Mechanical and Mechatronics Engineering
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This is the collection for the University of Waterloo's Department of Mechanical and Mechatronics Engineering.
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Browsing Mechanical and Mechatronics Engineering by Subject "3d printing"
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Item Computational Fluid Dynamics (CFD) Applied to a Glass Vaporization Chamber for Introduction of Micro- or Nano-Size Samples into Lab-Based ICPs and to a CFD-Derived (and Rapidly Prototyped Via 3D Printing) Smaller-Size Chamber for Portable Microplasmas(IntechOpen, 2018-02-14)Computational fluid dynamics (CFD) is used extensively in many industries ranging from aerospace engineering to automobile design. We applied CFDs to simulate flows inside vaporization chambers designed for micro- or nano-sample introduction into conventional, lab-based inductively coupled plasmas (ICPs). Simulation results were confirmed using smoke visualization experiments (akin to those used in wind tunnels) and were verified experimentally using an ICP-optical emission spectrometry (ICP-OES) system with a fast-response photomultiplier tube (PMT) detector, an ICP-OES system with a slower-response charge injection device (CID) detector, and an ICP-mass spectrometry (ICP-MS) system. A pressure pulse (defined as a momentary decrease of the optical emission intensity of ICP background) was not observed when employing widely used ICPs either with a CID detector or with ICP-MS. Overall, the simulations proved to be highly beneficial, for example, detection limits improved by as much as five times. Using CFD simulations as a guide, a rapidly prototyped, 3D-printed and smaller-size vaporization chamber (a scaled-down version of that used with ICPs) is being evaluated for potential use with a portable, battery-operated microplasma. Details are provided in this chapter.Item Controlling deposition location in atmospheric-pressure spatial atomic layer deposition(University of Waterloo, 2023-12-05)Nanoscale thin films exhibit unique properties and functionalities and are significant in a wide variety of applications and various sectors such as microelectronics, energy harvesting and storage applications, optoelectronics, sensing, and various other emerging technologies such as flexible electronics, 2D materials, quantum computing, micro electromechanical systems (MEMS), and packaging. Atomic Layer Deposition (ALD) is one method for producing thin films; its advantages include atomic-scale precision and control over film properties, which are vital for these applications. On the other hand, ALD is carried out under vacuum and therefore the process is expensive and slow. Atmospheric-Pressure Spatial Atomic Layer Deposition (AP-SALD) is an advanced technique for fabrication of thin films with properties similar to ALD but under atmospheric conditions and up to 2 orders of magnitude faster than ALD. AP-SALD is advantageous for its ability to deposit uniform, conformal and pinhole-free thin films. However, formation of powder can be observed during deposition using lab-scale and industrial-scale AP-SALD systems. A major reason for the formation of airborne powder particulates is due to intermixing of precursor gases. This can be a disadvantage as it can lead to non-uniform film growth, an increase in surface roughness and poor adhesion, film quality and properties. Moreover, formation of powder around the perimeter of the AP-SALD reactor head and the channels due to undesired material deposition can affect the performance and efficiency of the system. In addition to unwanted powder formation, AP-SALD is a coating technique that deposits a film over the entire substrate area, whereas selective deposition of a patterned film is sometimes desired. To overcome these challenges, methods to control the location of material deposited by AP-SALD are crucial. Therefore, the objective of this work includes developing methods to (1) either prevent or minimize the powder formation on 3D-printed AP-SALD reactor heads and (2) control what parts of the substrate are coated by depositing thin films at specific regions on the substrate. Several advanced strategies revolving around exhaust systems, in-situ monitoring and process optimization are being explored at the Functional Nanomaterials Group to prevent powder formation and effective removal of powders. In addition to these methods, coating the AP-SALD reactor head with materials that passivate the surface against gas-phase reactions may reduce powder formation on the reactor head. Area-selective atomic layer deposition (AS-ALD) by area deactivation is a technique in which thin films are selectively deposited on specific regions or patterns of a substrate (growth area) by coating the undesired regions (non-growth area) with growth inhibitors. In this work, the effect of dip-coating a custom AP-SALD reactor head with growth inhibitors to prevent material nucleation and powder formation is studied. Samples made of the same material as the reactor head are dip-coated with various growth inhibitors: polymers including poly(methyl methacrylate) (PMMA) and poly(vinyl pyrrolidone) (PVP) and self-assembled monolayers including octadecylphosphonic acid (ODPA) and dodecanethiol (DDT) for different durations up to 6 hours and 53 hours 30 minutes, respectively. Then AP-SALD depositions are performed on the samples to assess the effectiveness of the inhibitors. Some of the selected inhibitors demonstrate a clear ability to limit film growth on the 3D-printed samples. When 3D-printed reactors are coated with the promising growth inhibitors PVP and ODPA, powder formation is still observed on the reactor after performing depositions, although slightly less powder formation is observed when the reactor was coated with ODPA. Using 3D printing, AP-SALD reactors with complex channels that cannot be fabricated with conventional manufacturing methods can be fabricated. Fabricating custom reactor heads with channels that deliver precursors at desired locations on the substrate can enable direct selective deposition. In this work, novel area-selective AP-SALD reactors are developed to selectively deposit thin-film patterns on a silicon substrate. Two types of reactors are designed and tested; to deposit wide and narrow patterns separated by a small and large gap, respectively. Using the former type of reactor, a pattern is visually observed after depositions, however film growth with approximately half the thickness of the patterns is observed in the gaps due to precursor leakage and intermixing. Closely spaced narrow patterns are deposited using the latter type of reactor by slightly offsetting the reactor head relative to the substrate in subsequent depositions. This method can also be extended to depositing wide patterns and represents a significant advancement in the ability to deposit high-throughput patterned films by AP-SALD.Item Empirical Design Rules for Binder Jetting Additive Manufacturing(University of Waterloo, 2024-04-23)Metal binder jetting additive manufacturing (BJAM) is an additive manufacturing (AM) process that builds parts from a feedstock metal powder material by spreading a layer of powder, then depositing liquid binder over the desired cross-sectional area to bind the powder together. Once completed, the part is cured and depowdered, resulting in a green part with the desired form but lacking functional material properties. Heat treatment, typically in the form of sintering, is required to impart the desired properties to the material by pyrolyzing the binder and densifying the part. During each of these steps is the challenge of creating or maintaining a dimensionally accurate part that adheres to the intended geometry of the part that was designed. Each step has interactions between process parameters, material properties, and geometric feature characteristics that determine the degree of accuracy of the finished part. Benchmarking and understanding the physical phenomena of each of these steps is a field of active research with many domains to be covered. In particular, there is a lack of information on the dimensional accuracy of the printed green parts prior to post-processing and how to design parts to achieve a desired accuracy. The goal of this work is to develop a set of design rules that can be applied when designing for binder jetting additive manufacturing with stainless steel (SS316L). This was done by printing artifacts with geometric primitives at different scales and orientations to determine which features can be printed successfully. Six types of features were included in the design of these to examine minimum feature dimensions and clearances. The artifacts were analysed with the help of a custom developed automated computer vision approach to quantify the degree of dimensional accuracy. These results are compiled into a practical set of design rules for designers that express printability and dimensional error as a function of feature type, nominal dimension, thickness, and orientation. Future work is proposed to expand the formalization of design rules for binder jetting additive manufacturing and to apply this workflow to other processes.