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Overburn and how to turn DTHC off

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BensPlasmaAu
Posts: 195
Joined: Mon Jan 13, 2014 10:37 am
Location: Boronia, Melbourne, Australia

Overburn and how to turn DTHC off

Postby BensPlasmaAu » Thu Feb 22, 2018 3:36 pm

After writing this post, perhaps it needs to go into The SheetCam sub folder. But I thought with a few posts on hole quality etc that this might be relevant here as well. Admins, feel free to move it if required.

I have done a search already and know roughly what overburn does and how it will help my cuts, especially on holes.

So for the uneducated (me) how does one input a rule to do the over burn on holes. I have looked in SheetCam to add a new rule, but I can’t seem to work out the combination. Maybe it’s not even in this screen or set of options. Can somebody please step me through the process of adding a rule for overburn? SheetCam, windows xp system older parallel port Bladerunner DTHC IV.

Second part, I just read from tcaudle that I need to make sure DTHC is turned off, and not via a rule in SheetCam. Do I need to have a new tool in the library to make sure it is off completely? In the tool setup options there is the bottom field for DTHC. From memory 0 is off and 1 is on from my memory. Can someone step me through this as well?
Home built 3400 x 1400mm (11 and a bit X a bit over 4.5 feet)
Hypertherm Powermax 45
CandCNC Bladerunner IV
Some air dryer off the internet
Another water seperator I found unused on a shelf
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tcaudle
Posts: 973
Joined: Tue Feb 28, 2012 6:47 pm

Re: Overburn and how to turn DTHC off

Postby tcaudle » Thu Feb 22, 2018 8:07 pm

The easiest way to turn off the DTHC on holes or small objects is to simply use the "Min Cut fo DTHC" in the Operations in SHeetCAM. That never turns it on rather than trying to turn it off with a cut rule. You can make a new tool that keeps the DTHC off as long as you use that tool. It uses a Global DTHC on.off S code (900 and 990) rather than the S10 and S20. I am not a big fan of overburn. The problem is usually that the torch stays on AFTER the end of the cut and blows a divot. Thar is cured by turning the torch off BEFORE the end (which has to be done with a Macro and the normal M code cause a motion delay . You have to use M10 and M11 (both) ot make it happen without a motion delay. SOme of the later POSTS have the option to use M10 and M11.

It is advantageous to turn the DTHC off before the end using the "before End" cut rule. Stops any diving when you either cross over the start line or when the piece falls out.

djreiswig
Posts: 270
Joined: Thu Nov 19, 2015 10:02 pm

Re: Overburn and how to turn DTHC off

Postby djreiswig » Fri Feb 23, 2018 9:51 pm

I've tried to research how to use the M10/M11 codes without much success. Is it as simple as replacing the M03/M05 with M10Px/M11Px? How do you get sheetcam to insert the M11 code in the correct place before the end of the cut to turn the torch off before the motion stops?

2014 Bladerunner Ethercut Mach3 SheetCam
2014 Bulltear (StarLab) 4x8
C&CNC EtherCut
Mach3, SheetCam, Draftsight
Hypertherm PM65
Oxy/Acetylene Flame Torch
Pneumatic Plate Marker, Ohmic, 10 inch Rotary Chuck (in progress)

FazQuaz
Posts: 11
Joined: Tue Apr 18, 2017 11:14 am

Re: Overburn and how to turn DTHC off

Postby FazQuaz » Fri Feb 23, 2018 9:59 pm

I also wonder how you do this? Also, how far from the end of the cut do you turn the torch off to eliminate any divot.
Star Lab NGEN 4x8
PowerMax 85
Linux/Command CNC

tcaudle
Posts: 973
Joined: Tue Feb 28, 2012 6:47 pm

Re: Overburn and how to turn DTHC off

Postby tcaudle » Sat Feb 24, 2018 12:47 pm

There in lies the challenge. It varies with speed. In most case about .2 before thend works. Its time versus distance. The turn off time is fairly constant for given material, then it becomes a function of how far that is when moving at the cut speed.

You should keep the M03 and M05 in the code too because som eother things trigger of those commands. There are later POSTS (the "11 series , 11M or 11J) have an option in the OPTIONS at the top to use the M10 and M11. It not hard You simple add that into the functions that already use the M03 and the M05. One is in "onPenDown"" Yu simpley have to do a FInd and searech the POST code for the m03"

Thr M10/M11 has a P parameter that defines which output you are calling. In the Ethercut model with the ESS the ESS has to catch the M10/M11 code and send it to the correct output. It sll done in the ESS beacuse there is a delay between where MACH is and where the actual machine is. There can be up to 1 second of delay between when MACH reads the code and it actually gets executed.


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