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I have worked on designing small machinery, 3d printers and cnc routers, and on some axis, we use two motors in sync for movement. It is very reliable until it

by kuon 3y ago

I have worked on designing small machinery, 3d printers and cnc routers, and on some axis, we use two motors in sync for movement. It is very reliable until it is not, we had times were programming errors or driver failure would unsync the two motors, moving the axis into a triangle. It is very rare like once every 1000 hours, but it does happen. For our bigger machine, were this would cost a lot and could be dangerous, we decided to go old school with full mechanical coupling and bigger motor, we also added second endstops being the optical ones with direct wiring of the general machine switch. The mechanical coupling never failed. I know it is not really the same type of machine and design, but it still makes me wary that my steering wheel will turn suddenly because of any unforseen reason.

leowoo91 3y ago
Can't they wire between two motors as the supporting signal? Would that reduce the error significantly?
- kuon 3y ago
  It really depends on the motor (stepper, closed loop BLDC...). It can help in some configuration but with bigger motors, there is a lot of inductance and EMI and it is very hard to drive them from the same wires. You usually have one supply and one driver per motor. As least that was my understanding from my software job point of view.
syntaxing 3y ago
I’m genuinely surprised this is the case, sounds like either budget constraint or bad engineering. Been a MechE for about a decade and worked on a span of critical applications. Either an off the shelf fully package motor from Parker or Schneider electric or a custom setup with a motor, high precision quadrature with harmonic drive run for years. Of course you need some safety code like encoder checks (baked into the off the shelf ones) but the machines I worked on run for years and throughput in the thousands without anything failing. Also worked on industrial gantries. We’ve built delta packaging robots with sub second throughput and those motors never go out of sync after commissioning.
- kuon 3y ago
  I am not sure as I was a software engineer on those and it was a few years ago. I would like to say cost constraint but I do not really know. But the mechanical engineers seemed way more confident with the single motor.

by kuon 3y ago

leowoo91 3y ago

Can't they wire between two motors as the supporting signal? Would that reduce the error significantly?

kuon 3y ago
It really depends on the motor (stepper, closed loop BLDC...). It can help in some configuration but with bigger motors, there is a lot of inductance and EMI and it is very hard to drive them from the same wires. You usually have one supply and one driver per motor. As least that was my understanding from my software job point of view.

syntaxing 3y ago

I’m genuinely surprised this is the case, sounds like either budget constraint or bad engineering. Been a MechE for about a decade and worked on a span of critical applications. Either an off the shelf fully package motor from Parker or Schneider electric or a custom setup with a motor, high precision quadrature with harmonic drive run for years. Of course you need some safety code like encoder checks (baked into the off the shelf ones) but the machines I worked on run for years and throughput in the thousands without anything failing. Also worked on industrial gantries. We’ve built delta packaging robots with sub second throughput and those motors never go out of sync after commissioning.

kuon 3y ago
I am not sure as I was a software engineer on those and it was a few years ago. I would like to say cost constraint but I do not really know. But the mechanical engineers seemed way more confident with the single motor.