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interpolation issues
« on: May 17, 2020, 12:27:56 PM »
Hey, just built a router,. decent size,. went through a few different controllers and founds the pokeys57cnc and was impressed enough with it to where i bought their stepper drivers as well (the 6A ones)

had and still having a issue though, during any interpolation moves it seems to loose track of what its doing and a best i can describe it, is overdriving the steppers causing them to jitter and hum. it will come out of it after a second or two but its an unacceptable fault in any way. at first i thought it was the cheap chinese drivers i had and i put in the pokeys drivers but it didnt help, the computer was my second suspect and has been changed out with something slightly faster but no change. feed speeds do not make a diffrence, but even if it did i would still want it fixed.

mach4 seems to know when this is going on and alters the cutpath to reflect the new 'position' after the stutter.

i have attached a screenshot of what mach4 looks like when this happens


if any of you can tell me whats going on i would love to know

some side info,
connecting with Ethernet. the computer is a dual core 1.3ghz with 8gig of ram. running windows 10. this one is about 50% faster then the previous one i was using, so i am semi confident that it inst the issue.

thanks
-Justin

Online Graham Waterworth

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Re: interpolation issues
« Reply #1 on: May 17, 2020, 02:18:44 PM »
Can you post your code and a picture of what it should look like without the error
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Re: interpolation issues
« Reply #2 on: May 17, 2020, 03:20:21 PM »
that picture was an example, it does this whenever any interpolation operation is preformed. not every operation though. i can run a half hour with no issue, or 30 seconds,.. its random.

the attached code is for the image, with a redraw of it without error,.. its just a hemispherical depression.

it was generated with fusion 360, but i have had the same issue with freecad and handwritten code to cut circles.

Online Graham Waterworth

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Re: interpolation issues
« Reply #3 on: May 17, 2020, 04:18:45 PM »
The code looks fine, I would guess it is noise on the step / dir cables or a bad connection / joint, make sure the cables are shielded with only one end of the shield connected to a common ground.

Make sure you have no power wires close to the signal wires.

Spindle power cables are bad for this.

Without engineers the world stops
Re: interpolation issues
« Reply #4 on: May 17, 2020, 05:19:30 PM »
that would explain a lot,. it never happens on the Z axis, but happens on the Y a fair bit, z and y both are run un-shielded along side a 120v ac line ( using a router for spindle. ) i can run the router cable outside the cable tracks to see if that helps short term while i get more shielded cable. i had run out half way through the project and had some cable left over from a heat pump install..

i do have an occasional issue with the X axis doing the same thing but its cable run is different, and only about 2 feet are un-shielded.  that one i can run in shielded,

do you recommended i run all the shields to a common ground?

i have some ferrite cores i could put on the spindle power cable,. dunno how much good they would do,

Online Graham Waterworth

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Re: interpolation issues
« Reply #5 on: May 17, 2020, 05:32:53 PM »
All signal cable should be twisted pair shielded for best protection from noise.  All grounding should be to one point to stop earth loops.

 
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