Tuesday, October 13, 2009

 

Open-Source to the rescue!

To build anything in a RepRap, you need to have a 3-D design, save it as a STL or triangle mesh file, and load it into the RepRap host software (or skeinforge).

To create these designs, RepRappers use different programs - Either an adapted 3-d modelling programs, originally used for animation (like Blender and Art of Illusion), or freeware versions of CAD software (like CoCreate). These solutions work, and work well, but each program has seperate advantages. I've been looking out for a 'better fit' - a CAD-style program, that supports building meshes and solids.

Make magazine today furnished me with a link to FreeCAD.

It's pretty slick - either I'm quite lucky, or it works quite well. Within a few minutes I was able to load it up, get started, create a small cube model, export it to an STL file and import it successfully into the RepRap Host software (not always an easy thing!).

OK, lets give it a real test...

Let's load up some data from a complex file: a human head.
To really test it, I created a large sphere, stuck it on top, and did a 'union' (Join).
This is not nice: most complex geometries cause all sorts of bent and broken and backwards triangles. Lucky there is an analysis tool to point all this out:
From FreeCAD

Pressing some of the 'repair' buttons sorted all this out.
From FreeCAD

This exported easily to an STL file: and then loaded straight into the host software.

From FreeCAD


It started to slice and print to gcode : it got to 55 layers through before I got bored and turned it off.

FreeCAD is currently alpha software so far, but certainly one to watch!

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Comments:
I Played with it a bit, but couldn't figure out for the life of me how to move an object around with the mouse. Pointers?

Vik :v)
 
I'm not sure yet - so far, I clicked on the object at left menu, then 'data' on the tabs at the bottom, then ... on the position - brings up a translation and rotation dialog.

I might have to (gasp!) read the manual!
 
> I Played with it a bit, but
> couldn't figure out for the life
> of me how to move an object
> around with the mouse. Pointers?

Middle click with mouse, and move around;)

I have difficulties to install python-pivy on ubuntu jaunty. (dpeendency hell)
 
hmm, it looks like its panning.

Ok, I definietly need a tutorial. The program looks promising, but Im unable to figure out how to create a bit more complicated object.

So lets compile a tutorial about creating one of the darwin/mendel part!

Im definietly interested in it.
 
Ok, I cant really figure out how could I model simple things in freecad.
Here is how the program looks like:
http://khiraly.googlepages.com/freecad_mendel_frame.png

I would love to see a tutorial how to create a simple solid like this.

For 2D drawing, this tutorial looks promising:
http://sourceforge.net/apps/mediawiki/free-cad/index.php?title=Draft_tutorial

But, I cant find any tutorial about creating 3D CAD models, like our mendel parts.
 
It's most useful for creating stls from objects built in more sophisticated apps, STEP and IGES import work well, even quite large ones. Got filleting, but no choice of endcaps and no chamfer, and I've had some faces evaporate with more complex blends. Booleans work well. Object creation from parametric primitives provides for translation and transformation by cartesian absolutes only, no scale factoring, no angular vectors. Change the parameter in the data panel and objects update with edit|refresh. No spin/lathe, and extrude builds surface objects from closed figures, not solids, and filleting on extrudes sometimes doesn't recognise edges to do so. Good mesh creation from solids, good automatic mesh analysis/repair.
 
No trimming or priority snaps for drafting, and no hybrid polylines (curve/arc) either.
 
To move an object with the mouse: Double-click on it's name in the project tab of the combi view and a cage appears around it. The arrow parts of the cage move it around, the wires between the arrows rotate them. Visual control only, no correlation to data while its happening.
 
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