Converting .stl file to .stp (.step)
I have a perfect scan of an object - put into a .stl file.
I need to have a perfect .step file for CNC Machining/drilling. All manufacturers ask me for a .step file.
We had this .stl file converted into an .step file, but the results are terrible. With the convertion the drawing has been simplyfied to a few hunderds/thousands triangles. The surface is approximaly and not as accurate as the scan or the .stl file.
Is there way to keep the same quality (the surface of my .stl file consists of millions ultra small triangles) ?
Can anyone help me ?
Or does anyone knows CNC Manufacturers with machines that can use .stl withous convertion ?
2 Answers
This is the problem of dealing with a file with millions of elements, to convert this to a step file requires many calculations by your conversion program. Starting off with many elements the higher the resolution you require in the output step file can make for a very large file and take considerable time. To keep this output reasonable sized verses a reasonable resolution and a reasonable process time, will always be a compromise. Often it is better, if you can re-model the part with a solids based software, from scratch, you will be better off. Often with the re-model approach you will end up with a usable file quicker than the conversion of a scanned item. If you attempt to create a CNC program from the large scanned, millions of small triangle high resolution you will end up with a file the CNC machine will have difficulty keeping up with a cut path made up of a very large number of short segments, which is what you will get from a model with millions of small facets. CNC machines prefer working from well defined surfaces made up from curves straight lines and the like as these will always be defined by pretrcise r
"Perfect scan data" might be a bit of a stretch. It is a good, clean scan, but the attached image shows one example of the triangles forming a void/bridge between two of the "fingers". It's not a big problem, but its a data error.
I made a tutorial about converting STL meshes to NURBS models (like a Step file), it might have some content you'll find useful: Convert STL (or OBJ) Mesh to SOLIDWORKS Model (NURBS)
This model needs to be redrawn in a CAD program to get clean data for machining. I'll estimate it could take about 8-12 hours to create a CAD model.
If there are specific dimensions, or design considerations needed, those need to be discussed before a model is made.
A second screenshot shows the progression of scan data to a CAD model of one "finger" with a deviation analysis. The model is tricky to build, it's a big optical illusion of planar faces with perspective.
If this is a paying job, try posting details here too: https://grabcad.com/groups/jobs-and-career-opportunities
