Date of Award

2017-01-01

Degree Name

Master of Science

Department

Mechanical Engineering

Advisor(s)

Ryan Wicker

Abstract

Additive manufacturing (AM) encompasses different technologies, including material extrusion 3D printing, a technology commonly referred to as fused deposition modeling (FDM), which is the focus of the work described in this manuscript. Additive manufacturing is a growing technology with many applications in numerous fields from the air force to medical offices. FDM is a process that uses thermoplastics, in this case polycarbonate (PC), where the PC is heated and selectively dispensed in a layer-by-layer process to create a 3D printed part. Currently, FDM systems have advantages over subtractive manufacturing or machining because cavities and other components (e.g., microchips, valves, and actuators) can be inserted at any layer. However, the FDM systems are limited in the functionality and purposes of the end-use product. Limited by the ability of printing one nonconductive material at a time, the commercially available FDM system cannot create parts with electrical functionality. Incorporating multiple materials such as the addition of conductive copper with the printed PC can mitigate the limitations of a conventional 3D printed part. Incorporation of conductive materials can create features such as electrically conductive traces, thermally dissipating heatsinks, and electromagnetic radiating elements. While there are efforts to fully automate the fabrication of electronic devices within the arena of 3D printing, the addition of electrical components into 3D printed parts is most commonly done by hand. There is a need to incorporate electrical components into parts using an automated method. The same is true when referring to placing and patterning conductive foils within 3D printed parts. Thus, the goal of this work is to develop a tool that will enable foil application within 3D printed parts.

For this work, a Stratasys Fortus 400mc FDM machine was used to fabricate PC parts. A hybrid manufacturing (HM) process was used, which can be described as an approach to building a product with additive and subtractive manufacturing. There are many ways to create a HM process, depending on the desired end result various manufacturing applications could be turned into a HM process. This work describes the design and development of a Foil Application (FA) tool for foil embedding into 3D printed parts to result in a HM process. With the use of a 3D printer and milling machine a HM process was created.

The FA tool was designed and implemented as an automated tool for applying copper foil onto the surface of a printed substrate. The copper foil was then machined using the CNC to create patterns. Copper foils were patterned for dissipating heat, but other potential patterns include circuits, ground planes or an electrical connection between layers, just to name a few. The FA tool included the capabilities of varying the feed rate of the dispensed copper foil, handling different copper gauge thicknesses and widths not to exceed 25.4 mm (1 inch). The ultimate goal of these efforts was to incorporate the FA tool into the Multi^3D Manufacturing System where a new generation of HM processes would be executed by one machine. The results of these new HM processes will ultimately culminate in the fabrication of complex parts with electrical capabilities through the embedding of copper foil. In previous work, electronic components in a 3D printed part were manually added after pausing and removing the substrate from the printer. The manual intervention proved to introduce registration errors and was deemed to be labor-intensive and tedious. The goal of the FA tool was to create a HM system that would eliminate human interaction in the building process; therefore creating a fully automated system to mitigate registration errors and tedious operations. The result would be a completed complex print with electronic capabilities with the unique capabilities of a 3D printer.

Upon completion of the FA tool, experiments were done; those of which resulted in multiple findings. First, the FA tool applied the foil to a designated position within 8% of the specified location. Also, the addition of embedded foil decreased the flexural extension of the PC part with the increase of width of the foil. With the addition of 12.7 mm copper foil the percent decrease of the flexural extension compared to the samples without foil was 19% and 42% for the 25.4 mm foil. Tests were done to determine how straight a copper strip could be applied along a 76.2 mm (3 inches) length. The length was user-designated and was not chosen for specific reasons. It was important to test how straight the copper foil strip was applied because different applications of the copper foil could require straight strips. Foil applications such as ground planes for antennas require specific location and dimensions of the copper for accuracy on electromagnetic response data. The copper showed a maximum horizontal displacement of 0.4 mm on either side along its length of 76.2 mm. Lastly, one, two and three copper foil strips were applied to three separate parts along three faces of a PC block. One of the exposed sides of the copper was positioned onto a heating plate. Thermocouples were evenly placed across three faces of the part to determine the temperature distribution across the PC part. There was a decrease of change in temperature across the copper foil with an increase of copper foil surface area. The percent difference between the part with no foil and one foil strip was a 26.3 percent increase. The percent increase from one foil to three foils was 37.5%.

These findings showed that the addition of a copper foil application tool was beneficial since applying copper foils aided in the temperature distribution of a heated PC part. The potential to integrate this tool into a single Multi3D machine would ultimately provide time-savings. The foil application process before the FA tool required the removal of the build platform, cool down time, manual application of the foil, and reheat time after the build platform was placed back into the printer. With the incorporation of the FA tool, these steps can be eliminated. With the tool inside the printer, the build platform would remain inside the printer and the cool down and heating time would be eliminated, making the multi-material integration faster than if done by hand. Not only would the incorporation of the tool into the printer speed up the application process but it would reduce the registration errors. When the substrate is removed from the printer and cools down, the part contracts. When the platform is returned to the printer and begins to reheat again, the substrate does not fully expand again; resulting in subsequent layers not lining up when deposited, creating a registration error.

Two different adhesive methods were developed and demonstrated in context of the PC and copper adhesion. One side was adhered to a cooler (147°C), solid PC surface; the other was exposed to a dispensed, semi-solid, hot (365°C) amorphous thermoplastic. The pre process required an adhesive and associated accelerant to adhere the solid PC substrate with the applied copper foil. The accelerant reduced the adhesion time, from 30 seconds to under ten seconds to adhere as the tool applied the copper foil. Subsequent layers of semi-solid PC were printed over the applied copper foil without post processing chemicals, the result of which was a rough textured surface finish with exposed copper foil in some places. Three chemicals were added to adhere the copper foil with the top layer of PC. The first was etchant: a chemical that etched the surface of the copper and removed the protective oxide layer. Then Isopropyl alcohol was added to remove excess etchant and clean the surface of the foil. Lastly an Acrylonitrile Butadiene Styrene (ABS) and acetone solution was added. The ABS solution was a thick liquid used to adhere the copper foil with the subsequently printed materials.

At the conclusion of the testing of the FA tool, the produced results exhibited that the FA tool could apply copper foil under a ten percent error. Electronic components, structural purposes and thermal dissipation are all within the capabilities of the FA tool in the Multi^3D Manufacturing System. Foil embedding through the application of foil application with the FA tool has proven to be an automated process with multiple purposes.

Language

en

Provenance

Received from ProQuest

File Size

96 pages

File Format

application/pdf

Rights Holder

Betty Elizabeth McKenzie

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