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Author Topic: Stop CV issues...  (Read 4690 times)

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Offline stirling

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Re: Stop CV issues...
« Reply #10 on: September 13, 2015, 09:48:06 AM »
take a look at line N0360 and N0490 and tell me what you see.

Offline Davek0974

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Re: Stop CV issues...
« Reply #11 on: September 13, 2015, 10:36:36 AM »
take a look at line N0360 and N0490 and tell me what you see.

N0360 G01 X8.171 Y25.365
N0490 X33.009 Y48.108

G01 is missing?

Thats all i can see, i'm way down the learning chain though...
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline stirling

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Re: Stop CV issues...
« Reply #12 on: September 13, 2015, 11:11:30 AM »
No that's perfectly fine.

Sorry Dave - it's actually N0370 etc. and it's not quite what I thought now I've looked closer.

However, I'm guessing it (and possibly some others) are still the cause of your ills. The thing is your toolpath has loads of REALLY short lines joining your "intended" lines to arcs. The one on line 370 is 0.07mm long (where I think ONE of your "blips" is). I'm thinking this is what's tripping up CV with angles >.

NOW - it shouldn't - but I seem to recall REALLY short lines having bad effects sometimes in CV so I'd get rid of them and see what happens.

What CAD/CAM do you use?

Are the 2 "blips" in your photo the only two?
« Last Edit: September 13, 2015, 11:30:20 AM by stirling »

Offline BR549

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Re: Stop CV issues...
« Reply #13 on: September 13, 2015, 01:12:59 PM »
Dave, (;-) It would seem you have an accel issue IF you are getting corner rounding. Plasma depends on a constant as possible cutting rate . Turning OFF CV anywhere defeats the purpose of CV.  I plasma cut just about everyday from 28ga up to 3/4",steel and  aluminum.

A lot of what you are talking about in corners is a THC problem where it is NOT holding the height as it slows down. THAT is a setting you need to play with. Start adjusting the anti dive/corner dive in Mach3.  IF it is to much reduction in vel before it locks then you get a arc that is to low and THAT will angle the kerf . You want the anti dive to lock out before it effects cut quality.

Another issue is using the correct combination of Nozzle, Sheild. air pressure, amp settings, DRY AIR.  This are very important to cut quality as well. Get one part off and the quality goes down the tube.  

with Plasma a LOT can be said out the quality of the Cut file. You are much better of with radiused  corners where ever possible. A sharp intentional corner makes it HARDER for the machine to maintain a constant cutting speed(almost impossible) without rounding. Accel is king with Plasma cutting and well as a very lightweight rigid gantry. Motros are calculated for max acell properties (low inertia High torque) THEN comes speed. Most times steppers have limited RANGE of operational speed where as Servos have a much wider RPM band they can work in.

THCs are another can of worms for most DIY users .  BUT that is a different chapter in the " So you want to be a plasma cutter book ". (;-)

NOW IF your control cannot do transitional changes in Gcode without a HESITATION then you have a Controller problem.  There ARE controllers that do not have that problem. Another chapter in the book.  The trajectory planner has to be top notch and very much in control without hesitations in execution.



I use the STANDARD Mach3 CV with NO adjustments at all. JUST like it comes out of the box and it cuts fine detail very well here. I do a LOT of artsy stuff where DETAIL is an issue.  NOW that siad I also use an alternative cutting speed settings for the very thin stuf <18ga . I am not interested in trying to cut above 200 IPM . There is ALWAYS an alternative cutting solutions to high speed cutting, you just have to find it

You are trying to solve a mechanical issue through software control (;-).
« Last Edit: September 13, 2015, 01:24:48 PM by BR549 »

Offline stirling

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Re: Stop CV issues...
« Reply #14 on: September 13, 2015, 01:51:32 PM »
Terry

Generally I agree with everything you've said.

However - look at WHERE the gouging is happening on the picture. That should have NOTHING to do with slowdown because at that point there shouldn't BE any slowdown.

Of course there obviously IS, which is why I've suggested what I have.
« Last Edit: September 13, 2015, 01:58:59 PM by stirling »

Offline Davek0974

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Re: Stop CV issues...
« Reply #15 on: September 13, 2015, 04:13:10 PM »
Hmm, ok here we go ;D

That file is not my general standard, it's downloaded from the 'net and yes it's pretty ugly when loaded in CAD, thousands of little lines. However, with normal CV on, it cuts perfectly fine - no issues at all, its only when stop-cv is on that the blips show up and there is one every point where it goes form straight to a curve - no slowdown so should not blip.

It's a minor point and i was just playing about looking for improvements.

Yes, I have not fine-tuned the THC yet, it could well be diving unseen, I will have a play with the dive% settings.

So far I only have the 45A consumables for my PM45, I will be getting some 30A ones to try though. The air is passed through a refrigerated dryer so should be pretty good.

Any chance of a pic or two of some examples of your cuts for comparison, some settings maybe ;)
« Last Edit: September 13, 2015, 04:14:52 PM by Davek0974 »
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline BR549

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Re: Stop CV issues...
« Reply #16 on: September 13, 2015, 04:26:51 PM »
OK are ALL the plates the same way ??  I can not see enough kerf detail to tell IF it was coming into the arc or just coming out of the arc ? Which was it. I see 2 defects.

Both appear to be a stall of motion ??  . Does it do the same thing if you set the CV back to box stock settings ?.   never see that here so it appears to be a local event. are you using the LPT version or other ??  What THC ??  Have you tried with the THC off ?? 

Have you reversed the motion to see IF it is an arc direction  problem ? 


(;-) TP

Offline Davek0974

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Re: Stop CV issues...
« Reply #17 on: September 13, 2015, 04:42:57 PM »
I've only cut this one part, using it as a test to check the slot width etc. The whole lot are drawn just as badly though.

No, with CV back on the blips disappear.

This is the LPT version, the THC is a CandCNC Mp3000 DTHC2, not tried this part with THC off yet or reversed directions.

I've attached the whole file incase someone wants a play.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline BR549

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Re: Stop CV issues...
« Reply #18 on: September 13, 2015, 05:00:31 PM »
Dave what version of Mach3 are you running ???  IF the problem goes away when you put the CV back to normal then there is your answer , leave teh CV alone and work on other areas for improvement.  IF you are having rounding problems at those speeds then you need to rethink your settings or motors/drives or gantry design.   (;-)

(;-) TP

Offline Davek0974

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Re: Stop CV issues...
« Reply #19 on: September 14, 2015, 02:23:20 AM »
Hi

can't remember which version, its at home, will check tonight but i do know that the CandCNC plugins and THC only works with one version of Mach.

Yes i can leave it on of course.

The main issue is i think that i done even know what a PM45 is capable of when it comes to internal corner quality, i know it can't be tighter than the radius of the flame but its difficult to know when you can't see what other users are happy with ;) I may be chasing the impossible.

Anyway, thanks all for the info, I will leave CV on as normal and revisit my table settings etc.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives