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.

FORMING PROCESS SIMULATION OF BIMETALLIC BILLET BY EXTRUSION FOR REW METHOD

The bimetallic joining elements were designed for lap joints of thin metallic (Fe-Fe, Fe-Al) as well as metallic – nonmetallic (Fe-PMMA, Al-PMMA) sheets by Resistance Element Welding (REW). The Cu tubes with an outer diameter of 4 mm, wall thickness of 0.5 mm, and a length of 11 mm filled with a solder Sn60Pb40 were used for the bimetallic joining elements producing. The required shape of joining elements is obtained by cold forming. Simulation by ANSYS software was chosen for the optimization of the forming process and geometry of functional parts of the forming tool allowing to use only one extrusion forming operation. The simulation results are stresses, strains, and modification of cross-section geometry of elements for the three proposed forming modes. The geometry of functional parts of the forming tool was compared with the results of cross-section macroanalysis of joining elements.

Numerical Simulation and Experimental Study on Rotary Cold Extrusion Forming of Screw Rod

The rotary cold extrusion forming process is a plastic forming process with very low material loss, especially in the production of hollow screw rods with equal wall thickness. In this work, the rotary cold extrusion forming process of a hollow T2 copper screw rod with a wall thickness of 4 mm and solid T2 copper screw rod was verified by experimental method. The finite element simulation software Deform-3D was also used to simulate the rotary cold extrusion forming process of the screw rod. The effects of the die with different heights of the working belt and the different wall thickness of the billet on the eccentricity, extrusion force, and forming torque in the forming process of the screw rod were studied. The results show that it is feasible to process hollow and solid T2 copper screw rods with equal wall thickness by rotary cold extrusion. With the increase of die working belt height, the eccentricity of the screw rod becomes smaller and closer to the ideal eccentricity. With the increase of the wall thickness of the billet, the amplitude fluctuation range of the eccentricity of the screw rod gradually decreases. The higher the height of the die working belt, the greater the extrusion force and torque required in the extrusion process, and the more intense the change of torque. These results also provide theoretical guidance for the production practice and lightweight transformation of the screw pump rotor.

Flow-induced Folding in Multi-scaled Bulk Forming of Flanged Parts and its Prediction and Avoidance

The quality of manufactured parts and the efficiency of forming processes are crucial in deformation-based manufacturing. In product miniaturization and micro-manufacturing, size effect induces many unknowns. Flow-induced folding related to size effect is one of them and has not yet been fully studied. In this research, the formation mechanism of folding defects in axisymmetric bulk forming was investigated, and a design-based method was employed to evaluate different tooling and process route designs for making a case-study multi-flanged part with three features and to explore the design-based avoidance of folding defects. In addition, a design evaluating framework of folding-free bulk forming was proposed, implemented and validated. Via analysis of the material flow, energy consumption, folding formation, and product precision of the four proposed forming processes for the case-study part, an upsetting-extrusion forming method via using a nested punch was found to be the most desirable. It was then implemented in the physical forming with three size scales. The results revealed that the flow-induced folding in the macropart was severe and regularly circuitous, but it is slight and irregular in meso and microscale. These findings are useful in the defect-free forming of multi-flanged structures and multi-scaled axisymmetric parts

Experimental research of ploughing extrusion forming multi-tooth tool wear and damage mechanism and workpiece defects

According to the characteristics of ploughing extrusion forming and the theory of metal cutting, the wear and damage mechanism, common wear and damage forms and causes of multi-tooth tools in ploughing extrusion forming are analyzed. Then, the correctness of the analysis of tool wear and damage mechanism and common wear and damage forms is verified by field cutting experiments. At the same time, the phenomena and causes of workpiece stagnation and cracks in the process of ploughing and extrusion forming were obtained through experiments. Finally, the reasonable processing parameters of ploughing and extrusion forming multi-tooth cutting tool were obtained.

Numerical Simulation and Experimental Analysis of the Semi-Solid Thixotropic Extrusion Forming Process for Producing the Thin-Wall Wrought Aluminum Alloy Mobile Phone Shells

Aluminum alloys have been widely used in various engineering applications due to their excellent physical properties such as low density, high strength and good cutting capacity. In this paper, the semi-solid thixotropic extrusion forming process is proposed to produce aluminum alloy 6063 shells for mobile phones. The effects of the operating parameters on the equivalent stress distribution, velocity field, temperature field, and the load of the top mould were investigated through numerical simulations. Optimal parameters were identified from the simulation results. The experiment was then conducted at these optimal parameters. The macromorphology and microstructure results of the mobile phone shells produced from the experiment are presented and discussed. It was found that the optimal process parameters for preparing aluminum alloy 6063 shell by the semi-solid thixotropic extrusion process were a billet temperature of 630 °C, mould temperature of 400 °C, and top mould speed of 10 mm/s. It was found that the mobile phone shells fabricated under the optimal operating conditions were fully filled with a clear outline and a smooth surface. The solid grains in the microstructure were small, uniform and nearly spherical. The average grain size of the microstructure for the product was obtained as 76.92 μm and the average shape factor was found as 0.76.