FreeCAD -> Lasersaur (was Kerf compensation)

[Michael Ang]

I've been playing around with exporting from FreeCAD to LasaurApp.

So far the best is to select the geometries and do File->Export->Flattened SVG.  I don't think it would be too hard to write a custom exporter that's tuned for the Lasersaur.

For example someone wrote an exporter for 3D printing that uses the Cura engine for slicing and presents a custom UI to control the parameters: http://forum.freecadweb.org/viewtopic.php?f=22&t=5466

Unfortunately I don't have access to a Lasersaur, but my plan right now is to generate SVGs to cut on an Epilog, so that's a pretty similar workflow.

  - mang

On Tue, Apr 22, 2014 at 12:41 PM, Michael Ang <mangt...@gmail.com> wrote:

Hey cool my German lesson for the day :)

For English speakers curious about FreeCAD, this is a good set of tutorials: https://www.youtube.com/playlist?list=PLu4XhOBNpasTKwjERkOoProJv9gFmdfLN

The Sketcher/constraints starts in episode 3.  I agree the Sketcher is very nice.  I've played with parametric models in SolidWorks back in the day, but usually ended up getting my model to the point the parameters would no longer propagate through the model (e.g. after some complex fillets).

I'm interested in "unwrapping" a 3D polygon model so that I can cut the faces on a laser cutter (with numbering and some munging for physical construction), if anyone has any pointers :)

  - mang

On Mon, Apr 21, 2014 at 12:59 PM, Stefan Hechenberger <ste...@nortd.com> wrote:

Hi Mang what's up,

Creating 2D geometry works well. There are two workbenches for this: Draft and Sketcher. Sketcher is totally ingenious. It allows you to draw geometries based on constraints. For certain problems it's one of the best tools I've used. Draft is more for freestyle drawing with nice snapping support.

Exporting 2D to svg or dxf is not so smooth. Most of the time something screws up. I haven't found a solid way of doing this. Although I think it would be fairly trivial to write a custom exporter for sketch/draft -> lasersaur in python.

Check out this Sketcher tutorial:

https://www.youtube.com/watch?v=FWKxsD45svw

On Mon, Apr 21, 2014 at 6:03 PM, Steve Baker <st...@sjbaker.org> wrote:

In Inkscape, it seems fairly easy. 1) Draw the 'ideal' shape you want. 2) Set the line width equal to the expected width of the kerf. 3) Select the shape. 4) Click on "Path/Outset" in the menu to offset the path by half the line width. ...done! But I agree with Stefan...it doesn't seem like a good thing to put this into Lasersaur's own software when it's so easy to handle it in external tools. Mostly, I think (as I said before) that the kerf is small compared to the positional error of the lasersaur - so if you need such extreme precision, you probably need a better tool. Lasersaur has belts that are over 8 feet long...the amount of hysteresis-causing stretch in them is far more than 0.14mm - so compensating for kerf when the positioning accuracy isn't going to respond to that seems kinda silly. -- Steve Stefan Hechenberger wrote:

Kerf-compensation is doable but not super easy. For most jobs compensating for 0.14mm is overkill and therefore not a priority for LasaurApp. It comes down to the geometric problem of polygon offsetting. I found a couple of open source implementations ... if anybody wants to take a stab at it let me know. In general I am inclined to keep LasaurApp simple/beautiful and make it rock-solid first. For power users and advanced features I am thinking of getting Rhino and FreeCAD integration going. It would be very nice to cut directly from these CAD packages. As a first step we would finalize a network API that allows any alternative software to talk directly to the lasersaur. Rhino and FreeCAD can then easily talk to the Lasersaur because they can reuse any python code that is already in LasaurApp. In these CAD apps calculating an offset is as simple as calling a function. Also FreeCAD has a super interesting feature called Parametric Objects. See the following for details: http://www.freecadweb.org/wiki/index.php?title=Scripted_objects http://www.thingiverse.com/search?q=freecad+parametric&sa= Thinking out loud ... -stefan On Mon, Apr 21, 2014 at 11:50 AM, Andy Dingley <din...@codesmiths.com> wrote:

On Monday, 21 April 2014 05:52:26 UTC+1, Tim Courtland wrote:

Plus you will always have that cut angle on thicker materials, canâ EURO (tm)t do anything about that unless you do multiple passes.

I don't find cut angle a problem. I was cutting 9mm MDF yesterday (I hate 9mm) and didn't have any discernible angling except for the screw holes, which came out slightly oval on the back side. -- You received this message because you are subscribed to the Google Groups "lasersaur" group. To unsubscribe from this group and stop receiving emails from it, send an email to lasersaur+...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.

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-- Steve

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[Steve Baker]

Flattening 3D geometry to something I could print out on paper and cut out
with scissors is something I did a few years ago - it's definitely
possible - and you could certainly use the laser cutter to do the cutting
and thereby skip the printing stage.

But doing that with thicker materials is incredibly hard! For one thing,
because the laser cutter can only cut through the wood at 90 degrees to
the surface, you can't make parts that fit perfectly together unless they
happen to meet at right angles. You can make tabs and slots that
interlock nicely at 90 degrees - but if you need other angles, then the
resulting object is never going to look particularly good.

What I have seen is people slicing a model (as if you were going to 3D
print it) and laser cutting the slices...but then there is no "unfolding"
involved.

-- Steve

>>> Plus you will always have that cut angle on thicker materials, canâ