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Flaw in the way fillets are done?

16 REPLIES 16
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Message 1 of 17
tims79
897 Views, 16 Replies

Flaw in the way fillets are done?

I think this is a flaw in the way Inventor processes fillets.  I tried to illustrate with the attached pictures.  I realize that I could get around it in this particular instance by changing the order of the features, but that's not always the easiet way, or the way it would be machined.

16 REPLIES 16
Message 2 of 17
JDMather
in reply to: tims79

How would it be machined?


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Message 3 of 17
tims79
in reply to: tims79

Well, material is certainly not added during any machining operation.  Here is another example.

Message 4 of 17
Hell-If-I-Know
in reply to: tims79

I know what you mean.

I've run into these issues numerous times, but I'll be honest with you, fillets have always been a problem for CAD programs.

Ever since I can recall, even on high end CAD programs such as Pro/E and CADDS5i, fillets would be a challenge to model.

Typically it comes down to the order you select the edges. Some you can do all at once, others you have to do individually and again, it's trial and error as to what order you select them in.

 

But please, let us know how this should be machined and I'll be more than happy to take a shot at it if I have the chance.

I enjoy these types of challanges.

Message 5 of 17
mcgyvr
in reply to: Hell-If-I-Know

ha that is funny.. Never run across that before.. 

That clearly should happen. 

Dragging the EOP part marker above the upper extrusion then adding the fillet then moving EOP marker back down fillets correctly..



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Message 6 of 17
Hell-If-I-Know
in reply to: mcgyvr

Correct, that or putting the fillet in at the sketch stage works also. But I'm not fond of fillets and chamfers done in sketches.

 

But I do recall one of the big "tests" of years ago was to model three cubes in a pyramid form with corners lined up with corners and attempting to fillet them.

Today, we have more options available to make the fillets work correctly. A lot of the issues come from lack of planning for that fillet ahead of time.

Message 7 of 17
blair
in reply to: Hell-If-I-Know

You could try a Split-Face on the face to stop the fillet,but it seems like an error to me.


Inventor 2020, In-Cad, Simulation Mechanical

Just insert the picture rather than attaching it as a file
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Message 8 of 17
Dennis_Jeffrey
in reply to: tims79

3D Modelers always do what you tell them to do....

 

Tell me how I did this?   Inventor 2011 SP1.

 

000147.PNG

 

000146.PNG

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Message 9 of 17

Hint.... It mimics the machining process. Like JD and others, tell me how you would machine this part?

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Dennis Jeffrey, Author and Manufacturing Trainer, Autodesk Inventor Certified Expert
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Message 10 of 17
tims79
in reply to: Dennis_Jeffrey

I'll tell you how you did it - I can see in your browser that you used a split feature. 

 

I kind of see what you're saying.  But I'm not sure I totally agree.  Here's another example.  Let's say I begin with the attached, then later I find out we need to add a slot to this block (second attached). 

 

Tell me how would you machine that?  The only way to get this to look right is to add the fillets in the sketch for the slot.  Correct?  Which is fine, I suppose.  But I was always told (and I agree) best practice is to use fillet features instead of sketched fillets.

Message 11 of 17

I agree about adding fillets last.  It gives you the most flexibility.  But in your latest screen caps, it looks like your 2nd slot ends exactly where your 1st slot begins.  I think that is forcing the program to include geometry from the 1st slot into the fillet operation.

 

Try adding fillets as a secondary extrusion operation, or, modify your sketch to include the fillets, or, make your 2nd slot not end at the same exact point as your 1st slot.  Maybe one of these suggestions will get you by your issue.

 


Stephen R.

Message 12 of 17
Dennis_Jeffrey
in reply to: tims79

If you add the slot as a new, separate machining operation, that top face is already flat. I think you are missing the point that others and myself stated about how would you do the machining. Working in 3D is a mathematical operation, not a mechanical one.

 

If the slot was created as the first machining operation, it would have that radius. A second path would then be required to make the top edge flat.

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Dennis Jeffrey, Author and Manufacturing Trainer, Autodesk Inventor Certified Expert
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Message 13 of 17
tims79
in reply to: Dennis_Jeffrey

I know, that is why I explained about adding the slot second, and what I feel is an error in how the fillet gets calculated.

 

In your previous response, you said Hint... it mimics the machining process.  You kept asking me how I would do the machining.  So I told you how it would be machined, now you are saying its a mathematical operation, not a mechanical one.  I think you are contradicting yourself.

 

I suppose it's not really an error, just the way the software works.  I will have to learn to live with it.

Message 14 of 17
JDMather
in reply to: tims79


@tims79 wrote:

 

I suppose it's not really an error, just the way the software works.  I will have to learn to live with it.


SolidWorks returns the same results.  Pro/E returns behavior you are after.


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Message 15 of 17
jakefowler
in reply to: tims79

Hi,

Thanks for submitting this case.

Unfortunately, this is one of those cases where a subjective decision has to be made by the modelling team over which solution to provide for an operation with multiple possibilities. When designing algorithms, we base these decisions on customer research and feedback, but unfortunately no one solution will suit every case.

I’ve spoken to the Fillet development team about this case, and they agree that we could do better here (an ideal might be to somehow provide a choice from both solutions). They asked for this case to be submitted as a defect so that this example can be examined further - machining technicalities aside, we would obviously still like to offer our users maximum freedom to explore shapes when creating their models. I've logged this as 1393252 in our defect tracking database.

Fortunately there are alternative workflows for your two examples to achieve the results you require; but if you encounter any models which can’t be worked-around, we would be very interesting in taking a look at these.

Thanks again for taking the time to submit this!

Jake



Jake Fowler
Principal Experience Designer
Fusion 360
Autodesk

Message 16 of 17

Jake

 

You’re welcome for submitting the issue, and thank you for looking into it.  Your response is completely satisfactory to me.  I can see how this is sort of a “you say potato, I say potahto” kind of thing. 

 

There are ways of getting around this one, so I don’t think I will run across one that can’t be worked-around.  But if I do, I will try to pass it on.  I think the idea of having the option for either solution is a great idea.

Message 17 of 17
scottmoyse
in reply to: tims79

i get what you are saying fella, and fully agree with you. it is odd behaviour. It would annoy the hell out of me as well, especially since it doesn't show it in the preview. Its not only adding 'material' as you put it (even though an internal corner fillet does), it is creating a weird quirk.  easy to work around by shuffling the order features are created, but annoying nonetheless. You are choosing to fillet a selected edge, but INV is deciding to extend the fillet long another edge that hasn't been selected. i suppose its seeing it as a face to face fillet.


Scott Moyse
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