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h4ppy-chris
27-01-2011, 07:09 PM
backlash compensation in mach3 any one use it? if not why?

M250cnc
27-01-2011, 07:31 PM
I don't use it as I have ballscrews so I don't have to.

Phil

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Jonathan
28-01-2011, 12:56 AM
I almost always use it. If, for instance, you're drilling an array of holes it will clearly make a difference to the accuracy - unless you're careful with the Gcode.
I've found in some instances it is of limited value since the backlash wont be a constant value.

Be careful with the velocity and 'shuttle accelaration' settings. The motors will loose steps with too low a setting for the latter, however to high a value will make the motion less smooth.


I don't use it as I have ballscrews so I don't have to.

Have you got two ballnuts preloaded on each screw then? Or just sufficiently low backlash to ignore it with one?

M250cnc
28-01-2011, 12:00 PM
Have you got two ballnuts preloaded on each screw then? Or just sufficiently low backlash to ignore it with one?

Two ballnuts on the lathe single on the mill same amount of backlash on each 0.05mm

Phil

h4ppy-chris
28-01-2011, 12:27 PM
Phil why don't you use backlash compensation to get rid of the 0.05mm?
i had 0.5mm now got it down to 0.02

M250cnc
28-01-2011, 12:43 PM
Phil why don't you use backlash compensation to get rid of the 0.05mm?

I did try but the machine in my mind didn't benefit, it sounded weird.

Parts i make come out perfect for me, so in my case it wasn't worth it. I also have a manual Bridgeport i can get better accuracy on the RF31 a lot easier.

All machines have some backlash, especially on a hobby machine if you think you have Zero backlash then you are not measuring correctly.

There is no substitute for almost zero backlash, software will do a job on small cuts but if you are taking big cuts with large amounts of backlash the cutter is going to be drawn in (Snatch) when climb milling and the potential is to lose position.

Also when climb milling with ballscrews the cutter is moving the table and the stepper is controlling the movement so you do not need as much stepper motor power.

When conventional milling the stepper has to fight the forces of the cutting action so you need a powerful motor.

Chris i know you have a mill already and you can tell how much extra force you need when manual milling in the conventional direction. You also get the best finish with climb milling.

Phil

h4ppy-chris
28-01-2011, 09:00 PM
thanks Phil a good read that nice 1.

M250cnc
29-01-2011, 10:34 AM
i had 0.5mm now got it down to 0.02

Hi Chris, i missed this statement first time using my phone. Sorry to burst your bubble but you haven't got rid of it, you have masked it with software. Backlash can only be removed by mechanical means.


thanks Phil a good read that nice 1.

Thanks
Phil

h4ppy-chris
29-01-2011, 10:59 AM
don't know if you've seen this Phil shows how to setup so no weird sounds and runs sweet.

http://www.youtube.com/watch?v=A27nOkTFYDY

M250cnc
29-01-2011, 12:11 PM
don't know if you've seen this Phil shows how to setup so no weird sounds and runs sweet.


Chris i appreciate your effort to help, but i use a Smooth Stepper now, so backlash is not working when using the SS.

I have seen the video before, cant really forget Hoss's dulcet tones. :lol:

Phil