Machsupport Forum

Mach Discussion => Mach4 General Discussion => Topic started by: phando on July 14, 2021, 08:18:51 PM

Title: Calibration Issue
Post by: phando on July 14, 2021, 08:18:51 PM

Hello,
I am finishing my my migration from Mach3 to Mach4. I just got done with calibrating my axis (without backlash) and noticed an issue. My calibration was done over 1". The mill is moving more accurately than I was hoping. The issue is when I move less than 1" there is a progressive error (not moving far enough). Once the machine gets to 1" it is perfect. I am unsure if the error continues on the other side of 1" but if it does, I would imagine the machine will be moving too far.

Anyone else run into this?

Title: Re: Calibration Issue
Post by: Cbyrdtopper on July 15, 2021, 11:23:46 AM

If you have the ability, calibrate it to a longer length.  The longer, the more accurate.  I use a dial indicator to calibrate axis on our machines, but I always check to be sure it moves further accurately.

Title: Re: Calibration Issue
Post by: phando on July 15, 2021, 12:56:04 PM

@Cbyrdtopper, thank you for the response. Using a ruler I was able to see that the mill is off by 1/16" over 20". I think where I may have been going wrong is that I am not preloading the screw in the right direction before taking my calibration measurement. Today I will try to move the screw 0.05 (in the measurement direction) to zero then measure my 1" with the micrometer. Maybe moving back and forth between 0 and 1" was adding backlash to my calibration. Additionally I will look into taking the backlash out using the screw adjustments.

Title: Re: Calibration Issue
Post by: Cbyrdtopper on July 15, 2021, 01:03:02 PM

Getting the backlash out mechanically is absolutely the best way to do it.  Removing backlash in the software is just like a bandaid... it just masks the problem.
If you have a good quality ruler, use that for your calibration.  Get an extremely fine point tool in the spindle and move it from 0 to 20 and try that.  It should get you pretty close across 20" of travel.

Title: Re: Calibration Issue
Post by: phando on July 15, 2021, 02:31:59 PM

I am out of the woods, thank you. This is the most accurately I have ever calibrated a machine. Super stoked!

Title: Re: Calibration Issue
Post by: RecceDG on July 16, 2021, 11:15:20 AM

What is also instructive is placing a dial indicator - a sensitive one, like a tenths indicator - and jogging in 0.001" increments. It demonstrates backlash and other weirdness immediately