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Travel per Revolution set to 1mm, stepper turning only 3/4 of a turn when asked to move 1mm

Started by lpdc on in TinyG Support. 2 replies, last activity Jun 22, 2012.

lpdc #2595

Hello,
I finally got time to try and play around with my recently received TinyG.
I simply hooked it up to an ATX power supply (+5V and +12V) and to a reclaimed stepper motor (one exactly like this : http://www.motors.wrobots.com/EM-258_17PM-K212-PIT.php)
I used coolterm to send commands but found something weird that I can't explain. Maybe someone can shed some light on what I am doing wrong.

I mapped the 3rd motor to the Z axis (above stepper is plugged on the 3rd slot). No load is attached to the motor, only a piece of tape to act as a flag.
I set the Travel Per Revolution to 1mm but when I issue commands like G0 Z0,G0 Z1, G0 Z2 etc... the motor does not spin in full turns. It seems that it spins roughly 3/4 of a turn each time. Since the Travel Per Revolution is 1mm, I expected 1 full turn for each mm of requested movement. Am I missing something ?

Tried various Velocity Maximum from 100mm/min to 500mm/min (only values below 400mm/min enabled the motor to spin correctly, anything above would cause the motor to spin only during acceleration and deceleration phases but not during cruising speed)
Tried various micro stepping values (1, 2 and 8)
Tried various positions on the TinyG trimpot for the 3rd motor.

Looking forward to reading any suggestion,

Fabrice

lpdc #2596

Hello again.

Sorry about previous post, you can disregard it.

I replaced the 12V power supply with a 19V laptop power supply and now the motor is behaving as it should (plus I can use a Velocity Maximum of 1000mm/min without the motor dropping steps)

Either there was something wrong with my ATX power supply or 12V was simply not enough and the motor was dropping steps.

Now everything is fine.

Alden, Riley, you can either delete this thread entirely or leave it if you think it might help someone else.

Once again, my apologies for posting too quickly.

Fabrice

aldenSynthetos #2597

Fabrice,

No worries, we'll leave it up. These systems require tuning in many layers - the mechanical layer for the machine itself, the motors, and the settings and software.

If you have not already done so, I'd recommend reading the section on setting motor current here:

http://www.synthetos.com/wiki/index.php?title=Wiring_TinyG

- Alden

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