WHAT IS A GOOD GATING SYSTEM? or QUANTIFYING QUALITY — BUT HOW?

摘要

Casting process simulation is usually used in an iterative procedure where the engineer modifies the design step by step to achieve improvements. When designing gating systems for example, the thickness and the shape of the runner may be modified in order to prevent air from being enclosed by the melt. Today, the search for improvements can be performed by an optimization algorithm if the decision process driven by human experience is replaced by a mathematical, analytical system of rules. Therefore quantitative criteria are needed which allow the comparison of designs through simple scalar values, leading to rankings of the possible variants regarding certain points of view. Existing criteria calculated by standard casting simulation software already contains much quantitative information, but this information has to be concentrated into representative scalar values. The most important question is therefore how to quantify or how to classify global or local results. Furthermore it is necessary to think about totally new quantitative results which meet the requirements of an automatic design optimization. Such a quantity can be for instance the average deviation of the main flow direction in a certain area. In several examples we will discuss what kind of problems arise answering the question "what is a good gating system" in a formal way. Using different quantitative criteria or various combinations of these criteria all result in different "good" designs being found. Each of these designs has its advantages and disadvantages regarding the involved objective functions. This leads to the conclusion that there is not necessarily one "optimal" gating design, but that the "best" design is dependent on the specific problems and objectives to be achieved for a particular layout.