THC on or off??

Having an issue with a job and my THC (CandCNC)

I have "min length for THC set to 80mm in SheetCam, I also have a small shapes rule that slows down and turns off the THC then back on after.

The part i am fighting is a detail of a dogs ear - a sort of U shape, cut all the way round but on the return path the scrap is burnt away as the gap is only about 2.5mm wide so I really want THC off as the torch will (and does) dive which trips the limit switch.

Despite have the THC off on both min length and small shapes rule, it still triggers, dives and trip the limit. Baffling and really annoying. :wink:

Here is the code, is the THC on or off for the cut??

N0010 (Filename: test.tap)
N0020 (Post processor: DTHC-HYT-TAP-rev11B With Pauses.scpost)
N0030 (Date: 15/05/2017)
N0040 G21 (Units: Metric)
N0050 F1
N0060 G53 G90 G40
N0070 (Part: Labrador 1 Bracket 300mm)
N0080 (Tool number: 106  Distance between Touch-offs: 0  Feedrate: 4100) 
N0090 (Preset Volts: 110)  (Suggested Tip Size: 45 ) (DTHC Delay: 1 sec ) 
N0100 (Min Cut Length for DTHC ON : 80 units ) 
N0110 S900  (Global DTHC ON/OFF is ON ) 
N0120 M22 
N0130 S10 (Turn off DTHC at the beginning)
N0140 M22 
N0150 S3110 (Preset Volts set to 110 Volts)
N0160 M22 
N0170 S510 (DTHC Delay set to 1 Seconds)
N0180 M22 
N0190 M09 (Turn off extract fan)
N0200 M00 (Paused: Check the DTHC Settings - Hit RUN to continue)
N0210 G00 X204.724 Y307.639 Z20.000
N0220 M08 (Turn on extract fan)
N0230 M98 (HeightSense.tap)
N0240 G00 Z3.8000
N0250 M03
N0260 G01 Z1.500 F2300.0
N0270 S20 (DTHC is ON)
N0280 S10 (THC Off By Code Snippet) (On small shapes)
N0290 G01 X204.723 Y307.641 F2460.0
N0300 G02 X204.261 Y309.354 I15.094 J4.988
N0310 G01 X204.257 Y309.378
N0320 G02 X204.078 Y311.592 I14.287 J2.267
N0330 G03 X204.096 Y308.057 I4.701 J-1.744
N0340 G01 X204.114 Y307.997
N0350 X205.338 Y302.877
N0360 G02 X205.840 Y289.833 I-26.626 J-7.555
N0370 X200.693 Y285.586 I-4.696 J0.449
N0380 G01 X200.602 Y285.604
N0390 G02 X195.375 Y288.376 I4.345 J14.504
N0400 X192.598 Y290.839 I14.627 J19.287
N0410 G01 X190.575 Y292.753
N0420 G03 X186.094 Y296.980 I-112.149 J-114.400
N0430 G01 X185.413 Y297.608
N0440 X185.405 Y297.616
N0450 G03 X185.163 Y297.786 I-0.678 J-0.703
N0460 X184.696 Y297.509 I-0.017 J-0.504
N0470 G01 X184.785 Y297.454
N0480 X184.853 Y297.403
N0490 X187.671 Y294.865
N0500 X192.524 Y290.542
N0510 X192.536 Y290.531
N0520 G03 X198.940 Y286.004 I18.418 J19.261
N0530 G01 X198.972 Y285.986
N0540 G03 X206.140 Y288.527 I2.545 J4.201
N0550 G01 X206.147 Y288.545
N0560 G03 X206.976 Y292.967 I-10.471 J4.251
N0570 G01 Y292.990
N0580 X207.026 Y294.572
N0590 G03 X206.672 Y297.491 I-10.221 J0.241
N0600 G01 X206.665 Y297.518
N0610 X206.485 Y298.379
N0620 X206.482 Y298.396
N0630 X205.242 Y305.584
N0640 G03 X205.008 Y306.680 I-13.490 J-2.305
N0650 M10P1 (Torch Off By Code Snippet) (Before end)
N0660 X204.724 Y307.639 I-13.256 J-3.402
N0670 S20 (THC On By Code Snippet) (On small shapes)
N0680 M05
N0690 G00 Z20.000
N0700 M09 (Turn off extract fan)
N0710 M01 (Paused: Hit RUN to continue)
N0720 X0.000 Y0.000
N0730 S900 
N0740 M22 
N0750 S10 (DTHC is off)
N0760 M22 
N0770 M05 M30

Just for update, the issue is caused by having two S codes in sequence - the system cannot handle this an the codes are ignored.

The S codes need an M22 call between but the M22 is a delay macro and will cause a pause in motion.

I’m still fighting the issue - i need THC off but only in cut rules - you cannot use the Global DTHC on/off as well as THC on/off in a path rule :frowning:

Would a action point work on that area Dave?

I never had 11B, currently on 11M7?
Don’t know if that’s a good or bad think.
On small details I try and make put them on a layer I can control.

Not sure, i have never used them and will have to read up on it.

It might work though.

Yes thats what i did today, i normally use the auto external/internal feature but this time i created a duplicate tool with global THC off and used manual layer control - that all worked nicely, no torch-dives etc. just takes longer on the PC :slight_smile:

I don’t really want to change posts as i modified this one quite a lot :slight_smile:

If i can figure it out, it would better how i had it before but needs a big post mod - this is what happened before and fails…

N0240 G00 Z3.8000 
N0250 M03 
N0260 G01 Z1.500 F2300.0 
N0270 S20 (DTHC is ON) 
N0280 S10 (THC Off By Code Snippet) (On small shapes) 
N0290 G01 X204.723 Y307.641 F2460.0

This is whats wanted…

N0240 G00 Z3.8000 
N0260 G01 Z1.500 F2300.0 
N0270 S20 (DTHC is ON) 
N0275 M22
N0280 S10 (THC Off By Code Snippet) (On small shapes) 
N0250 M03 
N0290 G01 X204.723 Y307.641 F2460.0

Looks minor but needs the THC codes put before the M03 call so the M22 delay has no effect

Ah get away :smiley: never used them!
It’s a doddle, would be ideal for that job.

Hi sean,

I’ve just been messing with SC and i just cannot make sense of action points - you cant fit them on a lead-in so i put one just at the start of the path and told it THC off at start, length 50mm and THC on at end.

All i can see is that its added two more action points further along and in the code the actions are backwards! THC goes on at the start and off at the end.

Way more complex than it needs to be - i just need the THC off with my “Small shapes” path rule and back on at the end - this fails though as the global THC on clashes with the path rule and you cant have two S codes together, put an M22 delay in and it works but you delay the torch while its on and that burns the part.

In my mind the THC commands should ALL be BEFORE the torch fires - this would all then work.