d.Report presentation including conciseness20%


I will use the simulation file to check the consistency between your report and the simulation.



The Project Report will be checked against plagiarism.



Please note that the majority of the marks are NOT given for the simulation itself, but for the quality of your analysis and improvement suggestions. In the past some students have submitted a near perfect model and a terrible report. Taking this approach will not get you the best mark.


Please also note that there is no ‘perfect simulation’ of a real system. In order to get as close as possible to the details of this manufacturing systems, you will have to make some assumptions. Please state clearly these assumptions!













  • An executive summary, or management summary, is a short document or section of a document, produced for business purposes, that summarizes a longer report or proposal or a group of related reports in such a way that readers can rapidly become acquainted with a large body of material without having to read it all. It usually contains a brief statement of the problem or proposal covered in the major document(s), background information, concise analysis and main conclusions. It is intended as an aid to decision-making by managers and is the most important part of a business plan






Description of the ZA810 Valve Production Line


(Refer to attached Data Sheet and Process Diagram)


Raw material (bar stock) for both valve types is delivered to buffer STORE1. They are delivered via a forklift from the parts crib with a particular delivery schedule. Auto Components Ltd. have a contractual agreement with the supplier of bar stock that guarantees the part crib will never run empty.


SAW takes a single bar from STORE1, processes it, and places it in STORE2. DRILL takes a single bar out of STORE2, processes it, and places it in STORE3. Finally COATER takes a single bar from STORE3, processes it and dispatches it to the ROLLER conveyor.


Both DRILL and SAW each have 2 separate tools that are used for each operation. Data has been provided on the replacement frequency of these tools. In addition the breakdown profiles of SAW, DRILL and COATER have been collected.


The production line employs three machinists, LAB1, LAB2 and LAB3. LAB1 and Lab2 are responsible for SAW, DRILL and INSPECT. LAB3 is responsible for COATER.


A series of ten manual workstations, five of them produce 20 cm valves and the other produce 25 cm valves, are simulated as two fixed conveyors, STAT_20 and STAT_25 respectively. Both conveyors need to have a carrier or pallet to position the bars as they move from station to station. To accomplish this, the LOAD operation takes a pallet from PALLET STORE and places a bar from ROLLER in it. Fifty percent of the pallets go to STAT_20 and the other fifty percent go to STAT_25.


The UNLOADING operation disassembles the pallets from STAT_20 and STAT_25. It sends pallets down the RETRIEVAL CONVEYOR, which deposits the pallets back into PALLET STORE.


The valves are then placed in to the INSPECT operation. The INSPECT process consists of four distinct cycles.


Quality has been a big issue in the past with only 85% of the valves passing inspection. Those that do pass are shipped. Rejected valves are placed into the REWORK buffer for repairs. The repair time, which depends on what valve needs to be repaired, is simulated as a minimum delay within the buffer. Any repaired valves will be inspected again to ensure their quality.


The management require displaying separately the total numbers of 20 cm and 25 cm valves that have been reworked. In addition, calculation and display of the average downtime of the COATER, DRILL and SAW machines is also required.


The facility works three shifts a day, 7 days per week. The shift applies to part arrivals and labour.


The management have completed a primary study of the system and have suggested a warm-up time of 600 minutes; this may be checked for accuracy. They are interested in a production time of at least 1 week in addition to the warm-up period.








A1. Data Sheet


Bar Stock delivery schedule: 50 bars every 240 minutes


Buffer capacities:

STORE1: 1000 parts

STORE2, STORE3: 10 parts


  Table A1-1. Machine Cycles          
  Machine Cycle Time [min]    Operation Labour  
   SAW Mode = 3.7, Min = 2.9, Max = 4.3 LAB1 or LAB2  
  DRILL 5.2   LAB2 or LAB1  
  COATER 2      LAB3  
  LOAD 4       
  UNLOADING 4       
    Table A1-2. INSPECTION Cycles        
    Description  Cycle Time [min] Labour Requirement   
     Position Valve   1 LAB1 or LAB2   
    1st Automatic Test   3      
     Calibrate   1 LAB2 or LAB1   
    2nd Automatic Test   2      
 Table A1-3. Tool Replacement Data          
 Machine Tool Ops. BetweenChange Times [min]  Labour Requirement
       Tool Changes            
  SAW 1  50    1.5     LAB1
  SAW 2  75    2.1     
 DRILL 1  45    1.2     LAB2
 DRILL 2  35    2.8     
  Table A1-4. Machine Breakdown Information        
  Machine Breakdown Repair Duration Labour Requirement 
   SAW Mean = 60 min Mean = 20 min  LAB1 and LAB2 
        Busy K = 3   (Two labours are 
        (Neg. Exp.) (Erlang)   required) 
  DRILL Every 100 See Table A1-5  LAB1 and LAB2 
        Operations      (Two labours are 
  COATER Mean = 120 min Mean = 20 min   LAB3 
        Busy K = 3        
        (Neg. Exp.) (Erlang)       








  Table A1-5. DRILL Repair Times   
  Range [min] Frequency     
   0 – 10  12     
  10 – 20  8     
  20 – 30  18     
  30 – 40  4     
  40 – 50  10     
  50 – 60  16     
 Table A-6. Conveyor Information     
 ROLLER       Data 
 Bar Length        30 cm 
 Length of ROLLER     2.4 m 
 Speed of ROLLER     3 m/min 
 Pallet Length        60 cm 
 Length of STAT_20     3 m 
 Length of STAT_25     3 m 
 Speed of STAT_20 and STAT_25   3 m/min 
 Length of RETRIEVAL CONVEYOR   6 m 
 Speed of RETRIEVAL CONVEYOR   3 m/min 
 Number of Pallets   10 
 Capacity of PALLET STORE  10 
Table A-7. Valve REWORK Information     
Item    Data     
 20 cm Valve REWORK Time  16 
 25 cm Valve REWORK Time  20 
 REWORK Capacity 10 Valves
Table A-8. Shift Patterns       
Shift Period Shift 1 Shift 2  Shift 3
 Start 12:00 AM 8:00 AM   4:00 PM
Lunch (1 hour) 4:00 AM 11:00 AM   8:30 PM
 Finish 8:00 AM 4:00 PM   12:00 AM


















































Last Updated on March 11, 2019

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