Date of Award

2018-01-01

Degree Name

Master of Science

Department

Mechanical Engineering

Advisor(s)

David Espalin

Abstract

Printed circuit boards (PCB) have been widely used as a permanent solution for generating complex circuitries to power electronic devices. Over the years, PCB boards have proved to be reliable when powering electronic devices. However, when fabricating a printed circuit board, one must outsource to fabricate the boards when in prototype phase. Therefore, the risk of intellectual property theft and long lead time is an issue. The objective of this Thesis is to develop a hybrid multi-tool desktop material extrusion 3D printer that allows for easy integration (modularity) of tools to generate multi-functional 3D printed components.

The addition of an ultrasonic wire embedding tool allowed for embedding of conductive wires (traces) intended for interconnection between electronic components on 3D printed parts. Additionally, the implementation of tools, such as machining, has the potential to enhance extra feature resolution that is not achievable by material extrusion itself. Experiments were performed to understand the limitations of the modular desktop 3D printer and inform the user of design parameters and constraints for material extrusion and wire embedding. Repeatability tests of the XYZ axes were performed to understand the resolution of the modular desktop 3D printer. As a result, the deviation of the Y-axis was ±0.5µm with an average error of 0.11% for a 5mm travel displacement based on 10 measurements. Similarly, the X- and Z-axis showed a deviation for both a 2mm and a 5mm travel displacements of ±1.63 µm and ±0.78 µm with a percent error of 0.18% and 0.16%, respectively.

A computational steady state heat transfer analysis, validated by an experimental setup, was developed to understand the temperature distribution of the build platform. The computational analysis showed a maximum temperature of ~84ºC using a power input of 200W. To validate the computational analysis, an IR camera and a thermocouple data acquisition system measured the temperature of the build platform. The IR and thermocouple near the heat source reached 120ºC (set temperature) in approximately 8 minutes. The sensor located on the surface of the build platform 15.24cm (6in) away from the heat source reached a steady temperature of 101ºC in 14 minutes when the built platform was set to 120ºC.

To characterize the material extrusion of the modular desktop 3D printer, an extruder gear ratio of 1:30 was determined by trial error. Different line sizes were printed and measured ten times with a digital caliper to compare the set lengths with the actual extruded lengths. The extruded lines set to 10mm and 150mm measured 10.34±0.64mm and 151.93±0.58mm, respectively. After obtaining the extruder gear ratio, a ranking model inspired by Moylan et al. (2012) was used to compare the part dimensional accuracy of the modular desktop 3D printer with an industry grade Fortus 400mc (Stratasys, Eden Prairie, MN) FDM printer. With the help of an optical measuring tool, 25 features were measured for a PLA ranking model produced by the modular desktop 3D printer and a PC ranking model produced by the FDM 3D printer. Both parts showed undersized and oversized features at different locations. However, the largest oversized feature was produced by the modular desktop 3D printer having a percent error of 1.46% compared to the 0.02% error produced by the FDM for the same feature. That is, the difference from the feature size of the CAD model to actual printed feature was 1.12mm.

Parameters for wire embedding were developed using trial and error by varying the amplitude and traversing speed of the wire embedding tool. Embedding 26AWG solid copper wire onto an ABS plastic substrate required an amplitude of 60% at an embedding speed of 8mm/s. To characterize the wire embedding, three linear pairs of parallel traces were embedded with a center-to-center distance of 10mm, 1mm, and 0.5mm. Using an optical measuring tool, the center-to-center distances for the linear pairs were 10.31mm, 1.16mm, and 0.70mm. Finally, to understand the variance of the center-to-center distance between two parallel wires with angles, four fully dense ABS plastic substrates were printed and three different trace pairs varying in width with a sharp turn of 135º, 90º, 60º, 35º were fabricated. Complete failure of embedding the 35º turn was seen due to excessive amount of accumulated energy input in the same area as the wire was not retained by the polymer due the polymer flow when excessive energy was accumulated. This allowed for the development of design constraints, for example, a spacing of approximately 6mm was experimentally calculated to avoid interference with the component/feature when placed close to a wire trace with a sharp turn.

Machining capabilities were easily integrated to the modular desktop 3D printer. A rectangular ABS coupon was faced using a 1/8 end mill at a federate of 8mm/s to prove for easy integration of other tools. The system allowed a maximum payload of 86 kg (190lbs) when the load was at the center of the Z stage.

Language

en

Provenance

Received from ProQuest

File Size

92 pages

File Format

application/pdf

Rights Holder

Jose Francisco Motta

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