Thermal Post-Processing of 3D Printed Polypropylene Parts for Vacuum Systems

Abstract

Access to vacuum systems is limited because of economic costs. A rapidly growing approach to reduce the costs of scientific equipment is to combine open-source hardware methods with digital distributed manufacturing with 3D printers. Although high-end 3D printers can manufacture vacuum components, again, the cost of access to tooling is economically prohibitive. Low-cost material extrusion 3D printing with plastic overcomes the cost issue, but two problems arise when attempting to use plastic in or as part of vacuum systems: the outgassing of polymers and their sealing. To overcome these challenges, this study explores the potential of using post-processing heat treatments to seal 3D printed polypropylene for use in vacuum environments. The effect of infill overlap and heat treatment with a readily available heat gun on 3D printed PP parts was investigated in detail on ISO-standardized KF vacuum fitting parts and with the use of computer vision-based monitoring of vacuum pump down velocities. The results showed that infill overlap and heat treatment both had a large impact on the vacuum pressures obtainable with 3D printed parts. Heat treatment combined with 98% infill reliably sealed parts for use in vacuum systems, which makes the use of low-cost desktop 3D printers viable for manufacturing vacuum components for open scientific hardware.

Recycled polycarbonate and polycarbonate/acrylonitrile butadiene styrene feedstocks for circular economy product applications with fused granular fabrication-based additive manufacturing

“…10b. After its fabrication, the external structural part can be easily adapted with an accessible heat source, i.e., a hot gun that can be used to seal pores [102] and reshape, to reach the 3-D profile of legs and ankles. The demo shin guard was designed by following these key principles [103,104]:…”

The Current State of the Art and Advancements, Challenges, and Future of Additive Manufacturing in Aerospace Applications

“…In addition, meticulous quality control measures and testing methodologies are implemented to ensure dimensional accuracy and structural integrity of the components. By addressing these challenges and developing efcient postprocessing solutions, SLS can fully utilize its potential in manufacturing aircraft components with diverse materials [34,44].…”

On the application of components manufactured with stereolithographic 3D printing in high vacuum systems

“…The application of printed parts in high-vacuum systems has been limited, though there are reports discussing the use of fused deposition modeling (FDM) and multi jet fusion (MJF) methods which have been shown to have some vacuum compatibility depending on ultimate surface finish and porosity [2][3][4][5]. Stereo-lithography (SLA) has become a standard method due to the control and precision of manufacturing and is substantially different to it's stablemates since the finished part is closer to a chemically bonded solid body and structures are not defined by lamination layers, thus SLA is a promising candidate for producing vacuum compatible bespoke parts.…”

“…Previous work has explored the application of vacuum sealants, such as "Vac-Seal" from SPI Supplies Inc. [6], post-manufacturing on acrylonitrile butadiene (ABS) and polycarbonate (PC) FDM prints, to create a physical barrier through which trapped water cannot out-gas [7][8][9]. Designed primarily as leak sealants for high-and ultrahigh-vacuum systems, such products typically contain toxic solvents which affect repeatability and present environmental challenges.…”

“…Many common vacuum sealants require high temperature curing, 260 -300 °C for VacSeal specifically [6], which are not compatible with many materials used for fabrication. Typical pressures achieved using leak sealant coatings range between 10 −4 − 10 −7 mbar when applied to ABS or PC [7][8][9][10].…”