Analysis of Sealing Methods for FDM-fabricated Parts

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Date

2011-08-17

Authors

Mireles, Jorge
Adame, Arturo
Espalin, David
Medina, Francisco
Winker, Rob
Hoppe, Terry
Zinniel, Bob
Wicker, Ryan

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Publisher

University of Texas at Austin

Abstract

As a result of the layer-by-layer deposition characteristics of Additive Manufacturing (AM) processes, fabricated parts exhibit limiting qualities and have yet to achieve the requirements for end-use applications. Specifically, the use of AM-fabricated parts in fluid pressure applications is limited due to part porosity as well as non-optimized building variables (e.g., build orientation and material properties). In an effort to extend the use of AM in more applications involving fluid pressure, parts manufactured with Fused Deposition Modeling (FDM) were sealed with a variety of sealants and tested under applied pressure. Eleven sealants with diverse chemical properties were applied to multiple geometries of FDM-fabricated pressure caps through brushing or vacuum infiltration. The caps were installed on pressure vessels and subsequently tested while safety precautions were taken to avoid catastrophic failure (i.e., exploding) caused by pressure differentials. Results of the testing provides a sealing method using BJB TC-1614 that enables FDM-fabricated parts to withstand pressures up to ~276 kPa (40psi) through brushing and ~138 kPa (20 psi) through vacuum infiltration. Other noteworthy sealants (Minwax Sanding Sealer, Minwax Polyurethane Oil Based, PRO Finisher Water-Base Polyurethane) that are readily available to consumers and easy to apply (i.e. no mixing ratios to follow, long working times) also had notable results by withstanding pressures up to ~207 kPa (30 psi). In addition, an analysis on dimensional changes was performed to determine the absolute difference between as-built and surface-treated parts. Parts that were infiltrated with BJB TC-1614 showed less dimensional changes (average absolute change of 0.104 mm) than parts that were brushed (average absolute change of 0.231 mm) however one-part sealants had smaller dimensional changes (maximum absolute change for one-part sealants of 0.065 mm for infiltration and 0.171 for brushing) with noteworthy results in pressure testing. Benefits of filling voids within FDM-manufactured parts enables end-use applications such as hermetic housings for biomedical devices and pipes/covers for thermodynamic systems such as heat exchangers.

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