There has been a significant amount of development made since the second project update. First, an improved solidworks file was created that split the original design into two components: the meshed box, and an external door which is connected by a hinge. Additionally, using the Form 2 with High Temp material instead of the Ultimaker greatly improved the print quality of the two pieces compared to the prototype print. For the hinge, a 3 1/2” x 1/8” stainless steel rod was inserted into the printed box. To provide a locking mechanism for the enclosure, we chose to implement two magnets along the top corners of the door. Because there was a small displacement between the box and the door from the hinge, the magnets proved to be a viable solution as they bridged the gap between the two pieces. Lastly, additional post-printing fabrication was performed to fine-tune the design and ensure the best fit for the assembly.
Using SLA to print required the generation a large number of supports. As such, this meant an increase in print time compared to the first print. Preform has software that auto-generates the “most ideal supports”, however, that recommended orientation would take 13 hours to print. To address this issue, we played around with different printing orientations to see which orientation would reduce the print time while retaining the structure’s integrity. The recommended orientation had the box flat on the platform, while the final orientation, with the fastest print time, had the open side of the box at a 45o angle with respect to the platform. This change reduced the print time to fewer than 12 hours, making the official print time of the box 10 hours and 7 minutes.
The next step was to slice the door on Preform. Our goal was to have it print in under 2 hours. Initially, the auto-generation tool set the print time to 3 hours and 53 minutes. After changing the orientation, the final print time was 2 hours and 33 minutes. This cut off more than an hour, but not quite enough to be under the 12 hour threshold. After consulting Makerspace staff and the class TA, we concluded this was as close to the 12 hour time we could get. This print unfortunately did not work, as the door printed with some warpage and the hinge rod could not go through the holes, making the door unusable. To avoid warpage, we tried another geometry where the door was kept vertical. While this fixed the issue, it unfortunately increased the print time because the machine had to print at a higher angle. The result was satisfactory and is shown below in Figure 2.
The final box print was successful. It has strong angles and is rigid. The hinge also printed well. The only issue with this print was that some of the grids that didn’t get supports drooped. This shouldn’t affect the functionality or structural rigidity enough to be an issue. There were many supports that needed to be cut and sanded away, so some of the faces are rougher than others.
After both parts were printed, the holes for the hinges were filed out more to make a better fit for the stainless steel rod. This was done on the box hinges as they matched the diameter of the rod exactly. The door did not need much filing as the tolerances were about 0.015” greater to accompany for the swinging motion of the door. We also filed down the corners of the door so it fit well in between the box hinges. This included filing the backside of it as well so the square corner wouldn’t rub on the round hinge.
Lastly, to make sure the door would stay closed, small magnets were inserted. These magnets are fairly thin and when clamped together are the same size as the displacement between the box and door. Epoxy was used to solidify the position of the magnets, and the box with the attached magnets can be seen in Figure 5.
After all of this, the box was put to use in a dishwasher along with two retainers. The cycle was run at “high temp”. After the full cycle was complete, the box was examined for any deformations from the exposure the harsh environment of the dishwasher. The box did not have any visible deformations. It also stayed closed, so the magnetic locks performed successfully, and there was no standing water in the box so the grid system performed as designed. Based on this test, the part was a success.
Regarding future modifications for full optimization of this design, there are a few changes that can be made. The thickness of the part can be decreased by about 50% and still maintain its solid structure, which would reduce the overall size of the enclosure, and reduce the amount of material required to manufacture it. The height of the box can also be decreased by ¾” and still be able to perform its designed functions. Also, smaller magnets can be used that fit inside the corners and don’t overlap the opening of the box. These changes can help to decrease the print time significantly, and make the part a more refined product as a whole. Another consideration for improvements would be the material. With the limited time available to us, there was unfortunately no time to test the pH of the box, which would help us understand how the material handles the dishwasher’s environment over time, and if it is still safe to be used in contact with the retainers. While this material did print well and held up great in the dishwasher, it is not clear if the plastic would potentially affect the safety of the retainers, and as such would require additional testing.
Authors: Austin Schwark, Shianne Carroll, Nick Pocquette, and Riley Cockerill