Need Help!- Noise/Interference Problems - Advice needed!

[UKRobotics]

Hi All,

I am now nearing completion of my first cnc retrofit and have just finished tuning my rutex servo drives with the supplied PID tuning software. I have also done the tuning in mach3 and can move each axis by pressing the arrow keys on my keyboard.

HOWEVER, I seem to have a massive noise problem because as soon as I enable the limit/estop inputs in mach3, with the servo drives powered up I get random 'trips' every few seconds making the system unuseable.

I'm not really sure where to start in solving this one, so I was hoping some of you could give me some pointers to save me spending a lot of time/money fixing stuff that doesnt need to be fixed.

My servo drives are Rutex R2020's and the limit/estop inputs are connected through the DB15 input to the rutex motherboard. None of it is optoisolated. I'm not currently using any shielded cable (the original bridgeport wiring did not use shielded calbe either) but between the control box and the motors, wires are run through earthed flexible metal conduit. Where my limit switches are connected to the rutex motherboard db15 input I have 10nf caps between each switch input and ground. Should I have one accross the input and output of the switch as well? I currently have no spindle wired up so this is not VFD related noise.

Any help would be much aprechiated.

Regards,

Dom

**Edit** I should probably also add here that my braking resistors are in an earthed metal box and I have tried using the mach 3 input debounce option with no real improvement.

[PEU]

the encoders are USdigital by chance? I read a lot of bad things regarding noise about them

[Al_The_Man]

Here is some recent posts on the subject you may want to look over.
http://www.cnczone.com/forums/showthread.php?t=71923
http://www.cnczone.com/forums/showthread.php?t=79908
http://www.cnczone.com/forums/showth...t=56869&page=2
Al.

[UKRobotics]

Encoders are US Digital, E5 type.

Al, thanks for the links - some useful stuff there.


I sent a copy of this post to Tom at Rutex shortly after posting it here and he came up with an interesting explaination.

I do not like the Rutex Limit switch circuitry. I never advise users to use it with Mach3. Save yourself a lot of trouble and purchase a Pci second parallel port and interface your limit switches through it to Mach3. You will have nothing but grief trying to get Mach3 to work through the Rutex system because Rutex requires only normally open limit switches and Mach3 picks up noise on the lines and interprets it as a limit switch condition. I know of no way to completely stop this.

Considering I already have a second parrallel port and break out board in place It makes sense to try this first. If this solves my problems then I'll put it down to a design flaw in the rutex motherboard or drives and not worry myself too much about it. However if the problem remains the same then I will take a closer look at my grounding, shielding, suppression and cable placement. I'm sure there is room for improvement.

[BobWarfield]

FYI, here is a page where I keep a lot of tips on getting rid of noise in your CNC system:

http://www.cnccookbook.com/CCCNCNoise.html

Cheers,

BW

[UKRobotics]

Bob, thanks for the link I've printed that out for future reference. For a minute I saw the tin foil office and though it was just a piss take :P

Al, Reading your other posts; are you suggesting one should common all their digital grounds (0v) together but keep them separate from analouge ground (earth) or are you saying that all the digital grounds should be commoned together and connected to analoug ground?

[Al_The_Man]

I connect all mine to a central ground plate, together with the service ground conductor.
See the first link MikeF OP.
Your PC 5v logic is most likely already at the same earth ground potential as your 120/240vac supply anyway.
Bonding them at a central point avoids ground loops.
It depends on which method you select. (try) to isolate all or make all common.
Al.