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Author Topic: Is backlash compensation broken?  (Read 7676 times)

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Offline RICH

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Re: Is backlash compensation broken?
« Reply #10 on: August 11, 2011, 06:01:51 AM »
micro......
Quote
I can not get backlash comp to work either no matter what I put in for a number nothing changes.
We need some more info:
Version of Mach your using? Using PP or SS and any breakout boards?
DId you check the box in CONFIG>BACKLASH to implement it, save settings , and restart MACH?
Can you post your xml  file?

RICH

Re: Is backlash compensation broken?
« Reply #11 on: August 11, 2011, 07:45:02 AM »
It works on my setup to an extent.  The deal is you won't see the compensation if the distance of the reversal is less than the compensation you had dialed in.  For instance, say you have .005" dialed in.  If you jog left in .001" increments, then reverse directions, you would expect, and done properly, you should see the stepper twitch the .005" plus the .001" commanded.  As implemented, you won't see the backlash compensation kick in until the second or third reversed step.

In practice, if the reversal distance is greater than .005", then the BL would compensate properly.  If you are machining a round pocket, especially a larger one, the reverse step may well be less than that and your hole will not be smooth.

The parts I am making are not only functional, but also cosmetic.  They have six larger holes in them I used to bore with a boring head.  I had hoped to mill them to speed things up, but they didn't look good enough with the faulty BL compensation.  I ended up removing the SS, bought a C10 board for use with my old desktop with the parallel port until the driver gets fixed.

Offline Hood

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Re: Is backlash compensation broken?
« Reply #12 on: August 11, 2011, 07:49:50 AM »
bought a C10 board for use with my old desktop with the parallel port until the driver gets fixed.

Are you using Backlash via the PP?
Hood
Re: Is backlash compensation broken?
« Reply #13 on: August 11, 2011, 08:13:54 AM »
Sheesh, I thought I was in the Warp9 (Smooth Stepper), forum...
The BL compensation is broken when using the smooth stepper.  The PP works fine however.

Offline Hood

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Re: Is backlash compensation broken?
« Reply #14 on: August 11, 2011, 08:26:49 AM »
So you are getting perfect circles with no marks when using backlash in the PP?
 I would have thought with physical backlash that comp would never stop that happening unless you are taking a very fine finish cut, but have never messed much with the backlash in PP or SS. I do use it in the SS for rigid tapping and its great for taking the lash out of the spline drive on the spindle although I rarely do rigid tapping anyway.

Hood
Re: Is backlash compensation broken?
« Reply #15 on: August 11, 2011, 09:03:37 AM »
I have been using R3.043.022 after reading some post I am using the R3.043.039. I'm not sure what PP or SS is? I followed the procedure on setting backlash in the box and restaring the program. I am using a galil card and servos. How do I post my xml file?

Offline Hood

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Re: Is backlash compensation broken?
« Reply #16 on: August 11, 2011, 09:09:14 AM »
Not sure if the Galil supports backlash, you would have to ask on that part of the forum.
Hood
Re: Is backlash compensation broken?
« Reply #17 on: August 11, 2011, 09:43:30 AM »
I have been using R3.043.022 after reading some post I am using the R3.043.039. I'm not sure what PP or SS is? I followed the procedure on setting backlash in the box and restaring the program. I am using a galil card and servos. How do I post my xml file?

PP is parallel port, SS is smooth stepper.  The SS allows you to use a laptop with Mach3 and runs through the USB port.  It gives you two parallel ports to work with and works real well for the most part.

Offline Sage

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Re: Is backlash compensation broken?
« Reply #18 on: August 11, 2011, 05:10:34 PM »
Excuse me if I'm missing something here but what difference does using the PP or SS have in backlash compensation. My understanding is that Mach simply issues additional ordinary steps in a particular direction to complensate just before sending out the regular steps - NO?
 Why would it need to be handled any different through the SS. OR why would SS choose to handle it any different if it is handled already by mach when directly connected by the parallel port?

Sage


Offline Hood

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Re: Is backlash compensation broken?
« Reply #19 on: August 11, 2011, 05:19:14 PM »
External controllers such as SS, DSPMC, Galil etc etc use a plugin to talk to Mach so things like backlash comp need to be handled by the external controller.
 I am not sure how many of the external controllers actually do backlash comp.
Hood