Mach3 Calibration

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Mach3 Calibration

Postby trwalters001 » Thu May 05, 2011 12:45 pm

Hi All,

I'm trying to calibrate my axes with Mach3.

I'm using the "Set Steps Per Unit" button on the Settings page.
My system is set up for 1000 steps per inch. I've used a dial indicator as well as an 8" caliper.

I can get the system to move exactly as far as I need to, and then I tell Mach3 to save that setting.

If I want to run the test again to get more accuracy, should I reset the steps per inch to 1000?

The reason I'm asking is that I can calibrate both axes so that they each move exactly 1" when I tell them to move 1". I then run a gcode file that has a 1" square in it. The square comes out completely wrong (example: .980" x 1.015".) If I run the square again, the dimensions remain the same.

Any ideas/advice/suggestions?

Thanks!

Tim
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Re: Mach3 Calibration

Postby bdring » Thu May 05, 2011 2:28 pm

What do you mean by "calibrate"? Are you using something other than 1000 with Mach3?

Have you checked for backlash? Going past 1.00" does not sound like backlash, but it is possible.

The results are a drawn line, a cutout square???
Bart
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Re: Mach3 Calibration

Postby trwalters001 » Thu May 05, 2011 2:44 pm

Hi Bart,

Maybe I used the wrong terminology...

My system is using 1000 steps/inch.

I'm referring to the Mach3 Install & Config Guide, Section 5.5.2.3 "Automatic Setting of Steps per Unit".

In performing that procedure, Mach would set my steps per unit to something (slightly) other than 1000 (like 1006.8235454).

During that procedure, and after I let Mach set steps per unit, I could tell either axis to move 1", and it would move 1" +/- .0005.

I would then load my gcode file that draws a 1" square.

Let's say that my focused spot is .006" in diameter. That means that if I cut a perfect square, with no offset for tool diameter, the cut-out square should be .994" x .994".

My cut-out squares would be (for example) .980" x 1.015".

I'll be checking backlash tonight.

Tim
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Re: Mach3 Calibration

Postby bdring » Thu May 05, 2011 2:53 pm

The steps per inch on your system should be a pure calculation. Do not let Mach3 do it.

There may be factors that make your system off a few apparent steps, but these generally do not accumulate. Letting Mach do it will quickly add up over distance.

You could have an alignment issues too. If the beam drifts over distance, that will show up on the workpiece.
Bart
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Re: Mach3 Calibration

Postby trwalters001 » Thu May 05, 2011 3:06 pm

If one or more pulleys aren't *exactly* the right diameter, wouldn't that affect steps per inch and need to be compensated for?
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Re: Mach3 Calibration

Postby bdring » Thu May 05, 2011 3:17 pm

Yes, on a small scale, but that will not accumulate. The belt teeth keep that in check. Things would have to be so bad that eventually a the belt would jump a tooth.
Bart
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Re: Mach3 Calibration

Postby trwalters001 » Thu May 05, 2011 3:20 pm

I'll reset them to 1000 steps per inch.

Thanks!

Tim
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Re: Mach3 Calibration

Postby trwalters001 » Thu May 05, 2011 10:50 pm

I reset both axes to 1000 steps per inch and ran my square routine.

0.997" x 0.997"

Yay.
:D

Thanks Bart!
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