(完整版)注塑模具外文翻译32毕业设计论文

优秀论文 审核通过 未经允许 切勿外传

附录2

Integrated simulation of the injection molding

process with stereolithography molds

Abstract Functional parts are needed for design veri?cation testing, ?eld

trials, customer evaluation, and production planning. By eliminating multiple steps, the creation of the injection mold directly by a rapid prototyping (RP) process of injection molding with RP demonstrated many times. What is missing is the fundamental understanding of and the injection molding process. In addition, numerical simulation techniques molding. But all current simulation packages for conventional injection molding are no longer applicable to this new type of injection molds, mainly because the property of the mold material changes greatly. In this paper, an integrated approach to accomplish a numerical simulation of in-jection molding into rapid-prototyped molds is established and a corresponding simulation system is developed. Comparisons with experimental results are employed for veri?cation, which show that the present scheme is well suited to molding Numerical simulation Rapid prototyping

1 Introduction

In injection molding, the polymer melt at to create the

injection mold directly by a rapid prototyping (RP) process. By eliminating multiple steps, this method of tooling a production material. The potential of integrating injection molding with RP technologies demonstrated many times. The properties of RP molds are very different from those of traditional metal molds. The key differences are the properties of thermal conductivity and elastic modulus (rigidity). For example, the polymers used in RP-fabricated stereolithography (SL) molds one thousandth that of an aluminum tool. In using RP technologies to create molds, the entire mold design and injection-molding process parameters need to be modi?ed and optimized from traditional methodologies due to the completely different tool material. However, there is still not a fundamental understanding of and the injection molding process parameters. One cannot obtain reasonable results by simply changing a few material properties in current models. Also, using traditional approaches when making actual parts may be generating sub-optimal results. So there is a dire need to study the interaction between the rapid tooling (RT) process and material and injection molding, so as to establish the mold design criteria and techniques for an RT-oriented injection molding process.

In addition, computer simulation is an effective approach for predicting the quality of molded parts. Commercially available simulation packages of the traditional injection molding process programs for

conventional injection molding are no longer applicable to RP molds, because of the dramatically dissimilar tool material. For instance, in using the existing simulation software with aluminum and SL molds and comparing with experimental results, though the simulation values of part distortion are reasonable for the aluminum mold, results are unacceptable, with the error exceeding 50%. The distortion during injection molding is due to shrinkage and warpage of the plastic part, as well as the mold. For ordinarily molds, the main factor is the shrinkage and warpage of the plastic part, which is modeled accurately in current simulations. But for RP molds, the distortion of the mold neglected in current models. For instance, [3] used a simple three-step simulation process to consider the mold distortion, which .

In this paper, based on the above analysis, a new simulation system for RP molds is developed. The proposed system focuses on predicting part distortion, which is dominating defect in RP-molded parts. The developed simulation can be applied as an evaluation tool for RP mold design and process optimization. Our simulation system is veri?ed by an experimental example.

Although many materials are available for use in RP technologies, we concentrate on using stereolithography (SL), the original RP technology, to create polymer molds. The SL process uses photopolymer and laser energy to build a part layer by layer. Using SL takes advantage of both the commercial dominance of SL in the RP industry and the subsequent expertise base that developed for creating accurate, and form-?t studies with very limited functional applications. However, the newer generation

stereolithographic photopolymers of the molding process

2.1 Methodology

In order to simulate the use of an SL mold in the injection molding process, an iterative method is proposed. Different software modules developed and used to accomplish this task. The main assumption is that temperature and load boundary conditions cause signi?cant distortions in the SL mold. The simulation steps are as follows:

1 The part geometry is modeled as a solid model, which is translated to a ?le readable by the ?ow analysis package.

2 Simulate the mold-?lling process of the melt into a photopolymer mold, which will output the resulting temperature and pressure pro?les.

3 Structural analysis is then performed on the photopolymer mold model using the thermal and load boundary conditions obtained from the previous step, which calculates the distortion that the mold undergo during the injection process.

4 If the distortion of the mold converges, move to the next step. Otherwise, the distorted mold cavity is then modeled (changes in the dimensions of the cavity after distortion), and returns to the second step to simulate the melt injection into the distorted mold.

5 The shrinkage and warpage simulation of the injection molded part is then applied, which calculates the ?nal distortions of the molded part.

In above simulation ?ow, there are three basic simulation modules.