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Additive manufacturing of metallic components – Process, structure and properties

A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.

Fourier-transform method of fringe-pattern analysis for computer-based topography and interferometry

This chapter discusses leading problems linked to energy that the world is now confronting and to propose some ideas concerning possible solutions. Oil deserves special attention among all energy sources. Since the beginning of 1981, it has merely been continuing and enhancing the downward movement in consumption and prices caused by excessive rises, especially for light crudes such as those from Africa, and the slowing down of worldwide economic growth. Densely-populated oil-producing countries need to produce to live, to pay for their food and their equipment. If the economic growth of the industrialized countries were to be 4%, even if investment in the rational use of energy were pushed to the limit and the development of nonpetroleum energy sources were also pursued actively, it would be extremely difficult to prevent a sharp rise in prices. It is evident that it is absolutely necessary to pursue actively the development of coal, natural gas, and nuclear power if a physical shortage of energy is not to block economic growth.

World energy outlook

Additive manufacturing (AM) alias 3D printing translates computer-aided design (CAD) virtual 3D models into physical objects. By digital slicing of CAD, 3D scan, or tomography data, AM builds objects layer by layer without the need for molds or machining. AM enables decentralized fabrication of customized objects on demand by exploiting digital information storage and retrieval via the Internet. The ongoing transition from rapid prototyping to rapid manufacturing prompts new challenges for mechanical engineers and materials scientists alike. Because polymers are by far the most utilized class of materials for AM, this Review focuses on polymer processing and the development of polymers and advanced polymer systems specifically for AM. AM techniques covered include vat photopolymerization (stereolithography), powder bed fusion (SLS), material and binder jetting (inkjet and aerosol 3D printing), sheet lamination (LOM), extrusion (FDM, 3D dispensing, 3D fiber deposition, and 3D plotting), and 3D bioprinting....

Polymers for 3D Printing and Customized Additive Manufacturing


 In-flight particle state has been shown to play a crucial role in determining the properties of thermally sprayed coatings. Therefore, process control strategies have been suggested to keep the in-flight particle state constant in order to decrease the variability of coating quality. Such strategies are already used to some extent in industrial applications, where the particle state is measured before starting the coating of a part to make a go/no-go decision based on whether the values are inside a predefined process window. This paper shows the importance of the evaluation procedure of the in-flight particle state, with focus on process control applications. The paper demonstrates this on the example of atmospheric plasma spraying (APS) of yttria-stabilized zirconia (YSZ), using a commercially available sensor system Accuraspray for measuring the ensemble particle temperatures and velocities as descriptors of the in-flight particle state. It is concluded that the stabilization time of the particle jet might be different from what is practically considered. Moreover, the paper investigates an approach of monitoring the in-flight particle state during a coating run without having to install the sensor system on the robot arm.

Importance of Evaluation Procedure of Particle State in Atmospheric Plasma Spraying

In grinding the use of coolants is inevitable to achieve high precision surface properties under the need of high process performance and under reasonable material removal rates. In conventional grinding typically a significant share of the total production energy refers to the delivery and conditioning of the coolants due to the use of flood cooling, which contributes a significant portion to the production costs. However despite trends of minimal quantity lubrication and even dry grinding, the demand of metal working fluids is increasing worldwide. In order to reduce and optimize the use of coolants, profound knowledge about the fluid delivery into the grinding gap is important. Usually studies show the effect of coolants on the grinding process by the effect on the workpiece. They allow general conclusions about the share and distribution of the useful coolant flow, which is considered as the coolant flow into the grinding gap. On the other hand in-process methods can be used to assess the coolant flow. In a newly proposed experimental set-up the distribution by different nozzle designs and volume flows, respectively flow speeds, are studied for a cylindrical grinding process and can directly be visualized. Effects of the grinding wheel induced air-flow are fully considered. The main evaluation is done along the workpiece axis. It is shown that the distribution of the coolant flow inside the grinding gap is typically not entirely uniformly, also when nozzles with a consistent coolant supply are employed. Coolant distribution depends on the nozzle outlet cross-section, while different nozzle design can lead to even grinding results. It is shown, that the amount of cooling flow is not the main parameter. The influence region of single jet nozzles is typically much wider that their cross-section, which allows to use them in grinding. The results combined with a heuristic approach allow the optimization of coolant jet nozzles for grinding processes.

/pdf/investigation-of-the-coolant-fluid-flow-distribution-in-the-453kspcf7q.pdf

Investigation of the coolant fluid flow distribution in the grinding gap

Picosecond pulsed laser machining of hardened martensitic stainless steel drive shaft

Single crater dimensions and wire diameter influence on Wire-EDM

Silicon alumina nitride (SiAlON) and alumina toughened zirconia (ATZ) ceramics are applied for ceramic cutting tools to machine, e.g., cast iron, nickel base alloys and other difficult-to-machine materials. The state of the art technology for manufacturing of the cutting tool geometry is grinding. Laser processing of ceramics is already studied in terms of ablation rate and roughness evaluation with the application of dental implant manufacturing. In the present study, laser machining of the mentioned ceramics is explored with a laser beam source of 1064 nm wavelength and 10 ps pulse duration (FWHM). The angle dependent energy specific removal rate is described in a model and the optimal pulse fluence for the different materials and the irradiation angles can be derived. For processing at irradiation angle of up to 75° no decrease of the relative absorption could be observed. For ATZ, lowest surface roughness is determined for both, orthogonal and quasi-tangential processing angle. For SiAlON, the roughness decreases constantly for higher tilt angles. A significant difference in the material answer with change of the sample composition can be detected and the results show the potential of further developing SiAlON ceramics towards machineability for laser ablation.

/pdf/laser-ablation-study-of-cutting-ceramics-with-consideration-3s930c90.pdf

Konrad Wegener

Papers

Importance of Evaluation Procedure of Particle State in Atmospheric Plasma Spraying

Investigation of the coolant fluid flow distribution in the grinding gap

Picosecond pulsed laser machining of hardened martensitic stainless steel drive shaft

Single crater dimensions and wire diameter influence on Wire-EDM

Laser Ablation Study of Cutting Ceramics with Consideration of the Beam Inclination Angle