How i can do operations on Mesh file/STL file

How i can cover this patch on STL file/Mesh file ?

PLz give any suggestions

Attachments:

Green 2.stl, 1.6 MB

Replies to This Discussion

Permalink Reply by martyn hogg on November 15, 2015 at 5:50am

How do you want to patch it?

With a flat, planar patch or do you want to somehow continue the curvature of the mesh across the hole?

You could start by creating a curve to loft to give a cutting surface to trim the edges of the hole. You would then have naked mesh edges which you could then create a patch with.

Permalink Reply by Phanindra on November 15, 2015 at 8:17am

Thank you for reply, start with curves (maintain the proper curvature) to cover total hole and that patch should have some thickness....

Finally that patch should be separated from the base body (by Boolean operation)

Regards

phanindra

Permalink Reply by Nik Willmore on November 19, 2015 at 8:51pm

This is normally done in $8500 Geomagic Freeform (or $30K for Pro version that includes NURBS). This took only 15 minutes in the standard version, as a mesh output, using the brand new 2014 Defeature button within the Smooth Area command, so I merely duplicated the import of your STL as 3D pixel clay, manually selected the hole edge area with the haptic arm tool being trapped inside the body to make it easy, and then smoothed a bit the resulting automatic fill-in that Defeature provided, after Boolean subtracting away the original form from the patch:

To avoid huge meshes from the uniform Freeform clay 3D voxels, there is a Reduce For Export command that I used.

This likely 3D printed titanium part wouldn't just click in place like a jigsaw puzzle so that's an issue, due to all the small undercuts within the joining line.

How to do this in Grasshopper? Well.... Various hacks come to mind and I'll think about it over time, but I know of no ready made solution.

Permalink Reply by Nik Willmore on November 19, 2015 at 8:56pm

Patch STL attached, and rotated original STL:

Attachments:

PatchNik.stl, 4.9 MB
PatchNikB.stl, 4.9 MB

Permalink Reply by Phanindra on November 20, 2015 at 12:57am

Thanks N Willmore

Permalink Reply by Nik Willmore on November 21, 2015 at 10:42am

I thought curvature analysis might isolate the edges of the hole but it's not quite abrupt enough without random little areas also having high curvature, and only little parts of the edge itself are tagged, and I'm not sure yet what to do with the curvy vertices to bridge between them with a patch:

Attachments:

MeshCurvature_0.31TEMP.gh, 974 KB

Permalink Reply by Nik Willmore on November 21, 2015 at 6:21pm

I have also realized that even if you could get Grasshopper to bridge the hole, you would then very likely have the needed Boolean subtraction of a copy of the original mesh FAIL, since the surfaces of the original and patched meshes are coincident or nearly so, which destroys Booleans in Rhino.

Free Autodesk MeshMixer ( http://www.123dapp.com/meshmixer ) can also make a patch though, by selecting and deleting the edges of the hole then just using its Analysis automatic fixing feature to patch the two holes, the upper surface hole and the lower surface hole, by simply clicking on the spheres at the end of lines indicating each hole.

Then a Boolean difference does work, and unlike Rhino, instead of just failing, it leaves stray mesh faces here and there that can be deleted:

MeshMixer is a fun and rapidly improving program, worth learning the quirks of. There's no good update of the user manual though, but lots of YouTube videos and this course that is now on udemy:

https://www.kickstarter.com/projects/1727665673/3d-printing-toolkit...

Permalink Reply by Phanindra on November 22, 2015 at 5:17pm

Thank you Nik, I tried MeshMixer same problem i got, there are lot of errors

Permalink Reply by Nik Willmore on November 22, 2015 at 4:32am

The idea that you will automatically patch that hole via Grasshopper is utopian since it has two surfaces it needs to make, of a matching thickness apart. I thought of shrink wrapping with Kangaroo the whole form, but it wasn't working well, even if I saved the mesh from spreading out too much over the whole by adding a spring length restraint.

But! If you first manually isolate the edge of the hole by overlapping it with new geometry you create in order to define the overlap as a selection, or by drawing two loops on the surface, then you can simply split the mesh to isolate the hole edge from the body, and then just figure out how to cap the hole edge on both top and bottom sides, thus avoiding any failure-prone Boolean subtraction strategy. The perfect joint information is already there, being the original mesh along the hole edge.

Isolate and extract the edge manually, by modeling a surface or mesh surface through the form and splitting the form with it, then create a closed mesh solid from that ribbon-like loop of mesh surface.

Permalink Reply by Nik Willmore on November 22, 2015 at 5:53am

So far, yet another Rhino failing/bug ruins it. I drew a curve freeform on a mesh in Rhino, moved it a bit away from the surface and scaled it slightly bigger, and also created a copy below the hole and scaled it a bit smaller, then lofted between them to create a cutting surface:

However...Rhino now refuses to actually split (MeshSplit) the mesh with the damn surface, a common problem, since Rhino is a very poor mesh modeler. It lacks any tools to just select mesh faces with a brush that I could them copy to isolate them.

There is a MeshExtractFaces command but you can only use a marquee selection box so it's rather difficult. I tried to UnWeld the mesh with angle = 0 to then explode it into separate mesh triangles and then use brush select (SelBrush) for an easier selection process, but that fails to give a clean curve split that I very much want for the patching of the edge into a solid. Splitting the mesh at existing triangles is a drag, and will never give a smooth edge:

Autodesk MeshMixer however, is smarter, and has a selection brush and the ability to then smooth the selection independent of the mesh faces! This lets you use the Separate command in the Selection palette to indeed grab your edge nicely:

In other words, MeshMixer has re-meshed the boundary for you! So, now in just a few minutes, you have a new, much easier problem to solve, a perfectly fitting edge that you need to create surfaces for on top and bottom, to turn it into a solid.

It's a complicated surface, which you can create boundary curves from (DupBorder), but then a simple Patch command will need considerable tweaking or post-editing due to wild curvature artifacts of the surface, before you convert to a mesh and try to match up the edges for a join into a solid.

Now you could maybe shrink wrap it though (Kangaroo) and obtain a nice mesh solid. There are examples for that already on the forum.

Attachments: