16. Wildcard week¶
Week assignment
- I have to design and produce something with a digital fabrication process (incorporating computer-aided design and manufacturing) not covered in another assignment.
Vacuum Forming Machine to make packaging¶
I wanted to use this week to create the packaging for my project. So, I decided to use the vacumm forming process. As the object I’m developing for my project is small, Edu Suggested me to partner with Carla how was also interested in trying the vacuum forming machine. We discussed about the fastest way of doing it and ended up deciding to 3D print the molds.
We documented the steps as the machine it’s preatty easy to use but it has it’s tricks.
- The design
I created a very simple design simply to test the thermoforming process with the machine that we had available in the lab. The idea was to try to test a possible packaging. I made my design in Rhino. I have made this piece by joining two circles and an ellipsis. Thus creating a polyline that I then extruded with an angle of 2 degrees in case the part had problems for demoulding.
I did not do any other operation on this piece because the objective was to test the process.
- Making the model
We decided to 3D print our models and just place them on the bed of the machine. As our pieces were simple and small it was not necessary to duble check design issues. The most important thing is to make sure it’s possible to demold and that has no nooks and crannies.
- Framing the material
The fist step is to get the material into the frame. In order to do this, we need to trap the material into 2 rectangular metal frames. We ended up using strews and big washers to hold both frames toghether. We didn’t look for the most suitable material for this process, we just use a Polypropylene sheet that we found in the lab. Not the best idea. We cut the edges that protrude from the frame to be able to make the sandwich: frame / material / frame.
- The machine
We needed to turn on the machine, which has 2 has two plugs and an inlet for the vacuum cleaner. The machine has resistors in the upper part, which heat the material. It also has a series of magnets that hold the metal frame to keep it close to heat. Then, the bed has some holes, which when connecting the vacuum cleaner, make a vacuum.
The process involves heating the sheet of plastic material until it is soft enough and then turning on the vacuum cleaner and lowering the sheet in a plastic state so that it takes the shape of the molds.
- The process
Before starting, we put mold release agent in the molds, the same one we use for the molding and casting week.
Our machine is a machine made in the lab. Therefore, it has its tricks. Assuming that Polypropylene is not the best material for this process, the first issue we encountered was that the heat was not homogeneous. So, Edu helped us with a heat gun. We managed to heat an area of the sheet, so we moved our pieces to that section. When we were ready, we wore protective gloves, grabbed the frame by its grip, and 1, 2, 3 we lower the frame towards the molds.
To our disappointment, the molds did not turn out well.
Download files here:
Learnings
The preparation process is long for how simple the procedure is. Partly because of the characteristics of this machine where you have to do a lot of manual work. But on the other hand, we did not choose a good material to carry out the process.
I think it is key to take into account the limitations of the machines that one uses, and to be able to maximize their efficiency. In our case, the problem was clearly the material.
