Rhino 3D Import DXF, smooth edges become angular

Hello everybody,

First I would like to introduce myself. I am a 23 year old building engineer from the Netherlands. At this moment I am working on a DIY camp trailer.

I have designed this with my own building CAD-software and created a DXF file from it. For the CNC milling I have to create a .STP file and I am trying to do this with Rhino 3D .

The shape has to be extruded to 15mm, because the base will be made from 15mm plywood. At first I imported the DXF file in Rhino and then I used the tool ‘extrude’. This is the moment when it fails, because the smooth edges turn into angular sides and I have no idea how this could happen. The same thing happened when a friend of mine imported it in SolidWorks. Does anybody know how this could happen? And maybe someone is willing to fix this for me? I have attached the two regarding files.

Thanks in advance,


I need the model in .STP or IGES format.

20151103 Multiplex overig.dxf (180.7 KB)
20151103 Multiplex watervast.dxf (174.5 KB)

They seem to be OK to me - below are the two files in Rhino .3dm format, I exploded the block instances and extruded the curves solid 1.5 cm.

Just to note, most likely the CNC guy will want the parts in mm units, not cm, so you might need to change the file units before exporting as STEP.

20151103 Multiplex overig.3dm (305.6 KB)
20151103 Multiplex watervast.3dm (423.1 KB)


Ah Thanks for your quick answer! Unfortunately I am not able to open this files, maybe because i am using Rhino 4?

Maybe an impertinent question, but could you change the files to millimeters, and export to .STP? :grimacing:
Thanks a lot already.


Here are the files in both RH4 and STEP formats. Units were changed to mm and the geometry NOT scaled. The height of the camper is now about 1.5 meters whereas it was 15 meters.

20151103 Multiplex overig-RH4.3dm (723.7 KB)
20151103 Multiplex overig.stp (492.9 KB)
20151103 Multiplex watervast-RH4.3dm (527.2 KB)
20151103 Multiplex watervast.stp (541.4 KB)

Hi Wim, thanks a lot for your cooperation. Since I have a lot of error messages, could you please do one last thing for me?
Change the extrusion from 1.5mm to 15mm? And then export as a STP file. I would be a very lucky man with that! hehe

Thanks in advance,


20151103 Multiplex overig.stp (396.6 KB)
20151103 Multiplex watervast.stp (450.6 KB)
20151103 Multiplex watervast-RH4.3dm (471.8 KB)
20151103 Multiplex overig-RH4.3dm (583.0 KB)
What kind of error messages were you getting?

Thanks a lot!! :smile:

Opening, extruding and exporting the file was no problem, but I was not able to open it in a STP viewer, it said there was a problem that could not be fixed. I probably do not have enough knowledge of this software, because I am used to building CAD software.

Thanks again for your help.