As I am now in an apartment, I can't make noise anymore. This box allow me to work/play without neighbor issues. The other big advantage is to contain the dust and the bad smell of machining.
This enclosure reduce the noise by 12db according to my iPhone and the SLALite app which looks not really impressive but in fact is a great improvement. Do not forget that 12db correspond to a factor of 16 of sound amplitude attenuation. Concretely, now my vacuum cleaner is more noisy than my CNC milling machine.
The theory says that a heavy material stop and reflect a sound wave. As I couldn't make a cast iron box I choose wood. But we also need another material to absorb and dissipate the energy and avoiding to make sound box like a guitar. This is the role of the mat layer situated inside. At the end I noticed great improvements by adding polystyrene foam at some strategic places. I think that it avoids the machine vibrations to be transmitted to the box. I also placed the box on foam cubs.
For the Proxxon mf70, the box I made measures 50 (length) x 53 (height) x 41 (depth) cm.
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Step 1: Gluing
I bought a wooden board (300 x 40 x 2), a 4mm plexiglass window and 6 cheap mats. I made the board cut at the good size at the store. I also finally used some polystyrene foam for home insolation I already had.
The parts were cut at the store at 50 x 40 cm. Notice that the bottom is not closed. It is due to the fact that all the parts come from the 300 x 40 x 2 cm lumber. It allows me to make a custom part with holes for the wires and, maybe in the future, a ventilation system.
I simply glued the edges and assembled the parts. As I didn't have large clamps, I just put heavy stuff on it and secured with small lumbers and clamps as shown in the pictures. I did this in two times: At first the sides and top, and after the bottom.
Step 2: Completing the Bottom
The last part was cut at home. The last hole will be closed by a piece of wood in which all the wiring is passing through. It is maintained by hot glue in order to be easily removed.
Step 3: Adding the Mats
The mats where already 40 cm wide so I adjusted them to the inner of the box with a cutter. I then glued one side and apply them in the box.
Step 4: Adding the Window
I cut the window by hand because it tends to melt if done with a circular saw. I then drilled the hinges holes. I used shorten wood screws to attach the window.
It is the same process for the clasp.
Step 5: Adding the Foam
The first test was disappointing, I didn't see much improvement. I took some scrap polystyrene foam an tried several configurations. I understood that the box was vibrating because of conduction when I decoupled the machine from the box by placing it on the foam. According to my iPhone, I also gained few dB with the vertical parts.