Our Making and Tinkering journey thus far has been enriching and fruitful, though we have also faced our fair share of challenges and setbacks. Ambition has always been an intrinsic element within our group dynamic, and this drove us to come up with a variety of complicated ideas which we felt had great relevance and potential on the commercial market. The most significant of these ideas included a proxy robotic arm, an automated 360-degree rotating camera platform, and our current screw sorting machine. Eventually, we found that it was difficult to model the robotic arm in a short amount of time, while we might also not be able to achieve a sufficient level of image precision to render effective functioning of our camera platform.
The decision to go with the screw sorting machine came from what we thought was a moment of inspiration at that time. While experimenting with a simple phone case, we found that we were able to trap screws of a certain head size underneath the phone case, while initiating a forward pushing motion would also allow the trapped screws to be rotated to a uniform orientation (such that the head is facing away). This experiment led us to our first prototype design for our machine, which consists of a head-sorting and a length-sorting segment. For the head-sorting segment, a slider (which would function like the phone case as mentioned above) would be attached onto a slanted board. The slider’s angle would be adjusted such that the gap between the slider and the board would only catch the screws of the desired head diameter. These caught screws would be pushed upwards by the slider until their heads rested perfectly on the edge of the board, while the other screws would be pushed off the board and into an overflow box. A thin ruler-shaped device would push the screws resting on the edge of the board towards the length-sorting segment of our machine. From there, the screws will be rolling down the edge of the slanted board, while there are holes of various sizes cut out in the boards. If a screw were short enough, it would fall tip-first into the hole and be collected in a container underneath the hole, while screws that were longer would continue rolling until it reached a hole of appropriate size for it to fall into. As we would soon find out, this was an overidealized approach which could not be replicated consistently. Nonetheless, it kick-started our project and indirectly led us to gain a much deeper understanding regarding the behaviour of screws.
One problem which constantly hampered our progress was the sheer variety and differences in the lengths and sizes of screws. Our project scope called for the sorting of all M2 to M6 SCH screws found in the M and T lab, and their lengths varied from 4mm (shortest M2 SCH screw) to 80mm (longest M6 SCH screw). The head-sorting segment of our first design did not sufficiently accommodate these extreme differences in length, and we soon discovered it was unrealistic to consistently “push” M2 screws upwards such that they rested perfectly on the edge of the board, as the slightest disturbance from a longer screw would knock them off. We encountered similar problems when attempting to push screws horizontally from the head-sorting to the length-sorting section, with longer screws knocking over shorter screws. Furthermore. even if all the screws were initially in the correct orientation, their length differences meant that they had different centres of gravity. For instance, a long 80mm screw might be able to roll horizontally for a long distance, but a short 4mm screw had a high tendency to tip over and fall off the surface. The impracticality of trying to control these varying movements and behaviours of different screws forced us to virtually abandon our initial head-sorting design.
The search for a new head-sorting design was a laborious and admittedly frustrating process. We realised that we needed a system that could accurately feed screws from the head-sorting to the length-sorting segments, even if the screws had a huge variance in length. Even after extensive research into other methods used by professional companies, we failed to find such a system on the market, as most existing feeding systems focus on a specific length. We eventually adopted a design where screws of the desired head size will be trapped in the gap between two horizontal rods. One of the rods would be adjusted by a motor to vary the size of the gap, according to the specific screw head size that the machine was sorting at that time. Screws that were not trapped in the gap would deflect off a slanted surface and onto a platform. The platform can then be raised by another motor and a trapdoor will control when these unsorted screws are fed back into the system for sorting. Having screws trapped between two rods made them less likely to fall, and we would be able to transport these screws to the length-sorting segment by tilting the rods or the entire setup.
We had more success when it came to our length-sorting design. The extremely short screws still gave us problems as they rolled too quickly down the edge of the board and had the tendency to fall off, but this could be rectified by attaching a movable plank to the board to control the speed of the screws. Meanwhile, our initial thought of screws of different lengths falling tip first into their allocated holes was mostly accurate, except for a certain dimension of screws. These were screws whose head size diameter was longer than the entire length of the screw itself, such that even when the screw fell tip first in the hole, the screw head would cause the hole to be blocked. We are still working to resolve this problem, though it is possible that we might have to exclude screws of these dimensions from the scope of our project.
Throughout this journey, we grappled with the idea of having to strike a balance between our ambitious expectations and what we could feasibly achieve over this short period of time. We became over-fixated on improving and developing our initial head-sorting design, as it was our own discovery and we really hoped to come up with a novel concept. When that was scrapped, all of us came up with alternative designs, but we focused heavily on eliminating all possible faults in every design and were hesitant to commit to any one of them. Eventually, we spent a disproportionate amount of time in the project conception stage which leaves us on a very tight schedule for the rest of the building and testing processes. Whilst a certain amount of brainstorming helps to uncover possibilities and potential approaches, we took it slightly too far and attempted to achieve perfection in every element of the screw-sorting process. Ultimately, we learnt that brainstorming and pondering is much more effective when directed towards clear priorities and goals, while learning to accept trade-offs and sacrifices appropriately allows us to better allocate our time and efforts, in turn increasing the quality of our product.