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16-Pearl
September 25, 2023
Question

Creo Parametric Community Challenge 2 - Isogrid on a Curved Surface

  • September 25, 2023
  • 17 replies
  • 19698 views

This month’s challenge is based on a modeling problem I’ve seen throughout my decades in aerospace. An isogrid is a repeating rib structure that adds strength with low additional mass. Although it may appear simple, modeling it in CAD can be difficult, especially when you need to place it on a non-planar surface.

 

DaveMartin_0-1695670569665.jpeg

 

Public domain image courtesy of NASA and Wikimedia Commons.

 

Your mission, if you choose to accept it, is as follows:

  • Beginner to intermediate: Model an isogrid on a flat surface.
  • Expert: create an isogrid on a cylindrical, conical, or radome surface. The isogrid can have a size / spacing of your choice and can be placed on the interior or exterior surface. (If placing on the interior, I highly recommend creating a cross section to make it visible.)
  • Optional: add fillets to the interior “vertical” edges.

For this challenge, you can choose to ignore the center circular post and hole as depicted in the pictures. You can focus on the vertical sides of the isogrid triangles. (Of course, you can always challenge yourself by including those circular posts and holes.)

How would you do this in Creo Parametric? Would you use a profile rib, trajectory rib, extruded protrusion, extruded cut, datum curves, surfaces, pattern, toroidal bend, or some other feature? (Most likely, it would be a combination of two or more of these.) The sides of the triangles in the isogrid can either be connected or they can be disjointed (as in the image below).

An optional Creo Parametric 2.0 model has been attached with a radome part model as a starting point if you choose to use it. As creating the isogrid all the way to the tip can be challenging to say the least, a suppressed Solidify feature has been included that removes it.

DaveMartin_1-1695670569675.png

 

Public domain image courtesy of Wikimedia Commons.

 

Please submit a part or zip file of your submission as a reply to this post and indicate which version of Creo Parametric was used to create it. Also, please include an image in your reply to this post. This challenge will close on Friday, November 6th.

DaveMartin_2-1695670569678.jpeg

 

Example of a radome on the nose of an aircraft. Image courtesy of Kentaro Iemoto and Wikimedia Commons shared under CC BY-SA 2.0.

 

Additional examples of isogrids on curved surfaces can be found here and here.

 

Find the PTC Creo Community Challenge Guidelines here!

 

17 replies

tbraxton
22-Sapphire II
22-Sapphire II
September 27, 2023

For the purposes of this exercise, I have a question about the requirements. Assuming pocket milling is used to remove material from a curved part, how must the tool path be managed when cutting the pockets? Is it acceptable to use a surface normal reference at the centroid of each pocket or must the tool trajectory be normal to the curved surface at all points along its path while milling?

 

This is an example of using the surface normal at the centroid of each orange 3 sided pocket on a curved surface. This topology will not be congruent to one where the cutting axis is normal to all points on the curved surface.

 

tbraxton_0-1695831202350.png

 

16-Pearl
September 27, 2023

One of the reasons isogrids are not very common is that they are incredibly expensive to manufacture. For the sake of this challenge, concentrate on the geometry and not the manufacturing method. You do not need to assume this will be manufactured via CNC machining. When evaluating the submissions, I will look at the resulting geometry and what features you chose to use. I will not be taking manufacturability into account.

 

tbraxton
22-Sapphire II
22-Sapphire II
September 28, 2023

Isogrid applied to the interior of a domed shell.

 

tbraxton_1-1695875422487.png

 

 

16-Pearl
September 29, 2023

Wow. Looks fantastic.

 

Can you share your model file with the community?

 

tbraxton
22-Sapphire II
22-Sapphire II
September 30, 2023

Creo 7 model enclosed. Resume all features after opening the file and prepare to wait (1 min 50 sec regeneration time on my 11th gen i9 laptop). Fully regenerated this model zipped exceeds the 47MB file size limit for upload here. I suppressed the patterns to reduce the file size.

 

Notes:

There is a geometry check in the model that is embedded within a trajectory rib internal round. If anyone can offer a fix for that I would like to see it.

 

The patterns are structured to regenerate "quickly".  Quick is relative to other potential construction techniques. It will regenerate faster than if the auto round function were used on the pockets for example. If there are techniques that will regenerate faster than what is in this model, please post them.

 

7-Bedrock
October 2, 2023

I found the exercise harder than it looks!

here my 2 first try.

 

Thx to Dave for this challenge .

 

made with creo 4

 

.Capture d’écran 2023-10-02 090250.jpg

Capture d’écran 2023-10-02 090120.jpg

14-Alexandrite
January 25, 2024

Fiddix, Can you explain how you used copy geom? I'm trying to replicate how you generated the part, but your copy geom window is different when I try to do it. I cannot select the same references that you selected. 

7-Bedrock
March 22, 2024

sorry for my very late answer !

I dont do anything particular:
I just make a box selection of all the geometry and then make a "repeat geometry"

I make you 2 screen shot to illustrate.

 

Sans titre.pngSans titre0.png

13-Aquamarine
October 2, 2023

Hi Dave,

 

Thank for this challenge.

I think there are lot of different ways for this feature creation.

I have used on the way in non-planar, non-cylindrical, non-conical surface.

Please find below image

 

jvadalia2_0-1696253914190.png

 

Part is attached. Give your feedback.

 

13-Aquamarine
October 3, 2023

Hi,

 

Creo 9 has been used to create this part.

 

Regards,

Jignesh.

tbraxton
22-Sapphire II
22-Sapphire II
October 5, 2023

Isogrid applied to exterior of a cone. Design goal is to leverage symmetry to keep regen time down. Creo 7 model.

 

tbraxton_0-1696533977571.png

 

 

5-Regular Member
October 8, 2023

Not realistic, but I have some fun to draw.
I have few opportunity to use the toroidal bend.
Thank you for the challenge.

 

2023-10-08 01_33_43-PTC_BALOON (Actif) - Creo Parametric.jpg
Olivier 

kdirth
21-Topaz I
21-Topaz I
October 9, 2023

Here are my 2 submissions.

 

I started with fairly simple open shape:

iso-tri.png

Then I decided to try the radome supplied by @DaveMartin

radome.png

I would say that my models were created by brute force, repeating the same operation over and over.  However, I did use a lot of patterns and automated the repeated operations with temporary mapkeys.

 

Below is a link to the Creo 7 files.  They are both too big for the 47 MB limit for the community board.

 

CHALLENGE-2

There is always more to learn.
kdirth
21-Topaz I
21-Topaz I
October 11, 2023

The 3D printer was in need of some "exercise" as it had been sitting idle for almost a week, so I printed a scale model about 2.5" tall.

kdirth_0-1697050295601.png

 

There is always more to learn.
15-Moonstone
October 16, 2023

Fun challenge! I did mine in Creo 7 with some Spinal Bends and Multibody. It got a bit thin towards the bottom, which could be fixed, but I couldn't be bothered. 😄

 

Pettersson_0-1697448835945.png

 

3-Newcomer
October 16, 2023

I'm new with Creo but have used SolidWorks for 10+ years. Here's what I came up with. I created the following and the made a pattern from it. Outer ribs are half the thickness of inner ribs so that all ribs are uniform when the pattern is applied. Using Creo 9.0.4.0Challenge how.jpgChallenge results.jpg

3-Newcomer
October 16, 2023

Attaching model here

15-Moonstone
October 17, 2023

I tried a different approach. This time on an easier surface, just somewhat deformed, meaning I could use Flatten Quilt Deformation, which is a really fun tool. My approach this time was to use surfaces as far as possible and only thicken them towards the end. the advantage of this method is that it keeps a constant thickness on the ribs. If you deform the solid geometry, the thickness will vary, but if you deform the quilts and then thicken them, you get a constant thickness, which might be desirable. It was a bit finicky, though, and I had to play around with the accuracy to make Creo do all the thickening. Even so, there's actually a small rib missing, but it's close to an edge, so I don't think it would matter for the strength.

 

Pettersson_0-1697532519001.png

This part is in Creo 9, which is what I happened to have open when I started playing. Apologies to anyone on a lower version!