Axis run too far

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27 Aug 2013 18:53 #38148 by Rick G
Replied by Rick G on topic Axis run too far
It is not common for a stepper motor to over run, a step loss problem would normally be a stall or too short a movement. You could try to dramatically reduce acceleration.
Did you try the moves that were recommended?
The wiring changes?

Yes I can turn the coupling by hand if the machine is on.

Well that is not good, All the axis or just the bad one?
Some boards drop down the amps when at rest, but still should be able to hold their position.

Dave has experience with these boards.
You might want to post your config files for review.
Perhaps start over with the set up paying close attention to the step and direction timing.
Re check your latency, any errors messages?

Rick G

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27 Aug 2013 20:03 - 27 Aug 2013 20:03 #38150 by seppel
Replied by seppel on topic Axis run too far
No, the wiring changes can I try first on the weekend.

I can all axis turn when the machine is on, but I can't shift the portal. The Motor has 0,93 Nm, is it not normaly to turn it by a big coupling?

The step and space time is 15000 ns. There are no error messages. The latency is 12000ns but I've typed in 16000ns.
Last edit: 27 Aug 2013 20:03 by seppel.

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27 Aug 2013 21:52 #38156 by andypugh
Replied by andypugh on topic Axis run too far

Could I measure the current when the machine is on and not turning in DC?


Yes, but, you must _never_ disconnect the motors from the drives when the drives are powered. The TB6560 drivers hate that.

The problem looks to be due to the system not stopping when asked to. What happens at very low acceleration rates?

How fast is the motor spinning at G0 speeds?

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27 Aug 2013 23:27 #38159 by seppel
Replied by seppel on topic Axis run too far
the max y-speed is 10 mm/s and the acceleration is 100 mm/s².

I will test with decreased acceleration on the weekend. Thaks for your help

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30 Aug 2013 19:32 #38244 by seppel
Replied by seppel on topic Axis run too far
So, I've found the fault! After I changed the X and Y axis the Y runs exactly to the target. Consequential mechanism is okay and the step time is okay, too!

The fault musst be the chinese driverboard! right?

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31 Aug 2013 17:38 #38299 by Rick G
Replied by Rick G on topic Axis run too far

After I changed the X and Y axis the Y runs exactly to the target.


Perhaps you could explain exactly what you changed.

Rick G

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31 Aug 2013 23:02 #38316 by seppel
Replied by seppel on topic Axis run too far
I've changed the x and y pins in the config and the output wirings on the tb6560 board. After this the over runnig is on the x axis.

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01 Sep 2013 09:50 #38341 by andypugh
Replied by andypugh on topic Axis run too far

I've changed the x and y pins in the config and the output wirings on the tb6560 board. After this the over runnig is on the x axis.


That is quite remarkably strange. Quite the oddest thing I have heard of so far.

Here is a very speculative diagnosis. Many of the stepper boards include a 555 timer based step generator, and a header that allows you to jog your steppers with switches.
It is just possible that you have a faulty PCB that is adding extra steps via this circuit, but only if there are genuine steps too.

Frankly, as cheap as the board are, I would just change the board rather than try to diagnose. It seems that you have isolated the issue to the driver board.

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01 Sep 2013 15:15 - 01 Sep 2013 15:16 #38353 by seppel
Replied by seppel on topic Axis run too far
I 've order another TB6560 board Letmathe . It will arrive in the next days and I'am very hopefully to get better results in matters of the over running and a smoothly step sequence.
Last edit: 01 Sep 2013 15:16 by seppel.

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01 Sep 2013 17:51 #38358 by Rick G
Replied by Rick G on topic Axis run too far

I've changed the x and y pins in the config and the output wirings on the tb6560 board.


What happens if you change the pins back in the config to their original settings without changing the output wiring?
Of course the wrong axis will respond to moves but does the problem stay with x axis?

Rick G

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