Tuesday, June 19, 2012

Envelope Stuffing - One Piece Flow

To make up for not having a post last week, I've embedded two videos of envelope stuffing below. That's right! Mesmerize yourself with some exciting footage of people stuffing envelopes!

Actually, stuffing envelopes is a perfect lean activity for demonstrating one piece flow. It's simple and cheap. The process consists of multiple steps. And everyone's familiar with the method.

It wasn't too long ago that my wife was preparing for our wedding day. I also was roped into some of these preparations. The table was lined up with wedding invitations, ready to be signed, folded, stamped and mailed. This was in my dark pre-lean days and I assumed the fastest way would be to batch them.

Well, apparently that's not the case. Here follows video evidence that batching is slower than one piece flow.

The first video shows one man taking on the task. He times himself stuffing 10 envelopes, the traditional batch and queue method. After 10 envelopes, he repeats the task, one envelop at a time. The time shows that one piece flow is faster!

Some key things to note. During the batch process, tons of inventory build up. The envelopes by their nature don't stack very well when folded, showing some of the dangers of inventory (messy work place, bad 5S).

Now, what if my wife realized she wrote the wrong name on the wedding invitation? It would be a bit of task sorting through the stack of half opened envelopes to find the right one. The rest would be falling all over the place.

Here's the first video. The second one is below it. For those that can't see the embedded video, you can watch it on youtube here.

The other thing that needs to be remembered when watching these videos is the benefit of one piece flow to the downward processes. With one guy, one process, this benefit is essentially lost. So what if it's a little faster? Sure that's a benefit. But with multiple people doing the envelope stuffing in a row, you can demonstrate the real power of one piece flow. Less inventory through the process and faster cycle time for the first piece through the system.

This brings me to my second video. Here we have two teams competing against each other using two people each. This is the perfect opportunity to how one piece flow is more efficient. One person can be folding and stuffing, while the other is closing and stamping.

Unfortunately, the video disappoints. Both teams seem to be batching the process. I'm only showing the video as an example of how you could use this as a team activity, rather than a single person demonstration.

Here's video number two. You can watch the original on youtube here. 

To do this properly, I would use 4 people in a row. Each person does one step of the process, Person one folds, person two sticks it in the envelope, person 3 seals the envelope and the last person stamps it.

With this pseudo production line, you can control the WIP inbetween. Start with each person passing papers in batches of 5. Time how long it takes to go through the whole system. Nest, get each person to pass after completing one at a time. This way you can illustrate the benefits of reducing inventory between processes.

As demonstrated in both videos, stuffing envelopes can be easily used to illustrate lean processes. Whether as a one person demonstration or as a group activity, finding some envelopes and stuffing them is very cheap and requires basically no set-up.

For a more in-depth paper based lean activity check out the Making Pamphlets game, updated as "We're Having a Party". 

I've added this activity to my list of free lean games and training simulations. 

If after all this fun, stuffing envelopes is still too boring for you, consider stepping it up a notch with these awesome (and more complicated) mechanical paper card designs. 


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