|FreeCAD STL to STEP solid of Thing 64549|
Following a comment posted in the STL to STEP blog entry. I decided to try FreeCAD 0.13. As my CAD program is over 10 years old, it's about time I moved to something a little more modern. The stumbling block has always been import / export capability. Ease of use and graphics capability were additional considerations, but time has leveled the playing field somewhat where graphic rendering is concerned. The ultimate platitude usability is still a worry, though most modern packages seem to exhibit wrinkles now rather than show stopping user interface 'faux pas'.
Packages such as Tinkercad, Creo and the like are frequently crippled quite severely. Usually so as not to detract from some other market segment product being purveyed. Typical limits include import / export format limitations and resolutions. Or limited numbers of features allowed in the part, limited assembly components or limited capabilities e.g Splines, Surfaces etc. Creo, demanding to see a license server on the internet every 3 days. Assumes I care to expose my CAD computer to the internet. Whilst I have no designs in the 'top secret' category. When out and about, the necessity of using public internet to refresh the license; potentially 'creating backdoor access holes' for third parties; is not something I wish to do where possible. At the other extreme, Tinkercad's birth has been somewhat ignominious.
I decided the acid test for any candidate CAD software, was the ability to take an STL file from Thingiverse and create a solid model ready for subsequent modification. At this stage only and import export functions are important; with a view to migrating over time to native modelling.
The crunch test seemed to be the Thing 64549 which crashed Instep V2.0. It has a lot of points associated with the spiral and cylinder features, around 63900 apparently. So this is the first model I decided to try out with FreeCAD.
FreeCAD handles STL files using a family of functions grouped under 'Mesh Design'. Interestingly FreeCAD also has some basic Mesh fix up functions. However for the test I decided to rely on files previously manipulated in NetFabb.
The two screens below show Thing 64549 imported as a Mesh, converted to a solid, exported as a STEP file and finally imported back into FreeCAD. I failed to get a valid file from Instep which was allowed to run overnight. FreeCAD took somewhat less time and managed to produce a usable file, though a little large at 160Mb.
|Import of Thing 64549 STL and conversion to solid|
Here is a quick summary of how the conversion process is performed in FreeCAD 0.13. The example shown is based on a Raspberry PI case modified previously.
|Initial FreeCAD screen with Mesh functions selected|
|Imported STL Mesh|
|Selecting the FreeCAD Mesh fix up tools|
|FreeCAD mesh fix up tools|
|FreeCAD conversion of mesh to solid in the Part functions|
|FreeCAD solid conversion tolerance parameter (left as standard)|
|Converted mesh now as solid (notice extra entry in the Tree View)|
|Exporting the Solid as a STEP file (Select FILE the EXPORT from the menu)|