WEEK 7 Computer Controlled Machining


For this week assignment I wanted to produce a chair (as the most of us did here in opendot lab), and I chose to redesign the classic italian "trattoria" chair. This is a very common chair here in Italy, you can find plenty of them in traditional restaurants. Redesigning it for digital production seemed to me an interesting challange.

First I started designing the basic structure using Rhinoceros in 2D. The effort was to use material with minimum waste so the design was made in order have the pieces as close as possible one to each others.

I directly designed T-bone fillets for every joints. I discovered later that for some kind of joint this wasn't efficient. I had to redesign them directly on VCarve Pro. We'll see it later.

When the 2D design was complete I simulated the chair construction to be sure everything fit togather.

I placed every piece close to each other to save material. This was even too close, I had than to add some space between pieces to avoid a too weak structure that could have been a problem in machining.

I made than a render to evaluate better the final shape of the redesigned chair.

I than started the machining on a Shopbot. The first step was to place the 12mm wood panel aligned with XY machine planel.

And to secure it with some screws. I avoided corners that was already too much ruined from previous works and placed screws every 35-40 cm on the perimeter 1 cm far from the borders.

The tool was two bladed with a 6 mm diameter.This was the smaller radius I used in the design of the chair.

I than divided the cutting in 2 phases. The first one to cut out all the material inside hole joints. The second one for external profiles of pieces. In this phase I put more distance between pieces: more or less 4-5 cm.

As I said before I redesigned hole joints in this phase, I used the dog-bone tool in VCarve Pro to loose less material and keep the pieces stronger.

The machining was lunched starting from hole joints just redesigned. If I had these holes cutted later than external profiles it could have been bad since the panel would have vibrate resulting in less precise cuts.

It took 32 minutes to finish all the machining. Now I think that cutting profiles could hve been a little closer, in the midway from the first disposition. Maybe 2.5 - 3 cm between pieces

Little bridges of material was left to keep pieces attached to the panel, avoiding them to move durig the work. These bridges are 5mm thick

I manually positioned them in strategic positions to void vibrations and to reduce them the most.

When everithing was done I detached peces from the panel using a saw and I cleaned them to obtain smooth surfaces.

I built the chiar without screws. Joints were trong enought to keep it all togather.

This is the result I'm pretty satisfied

I added some vinil glue on the coupled structural materials. Legs and backrest.

And finally I waited for the glue to dry up.

Sitting on it could be more confortable. I will modify the cutpath of the 2 elements of the backrest in order to have those closer to the back while seating.

Cut Traces
Machining shopbot files

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