Problem with Preform

I’ve designed this flight of cast cement stairs and scaled it as needed in SketchUp 2017. It passes all the sold tests with Solid Inspector 3, export to OBJ and open in Preform. No errors generated anywhere.
As you can see by the first photo the bottom is hollow so to no over use material but also to orientate the stairs so the bottom is towards the build plate but has good drainage.
But, when imported into Preform, no errors generated, it shows a surface over both open areas and when supports are generated it puts them on these non-existant surfaces.

I don’t think you want any polys with more than 3 vertices. You need to “triangulate” the model.

I’ve had some trouble with printing Sketchup files but I’m not comfortable enough with the software to know whether this is a design or PreForm facing issue. I’ve had a fair bit of success using the STL exporter plugin for sketchup and then running the exported STL file through Microsoft’s STL Repair. Note, the repair tool will export a 3MF file which can be converted to STL using the 3D Builder tool in windows or Netfabb (which still has a non-licensed version). We haven’t made any modifications to how files are parsed by PreForm, but if this doesn’t seem to correct things for you, I’ll connect with our software and support teams to see if they can recommend a fix.


I’m getting this issue with a number of files sent over to PreForm. Also, I too have tried the STL export plugin in SK but when that file is opened in SK it has more holes than a piece of Swiss Cheese and is not usable. That too has happened on a number of files. Rather frustrating.

Are you noticing this issue in other software suites as well? Sketchfab uniquely seems to have some trouble with export to STL or OBJ file and I’ve not been able to export any files that natively print without requiring any sort of external repair process. You might analyze the models in Netfabb to see if that displays any errors.

There are not enough triangles on this model. Bump up your SplitEdgePrecision.

I went in and manually added quite a few lines to create triangles, it worked. I also added a bar across the base of the opening. Anyway, the file passed all tests and when exported to Preform there were no errors or false surfaces. So, I’ll give it a try today to see how it prints.
Thanks for that info, it helped very much.

Here’s a photo of the first printout of these stairs in HO Scale. They came out great.


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