[OpenSCAD] DXF for cut and engrave

Alex Gibson alex at alexgibson.net
Wed Oct 30 07:36:52 EDT 2019


I use a Piranha laser cutter with RDWorks v7 / Lightburn software.  This does have the ability to offset the cut line to take into account beam kerf.  For most 2D cutting operations this is plenty – and the adjustments it has for homing, intensity, speed etc are all you need in a 2D world.  These are both ‘standard’ laser driving software packages – it may be that more stripped down laser engravers don’t come with these features – but they are only trying to be 2D cut, or engraving a surface.

 

When making very high precision assemblies using jointed sheet plastic, I leave the laser kerf offsets turned off, and instead offset these in openscad.  A good way is to use Minkowski to ‘inflate’ the shape that will be the output DXF, by half the (measured) laser cut kerf.

 

It is not hard to turn OpenSCAD into a crude slicer – using a lot of “projection” cuts through your 3D model, separated in Z by your layer height. You then output a numbered series of DXFs and cut or scan them one by one, moving the laser bed up each time.  

Of course lasers are strictly 2.5D – depth from above - And I’ve found the limiting factor is that errors stack up as you go further down, as both beam intensity and the absorption of the material vary a lot, so each layer is engraved on a progressively less even surface height.  This might even out for larger items, as if a layer is engraved too low, the beam may be defocused and cut less deeply…

 

I think a scripted use of Openscad code can be used fairly effectively to make a slicer for 2.5d topography in the laser cutter, but your mileage may vary considerably as to the quality of result it will have… 

 

Far more often, I’ve used such scripts to make 3D models from stacks of laser cut 2D sheet material such as foam or card – like Autodesk’s old 123dmake.  At the very extreme of this, you could use a vinyl cutter similarly to the MCOR iris paper 3D printer.

 

Interested to see if others have additional tips or ideas for similar processes?

 

Cheers

 

Alex Gibson

 

admg consulting

 

edumaker limited

 

·         Project management

·         Operations & Process improvement 

·         3D Printing

 

From: Discuss [mailto:discuss-bounces at lists.openscad.org] On Behalf Of Rob Ward
Sent: 30 October 2019 11:07
To: OpenSCAD general discussion; A. Craig West; OpenSCAD List
Subject: Re: [OpenSCAD] DXF for cut and engrave

 

Surely if OpenSCAD could produce coloured and layered elevations, the "slicer" (or any number of variants) could do the rest?
Cheers, RobW

On 30 October 2019 8:14:49 pm AEDT, "A. Craig West" <acraigwest at gmail.com> wrote:

The  essential problem is that there is currently no work flow for laser cutters that allows you to use the output from openscad directly, essentially there is no slicer. In an ideal world, you would be able to use openscad to produce 3d shapes representing the material cut away by the laser, and the 'slicer' program would calculate the required beam paths and intensity levels, but as the that doesn't exist yet, it's not a very useful approach to take. For better or worse, laser cutter designs currently consist of 2d open or closed paths, generally with colour used as a hint for beam intensity. If openscad was able to produce output like this, it would be immensely useful to a LOT of people almost immediately.

It also seems like far less work to modify openscad to support output like this, than it would be to both create a slicer program for laser cutters AND change the work flow of all of the people using laser cutters

 

On Wed, 30 Oct 2019, 04:30 Troberg, <troberg.anders at gmail.com> wrote:

RevarBat wrote
> In the BOSL2 library, the `stroke()` module can let you draw lines of a
> given
> width along a 2D polyline path, with optional arrows and/or endcaps for
> either
> end. The code for it relies on a lot of other features of the BOSL2
> library, though
> so it'd be a bit of work to extract that module out.

The problem is that as soon as they have a width, the laser will cut twice.




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