Hi Laurent, well filleting can definitely be one of the most sensitive areas.
It involves quite a sequence of pretty elaborate calculations, including generating offset surfaces, then intersecting those offset surfaces, generating fillet surfaces, extending fillet surfaces and intersecting and trimming them with one another, and also generating corner patch areas where multiple fillet surfaces are colliding into one another.
The fillet engine that MoI has is not really the most sophisticated one, it is pretty decent at handling simple cases but if you have more complex corner junctures you may need to use a separate program to do the filleting, it's not one of the especially strongest areas of MoI.
> Is there another app that i can use to apply fillet on MOI model with osx ?
I think ViaCAD has an OSX version, so that could work pretty well as a companion app to help with filleting:
http://www.punchcad.com/c-12-consumer-cad.aspx - you should be able to use the ViaCAD 2D/3D one, which only costs $99, it can also be a good helper program to bring in models that you want to generate dimension and 2D drawings on as well.
Now as far as the model that you posted goes, it looks like it is well constructed, and it actually seems to fillet ok in MoI as far as I can see - however you will be limited to a pretty small fillet radius, like something around 0.02 units max.
MoI's filleter will get confused if you give a fillet radius that is large enough that it cause a whole edge or face to be completely consumed away and if you go to a larger radius than about 0.02 that is what ends up happening, mostly because of some of the prior fillets that you have put on there where you only filleted some of the edges that are coming together at a common juncture like here:
Because you only filleted some of the edges that come together and left some pieces sharp, the fillet pieces will be of different actual sizes where they collide into one another - you can see that if you zoom in there:
So basically after that fillet you now have some much smaller edge fragments in your model and now that will add complexity to more fillets that try to travel along those new edges and especially if you try to use a radius that would cause that little edge to be completely eaten up it will fail.
Because filleting only some areas of a model can lead to more complex structures like this it is usually best to do all the fillets all at the same time instead of only doing a few at a time and leaving some sharp edges in the result. The exception is if you want to put in some fillets that are of a different much larger radius than other ones, then you do the large radius ones first and then all the smaller radius ones in another step after that.
But basically you can see there how some of your initial filleting has added complexity to the edge structure of your model and then that's what is getting in the way of more filleting that involves those same areas.
Your original model before doing those couple of partial fillets looks very clean and well constructed, and you should likely be able to fillet the whole thing to a larger radius than 0.02 if you did it all in one go on your original model before those partial fillets were put on to it.
At any rate if you select just the whole model (you don't need to select edges if you want to smooth everything) and run fillet at a radius of 0.02 you should see it working.
Sometimes it can be surprising how much of the model fillets can consume away, so if you see a problem with a fillet, try going to a smaller and smaller radius so you can see if a small radius one succeeds and what it looks like, especially if you have things that meet each other in sharp angles it does not take much of a radius to eat away a substantial amount of the model. So go down in stages like if the radius you try does not work, try 1/10 of that, then 1/20 or 1/50 of it, etc...
That and the "do all connected pieces in one shot" type thing can help out quite a bit. It also helps out to have clean geometry that does not have excess fragmentation in its faces or edges, and it looks like you did have that before you did some of those partial fillets, so in that area of initial construction you're doing good already. But you don't want things like a planar area of the model that is made up of 3 separate adjacent plane fragments, you want just one big plane in places like that to be more fillet friendly.
With more practice you will tend to get more of a feel for the kind of thing that will cause trouble with filleting and try to avoid those types of configurations.
ViaCAD is not bad to have in your toolbox either though - in general the fillet engine that it uses is more sophisticated than MoI's and can handle more kinds of corner patch junctures and stuff like that.
Hope these tips and explanations help!
- Michael
