How to make Something BIG

The main objective for this week was the construction of something big. First I thought about what is actually a big thing. If It has to be an entity really big, the question is how much big it should be. In the other hand something really big usually is built by adittion of many smaller pieces that could contruct a bigger one. Repeating a modular pattern you can build something really big. Structures and architectonic constructions are materialized by addition of basic modules from simple bricks to sophisticated entities.

In this way I have raised the problem using an additional method. Related with my final project, I think that can be introduced the modularity question. So I have taken avantage from this week assignment in order to find a supporting structure for my foldable "thing" I decided to work with a single square frame because it will be easier to fix into it the push-pull mechanism, almost I suppose it by now. From the geometrical point of view this decision may limit the number of posible solutions almost if we are thinking on the posibiliy to build some kind of spacial structure. For the time being, I am going to try with polyhedrical shapes. There is only one Plathonic polyhedron which has square faces but if we focus on Archimedean ones, a bigger group can be found. I decided to star with the simpliest of them all, the cuboctahedron.

Although I have built many things using CNC machine they are not enough, you always find problems using this kind of tools. I think that you should have an appropriate design plenty of well solved details besides you have to find the correct milling tip and not only, you must select the correct material. At this point, this can be the key for your success milling any kind of stuff overall if you are using wood either a block of wood or plywood.

Special issues to have in mind:

Milling tips.the quality of the tip will be essential in the finished work. You can save many time if you chose the appropriate end mill for your material. In this case I have used a straight edge mill, I have had fulfilling results with this kind of tips milling plywood. I have used a 3 mm diameter tip in order to get a sharp enough radioused corners of the pieces and overall inside the througholes.

Material. The humidity of the wood should be low enough, in order to get a correct finishing along the edges of the cutting work. I have used a board that has been stored in an almost exterior room. Here in Donostia the humidity level ususally is very high. So the edges tends to produce splinters. If you store the board in an inner space, even if you can put them near the machine, the humidity level of the board will be lower and the cutting work will be smooth.

Tolerances.At this point the considerated values should be higher than those used with the laser cutting machine. I have used a 9 mm thick birch plywood and the pieces are small enough. In order to mill a single edge-lap joint I calculated the tolerance by a 1/10 of the milling tip diameter, so the width of the inside openning should be 0.3 mm bigger than the plywood thickness.

Panelization of the cuboctaedron using square panels.

Cut 2D by Vectrix used for this work.

Straight edge flutes.

Mechanical fixing of the board over the sacrifice layer.

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