Over the years, 3D printing has proven to be a pretty handy technology to have in one’s toolbox when it comes to making replacement and mechanical parts, like hand water pumps, transmissions, gears, and valves. For his Master’s of Science thesis this year, titled “3D printed relief valve analysis and validation,” John Anthony Dutcher, III, a student at the University of Northern Iowa‘s Department of Technology, used SLA 3D printing to fabricate prototypes of the internal pressure relief valve of a positive displacement pump.
The abstract states, “Additive Manufacturing allows for faster, lower cost product development including customization, print at point of use, and low cost per volume produced. This research uses Stereolithography produced prototypes to develop an improvement to an existing product, the internal pressure relief valve of a positive displacement pump. Four 3D printed prototype assemblies were developed and tested in this research. The relief valve assemblies consisted of additive manufacturing produced pressure vessel components, post processed, and installed on the positive displacement pump with no additional machining. Prototype designs were analyzed with Computational Fluid Dynamic simulation to increase flow through the valve. The simulation was validated with performance testing to reduce the cracking to full bypass pressure range of the valve. By reducing this operational range of the valve, the power requirement of the pump drive system could be reduced allowing for increased energy efficiency in pump drive systems. Performance testing of the 3D printed relief valves measured pump flow, poppet movement within the valve, and discharge pressure at operational conditions similar to existing applications. The Stereolithography prototype assemblies performed very well, demonstrating a 56% reduction in the pressure differential of the cracking to full bypass stage of the valve. This research has demonstrated the short term ability of additive manufactured produced components to replace existing metal components in pressure vessel applications.”
The gear found inside positive displacement pumps, developed over a century ago, was able to overcome existing performance limitations, but it was by no means perfect. These pumps need an internal relief valve, which provide protection against too much pressure; if there’s a reduction in discharge flow, the over-pressure system could fail.
“The primary focus of this research is to investigate the performance of an internal relief valve for a positive displacement pump, propose an improvement to flow conditions in the cracking to full bypass pressure range of the valve based on flow simulation and validate the performance improvement with 3D printed prototypes,” Dutcher wrote.
Over the years, the design of the internal relief valve in these positive displacements pumps has not changed much. But by using computer simulation, the design can be revised and optimized to make the part more efficient. As he wrote in his paper, Dutcher’s research validates the 3D printed prototypes, using Computational Fluid Dynamics simulation and perfrmance testing, “in the design development of an improvement to an existing product,” and also shows that costs and time can both be reduced by using 3D printing to manufacture the valve.
“Additive manufacturing has the benefit of customization, allowing for design changes,” Dutcher wrote.
“Developing customizable end use components that can manufactured at the point of use, allows for application specific products to be produced for pressure vessel applications.”
The valve prototypes, 3D printed using SLA technology, were shown to reduce the amount of cracking in order to fully bypass the stage differential pressure that’s necessary to operate the internal relief valve. FDM 3D printing was used to make mounting brackets to attach an LVDT sensor to the valve prototypes; this sensor measures the movement of the poppet (internal device in the relief valve that seals its surface) during testing.
In his thesis, Dutcher wanted to determine if 3D printing could successfully be used to produce components of a test valve for the positive displacement pump, if the valve’s geometry was able to be optimized to reduce cracking based on flow conditions, and if the 3D printed prototype valves would perform at the same level as existing ones made with conventional methods of manufacturing. Ultimately, while he did answer these questions and demonstrated that 3D printing does indeed have applications in developing new products, his research provided a viable proof of concept for improving the existing design of a product.
“The 3D printed prototypes were developed to reduce cost and delivery lead time for prototype testing,” Dutcher wrote.
“The flexibility in design permutations that additive manufacturing allows with customization provides the opportunity to validate multiple product designs in parallel.”
By using 3D printing to create the prototypes, Dutcher was able to develop several different design concepts at the same time, without getting caught up by the normal barriers that come with traditional manufacturing methods. SLA 3D printing also makes it possible to produce parts with “the dimensional tolerances of machined components,” which helps speed up the development of prototypes.
“This research has demonstrated the SLA 3D printing’s ability to reproduce existing machined metal components,” Dutcher concluded. “While extended performance testing was not the intent of this research, the 3D printed pressure vessel valve components performed very well in performance testing. The development of the design variations in timely manor would not have been possible without Additive Manufacturing. Testing has shown an improvement in the valve performance by reducing the cracking to full bypass pressure from 52.0 psi to 22.8 psi. The successful performance test to improve an existing product demonstrated the validity of the SLA 3D printed prototype assemblies.”
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