Digital Art Zone

I have designed a small part to be CNC’ed. I have made dxf files of it, however the company that will do the CNC work cannot use Carrara’s dxf file because the content of the part (model) is trianguarized. How do I produce a model for CNC work with out the triangularization?

Designerbob - 16 January 2013 09:03 AM

I have designed a small part to be CNC’ed. I have made dxf files of it, however the company that will do the CNC work cannot use Carrara’s dxf file because the content of the part (model) is trianguarized. How do I produce a model for CNC work with out the triangularization?

Did you model it with quads or triangles? I know the vertex modeler in Carrara can do both, but if you model with quads and the exporter converts to triangles during the export, you may have to try exporting the model using a format that preserves the quads, and then using another program to convert to dxf. Maybe .obj would work?

Designerbob - 16 January 2013 09:03 AM

I have designed a small part to be CNC’ed. I have made dxf files of it, however the company that will do the CNC work cannot use Carrara’s dxf file because the content of the part (model) is trianguarized. How do I produce a model for CNC work with out the triangularization?

Ask the machinist of he can take Gcode Converter (G-Code).

There is a free converter here (DXF to G-Code).

http://www.dewittindustries.com/cgibin/metavector/

Try OBJ, and if that has trouble, then get MeshLab (free) to convert it to something they like. They might want STL or another format.
As for their comment about it being triangles, the only thing I can think is they were expecting a file with primitives and boolean solids operations, (sphere, cube, cylinder) instead of a mesh. DXF is totally capable of that, but Carrara is not. It doesn’t really use those internally, so it certainly can’t export to it. That would be a task for Autocad or Solidworks.

But there are tools to create a G-Code tool path from a mesh. MetaVector is one, (I hadn’t heard of- interesting) or try Skeinforge.
Skeinforge is open source, and originally for 3D printers, but also has a cutting mode for CNC tooling.

It looks to me (in a brief peek) that MetaVector is designed for 2D designs - it mentions several CNC type tools that are typically used only on flat stock. (sheets or plates) Skeinforge is designed for full 3D work. Not knowing anything about your task, I can’t say which is best for you.

One possibility is the company is only expecting 2D lines, instead of a 3D mesh. If their CNC tool is just a cutter then it won’t have much height control, and they may use it primarily for signs or sheet metal. But even in that case, if it reads G-Code it can be used with Skeinforge to do 3D. (Within it’s limited height.) But if it read HPGL or some proprietary language, then there’s not much it can do with height.

It is possible to machine from facetted (polygonal) files, but in general machinists prefer nurbs file format, which cannot be created with Carrara. Some example applications would be would be Rhino, SolidWorks, ProE. In addition to the native file format, nurbs based applications generally save to common nurbs based formats such as IGES (IGS), STEP (STP),  and SAT (ACIS).

There is a free nurbs modeler here:
http://sourceforge.net/apps/mediawiki/free-cad/index.php?title=Main_Page

A relatively inexpensive nurbs modeler is ViaCAD 2D/3D or ViaCAD Pro
http://www.punchcad.com/c-12-consumer-cad.aspx

Moi3d is also inexpensive, and uses the Rhino format:
http://moi3d.com/

DesignerBob,

Is your machinist doing a 2d or 3d model?
Alot depends on your machinists software, since it must be able to import & convert it to G-code, however,

In the 2d software I use,
For 2d these formats can be imported: dxf, dwg, eps, ai, pdf, pvc, v3d, v3m

In my dreams + $1,700….
For 3d Mesh files these formats can be imported: stl,3d dxf, obj, 3ds, vrml
Rhino, Solidworks, AutoCad, Silo, Moi…etc….

McGuiver - 16 January 2013 10:43 PM

DesignerBob,

Is your machinist doing a 2d or 3d model?

Good point.

For 2d CNC, a DXF file with arcs in the curved areas is the best format.

Carrara does not create 2d DXF files. Most CAD applications, such as the ones I mentioned, can create a 2d DXF file.