This week's assignment was to design and build a machine as a group assignment focussing on the mechanical parts. You can find the documentation of the whole machine here. Below is the description of my part of the project.
Designing a food deposition system for the Random Dutch Lunch Generator:
1. We started by brainstorming with the team how the machine should function and be assambled. The bottom part of the machine was meant to be a stage with a stepper motor which would move a lunch box back and forth, like shown on the bottom of the left sketch. The top part of the machine had to incorporate 4 different compartments for food deposition, two for holding a tube on the sides and two funnels in the middle. I was supposed to design the deposition method with funnels, whereas Henk designed the ones for the tubes. We discussed the measurements of the top part so that the motors and other necessary parts would fit in there.
2. I needed to think about whether to make the funnels from scratch, for example from wood or plastic, or buy ready made funnels and how to fit them into the given space. The determining factor at the end was how to attach them to the wooden casing or frame of the machine, and the complexity of the assemblage. Because the ready made plastic funnels come already with an edge with which you can hang them to the frame, I decided to buy 2 funnels which I could fit into the wooden casing. We tested the funnels with the chocolate sprinkles to see whether the funnel opening is big enough for the deposition.
3. It turned out that the opening was too small and the sprinkles got clogged. I needed a bigger opening which is why I cut away the bottom part of the funnels and attached a new cilinder shaped plastic sheet to adjust the size to the sprinkles.
4. To control the deoposition amount of the food falling from the funnels I had to create a method for opening and closing the bottom opening of the funnel. I decided to use a small servo motor that would control the circular movement of a cover that would open the hole for a deposition when the lunch box is placed underneath.
5. The servo motors I decided to incorporate into the mdf lids that would go on top of the funnels. First I thought I could engrave the 3mm mdf board we were using about 1,5mm so that it would be thinner and therefore fit onto the funnels by being on the same level with the top plate, like shown on the photos below. However, the mdf turned out to be too thin and broke easily. I made new ones with 3mm thickness, like shown on the photo above. Also I made a mistake by engraving the whole full circle and then cutting out the necessary shape which took a lot of time, whereas later I learned that I could have engraved only the necessary shape by selecting all relevant lines in the laser cutting software and assigning them to engrave.
6. The opening for the funnels was first made the same way. I engraved 2 full circles about 1,5mm thinner and then cut out the opening leaving a thin engraved edge on where to hang the funnels, so that they would hang lower and that the lids would fit on top.
7. However, at the end this didn't matter anymore because the thickness of the lids had to be increased and they stuck out form the top anyway. But this was not very disturbing and we decided to leave it like that.
8. At some point we discovered that the openings for the tube system that Henk was designing were not in the middle of the lunch box (like can be seen on the photo above, where the tube is not reaching the mid point of the lunch box) and we needed to push all the food deposition openings closer together. On the image below is the final design of the panels with right measurements, drawn in Fusion 360.
9. We laser cut the panels again, but this time in a smarter way. We engraved only part of the circles necessary and not the full circles, like can be seen on the photo below.
10. The new design fit perfectly. Henk's tube system was in the middle of the lunch box and my funnels fitted well in the middle.
11. When all the necessary components for the mechanism was ready I could pursue to testing the motor for the opening the cover of the funnels. The next steps of this are described under Assignment 16 - Machine Design.
Download here the design file: