Hello All

First thank you for your help....Every time i have a question you answer it and i am up and running.

So now i am scratching my head.

I am running my CNC Router with Artcam Express and Mach 3. They work well together.
The other day i was running a g-code for the first time it was going really good, and all of a sudden it starts cutting too deep. It was like the "Z" lost track of its position. I hit the E-stop.
At this point i just flipped the board over,  reloaded the same g-code and it ran just fine. A perfect cut. Can you explain this?

Thanks in advance

John

Most likely one of two reasons, first is the cutter getting pulled out of the collet with the cutting forces. Second is you are loosing steps on a Z+ rapid move and thus as it does not go up as far as Mach has instructed, and thinks it is,  it will go lower on the next Z move down.

For the first option you will need to make sure the collet is tight enough, for the second you need to detune your motors a bit, ie reduce accel and/or velocity
Hood

Thank you Hood,
 I know it was a while since my original post but i haven't been running my machine lately.
Well i am sure my collet is tight and the bit is not moving. So i have adjusted the accel and the velocity. Accel from 20ipm to 10ipm  and the velocity from 5ips to 2.5 ips. This has not cured my problem. This is baffling me because it doesn't always loose track of where Z is. Sometimes it runs the job fine and then other times it just starts cutting too deep at any point in the job. I have no problems with X or Y. So at this point i am 6 out of 10 jobs that went bad.

any help would be appreciated.

thank you
John

Hi John,
 Till Hood gets back to ya, ya might verify that there is no binding or excessive load on the Z mechanism.
Set the jog rate to 100%, (or hold the SHIFT key) and jog the Z up and down several times to make sure it doesn't miss any steps.
You might just be at the borderline of missing steps, even though you've reduced the settings.

Regards,
Russ