G320 Brush Servo Drive errors on K2 2525

I'm totally stuck in fixing my K2. Brief history of the machine. Purchased in '08 it was never put into service until earlier this year. It was purchased when K2 first started providing servo drives instead of just steppers. It spent several years in storage. I greased everything and it was acting pretty good for the handful of short jobs I threw at it. However... It has become completely unreliable.

I have done troubleshooting and moving any axis will cause the error. In fact I removed the x assembly from the ball screw and it will error moving the ball screw with nothing connected. I'm using Gecko G320 Brush Servo Drives. They are designed to error if the motors draw too much current, OR if the encoder fails behind the requested position. The three drives are wired in a way that if any one of them fail, they are all halted, which on the surface sounds reasonable, but there is no way to determine which axis failed, or just as important, why it failed... The speed is 100ipm and the acceleration ways reduced from 30 to 25 on all axis before the jog test. All motors are barely warm and the drives are also barely warm. I find it hard to believe it's over current. All Gecko drives current limit is 20 amps and is set to maximum. It will error at lower speed, at lower acceleration, moving any one or more axis, it is unusable.

Are there better options for wiring these drives? Are there better drive options out there. At this point I have an 8 year old brand new piece of junk, costing $12k. I could really use some expert advise as I'm to the point of depression as I can't really promote my gun case business with a goobered up cnc... Nice day all...

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It doesn't look like you've got much heat-sinking on those drives, but if they fail right away, then heat's probably not the issue. Have you tried tuning the drives, using a fine screwdriver to adjust the trimpots? It's recommended to use an O-scope to do this, but trial and error can also work (eventually). There's info on how to do it on the Gecko site, but here's some more advice: Fabrications of the Mind: Tuning EMC2 and Gecko servo drives

I'd disconnect all but the one drive I was working with at the time, just to narrow things down. And if all else fails, you can ask Gecko for help - they're amazingly good about supporting individual users.

Thank you for the reply Andrew! I went to your link and it was very helpful. I also called K2 and talked to their tech support guy. He told me to adjust the pid as well. So I connect my scope to the test points for X and set it to 1v/div 10mS sweep and the damping looks really pretty good. It's rebounding quickly without overshoot and no oscillations. While I'm jogging back and forth I see a large spike and the drives error out and shut down. It does not seem to be associated with the start of motion, it faults in the middle of a move. The test point is a voltage that represents the amount of accumulated error. There is no logical explanation for me to see a large spike on this test point. Something is wrong with the drive wiring, maybe the part K2 made. Without a schematic I'm not sure what to do. It was failing on all axis individually. I can't see it being pid. I have no idea how to get this thing to be reliable, I mean I'm running out of ideas. :(

Can't the folks at K2 tech support provide a schematic for you? Something must be seriously screwy to give you those big spikes that fault the drives - maybe a ground fault? You can ask Gecko to check them out for you, but I doubt they're the problem. If you can't get K2 to fix this, I'd say invest in a new breakout board and wire around all the K2 stuff. They aren't that expensive. Your motors are probably good, but there could be something wrong with the power supply. Basically, you have to keep replacing things until it starts working correctly.

Hi Andrew, thanks for the reply. Well K2 went under earlier this year or late last year. I am in the process of wiring an arduino for use with grbl. I hope I'm not opening a can of worms. :/

Why not disconnect the error-in or the fault circuit and enable all drives, try them one at a time and see which errors out by way of the fault light..
Al.

I'm going to do that Monday. I would like to know what's going on even though I am changing to a usb or ethernet solution.

Hi Robot Dude. Did you ever find out what was causing the K2 servo drives to fault for no apparent reason. Ive been chasing this problem for years on my K2 machine. It will work fine for awhile and other times I just give up for the day. Im hoping you have some insight before I start replacing the power supply and bob. Thanks