After printing our prototype, we knew there were several changes we needed to make to our design in order to print a functional part that Jake could use. The first thing we addressed was the dimensioning of the T-slot. We sent Jake a sample T-slot attachment (FDM printed) in the mail to ensure that it fit into the mounting on his chair. After receiving the part, Jake informed us that the attachment was too large and that it did not fit into the slot. We asked Jake to retake the measurements, trying to be as accurate as possible. Jake didn’t have any access to calipers, so this process was difficult for him and his family. After another look, it turned out that the measurements he originally sent us were slightly larger than what the slot actually was. The dimensions changed from 0.75 x 0.75 x 0.25 to 0.6875 x 0.6875 x 0.25. So, knowing the slot was 11/16 x 11/16, we dimensioned the attachment to be 10/16x 10/16 to ensure that it fit into the slot without too much wiggle room.
The next issue we addressed was something we just recently caught. The way that we designed the curve of the lid requires that the lid travel up as it is opened (Figure 1). This will be a huge problem since the top of the compartment will be almost flush with the bottom of Jake’s armrest. So, we had to redesign how the lid opens to ensure that it will not hit the armrest as Jake tries to open it. We made a couple of adjustments to make that possible. First, we reduced the curvature of the lid so that it does not have to travel upwards, but rather outwards when it is opened (Figure 2). In doing this, we had to leave off some of the lid so that the compartment is not completely enclosed. We justified this change because Jake’s armrest will be acting as a roof to the cards anyways, so it is not necessary to print an entire roof for the compartment. Jake also needed room for his hand to fit into the compartment, so leaving the holes on top allowed for extra room for his fingers and hand to reach his cards. We also moved the location of the T-slot slightly back on the top of the compartment. This allows more room for the lid to open as the compartment is closer to Jake and not so far under the armrest. With these changes, we were able to get a clearance of about 0.25 inches between the lid and the armrest when the lid is opened.
The final enhancement we made to our design was the addition of magnets to the lid to ensure that it stays closed when not in use. We found 1/16 inch magnetic tape on amazon that we could apply to the both the lid and the compartment. As seen in the picture below, we cut out 1/8 inch slots where the tape can be applied to the compartment so that the lid can stay flush with the compartment when closed.
Figure 1 Figure 2