17. WILCARD WEEK¶
The statement raised in the FabAcademy 2020 schedule for the assignment to be achieved this week 17 (Wildcard Week) is this:
- Design and produce something with a digital fabrication process (incorporating computer-aided design and manufacturing) not covered in another assignment, documenting the requirements that your assignment meets, and including everything necessary to reproduce it.
This week there is no proposed group assignment.
I have continued recording my FabAcademy assignments in my private calendar as I have been doing every week since the beginning of this course.
This week we are still homebound and without full access to the lab, so I’m going to use my imagination and try to do something that I can develop in the makeshift lab that I have set up at home.
For this wild card week, I have decided to use the vacuum thermoforming technique.
Vacuum thermoforming is a technique in which a plastic sheet is heated to a deformation temperature, stretched over a single-surface mold, and forced against the mold by vacuum, taking the shape of that mold. On cooling, the plastic will have acquired the desired shape.
In our Fablab we have acquired a machine to be able to work with this technique, but it has not yet been supplied to us due to the Covid-19 pandemic and the stock and distribution problems that are occurring.
As an alternative , we have users who belong to a public center (National Reference Center for Chemistry) that has one of these machines, similar to the one I have bought.
One of its workers, who uses our techniques from the SAIT of the UPCT a lot and whom I have helped a lot in carrying out analyzes, papers and publications for his doctoral thesis, has offered me to use this machine that is in his laboratories while we do not have the ours, the bad thing is that, at the moment it must be unofficial hours, since this center is also closed to the public for health security and only those in charge of some of its sections have access and in shifts so as not to coincide with each other.
So I depend a little on when he can go to use the thermoforming machine.
In this case, while waiting, I had to go from a first PLAN A to an alternative PLAN B , as in the previous week.
17.1. PLAN A¶
My goal with this task is, initially, to produce the transparent plastic packaging for the soaps that I want to do in the assignment of week 16, which I still have to do, because at the moment I am using my mold to make ice cream and chocolate bars with shapes. of baby motifs.
Later, waiting to be able to go to the CRNQ to use the thermoformer, I have gone to a plan B, which I also think will give a lot of play to show something manufactured in a different way in this assignment.
17.2. PLAN B¶
Already nervous, because I see that in this strange and difficult maelstrom, in which I am also having health problems, work is piling up on all fronts, and it is difficult for me to be able to keep up with the assignments of FABACADEMY, I begin to look for other alternatives to shape the work proposed this week.
On the website of the supplier of the products that I bought and used for the previous assignment (FEROCA), I have found something that I found very interesting for what I want to do now and I have decided to buy it since it is veeery affordable and try it, and yes It also works well, when I can go to the Fablab I will make a replica to a larger size to see how it works.
It’s about this:
It is a domestic thermoformer available in two sizes, A5 and A4. Comfortable standard sizes to have in small spaces.
I have decided to purchase the A4 size.
Its base of this DinA-4 size makes it perfect for making runs of small pieces in any type of plastic type Worbla which is available in different colors, normal, black, red and especially transparent, a more difficult worbla to work with with the stripper and that with this machine gives amazing results.
It also works with HIPS (High Impact Polystyrene) 1.5mm or less thick.
It is not suitable for use with PVC, Polypropylene or PET.
It is necessary to make it work the use of a standard vacuum cleaner .
In this video from the Feroca website you can see how it works:
It is actually a very simple machine made up of parts from laser cutter manufacturing .
These are the parts that came in the kit that came to my house after purchasing online:
I have also bought worbla of different colors for testing.
17.2.1. Design to be thermoformed¶
Regarding the form I want to obtain, I was keen to use Candela’s scan, in the previous task in assignment 16, so I will start from that idea again.
I start from the stl file obtained in the 3D scan of Candela and I try to divide it into two parts to use one of them and make the plastic shaping.
I am going to use the Rhinoceros software to do this.
I have not worked with this software for a long time, I used it a few years ago for naval design, it was very easy to get the frames and sections of the structure of a ship since this program works very well with surfaces and nurbs curves.
But I don’t remember how it works very well anymore and I don’t even have it installed on this computer I’m working with at home, so I have to start from scratch even with the installation.
I download Rhinoceros evaluation version 6 and I create a Rhinoceros account:
Once the license code for the downloaded version has been added and the installation done correctly, I am going to test with the stl designs from last week’s scan to see if I can create a cut in half and make a piece to use as a mold for the thermoforming process.
From Rhino, I import in stl of the Candela scan.
I have previously made a cut with the Geomagic software that is mesh treatment and with which I manage point clouds and scan meshes, with a plane that divides its head into two profiles.
I keep one of the parts that I want to make the milled mold from.
After importing this stl I want to see its dimensions, I go to mesh work mode and do all these operations:
I select “Finish”.
I search and watch videos to cut mesh, solids, create cutting planes…
There is a lot of information online, here are some useful links:
Consulting what I need, I manage to cut the mesh.
These are the generated files,
- Scanned head, ½ face cut, hair
- Scanned head, cut ½ two profiles. Right profile and left profile of the head.
- Head scanned, cut into three parts, to stay ahead and try to make a mask.
From here I use the profile section and I keep one of them, the left profile specifically, I am going to mill this in a size that fits in my domestic thermoformer.
17.2.2. Generating Gcode¶
To do this, I am going to configure the milling in the Aspire software, as the shoulder height is greater than the length of the milling cutter that I have with a round tip, from this program I make a cut and set milling parameters.
I do the simulation of the milling and I check that everything is ok and no strange things happen.
Simulation of the roughing process.
Simulation of the finishing process.
My mill tool has a maximum depth of 5cm. So I prepare my model so that it does not measure more than the depth of the milling tool..
I use Aspire software to generate the gcode. I have extruded polystyrene plates of 4 cm thick, so I glue 2 plates with glue to exceed 5 cm of the model. I get an 8 cm block.
Finally I am about to mill in a polystyrene of thickness = 8 cm
In the parameters imposed in Aspire, I select a milling tool 6mm in diameter, and choose 5mm depth of cut. I will select the feed rate later on the milling machine.
I also define the finishing operation. I select a 8mm diameter ball noise mill.
17.2.3. Milling my design¶
Álvaro and I ran away one afternoon and asked unofficial pe