Servo's and noise suggestions

[ty1295]

I have 3 DC servo's with TTL compatiable encoders and 12 ft wires from US Digital

Wire is shielded, hooked to rutex drives per their manual. Wires run seperate from main drive wires and in it's own plastic conduit. 1 end of shield is grounded.

Machine is working great with Mach1, Mach2 is jerky.

What is interesting, is this weekend I used my plasma cutter (plan to CNC it later), went back to mill, nothing would work right, lost steps, etc.

Fought with it for 2-3hours changing EVERYTHING. Finally noticed plasma was on (not being used but powered up), turned it off and mill worked perfect again. An interesting note, is when I had issue using Rutex tuning software, if I tapped on mill with hammer you could watch encoder counts.

Plasma is on different breaker than mill but obviously on same panel.

So I have concluded I still have noise into my encoders with my best efforts, and possibly is reason Mach2 isn't working for me yet.

What more can I do to help?

My only thought was, currently my drive power supply is in the same cabinet, thinking of moving it out.

Anybody else have machines this sensitive to noise?

And how am I going to control it with the plasma cutter when I go to CNC it. (Hypertherm)

Jeff

[Al_The_Man]

What I consider very important to reduce the problem of noise etc is to make sure that every thing is grounded, including the commons of all power supplies. I always set up a large copper plate to terminate all grounds and shields to a common point which in turn goes to a the main ground conductor. this is especially important when you CNC the plasma, where It is a good idea to ground the plasma table to the plasma common and sink a ground rod if possible. If you use a 120vac or 240vac step-down/isolation transformer for the AC control make sure you set up a neutral by grounding one side of the secondary at the transformer. If you have a PC based system, make sure the power supply DC common goes to the same ground point, on all the retro-fits I where I have followed this method I have not had a problem with noise.
Al

[ESjaavik]

Are you sure your encoders have proper line drivers and not just a TTL interface?
The first are made for sending the signals over a long(ish) cable, the second is meant to be connected directly to the electronics.
Don't be confused by "TTL level signals" they can still be generated by line drivers. That term does not actually say anything about the drive capabilities and suitability over wire connections.

If using unbuffered TTL it may give the symptoms you describe. It works as long as the environment is near perfect, but will get disturbed, even physically destroyed by noise, improper grounding etc.

Ground loops are especially pesky. Check that motor, encoder and electronics are properly grounded to a good ground point using separate wires. And ONLY through these wires. For example grounding the encoder to the motor can upset the encoder signal so the drive gets totally confused.

[NHughes]

What type of drive are you using, belt, screw, rack? What speed are you running, how heavy is the table/gantry you are moving? Can you move the machine by hand? Is the Machine bolted to the floor? Is the plasma circuit seperate from the machine? Do you have any other wires running along side of the servo cables? How are your motors mechanically isolated from the machine?