Lost steps jogging at low jog rates.

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25 Mar 2017 20:44 #90262 by Charlieslasher
Lathe xz axis 2.7.7 updated linuxcnx.
G540
PP
381oz steppers

When jogging at less than 100mm/min feed rates the axis dro will move but the actual motor wont. Only happens on x axis. Also seems to do it homming the x axis the dro numbers change faster than the axis moves. I will try swap motors and drives to eliminate that. But seems like software/pc hardwear.

I some times get real time errors that i am working to fix with more ram. But any idea what might cause this.

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25 Mar 2017 22:41 #90268 by PCW
This (step loss at low speeds on G540s ) can be caused by parallel port interface issues
(low high level drive from parallel port or too short step times)

You might try increasing the step times to 5 or 10 usec if they are not already this long

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26 Mar 2017 00:20 #90274 by Charlieslasher
Which file to change step times with out using the configuration utility?

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26 Mar 2017 16:45 #90298 by Wirewrap
There is obviously a problem with some G540 controllers. I have two G 540 units. One of them refuses to step on the Z channel below 150 steps per second. Tested with 5V square wave drive from a signal generator. Swapping the driver sub-boards around the problem is still on the Z axis on one unit. It quite distinctly stops and starts stepping when the input frequency is varied around 150 Hz. Pulse ratio has no appearent effect.

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26 Mar 2017 23:34 #90321 by Charlieslasher
Ok i will try swap the axis as im only using 2 of 4. Also it worked ok when i tested it yesterday with no changes. So no idea what realy is the problem.

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27 Mar 2017 00:13 #90325 by tommylight
The G540 uses a divide by 10 on all the inputs, so most probably the problem is there. That is not microsteping, so for 9 pulses the motors do nothing.
I had 2 of them, both are still working properly used daily, i realy liked them for many things, they are nice and usable and quite powerful for the size, but i realy hated not having the option to disable that divider. I also have G320's and G212's but i have removed dividers from them. When used with low gearing or directly driving a belt, the error in dimensions is noticable.
Also do you have resistors wired on the d9 ports? They absolutely do not like high inductance motors, so try swaping the motors.

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27 Mar 2017 06:17 #90331 by Charlieslasher
I have ran g540s with two types of steppers for 4+ years with not to many problems so i assumed it wasnt hardwear. But it maybe the way linuxcnc works with the g540. I have just switched to linuxcnc.

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27 Mar 2017 11:52 #90350 by tommylight
Linuxcnc does not care or know what hardware is connected to it in your case it just sends the signals.
Has nothing to do with Linuxcnc.
Can you please go through this post again and test the advices given here and report back.
You know what they say about assumptions......

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27 Mar 2017 21:39 - 27 Mar 2017 21:53 #90397 by Charlieslasher
I get the lost steps jog problem to repeat by letting linux cnc and the computer sit for 30mins + then just one axis fails to jog at very low speeds. At startup it works fine.
Update
Looks like its the g540 drive. Swapping axis to a spare axis on the board and it works. So must heat up and stop working or something weird. The g540 had damage from over current through a poor conection early on in its life so this could be related.

Will continue to test
Last edit: 27 Mar 2017 21:53 by Charlieslasher. Reason: Test results

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