One Piece flow, the real story
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- เผยแพร่เมื่อ 11 ต.ค. 2023
- Have you also seen those animations about the huge benefit of one piece flow? It's supposedly way better than batch production, the only way to 'do Lean' and a waste if not implemented immediately.
But when you see those animations, where it takes ages for a batch production system to output even its first product while the one piece flow has already finished the whole order, don't you immediately know that it's nonsense?
Don't get me wrong, one piece flow is a good system, just not as overwhelmingly different as those animations make it seem.
A regular factory is full of work in progress (WIP), so the machines are not idling, they're producing all the time. So batch production will produce about the same as one piece flow.
There are advantages though: lower inventory, faster reaction to defects and client demands, less stuff on the floor, and more.
#continuousimprovement #lean #onepiece - วิทยาศาสตร์และเทคโนโลยี
Yes, the mic change is definitely a great improvement. Thanks for the video, Tom.
This is interesting. Ive recently upgraded our new cabinet shop with better machines. Im rethnking how we do our process out of necessity. I discovered this "one piece flow" and found those animations to be very interesting but something wasnt adding up. They never addressed the issue of it would require 5 people for 5 stations of OPF (one piece flow) say, but there would be alo 5 people for bathcing. So that stack of pieces would not just be piling up while the OPF units are being completed. I thought I was just misunderstanding something. So glad Ive stumbled across your video. We have only a very small shop, 2-4 workers. So it seems to me that a hybrid of batching and OPF makes sense, and that should be dictated by the resources and scop which go itnto any specific part of our system. Am I on the right path here?
The concept of One Piece Flow is still very valid - it's a good system, just not as overpoweringly good as many of those animations make it out to be.
I would say the main benefit is early detection of problems - if you pull one piece through your entire production process, you'll know if you have the right materials, design and work stations set up, before you commit a whole batch of materials to the first couple of operations.
The other benefit is flexibility in production - Work In Progress isn't worth anything (you've committed the materials, but haven't made the thing your customer will pay for), so it's best to finish a product once you start on its materials. With OPF, you'll get to each finished product as soon as possible.
You may find, however, that some operations are simply easier to do in small batches. Usually because the setup of a work station takes some time or if an operation can treat a batch of products in basically the same time as a single piece (example of the oven).
That's why many companies don't go for literal One Piece Flow, but rather use Small Batch Production. These batches probably should not be larger than the customer's order (unless you're making to stock), but they can definitely be smaller - pick a batch size that still allows for easy handling and transport and also doesn't take up too much time. If you're working on larger stuff (like a motor cycle, or even just an engine or pump) one piece is probably your best batch size, but if your products are small enough that several fit in a box (which won't require a forklift to move 😉) than go up to roughly what you can still move manually and up to what takes a matter of minutes to produce (up to about 30 min maximum for a small batch - shorter is often better for flow).
@@TomMentink Good feedback. We make custom kitchens and builtin furniture. I am a career carpenter but I am self taught regarding cabinetry. It started with just, "can you make a cabinet" (yes), to a small shop (3,000 SF) and 3 other employees besides myself. I created and continue to develop a system and process for building, tracking labor and materials, analyzing the process, bidding and estimating, and, most recently, upgrading to industrial machinery which none of know how to use yet, including a CNC. The point is, Im always researching and exploring new and better ways to do EVERYTHING, and a big part of that is using the internet. But it sometimes surprises me what other people have to say regarding literally everthing, but specifically concerning workflow efficiency, best practices for building, and in general how things should be done. My instincts tell me to find what works best for our specific situation. Learn what I can from other skilled and knowledgable people, but chew the meat, spit out the bones. One challenge of that however, is when you have a tendency to get stuck in analysis paralysis. It kinda comes with the territory of being a bit obsessive over the details. It can make for a good craftsman, but it also can get in the way of production. Regardless, I appreciate your video and feedback. Its quite helpful to hear and see people breakdown things to a level thats easily digestable.
The mic works good.
Tom, please make a video showing job shop vs one piece flow.
Question.
Lets say you get a batch of 400 components to make a laser. The laser is made up from 4 components such as, lens, lens housing, diode and wire, setup.
The process is this:
1. Glue lens into lens housing - 1 minute
2. Wait for glue to cure - 1 minute
3. Attach diode - 1 minute
4. Testing - 1 minute.
In a job shop where you have 1 operator, they would do this in ideal condition without defect, breakdowns:
1. Glue all lenses into housings- 799 minutes
2. Wait for glue to cure - 799 minutes
3. Attach diode - 799 minutes
4. Testing - 400 minutes
Total time - 2797 minutes.
One piece flow:
1600 minutes.
Is this correct?
Thanks for letting me know.
A video on job shops is a great idea, it’s on the list 😉
As to your example: I don’t understand why you’re counting 799 minutes for those batched job shop stations, station 1 and 3 will simply take 400 x 1 min. In fact, the drying will be done while you’re gluing, so the total process will only take you 3 x 400 = 1200 min.
Very strict one piece flow will cost you 1600 min, but that’s only if you actually wait for each single piece to dry. If you would do “2 piece flow”, you’d end up with 1200 min too.
You will, of course, have all the problems that come with inventory if you batch all 400 pieces. And your very first product won’t be done until minute 801 (which under normal working conditions is ‘some time tomorrow’), vs min 5 in 2 piece flow - so course corrections are also much easier in the one piece flow system.
@@TomMentink I am counting 799 minutes because it is done in batches. The first assembly would be available in one minute after drying , however if you do whole batch the first one needs to wait remaining 399 minutes until the last one is done. Isn't it? I may be wrong, i do not know :D i think i am wrong
I think I got my calculation wrong. Lets say you have 100 pcs of product to make. This may be simpler.
To make the product you have to go through 5 steps. Each step takes 1 minute to complete. There is only one person working on this product.
SO what I would like to understand is how much would it take to make whole batch of 100 if;
1. It is done in batches - Step 1 - operator makes 100 pcs then they move to Step 2 - makes 100 pcs - Step 3 - makes - 100 pcs, Step 4 and Step 5, so in total they spend 500 minutes to make the product.
2. When operator makes 1 piece through 5 steps, then 2 piece through 5 steps and so on up to 100 - it looks like it also take 500 minutes.
Does that mean we can only see benefits in terms of speed using on one piece flow if there is more than one person working on the product and if there is only one person working on it it would take the same time to complete?
@@gl4c.4 correct: one piece flow does NOT decrease total production times for the whole batch. If you have multiple machines/people who can work at the same time, 1 piece flow can finish this specific batch earlier than a batch system (but total system output is not per se higher).
The big advantage come from its effect on WIP inventory decrease and its accompanying increase in process feedback speed. There really is a very good case to make for one piece flow, but it’s not in the pure maths of finishing a product batch sooner. (which is my main grudge with those animations that show 80% of a factory not doing anything while waiting for the previous process to finish a full batch)
@@TomMentink I undestand it now. Batch of 500 if you had 5 people working on it would be finished in 104 minutes in perfect conditons if I am correct