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Author Topic: Alright fellow campers...a frankenstein moment!!  (Read 6386 times)

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Alright fellow campers...a frankenstein moment!!
« on: November 12, 2017, 05:40:58 PM »
So the situation is this:  I have a mach 3 running a cnc gantry style and I have added a forth axis (A axis)  It has its own power supply and control board.

My spindle runs separately and it is not controlled by mach 3.  I turn it on manually.  There are no wires running from the inverter vfd that runs the spindle, and control board--none!. So the vfd, spindle electrical cable, and spindle are not wired to the control board that runs a-axis or to the other control board that runs any other stepper motor!.  A-axis lathe is run by a stepper driver and stepper motor.

But the following happens: When the spindle is activated by turning on the vfd ---the A-axis rotary starts turning, but it sounds like its grumbling badly as it spins up to rapid.  Its not suppose to do anything.  If I disconnect the usb cable between the A-axis control board and the computer, and then start the spindle running, then A-axis does nothing.  Plug it back in with the spindle already running--and a-axis revs back up, grumbling.  Actually its sounds like a growling cat or something tearing itself apart.  If I disconnect the energy cable from the spindle motor, a=axis still turns (vfd still turned on).

IF I EXIT MACH 3 ALTOGETHER... AND THEN TURN ON THE VFD, THE A-AXIS still SPINS UP!! 

Hitting the emergency switch, stops x-y-z movement, but the *7!@# lathe keeps on turning...(its alive!!)
Hitting the home switch for a-axis does nothing... still keeps turning.

Ok you wizards... where did I f*** up.  bob




Offline ger21

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Re: Alright fellow campers...a frankenstein moment!!
« Reply #1 on: November 12, 2017, 05:53:54 PM »
You need proper shielding and grounding on your VFD and cables.
Gerry

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Re: Alright fellow campers...a frankenstein moment!!
« Reply #2 on: November 12, 2017, 08:20:58 PM »
I have good grounding all the way back to the main panel of the building... checked it with a continuity meter.
have to think about shielding my cables and vfd

liked your advertisements, not sure how they apply to my current issue... bob
Re: Alright fellow campers...a frankenstein moment!!
« Reply #3 on: November 12, 2017, 08:25:40 PM »
Has anyone out there had a similar issue...

Offline RICH

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Re: Alright fellow campers...a frankenstein moment!!
« Reply #4 on: November 13, 2017, 07:23:06 AM »
Simply, and I mean very simply stated, your problem us that you have a transmitter creating interference and something that acts as receiver of the interference.

There may be no single simple solution but what Gerry said is a start.
Most folks just don't understand interference and there are many books written on the subject. Hopefully the electrical and  instrumentation folks will give you specifics on what to do.

Will not go into any detail, but, resolution of the problem is something like this:
- Identify the source of the problem
- Eliminate, isolate, reduce, contain the  source of interference
- Provide protection from interference to any device


Quote
I have good grounding all the way back to the main panel of the building

That may be true from a purely electrical code point of view.

For interference, ( term used very loosely for the sake of simplicity) one
may want to provide a seperate ground system.

----------------------------------------------------------------------------------------

Simple things to do and  try:

- Make sure your wires are all shielded
- Provide a ground system for the shielding
- Move the electrical plug of the VFD to different outlet  that is not part of the circuit
  used for the PC or electrical supply to the router.
- Move the VFD as far away from the router as possible
- Keep wires to and from the vfd away from other wires
- Any control boards etc for the vfd should be enclosed

Only do one change at a time and see if it solves the problem
RICH
« Last Edit: November 13, 2017, 07:29:26 AM by RICH »
Re: Alright fellow campers...a frankenstein moment!!
« Reply #5 on: November 13, 2017, 08:01:41 AM »
In the past I have had similar issues with Freq drives. I had both ends of the shield grounded. This proved to be a mistake. When I would unhook one end of the shield  .
The issue would go away.  It is kind of like an antenna.  Dont know a better way to describe it.

Offline Chaoticone

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Re: Alright fellow campers...a frankenstein moment!!
« Reply #6 on: November 13, 2017, 08:39:01 AM »
All good info fellas.

Tweakie has a very good write up on noise somewhere. I think it was on his website.

This is to a post in members docs..... http://www.machsupport.com/forum/index.php/topic,25616.msg180583.html#msg180583
;D If you could see the things I have in my head, you would be laughing too. ;D

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Re: Alright fellow campers...a frankenstein moment!!
« Reply #7 on: November 13, 2017, 06:08:43 PM »
I want to thank everyone who responded to my issue with the vfd interference... I replaced the cable from the inverter to the spindle motor and with a shield cable and that solved the problem immediately... so thank you very much... bob

Offline Chaoticone

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Re: Alright fellow campers...a frankenstein moment!!
« Reply #8 on: November 13, 2017, 07:27:40 PM »
Glad you got it sorted. Mitigating EMI is a lot like black magic. There are common practices (which is a good place to start) then there is the thing that actually fixes it. Which may require some nose twitching, a crows foot and other ingredients. Consider yourself lucky if your first attempt fixed it.
;D If you could see the things I have in my head, you would be laughing too. ;D

My guard dog is not what you need to worry about!
Re: Alright fellow campers...a frankenstein moment!!
« Reply #9 on: November 13, 2017, 10:15:03 PM »
I spoke too soon... Earlier today I put in the shielded cable and it worked beautifully...  no turning of the 4th axis lathe when the spindle came on.

Later this evening I came in and decided to run it again before I tried to cut some stuff... but upon spindle spin up, the lathe started turning???

Now when the lathe comes on under these conditions, I notice that it is trying to turn both directions at the same time.  Does this trigger any ideas in anyones mind?

All thoughts appreciated... bob