The assignment

The assignment for this week was to decide a piece that would be repetitive in our project and design a mold to produce it many times. As I am doing an engine that has many gears that wil repeat, I decided that the first modl that I would do was actually the gear, as I did not want to 3D print this piece many times.

The first step of the assignment was actually to redesign the gear. The first gear that I did was very big and my project now needs a smaller gear so the louvers do not get too large.

I designed the gears with a proper engines modeller, which will give the exact size and dents needed for the perfect working of the engine.

After the design I 3D printed the piece to make sure that the engine was working as desired and after I experimented that the engine was working correctly I decided to start the molding.

Molding - CNC cutting

The first step of the assignment is to design the mold that we are going to cut out from the wax block with the CNC machine. I was sharing the block with my colleague so we tried to fit our two pieces in a single block. My piece to mold is quite small so we think that there will be no problem with that. Some considerations of the design of the inverse mold shold be done, as the tolerances so the mold does not break and add some flanges to the design for the better extract of the mold.

After the design of the modl in Rhino, the next step is to cut it out with the CNC machine. The design needs to be done according to the mill that we are going to use in the CNC machine.

We need to design the surfaces that will cut out in different heights so the machine does not mix them and cut anything important in its way.

Molding - Silicone molding

The next step was to start filling the inverse mold that we have created in the CNC machine. We had some problems with the first attempt with some misunderstanding of the instructions of mixing the silicone and the hardening component and the final mold did not finish as expected, so we had to clean it and redo it again.

Th next attempt went very good, and I followed the following steps:

- Mix the components with the proportions that our product needs, in my case 5% of hardening component of the silicone.

- Clean and apply some vaseline to the inverse mold that has been cut out from the CNC machine.

- When we want to tip out the product into the inverse mold, we should start doing it from the corners, as the product will flow from the bottom to the top of the mold.

- When we are done with that, we should hit some times to the wax block in order to extract all the air on it. All those air bubbles will make a less precise mold and so the pieces will be less precise.

Once we have finished the mold, we have to wait 24 hours to so the silicone hardens and finishes the reaction to complete the mold.

Casting

The final step of the assignment is to extract the mold that we have made of silicone and to clean ir as much as possible.

When we have done that, we can make the mix of the two different products of the resine, and start filling the mold. The piece will harden much more faster than the silicone.

As the silicone is very soft and malleable, the piece will be extracted vere easily from the mold. Once we have done one piece, the mold will serve us to repeat the piece as many times as we want.

As we had some problems with the modling, I could not finish the casting of the piece. I will try to solve the problems and update my site as soon as possible.

The day after we could finish the assignment doing the measurements correctly. I could finish the mold with the silicone and after that I could do the casting with the resine product. It was very easy once the mold was finished correctly.

I did many pieces of my gear but I saved some product to build my louvers with the same technique. I will update the website with this information inthe following weeks.