12. Machine design
Goals
Group assignment:
- Design a machine that includes mechanism + actuation + automation + application
- Build the mechanical parts and operate it manually
- Document the group project and your individual contribution
Tools Used
- Pureref - An amazing program for gathering images into a big mood board
- Concepts - My go to sketching app on the Ipad
- Fusion 360 - 3D CAD/CAM software from Autodesk
- Miro - Collaborative work space for research and design
TLDR; Nice images
Group Project
As the focus of this week is the group project pleas see link below for the full write up.
Individual Project
1. My Contribution to the Rotocasting Machine - Mechanical Design
For the project we designed and built a rotocasting machine.
My role in the project was the fabrication lead.
1.0 Research
The project we started out with a miro board where we brainstormed the general idea of the design and then assigned roles in the team.
1.1 Disassembly of Ultimaker 2
My first task was to disassemble the Ultimaker 2 to understand its components and how they work together.
From this we got stepper motors, acrylic panels, linear rods, bearings, and a whole host of other components.
2.0 Sketching
Im a big believer that jumping straight into CAD without a sketch is a big mistake. To that end, I took some time early in the project to sketch out the format of the machine.
As these ideas developed they became the basis for my team mates CAD designs.
2.5 CAD
Diarmuid was the CAD lead on the project but as there was a lot to do i took some of the less complex parts to free him up to work on the mechanical design.
This is the inner ring of the machine. It consists of 8 3D printed parts that are sandwiched between two MDF panels.
One of the strategies we used was for the printed parts to take all the complex features we needed and the laser-cut parts to provide the structure.
In this case all my printed parts were the exact same. They were designed to take either a set of bearings or a captured pulley.
3. Manufacture
The parts were exported from Fusion 360 using the export as mesh option and sent to Orca slicer for printing on the P1S.
3.1 3D printing
The parts were sliced using Orca slicer using standard PLA settings, We just added an extra wall for safety
We could have printed the parts in ASA or a different material but PLA is actually very rigid and we thought this would work well for the application.
The parts were printed across 3 Bambu Lab P1S 3D printers.
3.2 Laser Cutting
The side panels from the Ultimaker were used to create the uprights for the machine.
A challenge we ran into was the variance in thickness between the two sides. One was 5.7mm and one was 6mm.
This meant to get a press fit we had to create a handed set of slots on the base panel to accommodate the different thicknesses.
The rings were cut using 4mm MDF, this is a cheap stable materials that is perfect for prototyping.
This will likely be replaced with PLY or acrylic in the future.
3.3 CNC Milling
The base of the machine was cut in 24mm ply on our shopbot CNC.
The slots for the uprights were cut using a 3mm end mill and went through several rounds of finish passes and offsetting to get a good press fit.
The part was cut out from the stock with a multitool.
3.3 Fitting and assembly
The parts were assembled using a combination of press fits and screws.
4.0 Testing mechanical design
To test the design i decided to create a mold for an easter egg as it is easter weekend :)
So took a reference image of an egg into fusion 360 and revolved the basic shape and used the emboss tool to put and M onto the egg for my Daughter
As i planned to vac form the egg mold so i added some additional geometry to make areas for the 2 halves of the mold to register with each other.
The parts were sliced in Orca Slicer using the following settings:
- Layer Height: 0.2mm
- Infill Density: 55%
I used modifier objects to have areas of the print with no top layers so that air could flow through the mold and prevent air bubbles.
I then designed the MDF component that will attach the mold to the inner ring.
The parts were vac formed on a mayku formbox using the flex sheets.
I thought this would be a good choice as it would allow me to gently pull away from the mold.
Fully assembled
So my first test was to try and make a colcolate egg for my daughter.
We didn’t have a hotplate in the lab but the warm plate of our coffee maker was perfect to melt the chocolate.
This was poured into the mold, about 30% of the volume and spun up using a cordless drill for drive.
The egg was removed from the mold and placed in the fridge to cool.
Failure!! The egg was too delicate to be removed from the mold without breaking.
In hindsight this was not a bad thing as the material in the mold was probably not foodsafe anyway!
In the end I used some pigment to create a chocolate looking egg out of Jesmonite.
And here is the mechanism in all its terrifying glory
5. My Contribution to the Rotocasting Machine - Machine Design
5.0 Figuring out the RepRap Board
TODO
TODO
TODO
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6 Final Leg Planning
TODO
7 Laser Cutting Enclosure
TODO
TODO
TODO
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8 Integration and Assembly
TODO
TODO
9 Doneish!
TODO
!!Audio on for this one!!
In Summary
TODO
Things I would do differently next time
TODO
See below link to to files created this week: