Bob Hanover has a great little article about applying visual controls to household laundry on his “Thoughtput Solutions” site. (cute way to use TPS as the name for the company, too.)
The concept he outlines is the same one that is (or should be) used to trigger batch run points for kanban managed machines.
But I want to talk about machine utilization, especially of home appliances.
A modern home washing machine can cost anywhere from a few hundred dollars to over a thousand, depending on the make, model and features.
In a household like Bob’s, with two adults and seven kids, it makes sense to ensure this expensive machine is running to full capacity.
To keep the machine running, as each load is complete, the next one should be started, otherwise the machine will sit idle, and that would be bad… right?
Let’s do some math.
Typically a home washing machine completes its automatic cycle in just around half an hour.
Typically a home dryer completes its automatic cycle in around 45-50 minutes.
So, if you want avoid having the washer stand idle, what are you doing to do?
I’ll tell you what nobody does. Nobody keeps putting loads into the washer and piling up wet clothes to wait for the dryer. It is obvious that the dryer is pacing the process, and running loads through the washer faster than the dryer can take them would defy common sense. Wouldn’t it?
Yet we do this all of the time in factories.
Why?
I’ve been with a company making kitchen appliances for a couple of month now.
They do it because…
a) There’s 2 departments involved, the “washing” and the “drying” department, if you like
b) it gives a sense of accomplishment “look at all those batches with washed clothes we completed today! Successful day!”
🙂
What a great sense of accomplishment – but what was accomplished?
How would Mom and Dad react if they saw the kids had accomplished so much with the laundry, and had piles of heavy wet clothes stacked up on the floor?
🙂 All in good humor, but:
Of course the washer and dryer are close together, in a work cell you might say, so it obviously does not make sense to stack up wet clothes. You wait for the dryer. But put them in different rooms, then expect each to produce as much as possible, and what would you get?
So if they could not be so close together, how could we limit the overproduction of the washer?
We want to move closer to the ideal. Maybe a target condition would be load-by-load pull. Time for the kaizen team to get to work! 🙂
In Extreme Programming Expained, 2nd Edition, by Kent Beck, he goes through this example and suggests using a drying rack in addition to the dryer.
Also, I recently had to upgrade my washer, but not my dryer, and I now have access to enough settings that they run at similar speeds (cadence), although the dryer times are now approximate since it’s on sensor. (Running an extra long spin cycle at the end of the wash cycle, so that the clothes are more dry at the end of the wash cycle.) I haven’t done the math to see which is faster in practice.