Workshop: Extreme Detail – Part 2

The school has a large 5-axis CNC machine that we used to cut out the pieces of the lighting object. The process actually took longer than expected due to the large number of binding holes. Average cut time was probably around 45 minutes – 1 hour per sheet. In the first pass, the CNC drilled the binding holes.

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In the second pass, the CNC drilled out the contours that were on each quad. The actual edges of the quads were done as the last step. This is important to note, since once the quads are cut free of the plywood sheet they are free to move around on the cutting table, which would make any precision drilling on it impossible.
We also had an incident occur where a stray piece that was cut out from the contours was thrown up on the sheet to lay on top of it. The drill head happened to come down right overtop of this piece. Upon contact the piece shattered and the CNC machine halted! We had to reset the machine to continue.
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The cut pieces required thorough hand-sanding in order to remove the rough edges that formed. The next step was assembling the structure using string to bind it. We attached rice paper to the insides of the quads in order to diffuse the interior light. As a final detail, we ran some LED strip lights inside the lighting object. Check out the time-lapse video to see how we assembled it:

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Conclusions: The workshop gave students a chance to use the school’s CNC machine to bring a computer-generated form into physical space. We accomplished this in the short time frame of only five days, with a few sacrifices: the tight timeline meant that we could not test out our ideas, so we didn’t actually know how the final design would hold up in terms of assembly and fit.

The design process partially suffered from the inability to fully automate some processes of the parametric design. The patterns team provided us with the concentric lines to cut the contours all flattened on the z-axis, so we had to manually move each set of rings down 2mm each so that the contours would be cut correctly. We had to move our binding holes inward on each quad once we realized during a simulated cutting that they were too close to the edges.

Alphacam was mentioned a few times by one of the workshop instructors as a “terrible” piece of software to handle CNC milling. There were many occasions where only the instructors knew the right settings needed. I am confident that I could not cut anything on my own, despite the CNC machine being free for all students to use.

It was very difficult to find the right combination of settings in our Grasshopper sketch that would produce truly planar quads for cutting. There was a tolerance issue of +/- 1mm all around, which greatly affected the edges of the quads. Instead of being made from a single planar edge, most of them had a bit of “warp,” associated with the edge being made from a double curve. It seems that there should be a better way to ensure that the final form is planar.

The binding holes turned out to be very snug, and in some cases the string wouldn’t fit through without the hole needing widening with a tool. In retrospect, we should have made larger holes. The binding process as we designed it was very time-consuming during assembly. A different assembly technique would have benefited the project.

The lighting object that our team produced was an excellent example of what you can produce on a CNC machine with a week of work. Further experimentation with the machine would result in projects with a higher degree of craft, and it would be worthwhile to experiment with other materials as the plywood had a tendency to splinter on the edges where the wood grain ran perpendicular to the cutting direction.

I’m not sure if I will use the school’s CNC machine in my own work yet, but it now appears a lot more accessible than it was before.

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