fillets - how?

bob z. is designing a die right now. bob z. is at a level of
frustration that is incomprehensible to most humans. check the link
for one of the many problem areas:

http://bobzee1.googlepages.com/filletissues

what would be the best way to *force* a fillet onto these edges? the
fillets are there now, they are just not BIG enough. bob z. was
thinking of this line of attack - what do you think?

1. offset surfaces (both faces) and then trim them and then create a 3d
sketch and use that for guide curves for a loft?

2. bob z. got lost typing number 1, so he can't think of anything for
number 2...

bob z.
p.s. out in the west texas plains of el paso...

 

Looking at the feature tree this seems to be an imported part so it
doesn't look like you have any control of changing or removing fillets
from the feature tree.

that being said....

This sounds like a handy job for the "delete face" and patch feature.
What I think you want to do since the existing fillets are too small...

control select all the fillet faces that make up the area that you
would like to change or remove the fillet in this case. Think of it as
selecting all the faces of the fillet that you would like to set to 0
and create an edge. Once you have all these faces of the fillet
selected,
right click and under the "face" subset there should be "delete face"
option. (If it's not there you need to turn it on by custimizing the
menu). Once you bring this option up select the
"delete and patch" option.

Sometimes you have to play with the order of fillets of some blend into
each other. But hopefully if the geometry isn't too complicated it
will have successfully set those to sharp edges.

If you were able to get to this point you should be able to just add
the fillet size to your liking and life should be good. If you are
having issues with the "delete face" feature...
you may have already killed one of your coworkers by the time you read
this. ; )

Good luck!

 

bob zee wrote:
....


If bob z. can visualize where bob z. would like the edges of the fillet
to be, then bob z. could use split lines to place the edges of the
fillets. This might take some time and might require split lines from a
couple different directions. Then use Delete Face with the Delete option
to remove the faces that are where the fillets are spoda go (between the
edges of the fillets). Then bob z. could loft in fillets between the
edges. If bob z. lofts the fillet in smaller sections, bob z. can even
blend together fillets that collide.

There are magic four letter words bob z. can use to shame fillets into
working, but use that as a last resort, along with beating on the Esc key.

 

oh.. one more thing. If the egdes were sharp to begin with and SW just
won't let you put in a large fillet. Have you tried a "face blend"
fillet? If this doesn't work you may have to get fancy and try loft
faces together after split lines and deleted faces. But hopefully you
won't have to do this.

Don

 

OUT IN THE WEST TEXAS TOWN OF EL PASO...

bob z. just got corrected by someone up. way up. way up high on that
ladder!

bob z.

 

yes, the edges are sharp. the imported feature didn't have any fillets
on it. bob z. has tried the face blend fillet and isn't having a lot
of luck with that, either.

bob z.

 

BOB Z MIGHT HAVE TO LEARN TO USE THE ATOMIC BOMB OF FILLETS. WORKS
EVERY TIME.

EXTRUDE A BLOCK OF MATERIAL UP OUT OF THE SURFACE. THE BLOCK IS A STOP
FOR THE FILLET. IT MUST BE BIG ENOUGH TO STOP THE .25 FILLET. PLACE THE
BLOCK IN THE LOCATION WHERE THE FILLETS HAVE TROUBLE.

FILLET UP TO THE BLOCK FROM ALL DIRECTIONS.

THEN USING THE EDGES OF THE FILLET WHERE THEY INTERSECT THE BLOCK AND
ANY OTHER EDGES NECESSARY CREATE A FILL SURFACE FEATURE.

USE THE FILL SURFACE FEATURE TO TRIM AWAY THE PROTRUDING PART OF THE
BLOCK.

P.S.
This was something Ed Eaton showed me. I don't take credit; I just use
it.


PPS
If fillets as large as you need were formed there, would any of the
starting surfaces be consumed and changed in form? In other words, does
doing what you are going to do change the design, form fit and
function?

PPPS
There are a lot of little sliver surfaces in your imported part. These
are not good. Prior to any work did you run a TOOLS/CHECK with
Verification on Rebuild turned on? CTRL Q. Import diagnostics. Did you
try exporting to VDAFS? VDAFS has a very stringent checker. It may turn
up trouble that other means won't. Did you turn on surface curvature
shading and look for "whopper jawed" surfaces? This is just GIGO
checking.

PPPPS
You can always load a trial version of Rhino and fix it. Sometimes I
wonder about jobs like this. There is really no design intent issue and
history based modeling can get in the way more than help. More than
that, this kind of imported geometry more often than not is not
conducive to SW way of doing things for many reasons.

 

SMA realizes Bob Z's pain but cannot help note that Bob Z is designing
a die and also concerned about making external radii large. What SMA
knows is that external radii on that feature have no value since the
internal radii (on the far side) are the things one cares about since
the radii are on the "tension"side of the material (internal radii on
the die side may be sharp since the radius in question is controlled
from the other side of the material - the punch controls material here
and the material on the die side - visible here - is in tension and
will conform to the punch - the rule is not always true, but looks true
here). SMA also notes a painfully sharp draw radius near the flange -
SMA envisions a ripped part or a part that will perhaps require an
intermediate reduction to get that sharp radius (GRIN).

What SMA has done is steal the faces from the punch side and build a
punch block around it with surfaces only (likewise with the die). SMA
noted while doing this type of punch and die design that using surfaces
made SMA feel very good about life and that trying to carve up a solid
part is just pure pain. SMA now uses surfaces only to do this sort of
work. SMA suggest that Bob Z. might be happy this way too . . . SMA
used to believe that cavity was a good tool for doing complex punch/die
blocks from an imported part, but SMA felt much pain in doing this.
SMA still totally believes in cavity when the draw has clean straight
sides that lend themselves to carving away, but mostly SMA believes in
the utility and good behavior of surfaces for editing these
multifaceted parts will also make Bob Z. happy if he decides to try
this method.

Good luck man . . .

SMA

 

Sometimes I have just reconstructed the part from scratch after getting
enough dimensions one way or another. I can't tell by looking whether
most of the surfaces are prismatic or not.

Working with imported geometry is not my idea of fun. I don't know if
I heard whether or not Feature Recognition worked, but I assume it
didn't do very good.

Even with prismatic surfaces, Radii have presented a problem for me in
getting them to all "work". I have had to spend hours going through
complex parts where radii run through dozens of edges and all have to
blend together right.

I have changed the order of radii, types of radii and sometimes been
forced to add small radii from .01 to .1" on two intersecting surfaces
to get a radii at their intersection with another surface to fillet
properly. When the angle is slight like a draft angle of maybe 5
degrees, I have at times had to put in a 1" to 5" radii on the meeting
of two surfaces, in order to get their edges to Fillet properly with a
3rd surface.

Bo

 

SMA realizes Bob Z's pain but cannot help note that Bob Z is designing
a die and also concerned about making external radii large. What SMA
knows is that external radii on that feature have no value since the
internal radii (on the far side) are the things one cares about since
the radii are on the "tension"side of the material (internal radii on
the die side may be sharp since the radius in question is controlled
from the other side of the material - the punch controls material here
and the material on the die side - visible here - is in tension and
will conform to the punch - the rule is not always true, but looks true
here). SMA also notes a painfully sharp draw radius near the flange -
SMA envisions a ripped part or a part that will perhaps require an
intermediate reduction to get that sharp radius (GRIN).

What SMA has done is steal the faces from the punch side and build a
punch block around it with surfaces only (likewise with the die). SMA
noted while doing this type of punch and die design that using surfaces
made SMA feel very good about life and that trying to carve up a solid
part is just pure pain. SMA now uses surfaces only to do this sort of
work. SMA suggest that Bob Z. might be happy this way too . . . SMA
used to believe that cavity was a good tool for doing complex punch/die
blocks from an imported part, but SMA felt much pain in doing this.
SMA still totally believes in cavity when the draw has clean straight
sides that lend themselves to carving away, but mostly SMA believes in
the utility and good behavior of surfaces for editing these
multifaceted parts will also make Bob Z. happy if he decides to try
this method.

Good luck man . . .

SMA

 

bob z. isn't quite sure he has the brain power to pull that one off.
:~(

bob z. extended the surfaces far enough to allow for the radii to be
formed without consuming the needed surfaces.

bob z. did a 'roundtrip' through IGES and it came back in as a surface
with errors - ran the diagnostics and it fixed the gaps and then bacame
one imported feature.

bob z. has played with rhino just enough to know that he would/could
really screw up this part.
:~)>

 

bob z. is trying to create really large external radii so that the
internal radii on the far side are big - so, yes bob z. is in total
agreement with you (he thinks, anyway because he has NEVER designed a
die before). the painfully sharp radius near the flange will be
bigger, bob z. is still in the in-process stages.


bob z. started out with surfaces on this project. we had a wooden
check fixture (gage?) that was sent out and an iges file with the
surfaces was sent back to us. after going through several iterations,
bob z. ended up with what we see in the picture - one imported solid
feature and fillets that don't work...

Thank you! You have helped tremendously.
:~)>

 

bob z. is going to try this method right now.

bob z.

 

if one of these many ideas don't work for bob z. by about noon today,
bob z. will post this file somewhere on the 'net for download.

you guys have been way too helpful. everyone that has responded to
this thread deserves riches beyond comprehension! you guys rock. all
of you.
:~)>

bob z.

 

Sometimes round trips through IGES are not enough. That certainly does
not eliminate slivers and slivers are what you have. They are as
aggravating in a model as they are in your finger and need to be
removed. No automagic way to do that.

My point about Rhino is simply that the problem at hand really isn't
one in which "Design Intent" comes into play as strongly as "Get the
job out yesterday". Do you have as much time to play with the model as
you do to learn another tool?

 

these slivers are DEADLY.
:-(

very good question. unfortunately, bob z. is not sure how to answer.

bob z.

 

bob z. just got the fillets MOSTLY figured out. bob z. will stay away
from the girls.
:~)>

bob z.
p.s. they had training. *i* have google.

 

This was something I picked up from Jason Pancoasts filleting
presentation in 2001, and I understand that he got it from Keith
Pederson.
All I contributed was recognising its power and showing a few more
common examples, to dissect the "why's" of it, and apparently most
important of all- to tag it with a cute/memorable catchphrase.
It also works with drafts sometimes (and shells, and all sorts of other
problems)
Just want to put credit where it is due (i.e. not on me. As a policy I
don't like to regurgitate other folks stuff, but this one was just too
darn useful. All my ppt slides say I stole it wholesale from Pancoast)
Ed