Issue with patterning features. Missing instances.

[devin.kieselB9RNV]

I want to make evenly spaced alignment markings on this bend. I've made a sketch and extruded the marking into the bend. When I create the pattern two marks are missing as shown below. Any insight on why this is happening or a different way to accomplish this would be appreciated.

The extrusion depth is more than long enough.

Supression is NOT on.

Changing the pattern compute type to Identical or Adjust causes failures.

I've tried the extrude and pattern several different ways to try to find a way that works.

[g-andresen]

Hi,

That is indeed weird.
It doesn't work with the “face” option either.
If you create the profile as a new body and create the pattern from it, it works.
In my opinion, however, this should not be the case.

Perhaps @Phil.E  can say something about this?

günther

[johnsonshiue]

Hi! This is a geometry-specific modeling bug. It has something to do with the tip of the triangular extrusion touching the circular edge. It should have work but. For some reason, the Boolean operation fails in certain pattern instances.

There is a simple workaround to make it work. Just move the circular side face outward a bit so that the tip of the triangular extrusion intersects the circular edge. Then the pattern will work fine. Please take a look at the attached file.

Many thanks!

[g-andresen]

Hi,

I think that the position of the triangular element on the edge is not the cause.
As I wrote above, you also created the extrusion with the “New body” option.
But this also works without the “Push/Pull” action.

günther

[Phil.E]

New bodies do not rely on the intersection of the triangle and face.

Here is evidence the edge/face relationship is problematic. I can't get it to combine bodies. This is a known limitation in the shape manager kernel.

Moving the face shows it's not really a cylinder (except at a zero point on the plane)

All of that said, moving the face down to avoid the complex zero point intersections (edge to plane and triangle to that edge), the modeling kernel still doesn't like the number 72. 

[laughingcreek]

@johnsonshiue - your example is "working" because you changed the extrude type to new body instead of join.  see attached, your model with the extrude type changed.  this also makes the original "work".  it's not desirable to have 72 new bodies added to the model.  i guess the plan would be to combine them back on after? that would make it so the pattern wouldn't be parametric.  also undesirable.

[Phil.E]

I'll send this to the team that works on pattern. There's something interesting here. It doesn't like 72. Change it to 73 or 71 instances and it works correctly.

[g-andresen]

Hi,

Interesting!

A relation to the number sequence full circle > 2 * 360?

günther

[Phil.E]

Yes, same with 36.

[devin.kieselB9RNV]

I forgot about this side project for a bit and the notifications must have been filtered out of my inbox. I ended up making the marks as new bodies, which does work even if it's not desireably, I've tried to combine all the bodies but that operation also fails in the same place depending on how the mark geometry is changed. 

[devin.kieselB9RNV]

Looking forward to any insight they can give here

[TheCADWhisperer]

@devin.kieselB9RNV 

How will this be manufactured in the real world?

I think that I might have an easy solution based on manufacturability.

[devin.kieselB9RNV]

I am going to 3D print these. I'm open to suggestions.

[TheCADWhisperer]

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@devin.kieselB9RNV wrote:

I am going to 3D print these.

OK, I am not familiar with any manufacturing process that can create sharp corners out to 15 decimal places (especially 3D printing), so let me try modeling more like the real world and see if that fails. Back in a few minutes...

Edit: Well, my idea didn't work.

[devin.kieselB9RNV]

Unfortunate. Thanks for trying.