uPVC CNC Corner Cleaner

Hi all

I hope I'm posting in the correct place.

I have a company that manufactures windows and doors from uPVC profile. The production system is quite simple; cutting, welding, cleaning, beading and hanging. The profile we use is a sculptured system that is quite complex to clean off after welding and there are approx 13 different recipes.

The machine that does this job is a CNC corner cleaner, specifically this : EV470/300

This gives an idea of what it does (not the same machine):
CN-772 Fully Automatic CNC Corner Cleaning Machine ( 4 axes, 4 servo motors ) - YouTube



The machine is quite simple, it's two axis, X and Y, X being horizontal and Y vertical. All the system is Mitsubishi. The problem; about 18 months a go the Y axis started dropping and damaging frames. What we found was the the encoder for some reason is sending false pulses to the amplifier. The strange thing is this doesn't happen all the time. We have changed the amplifier, encoder cable and motor/encoder. We have everything wired as per Mitsubishi, we have mains filters etc. I'm pretty sure it is airborne RFI or similar as when the encoder cable is run externally away from the chassis.

Equipment on the Y Axis:

Servo Amplifier - Mitsubishi MR-J2S-70A
Servo Motor - Mitsubishi HC-KF73B

If anyone can help please do.

The fact you say it's fine when you move the cable away from the chassis, sounds like a grounding issue.

Are all the earth straps/wiring in good condition?
The first thing I'd do, is go around the chassis and check for any earth wires that are missing (look for remains of connectors underneath bolts/screws with nothing connected) or damaged wires. Any wires you do find, unbolt/screw them and check they're making good contact with the frame.
Check that the main earth wire in is good.

It migt talso be worth checking with a multimeter, that all the major metal parts have a good connection to the main earth terminal. You should see less than a few ohms resistance, anything higher and I'd be looking to find out why.

Everything M_C said with addition to go over every wire and connection with a fine tooth comb has chances are this is something simple like a loose connection or switch going down sending out noise.
Obvious but Check no high voltage cables run along side signal cables.

One last thing.!! . . . Have you changed any other equipment close by the machine that may be interfering.? I ounce had a compressor in the next room separated by concrete block wall affecting my machine when coming on.!! . . . . took me months to realise only happened when compressor fired up because it didn't always happen.! . . . Nightmare stuff.!!!