Hi,

I'm following some of the online tutorials, and I came across this problem.



I want to fillet the top (selected) edge but it just won't do it.

I attach a copy of the file for anyone interested.

Mark

zoon in very closely to the model's vertical centerline. You will see that the surface edges are not planar with each other. There are tiny overlaps which need to be trimmed back...

how to fix it... Once you trim the surfaces back, you can create surface blends between two opposite faces (either the top and bottom pairs, or the left and right pairs). then create the next 2 surfaces using Sweep. Join all together, and the boolean should run fine... But i think your model could be developed much cleaner using a simple revolved surface for the top and bottom faces, then using a curve to boolean the shape from the top...

jonah

Hi Mark, here is a screenshot of a zoom in on that center area so you can see what Jonah is referring to:



There is a tiny slivered surface on the top there, and because of that the edge structure is not totally clean there, instead of one big long edge there are several little tiny edges in that area.

Little slivery pieces and edges like that really cause a lot of problems for the filleter - it has to try to construct rounded corners in places where multiple edges meet.

Also an additional problem is you've got pieces here that are close to being smooth with one another, but are just a few degrees off from being smooth. This kind of shallow angle between pieces also makes things difficult for the filleter to calculate intersections properly, it is better when things either meet really smoothly or sharply.

For example in this case the outline for the shape from the top looks like this:



The end tangent direction of the curve is defined by the last 2 control points, circled above. In this case, these are not horizontal with one another, the line between them forms a slight angle, so the shape you construct from them will also have a slight angle in it and mirroring such an object forms a slight shallow crease at the mirror juncture.

I've attached here a version test8_new.zip, where I have reconstructed this object after using Transform/Align to true up those 2 end points with each other to make them meet smoothly. This version should now fillet ok.

One quick note on filleting - sometimes a nice shortcut for filleting is to select faces to fillet instead of edges (all the edges that belong to the face will then be filleted). Like to fillet all the top edges in this case you can select the 2 top faces instead of all the little edges.

- Michael

Thanks everybody,

I sure learn things day by day.
The actual model was created by two separate extrudes and their boolean merge.
I guess I had to be more careful with the drawing of the initial curves.

Thanks again, I'll have a go at it and let you know.

Hi Mark,

> The actual model was created by two separate extrudes and their boolean merge.

That works - there are a few other possible ways to go about it as well. Usually I do one extrude and then boolean difference the extrusion with profile curves.

You usually don't have to do an extrusion of a planar profile curve to use in a boolean, you can just use the curve directly. The booleans know to incorporate an automatic extrusion built in to them.


> I guess I had to be more careful with the drawing of the initial curves.

Definitely it is a good idea to invest time in the initial curve setup, any inaccuracies or problems at that stage tend to kind of cascade into larger problems as more things are constructed from them.

If you check out that test8_new.3dm file attached above, the curves are in there as hidden objects that can be shown. You can see there the closed profile that was extruded, and then the 2 cutting profile curves. Actually in this case that can be generated all in one step by selecting all 3 curves and doing boolean merge. But I kind of like doing just one extrusion first to see what that looks like.


Let me know if you get stuck on anything.

- Michael

Consider also - it's often a good idea not to overdefine your curves. For example, you could draw the "Top" profile curves as 4 simple arcs, without any fillets or blends where they join. The advantage is that you'll have more possible variations when filleting the solid model. Simpler curves also tend to create better models...

jonah