Hello, I'm new to the forum. I have spent the past year and a half building my own CNC mill that runs on LinuxCNC, and it is mostly done now. Except that I can't get it to finish a program because it keeps thinking that the limit switches have been triggered even though they haven't.
I built this mill from scratch. It is made entirely of aluminum plate and extrusions. It has NEMA23 closed loop steppers, SFU1204 ballscrews, HGH20CA linear rails, a 2.2kw 220v 3 phase spindle and 2.2kw VFD, a "5 axis" parallel port breakout board, a Dell OptiPlex 990 with a parallel port card and running LinuxCNC (obviously). For limit/home switches I have it set up to where one limit switch doubles as a home switch, and all six switches are normally closed and in series all going to one input pin. The limit switches are generic micro switches, and the limit/home switches are Metrol CS067B. I have 24V running through the switches, so I'm using a 24v to 5v optocoupler board to bring the signal down to 5v for the breakout board. The Metrol switch wires are not shielded, but because they cost $67 a piece, I don't want to mess with that. The wires for the other switches are shielded.
This is what happens when I try to run a program: I home the machine, import the program into Axis, hit run, and it could be 1, 5, or 60 seconds later that it suddenly stops the machine because a limit switch was supposedly hit. It doesn't seem to happen consistently. I originally had the VFD next to the other electronics in a copper mesh cage, but ended up making a sheet metal box for it and moving it away (and took the spindle cable out of the cable chain that also held other wires). I thought that would prevent any EMI from interfering with the other electronics. But that didn't fix it. I have narrowed it down to an issue between the spindle/VFD and the breakout board. I can run a program perfectly fine with everything on except for the spindle/VFD, so it can't be the steppers or drivers. I have tried running 24v directly to the optocoupler board, bypassing the switches, but it still triggers. I have tried completely bypassing the limit switch circuit by jumping the input pin on the breakout board to ground, and it still triggers. I have spent hours researching this, and I have tried almost everything. I have my VFD in a Faraday cage. I'm using a shielded spindle cable with the shielding grounded at both ends. I have the signal wires shielded and grounded. I don't know what I'm doing wrong.
I have spent weeks trying to diagnose this, and now I am only more confused. Part of the problem is that I'm only 18 and I'm not an electrical engineer (I'm not even a mechanical engineer yet!), and I'm learning a lot of this for the first time. I have run out of things to try, and I would really appreciate any help I can get. Thank you in advance!
