Why can't I mirror a feature pattern?

StephenG

I have a situation where I want to mirror a pattern and am dumbfound why this cannot be done. I believe I have a valid scenario that makes logical sense.

Here is a simple sheet metal part that I wish to add "fakeometry"  to reflect gussets that are formed during the bending/forming process.

No problem modeling the gusset feature (3 extrudes and a couple fillets) and doing a linear pattern to create a 2nd gusset along the same edge.
(Anyone know of a feature script that fakes in deformed style gussets?)


But I cannot mirror the pattern feature to the opposite side.

Fortunately, this part geometry was simple enough that I could create the 2nd gusset using a mirror and then mirror the mirror.



While this produced the geometrical result I wanted the method used does not reflect the design intent of the the gussets being separated by a given distance.    
 
I know there are various ways to work around this, but I am annoyed that I have to resort to a modeling flow that appears to be convoluted relative to a straight forward feature-to-feature relationships and modeling process that reflects design/functional intent.   

jon_sorrells

The edge that you used as the direction for the linear pattern no longer exists when the mirror feature happens, so it can't figure out what direction to do the mirrored pattern in.

Changing that to something that doesn't get modified should allow it to work

You can also turn off 'Apply per instance', since the geometry is exactly the same for each one.

EvanReese

I'm not sure offhand in this case, but might be able to figure it out if you could link the document. if you can't share this one, it looks like it may not too much work for you to create a similar part you could share.

For a generic answer in the meantime, in my experience with feature patterning, it usually has something to do with the way you're terminating features ("up to face" might fail on a pattern where "up to next works", for example). Sometimes you may have to select additional features, not just the pattern feature. So instead of just picking the linear pattern, you might also try picking the features that you patterned there too.

MBartlett21

It could be something to do with mirror not having an 'apply per instance' option...

StephenG

I doubt the issue has anything to do with how the gusset feature was built: 1 symmetric blind extrude add to create convex gusset bulge, 1 extrude remove through all to create the concave crease, 1 extrude remove to trim extraneous material and 2 fillets to smooth the gusset transition into the bracket.

Note: The parent features (5 features) and the linear pattern feature were included in the attempted mirror feature.

Here is the link to the document...
https://cad.onshape.com/documents/18b806f5c112daddce4b0633/w/d11eb1c62350a56ca16a422c/e/34af4bd2aafd70af1aaf326f

steve_shubin

@StephenG

Is this what you’re looking for

https://cad.onshape.com/documents/05ea10cfa9a759aa5d8fef97/w/489223b100f1a77917a71ab1/e/cf52346cb0f4b951a9ae256b

StephenG

@steve_shubin
No. In my original post you should have seen I desired to have a total of 4 gussets. 

The 1st gusset is located from a back edge, the 2nd is located along an edge separated by a fixed distance (linear patterned), the 3rd and 4th gussets are "mirrored" to the other side.

Again, it is not a matter of NOT being able to create something that "looks and measures" correctly, but having to use a modeling technique that is contrary to my design intent. I should be able to feature mirror a linear pattern feature. 

jon_sorrells

The edge that you used as the direction for the linear pattern no longer exists when the mirror feature happens, so it can't figure out what direction to do the mirrored pattern in.

Changing that to something that doesn't get modified should allow it to work

You can also turn off 'Apply per instance', since the geometry is exactly the same for each one.

StephenG

@jon_sorrells
Your are a brilliant guy! 

My first attempt was to use an edge on the opposite side, but this did not work. I ended up using an edge that was not affected in any way by the linear feature pattern or subsequent mirror.

You must know something about the internals (deep magic) of OS. I am surprised  OS did not handle this scenario cleanly. Yes, the edge that was selected for the pattern direction is "changed" by the linear feature pattern, but it has been my experience in other CAD products that this does not result in the edge being "destroyed". Yes, the selected edge is modified (shortened) and a new edge comes into existence. The result is the reference to the original edge is still valid for establishing the direction for the mirror of the linear feature pattern. OS developers need to rethink how this works to improve modeling robustness.

Note: Checking the "Apply per instance" was just a shot in the dark per suggestion in a prior comment.