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Author Topic: MDI and DRO not Matching????  (Read 3176 times)

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MDI and DRO not Matching????
« on: February 23, 2009, 08:49:50 AM »
Ok I need a little help.
I have Mach3, I  use it for my lathe and my mill with no issues. steps per are calculated and are acruate with out using the calibration utillity.

I just built a 4 x 4 plasma table using 20 pitch rack, meshing pinion is 30 tooth, pinion pulley is L timing belt 24 tooth. stepper pulley is 16 tooth.

Now because the rack and pinion are spring loaded there is no clearance, so calculations will not be accruate.

Now I have used the Calibration utillty and I get something like 637.************ for steps per. I used a linear scale attached to the axis and calibrated it to 4" and read it to .### 3 desimal places.

Now when I enter G0 X1 in the MDI the dro will go to something like .9995, or some other irrational number.

Is this normal?

None of my other profiles do this. Did I miss something?

Please Help ???

Offline ger21

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Re: MDI and DRO not Matching????
« Reply #1 on: February 23, 2009, 09:09:42 AM »
It could be due to your steps/unit not adding up to exactly 1. What is your exact steps/unit?
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: MDI and DRO not Matching????
« Reply #2 on: February 23, 2009, 09:25:56 AM »
I am at work, I will have to get it later. I will never =1 becaues the full mesh does not follow the theroetical Pitch circle. Right?

I will let you know latter. Maybe I can round it off?
Re: MDI and DRO not Matching????
« Reply #3 on: February 23, 2009, 05:59:11 PM »
Ok home now

steps per for X and Y which both have same mechanical setup are

637.385782

Any ideas????

Offline ger21

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Re: MDI and DRO not Matching????
« Reply #4 on: February 23, 2009, 06:53:00 PM »
When you tell Mach3 to move 1inch, it moves 637 steps, which is .99939

638 steps is 1.00096

What's happening is that mach is getting as close to 1 as it can, given you're steps/ unit.
Gerry

2010 Screenset
http://www.thecncwoodworker.com/2010.html

JointCAM Dovetail and Box Joint software
http://www.g-forcecnc.com/jointcam.html
Re: MDI and DRO not Matching????
« Reply #5 on: February 23, 2009, 08:15:10 PM »
OK I will live with it.

I cut some polycabanate test pcs that was within .005 to .007 with a crapy Roybi router.


Thanks for you input.