Y+ wavy cut w/ odd harmonic/vibration. Mach3 need ideas pls

[Countryguy]

Hoping someone can advise on other things to try/inspect next:
Recently had (over a few months time of occasional use) cuts became progressively wavy. Seemed to just get worse and worse rapidly in X and Y. This is a direct drive setup. A PrecisionPlasma iPlasma table from 2013. (used occasionally and still like new). Everything is square. no crashes. etc. It is an iPlasma table from 2013 from PPLLC. Pics of cut quality also in doc.

https://docs.google.com/document/d/1Jvp ... sp=sharing
PICS A and B were as of Sat when at worst. Pic C. Was today after tearing down over Sunday and rebuilding.

Effort taken: Called Support @ candcnc. tech noted that most things w/ wavy cuts was often hardware related and start there. I took X , Y and Z apart off the gantry. Inspected and tightened and adjusted everything I could. It did need attention IMO. Motors and gears were taken off and everything was re-assembled. Cuts are much better (Pic C), but Y+ cuts still really are nasty! (in Pic C, edge up you can see it).

Today, While cutting, when it hits the Y+ move you can see the entire torch just stat bobbling like pendulum. The sound is harmonic too. Y- is minor, but you can feel it there somewhat.. As a test, when setting to .06 over table/steel sheet and running air @ 70psi I just move the torch via keyboard. (no fire). and you can feel it.. almost like the stepper is the source when you hold onto it? I did put on a magnetic break-away torch mount. I used a c-clamp to ensure that was not bouncing.

Just looking for some thoughts on what to dig into next? Should I try some different stepper acceleration or tuning? (X/Y set to 1018.59/ 500 / 35) Value of 2 on the two settings for the pulse on this screen as well. Reading about stepper tuning but now sure if that can help rule things in or out?

Thanks in advance. I know it's old! Hoping someone can offer a suggestion on what to try next or some diagnosing steps.

[acourtjester]

First off what brand of Plasma are you using 70 PSI seems low. It is a little hard so say about your stepper tuning due to the gearing of your table, my X is close to yours but slower are 350 and 50. Since you have checked the drive system what about the guide bearings and how they are adjusted or the surface they ride on. Another thing is to make an adapter to hold an ink pen so you can do testing without cutting metal.
It needs to have a small spring loaded action so you drive the Z down to have pressure on the pen tip but can move up/down slightly to follow the surface of the paper when moving. Your images show a tight circular motion, you may have a power supply that is not regulating well and have a AC ripple and not a pure DC voltage to the driver. You say the Y+ is bad and the Y- is not as bad the difference is the direction signal is 0 volts and +5 volts. You may not have a strong enough signal to give a solid Y+ movement. If the wiring is loose enough for you to switch the plugs from the X and Y drivers on the motor output side A+, A-, B+, and B- as a test to see if the bobbling action moves to the X. You may not be able to do this if you have 2 motors for X drive.

[Countryguy]

Thanks!!!! On it and will check some of these. I have a green PowerPlasma50s from Everlast. (all I could/can afford)... If I recall they want/spec 70psi but I can run that up as a test. I ordered new bearings today... just going to replace them. I will check the voltages and ripple. Can record on my o-scope to possible. Thanks for the ideas... exactly what I was hoping for.

[BTA Plasma]

Go to settings and change THC rate to 18

[SeanP]

Go to settings and change THC rate to 18

It took me about 4 yrs before I went low enough with that setting to get rid of oscillation on z axis, now cut from thinnest to thickest all on one setting and that is 18

[robertspark]

Power Plasma 50 is the same as the Rtech Model with manual here:

70 psi denoted as the required pressure

https://www.r-techwelding.co.uk/media/a ... 017-10.pdf

good luck, not got a clue, but watching with interest

[Countryguy]

I'll be working on the table today w/ a meter and possibly my scope ... I wish I had my screens in front of me, but am at work. It's a Mach3/ CandCNC screen set. Is this 18 value ipm? or something else? Just wondering what 'rate' is... is this one of the setup screen input spots? TIA!

Go to settings and change THC rate to 18

It took me about 4 yrs before I went low enough with that setting to get rid of oscillation on z axis, now cut from thinnest to thickest all on one setting and that is 18

[BTA Plasma]

Go to settings and change THC rate to 18

It took me about 4 yrs before I went low enough with that setting to get rid of oscillation on z axis, now cut from thinnest to thickest all on one setting and that is 18

DTHCII takes in quite a bit that needs to be accounted for the THC dynamics however it doesnt have an acceleration factor built in for the Z aixs. So the 18 number is the speed at which the Z axis moves up and down and it works well for many materials. Once you need high speed THC that number jumps significantly but wont work for low speed applications. DTHCV is current and has all the dynamics involved for thin and thick in one speed up and down (For the most applications) however it only works with CommandCNC and variations of the Ubob or Ebob only. All bladerunner boxes can be updated to CommandCNC with Ebob and DTHCV tech.

[Countryguy]

I am soooo happy to report that this issue is resolved. In short- Pulled everything and readjusted. Then on Y+ issue (and some Y-) it seems that I totally missed getting one of the eccentric bushings & its guide wheel tightened up to the frame. As soon as I did that I could feel a big difference when moving the Y motor. Overall There are 8 or so bearings on the Z/Y assy. And I took my time adjusting everything just so.... I also did X and A since it's been 6 years w/o any tweaking.

I did ask Ron about the eccentric guide roller bushings that need to be adjusted. Here is a source if anyone needs it (https://www.modernlinear.com/product/gu ... -bushings/)

So... On another note- Let me tell ya about Mach minor version .062 -vs- .66 or .67 - This unit shipped w/ .67 and I always had odd intermittent problems w/ starts and stops and odd behavior during execution at times - After just a few day's w/ .062 running (noted stable version that others note is to be used)... Maybe it's placebo.... but I swear I see a difference already in stability . ????? Just wanted to mention it.

[SeanP]

It's a Mach3/ CandCNC screen set. Is this 18 value ipm? or something else? Just wondering what 'rate' is... is this one of the setup screen input spots? TIA!

Glad you found the culprit.
Thc rate is on the settings page.

[SeanP]

Go to settings and change THC rate to 18

It took me about 4 yrs before I went low enough with that setting to get rid of oscillation on z axis, now cut from thinnest to thickest all on one setting and that is 18

DTHCII takes in quite a bit that needs to be accounted for the THC dynamics however it doesnt have an acceleration factor built in for the Z aixs. So the 18 number is the speed at which the Z axis moves up and down and it works well for many materials. Once you need high speed THC that number jumps significantly but wont work for low speed applications. DTHCV is current and has all the dynamics involved for thin and thick in one speed up and down (For the most applications) however it only works with CommandCNC and variations of the Ubob or Ebob only. All bladerunner boxes can be updated to CommandCNC with Ebob and DTHCV tech.

Thanks for the info
I must have just hit the sweet spot with z speed and thc rate as thc now works really well on whether it's 25mm, cutting a 50mm dia hole in 115 dia tube/5mm wall (tracks it perfectly) or cutting thin stuff at full speed, I'm very happy with how it's performing.
I can see something as extreme as corrugated wouldn't work though

[Countryguy]

As a follow up to the follow up.... Ended up buying a bunch of new bearings. Intalled 8 total for the Y/Z platform. 6 of them just too wiggly for my likes. New ones had no play or wobble. Just too much loading the past 7 or so years?? Anyway so much better w/ them replaced. Peace!
GC