Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: mercury049 on January 11, 2016, 10:10:58 PM
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Greetings again.
Ok, last time I posted here, I was having issues with my 2.2kw spindle causing E-Stop signals being sent. The answer was for me to shield the cable that connected from my VFD to the spindle. So, I did. I bought special wire that's well shielded. Still having issues, but they're different now.
More info here...It's a Gecko G540 on a home built machine.
I have grounded the machine, spindle, shielded cable to ground via a ground wire to my outlet. I have also wrapped my spindle in electrical tape and put it back in mount to isolate it from machine.
I have turned my Debounce down from 2000 to 0. Sure enough it will run, for a bit. After anywhere from 30 to 180 seconds, it will throw an e-stop. So, things are MUCH better for sure. But I'm concerned I may still lose steps.
At first I turned my Debounce to 2000 to avoid the signal issue, but noticed that the machine would lose a TON of stop and wreck a project half way through. I assumed that was due to the signal issues. Even @ 2000, it will still throw a stop signal every so often. I would just click start to resume it and it would carry on, but I believe it was in those moments that steps were lost.
For troubleshooting, I took the spindle out of the mount and ran a job on the machine. It didn't stop once. NO problems at all. I can run the job with the spindle in the machine so long as it's not running, no problems at all. But if I turn it on, it's only a matter of time before an EStop is thrown.
What am I missing? Why am I still getting estops through every so often? Thanks for any advice!
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Also, I'm using shielded DB9 cables from Gecko controller to motors.
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Have you an EMI filter on your invertor, essential to stop noise............?
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No, I don't have an EMI filter. Didn't know I needed one. Can you recommend a reasonably priced one?
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Think you'll need to match it to your VFD, most CNC suppliers will have them for £50 or there abouts.
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Sounds more like grounding to the outlet may not be a good ground path to earth. In some places depending on building code the neutral and ground is connected in the electrical panel and can cause ground loops. All cable shielding should only grounded on one end and connected to a ONE common point on the machine, then to a earth ground (water pipe or ground rod). If this is a Chinese VFD they are low quality and known to be very RF noisy... none meet UL or CE standards. There is a reason they are cheap because they lack the RF suppression found in higher quality drives. Make sure the VFD case is grounded.
Remove the electrical tape from the 2.2kw spindle motor mount. This does nothing except make the motor case ungrounded which is dangerous in the event a motor winding shorts to the case. Touching the motor and the machine frame, you can become the path to ground. Chinese spindle motors are not case grounded internally. The connector plug has 4 pins... only 3 are used for T1,T2 and T3. I grounded my 2.2kw motor case with the 4th pin and used 4 wire VFD shielded cable, then grounded to a common point on my machine. EMI filters only prevent electrical noise from feeding back into the mains from the VFD. Good to have but not going to fix your problem.
I work on large VFD systems up to 1000hp... so I have allot of experience with chasing noise problems.
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Well, I ran a ground cable to earth from the spindle after I isolated it with Electrical tape. Shouldn't that help?
I'm going to try your suggestion of grounding the Spindle and VFD/Spindle wiring shield to one point on the machine and then grounding the machine to earth. If it continues, I'll try another circuit completely for grounding, if that doesn't do it, I dunno what I'll do. =(
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Read up on star grounding.
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What type/name of VFD are you using? Another suggestion is reroute the e-stop wiring as far away from the VFD & motor cable as possible and see if that helps. Maybe it's something simple as a loose e-stop connection?
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It's that cheap chinese stuff from Ebay. Hyunyang or whatever. I've separated them. In fact, if I take the spindle out of the mount, turn it on and hold it in my hand, the machine runs fine. It only throws the estop if I just barely touch the casing anywhere on the machine. It's definitely causing it to ground out and throw the estop. After making some adjustments that I mentioned previously, it's gotten better, but still after about 45 seconds or so when connected to the machine, it will throw an EStop. I think my next effort will be to try the star grounding mentioned by the previous poster. I feel like I've already done that, but maybe it could be cleaned up a bit.
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If you have a digital voltmeter remove the motor from the machine. Put one lead on the motor case and the other on the machine frame, VFD metal case or a grounded location. Turn on the motor and see if there is voltage. It should be zero. Any level of voltage leakage present from the motor case to ground indicates a partially grounded winding and could be the cause of your problems. Just so you know... a 3 phase motor will run with one partially ground winding. Unless the VFD has motor ground fault detection it will just keep working until it shorts out completely.
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If the shielded cable to the spindle is attached to ground at the inverter end and to the spindle at the other end then you have two paths to ground, one through the cable and the other through the frame of the machine. This is called a ground loop. Since the motor is mounted to the frame you should leave the ground wire connected at the spindle and insulate it from ground at the Vfd end.