By Andrew Wagner:
My wife, the resident space geek, turned me in the direction of this Boeing Press Release on their new lean “pulse line” for building GPS satellites, and presumably other satellites.
Most of the post is your standard lean accomplishments:
“…reducing the travel distance of a space vehicle from 12,000 feet to 10,000 feet…The line is intended to eliminate rework, allowing parts to flow continuously and smoothly through the process….New work cells, new tooling, standard work-planning packages and Lean manufacturing processes will reduce the total build time per satellite and increase the number of vehicles moving through the line at one time.”
Wait a minute… Increase the number of vehicles on the line? Do I need to go back and read that again? Increase inventory? That sure doesn't sound lean to me.
There are some ways to justify the increase in WIP. Perhaps they've freed up floor space and increased capacity so that they can meet increased customer demand. Mark reminded me that Factory Physics
Most companies beginning lean journeys start from a mass production baseline, but satellite production? Satellite production is the epitome of custom craft production. We've started to see constellations in recent years with GPS and telecom, but fundamentally the mindset is probably still building one-off pieces or small lots–not small lot sizes, small lots and then you're done for good, on to the next product.
The lean pulse line might actually be the first time they've looked at how to produce this particular product in a repeatable, systematic way. Of course, it's also possible that their PR folks do not understand lean well enough to describe their accomplishments. At worst, it's another sad example of “LAME” instead of lean.
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any time you increase production rate you get an increase in WIP (ie if I built 2 per month last month and 3 per month my ‘WIP’ increased). You can’t look at one factory measure without looking at the the big picture too.
Even if your TAKT time increases to three and you have single piece flow?
“Of course, it’s also possible that their PR folks do not understand lean well enough to describe their accomplishments. At worst, it’s another sad example of “LAME” instead of lean.”
Let me offer a third explanation.
It is possible that you either don’t understand lean well enough to understand the article, or you don’t understand why Boeing wants to “increase the number of vehicles moving through the line at one time.”
Granted, that I believe the latter is probably true. I will also grant that the PR did not explain itself well enough. The fact is that Boeing is probably trying to reduce their footprint while increasing throughput, and they probably have an incentive from the Customer to deliver the units more quickly than before. Let me explain this by describing what they did in their other production lines.
In the past, Boeing used to squeeze as many apaches or airplanes (insert product here) into a building as they could. They even put them at a 45 degree angle so you could squeeze more in (i.e. because of the wings you can fit more in a building this way). After beginning their lean journey, they began to straighten out the line, first implementing a pulse line and then moving the lines. This in turn allowed them to increase the line’s throughput and capacity. You see, before your capacity was limited to space. Now your capacity is limited by the speed of your line (yes I know balanced to takt time and all that). Additionally, your WIP costs decrease because you have less product on hand at any time. Note, of course, that your WIP costs could increase as well because your throughput could, but if it meets demand then it is still “lean.”
Without to much explanation it is probably safe to assume that they will be not only increasing throughput but will also reduce WIP.
I’ve learned (often the hard way) about making too many conclusions based on an article or press release. It’s no substitute for a gemba visit.
I thought Andy’s post *did* bring up a valid discussion point about WIP and “Factory Physics.”
If WIP is too low, you’re “starving” the line and throughput would be lower than ideal (assuming you’re needing to maximize throughput to meet customer demand). If WIP is zero, throughput is ZERO.
But, increasing WIP has diminishing returns. At some point, adding more WIP (beyond “critical WIP” as it’s called in Factory Physics), you get minimal or no increase in throughput.
So Andy’s assessment (or the answer to his question) depends on the starting point of how much WIP was in the system.
I haven’t seen too many systems there WIP was too low (people normally try to jam more WIP in than needed), but it is possible.
Mark,
Good discussion. Actually, more and more we are seeing lines that have too little WIP and end up with less than possible throughput or poor customer service or both. It’s a matter of knowing what the design characteristics of your production line are and the expected performance based on the characteristics (WIP, throughput, variability, lot sizing) you have designed into your line. I too question why such a custom environment such as satellite production is set up as a production line. TPS is just one logisitics design and it doesn’t work well for all situations. Unless these are program satellites, e.g. Iridium, I would think that by definition each one is a one piece job. I’ve seen Boeings presentation of their moving assembly line for the 777 and $250 million to take 2 days off of a 50 day cycle time is not impressive. It’s hard to make a definitive assessment without seeing the actual situation but there are indeed many production lines installed based on folklore and arithmatic rather than having a comprehensive, scientific approach to operations logistics design.