CNC motor acceleration tuning in Mach4 to reduce vibrations that degrade cut and laser quality

[@CorbinDunn]

Awesome, thanks Jim! I appreciate the help and advice you gave me on Facebook and the Avid Forums.

[@Sehast]

Nice job, Jim. Now I know how those CV wizards in Mach 4 really work. Looks like you have found the sweet spot on the Avid for the work that you do. I don't think there is much more you can do to reduce vibration using the Avid stock components. However, if you want to improve performance I have found the going to servo motors makes a significant difference. In my case I used Clearpaths as almost drop in replacements for the NEMA 34s. When they are properly tuned much higher acceleration values can be used with less resulting vibration because the motion step function response is commanded to match the exact mass characteristics of the axis with optimized damping.

[@JNWoodworks]

Thanks for the input, I'll have to check out their documentation. I've got good enough performance now (I don't have to make money on my machine, so the extra execution time is ok for me) so I probably wouldn't switch motors (unless I need a fun project), but its always interesting to see how others solve the same problem.

[@Warp9TechDesign]

Excellent video Jim, thank you so much for making it! The CAM program has no idea what hardware you are using (and Mach doesn't really either). After you build the hardware as best as you can, it is all a tradeoff between speed and accuracy, and it is up to you as the operator to adjust your acceleration settings and CAM settings accordingly.

[@JNWoodworks]

Thank you, and very well said on the second part.

[@AnotherMe890]

Well done Jim, thank you!

[@bstanga]

Man that Last Supper looks great! where did get such a fine stl as that. lol

[@JNWoodworks]

Some cool guy in LA

[@smallpoul]

Just want to say a big big thanks to you Jim for taking time to make all these videos.

[@JNWoodworks]

Thank you, glad you find them helpful.

[@mudtang89]

Good stuff. Was wondering about this topic. Thanks!

[@robertpeters9438]

I'd suggest a cable, pulley, and counterweight system and motor two times what you otherwise would need. The counterweight will offset your vibrations. No CNC experjence, but engineering experience.

[@imqqmi]

There's a couple things at play, the mach path planner has some flaws in constant velocity mode (as do any other as it's a trade off) and the controller and software that you use. It will cut corners at higher velocity and lower acceleration. I don't know if you can tweak those settings in mach, but on uccnc you can tweak them. I've set acc to 63 i/s² (1600mm/s²) and tweaked the constant velocity settings so that it has both smooth motion and precision at 2000mm/min velocity. The slower you go the more accurate it'll become. If you need perfect accuracy, stop using constant velocity mode and start/stop at each line segmemt (I think it's called stop mode). Also, the gcode generator/post processor makes a huge difference in vibration and jerky motion. I've found that the default settings of vcarve to be way more jerky than fusion360 as the latter adds small radiuses to in and out paths. That way you can greatly speed up the cut compared to vcarve without the machine shaking apart. You can use radius/smooth in/out motions on vcarve but it's a bit primitive, and doesn't always avoid cutting into your workpiece. For uccnc it can't deal well with circle gcode commands in constant velocity mode, I've turned that feature off in fusion postprocessor script. It will then generate line segmemts. It's important to bump up precision so that there's enough resolution for a proper smooth round transition to be generated.

[@JNWoodworks]

Ya, F360 (and others) have much more CAM control and sophistication than Vectric's. However, Vectric users are stuck with Vectric's output, so once you get the Gcode that it gives you, you can just run it, or try to get a little better performance out of it via feedrate and acceleration settings. As for CV, yes, I could make it cut corners at higher speeds and lower acceleration as you said, but the acceleration to make it do so was well below the values I need to run on my machine. So it wasn't really necesary and I see the same results with CV on and off. Other machines could certainly have different results than I see since weight and motor size affect what acceleration you should use.

[@chicoxiba]

Brian never really wanted to touch the TP code and fix the accel/decel disparity on Arts original implementation.. that's why I moved away from m3m4. Adjusting cv angles is only half good, motion is still full of uneven peaks. For me that was the only issue with m3 and m4.

[@roblewisjr2]

Great info in this video. Thank you. You mentioned 3d carving in the beginning. I have a different issue than vibrations, mine is the screen toolpath preview not showing for large 3d toolpaths and the program crashing and shutting down. I have a i7 12700 cpu with UHD770 integrated graphics and 64gig of DDR5 ram. It only happens on toolpath gcode files larger than about 100mb. Smaller than that and the previews look great. Any thoughts on what the problem could be? Thanks!

[@JNWoodworks]

Thats a good question. I went back and looked at all my carves and the biggest file was 28MB, so you are doing some really large ones :-) However, I know people that have done some really big ones and I haven't heard of a file size limit. A great place to ask that question would be in the AVID User Group on FB page (I'm assuming you are using Mach4?). That seems to be plenty of computer. I just checked on the Artsoft forum and there was a coment that the screen toolpath display is very resource intensive so for very large files you may need to turn off the toolpath display to handle that large of a file.

[@Shane-ce9fm]

@JNWoodworks will these adjustments affect wood carvings or do they apply mostly to an added laser?

[@JNWoodworks]

I first noticed the ripples that the vibration caused in Vcarve work with the spindle. I slowed down the feed rate a lot back then to get smoother cuts. Then when I started playing with lasers, I could see the sine waves in the laser line so clearly that it started to make more sense what was going on, and it was much easier to do experiments because the results were much more measurable. So the default settings are fine for typical machining like cutting cabinet parts and stuff where you are running longer vectors. However, once you start Vcarving, 2.5D carving, or lasering, typcially your toolpaths are very short and changing directions all the time and that causes all kinds of vibration if your accelleration is set too high.

[@RichA7CV41]

Jim, I've been binge watching your videos as I'm waiting for my first laser head (PLH3D-XT-50) and I just wanted to say thank you for all your videos and efforts. It's very much appreciated. One thing I'm still trying to figure out is the method for zeroing the laser for x/y. If the Laser is offset from the router, are you just setting an offset in the XY Datum section of the job setup in VCarve? Especially when dealing with combined Router/Laser operations in one job.

[@RichA7CV41]

LOL should have continued my binge watching, you answered it all on your excellent Mach4 Screen video :)

[@JNWoodworks]

Hi Rich, I have a section in my laser screen where I can plug in X/Y/Z offsets for the zero position. The screen is in my Google drive, and I briefly went over the screen in one of my laser videos. So I can use anything for a touch plate reference, like the spindle would work fine. However, I have.put a retractable metal rod on each of my laser bases so that the offset from the road to the laser is constant even when I reattach the laser base. I almost always use the rod with the touchplate and the offset routine to set my Z zero because I get very consistent results on the focus and that is important. However, for Xand Y, I usually just turn on the.laser and jog to where I want zero and set it manually in Mach 4 because that is usually not critical for what I'm doing. You do have to remember how you set the job up in Vcarve as to if you are corner or center referenced in the job.

[@arroff]

great video. Should help. Also I noticed you have a wireless keyboard. I also have one. A RII mini i8+. Can not find anything that tells me how to program it into mach4. I can moe X,Y,Z but that it. Help Please...TY Andy

[@JNWoodworks]

Hi Andy, I did a video on screen editing, and I cover they keyboard shortcuts in there. kzbin.info/www/bejne/bmjYn4CegLRqq5o Take a look at that video, and then if you have any further questions feel free to send me a note an [e-mail]

[@robertpeters9438]

COULDN'T YOU USE A COUNTERWEIGHT ON A DRIVE MOVING OPPOSITE YOUR SMALL FAST MOVEMENTS???

[@JNWoodworks]

In theory, but I don't think that would be practical. That would essentially be building a whole other "anti CNC" just to counteract forces. It wouldn't be too hard to do that under the table to reduce the vibration there, however most of the problematic vibration is up on that gantry, and the last thing you want to do is mount more mass and motors up there.

[@altamiradorable]

Go with Clearpath servos !

[@JNWoodworks]

Some day I might just to see the difference as an experiment, however just lowering the acceleration works great and has little impact on execution time for the type of tool paths I normally run.

[@altamiradorable]

@@JNWoodworks The nice thing about the Clearpath, it's NOT a stepper motor ! You set the parameters in the motor via USB and their software. You set the acceleration, start and stop point. Once connected to your controller, the morot receives commands and move to the position at incredible speed, uip to 800ips. It's really worth the 250$

[@JNWoodworks]

@@altamiradorable Well, I have no need for more speed. The NEMA 34 steppers on the machine will raster my laser at 1100ipm, which is about 900ipm faster than I really want to go (based on laser image quality). Most of the router work I do is Vcarving or 3D model carving, and then laser work, which is all very short vectors with lots of curves, so the motion is almost always in accelleration mode and doesn't reach full speed. So the only reason for me to switch would be for the improved acceleration curve control to reduce vibration. However, I can control that easily by reducing the acceleration values on the steppers with very little impact to the Gcode runtime. So I really don't have much justification to do it other than it would be fun project 🙂 The other concern I would have is that I don't want to replace the control system, I like the ESS and Mach4. I don't think the clearpath SDSK can really optomize the acceleration curves all that well when they are being feed a linear ramp from mach4, so w/o gutting they whole system it wouldn't be much of an improvement.

[@kevinspencer9114]

Hi Jim I am in need help with avid cnc / training .

[@JNWoodworks]

Specific items, or just general questions?

[@kevinspencer9114]

V carve l can pay for you time

[@JNWoodworks]

@@kevinspencer9114 send me a note at [e-mail] and we can talk.

[@ahmedibrahem3712]

Nerd