Ball Corners 3

[Amocs]

Is there a way within GSD to create a corner on surfaces with different fillet sizes terminating in a true Ball Corner?
For example, i have 2mm, 5mm and a 6mm fillet all running into a internal corner and i want a smooth result.
I have tried Edge Fillet and the blend corner command, and using the set back command, but i cannot find a way of having different fillet sizes.

 

[catiajim]

Three Fillets with different radii will not form a "ball" under any circumstances. You might be able to generate some kind of a Fill Surface using some intersection curves and get some kind of smooth surface, but it will not be any kind of cannonical surface.

 

[Kapitan]

A 'True Ball Corner' is a part sphere and can only be achieved if R1=R2=R3. The internal corner situation is often resolved with (R1=R2)<R3, which gives a part torus, where R1 and R2 could be considered as the corner radius of a cutter and R3 be generated by the path of the cutter centre and the cutter radius.

The (R1=2,R2=5,R3=6) corner case is not smoothly solved, try sketching it out as 45° chamfers instead of radii and the problems will be immediately apparent. By sketching, I don't meant Catia sketch, but pencil and paper.

If this case can't not be redesigned, maybe a result could be found by treating the corner as three surfaces, each having three boundaries. But it will be messy, whatever 3D modelling system is used, it is a geometry problem.

A one-shot Fill solution would probably have 5 boundaries - not good.

 

[RCDLtd]

Hi Amocs,

A "Stamping" ball corner, unfortunately can't be produced in one hit in GSD, that I've worked out any how.

So let the fillets run in together naturally then take a sketch roughly normal to the corner, project up the fillet tans and then 2D fillet/corner them off so you've got something to project back on to the surface to split it by. Then fill with tangency or curvature and join it up.

Long winded, not robust and difficult for someone else to follow that may pick your part up later (if you've got loads of them).

If there's a better solution I'm also looking for it.

 

[Amocs]

Thanks for the replies, but i think i confused the issue when i mentioned a `True Ball Corner`. What i am after is a method the create a smooth blend on any corner consisting of 2 or 3 different fillet radii. When using Ideas, you had the option of inputing different radius sizes onto individual edges during 1 fillet operation and it would calculate a corner surface, if this was not a good enough surface(which generally it was) you had a create custom corner option which allowed you to create individual stetback distances, and it would take into account the different fillet rads and create a suurface which was user definable.
In V5 the best i can get is to run the largest Fillet r=6 into a corner, then use a variable fillet, and change the fillet size (r=2 to r=5)on the start and finish tan lines of the r=6 fillet.

 

[catiajim]

Create the 3 fillet surfaces
Create the Intersects of the surfaces
Create a line on each fillet surface between the end-points of the intersects.
Split your fillet surfaces at these lines.
Create a Fill surface between these three lines, using the fillet surfaces as the "supports" for the fill.

This will create a fill surface that is tangent to each of the fillets while keeping the radius of the fillet as long as possible.

 

[Kapitan]

Perhaps the thread should have been called Blended Corner or Rounded Corner, the Ball was misleading, but it's an interesting problem and there are many things that can be done to bring those 3-radii together. I did find this example:

It appears that the corner has been achieved with surface of 4-boundaries, one of them being planar and the other three laying on the circular fillet cylinders.

Jim, could you please post an Image Capture of what you’ve described, and if you have FreeStyle, put the tangency and curvature visualization on - (black & white stripes). I'm not in front of V5, otherwise I'd try it !!

 

[itsmyjob]

use variable filet function to use several values with internal corner... it works.

Eric N.
indocti discant et ament meminisse periti ​

 

[Kapitan]

Please, post more images so that we can see what all these good words mean. It's not difficult to get a V5 screen shot, 23 years ago whan I started on Catia V1 it was so complicated to get a screen print that we used to get the company photographer to take a picture of the Black and White screen.

 

[catiajim]

Here it is:

http://pg.photos.yahoo.com/ph/jstrawn60/detail?.dir=/5b5bre2&.dnm=6ac3re2.jpg

(sorry, I don't know how to embed a photo here).

 

[Amocs]

Kapitan, thanks i think you understand the issue i have.
Your image is possible using 1 initial fillet, then applying a variable fillet over the top. That works ok, however there is a type of corner which looks equally good but can give a flatter corner radius, and give a different result. In V5 you can create a corner blend like the image below:

What would be nice is if you could vary the input fillets on each edge and let Catia calculate the blend(this is what Ideas can do!)
The example you gave works ok if the fillets are not to dissimilar, but if you vary them too much you can get the following:

Not nice....
Maybe this is a function for Class A surfacing tools and not for the basic surface work expected in GSD!

 

[solid7]

I didn't have any problem at all with blending the corners, using an HD2 license.

Check it out. Although I didn't have the screen units set to Metric, I typed the values in. (2mm, 5mm, 6mm) I made this using variable fillets on each edge (with one operation) and the value at each end of each edge the same. Then, I selected the "More" tab, and came to the "blend corner" button. You have the option to select the vertex of the edges, and define a SETBACK distance, which takes care of the problem in your second picture, there.

If the text in the pictures is too hard to read, follow my links to the contact page on either site, and I'll be happy to email you the full size versions.

Hope that helps.

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CAD design engineering services - Catia V4, Catia V5, and CAD Translation. Catia V5 resources - CATBlog.

 

[Amocs]

Thats exactly what i have been looking for!!! Thanks....