“Machine Week” was actually two weeks: Week 10 & 11, with a break in the middle.
Assignments
Our tasks for this week are:
- Group assignment:
- Design a machine that includes mechanism + actuation + automation
- Build the mechanical parts and operate it manually
- Actuate and automate your machine
- Document the group project
- Individual assignment:
- Document your individual contribution
Group Assignment
My group consisted of Me, Lena, Andrea, Riichi, and Hala. We were all interested in doing something with paste printing, and opted to make our own 3D paste printer.
A link to our group’s documentation of our Machine, ROTA, a Polar Paste Printer, is here.
Individual Assignment
My individual contributions to building Rota included:
- brainstorming and bringing ideation, gathering references and inspiration from prior work
- making a list of non-electronic components/OTS hardware needed (& hunting down components or identifying suitible replacements)
- assembly of the machine & parts
- redesign of several custom parts to be 3D printed
- brainstorm possible names and presented the options to our team to pick one
- documenting
Brainstorming & Ideation
At the beginning of the project, while we were still trying to figure out the exact scope and scale of our machine, we all spent some time individually gathering references and inspiration. Below is my section:
Non-electronic components/OTH hardware
We based our design off of a combination of the paste-adapted/enabled version of the Creality Ender-3 3D printer here in Fab Lab BCN and the RepRap R360, which is a 3D printer with a rotational (polar) bed.
The frame of our printer would be made from aluminum extrusion and we’d use a threaded rod and belt to drive the z and x axis motion, respectively, like the Creality Ender-3 paste printer in Fab Lab BCN. But the y-axis motion would be rotational/polar, accomplished by rotating the print bed, like in the RepRap R360.
One of my tasks was to make a list of all the non-electronic components we would need. I started by looking at the BOM for the RepRap R360 printer; although our shopping list would deviate from theirs since we were only borrowing the rotational bed piece from their design, it was still a good place to start.
Along with Hala and Riichi (who was taking point on the electronics components) we started familiarizing ourselves with the various containers and drawers of hardware around the lab.
We also started collecting components we thought we might need into a cardboard box to keep track of them. This included standard 3D printer OTS parts (a threaded extruded rod, endstop sensors, aluminum extrusion for the framing and hardware to attach to the extrusion, nuts, bolts, washers, etc.)
Assembly
All of us participated in this iterative task of assembling, testing, disassembling, and reassembling!
Initially we were excited because we thought there would be a wealth of documentation about the RepRap R360 printer that we could use as a guide in assembling our own polar printer version. However, we soon discovered that the company was defunct and much of the documentation for how to assemble their printers led to broken links. D’oh! I also spent some time on the WayBack machine aka internet archive trying to locate previous versions of the documentation and broken links to photos which could help us piece together their assembly process. We had a list of all the components they used but not a clear guideline on how to put them all together, so we had to sort of reverse engineer their process from the few photos we could find.
We experienced an issue with the print bed where there was some insability/motion where we didn’t want there to be any- ideally the print bed could be perfectly flat. We played around with different configurations of washers, bolt length, and bearings in order to get the bed stabilized so rotation was limited to only one plane!
Part Redesign
We went through several rounds of iteration and redesign in the process of building Rota. Andrea and Hala did a lot of the initial designing and redesigning but I took over for a few of the redesign rounds with some of the later parts.
Since Andrea designs in Rhino and I preferred to work in Fusion360, I had to convert the mesh files exported from Rhino to solid bodies I could work with in Fusion360.
I redesigned the assembly to fasten the cartridge containing the clay mixture to the X-axis as well as the piece used to connect the threaded extrusion rod to the frame to drive the Z-axis motion.
The original files are too big so I’ve included the link to them here:
ROTA - polar paste printer by andrearubio18 on Sketchfab
Cartridge Holder Redesign
The original version we 3D printed and tested came from the cartridge holder for the Fab Lab BCN paste printer, but we found that the cartrige we were using was a little too small. In order to fasten the cartridge in place we had to tighten the clasps down on the syringe pretty hard and they were starting to delaminate. Also there were some bolt through-holes that were a little too tight so we wanted to give ourselves more tolerance.
The first version I made had a longer body to support the body of the cartridge, and two clamping points. I also designed the clamps to tighten the cartridge to the cartridge holder.
The second version included an arm in the direction of the x-axis limit sensor so that the endstop would be activated at the appropriate time.
I also modified the clamps to be a little thicker in the second version, and just to be straight through holes, since we were still experiencing some issues with delamination in that region due to the forces from the bolt. A through hole proved more mechanically stable than a slotted opening.
Rod-Frame Adaptor (Rod Holder Adaptor)
Another part that needed to be redesigned was the 3D printed part which connects the threaded rod to the frame to drive the Z-axis motion. The first version was too thin so it was allowing too much motion and causing some unwanted binding in the Z-axis.
In the redesign I thickened the part to strengthen and stiffen it, and added a fillet to the 90 degree angle which would disperse the forces and prevent the part from starting to crack.
Naming
I came up with a number of different options for names and presented the options to our team to narrow them down.
Documenting
Like all of us, I contributed to the documentation by taking photos and video of my teammates and our progress with the machine over the course of the project.
I also wrote the sections in our Group page documentation hardware section about parts I redesigned.
Reflections
It’s amazing what we could achieve in two weeks! We pushed very hard in the beginning but it paid off: we were able to get our machine working and successfully do some test prints days before the deadline/presentations. Then we were able to prepare the slide and presentation without too much stress or time pressure. Our team worked very efficiently together, designing, assembling, and redesigning as needed. Everyone was very well organized and engaged.