[ModMatters]

Hello all,
I'm hoping someone can help me out. I have a shop in northern NJ. Purchased a 4x4 ft router from CNCRP guys (nothing but great things to say about them). Its taking me over a year to build this machine since I'm only in the shop once a week.

The machine is a CNC Router Parts 48x48 outfitted with Nema 34 motors, 2.2KW spindle, VFD and electronics are all completed. My problem is that I cant for the life of me, figure out why my machine is shaking so much!! As you'll see in the video, its only happening during linear motion so the X-axis. The Y-axis (Gantry movement) has perfectly fine and smooth movement and so does the Z-axis. I've had the nice guys from CNCRP try to help....tried all the suggestions but was still not able to figure out the issue. They suggested it was either CV settings (I definitely have continuous velocity setting in Mach3 on so I don't think its that) or too many line segments in the code instead of continious arcs (i've tried very simple designs and the machine is still shaking a lot).

If you'd like to see exactly what the problem is. I've uploaded the video to youtube here.

https://youtu.be/WmDCU-SgmoU

Note: either due to this issue or for other reasons, I had 2 x DM860 drivers fail on me...They are chinese drivers I bought on ebay so I wasn't expecting much but they didn't even last 2 weeks each...if one more fails I will just swallow the pain and get 4 Gecko G201X / G203V. Wiring seems good (see picture below), I've checked and rechecked everything, rewired all the drivers twice. Anyway, here's some stats:

• (4) x 1200oz Nema34 stepper motors from Longsmotor
• (4) x DM860 drivers
• (1) x unregulated 80V PS
• (1) x Ethernet Smooth stepper
• (1) x PMDX-126
• (1) x 2.2 KW Air Spindle
• (1) x VFD

Here's a picture of the electronics:

Attachment 387378


Truly hope someone can help. If you're an expert in setting up these machines or know how to troubleshoot this and would like to stop by my shop to troubleshoot in person (I'm located right off of NJ Turnpike, exit 14) - I will pay for your services! Send me a message.

[ger21]

Your drives are likely failing due to too much voltage. While they are rated for 80V, back EMF when decelerating can raise the voltage over there limit. And I don't think some of these chines drives have much headroom. I would not recommend voltage over ±70V.

Sounds like you have some resonance issues with those motors. What microstep setting are you using? Try increasing it.

[ModMatters]

Hi Gerry,
Thanks for your input. Big fan of your work.
I'm including both spec sheets attached - for the drivers and for the motors in case you'd like to review.

Drivers Failure:
As per my measurements the Voltage going to the drivers is right under 60V, i believe 57V to be exact. I think you're right, the PS probably put out too much and the drivers couldn't handle it. Should have gotten a less powerful PS or Gecko drivers. I believe both of the Geckos I mentioned above are rated up to 80V as well. I heard those can handle anything thrown at them.
- What do you think is the best solution here?

Shaking problem
The motors are rated at 6 Amps max so I had the DIP switches on the drivers configured for 5.7Amps (peak). Also on the switches, I had these configured for 2000 pulse/rev microstep resolution and its the configuration setting I have in Mach 3. I was under impression that's what I needed for these motors. Sorry if I'm asking obvious things,..still learning. I assume if I increase the micrsotep in Mach3, I would need to set the DIP switches accordingly? I'm going to try increasing it as per your suggestion to say, 3200 ( I believe that's the next highest setting available in DIP switch configuration on the drivers (see attachment)

Another question - aside from upgrading the drivers, do you think going with a better set of motors would help? Or maybe NEMA 34 motors just too powerful for this router?


Let me know if you have any other suggestions.
Thanks for the help.

- Dex

[ger21]

Your original post said you had an 80 volt power supply?

[ger21]

Or maybe NEMA 34 motors just too powerful for this router?

Not too powerful, but maybe too big. Larger steppers tend to not run as smooth at low speeds as smaller motors, so a smaller motor may run smoother, but it's hard to say.
Is the machine losing position when you cut something? I'm not sure I see what exactly the problem is. If it's not losing position, then the only issue is maybe a little resonance? Adjusting some Mach3 settings may make it a little smoother.
I see you have the camera showing the machine frame shaking. That's normal. You frame needs some diagonal bracing to stiffen it up.

Going to 1/16 microstepping (3200 steps/rev) may also make it a little smoother. Yes, you need to change both the drive settings and your steps/unit in Mach3.

[ModMatters]

You're right ..I meant to say the load is under 60V to the motors not the drivers...so its right around 80V to the drivers. I'm not sure if I can buy some kind of step-down regulator to drive either 60V or 72V to the drivers. Don't want to spend another $150-200 for yet another PS.

To answer your question about position - I've measured several times and it does not lose position. Its just way too much shaking for the router. I will try adjusting the settings as per your suggestion. I did add several diagonal braces (for the corners) and even bolted the bottom feet into the floor - in an effort to reduce the shaking - which did absolutely nothing! After that i thought maybe rigidity is not the main issue...However maybe I should still try getting something very heavy to put underneath the machine...some kind of concrete material to make it more rigid. It just sucks that I have to go through all these issues. I've seen guys with the same machines without all this shaking trouble and their movement smooth like butter:)

Hope the higher settings will help. Will try and report back.

Also, do you think getting different Nema 34s or smaller ones could help with the resonance issue? Is there any type you can recommend which do not have this high resonance?