Boolean Operation with a Mesh

[chaddcurtis]

I have a friend who I am trying to help out. He has a STL file that is a scan of an object. He has asked me to take this file and use it to create the negative of it, essentially a mold, that can be printed in an FDM machine that I have access to. The file is a mesh of course, so boolean operations are out in Rhino and most 3d software (as far as I know). I used a trial version of Mesh to Solid to convert it, but I am still having no luck. I an a novice to Rhino I am hoping knows of a solution.

If seeing the STL or 3DM file would be helpful to understand this, I am certainly willing to email it if you are willing to take a look.

Any help would be very much appreciated.

Chad

[chmillman]

In Rhino 4 you can boolean mesh objects with other mesh objects as well as with NURBS objects. The commands are MeshBooleanUnion, etc. They don't always work, the mesh intersector needs some work still.

Otherwise, you can split the meshes with lines or planes at the needed spots and build your mold box manually, and then join them all together. If you don't manage, I will be happy to look at your file. --ch

[pointcloud]

In Rhino 4 you can also change back and fourth from mesh to nerbs?

The .stl is a solidworks file that can be imported or opened with rhino. Although in some cases you loose information in the conversions....

As chmillman said I too would gladly help by looking....

[chmillman]

Originally Posted by pointcloud In Rhino 4 you can also change back and fourth from mesh to nerbs?

You can always go from NURBS --> Mesh... Mesh --> NURBS is a different thing, however. Difficult to do without manual work and/or a specific reverse engineering program or both.

What I meant was, that Rhino 4 has the capability of working with both types of objects in the same operation in a number of cases, such as being able to trim meshes with NURBS etc.

The .stl is a solidworks file that can be imported or opened with rhino. Although in some cases you loose information in the conversions....

.stl is a "Stereolithography" file (triangular polygon meshes), not a Solidworks file. Most 3D programs are capable of generating them nowadays, to a greater or lesser degree of quality. Not all are capable of importing them or working with meshes, however. --ch

[pointcloud]

You are right... I misread the command....

I am sure that the stl originated from solidworks, am I incorrect? As that is the way most solidworks users save there files, well the ones I have seen...


////chadcurtis\\\\\

On the scan from object do you have a .txt file? It would look like a pointcloud without xyz in the basic code? If so you can get it into rhino easily...

[chmillman]

I am sure that the stl originated from solidworks, am I incorrect?

I didn't see anything in the original message that indicated that.

As that is the way most solidworks users save there files, well the ones I have seen...

No, Solidworks files would be .sldprt (part) or .sldasm (assembly). For a Solidworks user, saving their files in the form of .stl would make them useless for anything but prototyping, as all construction info would be lost as well as the original surface structure of the file.

Normally you EXPORT an .stl from a program to transfer the data to another program that only deals with mesh data for RP or milling. .stl is a so-called "exchange" format for triangle meshes, as IGES is for surfaces and STEP is for surfaces/solids. --ch

[chaddcurtis]

Thanks for the responses. I am using Rhino 3.0 and I am downloading the evaluation of 4.0, as I type, to see if I can have any success with it. I opened the STL with a text editor, and it says the file was created with Geomagic Studio.

The scan is that of a ear canal for a bird- it is a scientist friend of mine. As such, the object is only about 1/2 inch long but has around 16,000 triangles. Also, I think one of the main problems I am having is that the mesh is similar to a cylinder but open on one end. Trying to cap the end so I can use the Boolean operators has been a problem.

I am happy to post the file but it is larger than the 500kb limit on the forum. As I said in the original post, I am a novice but I need to learn how to do this because he has seven more files that need the same processing.

Again, the help is much appreciated as I stumble my way through this.

[chmillman]

Geomagic Studio is a high end scan data and mesh processing software.

If the mesh is open and you need all of it, you're going to have to do one of several things. Most likely, you will need to build a box around it, somewhat bigger than the object. At that point, you can remove one of the sides (the same one that corresponds to the open side of the mesh. Then, you'll need to connect the two with a mesh. Probably with something like MeshPatch.

Otherwise, to print it with FDM, you might be able to "thicken" the mesh with OffsetMesh and a value of 1.5 to 2mm, then you will have a "skin" volume to print, and you can use this for your mold. Just in that case you will also need to build some external supports for the mold after.

If you need, send me the stl file (zipped!) to:

chmillman

at

gmail

dotcom

--ch

[chaddcurtis]

Thanks to all of you for responding. It looks like the evaluation version of 4.0 does everything I need it to do and is practically painless. Assuming the other files are provided with the same quality of mesh, I think I am good.

Time to upgrade...

[arturo1mar]

Hey guys, I saw this discussion board and I am having the same problem. I am a student in high school and I have a part in Solidworks (a helmet) it has some pretty advanced geometry so I can't do the mold in SolidWorks itself.

My professor told me to try importing the part to Rhinoceros make the mold and then back to Solidworks. Yet, in between the transfer I guess it loses some identities and it won't let me do it. Can any of you help?

Thanks for the help. Greatly appreciated

[Mike 1948]

Originally Posted by arturo1mar Hey guys, I saw this discussion board and I am having the same problem. I am a student in high school and I have a part in Solidworks (a helmet) it has some pretty advanced geometry so I can't do the mold in SolidWorks itself. My professor told me to try importing the part to Rhinoceros make the mold and then back to Solidworks. Yet, in between the transfer I guess it loses some identities and it won't let me do it. Can any of you help? Thanks for the help. Greatly appreciated

Post your problem in the Solidworks forum and you might find a way to get the mold done in Solidworks. I haven't seen a part yet that can't have the mold or cavity routine run on it in one form or another.

Mike