Fillet Question

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 From:  jetblast
6806.1 
I was wondering is it possible to put a 1mm rad. fillet where the flange meets the cylinder and have it go to zero as it runs into the big radius ?
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 From:  Michael Gibson
6806.2 In reply to 6806.1 
Hi jetblast, often times the fillet engine that MoI uses has difficulty with "disappearing fillets" where a fillet runs along an area where surfaces become tangent to one another like in your case there.

So I think probably you won't be able to do that fillet in MoI directly.

If you use Edit > Separate on the 2 surfaces there to break them into individual surfaces, you can then select the 2 surfaces and do a surface/surface fillet to generate a fillet segment like this:



That may give you something to work with and then you'd need to do some manual modeling to fill in the end parts.

The easiest thing would be to try importing the model into ViaCAD, it has a fillet engine that can handle those "disappearing fillet" cases a lot better.

- Michael

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 From:  Michael Gibson
6806.3 In reply to 6806.1 
Hi jetblast actually I guess that's not a "disappearing fillet" type case by default, but it still seems to be a corner situation that MoI's fillter does not handle very well. It needs the side face to be extended like this:



Then you'd need to use "variable radius fillet" to make it go to zero radius at the ends, in MoI that would be by expanding the "Fillet set" option and creating a new point set with 2 points one at each end with a zero radius on it. But since MoI has problems with that corner condition in general it's probably not going to work in MoI.

Maybe it would have better luck constructing it with a straight rising piece.

- Michael
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 From:  Michael Gibson
6806.4 In reply to 6806.1 
Hi jetblast, the more that I look at your case there, the more uncertain I am of exactly what kind of result you want to have...

It seems like it will be difficult for the fillet to go down to zero radius at the tips there and still interact very well all the other surrounding surfaces.

If you have a piece like this:




That will make the "taper to 0 radius" part have to be a sudden shift in shape and try to abruptly taper off, that has some difficulty.

If you try to make it do it more gradually, then it's probably difficult for it to fit exactly within the available space... it would still probably have to be a sharp corner in that area similar to the ViaCAD screenshot above, probably some of the fillet would be sliced off...

- Michael
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 From:  blowlamp
6806.5 
I got a pretty good result in ViaCAD by using the By Position option under Variable Blend. The orange coloured face was done this way with a 1mm radius near to the middle of the edge and 0.01mm radii close to each end. It looks as if ViaCAD's fillet engine fades the radii to zero at the extremities from what I can see.



Martin.
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 From:  jetblast
6806.6 
Thanks guys !


bz
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 From:  OSTexo
6806.7 
Hello,

Is something like this helpful?

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 From:  jetblast
6806.8 In reply to 6806.7 
Yes, that's what I was looking for.

Please show me the 'magic' .... lol
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 From:  OSTexo
6806.9 
Hello jetblast,

Please see the attached image. First create a rectangle, fillet the corner of that rectangle closest to the edge you will be using to create the filleted corner and center and align the rectangle to that seam. Run the Sweep command using the rectangle as the profile and the arc edge as the rail. Before completing the command make sure to select Both Pointy under the Ends tab of the Sweep command. You should be left with a shape that looks similar to the one pictured. Select the two outside and two inside faces and delete those, leaving the fillet shape. Run the Trim command using the swept fillet as the trimming object against the solid. Hide the swept fillet, and delete the two trimmed faces. Unhide the swept fillet and Join the fillet to the rest of the object to create a watertight solid. I admit I was thinking about this a while to come up with something that worked, it might even be interesting to experiment with scaling rails on the sweep to see what other shapes are possible.

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 From:  Frenchy Pilou (PILOU)
6806.10 
Tricky!
---
Pilou
Is beautiful that please without concept!
My Gallery
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 From:  kevjon
6806.11 
Good solution OSTexo,

I come across this problem occasionally too and there is no easy way to solve it with conventional tools.

Your post is very clear and easy to understand.
~Kevin~
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 From:  jetblast
6806.12 In reply to 6806.11 
VERY COOL, OSTexo !!!


I took the easy way out .... lol

Not what I exactly wanted but I can live with it.

I like your solution better.
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 From:  OSTexo
6806.13 
Hello,

Glad I could assist. I'll have to keep this technique in mind in case I run into a similar issue with filleting.
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 From:  jetblast
6806.14 
I down loaded a trial version of ViaCad and stumbled my way through to get something close to what I have in MoI. It gave the same result as MoI
but it did allow me to radius the outside edge (0.5 R) where as in MoI, it tried, but it didn't finish the deal ...
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 From:  OSTexo
6806.15 
Hello jetblast,

You could keep that fillet that MoI generates and use it to Trim away and delete the undesired part of the solid. Then try to Join that fillet to the rest of the surface to see if it's watertight.
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 From:  Michael Gibson
6806.16 In reply to 6806.14 
Hi jetblast,

> where as in MoI, it tried, but it didn't finish the deal ...

It looks like MoI's filleter got confused in the part of the process where it cuts away space in the main object.

When it runs into an error like that, it still returns the fillet surfaces that it was able to generate so you can use them, like OSTexo mentions above you can probably use the Trim command to cut the main object and then join the fillet into place in that case.

The geometry library that ViaCAD users does tend to handle a lot more fillet corner juncture type cases than MoI's though so it's not a bad idea to use it to assist with filleting like that.

- Michael
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