Size changes when export from OnShape

settanan_plangsiri

Hello! I am very new to OnShape and 3D design/printing, so I truly apologize if this question might sounds stupid. 

Currently, I am facing an issue with exporting my design in the .STL file. So I created a design with around 600um height but when I exported it and open in Blender... the height of my design became 15-16cm instead. I had made sure that the dimension that I use is similar to when I click export (centimeters). 



I had also try sending my .STL file to one of the 3D printing services. The reply I got was that the size was not specify in the file which is very baffling to me.

Is there a way to make sure/verify that my design is the correct size as what I planned to print is quite size sensitive! (Or is there certain file that you might recommend that would contain the size of my design?)

Thank you so much!!

martin_kopplow

Usually, if the scale error factor is suspiciously close to 2,54 or 1/25,4 (as in this case) then the issue is with metric to inch conversion. Try adjusting the settings in both applications to be identical and watch out for an additional scaling factor setting, which might exist independently from the unit setting. Unfortunately, some applications seem to ignore units stored in the file: Some do not write them and others do not read them. Some applications just assume, the units in the imported file are always inches, no matter what is written into the file. In these cases, it is sometimes wise (though not necessarily right) to export in the unit the receiving app assumes.

martin_kopplow

Usually, if the scale error factor is suspiciously close to 2,54 or 1/25,4 (as in this case) then the issue is with metric to inch conversion. Try adjusting the settings in both applications to be identical and watch out for an additional scaling factor setting, which might exist independently from the unit setting. Unfortunately, some applications seem to ignore units stored in the file: Some do not write them and others do not read them. Some applications just assume, the units in the imported file are always inches, no matter what is written into the file. In these cases, it is sometimes wise (though not necessarily right) to export in the unit the receiving app assumes.

settanan_plangsiri

@martin_kopplow Thank you for the answer! 0.06cm*25.4 does seems to get me to the length assumed by the program! This means that when I saved my design on OnShape as an .STL file, the size of my project is also saved right? (I just have to make sure that I opened the file with cm as the scale from the start... is my understanding correct?) 

Thank you so much!!!

martin_kopplow

Let me tell you a little story about a former colleague of mine. He always had that scaling issue. Nobody else in the office had, but he did, and even though his projects generally went well, the shop got their drawings with reasonable dimensions, and we checked he had set the units to mm in the export dialog, his exported files were always scaled wrong. After a year or so, we collaborated on the same project for the very first time, all using the same CAD system. The designers involved would create a large number of parts and we had a draftslady whose job was to merge all the latest parts together and povide an up to date reference assembly at all times. Even the native parts he contributed were all too small by a factor of 1/25.4!

It turned out he had been working with global decimal inch settings all the time!

So, to answer your question: Yes, I think your understanding is right. One should stick to a unit once that has been decided upon. Most probably, the millimeter units are more widely used, as compared to centimeters, at least in my primary industry (automotive). With furniture, architecture or shipbuilding, that may be different, though.

BTW.: I received a 3D print part just a few minutes ago, and so I can tell, that STL export from Onshape is not generally off scale, as the part came in just right.