THC futures for Plasma

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THC futures for Plasma

Postby shad » Sat Sep 24, 2016 12:34 am

As you know, one of the main problems for the torch height control is the need to turn off THC at the corners, at the end of the cut, at the small holes.
Now most of the users use the rules when creating a cutting program in SheetCam or other CAM program. But the rules often do not work properly, especially when they overlap. It is a headache.
If we look at it more globally, we can define the following THC control rules during cutting.

    Turn off THC when machine accelerate/decelerate - I guess this is UCCNC antidive future, but now only for internal THC, no way to send this signal to the external device
    Turn off THC before end of cut - the value of the distance before end can be settable
    Turn off THC on the small holes and down cutting speed - the values of the hole diameter and slowdown feedrate as percents from cutting speed can be settable
    These features must be able to operate for the built-in THC logic and able to have hardware output to the external THC (for example one combined output for this futures and for M205/M206 macros - "OR" logic) .

Balazs,what you think about this?
Also it's will be great to add to the UCCNC CAM module Plasma profile with settable kerf width.
Thank you!
-- Andrew
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Re: THC futures for Plasma

Postby Vmax549 » Sat Sep 24, 2016 1:53 am

You CAN output those signals using teh output triggers. OR you could send those signal via MOdbus or serial com to teh THC

Really no need to turn OFF teh thc on small circles as you would call Antidown when you KNOW there is a small feature coming up..

ON Corneres teh Antidive takes care of that very well

Most of those other features are CAM side features teh controller has NO idea when a small feature is coming up. Teh CAM can see teh whole picture before it writes teh gcode. Teh controller can't

Just a thought, (;-) TP
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Re: THC futures for Plasma

Postby beefy » Sat Sep 24, 2016 7:12 am

Hi Andrew,

Turn off THC when machine accelerate/decelerate - I guess this is UCCNC antidive future, but now only for internal THC, no way to send this signal to the external device
I've suggested to Balazs that in addition to M205/206 having a synchronous output, that any other internal feature that disables THC, also affects the same output. But I have no idea how easy or difficult that is to implement.

Turn off THC before end of cut - the value of the distance before end can be settable
Turn off THC on the small holes and down cutting speed - the values of the hole diameter and slowdown feedrate as percents from cutting speed can be settable

Like Terry said this is normally done in Sheetcam (or other cam). Why would it be better to put it in UCcnc.

Can you give an example of this "overlapping" problem with Sheetcam path rules. I'd be interested in trying to get these problems to happen, always good to know about problems I haven't experienced. I've tried path rules where I have a feedrate change and M205/206 put together in gcode. Sheetcam inserted them correctly and UCcnc implemented them correctly. I injected THC UP/DOWN pulses into UCCCNC and monitored the Z and XY pulse stream with a logic analyser and everything went smoothly when the M205/206 and the feedrate change happened.

Keith.
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Re: THC futures for Plasma

Postby shad » Sun Sep 25, 2016 10:19 am

Keith, you right about addition to M205/M206 having a synchronous output, that any other internal feature that disables THC, also affects the same output. Just will wait new release.
About others futures - yes, this is normally can done in CAM program and it's will be great to add this futures to the UCCNC CAM module.
Two issue in the sheetcam was posted here http://forum.sheetcam.com/viewtopic.php ... light=rule
But this is small part of all issues from my customers. It forced us to write own Sheetcam postprocessor and LUA script (based on the acc/dec, control of the small holes and making hole center marking without moves holes for marking on the separated layer) for generating cutting program. Now it's works perfect.

Terry, now I know, that all THC state LEDs in the UCCNC has 60 msec update time. It makes no sense to read state Of the THC inside plugin and send to the external device. It will be a long delay. Hardware output and M205/206 this is the best way.
Also we always disable THC on the holes less 25 mm diameter and decrease cutting speed to 75%. Holes are cut better.
-- Andrew
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Re: THC futures for Plasma

Postby Vmax549 » Sun Sep 25, 2016 7:30 pm

Hi Andrew , In most of those cases you are asking UCCNC to be able to read a crystal ball and look ahead and find those features in the gcode then TIME teh events for your THC AND it cannot look ahead and report an upcoming feature. It would take a second planner to be able to do it that way. Very few controllers can do that and those that can are running multi processor in order to pull it off.

I have been around CNC cutting for a very long time now. Most of those type features are not needed with low end AIR Plasma. I have tested them all and most did nothing to improve the cutting that I could not acheive by paying attention to the original setup. NOW those fancy features are good for sales. Though Not neccesarily for better cutting.

Plasma cuttings is ALL about constant velocity motion and exact torch height. In the case of a small circle a properly setup antidive will solve that problem for you without you having to juggle teh Gcode around.

Intidive combined with antidown and antiGAP solves 99% of all your problems and still gives you THC control when you really need it to protect teh torchhead.

iF you have a poorly designed machine with slow lazy accelleration you need to FIX teh machine NOT teh software.

Just a thought, (;-)
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Re: THC futures for Plasma

Postby Vmax549 » Sun Sep 25, 2016 7:31 pm

Hi Andrew , In most of those cases you are asking UCCNC to be able to read a crystal ball and look ahead and find those features in the gcode then TIME teh events for your THC AND it cannot look ahead and report an upcoming feature. It would take a second planner to be able to do it that way. Very few controllers can do that and those that can are running multi processor in order to pull it off.

I have been around CNC cutting for a very long time now. Most of those type features are not needed with low end AIR Plasma. I have tested them all and most did nothing to improve the cutting that I could not acheive by paying attention to the original setup. NOW those fancy features are good for Machine sales. Though Not neccesarily for better cutting.

Plasma cuttings is ALL about constant velocity motion and exact torch height. In the case of a small circle a properly setup antidive will solve that problem for you without you having to juggle teh Gcode around.

Intidive combined with antidown and antiGAP solves 99% of all your problems and still gives you THC control when you really need it to protect teh torchhead. TURNING teh THC completely OFF while cutting is never a good thing.

iF you have a poorly designed machine with slow lazy accelleration you need to FIX teh machine NOT teh software.

Just a thought, (;-)
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Re: THC futures for Plasma

Postby shad » Mon Sep 26, 2016 8:49 am

Most of those type features are not needed with low end AIR Plasma. I have tested them all and most did nothing to improve the cutting that I could not achieve by paying attention to the original setup.

Yes, you right.This is true and the main purpose of these futures to protect the torch and nozzle from damage during cutting. This futures are not make cutting more quality, but make more safely.
Everything else is handled by the THC and CNC machine.
-- Andrew
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