Rounding tool mysteries

[BrianBoman]

Part - I have a skin with an orthogrid modeled onto it and I am trying to round the floor of the pockets.

Issue - I can fully round the entire part but only if I break up the rounding effort. There are specific pockets which are happy to solve on their own accepting a round, however, if these pockets are grouped with adjacent pockets the entire round fails.

All of the geometry is identical and has either been patterned or created using the same features. 

Any ideas what could be causing this? 

[StephenW]

You can almost make a career out of rounds in Creo. 

Rounds have always been very pick order sensitive. You'll be working along and you'll find a round that won't work and then when you re-pick in a different order, they work just fine.

One possibility is you could change your accuracy. Possibly from relative to absolute (if it's not already that way). Then maybe reduce the accuracy until it works. Always be careful with accuracy and save everything before adjusting it because you can get failures that are completely unexpected.

[Patriot_1776]

As Stephen mentioned rounds can be a career.  Try using "Intent Edge" and see what that does for ya.  Also, you can set up "rules" to pick.  When you pick an edge to round, pick the "Details" under the "Refernces" cell, and that allows you to do some neat things.

Sometimes, you just have to group rounds the way the system forces you to.

[BrianBoman]

All good tips. I was actually using the datum reference feature combined with the find and select binoculars since with the datum reference active you gain access to the geometry selection filter. I was collecting edges based on "does not belong" and "does belong" and unfortunately the rounding tool made this much more difficult than it needed to be since the edge collection had to be done manually to an extent.

[BrianBoman · Accepted solution]

"

Topic: Rounding tool Mysteries 
Date: 01-08-2019 12:05 PM

Did it solve your problem?

Click here to view the replies and mark one as an Accepted Solution.

This helps others find helpful answers in the community too!

"

No. It did not. As a heavy Creo user I can say the state of the round tool is a burden on anyone who uses this software. I developed a technique to make heavy rounding easier (over 4000 edges), however, the round tool fails...Repeatedly. When I go into another CAD package I do not see the same issues with rounding. The solution is for PTC to make the rounding tool more robust.

[Patriot_1776]

Hmmm, picking 4,000 edges sounds excessive to me, it does not surprise me that it would fail.  I would tend to want to make the rounds based on other features where it makes sense (e.g. one area of the isogrid you make at one time) instead of trying to round everything at once, then simply writing a relation to make the radii equal.  That's a recipe for failure no matter how you slice it and is the LEAST robust way to do it.  For instance, one feature (e.g. a rib in the isogrid) fails, now that 4,000 entity round fails, then and rounds based on that fail.  If you did it in sections that made sense, only THAT round and the children would fail.

"Isogrid" to me means NASA work, or contractor.  Before I took my current position I worked at Sierra Nevada Aerospace on the Dreamchaser.  While I never worked specifically on isogrids, the similar rounding issue I had was when I worked for Royal Appliance (Dirt Devil - late '90's) and had to work on the back panel of a vacuum cleaner (over 1,400 features - a nightmare of shapes, draft, and rounds), so, I can relate.  I found that, as I suggested, breaking the rounds up into areas that made sense made the model much more robust.

Best of luck!

[BrianBoman]

Frank, 

I appreciate your response. This is for that type of work. I did break up the rounds. However, there are edges if even grouped with 1 other edge, will not accept a round, then will accept a round if selected by itself. There are edges that will solve with rounds at .1235, but not at .124-.125, then will solve again at .126. So, I do appreciate the help this community has tried to provide but the rounding tool needs some serious work. 

Thanks, 

Brian

[Patriot_1776]

Yeah, I feel your pain bro.  Been there, done that.  Get used to using the Pro/FANITY and Pro/WORKAROUND modules!

In doing a lot of plastic work over the years, I've run into case where rounds won't mirror.  On geometry that WILL mirror, the round that works on the right half does NOT work on the second half, and everything in between.

I didn't work at SNC long enough to try it, so I'll suggest it to you:  I'll bet that on anything with an isogrid, or similar type of geometry with lots of ribs, you could save weight without sacrificing stiffness or strength by adding draft to the ribs.  I'll bet a couple degrees of draft on a large bulkhead of isogrid or similar could save a lot of weight with little or no negative effects.  I mean, they're going to machine it with a ball-end mill anyways, right?  So, it's nothing more than a little bit of extra coding at the NC end.  I'd love to see it done both ways, then an FEA analysis done on both versions to prove out my theory.  I mean, it's what, $10k-$15k/lb to lift into LEO so cutting a few lbs at a cost of a minimal cost in machining time would be worth it, no?  Are you willing to be the guinea pig on this since I can't no longer do it?  🙂

[BrianBoman]

That is an interesting idea. I can guarantee I will will investigate the idea. That's for sure. 

Ah, the infamous free modules! Still makes me smile....and cringe.

Thanks for all the tips, Frank. It was all much appreciated and insightful.

[Patriot_1776]

You're very welcome Brian, I'd love to see how that turns out.  I had the idea from looking at cantilevers where it was noted that the beam height at the far end from the fixed end didn't have to be as tall as at the beginning, that the extra material was not helping stiffness.  The isn't the greatest example of what I mean, but I think it gets the point across.

Please keep me in the loop if you do FEA's of both types, I'm dying to know if my theory is correct.  I'd imagine on larger pieces (rocket ring frames, large bilkheads, etc.) the weight savings could be substantial.

BTW I "friended" you here.  🙂