[boatlover]

I have a prolight 3000 CNC lathe and last summer I rewired it with new motors, stepper drives and a breakout board. Everything seems to be running fine, but I'm having issues keeping the lathe accurate. Today I was making four of the same part and the first two came out perfect and the third one was under sized by a few thousands. Later on I had the same issues and the machine cut .005 too much off three part right in a row even though I checked the X axis setting in the middle of the three parts and it was dead on .

The lathe has some really nice ball screws and I can't see any back lash in the axises when checking it with a 1" dial indicator. I can run it back and forth and the needle keeps reading 0. The stepper motors are very powerful and I can't stop the travels no matter how hard I push on the so I can't see the machine skipping steps. I'm also only taking .025 to .030 off per pass on aluminum so I'm not pushing the machine too hard. I had some issues setting up the steps per inch at first but I think I have them set correctly now. It was hard to tell if they were perfect as I only had a Harbor Freight 1" dial indicator to follow the movements while testing. I have the x axis set at 2003 steps per inch and the Z axis set at 16,000 steps per inch which seems to be working right. I guess I don't get it as the ball screws should have the same pitch and the pulleys seem to be the same ratio on both axises so why would the steps per inch be so different?

Do you guys have any tips or suggestions as to why the machine is off once and a while? When I fist start up the lathe I take a test cut and use that measurement to set the x axis. Sometimes it stays good, but other times I have to re measure and set the axis as it gets off after a few cuts.

Thanks for the help!
Dale P.

[pippin88]

Did you change tools or remove the tool between parts?

[boatlover]

NEVERMIND! I found the problem!!! I realized that I was using a 1" micrometer to measure parts under an inch and they were spot on, but used a calipers to measure the larger parts and they were way off. I thought the lathe was getting off but it was just my calipers. I used my height gauge to re check the parts and they are just fine. Thankfully the only thing that needs fixing is the calipers : )

Thanks for the suggestions
Dale P.

[diyengineer]

Dale, I emailed you about your conversion.