Matters of Tension and Compression within Geometries
Issues of tension and compression seems to be thematically recurring in the process of developing these printed textiles works. Above is an ABS 3d printed model created with the plain weave script from the PointCrowd RhinoPython workshop run by Ari Kardassis and Masoud Akbarzadeh in January 2011. Many of the tension and compression issues stem from the phenomena of what I call getting gauge. It is that trial and error part of getting the right tension on a knit textile for example to meet the size requirement for a sweater or blanket etc. Geometrically for this diameter pipe or yarn, this is about the maximum distance the outer boundary can stretch from this specific original sphere before the piped surface starts to twist along the spine of the curve and warp the circular section of the pipe. This behavior makes for zero sectional thickness in the 3d digital model, and cannot be printed. This first experiment had a very simple version of piping that is computationally much lighter. This pipe script works, up to a limit. In this version of this model, the piping or yarn does not intersect at the weave crossings on this model, but the geometry of the sphere holds the separate woven strands together.
Compression of Single Link Textile
The single link scripted model above was printed as a flat, rectangular model, as you can see with no boundary return along the open ends of the strand, permitting this model a way to slide diagonally in the xy plane to have different states of density. Each of the strands is also free to rotate in the z direction allowing for some curvature parallel to the direction of the strand.
This is a model of interloping or knitting and presented the most issues with the pipe or yarn torquing into nothing, it required a new pipe script to get it to print at all. The section on this model is true and circular. The script is computationally much more demanding in terms of what it needs to track, but you get good results in the section of the yarn. It is posted here, thanks to Skylar Tibbets for help with solving the twisted pipe. This was made with some intersections in the yarn, but geometrically will hold together just fine if the yarn does not self intersect. The “ApplyCurvePipe” command in Rhino yields beautiful pipe results, especially for the knit curves and I have an update from Pascal Golay at McNeel. You can use “ExtractPipedCurve” to get a nice meshed curve from CurvePipe object that can be exported to an stl file.
Having made these physical models, I think the most useful model is the script, that can be used repeatedly to look at many different kinds of things both physically and digitally. These textile samples are neither surfaces nor bones and can reside somewhere in between, because you can push the script to be either/or if you so wish. These qualities have meant that it has been possible to look at these models as outer perimeters or skin and as structure. This kind of model does not require one kind of outer boundary or shape but is made up of many interrelationships of parts that can then be formed for multiple purposes.
Experiments to continue…
Thank you to Chris Dewart and Seth Hall at RPL for use of the ABS printer.