csg2stp

convert openscad design to step brep

Why

The mesh output from OpenSCAD is not suitable for CNC (the actual shapes are not preserved to compile sane G-CODE). There's no way to add these information after the object is "rendered" to mesh, these information are lost forever. The arcs are turned to polygons, the surfaces are also turned to a mesh, etc. Because of this the only way to build a usable STEP file is to go back to the CSG output of OpenSCAD and rebuild the object using OPENCASCADE which is the only open source BREP library I know.

Requirements

Use my fork of OCC-CSG: https://github.com/gega/OCC-CSG.git branch: sweep

This fork has the necessary changes to support the complex conversions:

• sweep command for rotate_extrude
• random rotation for rotationally symmetric primitives
• brep analysis for csg operation to prevent crashes

Compile and install this tool with the extended features.

You also need to have OpenSCAD installed and available in your path.

Usage

csg2stp.sh part.scad [loops] [args]

• part.scad: the OpenSCAD file to be converted

• loops: number of STEP parts generated

  for complex objects multiple rounds needed to convert successfully

  [default: 1]

• args: additional OpenSCAD parameters

  [default: none]

Manual Operation

1. compile and install OCC-CSG (use my fork and the sweep branch)

   git clone https://github.com/gega/OCC-CSG.git ; cd OCC-CSG ; git checkout sweep ; mkdir build ; cd build ; cmake .. ; make ; sudo make install

2. build these utilities with cloning this repo and make

   git clone [email protected]:gega/csg2stp.git ; cd csg2stp ; make

3. open your design in OpenSCAD, render and export as CSG

   openscad -o model.csg model.scad

4. feed the csg to csg2xml and redirect the stdout to an xml file

   ./csg2xml <model.csg >model.xml

5. use xml2mak to generate a makefile

   ./xml2mak model.xml model.stp >model.mak

6. use make -f with the generated makefile

   make -f model.mak

7. model.stp is generated, check if valid and complete, if not, go to step 6 and try again

Fine Print

NOTE: The following OpenSCAD commands are not supported because OPENCASCADE doesn't implement them:

• hull
• import
• projection
• minkowski

WARNING: The process is not deterministic, for some models it needs to be converted several times in order to get the proper results!