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Davidhcnc
03-11-2009, 01:48 PM
If you have a bit of knowlege with Mach3 machine control then please cast an eye over my problem.

V carve pro CAM software
Stepper driven mill.
Backlash compensation enabled. The trouble clears when compensation is not used.

The trouble is x axis stalls and then proceeds on line 1239 every time I try it..

During the stall the y axis backlash compensates( as the g code requires a move of .001( see previous Yaxis position)


Lets assume this in not a mechanical blockage or faulty steppers/drives/electrical interferrence/hardware trouble. All these aspects are proven.

Look at the screenshot and highlighted is line 1239.

I have a notion that a solution would be to reduce the number of decimal places in the G code but do not know if this is possible.


Any advice gratefullt recieved:)



http://homepage.ntlworld.com/david.hull35/Mach%20screen.JPG

sdeering
03-11-2009, 05:31 PM
Have not used the backlash compensation sorry. What speed of Pc are you using? 1ghz or better is recomended and not a laptop. I would think it sould work fine to .oo1"

What do you mean stall? All axis stop then continue without loosing steps? Like the PC can't keep up when it has to calculate the backlash?
Just an idea.
Stephen

jacampb2
03-11-2009, 06:50 PM
I have seen discussion about Mach's backlash compensation elsewhere. The general consensus is that it is not intended for continuous machining, and will cause all sorts of errors and problems. In fact, the manual says much the same thing-- see bellow.

http://www.rollmeover.com/bronco_fab/bridgeport/mach3_backlash.jpg

Good Luck,
Jason

Davidhcnc
03-11-2009, 07:06 PM
Have not used the backlash compensation sorry. What speed of Pc are you using? 1ghz or better is recomended and not a laptop. I would think it sould work fine to .oo1"

What do you mean stall? All axis stop then continue without loosing steps? Like the PC can't keep up when it has to calculate the backlash?
Just an idea.
Stephen


The PC is overspec'ed. I am confident that this is not the problem. Proved by..I can run my machine at 4 times the speed, including rapids but it will not pass this line 1239.

By stall I mean loose a load of steps.


The resolution in not .001"

If I am reading it correctly it is .001mm for the Y move. For me this is a redicously high resolution and I would like to lower it to .01mm.. not that I think about this, it is comming out of the V carve pro software.


Thanks for your input

Davidhcnc
03-11-2009, 07:11 PM
I have seen discussion about Mach's backlash compensation elsewhere. The general consensus is that it is not intended for continuous machining, and will cause all sorts of errors and problems. In fact, the manual says much the same thing-- see bellow.

http://www.rollmeover.com/bronco_fab/bridgeport/mach3_backlash.jpg

Good Luck,
Jason

Indeed Jason and thanks for your reply

I am aware that there are limitations with the backlash comp. My machine copes with backlash compensation properly for 95% of the time. Then occasionally , like today , there is just a characteristic in there that fouls. I want to change something , I have tried every other setting, and if we can raise the bar even to 96% then that is progress:)

Sparky_NY
03-11-2009, 08:39 PM
I have been using backlash comp on my mill with mach for a couple years without any issues. The manual statement on backlash refers to it not being a cure all and that mechanically fixing the backlash is the best route. It will not cause crashes.

There is not enough info to really troubleshoot the issue but having the accelerations set to high in the motor tuning would be a possibility as well as having the shuttle accel set to low. (shuttle accel is the rate of accel/decel before and after backlash adjustment is made)

3 decimal places is no sweat for mach.

macona
03-12-2009, 04:52 AM
The acceleration is too high combined with the backlash comp. Try lowering the acceleration for that axis and see what happens.

I use backlash comp and it works fine. There is no such thing as a backlash free machine. All controls have backlash comp in them, I dont know why mach would have a problem with it.

Sparky_NY
03-12-2009, 01:02 PM
The acceleration is too high combined with the backlash comp. Try lowering the acceleration for that axis and see what happens.

I use backlash comp and it works fine. There is no such thing as a backlash free machine. All controls have backlash comp in them, I dont know why mach would have a problem with it.

The shuttle acceleration on the general config page also effects backlash, it is the accel/decel rate to and from the pause when backlash is taken up.