so, I bought my cnc knowing I'd end up here at the school of hard learning... fully admit it was a terrible idea to be a newbie and get this machine.

at this point... I've done 6 or 7 little projects to test my machine... all went fine... and then started on a big project - a guitar.
things were going just fine... setup mounting holes, planed the top and back, cut the body outline, cut my control holes... then it came to cutting a neck pocket. it is at this point that I hit a wall.

over the last few days this is what I've learned... my machine cannot accurately cut things with a gradual taper.
Cut the body shape fine with no dreaded "steps" so it seems like the hardware is functioning fine and lots of big curves there. I would think I would have seen issues emerge over the run but I didn't.

For the neck pocket - I started with a typical spiral toolpath... and this ended up 1/2" off after two passes.
then, I ran my pickup cavity (just a box) and it is perfectly centered and lovely. so... what's the difference? well, I guess it's the taper on the neck pocket. seems like the gradual shift in x over the y length... it actually loses where x is and if I go back to my 'x' marked on the stock... we're off. when I cut anything square - we go back to x and we're fine. this makes me think I must be losing steps.

I've slowed my feed from 100 to 85 to 70 to 40 and doesn't seem to improve. again, it is ONLY the neck pocket. anything else I do ends up centered and no steps.



the machine specifics - well I don't know much but I do know it's all ball screws, and it's the red usb board. 4 axis 1.5kw spindle with extended z access. I have it running on a win 7 32bit laptop with nothing else and no inet connection. Full mach3 license. I've set the machine up with the config file that I got from the vendor for mach3.



so... is this the 'missing steps' I hear so much about? Is this more likely an issue with the coupling between the motors and the ball screws? any info appreciated... threads you can point me to, advice on next steps... shoulder to cry on... whatever you have.