The Design Process Journal Altitude Part Two

Step One: Identify The Need or Problem

Step one of the prosthesis design process task was to identify a need or problem for a replacement human body part. Bianca and I chose to identify the needs of having a prosthetic big toe. This is because we found that the big toe on a human is one of the most important parts of the human body that is needed for balance. There are multiple other purposes of a prosthetic toe including aesthetics, stability, weight bearing and it can also prevent deformities from occurring in the foot. The main reason why we chose to construct a toe is to see for ourselves how people’s balance can be restored with the use of a prosthetic.

Step Two: Research The Need or Problem

We had to research the prosthetic big toe in order to have an understanding of what we were planning to make. It has been proven that 75% of the time, the big toe is in contact with the ground to provide the support needed to stay balanced. Prosthetic toes have been made to bear the weight and pressure of humans without breaking or falling apart when in use and also to provide balance to the human structure. A prosthetic big toe can be attached to the foot in many different ways although the most common attachment method is to construct and design the toe so that it slips over the foot like a sock or a slipper. It is sometimes made so that it slides over the second or even third toe for extra support and so that the prosthesis stays in place. The prosthetic big toe functions almost like a normal toe despite the fact that the movement within the toe is slightly restricted. It restores the balance to the amputees and leaves them feeling normal like everyone else. We also found that prosthetic toes are often made out of silicon, wood, plastic, foam or carbon fibre depending on the activity levels of the clients.

Step Three: Develop Possible Solutions

The next step that we took was drawing up some initial ideas of what exactly we were planning on making. These drawings were ideas of what the toe needed to look similar to in order to satisfy the needs of the amputees. After this, we went back onto the internet to research the average size of a big toe. This was important for our prosthesis as we were required to make a realistic toe that could take the place of a missing toe on a person. The size that we found to be most common was 28 millimetres. We decided that the material that we were going to make the toe out of would have to be plastic as it is the most affordable and adaptable material available to us. The plastic could be melted, glued and cut which was all the things that we would most likely need to do to the product. We had developed a few possible solutions of how we were going to make the prosthesis. This consisted of using the 3D printer or using spare parts and scraps to create our design from scratch.

3D printer.

Step Four: Select The Best Possible Solution

Bianca and I chose to use the 3D printer to design and construct our prosthetic toe. The next step consisted of finding a design in which we thought was most similar and would work best for our idea using an internet program called Thingyverse. There were reasons why we had to find a design instead of making our own. This is because we discussed the process with design technology teachers that were more experienced than us and they said that it could take up to a few weeks to design a toe especially as we are inexperienced with the program. This meant that by finding a design we could save time to construct, test and even redesign if needed all before the deadline of the assignment.

Computerised design.

Step Five: Constructing A Prototype

To construct our prototype we put the design onto makerbot which was a a computer software that allowed us to adjust and shrink the measurements to a realistic size of an average big toe. After this, the process seemed fairly straight forward, we transferred the design over to a USB by exporting the file from makerbot. Then all we had to do was take the USB to the 3D printer in the design technology building and press the print button. It took a total of one hour and fifteen minutes to print the complete design which was in two pieces. We also had to sand down the ends of both pieces so that they would be flush and join together with no problems.

Design on Makerbot program.
Completed printing in 3D printer.
Sanding the ends of the product.

Step Six: Test and Evaluate The Solutions

To make sure that our prototype was accurately judged we created four criteria to assess it by. These were the attachment, ability to bear weight and balance, comfort and also the aesthetics and realistic appeal of the toe. We figured out that the toe was very light and weak and that it would not pass the test of strength in the end so we filled it with plasticine.

Half filled with plasticine.
Completely filled with plasticine.

Then we super glued the two pieces together and held them tight with a rubber band to set. After twenty-four whole hours of drying we found that it still hadn't stuck together. At the time it had seemed like a great idea, but then we were told that the plasticine would never stick with the glue due to its texture and softness.

Super gluing the parts together.
Holding the super glued parts together with a rubberband for 24 hours.

We tried duct taping the pieces together and this seemed to work until we started testing the prototype with small amounts of pressure by squeezing it with our hands.

Duct taping the toe together.

The next idea that we had was to melt out all of the plasticine and fill the toe with another substance that would become hard and be able to glue together. We grabbed a heat gun from the design technology building and we asked whether this process would melt the plasticine but not the product itself. We were wrongly informed that it wouldn't melt so we started the heating process. Unfortunately, the plastic 3D printed design melted and we were left with a destroyed toe.

Melting the plasticine inside the product.
Destroyed, melted toe part.

Step Seven: Communicate The Solution

To communicate solutions for our problem we first worked out what went wrong and thought of some strategies to fix the problem. We found that the best idea was to simply reprint our product. We did some research to find what substance we could use to stick our parts together that would dry solid and make the design stronger. We found that builders bog and liquid nails were the two best solutions for our idea. Although, after enquiring with the design technology staff we found that only liquid nails was readily available in the TSAC workshop. If we wanted to use builders bog we would have had to buy our own from Bunnings Warehouse which would cost twelve dollars.

Step Eight: Redesign

We reprinted our design from the 3D printer although this time it was black as we used a different machine. It only took forty-five minutes to print the second time as we made it slightly smaller to be more realistic.

Reprinting the design on the 3D printer.

Once it had printed we filled the two parts with liquid nails and left them to dry for twenty-four hours. When we came back the next day, we put super glue on both parts and held them together with a rubber band.

After a further twenty-four hours of drying, we painted the toe that was now in one piece a skin colour made out of white, red, black and gold paint. Now that it was completed we then had to start testing using our four criteria.

Painted toe prosthetic.

Step Nine: Testing and Evaluating Prototype Two

Using our four criteria of attachment, weight bearing, comfort and aesthetics we tested our prototype. To attach the prosthesis to the foot where the big toe is supposed to go we decided that it should be slipped inside a sockette or a thin stocking that matches to your skin colour. After easy manoeuvre inside the sockette to get it into the right place it would then stay without major movement. I would say that the attachment is satisfactory as it stays in place without movement.

Toe prosthetic inside sockette.

To test the weight bearing ability we both tried standing on the toe first with a body weight of 40 kilograms to start. As the product was filled to become solid the toe was stable and very strong. After this we tried an entire 55 kilogram body weight which still seemed to hold without any signs of failure or cracking. We decided that it was not necessary to go any further as no human puts their entire body weight on just one toe. The ability to bear weight was of very high standards for the prosthetic toe.

As we do not know anyone that is missing their big toe, we were unable to test it in the actual position that it should go. Instead, all that we could do to test the comfort was to feel for any rough spots or sharpness which we could not find on the part. We could have added a small layer of foam to the bottom of the toe for extra comfort and support although it was not necessary as it felt fairly comfortable on its own. Finally, to test the aesthetics we simply had to judge how realistic the toe looked and if it was appealing to potential users. Apart from minor errors such as a small lip where the toe pieces were joined and a slightly off colour than what we were matching it to, it seemed quite natural looking and realistic. We found through judging our product with the four criteria that it was designed and constructed well to match the needs of clients and the purpose of a prosthetic big toe.

Completed Prosthetic Big Toe
Created By
Nikita Hogrefe

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