Rib array on a dome-like surface

Hi everyone,

I am a grasshopper newbie. I am trying to model ribs arrayed on an onion dome, trying to make it look like in the attached photo. I know how to achieve the surface in the shape of a dome, however i have no clue how to even tackle the ribs.

I need to be able to control the number ribs, the number of nods (or the cross-overs) and where on the surface they cross over.

Sorry for a clumsy decription (an the dreadful drawing above), as i said I don't reallyknow the grasshopper terminology.

Any tips please?

Thanks

Replies to This Discussion

Permalink Reply by Matt Gaydon on January 27, 2017 at 6:17am

How about this, It will only work on a symmetrical shape mind.

Attachments:

RIBS-ON-RUSSIAN-DOME.gh, 15 KB

Permalink Reply by gosia on January 27, 2017 at 6:59am

Hi Matt,

thanks for your reply!

I have created a curve from points to use as the dome profile.

The lines seem to be not attached to the top, i am not sure why?

Permalink Reply by Matt Gaydon on January 27, 2017 at 7:15am

I think its just you have draw the curve from points the other way up (Your start and end points are opposite to mine) . Click on the points component and select reverse from the drop down list. or just re-select the point starting at the bottom and working your way to the top.

Permalink Reply by gosia on January 27, 2017 at 7:28am

works great, thanks a lot!

Permalink Reply by Birk Binnard on January 27, 2017 at 11:07am

I've made several small parts like that: http://www.thingiverse.com/thing:1319930 but had trouble with the top point. The ribs ended up making a small flat area so I cheated and added a tiny cone to the top.

Permalink Reply by gosia on January 27, 2017 at 11:36am

Hi Birk,

How did you construct these? They look great 3d printed!

Permalink Reply by Birk Binnard on January 27, 2017 at 12:11pm

Thanks gosia, I'm glad you like my designs. For parts like this the process is pretty straightforward (because I am a self-taught GH user), but the actual GH layout get somewhat complex because of the requirements for making a valid 3D printable part. The basics are these:

1. Construct the curve forming the shape of the part (I use 6 points and an interpolated curve.)

2. Use this curve to make a Sweep1 surface

3. Extrude a small square along this same curve to make a make a square-shaped ridge and cap it. (I've tried triangles too.)

4. Make a circular Curve Array of 3 specifying the number of ribs you want. Be sure to use a rail curve that matches the sweep curve in 1.

5. Twist these ribs a specified # degrees, and then twist them the same number of degrees in the opposite direction.

6. Join 1 & 5 and you're done - almost. As I said, the top of the part will be flat, so I add a small circular cone to make it come to a nice point.

For 3D printing I had to give the basic surface thickness so I could control the amount of light transmitted through it, and also to eliminate naked edges, so Step 2 is actually more complicated than I indicated above.

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