Fault in Gecko G540

[ArtG]

I recently made some modifications to my CNC which is a self built versions structured from a RoverCNC LT platform https://www.rovercnc.com/. I know I updated the Acon System and I added a larger spindle to this CNC, a GMT 2.2kW model, that most likely increased the weight from the Dewalt 611 router by another 15 lbs. Initially after the upgrade, no big changes in the operation of the CNC. I have been manually turning on the Spindle and setting the speed via a remote. good. I decided to grease and tram CNC with the new spindle. I don’t use my CNC very heavily, but due to the design, I have to unbolt several plates in order to grease the bearings.

During my upgrade I noticed several changes. I ran several small jobs and all seemed good. I decided to grease and tram CNC with the new spindle. Once that was completed, once I turned off the Acorn software the Z motor released and dropped the spindle to what ever would stop it. That was new, I had never seen the motors release, until power was removed from the CNC controller. I realize that I have added a lot of weight to the Z axis, but not sure why it would start dropping or lowering once the acorn program is stopped.

Today, I had a fault on the Gecko G540 and the spindle dropped into the work about a third of the way through the process. All motor activity had stopped except the spindle motor, until I was able to stop the process. After restarting everything, all seems to be fine. that is no fault or any movement issues.

Not sure if thing will continue to work or if I need to make some changes.
Just hoping someone can help me figure out the true issue here. Not sure if I should be working on the stepper motors, or counter weighting the spindle or what.

I will attach an Acorn report.

thanks Art

[ArtG]

Update. Still not sure why I got a fault in the middle of a process. I was putting a 12 in radius on a guitar fretboard using a parallel process with step overs of 0.003 so really slight X or Z movement and I had the Y running at 140% of the original speed.

I emailed the guy I purchased my steppers 600oz Nema 23s from and he thought the additional weight of the Spindle was causing the Z axis to drop when not powered and recommended a motor that that has a 24 vdc brake. The brake would only work when the power was off. Interesting.

He also guessed that the Gecko fault was caused by a non shielded VFD cable. Darn! I have built this CNC with everything shielded and haven't had any issues since moving over to the Acorn platform. I saw that Marty recommended a nice Belden VFD cable after I had purchased the non-shielded cable.

Gecko Tech Support was a little elusive on the EMI causing an issue and was more concerned if the 600 oz/in (35.7 in/lb) motor was sufficiently sized. The Z axis manufacture, recommended a minimum 420 oz/in motors, so I guessed the 600 oz/in motors were sufficient. Gecko also recommend lowering the velocity by 50% to get more torque.
In addition, he recommended that I remount the old router motor and run that to see if I continue to get the Fault on the Gecko G540. that made sense but really struggling with have to go backwards to move forward.

thoughts?

[Richards]

What is the mH (inductance) spec for the Z-axis motor. For efficient use with the G540, a motor should have 2-3mH inductance. Anything higher means that you have to slow things down to allow the motor to overcome its own inductance.

[ArtG]

Thanks for the input Mike,
Interesting, the Phase Inductance on my motors is 3.9mH +- 20%. So I should be lowering the velocity? I was kind of thinking I was kind of conservative and was planning to increase the speed. I was reading the manual (rev 8) on the Gecko web site and they reference 1 to 30 mH inductance, not that it means anything, as even Gecko support recommended lowering the speed. I will try that.
The one thing I did do differently is increase the speed on the Acorn control to 140%. I had really small step overs to get a smooth surface and wanted to speed it up.

It actually could have been any one of the drives, as all four are set up the same.

Do I change the Max Speed is 75 in/min or that and the Max Jog rate is 50 in/min. Acceleration is set to .5 second.

[Richards]

The issue with high inductance is voltage. Geckodrive uses the formula 32 X (SQRT(mH)) = maximum voltage. In your case 32 X (SQRT(3.9)) = 63V. The G540 is rated up to 50V, so you would lose a little top speed. The maximum motor current is 3.5 amps. Voltage relates to speed. Current relates to holding torque. With a 3.5K resistor installed on each DB-9 motor connector, the motor will be limited to 3.5A. I would use a 3K or 3.3K resistor to allow for manufacturing tolerances in the resistors. Excessive current could cause the drive to fault. Anything that causes the motor to draw more than normal current could cause the drive to fault, such as excessive speed or mechanical binding.

[martyscncgarage]

Whenever you have a machine with a ball screw and linear rails on the Z axis, it is generally required that you add an axis drive motor WITH A BRAKE.
Otherwise it will fall if there is a fault. The control has an output to control a brake. Axis motor brakes are normally locked until they are energized.

[ArtG]

Mike,
Thanks for that clarification. I think I have 3.2K or a 3.3k resistor installed and actually have some 3.48K resistors that I got but haven't replaced these yet. I think I will leave them as is. I ran the same job again last night, but didn't increase the speed on the Acorn control so it ran around 40in/min feed rate instead of 60. It complete the run successfully without fault. A little slower is just fine.

[ArtG]

Marty,
thanks for the validation on getting the brake with the Z Axis motor. I assume that I would set that up using one of the relays on the Acorn controller on the NO contacts and have it close the relay at with Acorn Start and open when Acorn Closes or a Drive fault is detected?? Not quite sure how to set that up.

The only 24VDC power supply I have in the box is for the Acorn board but I am very hesitant to use that. I believe I read in someone else's post that using the Acorn power supply is not a good Idea.

[martyscncgarage]

Marty,
thanks for the validation on getting the brake with the Z Axis motor. I assume that I would set that up using one of the relays on the Acorn controller on the NO contacts and have it close the relay at with Acorn Start and open when Acorn Closes or a Drive fault is detected?? Not quite sure how to set that up.

The only 24VDC power supply I have in the box is for the Acorn board but I am very hesitant to use that. I believe I read in someone else's post that using the Acorn power supply is not a good Idea.

I use Din rail Mean Well power supplies. A 2.5a 24vdc model is about $20 from Amazon.
MEAN WELL MDR-60-24 DIN-Rail Power Supply 24V 2.5 Amp 60W
by Amazon.com
Learn more: https://www.amazon.com/dp/B005T6OBFU/re ... UTF8&psc=1

Yes on the NO contacts

Marty