I'm Stump'd - Intermittent Axis Stalling with NO LOAD?!

[MA$TER_E]

I'm stumped guys and gals... I've been fighting a stalling issue on my K2 Router almost from the day I put it together.

I started off with a "Green Monster" Nema 23 400oz 3 axis kit from Probotix. It would stall once in a while and I wasn't to wild about the probotix gear so I upgraded to a bigger better Gecko G540 system and it still stalls.

Here's the thing. I thought it was binding so I removed the belts from the pulleys and even without any load at all the motors still stall. X, Y and Z axis will stall intermittently and only when a program is running. I cant get it to do it while I jog it around. I use BobCAD to generate all my G-Code and there's nothing funky going on in the code to make it stall. So its not binding or choking on code.

Last night it crashed a few times making some parts for a buddy and really caused some grief for me. So I sat down and tried every possible switch, toggle and setting I could find in Mach3 to try and fix it.

I found that the NC code that would always stall in the exact same place every time would run right through when I checked the box to enable "Sherline 1/2 pulse mode" in Ports & Pins. Unfortunately it did have a couple Z stalls later on in the program so it got better but still not good enough.

I want to just pull the trigger and buy a set of Nema34 motors designed to run with Mach3 and the G540 from Kelinginc.
KL34H260-35-4B But I really don't have the money right now for new motors plus whatever it'll be for new 1/2" pulleys and belts. Not to mention I'd need to build some new motor mounts.
Cry me a river right?

Here's the specs on the Probotix steppers I have.
Probotix Green Monster Motors

I've flipped all the switches and pushed all the buttons. I don't know what else to do. I don't see anything obvious that says new motors would solve the problem. In fact I don't see anything that says this is the problem. ANY advice or pointers would be very appreciated. I've got'a get this figured out.



My K2 KG-2525 Router Write-Up

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[awerby]

It sounds like a motor tuning issue to me. What velocity and acceleration are you trying to run at? Try reducing both numbers on all your axes (especially Z) to half what they are set at and try your program again, then let us know how it worked, okay? Normally Z will have the most load on it, since it has to lift the spindle, so typically its velocity and acceleration are set lower than the other axes.

The other thing that you might check is your current-limiting resistors. If you've used the wrong ones and are starving your motors of amperage, that could cause stalling as well.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[awerby]

It sounds like a motor tuning issue to me. What velocity and acceleration are you trying to run at? Try reducing both numbers on all your axes (especially Z) to half what they are set at and try your program again, then let us know how it worked, okay? Normally Z will have the most load on it, since it has to lift the spindle, so typically its velocity and acceleration are set lower than the other axes.

The other thing that you might check is your current-limiting resistors. If you've used the wrong ones and are starving your motors of amperage, that could cause stalling as well.

Andrew Werby
ComputerSculpture.com — Home Page for Discount Hardware & Software

[frankee]

Just to cover all bases, confirm that you haven't recently turned on your network card or some other new program that steals CPU bandwidth and stalls Mach3.

The effect of that will also look identical to the situation you describe (from personal experience).

Frank

[MA$TER_E]

Hey!

I've reduced the velocity and acceleration from 120/10 to 75/8 to 50/5 and velocity/acceleration doesn't seem to have any impact on the stalling. I've even used the override and reduced feed to only 5% of 40ipm and it would still stall without the motors being hooked up at all; just free spin'n.

I called and talked with guys at Gecko and they recommended with my motors that I remove the limiting resistors all together. My motors are rated for 4.2? Amps so the G540 won't hurt anything. Just put a full 3.5A to the motors and deal with a little extra heat. So I did that and I can't see any improvements to the stalling situation by doing so.

I was reading through my old thread and started thinking about grounding again. Right now I've got a 12'ish AWG ground wire connecting my frame to the grounding rod for my breaker box over about 12'ish feet. I'm starting to wonder if that's sufficient. I know grounding makes a HUGE difference but maybe with the distance I'm going my ground wire isn't big enough.

What are your thoughts?

Edit: For Frank

I've even unplugged anything USB or PCI that doesn't need to be connected. Walked through the Mach3 "optimization" guide again and took a look at my CPU while Mach is running and once in a while it'll spike at 1 maybe 2 percent CPU while running but during a stall there's nothing. Not even a tiny little ripple in CPU usage.

[MA$TER_E]

I'm going to go out on a limb here and say that the problem has been resolved.

I gave Gecko a call and was going to purchase a set of their steppers to replace mine. They connected me to tech support and I had a nice talk with Marcus. Marcus has helped me before and I must say Gecko KICKS A$$! They've got this customer service thing figured out and if I need any kind of driver believe me Gecko will be getting my business for sure.

Anyway, I explained my issue and why I wanted to replace my motors. Here's the key parts of my situation that's been causing me grief.

A) - The K2-KG2525 and most other higher end K2 routers are designed to run servos. As a beginner I elected to forgo the servos and run steppers then maybe someday when I know what I'm doing upgrade to servos. Well the frame is still geared 1.5:1 for servos. And as it was explained to me steppers generate most of their torque at low RPM and servos need higher RPM and the gearing ratio is hindering the performance of my steppers. They have to spin faster to compensate for the drive ratio which at the rates I'm traversing is getting really close to the max of what my motors are rated for.

B) - With the drive ratio I have the accelerations were to much for the steppers to handle. That's why loaded or free wheeling the steppers would stall. They were being asked to accelerate to quickly and would result in a stall. I've gone in and set all of my motor accelerations down to ridiculous slow 3? maybe 4? Its really slow BUT I've cut 4 projects thus far without a single stall.

I plan on replacing the pulley's soon and going to a 1:1 drive. I'll still more than likely upgrade my motors someday. Kelinginc has a pretty nice NEMA34 motor meant to run with the G540 but for now I'm up and running and most likely until something breaks I'm not going to mess with things.



Eric

[ger21]

The Nema 34 on a G540 will likely have an even slower maximum speed, due to the higher inductance. Going to a smaller motor might give you better performance than a larger one. If you want the most torque at the highest speed, then the 381 oz motors Keling has are probably the best option.

What pitch are your leadscrews? If they are 5mm, or 5tpi, then gearing 0.5:1 might be an even better option.

[MA$TER_E]

The Nema 34 on a G540 will likely have an even slower maximum speed, due to the higher inductance. Going to a smaller motor might give you better performance than a larger one. If you want the most torque at the highest speed, then the 381 oz motors Keling has are probably the best option.

What pitch are your leadscrews? If they are 5mm, or 5tpi, then gearing 0.5:1 might be an even better option.

I'm not sure what the pitch is anymore, I need to measure to see. I thought I was running a 2:1 ratio and turns out its 1.5:1 and I thought the screws are 0.2 but knowing what I know now I'm sure they're metric.

That's a good point on the inductance. I probably won't be doing anything until something comes undone. But when the time comes I think it would make the most sense to stay with the Nema 23's so I don't have to fuss with making new motor mounts.