# Lean (pull) Question

Six Sigma – iSixSigma Forums Old Forums General Lean (pull) Question

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• #47443

walden
Participant

I have a process that involves 3 seperate work cells. The first cell has an avg. cycle time of 2 hours and so does the third cell. My problem is that the second cell has a test procedure that takes about 6 hours.
I want to set up in/out locations for product in each cell and then shift resources to constraint areas when in/out locations are full. My eventual goal is to put out 20 units per day. How do I determine the size of my in/out boxes for the second and third cells?
Thanks

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#158155

Mikel
Member

Go fix the test procedure so that the cells will flow.

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#158157

Jamilah Haron
Participant

Your bottleneck is at Cell 2. Cell 2 needs 5 test stations to achieve 20 unit a day.
20/(24/6)=5. So the incoming units to be prepared to Cell 2 is 5, which means 1 for each test station. And incoming for Cell 3 is the output units of cell 2, which is 5.

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#158180

somo
Member

Your description of the process isn’t very clear.  The second process has the longest process time, but it may not be a constraint.  It is only a constraint if there is a capacity constraint.  One way to look at this is if you have are spray painting cars. The painting time is two hours and the dry/cure time is six hours. The painting bay consists of one paint system and 10 spots for drying cars.  It may appear that the longest process time (of six hours) is the constraint, but really the paint system is the capacity constraint.  In this case, the drying ‘process’ is really a ‘wait queue’ — and it is not a constraint as long as there is sufficient space for waiting.
So the first question, is the test procedure a ‘wait queue’, or does it actually consume the ‘capacity’ of cell #2 for 6 hours?

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#158328

His Excellency
Participant

Identify your takt time first. Your plan of having in/out locations might not be the right solution, check your levelling, workload allocation, layout, one piece flow, among others

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#158362

Participant

I agree with Stan about addressing the test,. Can you evaluate the
test it’s self, can you reduce errors (increase capability) to a level
where you can cut out part of the test and minimize the rest can you
test sub assemblies off line out side of the test cell or have suppliers

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#158363

Ron Pereira
Member

Hi Chris,
I used your question as sort of a case study over on my blog.  I cannot give out the URL (against the forum rules) but if you click over to the iSixSigma Blogosphere page and look on the left hand side you will see a link to my blog: Lean Six Sigma Academy.  Thanks for the link Michael!
Please contact me if I totally butchered the assumptions to this problem.  I am not a consultant but would be happy to help you out as best I can.  You can find my email on the blog if you are interested.
Good luck!
Ron

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#158693

Matt I
Participant

Hi Chris,
If your goal is 20 units per day and you ASSUME a 480 minute workday -then your TAKT time is 24 minutes. Thus, set up your cells and your process to reflect cycle time, not the other way around. If you have “waiting” constraints such as curing or “burn-in” times, create standard-work-in-process placeholders such that the process flows. Conduct time observations of the process “as-is”, then reconstruct the cell. When first starting out, it may be more helpful to break the cell up where the cycle time is slightly longer than the TAKT time but where there is a logical break in the process. Then you can get started with process improvements and coupled with a quick trip up the learning curve, you can get each station to the appropriate time.
Not knowing any more about the nature of your test (whether there is burn-in time, what time is related to set-up or fixturing, logical breakpoints, etc.) there are many options for establishing it. Of course, one constraint may be duplicity of test eqt, but there are options for that constraint as well.

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