MechMate CNC Router Forum

Go Back   MechMate CNC Router Forum > After Building the Beast - Operating , Troubleshooting and Maintenance > Troubleshooting
Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Reply
 
Thread Tools
  #1  
Old Tue 28 April 2009, 00:19
Barrie
Just call me: Baz
 
Darwen
United Kingdom
Creeping z-axis - a cable screen was grounded at both ends

Copied from elsewhere:

. . . . . we came to run a program to level the table bed and for some reason the Z axis seems to drop when the spindle motor is running. we put it in one position and started the spindle, you can hear the Z axis and it does move but very slowly, stop the spindle and its ok. do you think this could be pickup from the high frequency spindle motor?
I look forward to your reply.
Kind Regards
Barrie.
UK
Reply With Quote
  #2  
Old Tue 28 April 2009, 00:39
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
A creeping Z axis is unfortunately a common problem with CNC routers. In our case, and with many ShopBotters, it is caused by grounding problems. We solved it by running a thick wire ground from frame to frame, all the way back to the control box. See Grounding or Earthing

The spindle motor also needs its own ground/earth wire to run in a cable with its power wires.

Can you tell us more about your grounding/earthing?

Where is your VFD located? How close to everything else?

A photo inside your control box could help.
Reply With Quote
  #3  
Old Tue 28 April 2009, 13:04
Barrie
Just call me: Baz
 
Darwen
United Kingdom
Earthing / Z Axis Problem

Hi Gerald
Thanks again for the quick reply and the things to look for regarding earthing.
I checked all my earth connections and they are all fine, every earth point gives 0.5 Ohms back to the main earth. I still had the same problem so I wired the spindle motor direct (not going through the cable track, still yhe same I then disconected the screen from the motor (only 1 end connected) and the problem went away I checked the screen to earth with the motor running and had a reading of 36v ac which was being generated from the high frequency from the inverter, every time i touched this point to earth it caused problems to the Z axis. so I have not connected the screen but all the machine and motor are still earth via the main bonding.
Thanks again for your help. we have now leveled the full bed and run several deisigns all without problems.
Kind regards
Barrie
Reply With Quote
  #4  
Old Tue 28 April 2009, 15:57
jhiggins7
Just call me: John #26
 
Hebron, Ohio
United States of America
. . . . . . Tying only one end of the screen to ground is a STRONG recommendation of Mike Richards. I don't pretend to understand it, but given Mike's expertise, I certainly follow it.
. . . . . .
Reply With Quote
  #5  
Old Tue 28 April 2009, 23:08
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Thanks for the feedback Barrie and glad to hear that you are on your way again.
Reply With Quote
Reply

Register Options Profile Last 1 | 3 | 7 Days Search Today's Posts Mark Forums Read

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 14:10.


Powered by vBulletin® Version 3.8.3
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.