Papers by Keyword: Vacuum Casting

Abstract: Aiming at solving the problem that results from flow instability two-component materials, uneven density and thus affects the product quality in constant pressure casting stage. Based for theory of polymer materials and hydrodynamic, establishing mathematic model of filling stage and proposing a uniform filling strategy through analysis of geometric characteristics of different mold, set pressure regulation curve in order to ensure uniform filling and stable flow for two-component materials in pressure casting stage. The experiment shows that the proposed method can actually ensure uniform filling, but also eliminate the product defects such as insufficient injection and burr, thus presenting a feasible solution to the problem of flow instability two-component materials and uneven density.

Abstract: Industrial parts with complex shapes are characterized by thin sections and complex geometries. Rapid vacuum casting is an ideal technology to manufacture complicated parts in small series production or prototypes. Contributions regarding simulation and analyzing of the parts made by rapid vacuum casting technology are presented in this study. Using dedicated software for simulating the casting process was analyzed and optimized the time of casting, the complete filling with material and also reducing the surface defects.

Abstract: Silicone rubber mold is frequently used in the indirect tooling. Automatic vacuum casting system is widely used to degas in the manufacturing of silicone rubber mold, but the cost of hardware is very expensive. A low-cost automatic vacuum degassing system is designed, build and test in this study. Optimized parameters for degassing process are investigated. The saving in the degassing time is about 23.4%.This system offers many advantages such as reducing human error of operator, reducing noise and air pollutions derived from the vacuum pump of the vacuum casting system.

Abstract: Based on craft features analysis of vacuum casting, this paper concluded that the automation level and control precision of control system are key influencing factors for products quality of vacuum casting. So the purpose of this paper is to resolve these disadvantages of existing control system of vacuum casting equipments. This paper designed a new full automatic intelligent control system which adopts two-level distributed structure. The system is consisted of motor control subsystem, vacuum monitoring and control subsystem, and bubbles detecting and eliminating subsystem. According to the function requirement of control system, this paper described selection and configuration of hardware and function implement of software in detail. Finally, this paper designed and realized a new automatic detecting and eliminating method of bubbles based on vision sensor technology, and presented an intelligent controller model based on Wavelet Neural Network (WNN) for motors. The experimental prototype of vacuum casting has been developed and a large number of experiments have been carrying on. These new controlling algorithms have being tested. The control system integrates vision sensor, intelligent control, microcomputer interface and imaging processing technologies, so it possess high precision, efficiency and flexibility and has a good market application prospect and high economic value. It will be breakthrough for precise rapid tooling.

Abstract: Bubbles in vacuum casting process are dense, tiny and overlapped. The difference between bubbles and the background is so indistinct that makes bubble detection a great difficulty. Bubble elimination has become the main obstacle in the way of vacuum casting machine’s automation development. Bubble automatic detection is the base of bubble elimination. A machine vision bubble on-line detecting and eliminating platform is constructed, using industrial high-speed CCD camera and professional LED illumination. According to the features of vacuum casting bubbles, the edge pixel ratio algorithm is designed especially for vacuum casting bubble detection. The algorithm is realized using VC++ and Open CV. The integrated system proposed can detect and eliminate vacuum casting bubbles on-line automatically. As it’s confirmed, there is an obviously positive correlation between the edge pixel ratio and the bubble denseness. This detection system makes sense in vacuum casting bubble elimination.

Abstract: In order to achieve high quality superalloy ingots, an investigation of applying linear electromagnetic stirring to the superalloy vacuum casting solidifying process has been put into effect with electroprobe microanalysis and optical microscope. The results indicate that an one sided, upward linear electromagnetic stirring with 50Hz frequency and 140A current can effectively refine the isometric crystals and shorten the ratio of central shrinkage cavity in superalloy ingots.

Abstract: The new technology of superalloy vacuum-electromagnetic casting was developed and the feeding mathematical model melt in vacuum-electromagnetic casting was established. The availability of mathematical model was approved by the experiments of the IN100 superalloy. The experimental results indicate that the feeding capacity of melt in vacuum casting can be greatly increased by imposing the 50Hz, 60A rotating electromagnetic stirring, which can decrease the central shrinkage cavity in superalloy ingots, so the quality of the superalloy ingots can be wide-range improved.

Abstract: In the process of vacuum casting, non-uniform flow front velocity about pouring material will lead to casting non-uniform shrinkage and warping deformation. Ideal filling pattern should make pouring material fill into the mold cavity with uniform flow front velocity. Give an optimization method of vacuum casting process, optimize the filling velocity in the filling process by combining numerical simulation and optimization method, and make the flow front velocity of pouring material uniform in the filling process, further reduce the warping deformation of casting. The example shows that the optimal model and the given solution algorithm is feasible.

Abstract: Aiming at the problem that current vacuum casting method lack of the filling ability in filling large & thin-wall castings. Therefore, a regulated pressure vacuum casting method is proposed, which using regulated pressure to improve the filling ability. The process and mechanism for regulated pressure vacuum casting method is presented and proved it through the home-made V450N-VD vacuum casting prototype. The results show that the regulated pressure vacuum casting method has higher filling capacity and can provide higher negative pressure during the whole filling process. So regulated pressure vacuum casting method has profound development potential.

Abstract: Most often, product quality is based on purity and homogeneity. To meet these conditions secondary metallurgy was developed including different methods for steel refining, but more important is the choice method of casting and its components. Casting metal melts is one of the key points that can ensure the desired product quality. Depending on the castings complexity, to obtain a high quality material several methods of casting have been developed. One of the most common methods of pouring large ingots is vacuum casting because the metal bath is protected from reoxidation. Another advantage of vacuum casting of steel ingots is achieving wide stream by injecting inert gas (Ar), this stimulates the floating of inclusions and prevents convection currents forming in the metal bath. This wide jet creates particularly advantageous conditions in the degassing process by increasing surface contact between vacuum and molten metal, managing to achieve maximum efficiency of removing gas and lowering the inclusion content. Like other methods of casting metals, besides the benefits of obtaining a quality material some disadvantages may influence the future products. One of the great disadvantages that can lead to scrap is the formation of a crown on the spray limiter during casting. Crowns get formed from non-metallic inclusions obtained from the "washing" the spray limiter. During ingot vacuum pouring because of the contact between steel and spray limiter pieces fall from the formed crown representing a powerful source of exogenous inclusions which can reject the finished product in non-destructive checks. Experimental research presents interesting information on the causes of crown formation and the solutions applied to avoid its formation.