Accounting for CNC Laser/Plasma beam diamater when create DXF datafile 1

[vonsteimel]

Greetings,
I arrange quite a bit of subcontracting for simple laser/plasma cut parts. I usually send a drawing as well as a DXF "data file" of just the part geometry, which they use to input in to the CNC. However, all the DXF files I send are pulled straight out of the Formal Drawings and therefore are drawn exactly to size.

It appears that the Laser/Plasma beams ride along the center of the lines in the DXF which in turn offsets the feature equal to the radius of the beam. Generally speaking, how much should I offset my lines to ensure the feature is cut to the size we want.

Say I want a 0.250 hole cut... what should I draw the hole at in the DXF? I guess the answer begins with first asking; what is the approx. diameter of a laser beam and/or a plasma beam as used to cut 18Ga steel?
Thanks,

VS

 

[berkshire]

That should be done in the toolpath program for the cutting machine, and should not be your problem.
Just reject any parts that are not to the size of your drawing, the torch operator will quickly get the message.
If you accept his centerline cuts, he will just keep on doing it.
B.E.

 

[NickE]

Berkshire is completely right. The print is not the cut path, the print is what the actual part should be sized to after it's manufactured. It is the operator/path creators job to adjust the offset so that parts can be made that meet the print specifications.

There are plenty of reasons why this is the way it should be done.

1) You want to put the making of the part on the subcontractor, if your prints are correct and checked, who is checking the toolpath you are generating by offsetting your DXF file?

2) If you do not require that parts are made to print, how do you assure that you are not responsible for suppliers' bad parts? It's pretty easy for the supplier to blame your DXF file, not so easy to blame a checked print.

3) By allowing a vendor to not make to print, you are allowing a vendor to control your tolerance stackup, and all your dimensional requirements. If this continues with other vendors you will begin having parts from different vendors not fitting together.


just some of the reasons....


Nick