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Author Topic: Limits Activate when Spindle is Running ,, EMF ?  (Read 1806 times)

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Limits Activate when Spindle is Running ,, EMF ?
« on: April 20, 2013, 10:52:41 PM »
Hi All ,

This is my first post here and I hope this is the right forum section for this , I am just finishing on my first CNC Router/mill and going through the process of getting everything setup and I have been having trouble with what I suspect is EMF while the spindle is running , I have done a search and it appears to come up blank .

First , I wired all the limits to be NC but as soon as the spindle started limits would be active , and not able to reset . If the spindle ( 1.5Kw Chinese water Cooled VFD ) is not running then all axis moved and limits work as they should .

I then changed the the limit switches over to NO and the spindle does not affect movement , but when a limit is hit it is not able to be reset until the spindle stops .

just wondering if any one else has had the same trouble or knows of a previous thread ,

Offline Tweakie.CNC

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Re: Limits Activate when Spindle is Running ,, EMF ?
« Reply #1 on: April 21, 2013, 04:18:27 AM »
Hi PhillM,

Welcome to the forum.

The electrical noise produced by VFD’s can sometimes be difficult to control but here are a few suggestions…

All limit switch (and e-stop) wiring should be made with shielded cable and the shield only connected to GND at the controller end.
The cable connecting the VFD to the spindle should also be shielded.
It is good practice to have an EMI filter in line with the mains input to the VFD.
Try to keep the limit switch wiring distant from all the VFD wiring.
Treat GND and EARTH as being two separate circuits.
Check for and eliminate GND loops – It is best to have a star connection at the controller and take all GND connections to this one point only.
Check for and if possible eliminate EARTH loops.

There are many more potential noise elimination steps to follow but these are my initial thoughts.

Tweakie. 
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
Re: Limits Activate when Spindle is Running ,, EMF ?
« Reply #2 on: April 21, 2013, 04:40:00 AM »
Hi Tweakie,

Thanks for the tips , I had a feeling that shielded cables should be used , although I do not have the VFD earth and the 5v on the breakout tied . Trying to keep distance between the wiring is a bit hard in the cable carriers.
The whole CNC thing is new to me but I made the first DXF]drawing to Gcode and loaded it this afternoon and let it go , and I cant get the smile of the face .

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Re: Limits Activate when Spindle is Running ,, EMF ?
« Reply #3 on: April 21, 2013, 05:22:20 AM »
Excellent work Phill, you certainly deserve to be smiling.  8)

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.