Fully Three-Dimensional Toolpath Generation for Point-Based Additive Manufacturing Systems

While additive manufacturing and 3D printing achieved notoriety for their abilities to manufacture complex three-dimensional parts, the state of the art is not truly three-dimensional. Rather, the process plans for the majority of these machines rely on a stack of discretized, two-dimensional layers, which results in parts with stair-stepped surfaces, as opposed to being smooth and freeform. This work proposes a change to the 2.5D paradigm by using a configuration space approach to enable toolpath planning in a full three-dimensional space, allowing movements beyond planar slices. Algorithms are also presented to compute toolpaths on non-planar regions. Since the toolpaths take part and machine geometries into account, they are guaranteed to be collision-free. These techniques are relevant to many additive manufacturing technologies, including fused deposition modeling (FDM), directed energy deposition (DED), material jetting, and nozzle-based variants. The result of implementing nonplanar toolpaths is smoother, more continuous part surfaces.Mechanical Engineerin

Hard Broaching of Case Hardened SAE 5120

AbstractTo achieve knowledge of the effects of broaching to the component and the influence on subsequent process steps such as heat treatment and hard machining, broaching experiments were performed on plates made of normalized case hardening steel SAE 5120 in [1]. To investigate the effect of heat treatment, five broaching variants of [1] were chosen and hardened with two different case hardening depths, which were observed for effects generated from the surface layer carbon fraction. The hardened variants were analyzed for distortion generated through the hardening step and the specimen subsequently underwent a hard broaching stage in dry machining conditions. The cutting forces were monitored in-process, and the residual stress of the machined surface was determined using X-ray diffraction after the experiment. Surface roughness measurements also complemented the results. The results indicated that the cutting forces depend on existing distortion and therefore the volume material removed. It can also be seen that there is little influence on cutting forces with rising cutting speeds. Compressive residual stresses were present after heat treatment, but turned into tensile residual stress states after hard broaching. Effects from different case hardening depths and cutting speeds in the formation of surface roughness and residual stress could not be detected

Chip scale topography evolution model for CMP process optimization

A new chip scale model integrating pad height distribution and it’s interaction with topography on a patterned wafer was tested. Pad asperity height distribution was used to calculate mean contact pressure at a single asperity contact region. Material removal by a single asperity was evaluated from Hertzian elastic contact model and abrasive indentation model. Simulation on a test pattern predicted relatively higher removal rate and lower planarization efficiency with higher nominal down pressure. Oxide thickness variation over a test chip for a time period measured from specially designed test structure matched well with the model prediction

A cradle to grave framework for environmental assessment of photovoltaic systems

Environmental assessment of photovoltaic systems is a rich field, with representations of many technologies, regions and methodologies. This paper discusses some of the factors that strongly affect the outcomes of studies, encourages detailed reporting of normalization parameters and scope, and discusses a cradle to grave framework for benchmarking life cycle assessments of photovoltaic systems

Environmental performance characterization of atomic layer deposition

Atomic Layer Deposition (ALD) is emerging as a promising nanotechnology for manufacturing dielectrics and insulators on microelectronics devices. Its environmental performance has to be characterized at this early development stage to achieve sustainable manufacturing in the future. In this paper, we report our environmental performance characterization studies on ALD technology through material flow analysis and energy flow analysis. The assessed ALD process is for deposition of Al2O3 high-k dielectric films on a 4 inch silicon wafer. The results show that only 50.4% of input Trimethyl Aluminum (TMA) material is turned into Al2O3 film, while the other half is transformed into toxic emissions into the environment. Material usage efficiency of water is only 2.03% in current ALD processes. ALD is also featured with intensive energy consumption. For the studied ALD process, a total of 4.09 MJ energy is consumed for deposition of a 30 nm Al2O3 film, with averaged energy consumption at 13.6 KJ per cycle

Formulation of the Chip Cleanability Mechanics from Fluid Transport

The presence of solid particle contaminant chips in high performance and complex automotive components like cylinder heads of internal combustion engines is a source of major concern for the automotive industry. Current industrial cleaning technologies, simply relying on the fluid transport energy of high pressure or intermittent high impulse jets discharged at the water jacket inlets of the cylinder head, fail to capture the dynamics of interaction between the chip morphology and the complex workpiece landscape. This work provides a preliminary insight into an experimental investigation of the mechanics of chip transport at play, and how it can be used to build an effective chip optimization model that significantly aids in improving the cleanability of contaminant chips. The objective is to relate the mechanics of chip transport with the chip form parameters as much as possible, which makes the objective and constraints in the optimization model quantifiable. The end objective is of course to transmit this information upstream of the manufacturing pipeline in the form of a Design for Cleanability (DFC) feedback, which highlights the industrial cleaning problem as a design centric issue

Environmental assessment and metrics for solar: Case study of SolFocus solar concentrator systems

Life-cycle assessment (LCA) is utilized to analyze SolFocus Inc. concentrator solar systems. A hybrid LCA methodology is explained that combines process and input-output LCA techniques. The use of the greenhouse gas return on investment metric for solar technologies is discussed as a complement to energy metrics. Finally, preliminary results of a hybrid LCA for the SolFocus concentrator technology are presented. It is found that transportation and electricity consumption play a significant role in energy consumption and greenhouse gas emissions