Machsupport Forum

Mach Discussion => General Mach Discussion => Topic started by: Davek0974 on April 25, 2014, 05:42:44 AM

Title: Controlling THC?
Post by: Davek0974 on April 25, 2014, 05:42:44 AM
For those of us not fortunate enough to have an embedded THC system, i.e. we are using simple boxes like the PromaTHC which only output up, down & arc good signals, is there a way to control THC within Mach3 Plasma?

I have got two macros - M10 & M11 which contain one line - EndTHC() or StartTHC(), I used M10/11 as they seem to run without causing a glitch in axis movements.

In Sheetcam, we have new cutting rules to play with, I have one which turns off (supposed to) THC when it starts a small circle and back on after.

However, when the code is running, you can see the Z motor moving the torch when it is supposed to be stationary while cutting the circles.

The THC Led on the Mach screen stays on continuously regardless of the M10/11 issued, not sure if that is right or if it is indicating that the macros are indeed ineffective?

Is there a working method of doing this or have I missed a step out?
Title: Re: Controlling THC?
Post by: stirling on April 25, 2014, 06:18:11 AM
M10 & M11 are in-built reserved macros - you can't re-program them. They are designed for laser users and turn on and off designated outputs upon axis movement. It doesn't matter what you put in the TEXT files M10.m1s or M11.m1s - it won't be run.

User macros start at 100
Title: Re: Controlling THC?
Post by: Davek0974 on April 25, 2014, 06:21:15 AM
Ah, bugger  ;)

I tried higher number macros but they created a serious glitch in the movements, however, with the new rules system I have more control so will have another go at them.
Title: Re: Controlling THC?
Post by: Davek0974 on April 25, 2014, 06:43:42 AM
Moved to M101/102 and it seems to be ok now, the LED goes on/off as well :)

With the new Sheetcam rules, the pauses in movement do not seem to occur as we now have more control over when the M code is inserted.

thanks for the help
Title: Re: Controlling THC?
Post by: stirling on April 25, 2014, 06:47:12 AM
The "rules" are called the post processor or just the post.  ;)

Macro pauses shouldn't be an issue for what you're doing as you're doing it BETWEEN cuts not DURING cuts.
Title: Re: Controlling THC?
Post by: Davek0974 on April 25, 2014, 06:58:49 AM
AFIK, the new rules are not connected with the POST, they are a feature built into the actual main body of Sheetcam, the THC codes in the POST need to be disabled to make them work correctly :)
Title: Re: Controlling THC?
Post by: stirling on April 25, 2014, 07:17:49 AM
Sorry but that makes no sense to me - the pause for an M code is down to how Mach executes them. SCam has no control over that. Wherever you put an M code - it will always cause a slight pause. Whether that pause is an issue depends on where it is. If it's DURING CV'd feed movement then it will affect movement - If it's BETWEEN rapid and feed movement, or between exact stop feed movements the pause won't matter. You could always put M codes in any of these mentioned positions. I'm still using SCam 4.0.19 and I can turn THC on/off whenever I like with no pauses during cutting. YMMV.
Title: Re: Controlling THC?
Post by: Davek0974 on April 25, 2014, 07:52:04 AM
Hmm, I'm on V6.01, maybe a change?

Anyway, it seems to be working so all OK.

Dave
Title: Re: Controlling THC?
Post by: Davek0974 on April 25, 2014, 09:08:27 AM
. I'm still using SCam 4.0.19 and I can turn THC on/off whenever I like with no pauses during cutting. YMMV.

Would you care to divulge how you do that?

Anyway, as I'm still learning here, as an experiment, i tried the job below, picture attached.

N0010 (Filename: Test 1.tap)
N0020 (Post processor: Mach3 THC with scriber 2.scpost)
N0030 (Date: 25/04/2014)
N0040 G21 (Units: Metric)
N0050 F1
N0060 G53 G90 G40 G64
N0070 (Part: Test 1)
N0080 (Operation: Outside Offset, 0, T2: 1.5mm Steel, 30A, Std Tip, 103v)
N0090 G00 X41.3478 Y30.1053
N0100 G28.1 Z3.00 F800.0
N0110 G92 Z0.0
N0120 G00 Z3.9000
N0130 G92 Z0.0
N0140 G00 Z3.5000
N0150 M03
N0160 G01 Z1.0000
N0170 M101 (THC Off) (On arcs)
N0180 G03 X50.9478 Y20.5053 I9.6000 J0.0000 F2310.0
N0190 M102 (THC On) (On arcs)
N0200 G01 X72.6444 F3300.0
N0210 M101 (THC Off) (On arcs)
N0220 G02 Y9.4947 I14.3556 J-5.5053 F2310.0
N0230 M102 (THC On) (On arcs)
N0240 G01 X29.3556 F3300.0
N0250 M101 (THC Off) (On arcs)
N0260 G02 X0.5522 Y9.7414 I-14.3556 J5.5053 F2310.0
N0270 M102 (THC On) (On arcs)
N0280 M101 (THC Off) (On arcs)
N0290 X9.7414 Y29.4478 I14.4478 J5.2586
N0300 M102 (THC On) (On arcs)
N0310 M101 (THC Off) (On arcs)
N0320 X29.3556 Y20.5053 I5.2586 J-14.4478
N0330 M102 (THC On) (On arcs)
N0340 G01 X50.9478 F3300.0
N0350 X52.4478
N0360 M05
N0370 G00 Z10.0000
N0380 X0.0000 Y0.0000
N0390 M05 M30

It's a dog-bone shape, so I presumed that THC would be off for the curves and on for the straights, this sort of made sense. However, as expected there is a pause at the end of the lead-in (unexpected but i can understand why) then one at each start/end of arc. The odd bit is the two extra pauses on the left hand arc, these made no sense and it seem sheetcam has thrown a wobbly at this point so i will pop it over on their forum too.

So, due to my lack of knowledge, is this shape possible with THC on/off or should it just be kept off and fingers crossed???
Title: Re: Controlling THC?
Post by: stirling on April 25, 2014, 11:12:42 AM
. I'm still using SCam 4.0.19 and I can turn THC on/off whenever I like with no pauses during cutting. YMMV.

Would you care to divulge how you do that?

Maybe slide the finger off that trigger Dave - don't want to shoot yourself in the foot. Right?

Re-read my last post - it's all right there.

It's a dog-bone shape, so I presumed that THC would be off for the curves and on for the straights, this sort of made sense.

Why? You've mentioned this before about turning THC off for arcs - why? Generally speaking unless you're doing small holes - just leave THC ON.

The odd bit is the two extra pauses on the left hand arc, these made no sense and it seem sheetcam has thrown a wobbly at this point so i will pop it over on their forum too.

Look at the code - lines 250 to 320 - it's made of 3 arcs. Between each, you turn THC ON and then immediately OFF again.
Title: Re: Controlling THC?
Post by: Davek0974 on April 25, 2014, 01:17:04 PM
Sorry, your answer was a little contradictory, you said you could turn the THC on or off whenever you liked, but also said it would only work smoothly at certain points I.e. When not in CV.

Better to have said you can only turn it on/off at these points without upsetting motion, it's not the same as being able to do it whenever you want :)

As for the code being three arcs, it is something to do with sheetcam, les newel over there is looking into now as he was baffled too,.

I have found that my machine is less impressed with holes sub 20mm but also know now it is connected with acceleration and CV so I will be going back to the basics next week and retuning the axes from scratch to see if I can get her singing a better tune, then I can forget about flipping the THC off and on.

Anyway, my foot is intact and I've learnt a little more, as always thanks for your help, it really is appreciated.
Title: Re: Controlling THC?
Post by: BR549 on April 25, 2014, 06:55:05 PM
Dave do yourself a favor and stop fiddling with the thcon/off on arcs.

Stirling is doing his best to help you (;-) try not to bite the hand that feeds you.


You do NOT needed it 99% of the time. Mach3 will compensate on the slow down in the arc BY ITSELF. Everytime you add the Macros for the THC on/off you are monkeying with MACH3 ability to do a SMOOTH CV. AND a smooth CV it the KEY to a good Plasma cut.

Leave the CV setting to the STOCK mach 3 settings do NOT turn on any values for CV let the internal settings HANDLE the toolpath. THEN learn to set up proper cut parameters of power/speed/cut height for a good cut.

IF it does not work correctly after that you have a problem with table /drive mechanics and Vel and accel problems. Mach3 WILL work correctly if you table is built correctly and tuned correctly.

But that is just based on about 100 zillion cut inches with plasma and Mach3,  your mileage may vary.

(;-) TP

Title: Re: Controlling THC?
Post by: Davek0974 on April 26, 2014, 03:34:13 AM
Please believe me when I say I really am not biting anyone's hand off, I'm not moaning or criticising anyone, I am just trying to learn as much as I can, and unfortunately that means asking questions.

I really do appreciate all the help that has been offered here, it's been most helpful, really. :)

I do know now that I need to retune my acceleration parameters and will do so this week, the CV stuff I think is all bog-standard (I think), I use G64 at the start of a program and I think the no-cv angle is set at 89 degrees in config, I don't know if that should come out though?

The other cv settings are all blank.

Once again, thanks to you guys,and if I come across as hand biting then I apologise.
;)
Title: Re: Controlling THC?
Post by: stirling on April 26, 2014, 04:59:45 AM
Dave - Before we do the group hug I'll just get this out of the way ok.

Sorry, your answer was a little contradictory, you said you could turn the THC on or off whenever you liked, but also said it would only work smoothly at certain points I.e. When not in CV.

Better to have said you can only turn it on/off at these points without upsetting motion, it's not the same as being able to do it whenever you want :)

IMHO Terry is THE plasma guru here but for whatever reason it looks like you're generally stuck with me at the moment. However, I'm not your hired help. If you're going to chip at me and even advise me on how I should phrase things I'll just call it a day here.

Now... onwards...

Yes - CV (and therefore accel and therefore rigidity) are the keys to happiness. I'm pretty sure Terry and I have said this already. I'm think I've also said that you shouldn't need to "tune" CV at all - maybe it was to someone else.

With ref. to No CV on angles > 89: NO - don't do this. You don't want to restrict CV at all.
Title: Re: Controlling THC?
Post by: tripleblack on April 26, 2014, 06:57:41 AM
i use the m10 m11 macro to turn off and on the thc with the cutting rules in sheetcam.i use a dpdt relay that allows the thc to be used with a joystick for manual control , ei oxyacet flame cutting or auto for plasma. the thc control is a lcthc from candcnc.added activatesignal(output2) to m10   and deactivatesignal(output2) to m11.no hesitation in the disabling of the thc when cutting even at speeds of 240 ipm. i set up the cutting rules to slow at angles of +45 degrees and .5"
and m10. .25" out of the corner to turn on thc with m11.the relay is stopping signal to mach inputs when turned on.
Title: Re: Controlling THC?
Post by: Davek0974 on April 26, 2014, 07:04:39 AM
Dave - Before we do the group hug I'll just get this out of the way ok.

Sorry, your answer was a little contradictory, you said you could turn the THC on or off whenever you liked, but also said it would only work smoothly at certain points I.e. When not in CV.

Better to have said you can only turn it on/off at these points without upsetting motion, it's not the same as being able to do it whenever you want :)

IMHO Terry is THE plasma guru here but for whatever reason it looks like you're generally stuck with me at the moment. However, I'm not your hired help. If you're going to chip at me and even advise me on how I should phrase things I'll just call it a day here.

Now... onwards...

Yes - CV (and therefore accel and therefore rigidity) are the keys to happiness. I'm pretty sure Terry and I have said this already. I'm think I've also said that you shouldn't need to "tune" CV at all - maybe it was to someone else.

With ref. to No CV on angles > 89: NO - don't do this. You don't want to restrict CV at all.


It wasn't meant as a chip Stirling, that's why I put the smiley face on it, I was trying to explain how I misunderstood it that was all.

Re the CV angle I will certainly clear that on Monday and then retune my machine.

Thanks
Title: Re: Controlling THC?
Post by: BR549 on April 26, 2014, 05:20:20 PM
Dave the important part is STOP fiddling with the THC ON/OFF macros,  for most of your cutting you do NOT need it.

Even on small circles here I do NOT use it, don't need to, mach3 will cut just fine. The anti dive will take care of it.

(;-) TP
Title: Re: Controlling THC?
Post by: Davek0974 on April 27, 2014, 03:40:40 AM
Point taken, I need to stop over complicating matters, my fault entirely but valuable lessons learnt.

Many thanks for putting up with me :)

I really feel a full and proper instruction manual would benefit many users setting out, but I am fully aware that creating one would be a mammoth task. I know there are a few on the 'net but none fully explain stuff like CV, THC, side effects of low acceleration settings etc.


BTW, if I need a small hole in thick material, it needs to slow down, I have found 70% seems to work but as that is programmed in sheetcam! how does anti-dive deal with that?

As far as I know there are no hidden auto-slowdown features in Mach, it just does what it's told.
Just wondering.
Title: Re: Controlling THC?
Post by: stirling on April 27, 2014, 07:38:51 AM
BTW, if I need a small hole in thick material, it needs to slow down, I have found 70% seems to work but as that is programmed in sheetcam! how does anti-dive deal with that?

IMHO THC has pretty much no value on small holes - in fact in my experience it causes more problems than it ever solves. Remember THC is there to cope with the changing height of the metal. Almost by definition - small holes - don't cover enough metal to see any particular change in height. Add to that the fact that THICK metal is going to be even LESS prone to changes in height over short distances and it becomes clear that THC brings little if anything to the party.
Title: Re: Controlling THC?
Post by: Davek0974 on April 27, 2014, 10:31:24 AM
Yes, I can fully understand that, but what if you have a job with small holes plus large cut areas too?

My guess is that I would separate the holes into another layer in sheetcam, do the THC off and speed reduction business and then do the other features as a standard cut at normal speed with THC.

That I think is correct, but falls apart when you get a job like the dumbbell shape I was messing with, a long straight where I guess you want THC that then blends directly into small near-circles - you can't turn the THC off for the circles without a macro glitch but as it needs to be slowed down to cut, the anti-dive will not function?

These are the questions that cause me to pose questions because I can't answer it :)
Title: Re: Controlling THC?
Post by: stirling on April 27, 2014, 11:14:22 AM
No particular need for a separate layer for small holes. Remember turning THC ON/OFF BETWEEN cuts is not an issue. Turning THC ON/OFF DURING a cut usually IS an issue.

LOL - yes your long dumbbell with small circular ends could pose that problem. You don't maybe think you think too much do you Dave?

Of course when you have that great accel this sort of problem will magically disappear anyway. (hopefully  ::))  ;D

Ian
Title: Re: Controlling THC?
Post by: Davek0974 on April 27, 2014, 11:49:21 AM
Of course, yes, got it now.

Lol! Yes I do tend to think a lot, it's just the way I am, when faced with a new task-plasma CNC for instance, I like to try and gain answers before getting into a situation where that answer is needed.  At least you too can see how a dumbbell shape or similar could be an issue :)

Hopefully I can significantly improve things by tuning ;)
Title: Re: Controlling THC?
Post by: stirling on April 27, 2014, 12:08:38 PM
Remember your dumbbell shape is not "awkward" because it's particularly special in having small circles, it's just an example of a shape with tightish turns. ANY shape that requires sharp direction changes is going to need good accel. I know I keep harping on about the accel but it truly is the key.

Poor accel causes larger changes in cut speed. ANY change in cut speed will change the voltage across the arc. That change in voltage will be interpreted by your THC as a HEIGHT change. That's what causes dive. That's just how it works. Yes THCs use various methods to try to mitigate this but the plain fact is that you're better off not taxing them too much in the first place.
Title: Re: Controlling THC?
Post by: Davek0974 on April 27, 2014, 12:39:20 PM
Thanks again, I will tune for as much acceleration as possible without losing steps or shaking the table to bits ;)
Title: Re: Controlling THC?
Post by: BR549 on April 27, 2014, 04:36:38 PM
Dave somewhere in your brain is STUCK "You have to slow down on small arcs"  WRONG Cutting with a plasma is dependant on consistant cut speeds and heights.  When you slow down you are altering those constants.  

NOW a fact to remember . Mach3 most times cannot maintain constant feedrates on short arcs. It is a Physical problem with the drives accelleration rates not being able to keep up with the required acceleration between 2 or more short points. There is physically not enough room to do it at the Drives ability to do so. SO now mach3 has automatically slowed down compared to the called feedrate. THAT is where antidive kicks in. WHEN it does slow below requested feedrate MACH3 will shut OFF the THC to prevent torch dive. When the System gets back up to speed it will cut the THC back on.

NOW you talk about cutting small circles in thick plate. THE same applies lets say you are cutting 1/2 thick steel plate. I cut it here at 30Ipm @ 60amps AND I cut everything at that feedrate as THAT is what the torch wants for a smooth cut in that material. NOW a smooth cut is a smooth cut reguardless if it is a straight line or an arc. NOW if the machine can match the accel needed for a particular arc then it cuts the same. IF it gets too short for the machine to maintain a consitant rate then the machine rate will be lower as it just cannot physically do it. SO mach3 slows down and that will change the cut parameter and cause the torch to dive. AND that is where the anti dive kicks in and stop it from diving too low. The quality of the cut will be slighty different in those arc because ONE of the parameters has changed, "Speed".

It will ONLY Be a minor change and it is what it is . UNLESS you have a high END plasma that can auto control machine speed AND torch parameters ON THE FLY you will have what you have.

I spent a LONG time automating an older Plasma torch to have auto control over the power and air settings. Controlled it all automatically from mach3. It would compensate everything on the fly. In the end the overall cut quality 95% of the time was NOT a bit better than NOT having it on. It was a waste of time and energy for "WHAT" we are cutting (Fun doing it though).

SO I suggest you set your max Vel to something reasonable and LEAVE IT ALONE. Then tune the Accell for as FAST as it can react without loss of steps. THEN spend the time to develope a parameters table for your cutting based on YOUR MACHINE. Keep lots of notes. Soon you will find the sweetspot for YOUR machine. AND you will laugh at yourself for worrying about so much.

Then you can have fun at what your plasma can do for you as it is only limited by you imagination to create something to cut. AND that world is EXTREMELY large as to what you can get into and have fun at the same time.

Just another thought is with MACH3  using the THC control thru Mach3 it is NOT fast enough to keep up at HIGH speeds anyway so there is NO need to go there (;-)

Just some thoughts, (;-) TP





Title: Re: Controlling THC?
Post by: BR549 on April 27, 2014, 04:37:57 PM
Got 2 posts for the price of one,(;-) TP
Title: Re: Controlling THC?
Post by: Davek0974 on April 27, 2014, 04:48:20 PM
Fantastic, now that really made sense.

Many thanks
Title: Re: Controlling THC?
Post by: Val on September 06, 2014, 05:09:56 AM
I'm still using SCam 4.0.19 and I can turn THC on/off whenever I like with no pauses during cutting. YMMV.
How do you do that? Please do share. Sheetcam allows you to use rules. In their cutting rules tutorial on youtube looks very simple but in real life doesn't work. All I got is a jerk in movement right where the THC should go off. And on for that matter. They use M998 and M999. What is the code? M101/102 work? Do you have to write a macro for them? How do you do it whenever you want?
Thank you
Title: Re: Controlling THC?
Post by: Davek0974 on September 06, 2014, 05:51:51 AM
Since this thread I have upgraded to a better THC from CandCNC and it's way better at controlling things. Turning on and off during a cut is simple and has no effect on motion.

Also as mentioned, get the acceleration up, way up, push it as hard as it can take and things become much simpler.
Title: Re: Controlling THC?
Post by: Val on September 06, 2014, 06:41:01 AM
Since this thread I have upgraded to a better THC from CandCNC and it's way better at controlling things. Turning on and off during a cut is simple and has no effect on motion.

Also as mentioned, get the acceleration up, way up, push it as hard as it can take and things become much simpler.

I"am happy is simple to you, to me is something I don't know how to do. Can you explain haow you did it?
Title: Re: Controlling THC?
Post by: Davek0974 on September 06, 2014, 08:02:45 AM
There are two codes to turn THC off in mach3, they are listed in one of my other threads about THC control.

To use them I had to create custom macros, I think I used M10 and M11, trouble is my machine is at work and I can't remember what was in them but it is listed somewhere here in one of my threads. I think M10/11 did not cause a delay or glitch in mach movement.

To use the macros I created two code snippets in sheetcam one off and one on, these were then called from various cut rules.

It all worked well but the new system has made much of it pointless as it is completely different and has it's own on/off codes.

I will see if I can find the codes...
Title: Re: Controlling THC?
Post by: Davek0974 on September 06, 2014, 08:48:35 AM
It's  the start of this thread that we are in now!

It was M101/102 not M10/11
Title: Re: Controlling THC?
Post by: Val on September 06, 2014, 09:27:59 AM
There are two codes to turn THC off in mach3, they are listed in one of my other threads about THC control.

To use them I had to create custom macros, I think I used M10 and M11, trouble is my machine is at work and I can't remember what was in them but it is listed somewhere here in one of my threads.


I will see if I can find the codes...

Thank you so much. You explained it very nicely. The only thing now is the macros.  I tried with M101/102 but without the macros all they do is to pause the machine for a fraction of a sec.  If you could find those macros and explain what to do with them so that the M codes call them, it would be great.
Title: Re: Controlling THC?
Post by: Davek0974 on September 06, 2014, 09:49:13 AM
All that is in M101 is EndTHC()
M102 has StartTHC() in it.

The rest is down to using sheet cams cutting rules to call those macros.
Title: Re: Controlling THC?
Post by: Val on September 09, 2014, 10:49:16 AM
All that is in M101 is EndTHC()
M102 has StartTHC() in it.

The rest is down to using sheet cams cutting rules to call those macros.

thank you. you're a life saver.
Title: Re: Controlling THC?
Post by: cwalker1960 on September 19, 2014, 04:03:20 PM
not the same topic exactly,, but is there a screen , or a way to add z axis (torch height control) speed % up and down buttons to the screen as opposed to having to go into the xml file to change it ... I get the z thc speed set to where it isn't pogo ing up and down and then after changing materials thicknesses and speed rate  it's moving too slow to avoid collision.. just wish there was a simple speed % up/down button on the screen instead of having to modify the xml file.
Title: Re: Controlling THC?
Post by: Davek0974 on September 22, 2014, 02:03:30 AM
You could try a different screen set, on my last one the THC rate was on the main screen.
Title: THC Speed setting below 5%
Post by: revaebd on May 09, 2016, 11:20:57 AM
I need to set the "THC Speed" on the Plasma screen set to 0.5%.  If I change in in the Plasma XML, it will be what I entered when Mach3 first opens.  But if I try to change it on screen, it revert to a min speed of 5 or greater.  Somewhere the screen set is prevented from going lower than 5%.
Title: Re: Controlling THC?
Post by: robertspark on May 09, 2016, 02:17:55 PM
It is inbuilt within Mach.

The way to do this is to lower your z axis rapid speed setting in in/min or mm/min under the motor tuning setting.

Rob
Title: Re: Controlling THC?
Post by: Davek0974 on May 09, 2016, 02:27:27 PM
What Rob said.

I tried it with insane Z speeds, makes little difference on my setup, so backed it off to around 1700mm/min i think my THC rate is around 20%
Title: Re: Controlling THC?
Post by: robertspark on May 09, 2016, 02:34:33 PM
Really what you are looking for is range... If 20% works for everything you do, great, if you need to adjust the setting for thick and thin stuff then you really want some range to the adjustment, unfortunately the trade off is that you won't have phenomenal z axis rapid speed worthy of braging to your friends at the bar...  But it will work great, and the only time you use the rapid z axis speed is after touch off up to Pierce height, and a clearance move or safe z move after cutting.
Title: Re: Controlling THC?
Post by: Davek0974 on May 09, 2016, 02:41:10 PM
Or cutting very thin sheet where a slow Z will not track in time as the sheet warps etc.

In use, i never adjust mine, just set and forget.
Title: Re: Controlling THC?
Post by: robertspark on May 09, 2016, 03:17:46 PM
Dave, have you got a plunge rate for your zaxis.

I've now got a pmx45, 230v too.

After pierce where it moves down to cut height have you read anywhere or are aware of a recommended plunge from pierce to cut height, the reason why I ask is because of my fiddling with sheetcam post processors (no I ain't broken it yet), I noticed that some use the cut feedrate to drop from pierce to cut, whilst this may be OK for thin stuff with fast motion it may lead to an overcut a start (divot) where you have pierce delay and then a slower than it needs to be drop to cut height before motion.

(May be over thinking something here.....)
Title: Re: Controlling THC?
Post by: Davek0974 on May 09, 2016, 03:57:22 PM
I'm currently plunging at 2400mm/min this is the max rate I have set in motor tuning for the Z axis.

I don't think I have ever read a recommended rate, the only recommendations I have seen are ' as fast as possible' as a very slow plunge will increase pierce time and cause divots.

I have my M03 macro set to ActivateSignal instead of DoSpinCW as it operates faster, also my THC ArcOk current is set to a low value so it triggers as soon as possible.
Title: Re: Controlling THC?
Post by: beefy on May 09, 2016, 07:27:10 PM
The way I look at it, once a hole is blown through (pierce delay), there's no need to hang about. Just get down to cut height ASAP and move into the leadin / cut.

I would hazard a guess that on thicker steel there could be some advantage to piercing with a mixture of pierce delay and slow plunge rate (the move from pierce height to cut height). For instance, on thick steel, as the pierce progresses the distance from torch to metal "surface" is increasing. On a 30mm plate let's say you start a pierce at say 5 or 6 mm then by the time the pierce has blown out metal half way through, the torch to metal distance is now about 20mm. Perhaps a slow plunge rate starting at that point is an attempt to get the torch a bit lower/closer to the metal "surface". Of course it can only go as low as the cut height.

Like I say though that's just a calculated guess as to how a slow plunge rate could have some use. Personally all I've ever done is blown a hole then moved to cut height at max Z speed (Sheetcam plunge rate).

Keith.
Title: Re: Controlling THC?
Post by: Davek0974 on May 10, 2016, 02:26:36 AM
My preference is to blow the hole then get down ASAP, every time, I would rather control pierce with pierce delay as its controllable.

In an ideal world the change from pierce to cut would be instant i think.
Title: Controlling THC below 5%
Post by: revaebd on May 10, 2016, 10:24:49 AM
Rob,
 I was not wanting to change the motor tuning (speed) setting.  My "height detection" software slows down to a crawl if I do it that way.  It will hold my 1% setting set in the XML file if I never try to change it on-screen. 

If I understand your reply... the fundamental Mach code has this valve screened at 5% or higher.   Too bad... it is what it is, I guess.
Title: Re: Controlling THC?
Post by: robertspark on May 10, 2016, 10:37:38 AM
What height detection software?

Is it just a g31 or g28.1 macro for touch off?

What z axis screw pitch are you running with what stepper ampage and voltage?

Rob
Title: Re: Controlling THC below 5%
Post by: revaebd on May 10, 2016, 10:59:59 AM
Rob,

The "height software" I found and edited to suit my  needs.  I have a very fast and robust Z drive. I like it that way.  The motor is running on 60V, a couple of amps with a 1605 ball screw.

The "height software" detects the metal, moves to transfer height, turn on torch, pierces , them move to cut height.  This works fine.  If I slow down Z full speed,  it increases my run time a lot.  On short cuts (artwork), I spend more time in that software than running the cutting Gcode.