Designing a 3D Printer and 3D Modeling an arm

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For me, this project was something I was emotionally invested in. Attempting to create a prosthetic arm that was financially accessible for the average person was a daunting task. My goal within the team was to design a 3D printer capable of using high melting point strong plastics known as ASA a type of Plastic commonly found in car interiors. The printer was designed to print most of the parts on a standard FDM bed while the smaller parts would be printed in a DLP / SLA printer. One of the biggest hurdles while approaching this project was designing a model that could be modified to fit any person. Our approach to making it easy and accessible and cheap was to use the IR technology in the Kinect and scan the opposite arm to mirror it and then produce it. 

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Since my focus was not the internal electronics and it was primarily the design of the printing process and 3D scanning technology I will only be covering the design of that below.

3D Printer Design

Starting from the baseline we had 1 Makerbot printer but the bed size and limitations within the nozzle density caused that to be only useful for prototyping. For the commercial model, we would need to design a printer using a Steel nozzle at a 0.15mm size and a bed size of 400x400x400 to maximize print time. Since the management team wanted to build everything in the house I put together a parts list and set up the software requirements. From then we moved forward into researching the limitations ASA and comparing the price point to other types of plastic for our use case. 

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From that point, it was all about creating a means to turn the scans into a mailable model using a combination of software for the Kinect and modeling software such as Fusion 360. 

Printing Process

Designing the printing process was the most arduous part of the design. Making sure the printer would not have to be tinkered with in between prints was fundamental. Researching the means to do this was simply due to the nature of the open community within the 3D printer tinkerers. We decided to go with the laser bed leveling method using MatterControl as the slicer and an IR laser for the bed leveling hardware.

Final thoughts

Sadly I didn't have the opportunity to see this project fully develop as I moved out of Florida for a job in Virginia but from the experience of it and what did materialize is the understanding of the fundamentals of plastic manufacturing through 3D printing and the process to turn a 3D scan into a model that can be used to modify designs for products to tailor fit a person. 

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