Designing a dome optimized to be built from recycled plastic

[Sam Smith]

I'm working with the clean up team at standing rock, and I've built a plastic waste shredder and an extruder (check out preciousplastic.com for more on these machines). I'm now able to grind plastic waste and melt it into new shapes. I'm looking for help designing a dome structure optimized to be made of parts that are easy to produce using simple plastic fabrication, using either compression molding or injection molding. To optimize the design, it would use as few simple unique shapes as possible. I don't have the modeling skills to do this, but I'm wondering if anyone would be willing to lend a hand on this project. I have access to a 24"x12" CNC mill for making injection molds, and water jet cutting for making compression molds. If I can find a properly optimized design, I can turn trash directly into dome parts!

[Dick Fischbeck]

you could make corrugated sheets or conical overlapping elements. all elements identical. any size dome. too-good-to-be-true.

http://randomeshelter.blogspot.com/search?updated-max=2012-02-08T18:56:00-05:00

[Paul Kranz]

Sam:

How big of a dome are we talking about?

I designed a fiberglass geodesic dome dog house that was made from fiberglass lay-up many moons ago which has injection-molding potential. It was light enough to lift with one hand, strong enough to stand on (200 lbs) and big enough for me (6'1") to crawl entirely inside of. It was based upon the icosahedron turned edge up and had triangles that were only 18 inches long although the dome part was manufactured in one piece. Vyom Akhil liked it anyway! I called it the "DoggiDome." See attached.

Paul sends...

On Fri, Jan 13, 2017 at 6:13 PM, Sam Smith <notsa...@gmail.com> wrote:

I'm working with the clean up team at standing rock, and I've built a plastic waste shredder and an extruder (check out preciousplastic.com for more on these machines). I'm now able to grind plastic waste and melt it into new shapes. I'm looking for help designing a dome structure optimized to be made of parts that are easy to produce using simple plastic fabrication, using either compression molding or injection molding. To optimize the design, it would use as few simple unique shapes as possible. I don't have the modeling skills to do this, but I'm wondering if anyone would be willing to lend a hand on this project. I have access to a 24"x12" CNC mill for making injection molds, and water jet cutting for making compression molds. If I can find a properly optimized design, I can turn trash directly into dome parts!

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Very high regards,

 

Paul sends...

ReviveTheFlame.com

[Sam Smith]

Hey Robert, that's super cool! Have you seen the archimedes designs hubs? Very similar, even strut length and connectors based on the Goldberg poyhedron. But your design looks better for injection molding, theirs are cast aluminum (and quite spendy). 

Can you send me a digital design file for your connector? I could probably make a mold of it on my friends 3-axis aluminum mill.

After reviewing what's available, I actually decided I'm going to try building your CNC 4V dome out of compression molded plastic parts. My idea is to get the molds CNC laser cut in aluminum, put the recycled plastic flakes in, heat up the aluminum, and then compress them into the flat mold. I could potentially do it using simple injection molding too. I'll have to do some experiments.

 after doing a bit more research, I settled on your 4V dome as the easiest one to build that I could find. 

On Friday, January 13, 2017 at 10:46:37 PM UTC-8, Robert Clark wrote:

Awhile back, I had an idea for a light weight dome structure using injection molded hubs.  The shape is based on a Goldberg polyhedron made of hexagons and pentagons.  This model would have just 2 unique plastic hub parts.  The poles would be straight and made either of pvc or metal conduit tubing.  All poles are the same length.  I never really finished the design.  Just conceptual.

[Sam Smith]

Cool! I'm looking for something that could at the very least be used as a sleeping shelter for a few people, about 12' diameter.

On Friday, January 13, 2017 at 3:54:31 PM UTC-8, Paul Kranz wrote:

Sam:

How big of a dome are we talking about?

I designed a fiberglass geodesic dome dog house that was made from fiberglass lay-up many moons ago which has injection-molding potential. It was light enough to lift with one hand, strong enough to stand on (200 lbs) and big enough for me (6'1") to crawl entirely inside of. It was based upon the icosahedron turned edge up and had triangles that were only 18 inches long although the dome part was manufactured in one piece. Vyom Akhil liked it anyway! I called it the "DoggiDome." See attached.

Paul sends...

On Fri, Jan 13, 2017 at 6:13 PM, Sam Smith <notsa...@gmail.com> wrote:

I'm working with the clean up team at standing rock, and I've built a plastic waste shredder and an extruder (check out preciousplastic.com for more on these machines). I'm now able to grind plastic waste and melt it into new shapes. I'm looking for help designing a dome structure optimized to be made of parts that are easy to produce using simple plastic fabrication, using either compression molding or injection molding. To optimize the design, it would use as few simple unique shapes as possible. I don't have the modeling skills to do this, but I'm wondering if anyone would be willing to lend a hand on this project. I have access to a 24"x12" CNC mill for making injection molds, and water jet cutting for making compression molds. If I can find a properly optimized design, I can turn trash directly into dome parts!

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[Sam Smith]

Whoa, that's interesting. Thats made out of shallow cones made out of sheet material?

[Sam Smith]

Thanks Robert! Would you mind attaching your 3D model file for the two connector types? If you're willing to send me the CAD file, I can see if my friend can mill me a die for it out of aluminum with his CNC milling machine.

On Tuesday, January 17, 2017 at 6:13:26 PM UTC-8, Robert Clark wrote:

Sam,

After I had been playing around with the design, I searched around for similar designs and found the Archimedes dome.  However, Archimedes is based on the simple soccer ball pattern and the steel connectors are expensive.  My design uses a higher frequency geometry and thus shorter struts but more connectors.  Also, I would ideally go with zinc die cast connectors instead of steel.  A mold in china costs about $2000 and the connectors would be about 50 cents each.

A 12 foot diameter dome would require 85 two-foot long tube struts.  The tubes would be made from 1 inch nominal pvc or metal emt which has a 1.049 inside diameter.  The 85 tubes could all be gathered into a bundle just 9 or 10 inches in diameter for carrying.  The 60 connectors would fit in a small 3 gallon plastic bucket.

[Ashok Mathur]

Dear San,

This is a newbie question so please do not take offense.

In the type of domes that we are discussing, the total connectors (may be of two or three types) will not exceed hundred in number.

Why are you wanting to make a die when the same cnc machine could easily make the 100 pieces ?

Is it the time involved in machining the 100 pieces, or is it that molded parts are very much cheaper?

Regards

Ashok

Regards

Ashok

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