Hey everyone.

I need some help with the STEPS PER part of Mach 3. Putting a dial indicator on my CNC movement doesn't really equate to my STEPS PER calculations.
Also, upon cutting 1" squares. My squares seem to turn out 1.0000" Y, and 1.0040" X
Are STEPS PER subject to fine tuning or is the calculations you do, depict exactly what the STEPS PER should be?

Here is the info on my machine:

Techno Isel Model 040 http://www.techno-isel.com/Tic/H830/HTML/H830P046.htm

Leadshine Closed Loop stepper motors and drives http://www.ebay.ca/itm/Leadshine-Closed-Loop-stepper-Drive-motor-HBS507-573HBM20-1000-3PH-2NM-57mm-NEW-/121559936057?hash=item1c4d896c39:g:dxoAAOSwVL1V-OrR

Here is the info I am putting into a Stepper calculator revision 1:

Degree/step - 1.2

Pulse/rev (micro stepping) - 4000

Leadscrew threads/in - 5.08
Thread starts - 1

Steps Per Inch - 20,320



When setting up a dial indicator to the CNC movement of X and Y, 20320 step per doesn't get me to 1". 20335 gets me to 1" right on the money.
Does anyone have any ideas or can point out what I am doing wrong?

Have you performed a comprehensive backlash inspection on the axis' ?

Are you approaching the indicator at least 2 moves in the SAME direction ?

Have you performed a comprehensive backlash inspection on the axis' ?

Are you approaching the indicator at least 2 moves in the SAME direction ?

I have made sure to minimize the backlash as much as possible.
For instance, the axis starts at -1.0". I run the axis to +0.0", which is against the dial indicator (then I zero my dial indicator). Then I command +1.0" in Mach 3 and see if the axis moved that amount. Which is does, but at a different steps per inch amount than calculated. 

Are STEPS PER subject to fine tuning or is the calculations you do, depict exactly what the STEPS PER should be?

 

With a perfect machine in a perfect world, yes, calculations.
If what you are measuring is consistent in all areas of movement, I would adjust the steps-per accordingly.
I'd still be suspicious of a mechanical issue though.

I agree Overloaded. Nothing is perfect and calculations are good enough to get you close. Then adjust counts per based on actual measurements. If 20335 gets you to one inch then so be it. 

Another option would be to use the axis calibration feature in Mach , "ALT 6" tab to get the screen.
Works very nicely. For the move, the longer the better, ie; if you have 6" of axis movement do a 5" move.

RICH