I`ve designed that mold (for plastic injection). I would like to mill it in epoxy block (42cm x 13cm x 19cm).

This is in polygons because part was designed firstly for 3d printing. I have more of it but I don`t have enough time to rebuild it from scratch in pure NURBS and I can`t find milling service from polygons.

1) Do you know some online milling service which can produce it from STL file (instead of IGES)?
2) Do you think is it possible to mill such a thing from polygonal mesh?
3) Do you know any converter to take that parte ready to mill?
4) Is it possible to import that mesh to MoI and convert it to NURBS without converting it to SUBD?




I would be grateful for any help.

Hello,

I have software that should be able to RE the part quickly and accurately. It may be useful to get a second opinion on the mold design unless you are confident that it's optimal.

Could you tell me more about it?

Hello M,
Programs can read in the stl no problem.

But the "mesh" data will lose accuracy for something like a mold.

So your model appears to have locating pins!

The difference in cnc with mesh or NURBS data, is the mesh data will have to be cut with a 3d toolpath. Something that just rasters over the outer surface in some way. It wont know there is a perfect arc, located at a perfect coordinate.

Also, parts like the inner edges of the mold cavities will be affected.

A way this would be dealt with is to "defeature" the parts that need mold precision. This is more specialized software, like spaceclaim or others.

Maybe better to use the mesh as a ref and just remodel the part in moi!!!!

2 cents

Thanks, super precision is not so important. I need only about 0.5mm on 30cm part. It should be enough. Both parts of mold are made with booleans so they have same geometry with small offset. This is for low pressure injection so it won`t be NASA tech ;)
I would like to try without rebuilding. If quality will be very bad then I will rebuild whole model in CAD but I design those things very fast in polygons and I feel that rebuild that thing in cad will be time consuming process (especially for me - I`m much better polygonal designer that CAD one). Thanks for that Spaceclaim. I`ve asked them about price.

Please tell me:
Is it possible to import OBJ to Moi without changing it to Subd? I can`t find script for this.

What soft would be fastest to rebuild that thing for CAD. Will Rhino 7 would be better for that? I`m MoI user and I love it but I`m not sure is it right tool for that kind of job.

I have all parts in Subd but after importing parts to build that piece I have to dealt with many errors in MoI after booleans operations.

Is there any affordable app which will convert Subd to NURBs and do some booleans on it without generating errors (on fly)?

I know it`s fault of creases in Subd. I have a lot of them to have quite sharp corners.

Thanks for you help.

Cheers!!!

Hello,

Ideally RE the design in NURBS then have it reviewed by an individual experienced in mold design. The RE software I use alone costs $$$$. It's possible that you may have an optimized mold design that can be effectively machined. Start right, end right, more often than not saving you time and money.

Thanks for all tips.

One more thing to note ... do NOT convert the triangles/facets to individual nurbs surfaces. This is not the same as reverse engineering.
It will still be a problem for the CAM software due to the number of surfaces and breaks in tangency between each triangle/facet.

Hi mdesign,

re:
> Please tell me:
> Is it possible to import OBJ to Moi without changing it to Subd? I can`t find script for this.

There is a converter script on Max Smirnov's file archive (go to http://moi3d.com and then the Resources page and then find the link to Max's file archive), but it will convert each polygon into an individual flat trimmed plane and that is not how NURBS models are expected to be configured.

There is also an OBJ to 3DM wireframe converter on the Resources page as well, that will convert an OBJ file into a .3DM file with a line segment made for each polygon edge.

Neither of those will convert your polygon model into a normal NURBS structure, at best you would use it as a visual guide while you reconstruct the model.



> I have all parts in Subd but after importing parts to build that piece I have
> to dealt with many errors in MoI after booleans operations.

Can you please post the model files of a small area that has these problems before you do the booleans?


> Is there any affordable app which will convert Subd to NURBs and do some booleans on it
> without generating errors (on fly)?

Yes, MoI can do this but your sub-d meshes will need to be well formed, no things like degenerate or self intersecting polygons.

- Michael

Hi M,
""""""""""super precision is not so important""""""""""""""

The "precision" isn't nessasarily speaking to cutting things at .0001 tolerances.

It is more relating to things like the "Locating pins" you have there. Drilling a hole and sticking a pin in it, is not so easy, when you add "6 pins"

Your mold wont just "slip together". unless you cut slop. Then your mold is sloppy.

To reverse engineer that in CAD, I would just design that block with it's angles, and add the pins. (Leaving the cavity core part as just planes that go across) Pretty simple in MoI.

Then, you can cleanup your poly model by just deleting all the faces that aren't part of your cavity.

You can then import the 2 parts (STL Cavity and NURBS Mold.

Cut the NURBS parts. Then mill the cavity into the surface of that.

So, you would end up with this as a parted mold:



The parting line and Pins are good matches and will cut properly

Then all you need is the STL "Cavity portion" to cut.

1) I`ve tried to import obj to carve it into mold template made in MoI - OBJ was to heavy even after decimation - I can`t go lower. It was very brilliant idea but it`s too heavy to work in that way
2) I`ve tried to export subd for Michael but file has got 300MB, I can`t do booleans merge on it (at all).
3) When I`ve builded that mold I controled all draft angles and pins are directed in same angles like parts inside mold. I don`t know how in MoI I may control those draft angles (in polygons I check it inside Zbrush and create locators which can change world orgin and world direction temporary. I work on many different direction to be sure that every part has got right angles).
4) I know that should be created from scratch in MoI3d but I`m working over few million polys scans creating those parts and I have very low budget that`s why I`m doing it in that way. In other way I would bought Alias, Geomagic Wrap/Design X and Solidworks. I`m doing it with low budget and I produce many parts in that way.

Thanks for your tips.

Hi mdesign,

re:
> 2) I`ve tried to export subd for Michael but file has got 300MB

It sounds like it is a very dense file in its sub-d cage. Is it made up of all quads or is it triangles?

The MoI converter is more oriented towards converting sub-d models with a relatively sparse sub-d cage (with all quads) that was created by someone directly modeling the sub-d cage controlling edge flows, not for high density scanning conversions.

For something like that you're probably not really looking for a sub-d conversion, you'd need to look more for point cloud/high res scan data conversion. Those are pretty different kinds of data. MoI's converter is not meant for processing high density point cloud type data.

You might check out some of the reverse engineering plug-ins for Rhino at:
https://www.rhino3d.com/resources/#tabs-17

But if your model geometry has a lot of little high frequency bumps in it requiring millions of polygons in the sub-d control cage, it may just not be very suitable for conversion to CAD surfaces at all though.

Can you maybe show some of what your sub-d mesh structure looks like?

- Michael

This is how to looks whole thing:






What about that ReSurf? Is it same conversion from poly to subd as in Moi3d or maybe better?

http://www.resurf3d.com/Objmesh2solid.htm

Hi mdesign, what about these areas here, are they part of what you are trying to convert? Because those areas do not have a sub-d topology structure to them:



When you do the conversion into MoI make sure you are not including those non-sub triangle mesh areas and also make sure you're exporting the level 0 control cage for your sub-d objects and not a mesh that has subdivision applied to it instead of just the control cage.


> What about that ReSurf? Is it same conversion from poly to subd as in Moi3d or maybe better?

I think it's a pretty different process, if I remember right it's more like retopo where you sketch out some patch boundaries along a polygon mesh (not sub-d just a plain static triangle mesh) and it fits surfaces to the polygons. I haven't looked at it for quite a while so it may have more functionality now like some kind of auto re-topo stuff in addition to manual topology tracing.

The MoI converter is for sub-d only and exactly converts the limit surface of the sub-d model to NURBS surfaces.

ReSurf could be good for those non sub-d triangle meshes indicated in the above arrows. You should not be running non-sub-d stuff like those through the Moi sub-d converter.

If you want to e-mail the .obj file to me at moi@moi3d.com (using some file transfer service, like dropbox, wetransfer, etc...) I could take a look at it and maybe give you some ideas on what things are problematic.

- Michael

Thanks Michael I will send it to you but I should prepare it before because it`s not prepared to imitate a real problem. I need to change cutters. It takes some time (I`ve already tried this few months ago). Some cutters are not in subd because my production was pure polygonal. I need to change it and then I will try to do that test properly. Next I will send it to you. Thanks it`s very kind that you want to look at it.

Those triangles is a background scan :) (it`s not related with import subd meshes to MoI)

From that site it looks that is a rather subd conversion to cad than triangle mesh 2 cad: http://www.resurf3d.com/Objmesh2solid.htm (please look on images).

Thanks for all info. Thanks Michael also for that Rhino plugins link.

Objmesh2solid is not a reverse engineering tool. It is useful for less precise conversion only and will not produce accurate results compared to the original mesh data.
Quoting from the product description:
"the NURBS surfaces here do not fit to the OBJ mesh"

I`ve understood that quote as: Subd always does not fit to unsubd mesh. Subd is smaller.

I have resrf3d.... it is more of a "drape" surface.

If you want to see its results, i'll run it through for you.

I also have a cnc software if you want me to look at toolpathing it too

Thanks,
have you heard about http://www.grzsoftware.com/ MeshCAM software. I`ve heard that is good for STL milling. Is that true?

I won`t bother you with that. It`s nice to have your opinion (as an user).