Week 15. Mechanical design, Machine design

Goal

This is a group assignment and the goal is to design or modify a machine, making as many of the components as possible and automate the machine. Our extra challenge in Barcelona is that we are not going to buy anything in order to explore the limits of digital fabrication and making all the mechanical parts that were missing.

What we did

We made a modified version of the MTM Snap lock machine with improvements borrowed from the commercial version (Othermill) and some fabricated parts. We keep a page for the machine group page here. Hey, come back later!

What I did

Porting the MTM design to kokopelli

I ported the MTM snap lock design (originally in DXF) to kokopelli. The reason I did so is because our material was not exactly the same thickness as the original design. Apparently not too much, just +0.3 mm, but enough for not fitting and requiring several modifications scattered over the whole design. The main advantage of porting the design to kokopelli is that it became parametric. The most important parameters are: bit diameter, material thickness and bed size. Adjusting these parameters redraws the whole machine instantly. So it is now possible to make a different size MTM snap lock in any material thickness. Once Fab Academy is over I will continue modifying the MTM and probably porting other machines in a github repository.

MTM ported to kokopelli  3D MTM

Designing a timing belt

We started with a laser-cut timing belt in 1 mm polyethylene. I designed the gears that matched the laser-cut belt. The result proved to be unreliable with a huge backslash. Later, since I had a due assignment in molding and casting I  designed a mold for making a urethane belt, as Neil suggested in one of our machine reviews. But even I reinforced the belt with some sewing thread, it still was too elastic and hence not suitable for the machine. Luciano told me in advance that I would fail, but I had to give it a try. Since buying a timing belt was required to continue, hence breaking directive zero, we closed this design fork, returning to the lead screw design.

What I learned

The most important thing that I learned in this assignment is not related to the machine, but related to group management. We failed as a group because we no one took ownership of the project. A few months ago Joe Justice from Wikispeed came to the Iaac and gave us a workshop about extreme manufacturing. It was very interesting and he put emphasis in one particular thing when dealing with group assignments. There must be a Project Owner. He/she is one person who has the clearest vision of what should be the outcome of the project and the whole team relies on the Project Owner to set this vision. I did not understand why till the end of this assignment. I don't know if it is related to the human essence, but democratic decisions were unsuccessful.