How to Ease Mold Parameter Calculation

In injection molding, accurately predicting molding outcomes is essential. While using simulation software for comprehensive molding analysis is ideal for capturing all the details, it can be time-consuming. Traditionally, engineers have relied on theoretical calculations to predict certain conditions, such as shear rates for non-Newtonian fluids based on gate size and flow rates, or cooling times for parts with specific thicknesses.

Modern simulation software integrates these theoretical formulas into an easy-to-use interface, allowing for quick and accurate parameter calculations. Here are two practical examples:

Theoretical Calculation of Plastic Part Cooling Time

Cooling time is a critical factor in both product quality and production capacity in injection molding. It often constitutes the majority of the cycle time, which includes mold opening and part ejection. Efficiently evaluating cooling time can enhance productivity and reduce costs. Given that plastics are poor conductors of heat, the thickness of the plastic parts significantly influences cooling efficiency. Scientists have studied the cooling behavior of plate parts in molds to develop formulas for predicting the time needed for the average temperature in the plastic to drop to a safe ejection level.

The "Plastic Part Cooling Time" function in the MHC Design Estimator simplifies this process. Users can input material parameters, such as thermal properties and processing conditions, from a material database. The tool can be customized for specific part thicknesses, calculating the cooling time and plotting the temperature distribution curve. This visual representation shows temperature variations at different distances from the center of the part at the moment of ejection.

Theoretical Calculation of Gate Shear Rate

Shear heat is generated during the filling process of plastics, with the maximum shear rate typically occurring at the gate due to its being the smallest cross-sectional area of the part. An excessively high shear rate can cause material degradation or yellowing. Therefore, optimizing gate size is crucial: a larger gate may increase cooling time and reduce productivity, while a smaller gate may reduce packing efficiency and increase the likelihood of excessive shear rates.

The "Gate Shear Rate" feature in the MHC Design Estimator allows users to adjust gate sizes and calculate the maximum shear rate under different flow conditions. This tool uses specific formulas, such as those for round gates, to assist in determining the optimal gate size.

The MHC Design Estimator integrates classical theory into a user-friendly interface, enabling quick preliminary evaluations of parameters like gate size and cooling time before conducting full simulations. This approach helps users make informed decisions about molding parameters without requiring deep theoretical knowledge, streamlining the pre-simulation phase and enhancing the efficiency of the overall design process.