Tools

Nov 30 2018

Runners, Repeaters, and Strangers among Components

In assembly operations, we need a Plan For Every Part (PFEP). For each purchased component, we must specify suppliers, choose order and delivery patterns, organize all actions taken inside the plant to deliver it from the receiving dock to the assembly line.

Setting a plan for each one of the thousands of purchased items is a daunting task. It helps if you can group the items in a handful of categories. Policies by category may not be as fine-tuned as for individual items but they are an improvement over “one-size-fits-all.”

To make it easiest to do what you do the most frequently, a natural criterion for categorizing purchased components is frequency of use. Once you have sorted the purchased components by decreasing frequency of use, however, you need to set category boundaries that make sense for assembly.

Rather than using arbitrary cut-offs, we base thresholds on the proportion of the demand that can be built completely as a function of the frequency rank of components. A point on this plot means, for example, that 50% of the demand can be met using only the 100 most frequently used components.

We explain how we use this chart to categorize components as Runners, Repeaters, and Strangers. Then we show how we generate it from bills of materials and a product demand. We end with actual examples from several factories and recommendations on communicating these results.

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Jun 25 2014

5S: It’s not About What is Done but Who Does It

In yet another discussion of 5S in the TPS Principles and Practice discussion group on LinkedIn, Ryan Ripley asked about the real meaning of the 3rd S, “shine.”  As several contributors pointed out, the 3rd S in 5S is Seiso, which translates to Clean, not Shine. As discussed in an earlier post, translating the 5Ss by five English words that begin with S is a misguided effort that results in systematic mistranslations.

For the first 4Ss, an earlier, imperfect but more accurate translation that I heard in the UK was R.I.C.K., which stood for:

  1. Remove — take all the items that are not routinely needed out of the work space.”
  2. Identify — assign and label locations for all routinely needed items.
  3. Clean — clean the equipment and the floors.
  4. Keep clean — enforce the daily discipline of doing 1 through 3.

I would add Second-Nature for the 5th S, because it means practicing the first four until they are assimilated to the point that enforcement is no longer necessary. This makes the acronym R.I.C.K.S. The translation as Sort, Straighten, Shine, Standardize, and Sustain is not remotely accurate and should be abandoned rather than plumbed for intellectual depth.

What is essential about the 3rd S, “Cleaning” is not what the task is but who does it. A janitor will wipe the oil off the floor and that’s it, the job is done. If the operator does the cleaning, then the hand guides the eyes and draws attention to details like frayed cables, broken dials, or puddles that weren’t there before. It works as an early warning system, and a stepping stone towards autonomous maintenance.

A challenge in organizing for operators to do this is that it is not direct production work. Much of what we do in designing operator jobs is making sure that they are relieved of all tasks that do not directly move the product towards completion. That is why, for example, assemblers should not have to unpack parts but instead should have parts unpacked by others and presented to them within arm’s reach, oriented for ease of assembly.

In the same logic, you might imagine that it makes sense to have others pick up after the operators, putting each tool back where it belongs and cleaning the work space. I remember a production manager in a car plant responding to the idea of setting aside the last 5 minutes of each shift to 5S by saying “that would cost us three cars.”

In reality, of course, I never heard of production performance going down as a result of doing 5S, but it is not a priori obvious.

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