Since February 2012, thermostat housings molded from Ultramid® A3WG6 HRX are in use at VW. The new polyamide specialty from BASF which is now available worldwide has been developed specifically for applications requiring high hydrolysis resistance in conjunction with high strength.
The coolant control module’s cover, which is molded from the new material, must withstand demanding conditions – a pressure of several bars at a peak temperature of up to 130 °C – and exhibit minimal deformation, as this would reduce the module’s efficiency.
Compared to its all-aluminum predecessors, the housing cover molded from the polyamide specialty offers benefits in terms of both weight and cost: In contrast to the metal component, the molded plastic component does not need to be finish-machined, and the desired dimensional accuracy, especially of sealing surfaces, is easier to achieve. Supports, holders, valve seats and other functions can be integrated into the molded component without effort. In addition, the high surface quality of the plastic is important, since it counteracts abrasion by the coolant.
As with other challenging plastic components molded from Ultramid, the CAE experts at BASF provided assistance to the customer during design. Great attention was devoted to optimal positioning of the gates. This made it possible to shift the unavoidable weld lines with their reduced strength to regions of the housing that are subject to lower loads. Ensuring long-term tightness of the component under the seal and thermostat loads as well as the internal coolant pressures presented Veritas with an additional challenge. With the aid of BASF’s universal simulation tool Ultrasim it was possible to analyze the creep behavior of the component in advance and optimize design accordingly.
