Meaning
Temperature variation across the surface or through the thickness of a mould component affects the cooling of the resin. A steep thermal gradient can lead to internal stresses and warping in the finished plastic part. Designers use cooling channels and high-conductivity materials to manage these differences and ensure even cooling.
Monitoring the gradient helps the operator maintain a stable and efficient moulding cycle.
Cooling Uniformity
Ensuring that all parts of the cavity reach the ejection temperature at the same time is the goal of thermal management. When a thermal gradient exists between the top and bottom of the part, it will cool at different rates and bend.
Cycle Time
Removing heat quickly requires a temperature difference between the melt and the cooling water. However, if the thermal gradient is too large, it can cause the surface of the part to freeze too quickly, trapping air. Finding the right balance allows for a fast cycle without sacrificing part quality.
Tooling Stress
Rapid changes in temperature create mechanical stress within the steel of the mould itself. A persistent thermal gradient can lead to fatigue and cracking in the tool over time. Managing the flow and temperature of the cooling water helps to keep the steel at a more uniform temperature.
Differential expansion caused by these gradients often leads to the premature wear of sliding components. Infrared cameras provide a non-contact method for identifying these temperature imbalances on the mould face.
