Introduction: MAT 594X_Stackable and Nested Objects W/ Grasshopper

Using affine transformations, the project assignment is to parametrically model stackable or nesting objects, which ultimately needs to be printed and tested.

I am working on a simple pendant lighting fixture design. It will have a pattern for the light to go through and create playful shades.

Inspired by Echinus Esculentus, AKA sea urchin.


Rhino and Grasshopper


Step 1: Preliminary Result With Stacking

I might need to change the geometry of this lighting fixture so it can stack better. With that, I will also try nesting it.

This geometry itself is designed purely in grasshopper with no RS (rhinoscript). I created a series of polygons with the same number of segments and the same origin point on X & Y.

Z coordinate varies. Then, I lofted it, converted it into mesh. I triangulated this mesh and used a series of components from Weaverbird (wb) library: wbFrame, wbMeshThicken, and wbCatmullClarke subdivision smoothening.

There does not seem to be naked edges, but there are some problems with the geometry. See the detail picture on the upper edge. I first thought that this is due to the wbCatmullClarke smoothening algorithm, but I noticed that there is a subtle crease there before applying that algorithm. The crease is present as soon as I loft the polygons.

Sliced a mini and patern-free version (7cm in diameter) of this. What is interesting is that, if I place this in the same orientation as the rendering, the print time is 17 hours, however if rotate it one pi, the print time is around 8.5 hours. I am guessing that the discrepancy is due to the differences in support structure that needs to be built.


Doe that mean lofting polygons from parallel planes is not a reliable way to generate geometry for print? What are the reliable ways? Are there certain surface, solid, or brep creation algorithms that land themselves better for printing purposes?


My new theory about the crease I mentioned earlier is that if I increase the segment number of the polygons that make up the geometry, it could help smooth out that crease. Will try that later today.

Step 2: Nesting and Embracing the Segmented Polygon

Ok, in addressing the crease problem that I had mention before, my theory was to increase the segment parameter of the polygon component. After all, the smoothest shape of all -a circle- is about having infinite segments. The problem was, I could not have infinite segments and I could not use circle, instead of a polygon.(Somehow the loft operation does not work the same)

So, I increased the segment up to 100. The crease was still there. (see the red geometry on the screenshot take from Rhino).

Then, I decided to embrace the "polygon"'s true nature and I decreased the segments for a deliberate polygonal look. In this version the polygons are octagons. It worked quite nicely, I think, but, it will still take forever to print.

Sliced a mini version (7cm in diameter) of this (for LED maybe?). The print time is around 7 hours with a support structure.

Oops, I realized that the shape has deformed with the scaled iterations. My guess is that the reference point for the scale transformation does not match the center point of the geometry. I'll fix this in the next step!

Step 3: Why! Circle Indeed!!!

I a not sure why I assumed that the circles could not be lofted into a similar geometry. Just replaced polygons with circles and lofted, et voila! Completely smooth.

Sliced a mini version (7cm in diameter) of this (for LED maybe?). The print time is around 7 hours.

Step 4: 1st Attempt at Printing W/ Creality Ender 3

First trial: not quite success. Several problems

1. The support structure is so dense that it is impossible to peel away. This is a matter of slicer settings. I need to find the maximum stability with minimum material in support structure.

2. The bigger problem is that it got stuck on the bed. I used brim and the structure was extremely dense. There was no way it was coming off, so I heated the bed, 50, 60, 70, and finally at 80 degrees Celsius, it started loosening (but also deforming). Even in this temperature I had to use the spatula really hard for it to come off. As a result, I dented the bed. (See the photo). This may effect my future prints, so I will look into ordering this part as an extra.