I hope somebody on here can help me, cause I'm pulling my hair out here...
I have a CNC router, bought from somebody in LA, who since appears to have stopped business. I certainly would not say his CNC routers were the best quality, but it's been doing what I need just fine for the most part. For all intents and purposes, it should be considered homemade, and not professional quality. Lately though, it's been acting up.
About the machine - it's a 4x8, with a steel welded frame. Its X, Y and Z rails are as below:
Here is a link to the actual bearings: https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
Its rack and pinion X and Y, with a horrendous acme Z axis setup (soon to be replaced).
I have no limit switches - only hard stops. I jog it against the hard stops to square it every time I turn it on.
Running on Mach3.
Right now, as it moves along any of its axis, it will make a sudden and violent jerk, and then keep on going. It gets slightly out of place each time it jerks, and makes horrendous cuts. It appears to do it on the Z axis as well, although it's harder to see, being on an acme screw, and with less movement. It does it on long straight cuts, and also in the middle of curves. When I jog it around with the arrow keys, I cannot make it jerk. Only when its running from gcode. Also, maybe related, maybe not, when I jog it around, sometimes it seems like there's a delay from when I let off the key, until it starts to decelerate. This makes it a real pain to zero it out in a very specific spot, and sometimes when I go to jog it against its stops to square it it runs into them for a few seconds instead of just gently tapping them.
It started doing all this out of nowhere a couple of weeks ago. A month or two back I ran a 70 sheet job through it, and never had it lose its place or act up once. I didn't change a thing, and it is now acting up.
So far, I've tried the following:
First, I read up on proper grounding and shielding cables. My cables all have the foil shielding, and I took all the dump wires, and grounded them to the ground of my power supply, which is the ground going back to the wall. The other end is ungrounded. I also took the router power out of the cable trains, and ran it along the dust collector hose, so that it cannot contribute any noise into the other wires. I ran a grounding wire down the dust collection tube, and grounded it on both ends to try to counter static. But, the machine jerks even with the dust collector off.
I pulled the motors away from their respective racks, and under no load they all appear to turn fine. I can run the gantry or carriage back and forth by hand, with no binding whatsoever. But, just to be sure, I replaced all the bearings. Still no change.
I checked the backlash between the rack and pinions - my setup doesn't have a spring tensioner - you just have to set them by hand and lock them in place. I tried having them tighter or looser, with no luck. I tried brushing out the racks with a brass brush, and lubricating the racks, pinions, and rails with a dry teflon lubricant - no change.
I replaced the parallel port cable - no change.
I replaced the keyboard with a brand new one - no change.
I've tried messing with the velocity and acceleration. Everything from painfully slow, to fast (for me fast is 500 ipm).
Argh - at this point I'm about to start replacing the motors, drivers, and breakout board. I don't know what else to do. I'd rather not spend all that cash, but I need to get the machine going again.
Any suggestions? I'll try to get a video if I can...
Will