Hello everybody ,
I have recently built my own machine which has been cutting for a few months and everything seemed fine. I calibrated the steps per mm using a dial gauge and the machine cut perfect circles. However over the next couple of days I have been asked to cut some very accurate sign plates which will have vinyl attached to them.
Anyhow my problem is this:- when set as per my dial gauge readings I can repeatedly cut perfect circles at the correct dimension. However when I try to cut a rectangle at say 400mm by 100mm one axis is a tad longer (say 101 )and the other shorter (say 395). If I treat this discrepency as a percenage and adjust accordingly to my steps per mm, sure enough I then cut the rectangle correctly. However the circle is then eliptical (which you would expect , given both x and y run rack and pinion of the same type so clearly need the same steps pr mm).
Do you think I am missing something here?
Is there a setting in mach 3 for when axis move in a perfect linear fashion, and counter that when running in circles so to speak!
I just cant work this out , but the longer the distance the greater the error so I dont think it is backlash, as surely this would only apply on direction changes.
Thanks for any help regarding this,

Paul

sorry wrong thread
Hood

Can you do a test for backlash with your DTI. Move onto the  DTI until it has zeroed then go into the tab screen and set to Jog Step and set jog step to 1mm. Jog in the same direction as you moved and see if it moves exactly 1mm per step jog. Then jog back the way and see if it returns exactly 1mm per step.
Hood

Well, firstly thanks for replying Hood. I have just got in from the workshop and realised while I was  trying to go through everything logically that whilst entering the tool data into V carve pro , I was actually entering the size incorrectly when running the toolpaths for different shapes to test DOH!!!!
This in turn led to further adjustments...... and basically after 4-5 hours of stress ended up where I started only now entering the correct data.
So Lesson for the day , dont do work when you have been up since 4am, and secondly before deciding that your machine has major issues it could well be yourself 
Thanks again Mr Hood for taking the time, much appreciated 
Paul

Glad you got it sorted
Hood