SKP to IGES or STEP (for metal fabrication)

export
iges
step
stp

#1

I have seen the two other posts on this topic, yet the posts did not seem to provide a clean answer. Is there a newer answer to converting from skp to one of these other formats (requested by the sheet metal fabricator)? Thanks for any suggestions.

Jerry


Export for injection molding
#2

You might take a look at FreeCAD. It will accept a variety of formats for both import and export. For example, this sample part:

I exported it as a DAE (Collada) file and imported it into FreeCAD:

You will need to use the Part workbench to convert the faces into a shape, but once that’s done, Select All and export in whatever format your vendor requires.

The following export formats are supported:


#3

After playing around with FreeCAD a bit, you should probably export the SKP model as an STL file and not a DAE file. The results seem to be much happier all around.


#4

Hi Jim,

Actually I had tried this approach and exported both a step and an iges file. They were both created but very small and when I tried to open them in freecad there was nothing there?

Jerry


#5

Jim,

My mistake. When I tried to open them in xometry for a quote, the site said they failed to load (error).

Jerry


#6

This may sound like heresy, but try exporting the STL file in millimeters (it doesn’t matter what units you are actually using in your model). Then import it into FreeCAD and export it as an IGES or STP file.


#7

I’ve never heard of Xometry, but I may be giving them a try in the near future. My two sample files were created as (s) a 10"x8"x0.1" model and exported as an STL file using “Inches” and (s2) a 5"x7"x0.1" model and exported as an STL file using “Millimeters”. Both were imported into FreeCAD (which, I believe, assumes STL files are in millimeters) and then exported as an STL file and a STEP file. Here’s the results after uploading the step files to Xometry:

Uploading the second STL file to Shapeways (selecting “millimeters”) gives this:


#8

Since you mentioned Xometry - they accept .stl files directly so maybe you don’t need the intermediate conversion?


#9

@jim_foltz, they have this note about metal fabrication:

Note: .stl files cannot be used to fabricate CNC, Lathe, or Sheet Metal components. Please use another file such as a SLDPRT or STP.


#10

Hi Jim,

I tried exporting as stl file in mm and then imported into freecad. Then exported step file and xometry still would not take the step file?

I have run the stl file thru meshlab and netfabbc and no errors.

Jerry


#11

Jim,

It looks like you loaded the stl file into shapeways . The stl file has always worked and shapeways will not take step files?

Jerry


#12

@glb - I’m not sure what the problem might be. You might try a simple part (like a small brick) to test the process of exporting from SketchUp, converting with FreeCAD, and uploading to Xometry. This would indicate whether or not the problem is with the conversion or perhaps your model itself.

Shapeways only accepts files in the following formats: DAE, OBJ, STL, X3D, X3DB, X3DV, and WRL. For color prints they only accept files in DAE, WRL, X3D, X3DB, and X3DV.


#13

Hi Jim,

Same problem with small brick. It apperas to me that FreeCad cannot convert stl file to step file.
I recall reading somewhere that a spline type rep and a polygonal rep are very different and additional steps might be necessary to switch between formats. Have you tried a small brick
with your technique (can view step fie in a step file viewer) ?

Jerry


#14

The screenshots I posted a few entries back show the “S” step file I uploaded to Xometry.

Just now, I created a brick in SketchUp:

Exported it as a “millimeter” STL file and imported it into FreeCAD:

Converted the mesh to a shape, exported it as a STEP file, and uploaded it to Xometry:

Here’s their 3D view:

Still not sure what you might be doing wrong …

[added]

BTW, here’s the brick.step using Autodesk’s A360 viewer:


#15

I think you’re missing the steps to convert the imported STL mesh to a FreeCAD shape. Only shapes can be exported. You need to open the Part view first:

Then click on the filename in the left panel to select it (or use Control-A to Select All). Then click on Create shape from mesh…:

Then select the shape in the left panel (or use Control-A) and use the File >> Export option:


#16

in general, doing a file format conversion does not change the file content of course, i.e. facetted meshes won’t convert to NURBS surfaces typically used with 3D CAD exchange formats as STEP, Acis SAT or IGES.


#17

I’m not sure about the STEP file format, but the IGES format exported by FreeCAD outputs planes (144 - Trimmed Parametric Surface) bounded by (142 - Curve on a Parametric Surface) lines (110 - Line) for the case of the brick. There are twelve of these sequences … one for each triangle in the model. I suspect that any SketchUp STL export of lines and faces will translate into the same IGES entity types with no problems. I’m not familiar with STEP files, but I’ll look into its format when I get a chance.

Side note: From about 1982-1990 I wrote a number of IGES importers in FORTRAN for GE Calma systems. Most of the issues revolved around inconsistencies between various exporters, notably defining the normal vector to an arc … most exporters used the right-hand rule and some, for whatever reason, used the left-hand rule. When I’d see a radiused part that looked like this:

I had to reverse the sense of the vectors during the import. It’s somewhat depressing to see that folks are still using Hollerith ASCII format ;(


#18

sure, if the used application is doing an appropriate conversion but still representing a curved surface made of lots of facettes even if using curves as boundaries and not as one surface regularly expected by users of NURBS modelers importing STEP/SAT/IGES data.

The old IGES format should be avoided anyhow because of the flavours concering trimmed NURBS surfaces or support of the manifold solid b-rep object entity (#186) may lead to problems in the destination application.


#19

Jim,

I don’t know what I did wrong with my brick, but will give it another try now that you have shown me your success.Many thanks for your sticking with me!!!

Jerry


#20

BTW, the “curves” I see in the IGES file for the brick are composed of three straight lines. There are no surfaces other than planes with three lines for the boundary. In other words, the edges and faces appear unaltered. The downside, of course is that a nice-looking dome in SketchUp will end up being a bunch of facets (just like the STL file). At least within the FreeCAD software, no attempt is made to generate NURBS or other surface types beyond a flat plane in the IGES format.

There is one other entity, the 402 (Form 1) which says that my brick is made of 12 entities, with pointers to each of the straight-line bounded planes. Dissecting the IGES file related to a 24-segmented dome (created using Follow Me), shows 286 line-bounded planes (most of which have three edges, but some have four).

I’m not sure how one would create and export anything like that from SketchUp in the first place … but I agree with dumping the antiquated IGES format. The info I came up with (above) is based on the proposed 6.0 version, circa 2001. I only looked into the IGES file in detail since I’m already familiar with the format.