Steve Mould’s latest video https://www.youtube.com/watch?v=vrOjy-v5JgQ is on bistable auxetic material, where he has a somewhat flexible material with slots cut into it such that the initially flat form will deform into a three-dimensional surface that is locally stable. He has examples of domes and various cylindrical tubes. He has some very interesting analysis of the strategy for making the cuts to match the required surface.
This reeks of Grasshopper! I wonder if anyone has done anything along these lines and would be prepared to post an illustration or model? I am really tempted to have a go.
The history of the use of Grasshopper in auxetics work goes back more than 10 years.
This blog post from 2012 was what lead to my collaboration with Mark Pauly and Keenan Crane that resulted in this 2016 paper https://dl.acm.org/doi/10.1145/2897824.2925944
(full paper available here)
@bob.h.mackay, @Steve_Mould Did you manage to successfully output your own geometries into bistable cutting files?
I am trying to get this working for a university project and would really appreciate any advice!
How did you prep your input files? Did you manage to download the suggested boundary first flattening application or did you use the grasshopper bbf component in the ngon pluggin.
Did you have any issues with the 'BASS generation' python block at the very end of the 'demo-tri-bistable' programme? For the example files, everything else is working but I am getting errors from that final block which generates the cutting pattern.
I’m afraid I did not take this very far. I have a reasonably large CNC milling machine, but with the restriction to wood or perhaps aluminium, I don’t think I would get the necessary flexibility for this to work. In the longer term I am looking for a way to create minimal surfaces, such as the gyroid, but other projects have intervened.
The design files work for me, but the GH script which allows one to visualize the auxetic mesh through the deployment stages (generation_aux_bass) is very broken (see attached screenshots). This is the error message I get from the BASS generation ghphythonscript:
“1. Solution exception:‘NoneType’ object is not subscriptable”
I realise the script has a few errors. Firstly, the variable DBPath is spelled ‘DBPath’ on assignment and is referenced as ‘DBpath’ (lowercase p). Furthermore, the NoneType issue your experiencing is from the function RayRayIntersection, which checks for an intersection between two points (I assume) and returns None if there is no intersection. The script actually checks for this once, and then scales the elements by a variable ‘bigNum’ which is set to 100. If you increase BigNum to say … 500, 1000, or 2500 and so on, the error should eventually disappear.
