I have created a closed polysurface and mesh in this file.
sh-casting-for-stl-092408.3dm (7.5 MB)
The polysurface is on the right, and is intended as half of a pattern to make a cast iron element for a gate. I tried to do the best I could to get this shape with what I think are relatively good surfaces. The mesh on the left was created using the Mesh command. It is closed. But when I use the check mesh tool it says it is a bad mesh. Now some of the things it complains about might cause problems with rendering or boolean things. I am concerned about two points.
If I want to send out this mesh as an stl file for someone to create a pattern for casting using a CNC router, are the issues reported about the mesh likely to cause problems?
Secondly, I’d like to investigate the reported problems with this mesh, but I don’t know what tools to use to try to find multiple surfaces or intersecting surfaces. Maybe these are not a problem but I don’t know. I’m hoping someone with experience can point me in the right direction.
thanks,
Joe
Edited on 8/11/24 after playing with things a bit, I think I realize that some of the things it reports about the bad mesh are not caused by the closed polysurface. I cleaned up the polysurface in a couple of places and made sure it was closed and good. I remade the mesh and still got non-manifold edges even though there are none in the polysurface. I am guessing that I’ll have to send the stl file to the pattern maker and get feedback as to whether they have problems.
Instead of using the Mesh command you could use _ExtractRenderMesh. This will give you a valid mesh.
Not sure if it is good for CNC’ing, I have no experience with that at all. I’ll let the rest of the community who is knowledgable about this chip in on that.
Thanks. I wasn’t familiar with that command. I tried it but it didn’t do any better on this particular object than what I had before. I’m beginning to wonder about the check mesh tool.
Slicers and CNC are actually incredibly crude tools that are tolerant of all sorts of problems, don’t worry about the ‘bad’ mesh until/unless the shop comes back saying there is a problem. Also don’t send people STLs to mill, send STEP/IGES, all actually good CAM software does NOT like mesh data.
I joined your surfaces and used the mesh command with the slider all the way to the right and the resulting mesh does not have any non-manifold edges.
In theory, you could have 1/4 of the piece 3D printed in high res SLA and create a sand mold…
I’ll have to take a look at how to create Step/IGES files. Haven’t done that before.
Just export a polysurface as STEP… I think for most things you can forget about IGES.
It’s a simple export…
as others have said cnc likes step or iges
use stl for 3d printing.
check out these videos for mesh info- ( I threw in some shrinkwrap videos too, just cuz they rule)
I didn’t have much luck with shrinkwrap. BUT many thanks for recommending STEP/IGES. It’s very simple and the file sizes are smaller than stl files for the meshes.
The pattern maker had initially asked about STEP files so I guess that is the best to send. There are options for saving that I’m not sure of, but I’m not concerned with textures so I unchecked that one.
Thanks again. It has simplified things.
Stl is a terrible format. Ut is all triangles that are not connected to each other. So, on import all products need to guess how to join them back together. This can be difficult in certain cases if not impossible to get right.
Obj and DXF are better as they store join information in meshes.
Step is a NURBs format that stores join and solid information.
use the STEP option ap214 cc2 automotive design for cnc parts. That seems to be the best for sending to a cnc cutter.
Many thanks for that STEP option suggestion.
In a way, I’m fascinated that we seem to have come so far, and yet technology seems, I don’t know, kind of squishy. There are so many things that are not straightforward. I depend on the experience of myself and others rather than well defined specifications.
I’ve started a new build of a desktop computer. The instructions, if you can call them that, are horrible.
Sorry for the digression. The files have been sent to the pattern maker. Got my fingers crossed.