# Things You Should Know Before Selecting a Mould Temperature Controller | Moldex3D Blog May 29th, 2019

In injection moulding, we usually control the mould at a fixed temperature by making coolant continuously flow through the mould. If the coolant flow is not enough, or the coolant temperature is not as expected, the mould temperature won’t be able to keep at the designated temperature. The manufacturers of mould temperature controllers calculate the appropriate mould temperature controller specifications according to the size of the mould and the part. However, it can be a challenge for engineers and analysts using the simulation software to evaluate the performance of a mould temperature controller. In this article, we’ll share principles for using Moldex3D CAE software to better evaluate the performance of mould temperature controllers.

## The Relation between Flow and Pressure in Cooling Channels

In Moldex3D’s Flow analysis settings, users can apply two types of boundary conditions for cooling channels: flow rate and pressure. When the coolant flows through the cooling channel, the flow rate at the inlet and outlet are equal. Users only have to measure the flow rate at one side of the cooling channel, and the flow rate at the other side can be attained. Thus, using the flow rate as the boundary condition is easier to control. In terms of pressure, the inlet pressure is higher than the outlet pressure, and the flow is caused by this pressure difference. In Moldex3D, the default value of the outlet pressure is zero. Users only have to set the pressure boundary at the inlet, and this value will be equal to the pressure difference between the inlet and outlet. If we create a plot to show the relationship between the cooling channel flow rate and pressure, we can see that as the flow rate gets larger as the pressure difference gets larger. The two parameters are approximately proportional (Fig. 2).

Apart from the pressure difference, flow resistance is another factor that will affect flow. Flow resistance varies with some conditions, such as cooling channel diameters, channel length, channel wall smoothness, coolant properties, and flow rate. The Darcy–Weisbach equation shows the relations between these parameters (Fig. 3).

## The Relation between Flow Rate and Pressure of Mould Temperature Controllers

The function of a mould temperature controller is to push the coolant to flow and stabilize the coolant temperature. The main function of the pump in the mould temperature controller is to push the coolant to flow. When the pump pressure rises, the flow rate decreases; when the flow rate increases, the pump pressure decreases. We can see the maximum flow rate and maximum pressure values on the mould temperature controller specification, but we have to note that the two conditions never exist simultaneously. We can see the mould temperature controller pressure is inversely proportional to the flow in the figure below (Fig. 4).

## Choosing a Right Mold Temperature Controller with the Help of Injection Molding Simulation

Users can obtain the flow rate and pressure difference of every cooling channel through Moldex3D’s cooling channel analysis. The total flow rate of the cooling channels is the flow the mould temperature controller has to provide. The maximum pressure in the cooling channel is the minimum pressure the mould temperature controller has to provide. Users can enter point coordinates of the total flow rate and maximum pressure differences in the line graph. If the coordinate point is below the line, it means the mould temperature controller is able to provide enough flow rate and pressure. If the coordinate point is above the line, it means the mould temperature controller is not able to provide enough flow rate and pressure (Fig. 5). The latest version of Moldex3D, R17, is now able to provide the data of maximum pressure drop, total flow rate, and heat dissipation. Users can evaluate the mould temperature controller’s performance by adopting the pump performance curve.