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Even simple things like having two robot arms for the same task with one idle but ready in case the other fails; or being able to electronically label some asse

by crb002 8y ago

Even simple things like having two robot arms for the same task with one idle but ready in case the other fails; or being able to electronically label some assemblies as rejects and no-op everything on the down the line until they hit an eject point. Ability to re-insert them again later. On-off ramps with even 20 minutes of buffer capacity would be extremely helpful in building redundancy into the system.

Animats 8y ago
20 minutes of buffer in an auto plant? That's a building the size of a large supermarket. Buffering space is a big cost. Here's a Coca-Cola bottling plant.[1] This one has an extremely low employee count. It's mostly buffering space. That gives employees time to move to the trouble spot and deal with problems. Since Coca-Cola has been at this a while, they must need all that buffering. In an auto final assembly plant, you don't have the luxury of big buffers. On a rigid line, there's no buffering at all - if any station stops, the whole line must stop. That leads to quality problems - if someone drops a bolt, that bolt never gets inserted. A few seconds of buffering between stations helps. That's what Toyota's kanban system introduced. If you watch videos of Toyota production lines, they have a big timer showing the cycle time of the last cycle. It's not always the same. Sometimes a cycle takes a few seconds longer. If something goes wrong, like a tool breaking or a bad part, the stations upstream use up their buffering capacity and stop one after another. But the whole line doesn't have to stop for a one minute tool change. [1] https://www.youtube.com/watch?v=7V6JO0Rfgas https://www.youtube.com/watch?v=7V6JO0Rfgas
- csours 8y ago
  Disclaimer: I work for GM, any opinions are solely my own. This is enormously context-sensitive, but it is not at all odd to have a buffer with several hours worth of vehicles in auto assembly, for example between shops (ie between body and paint and between paint and final assembly). As you get closer to the end of the line, the buffers get much smaller, but you may have a 5 minute buffer between the last few lines in Final Assembly. One other thing to point out here; The two main styles of conveyance in vehicle assembly are fixed position stop and stop stations (also known by many other names). - Fixed position stop is what you call rigid line, and it is used where humans work on cars. The conveyor runs at a constant, slow speed through constant size work areas called footprints, such that each worker gets about a minute or so to do a set of assembly tasks. Humans can attach parts as the vehicle moves down the line. With fixed position stop, there is no buffer as the vehicle carriers are physically connected to a conveyor chain. - Stop stations are used where robots work on vehicles. It is very difficult to get a robot to work on a moving vehicle (but possible). Generally these conveyors move about twice as fast as the rigid stations, but all work is done while the vehicle is stopped. Also, each vehicle moves independently between stop stations as fast as the conveyor can move, and there is some buffering between each station. > 20 minutes of buffer in an auto plant? That's a building the size of a large supermarket. Yes, but it's in a mezzanine above the work area.

by crb002 8y ago

Animats 8y ago

20 minutes of buffer in an auto plant? That's a building the size of a large supermarket. Buffering space is a big cost. Here's a Coca-Cola bottling plant.[1] This one has an extremely low employee count. It's mostly buffering space. That gives employees time to move to the trouble spot and deal with problems. Since Coca-Cola has been at this a while, they must need all that buffering. In an auto final assembly plant, you don't have the luxury of big buffers. On a rigid line, there's no buffering at all - if any station stops, the whole line must stop. That leads to quality problems - if someone drops a bolt, that bolt never gets inserted. A few seconds of buffering between stations helps. That's what Toyota's kanban system introduced. If you watch videos of Toyota production lines, they have a big timer showing the cycle time of the last cycle. It's not always the same. Sometimes a cycle takes a few seconds longer. If something goes wrong, like a tool breaking or a bad part, the stations upstream use up their buffering capacity and stop one after another. But the whole line doesn't have to stop for a one minute tool change. [1] https://www.youtube.com/watch?v=7V6JO0Rfgas https://www.youtube.com/watch?v=7V6JO0Rfgas

csours 8y ago
Disclaimer: I work for GM, any opinions are solely my own. This is enormously context-sensitive, but it is not at all odd to have a buffer with several hours worth of vehicles in auto assembly, for example between shops (ie between body and paint and between paint and final assembly). As you get closer to the end of the line, the buffers get much smaller, but you may have a 5 minute buffer between the last few lines in Final Assembly. One other thing to point out here; The two main styles of conveyance in vehicle assembly are fixed position stop and stop stations (also known by many other names). - Fixed position stop is what you call rigid line, and it is used where humans work on cars. The conveyor runs at a constant, slow speed through constant size work areas called footprints, such that each worker gets about a minute or so to do a set of assembly tasks. Humans can attach parts as the vehicle moves down the line. With fixed position stop, there is no buffer as the vehicle carriers are physically connected to a conveyor chain. - Stop stations are used where robots work on vehicles. It is very difficult to get a robot to work on a moving vehicle (but possible). Generally these conveyors move about twice as fast as the rigid stations, but all work is done while the vehicle is stopped. Also, each vehicle moves independently between stop stations as fast as the conveyor can move, and there is some buffering between each station. > 20 minutes of buffer in an auto plant? That's a building the size of a large supermarket. Yes, but it's in a mezzanine above the work area.