Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: SSPW on March 20, 2015, 01:44:51 PM

Title: Table Compensation using Formulas
Post by: SSPW on March 20, 2015, 01:44:51 PM
Hi all. Just finishing first rev of my first cnc machine. I am new to everything cnc and mach3.
Initial testing showed a small 0.3mm drop across my 575mm width and 0.1mm across my 975mm length.
I will probably go back a do some mechanical correction, but i need to cut some parts now and just cant keep messing with my machine now.

I have found everything thing i needed about Mach3 here and other forums and YouTube so far.
I searched the MACH3 docs and web and nothing really good on Mach3 formulas.
Few references, mostly just mentions of formulas, but no good examples.

So i messed with in last night and came up with a solution to my immediate needs.
Might be useful for new comer and who knows, maybe some existing users too.

Before anybody says just face a sacrificial table top, i cant do it, i have nice alum tslot table and need to mill parts in vise or metal fixture plates.

So basically i probed around my table and found a bunch of zeros. Recorded the xyz points.
Then i made a EXCEL worksheet that was the excel solver addin to finds the best fit plane from all the measured points.
It makes the formula to compensate the z axis as a function of x and y.
You just cut the formula from excel and paste right into Mach3.

You can do the whole table or part or just a local fixture.
If you add a fixture or fixture plate, you can probe that local work area out and compensate for how its laying.
Just remember to remove formulas or switch back to a global table formula after local use!

Makes me think i should figure if a custom button could switch between formulas (local/global).
Hum something to look at later.

Spreadsheet can be downloaded here (
Use at your own risk!
Anyways, this my first post here. Hope its a help to somebody or saves you some time.

Title: Re: Table Compensation using Formulas
Post by: SSPW on March 20, 2015, 03:34:33 PM