This one has me stumped. I’m trying to create a new part that measures approximately 4’ x 8’, with the large face featuring a stacked stone texture. Ideally, I’d be able to define the grout lines but the face needs to have a natural stone, 3D texture to it. This needs to go direct to tooling, so a STP file is required. Can’t be an STL mesh like you’d find in rendering or gaming worlds. I can render how it looks but that doesn’t help me get it across the finish line with an actual, CNC’d mold.
If you are prepared to accept an interpolated, smoothed out result, you could convert the mesh to nurbs However, quadremesh, subd and conversion to nurbs in Rhino will only allow you to work with roughly 100,000 triangles. For a 4 X 8 area that is low resolution. You might have to sub out the mesh to nurbs conversion to someone with DesignX that can convert a higher resolution mesh to nurbs. Mesh2Nurbs and Cyborg3D also have mesh to Nurbs conversion and they are a lot less $ than DesignX. Unfortunately I don’t know how the results compare to DesignX. You still will not get a surface with sharp features from DesignX, it is a limitation of interpolating the mesh to nurbs.
You best option is to find a way to machine it as a mesh for a result that is faithful to the detail in the mesh. You did not say what king of molding process you are using. There are CAM systems that can use meshes to cut steel, if that will be the mold material. However, finding a company that has the CAM software and CNC machine might be a problem as many toolmakers will not cut meshes because the toolpath cannot be optimized, resulting in slower machining and more wear and tear on the machine.
The signage industry uses CNC routers that cut lower density material like HDU so the issue that toolmakers have with cutting steel from a mesh is not present. Perhaps machining a substrate as a mesh in a lower density material, and then using a spray metal technique to produce the mold might be an option. Although the thickness of the metal coating might smooth out finer detail that you are trying to keep. Manufacture of Sprayed Metal Moulds | Metallisation
Brilliant! The level of knowledge on this site always delivers!
I just asked the mold-maker about software and was told they use WorkNC for tooling path programming.
This panel is rotomolded polyethylene, aluminum mold. Given the scale, it certainly doesn’t require the extreme precision of an injection-mold tool.
So it sounds like I need to find an appropriate STL mesh and then have it converted to NURBS using conversion software. Would I then need to figure out how to apply it to the stone faces in Rhino, then sending out as a STEP to tool-maker? I’m guessing that file would be absolutely gigantic. Or could I provide the NURBS file to the path programmer and simply indicate which of the flat surfaces need to have that NURBS surface applied?
This is crazy complicated but if I can get it figured out, would be HUGE. Right now, the only option I can see is making a physical stone wall and then a fiberglass splash off that. Then casting it and sending to a foundry.
I may have misunderstood where your texture is coming from. I was assuming you already had a mesh with the texture?
Since aluminum it less dense than steel, its possible your toolmaker can use an STL file, and maybe the toolpath optimization that would result from the CAM software creating its own mesh from the nurbs is not as critical. WorkNC will import meshes according to the import formats listed here Nexus Documentation Center If the toolmaker has told you they will absolutely not use a mesh, then you will have to convert your mesh to Nurbs.
CAM software has a limitation in the number of nurbs surfaces it can process. So you’ll have to check with you toolmaker to see what their limitation is. That could reduce the amount of detail you can preserve from the mesh.
Thanks again for all the excellent info! I looked at that Nexus document and it doesn’t list the ability to read STL for WorkNC. I’m sending some screenshots to the tool programmers to make sure they understand what I’m ideally wanting to do.
So assuming that it is actually possible to apply an STL (or converted NURBS) to flat, planer surfaces on my file, how would you suggest I acquire the STL scan of rock? Is there somewhere online that sells these files, perhaps for rendering and game-design artists?
I’m sorry, you are incorrect. Toolpath optimization requires that the CAM software to generate its own mesh from the Nurbs surface. Toolpath optimization is needed for smooth cutting in a dense material like steel to provide a better quality surface.
If an STL file is provided to a tool/machine shop, they have zero ability to control the “smoothness”, the number of facets. If they are given a nurbs surface, they can have their CAM software create the mesh to produce a smooth surface.
The CAM software I run has never hit a ceiling as far as size of STL file. I do a ton of artistic mold type work so the stuff needs to be smooth as a baby’s butt. I can produce that smooth surface directly from Rhino, I have no need to have a CAM program reinvent the wheel.
That is exactly the the point. If you want a smoother finish, you need a nurbs surface. If you are cutting a steel mold for injection molding, you want the result to be as smooth as possible.
