Papers by Keyword: Rapid Forming

Abstract: A low dimensional precision is one of drawback for the GMAW-based rapid forming technique, which is related to pressure and heat flux on molten pool. To study pressure and heat flux on molten pool, the effect of droplet impinging process must been considered. A three-dimensional numerical model was built to analysis pressure and heat flux distribution on molten pool. Solving the model, it was found that pressure on the cathode by the arc decreases dramatically when the droplet is coming. As to heat flux, the appearance of droplet cuts down it within about 1.5 mm away from arc axial. Out of 1.5 mm away from arc axial, droplets effect on heat flux is not obvious.

Abstract: Metal fluid flow in weld pool would influence final quality of forming part in GMAW welding deposition-based rapid forming process. To numerical study fluid flow in weld pool, heat and force effects on weld pool surface must been made clear firstly. A three-dimensional numerical model has been built to study arc behavior in GMAW welding deposition-based rapid forming process. Solving the model, heat flux and pressure distributions on the cathode were derived. Calculated results show that heat flux from the arc to the cathode is related to arc temperature nearly above the cathode, and is not monotonous about radial distance within 2 mm distance away from arc axis. A maximum pressure with a value of 800 Pa happens at 1mm away from arc axis.

Abstract: Based on the foreign remanufacturing mode, the new remanufacturing rapid forming technology, which relies mainly on Surface Repair and Performance Improving Method has been explored and practiced. The aim of remanufacturing forming is to renew the original size of the waste components rapidly, and then improve their service performance. The advanced rapid forming technology, especially the high density heat source surface forming technology, is the important technique to carry out rapid forming. Based on the arc heat source, plasma heat source and laser heat source, three kinds of high density heat source remanufacturing forming technologies, such as high speed arc spraying forming technology, micro-arc plasma forming technology, and laser cladding forming technology, have been developed.

Abstract: With considering the Marangoni convection in the molten pool on plasma direct metal forming process, a finite element model posed to describe and reflect the flow in the molten pool. Results of temperature distribution modeling prepared by plasma direct metal forming process of metal powders in an Ar environment were numerically obtained and compared with experimental data. Powders of Fe314 and base plates of R235 steel were taken as sample materials. In the experiment a multi-stream nozzle capable of delivering metal powder coaxially with the plasma arc was used. The model revealed that the velosity of the front part of the pool is a little slower than aft part. Marangoni convection reinforced the convection and enhanced the heat transfer. Profile of the model is the same as the experimental data. This allows us to conclude that the model can be applied for preselecting the process parameters. Keywords: plasma, rapid forming, temperature field, Marangoni convection.

Abstract: The simulation of temperature field during laser direct metal deposition(DMD) were researched. The finite element model of single track cladding, multi-track overlapping and multi-layer deposition were established. The temperature field was simulated by ANSYS software basing on life-and-death element and cycle algorithm. Under different process parameters, the temperature and temperature gradient on the cross-section of sample were simulated during single- track scanning, multi-track overlapping and multi-layer deposition. Temperature cycle curves at different position were analyzed and were consistent with actually value. Both simulation and experiment showed that heat accumulation during continuous forming greatly affected the temperature of molten pool.

Abstract: The objective of this investigation is to study the rapid forming based on robot GMAW forming. The work may be divided into two sections. First study the modeling of weld bead profile. Self adaptive layered algorithm of variable direction is employed, which changes the forming direction on the basis of parts geometric character. In addition, the microstructure and performance characteristics of the formed parts are investigated. Its metallographic microstructure along the deposition direction shows obviously layered characteristic. The micro hardness values closely relate to the microstructure characteristics. The fracture mechanism of the part belongs to quasi-cleavage crack.

Abstract: The paper defined a concept of the utmost shapeable angle for the gas metal arc welding based rapid forming process, which is used to judge supporting material need to be employed or not when a inclined wall is deposited. If the angle formed by the outer normal of the inclined wall and building direction exceeds the sum of the utmost shapeable angle and π/2, then supporting material must be deposited to finish the inclined wall along the given building direction. The effects of metal transfer mode and welding speed on the utmost shapeable angle were studied. It is found that the ‘one droplet per pulse’ metal transfer mode in pulse-current welding based RP may obtain a bigger utmost shapeable angle than short circuit metal transfer mode does. The welding speed influences the utmost shapeable angle through heat input and bead profile. An abrupt bead is harmful to get a bigger utmost shapeable angle. Within a welding speed extension from 9 mm/s to 30 mm/s, the utmost shapeable angle gets the maximum value of 55° when the welding speed is 18 mm/s.

Abstract: Welding arc deposition is a high efficient rapid forming technology which can be used to rapidly form metal functional parts directly. While, Traditional slicing methods in the rapid forming process always produce ‘staircase’ or additional support structure which reduce deposition accuracy and efficiency, bring about the dissipation of materials. Even that it cannot exploit the advantages of welding arc deposition method. This paper proposes a slicing strategy which is suitable for rapid forming based on welding arc deposition. During slicing stage, the CAD model is decomposed into different pieces based on its geometrical feature to make each piece can be deposited in one direction without support structure, and layer thickness is determined according to the height of each sub volume and welding parameter database. A typical part is built with this method. It shows that this method is feasible and high efficient.