A PC-based architecture for parameter analysis of vector-controlled induction motor drive

In this article a methodology for constructing a user interface for system control and data acquisition of a drive which is suitable for three-phase induction motors (3?IM) is presented. The entire hardware implementation is shown, including power and digital stages. Communication between the computer and the controller is engaged in order to enhance an analysis of power quality, adjust the controller parameters for tuning the flux and speed loops, and performance of the embedded algorithm. USB and Ethernet protocols have been put into operation in the user front-end because a high speed sample frequency is required in order to guarantee the real-time operation of the whole system. A software interface is developed using LabVIEW environment enabling features not only as filtering signals of phase voltage and current but also power spectrum measurements. Vector-controlled drive is programmed on a digital signal processor (DSP) in order to ensure efficient use of energy in the power stage and proper tracking of the reference at low and high speeds.     

Strain Dependence of the Uniaxial Compression Response of Vegetable Shortening

Many soft food materials, including vegetable shortening, exhibit complex rheological behavior. For shortening, a precise determination of rheological behavior is necessary to understand its functionality as a food ingredient. Commercial vegetable shortening was subjected to monotonic and cyclic uniaxial compression tests at a wide range of loading rates. The elastic modulus determined from unloading was a function of strain, varying between 740 kPa in the shortening’s strain hardening region to 220 kPa at large strain where perfect plasticity had developed. Visual analysis of shortening specimens during the compression process showed that a rate-dependent stress overshoot was attributable to the development of a shear band following strain hardening. An elastoviscoplastic constitutive model was developed to define the complex rate-dependent compression response of vegetable shortening. Using the fundamental parameters obtained from the different types of compression tests, the proposed model accurately predicted the uniaxial compression response of vegetable shortening over a wide range (three decades) of compression rates. A model with predictive capabilities of large strain properties is desirable because shortening is subject to large strain in essentially all applications.     

Material extrusion-based additive manufacturing of polypropylene: A review on how to improve dimensional inaccuracy and warpage

Material extrusion-based additive manufacturing (ME-AM) is an emerging processing technique that is characterized by the selective deposition of thermoplastic filaments in a layer-by-layer manner based on digital part models. Recently, it has attracted considerable attention, as this technique offers manifold benefits over conventional manufacturing technologies. However, to meet the challenges of complex industrial applications, certain shortcomings of ME-AM still need to be overcome. A case in point is the limited amount of semicrystalline thermoplastics, which are still not established as reliable, commercial filament materials. Particularly, polypropylene (PP) offers attractive properties that are unique among the ME-AM material portfolio. This review describes the current approaches of fabricating PP components by ME-AM. Both commercial and scientific strategies to make PP 3D-printable are elaborated and compared. As dimensional issues are especially problematic for PP, a comprehensive section of this review focuses on the strategies developed for mitigating warpage for PP parts fabricated by ME-AM. © 2019 The Authors. Journal of Applied Polymer Science published by Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48545.     

The Effects of Washing and Formaldehyde Sterilization on the Mechanical Performance of Poly(methyl Methacrylate) (PMMA) Parts Produced by Material Extrusion-Based Additive Manufacturing or Material Jetting

Nowadays, personalized medical implants are frequently produced through additive manufacturing. As all medical devices have to undergo specific washing and sterilization before application, the effects of a predefined cleaning routine that is available to the clinical institutes, washing with chemical agent and formaldehyde fumigation, on the mechanical behavior of printed parts are examined. Mechanical properties of parts manufactured by fused filament fabrication (FFF) and ARBURG plastic freeforming (APF) using two poly(methyl methacrylate) (PMMA)-based materials, 3Diakon and CYROLITE MD H12, respectively, are analyzed using flexural and impact tests. An influence of cleaning treatments on the mechanical properties of APF samples is not detected. FFF samples, however, show lower impact strength after washing, but not after sterilization. The fracture surfaces, porosity values, or chemical structure assessed by Fourier-transform infrared (FTIR) spectroscopy could not explain this decrease. Influence of the cleaning treatments on the material itself is assessed using thin compression-molded specimens. The influence on the stress–strain curves is negligible, apart from a slight but significant reduction in the yield stress. FTIR spectroscopy and scanning electron microscopy analyses of the fracture surfaces do not show detectable differences among differentially treated samples.     

Debinding behaviour of feedstock for material extrusion additive manufacturing of zirconia

Material Extrusion Additive Manufacturing (MEAM) is mainly used for the production of polymeric components. Using feedstocks similar to those of powder injection moulding, MEAM of ceramic components is possible. MEAM with filaments is also called Fused Filament Fabrication. Feedstocks are used as filaments; this imposes new requirements such as flexibility for spooling, stiffness to avoid buckling and constant diameter to ensure a consistent mass flow. Additionally, the binder should be removed without damaging the shaped part. In this paper, the debinding behaviour of MEAM feedstocks with zirconia was investigated. It was observed that higher temperature increases the debinding rate, but cracks occurred; the addition of a surfactant speeds up the debinding rate and reduces cracks; and a mixture of 10% isopropanol and 90% cyclohexane initially decreases swelling during debinding, but the debinding rate and the appearance of cracks is unaffected.     

Parameter Optimization of the ARBURG Plastic Freeforming Process by Means of a Design of Experiments Approach

Additive manufacturing finds more applications every day, especially in medical devices, ranging from models, tools, to implants. The fabricated parts have to withstand the mechanical loading applied during their lifetime. Hence, optimization of process parameters must be performed to reach the best performance of the manufactured part with the given polymer. A fractional design of experiments is performed with the ARBURG plastic freeforming using a medical-grade poly (methyl methacrylate) to improve the overall mechanical performance. Tensile specimens are produced, tested, and the impact of different parameter settings is analyzed to identify the factors with the highest impact on the mechanical performance. Based on the results, further parameter optimization is performed. A direct correlation between the density and the tensile properties of the printed parts is observed. Further, an influence of the processing pressure resulting from changes in the processing temperature is detected. Optimization for good mechanical performance is performed, and a relation between the filling of the parts, the nozzle temperature, and the discharge pressure on to the tensile properties is found. This investigation reveals that shrinkage due to changes in temperature and pressure has an essential role in determining the tensile properties of specimens produced by ARBURG plastic freeforming.