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Question #: 13749

Question: Having some repeatability issues on Y axis of the blackFoot CNC Router. doing motor tuning, but also notice the Y axis idler pulley doesn't stand up straight. Bearing seems good, just loose on the bolt. Do i try to shim between bearing to bolt or shim the sides to make it stay up straight?

Current Solution

First, make sure that the alignment of the roller chain is straight with respect to where the roller chains are affixed at the ends of the gantry. This is of chief importance as there will be a clicking sound if there is no alignment. Also, make sure the idler sprocket can move from side to side to auto-correct on alignment, unless you can fit nuts or shim washers on either side to maintain the perfect position with respect to the alignment of the chain.

The misalignment of the chain is most likely the reason the idler sprocket is slanted at an angle.

If you are having repeatibility issues, make sure the drive sprocket is very tight on the motor shaft, and that the set screw is tightened on the flat of the stepper motor shaft. This is the typical culprit if any of the axes are having repeatability problems. It is difficult to determine if the drive sprocket is loose. Make sure to push with a bit of force to determine this.

Additional Information:
ok, took the y axis apart. Checked the drive sprocket. it seems tight. Although I did not take it off and put it back on. Checked the chain alignment edge to edge using a straight edge along the y drive rail and no clicking. tightened the chain and seemed to have it now off the same distance to the other side of the Y. I lossened it back up but no noticeable change.
using Mach3 spindle not running, just a pointer bit in and feed rate 50ipm
9k line gcode it's off by about .1 to .14 (ran code 4 different times, once in opposite corner of table) 130k gcode it's off 1.3 to 1.5 (ran code 4 different times, once in opposite corner of table). Not sure what to do, using the using the mach3 motor tuning it seems really close, and it's always the Y. should I swap wiring on the x & y drivers to see if problem goes to X?

Additional Information:
You can give the swap a try. It would rule out a possible wiring/driver/motor issue. If that doesn't work, we will need to go email so we can see pics to get a clearer understanding of the issue.

Additional Information:
So, I couldn't swap X and Y as X has a big honkin' motor. So I swapped the Driver for Y and Z, ran the same 130k line gcode and Y was spot on, but now Z is off. it was only off by .01 but there wasn't as much Z movement as there was Y of course. To me this would point to the driver. What do you think?


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