Wire Embedding 3D Printer

Abstract

The RepRap 3D printer is an open-source rapid prototyping machine capable of producing most of its own structural components. This printer can be built and run at a much lower price than a commercial 3D printer, and used to create copies of itself. Its first model, Darwin, was released online in 2008. It can print durable and accurate parts from thermoplastic materials, but it cannot currently print with electrically conductive materials. The Gada Prize, established in 2010 to advance the RepRap project, is a $80,000 grand prize and $20,000 interim prize that will be awarded to a machine like the RepRap which meets several additional specifications, including the ability to print conductors. The wire-embedding 3D printer project adds a wire-printing tool head, “SpoolHead”, to the RepRap Darwin model. The SpoolHead is a promising new approach to manufacturing hybrid wire-and-plastic parts, and an attempt to meet the conductive materials requirement of the Gada prize. This report documents the development and testing of the first SpoolHead prototype, a wire-printing mechanism that uses a servo-actuated mechanical pencil to insert metal wires into the heated surface of a printed thermoplastic part. The wires are then to be cut by a solenoid-actuated mechanism that shears the wire inside the main tube of the print head. Benchtop tests performed to validate the design philosophy of the SpoolHead gave positive results. The print head was then manufactured and tested on two designs proposed at the outset of the project, a rectangle and a spiral. The SpoolHead was able to print the spiral design to within the specified ±0.5 mm tolerances outlined at the beginning of the project. The printed rectangle was out of specification, with straightness errors of up to 0.8 mm and dimensions short by 1 mm of the design length. However, the errors responsible for this have been identified and can be easily resolved in future versions. It was found that the cutter design failed, requiring manual intervention in the cutting process. While alternative methods have been proposed to improve the cutter, a fully satisfactory solution remains to be found. Numerous recommendations are presented that outline how the future development of the SpoolHead should proceed, beginning with investigating replacing the cutter. Methods for future miniaturization of the device are presented, as well as plans for improved electronics and software.