Sounds like a grounding and/or bonding issue, ensure the frame of the motor as well as any moving parts of the machine are suitably earth grounded.
What type of spindle, VFD? DC motor etc?
Al.
Our school has an old Emco F1 CNC Mill that Studica has supported from time to time. The mill is old, and temperamental but works fine. Recently the mill has been "hiccuping" a fair bit while runing a program. The machine has never acted in this way before.
I noticed that the stepper motors were clicking and the over ride clutches were engaging as the program was being run. This causes the machine to lose position and causes the program to appear to run. In the past it was an issue with the gibs, slides, lubrication to the ball screws ect.
I have checked that the slides, gibs and ball screws are clean properly adjusted, and lubricated. With the stepper motors disconnected, everything moves smoothly. Same when the stepper motors are connected and everything is moved under power.
The problem(s) starts when I turn on the spindle and run a program. This is when the stepper motors start clicking and the machine loses position. I have tried to run the program with the spindle off and the program runs fine. All 3 axis's move smoothly, and none of the above issues happen. At the same time there is no noticeable difference in the sound of the spindle motor as this happens.
Mechanically the machine runs fine. As described above the slides, gibs and ball screws are properly cleaned adjusted and lubricated. What should I be looking for? What have I overlooked? Would this be a power supply/electronics issue?
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Sounds like a grounding and/or bonding issue, ensure the frame of the motor as well as any moving parts of the machine are suitably earth grounded.
What type of spindle, VFD? DC motor etc?
Al.
CNC, Mechatronics Integration and Custom Machine Design
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
From what I can see on the label, it is a 95V 5.6 A DC motor. All of the connections look fine. Is there anything else I should be looking for?
As Al has said it could be a Grounding problem, or Noise, How are the brushes in the DC motor, may be time for a good clean, these machines have no shielded cables, so there are lots of Noise possibilities, Twist any of the wire pairs where ever you can, this may help a little
Mactec54
I have given the spindle motor a good cleaning, including polishing the armature. I have checked a large number of wire connections-especially the grounds, and they were all tight. I'm thinking of wrapping some aluminum tape around the z-drive wires, as the spindle power supply is right on top of it. I think it may help with some shielding. What else should I be looking at?
Those steppers have to be 20 or more years old. They are known to run hot.
Do they have a finite service life?
The machine was refurbished several years ago, and the steppers were replaced with Powermax 2 steppers. So far the steppers have been working fine, as is the mechanical components.
After cleaning the motor, polishing the armature, checking connections, and covering the spindle wires with aluminum foil, the machine seems to be working OK. I have not experienced any of the hiccups described, other than a limit switch being tripped when the machine was no where near any switch. As usual this caused the machine to completely forget where it was and run ramdomly when I tried to continue running the program.
What control /software are you using to run your machine, if you are using Mach3 then you can increase the Debounce this will help with limit switch false tripping, but does seem that you still have a noise problem, which is most likely from the stepper motor wiring, limit switch wiring also needs to be shielded, and the shield grounded at the source a saddle or a tight fitting spring clip around the shield,fastened to clean metal contact
Some EMC shield clamps, these are from icotek
Mactec54
Thanks for the info.. I'm currently running Mach 3 on a dedicated Windows XP computer. Currently there does not appear to be any shielded cables in the wiring. Another person suggested to look at the low voltage power supply for the PMDX interface board. it may be at issue as well.
What is the debounce set at?? ( Look in General Config )
Not likely to be a low voltage problem, Unless the Grounding has be done incorrectly
what you have is a noise problem,It sounds like your cables are the normal that Emco used for their system, they knew what they were doing when they wired these machines, when someone changes the wiring without knowledge of what they are doing, ( Most retrofits ) you will have problems like this
Mactec54
Thanks for the info. Currently the Debounce Interval and Index Debounce are both set at 0. What do you suggest I set those numbers at?
Mactec54
Thanks for the advice. I will play with the settings and keeps tabs on how the machine behaves.
Interestingly enough, for the past few project runs, the machine "behaved" before any adjustments were made. I will put the low values in to ensure no glitches happen, or are minimized.