Week 7


Testing using the ABS prototype has continued with good results. The data continues to align with the theory that suggests a relationship between coating diameter and nozzle diameter. Our data analysis has brought forth an issue with our testing apparatus that is currently being investigated. The paint we have been using is water based; this means that while the paint dries, the diameter shrinks due to water evaporation. The percent solid that remains is not 100%, as it would be if the strand were coated with melted thermoplastic. To compensate for this in our data, we must identify how much water is lost when the paint dries. The water loss will be measured by weighing a sample of paint right out of the container, and again after it has completely dried. Once this is complete and accounted for in our calculations, our data can be further analyzed. Our prediction is an even more accurate proof of concept.

Earlier this week, our melting chamber design was finalized and sent to two machinists for evaluation and pricing. Unfortunately, both of them concluded that the complex specifications for our design were not achievable using the equipment they had on hand. It is possible to 3D print the part, but the initial pricing quotes were around $12,000. This is far beyond our budget, so we were forced to improvise. We had some materials on hand that could be used to create a similar but rudimentary melting chamber. These parts mostly consist of metal plumbing fittings, but with some modifications we believe that a working melting chamber can be constructed and used to coat a continuous carbon fiber. The modifications to the components are being completed by the machinists in Drexel’s Innovation Studio, and we are very thankful for their helping hands.  

Figures 1 and 2 show the details of the model we sent to be machined out of stainless steel for use as the melting chamber. The following link is a pdf version of a Detailed Drawing created from the model. Previous iterations of the design included an external hopper, which was streamlined into the main body of the chamber. Evaluation of the heating requirements led to an elongation of the design to accommodate a second heater. This evaluation was accomplished by applying the heat transfer formula to our design specifications, these calculations include heat lost to the surrounding air. Details concerning this calculation are included Here which is a pdf version of a MATLAB live script.



 Figure 1 - Melting chamber cross section


Figure 2 - Melting chamber assembly

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