Manufacturable Meshes??

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Permalink Reply by martyn hogg on July 10, 2017 at 4:40pm

It depends on what software you are using as CAM to program your CNC machine. Some CAM software can use a mesh file such as an STL and in fact some CAM software only use STL or OBJ mesh files for 3d surfacing. These are usually the cheaper CAM software packages.

If you are using something like Solidworks with a CAM plugin then importing an STL mesh can be problematic because you either get thousands of tiny mesh face surfaces or you only get a graphical representation of the mesh which are both pretty useless in solidworks.

I have cheap CAM software for my CNC router at home... its called CAMBAM. This works with dxf files for profiles, pockets, engraving and drilling and for 3d surfaces it uses STL files. This is fine for most of what I want to do but I'm not making injection mould tools on my router!

Bothe of those are meshes machined using CAMBAM.

One downside to using mesh files is that the CAM software can't be "feature smart". I.e. it can't (usually) detect pockets, holes etc in the mesh that Solidworks would see as features in the feature tree and be able to program discretely. A mesh is often just viewed as an entire surface to be machined all in one go.

There is a discussion on here that cropped up again recently about turning meshes into NURBS surfaces...

Auto NURBS surfacing of Meshes This might help get you geometry into Rhino that can be exported as a STEP or IGS file which in turn could be used by software for designing injection mould tools. i.e. analysing draft and finding split lines then creating tool cavities. The surface you show in your image would be very hard to analyse for draft and split lines for an injection mould part though!

Permalink Reply by Ronan on July 11, 2017 at 5:45am

Thanks for the replies guys.

Martyn - interesting to hear about CAMBAM & similar systems handling STLs, I wasn't aware of that. You've got some nice results there! 

I might be able to use that method for larger CNC projects.

As for injection molding, yeah I'm aware that the surface I linked before would not be the easiest to make! That's just the pic I was using as a reference for the type of pattern. A better example might be the Jawbone Prime bluetooth headset:

So if I wanted to create something like this green part (with the hard edges for split lines, and snap fits etc on the underside) I think it would really need to be NURBS, right? Either converted from a mesh or modelled in NURBS in the first place. 

I'll have a play around with the Auto NURBS Surfacing method you linked and see how the quality is and whether Solidworks will handle it.

Another example of the kind of effect I would like to be able to achieve is this Renault concept car I saw at a Ross Lovegrove exhibition. I know how to create this as a mesh, but do you think they would have achieved this with surfacing instead? Since its a concept car I imagine it's possible that this part was actually CNC'd.

Tom - I'm not sure what you mean when you say a mesh "uses color interpolation to mimic fluent transition".  Do you mean the way Rhino displays a mesh vs. its true geometry?

I can imagine that working with large, reflective surfaces in automotive design, surface quality is critical. I wonder whether at a smaller scale (eg. the bluetooth headset example) a converted mesh would be just as good?

It does seem to me that Grasshopper is more geared towards architecture than product design, however I wonder how architects use the meshes they generate in real buildings? (Presumably they do?) Is there a fundamental difference in how architecture projects are realised that makes it more feasible?

You also said to get a good result from Grasshopper I'll need more tools in addition - can you recommend any specifically?

Thanks!

Permalink Reply by Ronan on July 11, 2017 at 8:46am

Haha yeah the car was generally a bit garish for my taste! But I liked that little pattern detail on the bodywork.

I think I will try Nik's approach for Mesh-to-Nurbs and see how the result comes out on smaller geometry. At the very least, it might be useful for doing quick concept visualisations for clients, so long as I don't get carried away and show them something which I'm unable to recreate with proper surfaces later! 

The last company I was working at had quite a few projects where the final product was 3d printed, so I think some of the mesh tools in Grasshopper will still be useful for that kind of thing.

I haven't used Surface-To-Surface morph before either so I'll give that a go as well.

Thanks again!