Problem- Going off Path During Machining

[artiesag]

Hi let me start by saying I am new here. Hi everybody!!!!!!!
OK this is my situation, I have had a CNC Shark Pro {USB} for about a year now. I have been using it with its basic panel since I got it with absolutely no problems. But due to its limitations I switched to Mach3 for its control software. I finally got the software to operate my machine which took some doing. I carved a few simple plaques without a problem, so it seemed but what I stared noticing was it was running off from my original start point somewhere through the machining process. What I mean is by the time it was done its return to "0" point was off, and so was the project being created. Is this a common problem. It doesn't happen all the time so I thought it might be a bad G Code but I have used the same G Code and one time it would work and another it would not, that is why I summed it up to be Mach3.

my motor is set to 1600 SPI and acceleration is 16. Could this be part of the problem? My controller is a Ncpod.

[mcphill]

You are most likely losing steps be driving too fast, or accelerating too fast. Once steps are lost, there is no "recover" without rezeroing and starting over. This is one major downfall of an open-loop system of steppers vs. a closed loop servo system with encoders reporting actual position back to the controller.

[artiesag]

OK that is exactly what I thought it was, but I do know that it can work because when I switch back to the basic panel everything is fine. So now how can I find the exact setting I need to run my machine correctly with Mach3? And what are all the settings that need to be changed? This is where my lack of knowledge stops me in my tracks.

[mcphill]

There is no "one" setting. The feeds and speeds will change depending on the material being cut, the tool you are useing, depth of cut, stepover. There are many, many factors that come in to play. You have some learning to do, and there is no "right answer" to give you...

[artiesag]

This is the understanding that I don't have and that is, My basic panel runs the machine perfectly in all circumstances. I guess all the settings are by default with the program it comes with. All I need to find out is what settings are needed to run the machine correctly with Mach3. I think you are right about the acceleration setting being whats causing the problem. Mine is set to 16 if that is not correct I do not know what to set it to, to get the proper results.

[ger21]

You need to calculate it via trial and error. I'd start with it at 5-10. Or, you can drop it by 20-25% and try it, and keep dropping it until it's 100% reliable.

What is the velocity set at?

[artiesag]

Is the 5-10 referring to the acceleration ? And the "velocity" I have never heard of that setting. Where is it located? and when I find it what should it be?

By the way thank you very much for helping me!!!!!!!!!

Artie

[mcphill]

Have you read the manual on MACH3?

Like I said, we can't give you "the answer" you will need to experiment with a better understanding of what is going on and what potential tunes/tweaks can resolve it.

http://www.machsupport.com/documentation.php

[artiesag]

Hey dude "Hurray" it worked !!! It turned out to be the acceleration setting I brought it from 16 down to 10 and ran the same g-code that I previously had a problem with.
Its all good now and Time To Jam making new creations.

Thank You So Much For Your Help!!!!!!!

Artie

[mcphill]

Glad its working out. Hope you still take the time to go through the manual, there is a bunch of great information in there...

[ger21]

Even better than the manual is to watch the videos, at www.machsupport.com

And Velocity is right next to Acceleration in the motor tuning screen.