Repeated reference pattern issue

[rory_hawkins]

I'm having an issue with performing repeated patterns on a quilt.  Unfortunately I can't share much due to confidentiality so will have to do my best to describe.

I'm starting with a 'base/origin' quilt on which I perform a number of patterned merges.  Usually I model another quilt which is to be merged, copy that quilt, pattern the copy, merge the first copy with the base quilt (ensuring the base quilt is selected first), select that merge feature and select pattern which would automatically detect the previous pattern and do a reference pattern of the merge.

However on this particular model this works once but when I try and do it a second time, the pattern feature button is either greyed out or the pattern instances are overlaid in a single point (seems to vary when I've fiddled around to get around the problem). If I create a copy of the base/original quilt and merge with this instead, the second reference pattern works fine (as do subsequent patterns but a copy of the base/original quilt is required each time) but there are fairly major disadvantages to not being able to carry a single quilt/feature reference through the design process.

From what I've managed to find by googling there seems to historically have been some issues/bugs with reference patterning. My general understanding is Creo sometimes struggles with which previous pattern to reference if there are multiples.
Is anyone able to clarify this for me? Is there a reliable way of making it clear/isolating which pattern is to be referenced? Any help would be greatly appreciated.

[tbraxton]

While your verbal description is readable, it is difficult to root cause the problem without a sample data set for evaluation. Can you create a simplified set of model(s) that demonstrate the problem and post them?

Are geometry patterns possibly the right tool to implement what you are trying to do? That is something to explore. The other issue that may be relevant here is that when you merge quilts the internal feature IDs may be getting updated and that can cause reference problems. Does your base quilt have multiple patches within it? You should be able to use the global reference viewer to gain insight into the references before and after your attempt to pattern to see what is happening.

[rory_hawkins]

The attached is analogous to my part.  For some reason I can't do a reference pattern on the last merge feature (F24).  Nothing terribly complicated.  Can't understand why.  Thanks for your help.

[tbraxton]

If you are not aware of how Creo splits circles in half and the ramifications of this, I would encourage you to research this. It will cause problems on parts with cylindrical geometry and since you are modeling surfaces in the example the cylinder split can cause reference problems with features that cross over the split or straddle the split.

Your feature #17 straddles the split of the cylinder in your posted model. I suspect this is probably the issue but I am not positive.

I do not have a specific root cause for why you can not create the reference pattern as you wish. It would take a while for me to dig through the references so I just modified the model to get the desired pattern members generated and then created a reference pattern after that on the opposite side of the cylinder to show it can be made more robust with geometry patterns.

Do not take the use of the last axis pattern as best practice for an axis pattern, I added it to demonstrate you can create a reference pattern from the opposite cuts.

Creo 7 model enclosed for reference. Note the structure in the model tree and the use of a group as the pattern leader for your horizontal cuts in the cylinder. If this approach does not enable you to create the pattern you need, I will need some more information.

[rory_hawkins]

Really appreciate you looking into this for me.  Unfortunately I'm only running Creo 4.0 so can't open the file you shared (even with GCRI) - shame as would have been interested to look at it.

I'll have a read up about the circle splitting thing and see if that explains the issue.

[tbraxton]

Here is a Creo 4 version of the model.

[rory_hawkins]

Thanks - that is very kind.

I spent some more time experimenting with my original model.  What I've noticed is that if I suppress the first pattern feature (vertical slots) then there is no problem doing a reference pattern of the horizontal features.  This suggests to me that it isn't to do with those features being on the cylindrical surface split (otherwise it would still be a problem regardless of the first pattern feature) and is something to do with multiple patterns.

[tbraxton]

When creating patterns that involve a merge of quilts it is generally a good idea to create a group that includes all of the features required for the merge to regenerate to create the leader and then pattern the group.

There are documented issues with reference patterns. This is one example using axial patterns. Note that this workaround also involves suppressing an earlier reference pattern.

https://support.ptc.com/apps/case_logger_viewer/auth/ssl/case=15353652 

Another option to try is to use datums (points etc.)  patterned as the lead for the subsequent ref pattern locations needed in the model. This will sometimes make it more robust.

Geometry patterns are a possible workaround for these issues as well.

[tbraxton]

In case the link to the article was not obvious from the case posted above. This is relevant to your model and attempted patterns including merge features of surfaces. It presents geometry pattern as a resolution as I had suggested above.

https://www.ptc.com/en/support/article/CS274749?&posno=4&q=Reference%20pattern%20for%20a%20new%20merge%20surface%20feature%20fails&source=search