INTRODUCTION TO APPLIED COMPUTER

132 VALUE ADDED SIMULATIONS OF DIE CASTING PROCESSES Noise Factors Control Factors Number of F actors Upstream Downstream R D Adv anced Engineer ing Product Design Product Design Product Design Product Launch Production End User Figure 9.1 Control factors and potential problems in the product development cycle. The cost to solve problems also increases as a product matures. As more concept and design decisions are made, resources are consumed. This is shown graphically in Figure 9.2 with the life cycle cost lever. 2 As a product approaches launch, resources have been expended to build tooling and test processes. Changes at this stage of a product’s life cycle require many steps to be repeated, often with increased cost due to overtime in a desire to meet timing plans. Figure 9.2 illustrates the benefits of predicting and solving problems early in a product’s life cycle. Addressing problems late in development or after launch is a drain on resources and lowers a company’s competitiveness. Don Clausing presents three levels of competence when ad- dressing problems during a product’s life cycle 3 : 1. Problems are found. Wishful thinking allows many to be swept downstream. A large number end up in the market- place. 9.1 INTRODUCTION TO APPLIED COMPUTER SIMULATIONS 133 Design Concept Design Release Tooling Preparation Production Profits Figure 9.2 Project cost lever illustrating returns as a function of when an investment is made. 2. Problems are found. The total quality approach is used to find and correct the root causes of the problem. The infor- mation is fed upstream so that the same problem is not in- troduced in a later development program. 3. Problems are prevented. Potential problems and their root causes are identified before they occur. Optimization posi- tions the design as far as possible from all potential prob- lems. The information is fed downstream to ensure that the problem prevention decisions are understood and maintained to avoid the inadvertent later introduction of the problem. Most companies strive for the third level of competence, in which problems are prevented. Rarely is this third level ever met. In many cases, this is because problems cannot be predicated. Over the last decade vast improvements in computer hardware and software technology have made complex simulations of phys- ical phenomena possible. Today engineers and designers have 134 VALUE ADDED SIMULATIONS OF DIE CASTING PROCESSES available an ever-growing and continually refined set of tools to aid in product development. Mathematical models using both fi- nite element and finite difference techniques have been developed to simulate various product functions, conditions, and environ- ments, including steady state and dynamic fluid flow, stresses in flexing structures, vibration and fatigue life, electric circuits and dynamic magnetic fields, thermodynamics, and corrosion life. These simulations offer the design community the opportunity to predict problems early in a product’s life cycle. Corrective actions often can be made to resolve problems before designs and tooling have been finalized. In some cases, mathematical models have advanced to a level in which complete product validation is pos- sible through computer simulation, which avoids the need for costly prototypes.

9.2 COMPUTER SIMULATIONS OF HIGH INTEGRITY

DIE CASTING PROCESSES Advances also have been made in simulating metal casting pro- cesses. Specific to high integrity die casting, mathematical models have been developed to simulate several elements of the process, including die filling, air entrapment, liquid metal surface tracking for predicting inclusion loca- tions, solidification thermodynamics, 9.2 SIMULATIONS OF DIE CASTING PROCESSES 135 Figure 9.3 Computer simulation of die filling during metal injection. Courtesy of MAGMA Foundry Technologies, Inc. material properties after solidification, shrinkage porosity, and part distortion. Today’s computer simulations are highly developed, producing complex graphics showing the progress of metal flow during die filling Figure 9.3. Thermodynamic results obtained from com- puter simulations can be used to predict numerous issues, includ- ing hot spots on the die surface prone to wear and heat checking. Such data can be used to predict regions in a component prone to solidification shrinkage, as shown in Figure 9.4. Recent advances in computer modeling of high integrity die casting processes have focused on the prediction of residual stresses and component dis- tortion, as shown in Figures 9.5 and 9.6. Coupling process modeling with design simulations can yield significant returns on investment by optimizing both the manufac-