Why Can't I Apply a Fillet to This Edge?

brian_wolf

Hello, all. I have no formal CAD training. I have fiddled with the free/hobby versions of a couple different programs. I apologize in advance if I don't use correct terminology, or refer to things in roundabout ways, and I appreciate you bearing with me. 

I have a sketch that I've extruded, and successfully added a few fillet features to. For some reason, I can't get the last bit to cooperate. I've tried using arcs in the sketch. I read in the forums that someone suggested using splines, instead. That hasn't worked for me, here. Will someone please help me understand why I can't apply the fillet? If anyone has a solution, I'm all ears. Thank you. 



Here's a link to the document: https://cad.onshape.com/documents/1b6d3b7bb068c0ed612ac43d/w/83eac526b7f01a2561af0b82/e/7ba073434c9b1b440b77dfb2

NeilCooke

Instead of selecting “add” in the extrude feature, choose “new”. Add the fillets then use Boolean/Union to add it back to the main solid. 

brian_wolf

Thank you for your reply, Neil. The cylindrical piece and the filigree-looking piece are two separate parts. I should have changed the color before posting. Here's a couple more pics for reference: one with parts better differentiated, and one with just the part in question. 

NeilCooke

It looks like the extrude is thicker than it is wide - if you are trying to make a full round fillet, the face created by the sketch should be "bigger" then the depth of the extrude, otherwise the fillet will self-intersect. Not easy to explain, hope you can understand!

brian_wolf

Your response makes sense. Like, if the width is 5mm, and I'm trying to apply a 3mm fillet to each side, that won't work, because there's not 6mm to work with. Am I understanding correctly?

The whole extrusion is a uniform thickness, and certain parts will accept a fillet no problem. The extrusion is 10mm, and each side is 5mm. I've even split up the spline forming the rounded bit, in case there was an edge condition that was messing up the fillet application. I can't identify anything going on with the curve that won't cooperate with the rest of the part that I didn't have a problem with. 

It might be worth noting that these edges will not accept any size fillet. 

brian_wolf

If I select the last little bit, I can get it to accept a 3mm fillet. 

3dcad

Without diving deeper into this; usually when I have a failed fillet and I feel it should work I can get it solved by changing the order of fillets in feature tree or make separate parts, create separate fillets and then boolean unite back to single part. Sometimes it's also necessary to select all edges into single fillet to make it work.

brian_wolf

Thank you, 3dcad. I gave that a shot, and it still won't work. Oddly, it won't even accept the 3mm fillet now that it's a separate part. New geometry could account for that, I guess. 

I really appreciate the feedback. This thing is so aggravating. 

NeilCooke

If you paste the URL to your doc here we can take a closer look. 

owen_sparks

It's in the first post Neil.

Jake_Rosenfeld

@brian_wolf

I very much suspect that it has to do with the line across the part.  Is this an intended modeling feature, or was the whole bump intended to be a cylinder?

brian_wolf

Hi, Jake. I was trying to achieve a specific shape based on a reference image. That line is just a result of the arc/spline combination I used to try to get the shape. I tried making it all one spline, but it didn't make a difference. Picture, below. 

3dcad, I also tried changing the feature tree order, and I tried toggling tangent propagation, but that hasn't been successful, either.