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Discussion Starter · #1 ·
Hello all,

Newbie CNC'r here, so feel free to criticize!

I have a Foxalien 4040XE with Dewalt 611. I've noticed a few times now during my profile cut (usually circles), all of a sudden it jumps off the toolpath and carves into the finished work (picture attached). This has happened now with both a 1/4" UC and DC bit, as well as an 1/8" UC. It seems to occur on either each side of the circle (closest to the y axis rails). I've tried slowing down feedrate and decreasing doc, all with convention cutting. The picture is from a 1/4" DC at 35ipm, 0.12" doc, conventional cut in pine.

Some additional info:
  • No problems with losing steps during pocket or engraving cuts - returns to zero nearly perfect every time
  • Running Candle GRBL control via laptop. I switched to running via offline controller, so the laptop is out of the picture, and have completed some profile cuts successfully with an 1/8" UC, coincidence??
  • All belts are at 5lb/in
  • All screws/collars are tight. Top backlash washer on the z-axis was slightly loose during the picture shown, not sure if that is the root cause?
  • Doesn't seem to fail on the first pass
  • Workpiece is held with the CA glue/tape method as well as clamps (it does not move)
  • Spindle/router is not perfectly perpendicular to the wasteboard - seems to have about a 1/32" tilt in the y-direction

Ideas on what could be causing this? Any feedback is appreciated.
 

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David - Machinist in wood
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Looks like you're losing steps. Set your Z height a couple of inches above the workpiece or spoilboard and run it in the air. See if it happens with the router off and not cutting. You could also try it at a different location on your machine and see if it's that particular location giving you the issues.
 

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I agree with David, losing steps. things to check:
  • check the stepper driver current settings. could be too low
  • check to see if there are any obstructions on your rails
  • check to see if the drivers are overheating
  • could be your feed rates (in your gcode, check your CAM SW). cut them back.
  • acceleration too high?
  • too deep a cut?
  • check to make sure your belts have correct tension and aren't worn.
That is not a terribly rigid machine so you should avoid pushing it hard. Don't go so fast or deep.
 

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Discussion Starter · #4 ·
I agree with David, losing steps. things to check:
  • check the stepper driver current settings. could be too low
  • check to see if there are any obstructions on your rails
  • check to see if the drivers are overheating
  • could be your feed rates (in your gcode, check your CAM SW). cut them back.
  • acceleration too high?
  • too deep a cut?
  • check to make sure your belts have correct tension and aren't worn.
That is not a terribly rigid machine so you should avoid pushing it hard. Don't go so fast or deep.
Thanks guys! I will check the recommended things and report back.
 

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Thanks guys! I will check the recommended things and report back.
No problem.

FWIW, looking at the gouge that happened, it looks like one axis started losing a lot of steps all of a sudden. I suspect the drivers are overheating. The control box looks like it doesn't have a fan. try running the machine with the cover off the control box. If you have an IR thermometer check the drivers (they should have little heat sinks on them). You could use your finger but be careful of burning it. If it doesn't fail with the lid off but the drivers get hot then you probably need to figure out a way to get forced air in the box. I'd cut a hole in the lid and slap a fan on it.
 

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Discussion Starter · #7 ·
Hey guys, thanks again for the feedback. Just a follow up.. my issue could have been a number of things but I now have more airflow going to the controller and slowed down feedrates/doc and did not experience the issue again. I suspect 90% of my problem was me trying to be too aggressive with the cut.. live and learn!
 
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