After reviewing our initial prototypes and comparing their mechanical and aesthetic qualities, we created a hybrid prototype combining the best aspects of each part. The new part was printed, along with multiple interchangeable inserts to allow for further design comparisons. We compared each tool, and have further developed ideas for a final, fully functional part.
Design
Figure 1: Redesigned multi-tool with blade cover and no insert.
Our part redesign was based off what worked and what didn’t work from our previous iterations described in the first project update. We started with the base model for part A since it was the most comfortable to hold and the PLA used was shown to be more durable than part C. We kept the general shape the same but made some modifications and additions.
First, the soda can opener was widened since the original design was too narrow to fit a pop tab inside. The thickness of the wall was also made slightly larger, and the taper was reduced to allow room for the addition of the bottle opener.
Figure 2: Soda Tab opener
Next, the bottle opener from part B was added to the side. We kept the same geometries, but adjusted the orientation to create a better lever arm than part B.
Figure 3: Bottle opener
Additional changes were made to better fit an Xacto knife blade in the middle of the part. The area surrounding the blade was narrowed and curved, similar to part C, in order to make it easier to slice with while still protecting the user. The shape of the insert was modified to maintain a tight fit with the larger part, but to also allow for easy removal and installation of both the blade and magnet.
Figure 4: Chip Bag opener blade and cut out
We also wanted to try out more designs for the twist off cap opener since our original design worked well with some bottles but was too small for others. To save printing time and material, a circular pocket and keyway was made on the front of the part and several inserts were made to fit. Each insert tested different variations of twist off cap openers. Insert one (Figure 5) was similar to the previous designs, with vertical rectangular fins. Insert two (Figure 6) had a step in fin length halfway down, to help accommodate different sized bottles.Insert three (Figure 7) had shallowly slanted fins, and insert four (Figure 8) had aggressively slanted fins. These slanted fins were used in hopes of being able to grip any sized twist off cap.
Figure 5: Insert 1
Figure 6: Insert 2
Figure 7: Insert 3
Figure 8: Insert 4
Materials/Printing
The final tool was made out of black PLA and took approximately 10 ½ hours to print on an Ultimaker 3. Wall thickness was increased to 2 mm so that the tools would be more durable. Infill was set to 20% to allow for strength, but also to create a lightweight part. A small amount of support structure was needed for the tapered end of the bag opener, as well as inside the can opener slot.
The four twist off cap inserts was made from thermoplastic polyurethane (TPU), which is one of the more flexible plastics that the Makerspace had. We thought a flexible plastic would help grip different sized bottles better. It took around 10 hours to print all four inserts. Each insert that was printed needed no support structure and post processing.
Functionality Tests
The soda can opener still could not fully open a can, shown in figure 9. The tab bent and the opening was not pressed in at all. Furthermore, it was difficult to maneuver the multi-tool to even get it around the pop tab. This will need to be redesigned in future attempts.
Figure 9: Partially opened soda can.
The bottle opener worked very well. The multi-tool fit perfectly around a bottle cap and it was easy to push off. It was comfortable to hold and required minimal effort to use.
Figure 10: Bottle cap fitting into the multi-tool.
When testing the four inserts, we found that our original design, insert one, was the most effective insert used. Insert three and four were incredibly ineffective. The slanted fins created only a small amount of contact with the bottle caps, and the lack of surface contact caused the inserts to simply slide around the cap, offering no grip whatsoever. Insert two provided some grip, but it was substantially less than that of insert one. One last observation was that the TPU material seemed to flex too much, and actually offered less gripping power than the original PLA designs.
The bag opener was minimally effective at opening a small plastic bag when tested. The blade was able to fit into the holder, and was stable during use. However, the tapered section was still quite thick, and the bag would catch on the blade without sliding and cutting. The blade was only able to cut after specific positioning of the bag and part.
Summary
Our part redesign and reprint improved on some issues over our previous parts but we also saw several problems occur while testing. By combining aspects of our initial tests with this iteration we could produce a more functional part. Although we used the pop tab opener from part A in this final design, we believe the pop tab opener from part B would be a better option for a future part. A small angled slit could be placed near the corner of the part to allow for easy access as well as more room for the other tools. Similarly, the twist off cap openers on all of the initial parts were better because the more rigid PLA provided more force on a cap than the flexible TPU. The bottle opener remained the same since it worked well on the first attempt. And the bag cutter worked OK, but likely could be refined to require less force to use. Although our multi-tool might not quite be ready for commercial use, we were able to quickly test many design iterations by making use of rapid prototyping and additive manufacturing.