Many thanks to Jamie Hill for providing inspiration for this challenge and the next. We had a brainstorming session yesterday, working on a custom method to solve a customer-specific problem.

One of the challenges was identifying the center of a flatten cut-out in a sheet-metal rolled cylinder. The main problem is that the faces of the hole change, depending on its position on the cylinder.

We found a pretty good solution and were very proud of it. But now, we ask for our "humbling" pill. We know that you will find much more interesting solutions. Can't wait to be surprised!

**Rules:**

1. Watch this video. It is also attached to this post, for those of you without access to YouTube.

2. Download the attached part. If you use SOLIDWORKS 2016 or older, you can model the part yourself, using the instructions in the video.

3. Switch to the *Flat Pattern* configuration

4. Create a new configuration called *Mid Ribs*

5. All new features to be added after the Flat-Pattern feature, in the flat

6. Add 2 ribs centered on the cut-out.

7. Make the rib width = to the Custom Property *TabW*, which already exist in the file

8. Test how well the ribs update if the hole is moved anywhere on the cylinder. The only exception is the hole touching the top or bottom base of the cylinder.

9. Once you got a robust model, create a new configuration called *Vent*

10. Multiply the ribs to fill the cut-out. The gab between two ribs is equal to the width of the rib.

11. Repeat step 8.

12. Upload your finished file to this thread before

12. Provide your solutions before midnight EDT on April 7th, 2019.

In my solution, I did not use macros. **If you use macros, and they are really good, we might award a special prize for them.**

**For eternal glory and 10,000 points, come with the best, most elegant and original solution which allows the mid ribs and the vent to rebuild fast in all positions of the flatten cut-out. The more details you add in your explanations, the bigger your chances of winning.**

Videos describing your solution are welcome. Please record your voice too, as you explain the steps you took.

Good luck!!!

**Update 2019.Mar.25: A second 10,000 point award is offered for the best solution solving the problem without referring the sketch of the circle used for cutting the hole.**

I will start by thanking John Stoltzfus for his generous donation of points in support of the SWPUC!As most of you know by now, the ideas for these challenges come from real-life problems encountered by my customers. Even though, in general, I find solutions acceptable for the customer, I am always wondering if there are better alternatives.

Being able to challenge the best SOLIDWORKS users in the world in finding other solutions has been a privilege. Thank you!

The 25th SWPUC challenge was not different in this regard. Initially I was quite proud of the solution I found, which could be applied to almost any type of geometry.

One thing I did not consider was the fact that the part included in the challenge is cylindrical, which greatly simplifies the problem.

It should not have been a surprise that the participants quickly identified several solutions which took advantage of the entities in the cut-out sketch, which greatly simplified the problem. The simplest solution is usually the most elegant one. So thank you again, for showing me that! It is a strange experience, both humbling and satisfying.

Let's discuss some of the solutions.

Chris England submitted the first entry. He tried to find a universal solution, independent of the cut-out sketch. For that he filled the flatten cut-out and placed a reference point in the centroid of the new face. Unfortunately, for irregular shaped faces, the centroid does not determine the center of symmetry in the horizontal direction.

Vahid Mostofi provided the second entry. He was the first to refer the circle's center in the original cut-out. That determined the vertical position. Great thinking, Vahid!!!

In order to pin-point the horizontal position, he used a mid-point relation to one of the edges of the main horizontal rib.

Unfortunately, the edge does not represent the center of the rib. In the picture above, the mid-point of the symmetry line of the rib is a bit to the right, compared to the mid-point of the edge.

Heiko Sohnholz's first entry also took advantage of the circle's center of the cut-out sketch. So, the vertical position was determined.

He also created a fill surface for the flatten hole. The beauty of his solution was trimming the new face with a plane that passes through the center of the circle. Thus, Heiko created an edge located in the middle of the cut-out. Its mid-point is the center of the flatten cut-out.

Alex Burnett proposed a solution that is independent of the circle's center of the cut-out. He added a very interesting twist for ensuring that the model will always rebuild properly. By subtracting from a solid body representing the bounding box of the part, the flatten sheet with the hole, he obtained the negative of the hole. This is a very robust method!!!

To identify the center, he used the same reference point as Chris. Fortunately, the flatten cut-out is vertically symmetrical, thus Alex's solution was correct.

In the future, I will try to find an example that would generate a cut-out without any symmetry. Using the reference point (center of face) would not work for something like that.

H.E.W. Rob Edwards had a lot of fun, working on his solution. The creation of the rings was quite something!

Because in this specific solution he used the center of the face, the location would not be precise in a asymmetrical cut-out.

Rob mentioned using Face Curves in a un-submitted solution, which would provide a correct (universal) answer.

Henk De Bruijn also use a reference point (center of face) for locating the mid ribs.

Is time to announce the winners of the 25th SWPUC!10,000 points: Heiko Sohnholz for the simplest solution10,000 points: Alex Burnett for the best solution that does not refer the original sketch.Also congratulations to the rest of the participants for demonstrating originality and ingenuity!