3 ms·

"JIT just pushes the costs on to smaller suppliers who a large company can effectively bully in the same way big supermarkets bully framers." This is not how t

"JIT just pushes the costs on to smaller suppliers who a large company can effectively bully in the same way big supermarkets bully framers." This is not how the TPS works (At least not in theory. In practice, bullying may or may not happen - I don't know about any). The idea behind JIT is that you can react to changes in external circumstances faster. Also, the suppliers should also not have huge stockpiles of parts. Then they can, too, react fast to changes in demand. But this can also cause problems: http://sloanreview.mit.edu/article/the-toyota-group-and-the-aisin-fire/ http://sloanreview.mit.edu/article/the-toyota-group-and-the-...

lostboys67 9y ago
that's not how I recall JIT is the parts arrive just as needed on a mature production line continually making tweaks to parts is more akin to small batch production
sbierwagen 9y ago
Paywall link.
Animats 9y ago
If you have a stamping plant, you usually have far fewer presses than part numbers. You stamp out some part, then change dies to stamp out another part. Die changing and adjustment is time-consuming and is non-productive downtime. Once a press and die set is running well, it will produce parts at a good rate without much attention, but die changing is labor-intensive. The less often you change, the lower the cost per unit. The optimal batch size at the stamping plant may be quite different from the batch size the assembly plant wants. That means in-process inventory, stored somewhere. In the scale of auto body parts, dies weigh many tons and cranes are needed to do a die change. Clamping a die into position is complicated. There are quick-change systems. They're expensive.[1][2] What's probably choking Tesla is that they planned their stamping batch sizes for a much higher production rate than they can currently achieve. Much of the planning for the Model 3 production line was based on the assumption that not much would go wrong. They made hard tooling for parts before using prototype soft tooling to save time.[3] That's a win only if you get it right the first time. (I once worked in an R&D facility for heavy hydraulic equipment. They had to deal with problems like this. People talked about "setup" a lot. A basic fact of manufacturing is that setup and changes are much more difficult than production. Once you get a production machine set up, it's mostly putting in blanks and taking out product, and that's often automatic. Setup requires skilled people. There's been a lot of talk about "agile production" and a "lot size of one", but the real economies still appear only when you make large numbers of something. Look at the pricing for some on-line service that makes custom things for you. There will be a big price break as the quantity goes up.) [1] http://www.thefabricator.com/article/stamping/10-common-quick-die-change-problems http://www.thefabricator.com/article/stamping/10-common-quic... [2] http://www.thefabricator.com/article/stamping/how-quick-die-change-is-changing http://www.thefabricator.com/article/stamping/how-quick-die-... [3] https://insideevs.com/tesla-insider-speaks-out-on-problems-of-soft-tooling/ https://insideevs.com/tesla-insider-speaks-out-on-problems-o...
- dilemma 9y ago
  There are two ways of doing production: large batches, like you describe, and TPS. It is counterintuitive but TPS makes small batch production more efficient and more cost effective than large batches because it looks at the production system as a whole. You may want to read up on it - Check out The Machine That Changed the World.

lostboys67 9y ago

that's not how I recall JIT is the parts arrive just as needed on a mature production line continually making tweaks to parts is more akin to small batch production

sbierwagen 9y ago

Paywall link.

Animats 9y ago

If you have a stamping plant, you usually have far fewer presses than part numbers. You stamp out some part, then change dies to stamp out another part. Die changing and adjustment is time-consuming and is non-productive downtime. Once a press and die set is running well, it will produce parts at a good rate without much attention, but die changing is labor-intensive. The less often you change, the lower the cost per unit. The optimal batch size at the stamping plant may be quite different from the batch size the assembly plant wants. That means in-process inventory, stored somewhere. In the scale of auto body parts, dies weigh many tons and cranes are needed to do a die change. Clamping a die into position is complicated. There are quick-change systems. They're expensive.[1][2] What's probably choking Tesla is that they planned their stamping batch sizes for a much higher production rate than they can currently achieve. Much of the planning for the Model 3 production line was based on the assumption that not much would go wrong. They made hard tooling for parts before using prototype soft tooling to save time.[3] That's a win only if you get it right the first time. (I once worked in an R&D facility for heavy hydraulic equipment. They had to deal with problems like this. People talked about "setup" a lot. A basic fact of manufacturing is that setup and changes are much more difficult than production. Once you get a production machine set up, it's mostly putting in blanks and taking out product, and that's often automatic. Setup requires skilled people. There's been a lot of talk about "agile production" and a "lot size of one", but the real economies still appear only when you make large numbers of something. Look at the pricing for some on-line service that makes custom things for you. There will be a big price break as the quantity goes up.) [1] http://www.thefabricator.com/article/stamping/10-common-quick-die-change-problems http://www.thefabricator.com/article/stamping/10-common-quic... [2] http://www.thefabricator.com/article/stamping/how-quick-die-change-is-changing http://www.thefabricator.com/article/stamping/how-quick-die-... [3] https://insideevs.com/tesla-insider-speaks-out-on-problems-of-soft-tooling/ https://insideevs.com/tesla-insider-speaks-out-on-problems-o...

dilemma 9y ago
There are two ways of doing production: large batches, like you describe, and TPS. It is counterintuitive but TPS makes small batch production more efficient and more cost effective than large batches because it looks at the production system as a whole. You may want to read up on it - Check out The Machine That Changed the World.