I'm only a newbie to MoI and 3D printing. :)

But I am finding I have less problems if I export to STL and check for "holes" in meshlabs has I create the model.
i.e after using merge to cut a solid in half, I will export to STL and test in meshlabs for holes. I have found a few times that MoI will report a object has solid but meshlabs will report a hole, most often along a edge where the solid was cut. I also find exporting to STL and testing for holes helps when trying to figure out why a bunch of surfaces will not join into a solid.


Cheers, steve

Hi Steve,

> I have found a few times that MoI will report a object has solid but
> meshlabs will report a hole, most often along a edge where the solid
> was cut.

That could be a bug - if you run into that situation again can you please send the model to me so I could test with it?

There are some situations though where you can possibly have mangled geometry like self-intersecting surfaces (surfaces that fold back over top of themselves) and things similar to that which can still read as an object type of "solid" but not be suitable for 3D printing with that kind of geometry.

I think you posted one a while back where it was a trimming boundary that had gotten mangled somehow? The tricky thing with that is that the bug is in the thing that actually produced the mangled geometry, not in the STL export itself. The STL exporter needs to have well formed geometry (no self intersections, no curly-cues or doubling back on trim boundaries, etc...) in order to produce a proper STL result.


> I also find exporting to STL and testing for holes helps when trying to figure
> out why a bunch of surfaces will not join into a solid.

The "Select naked edges" script which you can assign to a shortcut key can be useful for finding that out while staying inside of MoI.

Set up a new shortcut key (I use the N key myself for this), and for the command part of the shortcut key paste in the script shown here: http://kyticka.webzdarma.cz/3d/moi/#SelectNaked

Then when you push N any edges that are not joined to other edges will become selected so you can then see where you've got holes.

- Michael

Hi steve

The better / cleaner your models are the easier they are to output.

A couple of quick tips (ignore if you know this already or it is too far back to basics)

When you select an object it will say up the top right hand corner (solid) which is usually pretty good
If it changes to a "joined surface" at any point I start looking for reasons and backing up.

To get clean results you will find that when cutting solids (boolean difference) either with another solid or a surface it pays to have some overlap where the cutting object goes beyond the outside surface of the solid.
If the cutting object is flush with the surface it often leaves a messy surface or the solid becomes a joined surface which will not print.

If you find when joining 2 solids (union) and you see they go from 2 or 3 solids to a joined surface you can back up (ctrl Z) and either move 1 solid slightly or scale it slightly (even .5% can be enough) and try the union again, often this will work.

Also I find that rather then join 20 solids at once, select 2 or 3 at a time which will often union then add the next ones, then next etc untill done.

If you use booleen difference rather than chamfer to angle an area or shape a surface you can control the result more

For example with the following bezel



If you camfer the inside edges you get



whereas using a cutting solid that goes beyond the surface (made by rail revolving an angled line to form the cutting solid)



As you can see you get a much cleaner inside chamfer.



Some of this stuff can take months of trial an error to figure out

But when it all goes wrong and will take hours to backtrack or redesign and you find some bad edges or faces that are just too difficult and time consuming to find or fix (I know purists will cringe)

there is a great service on line that you can upload your stl model to for repair, then download it back

http://cloud.netfabb.com/index.php

I use a program called minimagics 2.0 to check my models if it gives you the OK you can guarantee it will print.
Which comes from Materialise who is the company featured at the top of this post by fabien

cheers
shayne

Yeah I (as a nurbs modeler) do learn every day. There are so many possible solution to come to an end result with Moi.
It is trial and error... :-) but a lot of fun.

Peace,
Rich_Art. ;-)

thanks for the tips Shayne