Hello everyone, My name is Mike and I'll start off by telling you my situation.  When I was first hired to run this CNC router it didn't even run and I had no experience on one, just knew a bit about electronics and computers.  It was purchased off ebay from a company going out of business and came with incomplete software, etc.  Before I came along someone else got the machine almost to working condition but Mach3 would not move the machine.  It turned out the XML file and Mach 3 needed some minor tweaking and was achieved thanks to people like you on this forum.    Since then I also added a smoothstepper.  The person I had fix the XML file said there was a lot of extra junk code in the XML file and it would take weeks to take it all out and said the machine should run right but with thrown together software and a iffy XML file who knows. 

Since then the machine has carved hundreds of carvings but not without it's mistakes.  Most the time the problem will be the Y-axis lags and shifts the carving in the middle of a carving up or down.  After troubleshooting, just by looking at the machine it looked like one of the screws for the Y-axis was spinning faster than the other side.  But that was just to the naked eye.  After attempting another carving it did the same thing, bumped the carving up a half an inch.  I did some more troubleshooting and tried rotating one of the screws by hand, it would not turn one way but would VERY easily the other way untill it got ahead of the other screw, which showed that the machine was ahead/behind on one side and cocked at an angle.  I did measurements from the machine to the motors on both sides of the machine and the machine was ahead .25 inch on one side.  Seeing how days before this troubleshooting I cleaned and adjusted the whole machine so that it was straight, level, and all measurements were perfect, it seems to me one side/screw of the Y-axis is spinning faster/slower than the other. 

As far as what would cause this I could only guess...  I know it has been messing up a little more lately so could a motor be going out?  Any way to adjust and calibrate each particular motor using Mach 3?  Any help would be appreciated. 

Mike

Here is a picture of the machine:

I put tape on each Y-axis motor so they were both pointing up and then started a carving. By the middle of the carving one side had the tape pointing up and the other was pointing down.  By the end of the carving the one side almost caught back up with the other side as you can see in the pictures I provided.  So throughout a carving one side will gain a full thread ahead of the other on the screw.  Any thoughts?

So no suggestions? Id appreciate any thoughts.  If not I'm probably going to start by replacing the motors.

So throughout a carving one side will gain a full thread ahead of the other on the screw.  Any thoughts?

I meant that one side will gain a full revolution or so on the other side. Not thread.

Check that all mechanicals are tight, things such as couplings and mounts etc.
Check the stepper drives are set to the same microstepping, if it is adjustable.
Check the screws on either side are the same, ie one could be 5mm pitch and the other 0.200 inch pitch.
If yo also attach your xml I will check that to see if I can find an issue.

Hood

Hello Hood and thanks for the reply. It turns out it was the two nuts on the end of one of the y-axis screws. They were too tight on one side and was causing enough resistance to cause the problem. Have carved out multiple carving since and has been running like a champ. Glad that was it and wasn't anything electrical. Thanks, Mike.

Glad you are sorted
Hood