Hello MoI friends,

I really enjoy using MoI and tell everyone interested in 3D to give it a try but I sometimes have issues and I hope the more experienced users here can take a few minutes of their time to help me out so we can all create beautiful designs.


My first issue(Please see attached images):

1. I create an L-shaped curve and Extrude. Fillet works.
2. I add a triangle shape using Snap, Extrude, and Boolean Union.
3. The fillet does not work.

I hope there is a way to fix this and thank you to anyone who provides a solution!

Hello, welcome to the forum!

It's a big help if you could please post the .3dm model file along with your question. That makes it possible to examine your model in detail, zoom in on pieces and test stuff out which can't really be done just by looking at a screenshot.

Just looking at your screenshot my best guess would be that once you have added the triangle the juncture at this location here is difficult for MoI's filleter to resolve:


That's probably something like a "multiple colliding fillets of different convexity" type of thing. The fillet engine in the geometry library that MoI uses just has not had the hundreds of man-years of work invested in it to recognize all these different kinds of corner juncture cases. There are other CAD programs like OnShape for example that could handle that one probably though.

- Michael

Thank you for the extremely prompt reply. Consider me impressed. Here is the .3dm file.

Thanks, yes MoI's fillet engine just doesn't know how to handle the complex processing that would be needed to handle that kind of juncture area with several different fillet shapes colliding into each other.

Probably your best bet would be OnShape, I was able to get it filleted there. You can see that there's quite a bit of special case handling needed to handle it:



- Michael

Thanks for the explanation. I am fine with working within limitations- right now I am just feeling my way around MoI to see what I can and can't get away with.

Image 1- I created a curve and used it to Boolean Difference the top edge.

Image 2- I select these edges.

Image 3- Fillet works. It's a bit small but I'll take it.

Image 4- I select more edges and Fillet doesn't work.


Basically, if you were to remake this object in a way that is more compatible with the program's capabilities and limits, how would you do it? Feel free to make changes.

I'm not really sure, one strategy that can help is to try and make some areas smooth before filleting since edges that are smooth to each other will have fillets that match each other end-to-end instead of having corner juncture patches needed as when filleting edges that meet at a sharp corner. Another thing that can help in general is to try fusing some smooth pieces together into single faces to reduce the number of edges involved.

But it's a pretty difficult thing to work around, it's far easier to import your object into OnShape and fillet it there, that's what I would recommend.

- Michael

Thanks for the recommendation. I don't know about buying another program just for a fillet though. In general how can I know if MoI can handle something versus other programs? What should I look out for?

Also, I have this issue with another fillet:

Image 1- The curves on a Box after I Boolean Differenced a Lofted Solid.



Image 2- A fillet of 1 works.



Image 3- A fillet of 3 works.



Image 4- A fillet of 2 does not work, even though it's between two working values...

Onshape was free in the past I don't know if it's always the case...

You have Fusion 360 who has a free version...https://www.autodesk.com/campaigns/fusion-360-for-hobbyists

else you have also Design SparkMechanical but i's a little tricky! ;) https://moi3d.com/forum/index.php?webtag=MOI&msg=6186.1

123D Design but i believe that it's not more downloadable

All have robust fillets

A little trick about fillet in MOI when that is blocking with a perimeter selected with very little sharp form or angular corners or maximum admissible

Make the fillet admissible then Trim then remake Fillets
and(without to exit the function) a variable Fillet with 0 at the angles if wished! ;)



but with Trim and variable fillets...you can overpass that! :)

Hi friend, yes filleting is complicated. For your case there I don't think there is sufficient space to fit a natural fillet in the corner spots much larger than about 1 unit or so before it starts to bunch up on itself:








There is some stuff that tries to deal with some kinds of fillets where there isn't enough space for them to fit but it's harder for that mechanism to work when the bunched up area is pretty small. That's why you're able to get some larger radius values in there.

In general it's better to avoid trying to place a fillet in a spot where there is not enough room for it to exist without bunching up on itself.

For your model here the way you would do that would be to not put in the rounded corners in your lofted object and instead have them sharp and round all that off in one single fillet like this:





That way these areas become corner juncture patches generated between fillet surfaces:



In yours instead of the filleter constructing a corner juncture patch it's trying to build a fillet surface between these pieces:



If you start with the sharp cornered shape here you should see a smooth progression of fillets for increasing radius values until they get large enough to run into each other much larger than radius=4:



- Michael

Hi Pilou,

"123D Design but i believe that it's not more downloadable"


123D is discontinued but it's last version is still available for download. I downloaded it recently (not sure from which website). It has a robust fillet and mesh manipulation tools and the good thing about it is that it's free and offline.

https://www.download-3d.com/123d-design

https://softfamous.com/autodesk-123d-design/

Cool for the users! :)
It's of course not the sites of the creators! ;)

Hi
Onshape is free.
2 minutes to import the 3dm Moi file and apply Fillet and export it

Ah cool! I have missed this new thing! :)
It has not more the 5 projects maxi ?

https://www.onshape.com/products/free

Just watched a video about OnShape free version, effective last year, 2018.
All of your OnShape work is in the public domain,
and use is not permitted for "commercial" work.
For casual use, paid versions are extremely expensive IMHO.

- Brian

Yes that's the free conditions! :)

Hello, thank you for all of the information.

Frenchy Pilou, I don't quite understand the first point you made but it seems you were offering a way to make the fillet work somehow? As for the animated gif file you basically cut the model in half and had a higher fillet on the right object using variable fillet? But you can't make the entire object with that same larger fillet?

Michael, so it's best to not fillet the construction curves and instead boolean first and then fillet the solids? Is there any situation when you should fillet the curves first?



Here I have made a simple curve using Polyline.




However when I extrude with Tapered active I get this Joined Surface and not a solid.

Hi friend, can you please post a .3dm file with your polyline in it so I can take a look at your tapered extrusion?

It helps a lot if you can post a model file instead of only a screenshot. That makes it possible to examine your geometry and test things out.

My best guess from looking at the screenshot is that probably the polyline segments here that look like they are simple lines are probably actually made up of 2 colinear line segments (like one line cut in half) instead of just single lines. That's a good example of something that's hard to determine from looking at a screenshot instead of the actual geometry:




> Michael, so it's best to not fillet the construction curves and instead boolean first and then fillet the solids?

Well it can depend on the particular situation.

> Is there any situation when you should fillet the curves first?

If the solid is going to be difficult to fillet it can sometimes be helpful to fillet the curves first so the fillet is incorporated directly into the sweep or loft or whatever.

But if you are going to be putting additional fillets in which are going to collide with the already present ones that's usually better to put in all at once or you can put them in stages if you do larger radius ones first.

- Michael

<< I don't quite understand the first point you made but it seems you were offering a way to make the fillet work somehow?
Fillet admissible : fillet maxi that Moi can do with a perimeter path or curves selection


<< As for the animated gif file you basically cut the model in half and had a higher fillet on the right object using variable fillet?
Yes absolutly


<< But you can't make the entire object with that same larger fillet?
Yes absolutly : Till now Moi's Fillet don't manage that (i tested with Onshape, DesignSparkMechanical, Fusion 360...it's the same)

And if you don't make this trick (maybe other existing) you can't make any "bigger" fillet on your object, only the admissible "maxi" so above 0.5
With the trick maybe 3 on some parts... i have not more the original object...

Michael, I attached the file which gives me problems with tapered extrude as "extrude tapered problem".





<<Yes absolutly : Till now Moi's Fillet don't manage that (i tested with Onshape, DesignSparkMechanical, Fusion 360...it's the same)

Do you mean that the fillet systems of those programs also can't do a higher fillet or that they can? I understand that some shapes can give MoI's fillet a hard time, like the example I started this thread with but what about this?






I think the construction line is preventing the fillet from being larger. What I want to know is: can other programs solve this fillet or is this a universal NURBS fillet problem?

I understand that there is a natural limit to fillets because the trim curves intersect each other:





But is there a way to solve a fillet when there is a construction curve in the way? I also uploaded the file for the fillet issue.

Yes they block at the same value!

Designspark block at this form for your last send!

There is no more material ! it's a slope at 90° :)