544,187 active members*
2,773 visitors online*
Register for free
Login
IndustryArena Forum > CNC Electronics > Spindles / VFD > Still a bit unclear on proper spindle grounding
Page 1 of 2 12
Results 1 to 20 of 25
  1. #1
    Registered
    Join Date
    Nov 2017
    Posts
    573

    Still a bit unclear on proper spindle grounding

    So I have the common 2.2kw spindle and vfd. Plug has 4 wires, I figured out that pins 1 through 3 are for phases but pin 4 is connected to nothing inside the spindle, no ground. How do I do this properly? I have 4 conductor cable with braided sheathing. Should I just run the ground wire to a bolt on my spindle mount instead of the 4th pin? Or open up the top and ground it internally? Also what about the braided sheathing? Ground it at the spindle? Or at the vfd? Or both? Lots of conflicting info out there. What is proper?

  2. #2
    Registered
    Join Date
    Apr 2003
    Posts
    537

    Re: Still a bit unclear on proper spindle grounding

    My understanding is, ground the ground wire (the green wire) from VFD ground to the spindle housing or mount if there is not a dedicated ground connection at the spindle. The shielded cable braid should be grounded at only one end... grounded at the VFD, but don't attach it to anything at the spindle end.

  3. #3
    Registered
    Join Date
    Nov 2017
    Posts
    573
    Quote Originally Posted by coherent View Post
    My understanding is, ground the ground wire (the green wire) from VFD ground to the spindle housing or mount if there is not a dedicated ground connection at the spindle. The shielded cable braid should be grounded at only one end... grounded at the VFD, but don't attach it to anything at the spindle end.
    Yep, that's pretty much what I assumed. Thanks

  4. #4
    Member
    Join Date
    Jan 2005
    Posts
    12411

    Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by QuinnSjoblom View Post
    So I have the common 2.2kw spindle and vfd. Plug has 4 wires, I figured out that pins 1 through 3 are for phases but pin 4 is connected to nothing inside the spindle, no ground. How do I do this properly? I have 4 conductor cable with braided sheathing. Should I just run the ground wire to a bolt on my spindle mount instead of the 4th pin? Or open up the top and ground it internally? Also what about the braided sheathing? Ground it at the spindle? Or at the vfd? Or both? Lots of conflicting info out there. What is proper?
    Remove the top of the spindle is the correct way and connect the # 4 pin inside

    The Shield for a VFD to Spindle needs to be Grounded at each end, this is done by folding the shield back and clamping it in the plug cable restraint

    There is another way that I have been using, and that is to not use the plug at all and wire direct, using a Cable restraint Gland designed to be used for Shielded Cable, this is much better than using the Plug that come with these spindles
    Mactec54

  5. #5
    Member
    Join Date
    Jan 2005
    Posts
    12411

    Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by coherent View Post
    My understanding is, ground the ground wire (the green wire) from VFD ground to the spindle housing or mount if there is not a dedicated ground connection at the spindle. The shielded cable braid should be grounded at only one end... grounded at the VFD, but don't attach it to anything at the spindle end.
    The shield must be Grounded at both ends, at the VFD drive and at the Spindle
    Mactec54

  6. #6
    Registered
    Join Date
    Nov 2017
    Posts
    573
    Quote Originally Posted by mactec54 View Post
    Remove the top of the spindle is the correct way and connect the # 4 pin inside

    The Shield for a VFD to Spindle needs to be Grounded at each end, this is done by folding the shield back and clamping it in the plug cable restraint

    There is another way that I have been using, and that is to not use the plug at all and wire direct, using a Cable restraint Gland designed to be used for Shielded Cable, this is much better than using the Plug that come with these spindles
    I've heard from multiple sources that shielding is not supposed to be grounded at both ends for it to shield properly. Is this not true?

  7. #7
    Registered
    Join Date
    Mar 2017
    Posts
    823

    Re: Still a bit unclear on proper spindle grounding

    X2 on being confused.

    There is conflicting info out there. I saw one YouTube video with a vendor wiring a Chinese VFD to Chinese spindle and not connecting the ground pin at all. I have also seen diagrams showing a ground wire going from the spindle to seperate box labeled "ground" that didn't seem to be on the VFD or the spindle. I have also seen diagrams showing a wire going from VFD ground to spindle ground.

    This really shouldn't be confusing. There are 3 wires going from power outlet to VFD and either 3 or 4 going from VFD to spindle. It shouldn't be that hard to write clear instructions aimed at the hobby-level user (which is what Chinese VFDs are sold for), or label all the pins with useful titles instead of meaningless letters.

  8. #8
    Member
    Join Date
    Jan 2005
    Posts
    12411

    Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by QuinnSjoblom View Post
    I've heard from multiple sources that shielding is not supposed to be grounded at both ends for it to shield properly. Is this not true?
    Yes that is not true, they are misinformed, in a lot of counties it is a code requirement when using a VFD Drive
    Mactec54

  9. #9
    Community Moderator Al_The_Man's Avatar
    Join Date
    Dec 2003
    Posts
    23714

    Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by QuinnSjoblom View Post
    I've heard from multiple sources that shielding is not supposed to be grounded at both ends for it to shield properly. Is this not true?
    This occurred originally with the implementation of relatively low voltage control systems, CNC etc used in conjunction with high voltage machine/spindle control etc.
    The concern was that it could encourage ground loops to occur, inducing noise into low voltage cables, since then it has been a recommended practice to implement something called equi-potential bonding, this is ensuring that each part of the machine and motor frames have a earth conductor, preferably sourced from a Star point ground.
    This helps ensure that no difference in potential occurs in any part of the machine and allows earthing both ends of shielded cables.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  10. #10
    Member
    Join Date
    Jan 2005
    Posts
    12411

    Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by Goemon View Post
    X2 on being confused.

    There is conflicting info out there. I saw one YouTube video with a vendor wiring a Chinese VFD to Chinese spindle and not connecting the ground pin at all. I have also seen diagrams showing a ground wire going from the spindle to seperate box labeled "ground" that didn't seem to be on the VFD or the spindle. I have also seen diagrams showing a wire going from VFD ground to spindle ground.

    This really shouldn't be confusing. There are 3 wires going from power outlet to VFD and either 3 or 4 going from VFD to spindle. It shouldn't be that hard to write clear instructions aimed at the hobby-level user (which is what Chinese VFDs are sold for), or label all the pins with useful titles instead of meaningless letters.
    The Chinese are not going to write anything for you, they are only interested in selling what ever they can, good or bad, I'm not sure why there is no electrical code enforcement of the imports from China

    This is information in most cases, is a nightmare for Hobby users, that should not be doing high voltage wiring, before anyone writes this kind of information they should look up there Electrical Codes, or consult and industrial Electrician, 3ph power is not something you just mess with, unless you know for sure what you are doing, videos in most cases are very misleading, and unless they are done by a VFD Drive manufacture, (which there are some ) most all others have some miss information in them

    The only country in the world that uses 3ph motor without a Ground is China, this is the reason that you see all these low quality Spindles and AC motors coming from China with no Grounding Terminal, the 3 Pin Spindle Plugs and the none connected 4th Pin on the 4 Pin Plug Spindles all have to be corrected before they can be used


    Correct Shield termination and Ground is a must even at Hobby level

    Cable Shields terminated at one end provide only electrostatic protection against low-frequency, capacitive coupled interference and emission
    Mactec54

  11. #11
    Registered
    Join Date
    Nov 2017
    Posts
    573

    Re: Still a bit unclear on proper spindle grounding

    So if grounding both ends of the sheild, doesn't the 4th conductor in the cable as ground become redundant? Do you still want both the sheild and the wire grounded at both ends?

  12. #12
    Community Moderator ger21's Avatar
    Join Date
    Mar 2003
    Posts
    35470

    Re: Still a bit unclear on proper spindle grounding

    The shield is not a ground. It's the shields job to contain noise. The ground is there so you don't get killed.
    Gerry

    UCCNC 2017 Screenset
    http://www.thecncwoodworker.com/2017.html

    Mach3 2010 Screenset
    http://www.thecncwoodworker.com/2010.html

    JointCAM - CNC Dovetails & Box Joints
    http://www.g-forcecnc.com/jointcam.html

    (Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)

  13. #13
    Registered
    Join Date
    Mar 2017
    Posts
    823

    Post Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by mactec54 View Post
    The Chinese are not going to write anything for you, they are only interested in selling what ever they can, good or bad, I'm not sure why there is no electrical code enforcement of the imports from China

    This is information in most cases, is a nightmare for Hobby users, that should not be doing high voltage wiring, before anyone writes this kind of information they should look up there Electrical Codes, or consult and industrial Electrician, 3ph power is not something you just mess with, unless you know for sure what you are doing, videos in most cases are very misleading, and unless they are done by a VFD Drive manufacture, (which there are some ) most all others have some miss information in them

    The only country in the world that uses 3ph motor without a Ground is China, this is the reason that you see all these low quality Spindles and AC motors coming from China with no Grounding Terminal, the 3 Pin Spindle Plugs and the none connected 4th Pin on the 4 Pin Plug Spindles all have to be corrected before they can be used


    Correct Shield termination and Ground is a must even at Hobby level

    Cable Shields terminated at one end provide only electrostatic protection against low-frequency, capacitive coupled interference and emission

    Nobody wants to be wiring up high voltage spindles (or anything else) but until somebody comes up with a standard spindle to VFD cable (which they should), they have to if they want to build a CNC machine. It's not realistic to expect that all hobby level users and small shops will hire an industrial electrician to connect their spindle wires. I seriously doubt an industrial electrician would even accept the job. It's hard enough to get a residential electrician to do some wiring for a reasonable price.

    I have wired up a bunch of high voltage projects and some that are considerably more dangerous than CNC spindles (like CRT arcade monitors which hold lethal current even when unplugged). I am perfectly capable of following instructions and taking the suggested safety precautions. IMO, where it gets dangerous is when the instructions are wrong or misleading.

    This risk is worse for CNC wiring than anything else I have attempted because there are too many people offering conflicting bits of advice. We have no way of knowing who really understands this stuff vs people who are regurgitating innacurate info. Electricity is one area where I like to be 100% before flipping the switch.

    It doesn't need to be this hard. With clear, simple and accurate instructions, connecting wires to screw terminals is not a difficult job

  14. #14
    Member
    Join Date
    Jan 2005
    Posts
    12411

    Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by Goemon View Post
    Nobody wants to be wiring up high voltage spindles (or anything else) but until somebody comes up with a standard spindle to VFD cable (which they should), they have to if they want to build a CNC machine. It's not realistic to expect that all hobby level users and small shops will hire an industrial electrician to connect their spindle wires. I seriously doubt an industrial electrician would even accept the job. It's hard enough to get a residential electrician to do some wiring for a reasonable price.

    I have wired up a bunch of high voltage projects and some that are considerably more dangerous than CNC spindles (like CRT arcade monitors which hold lethal current even when unplugged). I am perfectly capable of following instructions and taking the suggested safety precautions. IMO, where it gets dangerous is when the instructions are wrong or misleading.

    This risk is worse for CNC wiring than anything else I have attempted because there are too many people offering conflicting bits of advice. We have no way of knowing who really understands this stuff vs people who are regurgitating innacurate info. Electricity is one area where I like to be 100% before flipping the switch.

    It doesn't need to be this hard. With clear, simple and accurate instructions, connecting wires to screw terminals is not a difficult job
    Just last week I was asked to setup / make some cables for VFD drives to Spindles, this is not very difficult to do, if you are uncomfortable in making a simple cable like this then do you think you should be building a machine like this

    You will see who's information is correct, by looking it up in the electrical code regulations, they are not easy to understand, still the best place to look to see if you are doing something you should not be doing also, any good professional Video that has been done by the company that manufactures the product, is another good place to look, most you should not look at, as they have many problems that are incorrect examples of wiring Etc, even the pro's don't normally do a 400Hz spindle, just think that a few years ago the Hobby user could not get or use anything other then a hand router
    Mactec54

  15. #15
    Community Moderator Al_The_Man's Avatar
    Join Date
    Dec 2003
    Posts
    23714

    Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by Goemon View Post
    Nobody wants to be wiring up high voltage spindles (or anything else) but until somebody comes up with a standard spindle to VFD cable (which they should),
    Back in the 80's when I started doing CNC retrofits, Mitsubishi, Fanuc etc, these systems all had integrated type spindles, except they were called spindle drives then, not VFD's.
    At that time though, VFD's started arriving on the scene for general 3ph induction motor control.There were no defined instructions or any special cable recommended for the VFD to motor.
    The cable manufacturers started getting in on the action and the first that I can remember to bring out a specialty cable was Belden.
    This is some of their products and instructions.
    I made my own.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  16. #16
    Quote Originally Posted by coherent View Post
    My understanding is, ground the ground wire (the green wire) from VFD ground to the spindle housing or mount if there is not a dedicated ground connection at the spindle. The shielded cable braid should be grounded at only one end... grounded at the VFD, but don't attach it to anything at the spindle end.
    Why would you not ground the wire in the braided shielding
    To the ground on the spindle side??? Please answer carefully because I really don't want to have to re-solder my aviation connector.

  17. #17
    Community Moderator Jim Dawson's Avatar
    Join Date
    Dec 2013
    Posts
    4884

    Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by ClintonCarawayCNC View Post
    Why would you not ground the wire in the braided shielding
    To the ground on the spindle side??? Please answer carefully because I really don't want to have to re-solder my aviation connector.

    Normally you would only ground the shield braid at one end to prevent ground loops. Most common connection is at the VFD end. You would connect the motor ground wire at both ends.
    Jim Dawson
    Sandy, Oregon, USA

  18. #18
    Member
    Join Date
    Jan 2005
    Posts
    12411

    Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by ClintonCarawayCNC View Post
    Why would you not ground the wire in the braided shielding
    To the ground on the spindle side??? Please answer carefully because I really don't want to have to re-solder my aviation connector.
    You should not be soldering the shield to anything

    A Ground Connection is not somewhere you connect a Shield too, So, Ground wires to there Ground Terminals only

    For the spindle Plug Shield, because these plugs are not EMI Shield Grounding plugs, you don't have any choice other than to fold the shield up and clamp it with the Cable restraint clamp no ideal but the only choice you have

    The Plug is Grounded through the Body of the Plug and this in turn will Ground the Shield
    Mactec54

  19. #19
    Member
    Join Date
    Jan 2005
    Posts
    12411

    Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by Jim Dawson View Post
    Normally you would only ground the shield braid at one end to prevent ground loops. Most common connection is at the VFD end. You would connect the motor ground wire at both ends.
    You should not answer questions like this if you don't know the correct way to install a shielded Cable for a VFD Drive

    All Shields must be Terminated at both ends, every VFD Drive Manufacture will tell you this, in some countries it is a Code Requirement

    You can not create a Ground Loop if everything if correctly Bonded

    Do you know what a Ground Loop is ???
    Mactec54

  20. #20
    Community Moderator Al_The_Man's Avatar
    Join Date
    Dec 2003
    Posts
    23714

    Re: Still a bit unclear on proper spindle grounding

    Quote Originally Posted by mactec54 View Post
    You should not answer questions like this if you don't know the correct way to install a shielded Cable for a VFD Drive
    Do you know what a Ground Loop is ???
    Jeez Jim, what were you thinking!:nono::
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

Page 1 of 2 12

Similar Threads

  1. Replies: 3
    Last Post: 03-15-2017, 07:47 PM
  2. Grounding a 2.2kw VFD spindle
    By DDMODS in forum Spindles / VFD
    Replies: 6
    Last Post: 07-21-2016, 11:28 AM
  3. Help!!! Touch probe grounding through spindle???
    By Momentz in forum DIY CNC Router Table Machines
    Replies: 1
    Last Post: 11-28-2014, 10:21 PM
  4. Grounding router spindle?
    By Mogal in forum DIY CNC Router Table Machines
    Replies: 15
    Last Post: 10-15-2014, 07:17 AM
  5. Proper grounding
    By monte55 in forum Xylotex
    Replies: 13
    Last Post: 12-05-2006, 08:09 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •