Problems Cutting Diagonals and Circles

[ase3558]

Hey guys, got a shopbot PRS 96x48 and Ive been having a bunch of problems with it. Whenever I try and cut circles or a diagonal cut the circle is not circular and the line will be wavy. Also, I tried to mill a half sphere and in the middle of doing the finishing pass the feed rate will slow down randomly and sometimes even stop and then go at normal rates again. I tried dropping the motors and putting them back because I thought it might be the pinion not engaging with gears on the rails but I am still having the problem.

https://drive.google.com/file/d/0B2F8hZQtbOXhdVppbF80dS1jRnVaenhqNTN0akZqTU9yVTBr/edit?usp=sharing

[steve_g]

Austin…
Did you check the pinion gears for looseness on the shafts? That’s what it looks like… with power on, shake the gantry to check for movement, same with the y car… while you’re at it, push pull the Z too!
Let us know what you find…
SG

[ase3558]

The gantry has alittle play to it, but just alittle. I cant really feel that much on the y car. Ill try dropping all the motors and tightening the screws.

[steve_g]

Austin...
Just for grins, pull the set screws and be sure there's not a second one below... a common locking method.
SG

[jerry_stanek]

When you have the motors dropped check to see if both run. I have had that problem when one of my X cables came unplugged

[ase3558]

I dropped all the motors and on the last one the grub screw was so loose it was almost falling out. I tightened it down and just did a test using a Vbit. Think its as good as its gonna get. What do yall think, still a little out?

https://drive.google.com/file/d/0B2F8hZQtbOXhcmJyZGlaa0JQT2M/edit?usp=sharing

[steve_g]

Austin…
Well you certainly got it back to making usable parts! I can’t really tell if it’s all out or not. You shouldn’t be able to feel any slop when doing the “shake” test. With a friends PRS it took both of us to get the pinions and rack fully engaged… That would be the next thing if you still feel any movement.
SG

[ase3558]

Ok! So you mean when I drop the motors I need someone to lift it up when I am tightening to make sure its fully engaged?

[steve_g]

Yes… That’s what it took for us to get his right!
SG

[ase3558]

Ok! Ill try that! Thanks for all the help Steve! It was driving me crazy!

[steve_g]

Austin…
We’re close enough that we need to do lunch sometime!
PM me if that works for you!
SG

[pappybaynes]

Ok! Ill try that! Thanks for all the help Steve! It was driving me crazy! The circles do not look true...you may have a bad driver...I experienced all you have been experiencing, loose set screws etc, but had an "X" motor not running due to a bad driver - the machine cut squares just fine, but circles not so much. If both X motors worked then it's not the driver - with the control box turned on and motors in place I had definite slop on one side of the carriage and none on the other. Dick