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Final Prototype

In the final iteration, the cost of the frame has been further reduced. The ABS off-the-shelf enclosure box provided identical functionality but with over 50% cost reduction compared to the third iteration. The custom cutouts will be manufactured by Polycase, which is the vendor of the enclosure box. The pillars and motor housing (depicted in gray), as well as the syringe adapter (depicted in green) will be manufactured and fastened to the purchased enclosure. The same motor and lead screw system and syringe adapter from the second and third prototypes is used.

Cost for 25 units: $227.40

Third Prototype

In the third iteration, the complexity of the geometry has been reduced and the frame has been broken down into subcomponents to improve its ability to be injection molded in a greater quantity scale. The pillar and the motor housing will be produced separately and assembled onto the frame box during the assembly process with screws and nuts. By doing so, the cost has been reduced significantly. The same motor and lead screw system and syringe adapter design from the second prototype was used.

Cost for 25 units: $461.81

Second Prototype

The second iteration of the frame improved the accessibility of electronics by moving the opening to the bottom. This solution also improved the aesthetic of the overall product. Ventilation slots are applied to the bottom bracket and under where the motor is placed to prevent parts from overheating. The edges are smoothed out to provide stronger structure around the flange cutout pillars. However, such a part is hard to manufacture in a mass production scenario due to its size and geometric complexity.

This iteration includes an updated motor and lead screw design, using the same premise as the pre-built system from the first prototype, except it is to be assembled with individually purchased parts. The same stepper motor and threaded flange nut were used, but a stock lead screw was purchased and cut to the necessary length then connected to the motor via a coupler. The choice to assemble the system was made because it significantly reduced the overall cost.

In order to fix the syringe adapter issues from the previous iteration, the adapter has been increased in width to provide better rigidity for the part. Furthermore, the diameter of the rod slide rails has been increased to accommodate the linear bearings. Lastly, the modification of the geometry of the overall design contributes to better manufacturability and aesthetics of the syringe pump assembly. 

Cost for 25 units: $470.13

First Prototype

The first iteration of the syringe pump frame served the basic functional purpose of holding the motor and syringe in place, and the syringe can be plunged by the motor with the use of a syringe adapter. There are holes for the direction and on/off switches to validate the feasibility of the code. However, the frame was largely unrefined with flaws in its overall structure. The frame was 3D printed as a whole, and it is not a cost-effective design for the mass production goal of this project. The frame has sharp edges that will discomfort the user greatly. In order to assemble the electronics, an opening was placed on the side of the frame, which caused significant trouble in securing the switches, stepper driver, and breadboard.

The first design utilized a pre-built motor and lead screw system from McMaster-Carr. The motivation for this choice was the pre-built system came with a lead force versus speed plot. Instead of having to go through calculations to convert the motor torque to lead force, the plot showed the system could output the necessary force. While this saved a lot of time, the downside was the price of the pre-built unit was $169.95.

After 3D printing the syringe adapter (shown in green in the CAD image) and testing it, the syringe insert is found to be too low to include the entire backplate of the syringe. Furthermore, the rod slide, as well as the general structure strength is concerning.

Cost for 25 units: $549