Was wondering if some one could give me a push in the right direction. I need to put the finishing touches on this with fillets and such but it's not wanting to do it the way I am trying. I don't know maybe it's all wrong (I hope not).
Thanks
Bill

Michael will probably give you a good analysis of this object, but at first sight, a lot of the surfaces and edges don't have tangent continuity. This will make it really hard for the fillet engine. How did you make this and what is it supposed to be?

Thanks for the reply. My back ground is in Machining and Design work including 2d and 3d cad I am now using Alibre for my modeling software and now have a need to use MOI so the surfacing thing is all new to me. How I did this is I started by drawing curves with points and then used the network feature to make the surface then Boolean the surfaces together and extruded to thickness the bottom ribs were sweeps then planar and copied to the body of the part. Wrong or right I don't know I guess I am learning as I go and that's why I am asking for help. The part is just a genaric plastic cover I thought was a good place to start.

Hi Bill - it looks like you're building this sort of one little sub-patch at a time, maybe with sweeps or network?

In a case like this where you've got a somewhat irregular outline that you want the final shape to follow it tends to be better to initially build a larger more simple extended surface and then use a boolean or trimming operation to generate the irregular outline rather than trying to construct surfaces that hug the outline directly right from the start.

Doing it in this other sort of patchwork manner has ended up with surfaces that are nearly smooth to one another but not quite - all the various pieces you've got here are meeting each other at shallow angles and that kind of situation is particularly difficult for the filleter to handle.

When 2 faces meet at a crease instead of meeting smoothly it means that the fillets generated from different pieces will also not meet up smoothly where they collide into each other and that means that they have to be cut back and a corner patch put in to blend that area together. But it's difficult to form corner patches very well when the angle is very shallow, the corner patch would need to be kind of compressed or sometimes just a little tiny slivery thing and often times the fillet engine will get confused if the fillet you are trying to calculate contains those kinds of difficult-to-handle things in them.

Instead of building in this kind of patch-by-patch manner instead try to initially ignore the outside profile of the shape and instead focus more on the overall full surface form that you want to have.

So for your case here maybe you would draw in just 2 curves like this:



And then do a sweep to make one big extended surface patch. Maybe think of this more like your base stock material:



Then get your outline curve as just a 2D outline curve drawn in the Top view like this:



In the 3D view it looks like this:



Then you can use the Edit > Trim command to cut your base form with that 2D outline, slicing it into pieces like so:



Delete the portion you don't need:




Then you can thicken that surface into a solid using Shell or Extrude.


If you construct your object more in this manner, it will make a much higher quality model that is all smooth throughout its whole interior and also contains a more sort of uniform shape throughout it, since it comes from just 1 constructed surface instead of a patchwork of them constructed separately. See here for some more examples of how constructing surfaces independently tends to make for creases between them:
http://moi3d.com/forum/index.php?webtag=MOI&msg=1398.18
http://moi3d.com/forum/index.php?webtag=MOI&msg=1398.19


So something constructed out of one larger smooth surface will be much more cleanly formed and should then have a lot better shot at being filleted.


Also though if you've got some pretty tight bends in the outline you may want to leave them sharp and then make it get rounded out by filleting as well - if your object has tight bends in it, that can limit the fillet radius to have to be less than the radius of that bend because otherwise it would cause the fillet to get bunched up on itself, see here for more discussion and illustration on that:

http://moi3d.com/forum/index.php?webtag=MOI&msg=4828.3
http://moi3d.com/forum/index.php?webtag=MOI&msg=4773.7

- Michael

Hi Bill,

> How I did this is I started by drawing curves with points and
> then used the network feature to make the surface

So you do definitely want to draw curves to create stuff like this but try to focus first on the full overall surface contour that you want to have and then start by building a larger surface that has that overall form to it.

Then slice off pieces of that larger surface with other profiles in order to get the final outline rather than trying to generate surfaces directly to them right from the start.

It's a lot more difficult to get a good result by only using direct surfacing for everything.

Basically stuff that should be smooth to one another is usually best to be made up of one big surface instead of a lot of smaller fragments.

It's really hard to get good quality with the fragmented type approach - having a lot of extra edges in the patchwork is another thing that makes it much more difficult for filleting - areas where you have things like 5 or 6 edges all radiating out from a single point will also make for much more difficult corner patching situations for the filleting.

- Michael

Hi Bill,

Not sure what the dowel shapes on the underside of your object are, but here is an approach
to create a more uniform solid that will fillet more easily.

I traced a top view and created 4 contours that I lofted, then used the top trace to boolean intersect
with the lofted face. If you Show points on the result you can work with a simple cage to smooth if you wish.

3DM file attached....

HTH



EDIT: you have to be fast to post before Michael... ;)

Hi danperk, well more examples certainly won't hurt anything! :)

- Michael

Not exactly the same methods ;)

Wow what great instruction you guys are great and I really appreciate the help. Now all I have to do is work on doing it the correct way. I'm sure I will have other questions that come up but it is nice to know that this forum is so responsive and helpful.
Thanks again
Bill