Need Help! Serious noise issues

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Thread: Serious noise issues

  1. #1
    Registered Mike F's Avatar
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    Default Serious noise issues

    Hi all,

    I posted this message on my build log here and Gerry (ger21) suggested I post it here also.

    I recently bought a 3HP water cooled spindle and a matching VFD from here. It took some time but I managed to track down some proper, three core, shielded, control cable with 4 sq mm cross section conductors. 6 metres cost me £52 GBP!!! - expensive stuff but they sent me 8 metres. At 13mm diameter, this stuff is not easy to work with and my first problem was to try and solder the cable to the connector when the solder buckets were too small for the size of conductor. Eventually managed that OK, wire up the input cable, put in a temporary, gravity feed water tank and ventured to try the spindle.

    First attempt was not good but after a couple of questions to the seller, to get some of the program data, all things looked good. The spindle whispers up to 24000rpm and there is absolutely no vibration whatsoever. I am truly impressed with this motor.

    Next thing to try was to run the machine at the same time as the spindle and this is where I ran into massive problems. On start up of the spindle, the machine motors vibrate like mad and start to take off. This also happens as the motor runs down, just before it stops. The scary thing is that this also happens when the Gecko drives are in the fault condition and no computer attached. I did not think it was possible for this to happen as I have a charge pump attached to the controller. On careful inspection, the relay on the charge pump switches on and off rapidly of its own accord during run up and run down of the spindle.

    The plug for both the controller and VFD share a dual socket in the workshop and the workshop has two ring mains. Removing the VFD plug and plugging it into another socket, at the other end of the workshop and on a different ring, improved matters but there was still some interference.

    An electronics friend of mine tried a couple of filters on both the VFD input and controller input but these made little difference also. He concluded that the noise was travelling down the ground lines and basically, getting everywhere on the mains circuitry.

    Before anyone asks, all my cables and wires to the servos, encoders and limit/home switches are shielded. The shielding on the spindle cable is also the ground.

    I am hoping that someone, looking in, can shed some light on this problem and offer a solution as I am sure I am not the only one who has had this problem.

    Cheers,

    Mike

    Similar Threads:
    Attached Thumbnails Attached Thumbnails Serious noise issues-spindle-z-1r-jpg   Serious noise issues-spindle-z-2r-jpg   Serious noise issues-spindle-z-3r-jpg   Serious noise issues-vfd-r-jpg  



  2. #2
    Community Moderator Al_The_Man's Avatar
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    Are you following good grounding practice, i.e. service ground and any machine grounds to a star point and all metal parts of the the machine and spindle frame with ground conductor?
    Are you running isolated power supplies?
    Do you have a DeskTop PC or laptop?
    If DT. PC. how and what manner of grounds are connected to the PC power supply?
    Personally I prefer to make an absolute common ground connection of ALL power supplies etc to the common ground point. i.e. nothing is isolated.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

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


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    Registered Mike F's Avatar
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    I'm sorry Al but I am extremely electrically challenged. It is one of those areas that just passed me by during my informative years and try as I may, I just cannot get the hang of it. What I am sure of is that yours is good advice if only I could understand it I get confused between the terms 'ground' and 'earth' - I am told they are different but don't know why. As to 'star points' and 'isolated power supplies' - not a clue.

    If you were to tell me to connect A to B, C to D etc. I would have no problem.

    The computer is a PC running Mach3 only. As to the PC's ground, this is simply through the 3 pin mains connection here in the UK.

    I think the best bet would be for me to get my electronics friend to look over your reply and then I can reply to you in a more informative manner.

    Thinks? - maybe I should have made a clockwork machine

    With your perseverance and some help from my friend, I am sure this is doable - after all, there must be many hundreds of these devices running successfully all over the place. Just off to do some research on star points and isolated power supplies.

    Thanks,

    Mike



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    Community Moderator Al_The_Man's Avatar
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    Mike, I have installed many a PC based system in pretty harsh industrial environments over the years and have worked with a certain philosophy as to grounding etc. and common'ing supplies and have had no problems so far.
    Every week I see at least one post or another here mentioning spurious tripping of limit inputs etc, I would like to wager that the majority is caused because of an haphazard approach to grounding.
    Earth and ground is synonymous to me, Earth is commonly used in UK and ground in N.A. which should refer to a conductor that is actually at ground potential.
    One of my pet beefs ( of many ) is the use of the term Ground, especially by vendors of Drives and BOB units that refer to terminals as ground when they are actually common, or power supply common etc.
    Which in eventuality may or may not be grounded.
    Here is one link as a reference http://www.a-m-c.com/download/docume.../instnotes.pdf
    Rant over.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

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


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    Registered Mike F's Avatar
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    Al, you can rant all you like because I actually understood some of that.

    I don't know if you have seen my build log or know how it has been built but the Y and Z axes are actually completely isolated from the X axis and even on the X axis, the ballscrew is not electrically connected to the X rails and frame. Do I need to electrically connect all these metal parts whether they have motors, encoders attached or not?

    Mike

    Incidentally I have been looking at EMI filters and line reactors - are these necessary? Those line reactors are sure expensive.

    Last edited by Mike F; 01-20-2009 at 05:07 PM. Reason: More info


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    Community Moderator Al_The_Man's Avatar
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    Quote Originally Posted by Mike F View Post
    Do I need to electrically connect all these metal parts whether they have motors, encoders attached or not?

    Mike

    Incidentally I have been looking at EMI filters and line reactors - are these necessary? Those line reactors are sure expensive.
    I would investigate proper grounding before going into line reactors etc.
    Also, there are simple EMI L/R/C filters that you can put on the 240v supply to the PC for e.g. made by Corcom and others.
    You should bond all metal parts of the machine, at least all that have anything electrical mounted on or to them. And take the bonding conductor back to the ground star point.
    I have some previous posts in the regard of Grounding practice.
    I will look over you build posts and get a better feel of what you have.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

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


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    Registered Mike F's Avatar
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    A little more information:

    I tied all the metal structures to ground but it did not seem to make any difference. With Mach3 running but in Reset, the drives go haywire and the charge pump relay does a merry dance.

    I could not understand why the relay should be going berserk when, to all intents and purposes, Mach3 was not communicating with the controller. I had assumed that all the noise was coming down either the limit/home switch wiring, the servo motor wiring or the encoder wires. I disconnected the parallel port cable from the computer, tried the spindle again and - complete silence!!

    It seems to be a clue but I don't exactly know what to do about it.

    Mike



  8. #8
    Community Moderator Al_The_Man's Avatar
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    You could first try this, with the PC off, meter resistance from the 5v common pins on the parallel port to earth ground, normally the PC power supply common will be grounded through MB mounting screws to the metal chassis.
    If high resistance, it means your PC supply is floating.
    If as expected, it is low resistance, take a ground conductor from here to your central ground point and try again.
    If high resistance, I would take steps to ground the PC power supply common and also the port common pins.
    Al.

    CNC, Mechatronics Integration and Custom Machine Design

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


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    Registered Mike F's Avatar
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    Al,

    Fingers well and truly crossed, I think we have solved the problem.

    The PC's pins all checked out OK but we did find some wiring faults in the controller. I had mistakenly tied the shielding of the small power supply (giving me 5v and 12v) to the 0v of the supply giving me 40v. Also, the commons from the small supply were not referencing the same 0v as the other supply so these were then tied to the same reference as the main supply.

    At this point, the testing was very much better with the scope showing very little interference. However, the servos were still twitching and causing Mach3 to go into reset.

    My electronics friend then suggested we should try connecting the 0v from the supplies to the chassis ground. This seems to have been the final piece in the jigsaw and once this was done, there was not so much as a murmer from anything. The spindle was run up and down a number of times with no effect and the machine's axes were jogged whilst doing so also.

    I have to admit to being totally baffled by the whole electrical/electronic wizardry and am only too grateful for the help from those here and my local helpline.

    The next stage is to make permanent the grounding, try to route the spindle cable within the energy chain and to connect the VFD to Mach3. I appreciate that all the advice says I should not run the spindle cables alongside the other cabling but should I then run into difficulties again, at least I will know the cause and will be able to do something about it.

    I very nearly went down the route of buying expensive chokes, filters and reactors but, due to advice given here by Al, there was no need. Thanks Al for your assistance.

    Mike



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    Community Moderator Al_The_Man's Avatar
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    Quote Originally Posted by Mike F View Post
    My electronics friend then suggested we should try connecting the 0v from the supplies to the chassis ground. This seems to have been the final piece in the jigsaw and once this was done, there was not so much as a murmer from anything. The spindle was run up and down a number of times with no effect and the machine's axes were jogged whilst doing so also.


    The next stage is to make permanent the grounding,
    Mike
    Mike,
    I think that confirms my previous theory on the reasons for many of the spurious trips that constantly get reported here.
    I know a lot of people are averse to making all PS commons tied to a common earth point, but this goes part way to confirming it should be done.
    Thanks.
    Al.

    Last edited by Al_The_Man; 01-25-2009 at 06:12 PM.
    CNC, Mechatronics Integration and Custom Machine Design

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


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    Thats great Mike, glad you got it sorted and thanks for posting your findings which looks like an end to your problems.

    I'm sure it will help others in the future and maybe myself as I hope to use a similar setup.

    If you get time can you post a video of the spindle cutting some material.

    Thanks

    Andy



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    Registered Mike F's Avatar
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    Hi Andy,

    I have a few things to sort out yet but once done, I am sure I could post a video. It will be on my build log though, not here. I still have to sort out a water tank for the cooling and I had thought of using the space in the gantry to house it. It means the tube runs will be short and the pump more effective though it will mean the gantry has to carry the extra load but I don't think that will be a problem.

    I will post the progress in my build log.

    Cheers,

    Mike



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