A prototype was made out of foam. The intention of this foam model was to assess whether the sizing of the ergonomics are good and whether the handles are comfortable/practical to hold.
We discovered that the handles visualized in the 3D model were mirrored, so due to the foam model we were able to change the render for the final design.
Further, we discovered that the handles are too far apart when they are maximally apart. When holding the handles, it is quite difficult to squeeze the handles together to clamp a twist cap. Therefore the 3D-printed model will have handles that bend slightly towards each other. We will start off by trying a curvature of 5 degrees and test with the 3D printed model if it is more comfortable to squeeze the handles.
The 3D-printed prototype works fully and we were able to test it. We were able to open the twist caps we tested on and noticed a few things. The 3D-printed prototype proved that the 5-degree curvature of the handles is an improvement. We were able to squeeze the handles properly. To make it even more comfortable the width and the height of the handles can be increased a little bit. The twist cap is clamped, but we noticed the teeth need more grip. For the final design the surface of the teeth should therefore have an anti-slip material such as a textured rubber. Further when using the tool, we noticed against expectations, that instead of using the tool to twist the cap off, it is more natural to turn the bottle and hold the tool still. This is not necessarily a bad thing, but should be tested with the participant. A downside was that when squeezing the handles clamping the twist cap on a Lipton ice tea carton, one of the teeth got caught on the little flap on top of the carton. An upside was that even without the locking mechanism, the twist cap does stay clamped. But for the final design it should still have a locking mechanism.
Further while assembling the 3D-printed parts, we discovered that an extra connection is needed to constrain the plates of sliding slightly. Even the slightest movement within, will prevent the teeth from clamping a twist cap properly. On the prototype you can see an extra pin in the middle.