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To get maximum torque out of the 800 oz/in motors you will need a 70 volt power supply and 70 volt drives. What are your current power supplies and drives rated at?

So I guess the question is, what size PS do I really need? The all up weight on the gantry calcs to about 90 lbs being driven by a 20mm x 5mm pitch ball screw.

The steppers are 4-wire only so I'm not sure if they are considered wired in series or parallel?

The motor label says 24vdc but what does that really mean?

Jay
 
Jay,
Since you already have what you have, I suggest you go with it as is. As I said in my other post, torque is not the problem with your power supply. You WILL get the rated torque if you can provide the required amperage. The issue will be how fast you can move. Voltage relates to SPEED. I'll bet you can get things running with what you have. If you later determine that you want higher speeds then a different power supply would be in order. Many find that they don't need high rapid speeds, especially if it is a small machine.

Using the maximum the drives will allow will get you the maximum performance available, but you may not actually need it.

4-wire steppers don't have the choice of parallel or series. This only means there is one choice instead of two when you look up the specs.

The motor label saying 24 vdc is there because the manufacturer says that voltage with the max current will not overheat the motor. Running higher voltage means you need to keep an eye on motor heating. My CNC mill uses Compumotor drives at 170 volts. Marris (Mr. Gecko drives) wrote a "White Paper" that does a very good job of explaining how you can make sure your motors are treated nicely. I suggest you download a copy. It shouldn't be hard to find.
 
Jay,
Since you already have what you have, I suggest you go with it as is. As I said in my other post, torque is not the problem with your power supply. You WILL get the rated torque if you can provide the required amperage. The issue will be how fast you can move. Voltage relates to SPEED. I'll bet you can get things running with what you have. If you later determine that you want higher speeds then a different power supply would be in order. Many find that they don't need high rapid speeds, especially if it is a small machine.

Using the maximum the drives will allow will get you the maximum performance available, but you may not actually need it.

4-wire steppers don't have the choice of parallel or series. This only means there is one choice instead of two when you look up the specs.

The motor label saying 24 vdc is there because the manufacturer says that voltage with the max current will not overheat the motor. Running higher voltage means you need to keep an eye on motor heating. My CNC mill uses Compumotor drives at 170 volts. Marris (Mr. Gecko drives) wrote a "White Paper" that does a very good job of explaining how you can make sure your motors are treated nicely. I suggest you download a copy. It shouldn't be hard to find.

Thanks areoHAWK. I will give it a go with what I have as soon as I get new motor couplers.

Jay
 
I got the motors swapped out and they drive all the axis just fine.

The problem I have now is 2 of the 3 drives work fine but one does not.

It powers up but does not send step/dir commands to the motor. I have verified the motor works, the drive is wired correctly and all connections are good. The BOB is outputting correctly for each axis. I don't know what else to check? Any help would be appreciated.

Jay
 
Does a different motor work on the suspect drive? And the suspect motor works on a known good drive?
 
Does a different motor work on the suspect drive? And the suspect motor works on a known good drive?

The motor works on a different drive. Nothing works on the suspect drive. I also swapped the step/dir/com wires to a different output and nothing.

I found an FAQ that said to check the drive with a ohm meter from pin 1 (power neg) to pins 3, 4, 5, 6 (motor) and it checks okay suggesting the mosfets are okay.
 
At this point I would pull all of the wires off of the drive and re-wire it. If that fails to produce results, then I would say replace the drive. If you have an oscilloscope, you can check the input signals to confirm them.

EDIT:

Another thought, re-check the dip switch settings.
 
At this point I would pull all of the wires off of the drive and re-wire it. If that fails to produce results, then I would say replace the drive. If you have an oscilloscope, you can check the input signals to confirm them.

EDIT:

Another thought, re-check the dip switch settings.

No dip switches. These are 2001 era drives I have had since then but never used.

I will try a complete rewire next. I have access to a scope but have never used one.
 
Well I tried everything I could think of and no go on the one drive. I swapped it out for an extra Chinese drive I had and everything is working. Bad news is the power supply is too small. The motors stall way too easily for the machine to be useful.

Now to figure out how to get a larger power supply into the limited space I have in the box.

Jay
 
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