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KAIZEN CHALLENGE: Lean Technical and Social Quiz

by Jeff Smith
June 26, 2019

KAIZEN CHALLENGE: Lean Technical and Social Quiz

by Jeff Smith
June 26, 2019 | Comments (5)

Jeff (assembly) and Josh (machining) run a machine and assembly operation, which sells small engines. They bring in all the raw supplies. The first process machines one critical component used at the start of assembly. This critical component has three varieties. There is a machine dedicated to transform each variety so it is ready for assembly work.

The demand for variety A is 900 per day. Demand for variety B is 600 per day. Demand for variety C is 300 per day. A shift is 480 minutes of work time for machine and assembly. The layout has these three separate machine next to each other in a room that is 100 yards from assembly, with a WIP Pile 30 yards from assembly; and assembly 20 yards from shipping.

The three machines and their cycle times are as follows:

*Machine A= 25 seconds part (5 seconds human (load & unload) and 20 auto time).

*Machine B= 45 seconds part (10 seconds human (5 prep part + 5 load/unload) and 35 auto time).

*Machine C= 90 sec part (10 seconds human (5 prep part, 5 load/unload) and 80 seconds auto time).

One person is assigned to a machine for 1-2 shifts daily.

Machined parts comprise a WIP Pile of 1-2 days before assembly.

Assembly produces in a daily lot size of A, then B, and then C through one shift, plus overtime. It takes 8 minutes to assemble a completed small engine in any one of the three varieties. Assembly uses 38 people and runs at 13 seconds an engine. Output is 98%.

Jeff and Josh report to Karen. Karen has challenged them to free up cash flow and space by rethinking how they schedule Assembly and Machining. Now there is a one day lot size scheduled into each area with two days between them. Karen can see the way forward because of past experience. She does not dare just tell them what to do because they will miss a critical learning opportunity.

Karen’s plant has seven of these types of lines and machine equipment, but she selected the one run by Jeff and Josh since they need a little encouragement now and again.

Karen’s Challenge:

  1. What lot size is optimal to run through assembly to achieve our goal of 1800 day to open up floor space and free up cash flow?
  2. How much of each of the three machine varieties do we hold between machine and assembly?
  3. Do we have the best layout in place now? If not why and what should we do?
  4. After considering what needs to change, how do we communicate making that change so our team members make it their own idea and implement it?

There may not be a perfect answer, but if you were in the same situation and given that challenge how would you answer Karen?

In addition to Karen’s questions, can you identify any important lean concepts that Josh and Jeff need to brush up on?

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5 Comments | Post a Comment
Mike Owens June 26, 2019

A very interesting challenge!  I feel that the data is incomplete to make a recommendation.

I think the first place to start is to go to gemba in Assembly and deeply understand the situation there.  Then work backwards to Machining to achieve flow throughout the value stream.


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Andrew Bishop June 30, 2019
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Well, since none of the engineers in the audience are weighing in, this former plant pathologist will have a go.  Mrs. Olsen taught us in 4th grade to show our work, but since you didn’t ask, I’ll just answer Karen’s questions directly:

  1. Optimal lot size for assembly = 1 
  2. WIP held between machining and assembly = 1 for each type of engine
  3. No, we don’t have the best layout.  Why? All the distance between activities requires wasteful transportation, encouraging larger batches and piling up of WIP.  What to do? Put machining next to assembly, assembly next to shipping.
  4. These changes won't just happen.  The rear echelon you-know-what who just came up with them in a spreadsheet at his desk is probably wrong!  So, engage the team in discovering how best to approach these goals and the team will own them.  Provide a little training/simulation to develop their understanding of takt time, one-piece-flow, the 7 wastes, etc., followed by examining the work of the plant through the lens of these concepts, under the guidance of a teacher.  Then start testing ideas. The practicalities of testing and balancing the lines, of designing and setting up the mechanics of pull from machining to assembly can involve everyone. Did I mention, under the guidance of a teacher?

Then, given the size of the rest of the enterprise, new experts from these efforts can go forth to lead similar transformations in other parts of the business.  Josh and Jeff’s line won’t be needing quite as many people, though it will be ready to grow!

Important lean concepts on which Josh and Jeff need to brush up?

  • Takt time
  • One-piece flow
  • Batch size reduction
  • Pull
  • The 7 wastes (and some reliable countermeasures)
  • Man time/machine time
  • Kaizen

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Jim June 30, 2019

Andrew and Mike thank you for your thoughtful response.

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David July 03, 2019

Analysis of the machine auto timing vs Man wait time... Can we assemble during machine wait time with the machine operator for each part as it is produced? Moving or reconfiguring the machining cells to incorporate assembly through this process? Test ideas... Rethink... Test again utilizing operators ideas... Bring together the (cross-functional) team through the entire event building buy-in, eliminating many of our "wastes".

This is a simple explanation, and certainly should be explored further.


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James July 03, 2019

thanks David for your comment.  There is that possibility.  It seems josh and Jeff are keeping assembly separate from machining believing it necessary to hold wip between the operations. Are they correct? How can we prove or invalidate that assumption/ belief? How fast should assembly make one piece? What relationship does that have with each machine making a unique type of part at a certain rate?

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