Discovered my stepper motors needed calibration, so I have been getting them zeroed in per the thread on calibrating the steppers.
Ran a test carve afterwords and still was having issues - so I retested my calibration and it was off again. Re-calibrated again and still having dimensional issues. I re-re-tested the steps/mm today and it is dead nuts on in all 3 axis. test carve STILL is not accurate to my liking.
W correct steps/mm, tight belts, v-wheels, x&z stiffening mods I am consistently having X dimensions come out .025-.030in UNDERSIZE. Y dimensions are consistantly coming out .015 in UNDERSIZE. Circles are still not as round as I would like - and consistently coming out .030 UNDERSIZE.
I could understand things coming out OVERSIZE due to runout of the spindle or overall looseness but UNDERSIZE? I have no idea. my edges are all crisp, no shoulders or lost steps during test carves.
Anybody have thoughts on what could be the problem here?
Have you confirmed the actual diameter of your bit matches the diameter you think it is?
I have found that just because a bit it marked as .125 inch that does not always mean it is exactly .125. Especially if you are buying Chinese or off brand bits.
That may not be the entire problem since you are seeing different X and Y errors, but it may be a part of the error.
My bit is from inventables - mics out at .124in. Doesnt seem like it would be the cause of .030 undersize cuts.
Are you cutting on the line or inside the line or outside the line?
If circles are coming out non-round, you’re losing steps somewhere. My v-wheels are looser than I thought they should be, but that’s what it took for me to get good circles at all sizes.
Robert- I’ve been running your calibration carve when trying to run down the issues. Im consistently coming out with the circles being fat at the 130-830 position (NE-SW if you will). All my v-wheels are tight - (perhaps too tight?) belts are tight as a drum…I’ve done the x-axis stiffening mod, as well as the z-axis. My v-wheels are tight enough that the eccentric nut is starting to cut into the carriage and mar the surface. I have noticed that there is some play in the Y axis, with the power off - the X-Z axis & carriage has some play latitudinaly in the Y axis…think of instead of the carriage being always, and firmly oriented square to the Y axis like so |–|, (| = y maker slides, – = X&Z axis/carriage) it has some play and allows play like so ||, |/| (about 1/4-3/8 of an inch out of square to the Y)
Allen - for pocket cuts, there really isn’t an option between inside or outside the line - and they’re coming out undersize. (using V-carve for my own tests, and Easel for Robert’s calibration test - same results with both). Although - cutting inside the line for a profile cut, it seems to be closer in tolerances than outside the line.
I am running the X-controller - which from what I understand as long as you set the pots to the factory recommended setting of 2.8, you will have plenty of voltage - I cant imagine that I’m losing steps due to overwhelming the motors.
That is way too tight.
You only want your belts tight enough that they won’t slip when moving the machine by hand. If the belts are too tight it can cause motor binding and excessive current draw of the motor. Which can cause missed steps and the motors to get hot.
It’s not like a V belt where it has to be tight to wedge into the pulley, the belts have teeth.
Sounds like the belt may be too tight, along with the V-wheels. I have my v-wheels set so that I can easily spin them with two fingers, but one finger gets a little tougher.
Check out my belt tensioning video, I included a way to check belt tension with a 2x4, dowel, and gallon of water if you don’t have a good scale. X-Carve Maintenance/Troubleshooting Videos - Add Your Own!
Thanks for the info gents - I’ll try loosening the belts and v-wheels and see what shakes out.