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  #1  
Old Wed 24 June 2009, 14:45
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Spindle RF noise makes y car & z axis move

Well,
The machine moves well, performs and executes G-code fine.
...then I turned on the spindle. Yikes....talk about cross talk in the wires.
The spindle turned on at 500 rpm or higher the y car or z axis will start by themselves moving. I have dealt with this before on other machines. Just not my MM.

...I will spend the next day testing different isolation methods for the VFD cable to spindle wiring and the cable chain that has all the motor leads in it.

All suggestions are welcome, but I will start my signal flow challenges tomorrow when it's cooler - like at 4am!

The VFD is mounted external to the drive cabinet like Gerald's installations and the spindle is switched via the J7 contact.

...more to follow tomorrow.

Sean
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  #2  
Old Wed 24 June 2009, 23:24
javeria
Just call me: Irfan #33
 
Bangalore
India
Having proper grounds is your way out Sean!
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  #3  
Old Thu 25 June 2009, 00:04
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Proper grounds are only a small part part of the solution, as Sean knows. Some other parts of the solution:

Eliminante ground loops
Screening/shielding (single end grounded)
Separation distance
Non-parallel unscreened cabling

For the VFD in particular, reactors and filters, normally mentioned in the VFD handbook. (We have big ferrite rings on the Line In and Load Out points of the VFD, as well as a reactor on the Load Out)
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  #4  
Old Thu 25 June 2009, 02:18
javeria
Just call me: Irfan #33
 
Bangalore
India
I have a EMI filter on the input and the ferrites on the all the ip and op wires of the VFD, apart from that have ferrites on the motor wires extremely close to the motors - don't know how they help - but have certainly made a difference.

RGDS
Irfan
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  #5  
Old Fri 26 June 2009, 18:30
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
All clean now.
Whew - that was exhausting. I had 2 sources of noise.


What was done:
-I ran new motor cable that had a double braid and foil shield. (prior motor cables only had a foil screen)
- added a single phase 220V isolation transformer feeding the spindle VFD

Then.....I had the z motor doing this little *tick...tick..........tick........tick* sound and movement.......6 hours later I found the Proximity cable to the z axis had to be grounded to the machine. ( i had not mounted it yet) Once I mounted the darn thing, the entire machine went quiet.

Have I mentioned how much disdain I have for erratic grounding/isolation issues? One machine - no problems at all....the next machine, same build, all sorts of noise.

Now back to programming the OEM buttons and such.

Sean

Last edited by smreish; Fri 26 June 2009 at 18:56..
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  #6  
Old Fri 26 June 2009, 22:08
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Thanks for that feedback Sean. Well done!

It is amazing how sometimes these machines work okay without any special attention to grounds, shields, isolation, etc. Then a day comes along when it just won't work. And then to make it work, you have to break the "rules", like forcing a ground loop for a proximity switch.

One is torn between 2 choices:
1. Spend hours and dollars putting in all the "right" stuff from the start, knowing that you might still not have it 100%
2. Be less careful and know that it could be 100%

It is all a game of chance! (for us blokes without oscilloscopes and RF measuring equipment)
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  #7  
Old Sun 28 June 2009, 02:33
Kobus_Joubert
Just call me: Kobus #6
 
Dalview
South Africa
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Maybe I had luck on my side. I did not use any shieled cables. My steppers are fed with normal 4 core extention type cables. No noise or other problems so far. BUT I am sure something will show up if I replace my router with a spindle in the future
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  #8  
Old Mon 29 June 2009, 09:27
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Round three of electrical noise.

Problem:

The Pmdx is seeing the "ground flutter" the stepper motors were seeing. Only on the sourced inputs which are pins 11, 12, 13 and 15.

Solution:

First, tried to debounce the circuit (under general config in Mach 3). I could not effectively bounce the signal to rule out false positives.

Second, I Isolated the inputs by using a secondary relay to isolate the momentary push buttons on the machine from the PMDX.

How I did this.

Using the same 12vdc relays as used in the limit switch and homing circuit I have now source 12vdc out to the push buttons which now close a contact. That contact then closes the corresponding pin on the PMDX.
I effectively now have a "dry contact closure" close to the PMDX. Close is the reason. The switches close a dry contact as well, but because of the distance away from the PMDX and parallel runs in the cable chain, the PMDX "com" is inductively picking up signal from the grounds.

...more to report soon.


Local Electrical that is affecting this installation:


Flanking the building on each side is a citrus packing facility and on the other sub-zero refrigeration warehouses. A lot of machinery, compressors, conveyors, hoist's, dock elevators....you name it! To say the least, I have every type of bad power challenges most, if any, MM builder will every experience.
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  #9  
Old Sun 20 September 2009, 02:03
liaoh75
Just call me: David
 
Taibao
Taiwan
Hi Sean, I also just put in a spindle (the Chinese variety 3KW). I experienced the same problem. I am using a top of the line Rich EI-S9001-005L 5HP inverter with all the bells and whistles. They even say that it can be used as a servo controller with an add-on card installed. They said it was completely "something" isolated. I got it for free (long story - nothing illegal ) I thought everything would work like a champ. I decided not to go for the Chinese Inverter that was sold as a kit with the spindle I got.

And then...... The trouble began. I, too spent all day getting everything mounted and I had shielded cables for just about everything with the exception of the DC power source for my proximity switches and power feeding the Gecko G203Vs. I got the same behavior as your machine with the Y-axis and X-axis (No Z-axis though - scratch head) moving on it's own with no pulse from the PC. Like you, my brother-in-law and I spent hours with isolation exercises and wiring and re-wiring. Just as we were about to throw in the towel after about 5 hours, my brother-in-law called an inverter "pro" (also the guy that gave us the inverter for free) and he told us to disconnect the ground from the inverter completely and let him know what happenes. After following the guy's instructions, the machine stopped its eradic behavior but the E-stop kept triggering on it's own every 2-3 seconds. Pushing reset in Mach works but the E-stop was triggered again after a few seconds. We called the guy back and he told us to go through and -O.M.G.- un-ground one thing at a time (with inverter already not grounded) and then like magic after I got to ungrounding the braided shielding from the push buttons (this is the 7 core shielded wire for E-stop, start, and stop push buttons) everything was back to normal. The spindle works just fine I ran a quick test with a small G-code file I had on hand and it was fine.

Now, this goes against everything about grounding I had spent so much time reading about in this forum. I now have an ungrounded inverter and no grounding on either end of my 7 core push button cable and everything works like a champ????

Sean, I'm as confused as you are, but give it a try. After everything was working, I talked to the inverter guy again and asked him several questions and the interesting thing is, he said that although it is not an industry accepted practice, a large number of machines in Taiwan running with an inverter and believe me, there are many all run day-in and day-out without the inverter itself being grounded.

Gerald, or anyone reading this thread, can you guys shed some light on what this guy is saying? I want to say that he is wrong but he did trouble shoot our problem over the phone within 20 minutes. I am beginning to think this "grounding" issue is very complex.

Last edited by liaoh75; Sun 20 September 2009 at 02:08..
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  #10  
Old Sun 20 September 2009, 07:17
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
<chuckle> In the old days of analog, when you tried to configure a sound system for a concert or show, there was invariably some noise (usually 60hz hum) that would creep into the system. It was commonplace to run around inserting a "ground lift" into those channels that were picking up noise. This was done as a pragmatic solution to a problem that there wasn't enough time or resource to solve.

Grounds are not a digital thing. You aren't "grounded or ungrounded"; you are tied, with varying degrees of resistance and noise depending on the wire, to a reference.

I had the experience once of climbing a scaffold at an outdoor music festival to handle an adjustment to an amplifier rack. This speaker cluster was a "relay", placed several hundreds of yards away from the main stage to extend the range of the audio system, as this was a citywide kind of event. The scaffold was grounded to ... the ground underneath it. The amp rack was grounded to the main audio system, which was grounded to the ground near the stage. I was holding on to the scaffold as I touched a metal panel on the rack. Ouch! So which ground was correct?

In practice, grounds can vary like any other conductor; they can pick up measurable voltages via magnetic inductance from adjacent wires - especially on long high power runs. They can act as antennas, and either broadcast or receive RF noise.

Your expert just applied the pragmatic, get-it-working-now approach to your machine.

http://www.epanorama.net/documents/groundloop/ might be useful reading.
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  #11  
Old Mon 21 September 2009, 20:23
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
David,
Great to hear you have it working.
It sounds like the you solved the inverter issue. I would venture to guess if you added an isolation transformer before the inverter, you would have resolved the issue as well...along with keeping the ground for the inverter intact. This will add cost.
On the estop signal...if it was only triggering every few seconds, you can try to change your debounce settings higher in Mach and make that switch act like a "one-shot" event and possibly reconnect it's shield as well. I wouldn't loose any sleep over the loss of the shield on that low voltage e-stop circuit. If it was the 110V side of the contact block that the ground was lifted on, then I would spend a little more time on troubleshooting further.

Glad to hear you have it worked out. Erratic behavior is a pain in the arse.

Sean
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  #12  
Old Tue 22 September 2009, 10:22
liaoh75
Just call me: David
 
Taibao
Taiwan
Hi Sean, I have ordered an isolation transformer (line reactor - is it the same thing?) for my 5 HP inverter. It wasn't that expensive here at $27 us dollars. I also found out that these things are comon place here and widely available. After installing it, I will attempt to re-attach the ground. I'll check on that debounce setting as well. Thanks for your advice. I'll post results after this coming weekend when I have time to work on it.
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  #13  
Old Fri 25 September 2009, 18:31
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
David
Line reactor is very similar.....just a few minor insignificant differences. The line reactor is VERY recommended from all drive manufactures when using a spindle. EMF affects machines differently. Great to hear your moving forward.

Sean
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  #14  
Old Fri 25 September 2009, 23:06
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Quote:
Originally Posted by liaoh75 View Post
.....an isolation transformer (line reactor - is it the same thing?)
A line reactor will not replace a standard isolation transformer, where we are talking of "safety" isolation. I know too little of these things, but I do know that a line reactor has copper connecting input to output - in an isolation transformer, the copper is interupted by the iron core. Using an Ohmmeter, the reactor is low resistance while the transformer is high resistance.
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  #15  
Old Sat 26 September 2009, 09:35
Richards
Just call me: Mike
 
South Jordan, UT
United States of America
As Gerald said, an isolation transformer is NOT the same thing as a line reactor. A line reactor is also known as a choke or an inductor. Its purpose is to impede (or reduce) rapid changes in current. Voltage spikes appear as rapid changes in current, so a properly sized line reactor reduces or eliminates most of the spikes that cause problems with electronic circuits.

On my Colombo spindle/Delta VFD, I have both input and output line reactors as well as an EMI filter. I doubt that I actually need the reactors and the filter. When I installed the spindle, I thought that I had noise problems caused by the spindle. It turned out that the problem had nothing to do with the spindle - it was caused by a wireless network card that kept losing connection which caused the SB3 program to pause until connection was re-established. However, I added the reactors and the filter as part of the problem elimination process.
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  #16  
Old Sat 26 September 2009, 09:59
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Mike,
Thanks for publishing that clarification. I guess in my haste that I should have said " a line reactor may give you the same results as the isolation transformer - by isolating and not eliminating the EMF from the line side of the electrical system." In a pinch, when not having one or the other on the shelf, I have had the luck of eliminating the bad noise in the system with either.


My apologies for bad information.
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  #17  
Old Tue 29 September 2009, 06:48
digger
Just call me: Milosh #113
 
Toronto
Canada
A easy try of eliminating EMI could be done by inserting a ferrite ring on cable which goes to the spindle. I would try to find some used computer monitor. A monitor cable which goes to the computer has a ferrite ring (core) molded into the cable. You can't miss it. Take it out and put it on your cable. This will prevent unwonted current going through the shield of cable (to be more precise, on surface of the shield). Better solution is to use some bigger in diameter ferrite core, and wind some turns of your spindle cable. This will make more impedance / resistance to the unwonted current on the shield.

My 2 cents...

Milosh
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  #18  
Old Tue 19 October 2010, 19:23
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Today a new issue arrived on Machine #58.

Symptom - while changing spindle speed from 18K down to 60 rpm for special milling procedure, the Z - axis would "step abruptly in the down or up direction" duplicating the noise issue the machine exhibited during the build.

Troubleshoot procedure was used to check every wire, shield and connection from Gecko to Motor. All checked out fine.

Interesting that the noise only showed up on the z-axis, and not the other motors in the same e-chain......this made me think....it's only getting disruption on the step/direction of the z-axis output from the PMDX. This is J3.

After quickly routing the J4 connection to the Z - axis Gecko and changing the ports and pins from the 6/7 to 8/9 - the problem was resolved. (2 hours later) Also, in order to allow only J1 J2 and J4 to run the machine with 4 Geckos, I had to share the x1 and x2 gecko's off the J1 step/direction signal which I have done before on other builds.

SO, The problem is J3 was able to duplicate the erratic behavior with all 4 gecko drivers - thus verifying that either the PMDX -122 board has a partial failure or the Parallel port from the PC that correlates with these pins has failed.

At this time, the machine is up and running and cutting fine.

Mike, Brad, Gerald, Heath.....any thoughts?


Sean
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  #19  
Old Tue 19 October 2010, 21:31
bradm
Just call me: Brad #10
 
Somerville(MA)
United States of America
Hmm. I'm going to obsess over a historic detail of the PC parallel port design. The original parallel port had an "open-collector" TTL output, meaning that it relied on external pull-up resistors to ensure the high state. This was clever in that it allowed the port to be used in a bidirectional mode; as long as the output was set to '1', a external device could drive the pin to either 1 or 0, and thus a value could be read back. Weak pull-up resistors that could be overpowered were used. Modern parallel ports emulate this behavior - in some modes.

I suspect that the pull-up for the J3 step signal is too weak, and thus noise sensitive.

So, I think I'd be curious to know if you have that parallel port in full legacy mode in the BIOS.

Assuming that is okay, then I think you've got it nailed; you need a new parallel port (or PC), or PMDX. I suspect the parallel port.

You could further diagnose with lots of careful voltage measurements and adding pull/up or pull/down resistors. Or faster, just replace the par port. But you know that, you've already got the issue corralled.

I keep a PCI parport adapter around because it's useful for such cases. Also, it's very common for the motherboard parports, which are part of a large multifunction IC, to have significantly smaller and less powerful transistors than those on discrete parport adapters.
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  #20  
Old Tue 19 October 2010, 22:12
Gerald D
Just call me: Gerald (retired)
 
Cape Town
South Africa
Have you tried another parallel cable?
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  #21  
Old Tue 19 October 2010, 23:38
domino11
Just call me: Heath
 
Cornwall, Ontario
Canada
I think that you guys have all the bases covered at the moment. I have, in the past had parallel cables go bad as well. It is also easy to damage a driver IC on the parallel port. It will still work but at reduced drive. Static damage can cause this when installing computer cards. Always a good idea to ground yourself (or use a grounded workstation) when working on a computer swapping cards.

On the pmdx input, you could have a damaged connector or solder joint on that input. I have seen problems like this when a wire gets yanked or twisted causing damage to the connector or board it is attached to . Or even a cold solder joint from the factory. Sometimes these types of problem can show up using an eye loup (magnifier).

I would go with cable, then port, then PMDX.

ps watch out for the fake parallel ports that are usb based.
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  #22  
Old Wed 20 October 2010, 06:00
MetalHead
Just call me: Mike
 
Columbiana AL
United States of America
I agree. I think you are on the correct track. It could be a cold solder joint on either the PMDX or the Parrallel cable. If plans are to isolate further I would try the cable first. Even disconnect check for issues and reconnect to see what that does. May be a bad inteface connection.

If the problem remains then buy a Parallel card. Then replace the PMDX. Do these all as seperate steps. As sure as you do two of them at once your problem will go away and you will not know which one fixed the issue ..... this is Murphy's law
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  #23  
Old Wed 20 October 2010, 10:03
smreish
Just call me: Sean - #5, 28, 58 and others
 
Orlando, Florida
United States of America
Gentlemen,
Thanks for chiming in. The purpose of the question was 2 fold - to spur critical thought and also add to the troubleshooting threads in the forum.

I have a new cable on order, and will try that soon.
I have a spare Parallel Card in the ready, if needed.
I have a spare PMDX as well in the ready.
I "thought" I had the BIOS set to EPP legacy - but I will check...that's a great point to check Brad.

When I have a Saturday afternoon when the machine is idle, I will start the process of finding the real problem. Unless it comes back quicker than that!

As for now, #58 is cutting quickly A LOT of parts at the moment.

Thanks for the replies.
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