Study on Size-Related Product Quality of Multiscale Central-Punched Cups Fabricated by Compound Forming Directly Using Brass Sheet

Meso/microforming has gained much more attention in the last decades and is widely used as a reliable method to fabricate meso/micro-scaled metallic components. In this research, a compound meso/microforming system which combines deep drawing, punching and blanking operations was developed to fabricate multiscale central-punched cups by using brass sheets. The parts with three scales were produced by using the brass sheets with various thicknesses and grain sizes to investigate geometrical and grain size effects on the deformation behaviors, dimensional accuracy, and material flow behaviors in the forming process. Through physical experiments and finite element simulations, it is revealed that the ultimate deformation load in the drawing-punching stage is smaller than that in the single deep drawing stage under microscale, but the results in the meso-scaled scenarios are opposite. In addition, the thickness variation is increased with grain size, but the variation of the normalized thickness variation does not show an obvious tendency with different size scales. In the bending area, the material flow is tangential to the thickness direction, leading to the formation of thinning area. In addition, the material flow is almost opposite to the punching direction in the punching area, avoiding the expanding deformation of the hole. Thus, the punching operation barely affects the dimensional accuracy including the thickness and hole diameter of the formed parts. Furthermore, the micro-scaled cups with finer grains have a better surface quality. These findings enhance the understanding of size effect in compound meso/microforming with the combined deep drawing and punching operations.

Effect of process parameters on formability in two-point incremental forming-machining of planar and twisted AA5083 blades

The deformation machining process (DMP) involves machining and incremental forming of thin structures. It can be applied for manufacturing products such as curved-surface blades without using 5-axis computerised numerical control machines. This work presents the effect of tool diameter and forming temperature on spring-back and dimensional accuracy of a simple fabricated part. The results of the first phase of the study are utilised to design the fabrication process of a curved surface blade. A feature-based algorithm is used to design the tool path for the forming process. The dimensional accuracy of the final product is improved through warm forming, two-point incremental forming, and extension of the bending zone to the outside of the product edges. The results show that DMP can be used to fabricate complex curved-surface workpieces with acceptable dimensional accuracy.

Lateral forces determine dimensional accuracy of the narrow-kerf sawing of wood

The shrinking global forest area limits the supply of industrially usable raw resources. This, in combination with the ever-increasing consumption of timber due to population growth can lead to the lack of a positive balance between the annual volumetric growth and consumption of wood. An important innovation toward increasing environmental and economic sustainability of timber production is to reduce the volume of wood residues by minimizing the sawing kerf. It results in higher material yield but may impact the dimensional accuracy of derived products. Therefore, the cutting tool geometry as well as the sawing process as a whole must be carefully optimized to assure optimal use of resources. The goal of this study is to better understand the causes of machining errors that occur when sawing wood with saws of varying thickness of kerf, with a special focus on re-sawing thin lamellae performed on the gang saw. Numerical simulations were tested against experimental results, considering influence of diverse components of cutting forces, in addition to the initial and operating stiffness coefficients of the saw blade. It has been demonstrated that asymmetric loads from the cutting process for the scraper saw blade can cause sawing inaccuracies. The simulation methodology developed in this research can be straightforwardly extended towards determination of optimal geometry of other cutting tools, particularly with the reduced sawing kerf. This may lead to more sustainable use of natural resources as well as an increase in economic gain for the wood processing industries.

A Promising Potential of Brown Algae Sargassum polycystum as Irreversible Hydrocolloid Impression Material

This study aimed to investigate the potential use of brown algae Sargassum polycystum as irreversible hydrocolloid (alginate) impression material. Potassium alginate extracted from Sargassum polycystum was prepared in three different compositions (14%, 15%, and 16%) and mixed with other standard components to form an alginate impression material. Prior to that, the purity of potassium alginate was quantified with Fourier Transform Infrared Spectroscopy (FTIR) analysis. As a control material, the alginate impression material from a commercially available product was used. All alginate impression materials were then applied to a die stone model. Dimensional accuracy was measured by calculating the mesiodistal width of incisors in the generated dental cast using a digital caliper 0.01 accuracy (five replications). In addition, to evaluate the dimensional stability, the impression results were poured at four different periods (immediately, 5 min, 10 min, and 15 min). An independent t-test was performed to compare the measurement results with p < 0.05 considered significant. Analytical results confirm that the impression material containing 15% potassium alginate gives the best dimensional accuracy similar to control (p > 0.05). Meanwhile, the optimal dimensional stability was produced in the impression material containing 16% potassium alginate. Our study suggested that brown algae Sargassum polycystum has a promising potential to be used as an alginate impression material in clinical application.

Fused deposition modeling of polypropylene-aluminium silicate dihydrate microcomposites

Polypropylene (PP) undergoes fast crystallization and resulting in rigorous shrinkage when it is subjected to high temperature likewise of the fused deposition modeling (FDM) process. This research study focuses on the investigation of the processing parameters and factors that decrease the warpage of PP during the FDM process. Aluminium silicate dihydrate (K) microparticles of different ratios were melt blended with PP by a twin-screw extruder, and filaments of about 1.7 mm diameter were extruded in a single screw extruder. Then, the extruded filaments were used to fabricate the dumbbells structure through the FDM process. The effects of optimizing the fused deposition temperature, coating the chamber with thick papers/fabrics, and coating a printer bed with PP material were also investigated in this study. Scanning and transmission electron microscopy, differential scanning calorimetry, melt flow, and mechanical properties testing instruments are used to analyze the microparticles dispersion, crystallization, flow, and mechanical properties of resulting samples. Uniformly dispersed filler and increased printing chamber temperature result in an increase of crystallization temperature and improve the dimensional accuracy of fused deposited specimens. The fused deposited PP-K10 wt% composite showed an improvement of up to 32% in tensile modulus compared to the neat PP.

Research on Improvement of Cold Extrusion Technology of Connecting Screw

In order to solve the flange and dent defects in the end face of the cold extrusion of the connecting screw, the Deform3D software is used to simulate the extrusion forming process of the connecting screw, and the velocity vector is used to study the metal flow law of the part in the cold extrusion process. According to the velocity field and deformation law obtained by the simulation, the end face depression defect in the forming process is predicted. An improved production process is proposed, and the simulation results show that the new process scheme effectively eliminates the “sag” defect on the end face of the part. Finally, the extruded parts with qualified dimensional accuracy are obtained through experiments, and the results are basically consistent with the simulation results.