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COMSOAL

COMSOAL. Computer Method for Sequencing Operations for Assembly Lines. Lindsay McClintock OPERMGT 345 – 004 May 6, 2003. Today’s Topics. Assembly Line Balancing By Hand Overview Example Exercise By Computer Using COMSOAL. Assembly Line Balancing.

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COMSOAL

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  1. COMSOAL Computer Method for Sequencing Operations for Assembly Lines Lindsay McClintock OPERMGT 345 – 004 May 6, 2003

  2. Today’s Topics • Assembly Line Balancing • By Hand • Overview • Example • Exercise • By Computer • Using COMSOAL

  3. Assembly Line Balancing • The process of equalizing the amount of work at each work station on an assembly line.

  4. How to Balance a Line • Specify the task relationships and their order of precedence. • Draw and label a precedence diagram. • Calculate the desired cycle time (Cd). • Calculate the theoretical minimum number of workstations (N). • Group elements into workstations recognizing cycle time & precedence. • Evaluate the efficiency of the line (E). • Repeat until desired line efficiency is reached.

  5. Order of Precedence Specify the task relationships and their order of precedence.

  6. The Precedence Diagram • Draw and label a precedence diagram. B 1 min A 2 min

  7. The Precedence Diagram • Draw and label a precedence diagram. B 1 min D 3 min E 1 min F 3 min A 2 min C 2 min

  8. Cycle Time • Calculate the desired cycle time (Cd). • If Joe’s Sub Shop has a demand of 100 sandwiches per day. • The day shift lasts 8 hours. Cd = 4.8 minutes

  9. Minimum Work Stations • Calculate the theoretical minimum number of workstations (N). • If Cd = 4.8 minutes j ti = completion time for taski j = number of tasks Cd = desired cycle time i =1

  10. Minimum Work Stations • Calculate the theoretical minimum number of workstations (N). • If Cd = 4.8 minutes j i =1 N = 2.5 workstations 3 workstations

  11. Order Work Stations • Group elements into workstations recognizing cycle time & precedence.

  12. Line Efficiency • Evaluate the efficiency of the line (E). • If Ca = 4 minutes and n = 4 work stations. j ti = completion time for taski j = number of tasks Ca = actual cycle time n= actual number of workstations i =1

  13. Line Efficiency • Evaluate the efficiency of the line (E). • If Ca = 4 minutes and n = 4 work stations. j i =1 E = 75.0% effective

  14. Trial and Error • Repeat until desired line efficiency is reached. E = 100.0% effective

  15. An Exercise A sample precedence chart

  16. An Exercise • Draw and label a precedence diagram. A 3 min B 5 min

  17. An Exercise • Draw and label a precedence diagram. A 3 min B 5 min D 4 min E 2 min C 2 min

  18. An Exercise • Calculate the desired cycle time (Cd). • If, there is a demand for 100 units to be produced every 12 hours. Cd = 7.2 minutes

  19. An Exercise • Calculate the theoretical minimum number of workstations (N). • If Cd = 7.2 minutes j ti = completion time for taski j = number of tasks Cd = desired cycle time i =1

  20. An Exercise • Calculate the theoretical minimum number of workstations (N). • If Cd = 7.2 minutes j i =1 N = 2.08 workstations 3 workstations

  21. An Exercise • Group elements into workstations recognizing cycle time & precedence.

  22. An Exercise • Evaluate the efficiency of the line (E). j ti = completion time for taski j = number of tasks Ca = actual cycle time n= actual number of workstations i =1

  23. An Exercise • The most efficient set up of the line E = 83.3% effective

  24. The Real World A real world precedence chart

  25. COMSOAL • Computer Method for Sequencing Operations for Assembly Lines • Developed by IBM • Fast and Easy

  26. How it Works • 5 Common Heuristics Used • Ranked positional weight • Longest operation time (LOT) • Shortest operation time (SHOT) • Most number of following tasks • Least number of following tasks

  27. How it Works • The COMSOAL program proceeds in 6 steps as follows: • STEP 1: For each task, identify those tasks which immediately follow it in precedence order. • STEP 2: Place in LIST A for each task in the assembly, the total number of tasks which immediately precede it in the precedence diagram. • STEP 3: From LIST A, create LIST B composed of the tasks which have zero predecessors. If no task remain unassigned to stations, then stop.

  28. How it Works (con’t) • STEP 4: From LIST B, create LIST C composed of the tasks whose performance times are no greater than the available time at the station. If LIST C is empty, open a new station with the full cycle time available and go through STEP 4 again. • STEP 5: Randomly select from LIST C a task for assignment to the station. • STEP 6: Update the time available at the station and LIST B to reflect the time consumed and the completed predecessors at this stage. If LIST B is empty update LIST A and return to STEP 3 otherwise return to STEP 4.

  29. Why COMSOAL? • Simplifies complex assembly line balancing problems • Faster, easier, and more accurate than calculating by hand • Saves time and money

  30. References • Russell, Roberta S. and Bernard W. Taylor III. Operations Management. 4th ed. New Jersey: Prentice Hall, 2003. • Graves, Robert, Dr. “Perspectives on Material Handling Practice.” http://www.mhia.org/bs/pdf/75021.pdf

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