Fasteners fail

[346gnu]

Creo3.0 M030

My surfaces are flat, holes are co-axial, only 2 components, the most benign model imaginable and  (grrr) ITAR.

Original geometry from Solidworks.

No lead in chamfers (first thing I dealt with).

Any thoughts?

(I have resorted to the old fashioned shrunken beam method)

Thanks

[danderson]

Do the holes that the threads are screwing into have a counter bore? Those are also not allowed.

Do the holes break through creating a non square edge for selecting the fastener ending reference? In that's the case you'll need to first create a surface region to square off the bottom of the hole.

Also make sure there are no c'bores, rounds, or chamfers in the entire length of the fastern.

Hope this helps,

Don Anderson

[346gnu]

Don,

No rest for you either eh?

This is a typical hole, fastener edge references highlighted.

Fastener head has smaller diameter than its counter bore.

I've done 1000's like this and have never encountered an issue with this typical geometry before.

There's just something 'funny' and I can't find it.

I will try removing the point, square the end off.

Thanks

Charles

[346gnu]

The following doesn't help :

Making the threaded hole square ended

Making the holes in both parts exactly the same diameter

Messing about with accuracy

[danderson]

Have you looked at the head diameter or seperation diameter? Might be to big for the counter bore.

[346gnu]

I have a contact interface defined so there is no separation diameter. Fastener head surface region is smaller diameter than the counter bore surface diameter.

The message states that it cannot automatically detect the contacting surfaces even though there is one defined, the surfaces are normal to the fastener axis, hole axes exactly co-incident and there are only 2 components/1 interface. Is it looking in the wrong direction some how?

I am still suspicious that it has something to do with the non-native geometry. I believe that if I were to re-model as native geometry, the problem would just go away. There isn't anything special about the geometry.

When the model is run (no external loads) after dismissing the message, the contact region is ignored and all the fastener measures are all exactly zero. The software only does one pass. All very odd.

I don't think this will be resolved but should anyone remember this thread in the future after having come across and fixed the issue, please resolve this thread.

The old fashioned method works well as usual; albeit time consuming prep when there are many fasteners. In this case faster than remodelling.

Thanks

[JonathanHodgson]

Do the holes that the threads are ******** into have a counter bore? Those are also not allowed.

Seriously - this got swear-filtered?!?  What the &$£&^%*~??!

Toby Metcalf‌?

[346gnu]

Is that what the stars mean then?

[JonathanHodgson]

My assumption is that the word was s c r e w e d - screwed...

Although I don't seem to have been filtered, so maybe not.  I've seen this sort of thing on other forums with over-active filters though - on one car forum, we had difficulty referring to a rotary internal combustion engine with a three-cornered rotor!

[danderson]

Jonathan,

You are correct as to what the word was when I typed my my original reply. The system changed it after it was posted.

Don

[346gnu]

It won't pick up engineering issues though.

[Tmetcalf]

Jonathan,

I will need to dig deeper into filters as I did not edit your post.

Best,

Toby

[JonathanHodgson]

Might not be an issue... it was Don Anderson's post with the asterisks; mine came through fine.

I may have assumed incorrectly!

[dschenken]

I'll wager that it is a failure to correctly evaluate surface normals in the import geometry and that the solid modeling kernal has a tweak to hide the defect from the user but the analysis software doesn't. Like, all the normals are pointing inward.

It's also possible that there is a difference in hole construction. PTC's cylindrical surfaces have 6 unique edges and are split into two surface patches, but maybe the SW model doesn't.

I'm leaning more to the former as contacting surfaces should have opposing surface normals that point out. Not having that condition would certainly lead to an inability to find a contact.

[346gnu]

looking the wrong way along the hole axis would fit the experience.

Though the following seems inconsistent with the hypothesis:

• The problem persists if I 'model over the top'
• The problem doesn't occur for a pattern of holes at a larger pcd.in the same parts
• All other parts have behaved as expected

[DenisJaunin]

Hello Charles

Attached is a document which may be of interest to you.

Kind regards.

Denis.