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Author Topic: strange behaviour / offset  (Read 6618 times)

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Re: strange behaviour / offset
« Reply #10 on: September 26, 2012, 08:50:40 AM »
no it is a 3d milling at 1600mm/min 2mm deep pass on 6mm tool at 15000rpm

I even tried at 1000mm/min and same...

could it be at the 100khz are too much when several axis are in motion together??

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Re: strange behaviour / offset
« Reply #11 on: September 26, 2012, 10:03:33 AM »
Kernel has no effect with external devices, any limiting of frquency is done in the plugin.

Could be your Z is losing steps due to the short fast moves that 3D usually contains.
Have you tried reducing the acceleration for the Z axis?
Do you have the step pulse set to the correct state for your drives? ie active high or active low as some drives are particular about that.
Hood
Re: strange behaviour / offset
« Reply #12 on: September 27, 2012, 03:19:41 PM »
Pulse is at 5

Signal is active high And configured as such.

I feel it work for normal 2mm step over passes but not for the 0.2 ones...

 I tried to reduce and increase and same...

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Re: strange behaviour / offset
« Reply #13 on: September 27, 2012, 03:28:00 PM »
Pulse width has no effect when using an external controller so thats not the problem. The CSMIO controllers have 50% duty cycle on the pulse outputs.

Only thing I can think of is you could try swapping drives or motors from other axis to see if it could be one or the other that is the issue.
Hood
Re: strange behaviour / offset
« Reply #14 on: September 28, 2012, 02:29:19 PM »
what about the microstep resolution setting in the drives...anything special to be aware?
Re: strange behaviour / offset
« Reply #15 on: September 28, 2012, 02:56:02 PM »
I increased motor acceleration to 400 and it seems better... will see after the 9 hrs of milling but so far it did not seem to loose steps...

any logics on that?

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Re: strange behaviour / offset
« Reply #16 on: September 28, 2012, 04:13:36 PM »
According to most people the optimum microstepping for a machine axis is around 10.

Hood
Re: strange behaviour / offset
« Reply #17 on: September 28, 2012, 11:54:04 PM »
then I should maybe reduce it to 10...it is currently 50
Re: strange behaviour / offset
« Reply #18 on: September 29, 2012, 02:34:51 AM »
ok... did further test. have not yet switched the drives or motor but:
- I set all drives to 10 microsteps and adjusted motor settings accordingly. which means that I divided by 5 the number of steps per rev compared to before.
- I created a program of 4 hole of 5mm deep positionned on rectangular way. after each hole the machine goes up to 10mm above the part surface.
- Then I offset the z to 50mm to have safe distance and runned the program.
- after completion I go back down and the zero is no more 50mm it is approx 44mm. which means a shift of approx 6mm. which is strange because in my previous test on the large 3d part, it was doing positive offset.

obviously by reducing the microsteps, I increased the shift...

any good idea following that test? I will shift the drives now...
Re: strange behaviour / offset
« Reply #19 on: September 29, 2012, 02:37:25 AM »
forgot to mention something really strange.

if I run a simple program like:
g1 x0 y0 z0 f4000
g1 x5 y5 z5
g1 x0 y0 z0
...

it comes back in position quite well...