Export .stl file shows gaps in some faces

Hi. I’m fairly new to using Rhino. I’ve rendered a guitar neck, everything seemed to go smoothly, but when I export a .stl file, I see gaps and strange squares inside round extrusions. See screen caps. I’m trying to import this file into MeshCAM for CNC g-code programming.

Hi Kenneth - if those surfaces are not joined at the meshing stage, or if there is a naked edge there (ShowEdges command) then the mesh will not match up across the edges. Generally, if in doubt, use the Mesh command to generate a mesh, and hide the surfaces,and inspect the mesh, then troubleshoot from there. When it is closed and looks correct , export the mesh itself to stl.

For stl , the mesh settings should be from ‘detailed controls’ and set the ‘Maximum distance edge to surface’ at something around the slice thickness of the printer as a starting point.


Thank you for this. I’m very new to using Rhino, so some of what you’re saying is going way over my head. I’ve tied playing with the ShowEdges command, but I can’t make heads or tails out of it. I get the same results. Is there anyone out there that would be willing to open my file and fix it up?

Mojo Bass Neck.3dm (762.4 KB)

Hi Kenneth - select all the surfaces and Join before meshing or exporting. ShowEdges will still show you a few nakeds that need fixing but you’ll see most of what you were asking about gets soerted out. Takeaway: if there are naked (un-joined) edges, meshing will not match up acoss the gap as you saw. There are many things to do when edges cannot be joined for some reason, you’ll become familar with those. I’ll see if I can sort out the ones in your file.

For example -

I’d make sure to understand the concepts of tangency and curvature continuity (the level 2 material has some stuff about this) for the type of surfaces you are building here.

Mojo Bass Neck_Closed.3dm (491.6 KB)


Wow, thank you Pascal, looks much better now when I open the stl in MeshCam. I’m an Adobe graphics guys, and I’m very good at snapping things and lining things up in Illustrator, but for some reason, I’m having a hard time with it in Rhino. I’ll get there. Thank you again.

Hi Kenneth - AI curves are fine for print but generally do not work well ‘straight across’ for surfacing of any quality. Typically, curve continuity is marginal at best and that is one key thing that is helpful (good, controllable continuity) in surfacing. In short, check your AI curves with Rhino’s tools but even better is to draw your curves in Rhino.


Quick question Pascal. What CAM software would you recommend using with Rhino 3D renderings? I’m looking to cut my guitar parts on my CNC machine

Hi Kenneth - I am not the one to ask this - I have zero experience in this area, but in any case, I’d start a new topic with this question - there are plenty of users with experience who might not drill down into this topic.