Stepper Motors
Posted by HSRepProject
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Stepper Motors April 19, 2010 09:39AM |
Registered: 14 years ago Posts: 16 |
Good morning,
We began installing the belts and final wiring on our RepRap system today. We went to test the motors, only to have them twitch back and forth. We are using the Kysan motors, the same ones you can get from Makerbot. We used a Dremel tool with a grinding stone to flatten the shafts of the steppers. This is necessary to fit the printed gears onto the motors. At least two of the ones we machined are twitching back and forth instead of spinning properly. The motor that we did not machine still seems to work fine. If anyone has any thoughts on what might be wrong, or how we can fix it, it would be greatly appreciated.
~Ryan
We began installing the belts and final wiring on our RepRap system today. We went to test the motors, only to have them twitch back and forth. We are using the Kysan motors, the same ones you can get from Makerbot. We used a Dremel tool with a grinding stone to flatten the shafts of the steppers. This is necessary to fit the printed gears onto the motors. At least two of the ones we machined are twitching back and forth instead of spinning properly. The motor that we did not machine still seems to work fine. If anyone has any thoughts on what might be wrong, or how we can fix it, it would be greatly appreciated.
~Ryan
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Re: Stepper Motors April 19, 2010 10:16AM |
Registered: 15 years ago Posts: 264 |
This happens when the wiring is incorrect, or when the stepper driver is not providing enough current.
You can use a multimeter to figure out which pairs of wires belong to the same coil. If the wires are on the same coil there will be some resistance between them, but if they are on a different coil there will be no connection (displayed as an overflow). Make sure the wires that are on the same coil are next to each other on the connector.
Also double check to make sure all the connections are good. A loose wire will cause twitching.
You may have moved the shaft out of position or let some metal shavings get into the stepper motor. Both cases can increase the amount of torque (and current) required by massive amounts making it impossible to run the stepper. The only fix for this I can think of is to carefully disassemble the stepper, clean it out and reassemble it.
1. What stepper driver are you using?
2. Have you tried running the bad stepper motors on the same stepper driver that runs the good stepper motor? What was the result?
3. Do you have these problems when you try to run the stepper motor with nothing connected to it?
Darwin clone, Gen 2 electronics, Arduino Duemilanove w/ AtMega328, 5D Firmware, Pinchwheel extruder
[www.codeerrors.com]
You can use a multimeter to figure out which pairs of wires belong to the same coil. If the wires are on the same coil there will be some resistance between them, but if they are on a different coil there will be no connection (displayed as an overflow). Make sure the wires that are on the same coil are next to each other on the connector.
Also double check to make sure all the connections are good. A loose wire will cause twitching.
You may have moved the shaft out of position or let some metal shavings get into the stepper motor. Both cases can increase the amount of torque (and current) required by massive amounts making it impossible to run the stepper. The only fix for this I can think of is to carefully disassemble the stepper, clean it out and reassemble it.
1. What stepper driver are you using?
2. Have you tried running the bad stepper motors on the same stepper driver that runs the good stepper motor? What was the result?
3. Do you have these problems when you try to run the stepper motor with nothing connected to it?
Darwin clone, Gen 2 electronics, Arduino Duemilanove w/ AtMega328, 5D Firmware, Pinchwheel extruder
[www.codeerrors.com]
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Re: Stepper Motors April 19, 2010 12:14PM |
Registered: 14 years ago Posts: 16 |
Thank you for the advice mccoyn. We are using the techzone remix electronics set. We have tried running the bad motor on a driver we know to be good, and the same twitching occurred. We are currently running the motors with only the gear attached. The belts have been removed.
Thanks,
Ryan
Thanks,
Ryan
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Re: Stepper Motors April 20, 2010 06:58AM |
Registered: 14 years ago Posts: 1,092 |
Ryan: Did you cover the bearing assembly before working on the stepper motor? The bearing assembly is where the shaft enters the motor. If you get anything in there (such as ground metal) you may end up with motor problems.
If you buy new motors, and want to avoid this happening when you work on the shafts, cover the bearing assembly and shaft with blu-tac. Don't press it in hard though, else you'll end up with blu-tac in the bearing.
If you're feeling particularly lucky, you could try opening up a bad stepper and seeing if there are any contaminants you can clean out. It's not something I'd do with a good stepper, but if it's dead otherwise, it might be worth a try.
If you buy new motors, and want to avoid this happening when you work on the shafts, cover the bearing assembly and shaft with blu-tac. Don't press it in hard though, else you'll end up with blu-tac in the bearing.
If you're feeling particularly lucky, you could try opening up a bad stepper and seeing if there are any contaminants you can clean out. It's not something I'd do with a good stepper, but if it's dead otherwise, it might be worth a try.
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Re: Stepper Motors April 20, 2010 03:36PM |
Registered: 14 years ago Posts: 28 |
I suggest you try to feel whether this is a mechanical problem or an electrical one:
disconnect the stepper from the electronics. Also make sure that the wires of the stepper are not touching each other or the motor housing (else electrical braking will confuse you).
Then turn the axis manually for several revolutions in both directions and feel whether it rotates freely. If it locks up you have a mechanical problem, if it does not lock up you probably have an electrical problem.
If you decide to open up a stepper motor make sure you do it in a place where no iron filings are present. The magnets in the rotor of a stepper are so powerful that it is *very* hard to remove metal filings. If you find metal filings in the motor it is probably easiest to remove them using some flexible sticky tape like painters tape.
Taking a stepper motor apart and putting it together again is not hard, the hardest part is to keep them clean and free from metal filings.
disconnect the stepper from the electronics. Also make sure that the wires of the stepper are not touching each other or the motor housing (else electrical braking will confuse you).
Then turn the axis manually for several revolutions in both directions and feel whether it rotates freely. If it locks up you have a mechanical problem, if it does not lock up you probably have an electrical problem.
If you decide to open up a stepper motor make sure you do it in a place where no iron filings are present. The magnets in the rotor of a stepper are so powerful that it is *very* hard to remove metal filings. If you find metal filings in the motor it is probably easiest to remove them using some flexible sticky tape like painters tape.
Taking a stepper motor apart and putting it together again is not hard, the hardest part is to keep them clean and free from metal filings.
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Re: Stepper Motors April 25, 2010 11:53PM |
Registered: 14 years ago Posts: 800 |
i had that same issue when i first tried to test my stepper motor driver and for me it was trying to step too fast for my motor or the controller i am not over sure just yet. you may want to try slowing your stepper down a little to see if that helps
[mike-mack.blogspot.com]
[mike-mack.blogspot.com]
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