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Author Topic: How to calculate the kerf width for plasma cutting?  (Read 18481 times)

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How to calculate the kerf width for plasma cutting?
« on: August 30, 2007, 04:07:59 AM »
As you know, when cutting with plasma, in proportion with the direction of cut, the kerf side changes. So, when cutting CW the kerf should be outside and when cutting CCW the kerf should be inside.
Now my question is:
Can mach3 calculate the kerf automatically by a given value in a DRO?
If no, can i use different tools from the "tool table" to do it? (how does this table work?)
Any ideas would be helpfull...

Offline Whacko

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Re: How to calculate the kerf width for plasma cutting?
« Reply #1 on: August 30, 2007, 01:15:46 PM »
The Gcode G40,G41,G42 are the Gcode commands for kerf on/off. Best you take care off it in your nesting software as there is no reverse run possible in G41,42 blocks. If you loose the cut, you cant go back to restart.

Whacko
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Re: How to calculate the kerf width for plasma cutting?
« Reply #2 on: August 31, 2007, 01:51:56 AM »
First of all thanks for replying.
OK, my nesting software gives G41 when CW and G42 when CCW and G40 at the end.
So, now, mach recognizes the kerf on/off and stop? And where can i set the kerf width?
Because (if i understand well) kerf is the gap that plasma leaves on material through cut.
So, if i have a rectangle shape of 100 x 100mm and the kerf width is 3mm, the path should be at 103 x 103mm,
and the final cutted rectagle will have the 100 x 100mm.
Can you help on this?

Offline Whacko

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Re: How to calculate the kerf width for plasma cutting?
« Reply #3 on: August 31, 2007, 05:27:15 AM »
Yes I can help you, I use MAch3 for plasma. The g41 and 42 is your tool offsets and can be set in the Mach3 environment. I use Cadlink's profile lab for nesting and post processing, but I take care of the kerf in the parts I generate in Turbocad. This is really because of the limitation to do reversing in Mach3. Mach3 will not allow you to run reverse if you lost the cut whilst in g41,42 blocks. This is essential with plasma cutting, as you might have to change consumables whilst in a cut. When you pause the motion you will overshoot the cut because of the slowdown parameter.

But if you want to use the g41,42 just set the kerf in the tool offset facility.

Whacko
Nothing's impossible
Re: How to calculate the kerf width for plasma cutting?
« Reply #4 on: August 31, 2007, 05:38:07 AM »
OK,
but where is that tool ofset facility?
I cant see it on the menus.

Offline Whacko

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Re: How to calculate the kerf width for plasma cutting?
« Reply #5 on: September 03, 2007, 03:31:19 PM »
Hey man, I forgot about this topic! Shees, I'm getting old. I believe the offsets are the G54 and onwards settings in the "Config" drop down menu under "fixtures".

Whacko
Nothing's impossible
Re: How to calculate the kerf width for plasma cutting?
« Reply #6 on: September 10, 2007, 01:48:56 AM »
Whacho, i tryied that (the g54) and seems that it follows again the original path.
Where can i find some information about all these g54-59???
I know nothing about them...
Ciao!

Offline Whacko

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Re: How to calculate the kerf width for plasma cutting?
« Reply #7 on: September 10, 2007, 05:16:49 PM »
No, the g54 is a tool select, with an offset parameter in the tables you save as I said earlier(the offsets are the G54 and onwards settings in the "Config" drop down menu under "fixtures). So you slect the tool at the start of your code, then you implement the g4X codes in the codefile as normal.

Whacko
« Last Edit: September 10, 2007, 05:18:49 PM by Whacko »
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Offline Whacko

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Re: How to calculate the kerf width for plasma cutting?
« Reply #8 on: September 10, 2007, 05:27:02 PM »
I put some visuals up, it should help.

Whacko
Nothing's impossible
Re: How to calculate the kerf width for plasma cutting?
« Reply #9 on: September 11, 2007, 07:09:24 AM »
Maybe i cannot understand exaclty what you say.
I put in the code before the G41 or G42, the G54 command:
.
.
.
G54
G41
.
.
.

I set at the fixtures (that very helpfully you uploaded) the kerf width that i want for axis X and Y.
Then i load the code.
The shape is a rectangular 200x200 mm.
So, i am expecting the cursor to go to 3mm around the shape (if the fixture is 3mm) which means 203x203mm.
Am i right?
Does it need anything else?
Because it does not work.