Relaxed mould making with stress-relieved HASCO steel
Developing and producing high-quality, high-performance moulds for plastic injection moulding is a complex process. With its products and services, HASCO, the Lüdenscheid-based standard mould component manufacturer, enables its customers to configure their processes in simple, flexible, and cost-optimized methods when possible. The company attaches particular importance to achieving consistently high and reliable quality in the standard components it produces. Alongside a large number of other criteria, reducing the inherent stress in the materials used is a key quality factor for all HASCO plate products.
Consistent stress reduction
When steel is produced and processed, stresses are automatically introduced into the material. This cannot be completely avoided. If these stresses are not consistently reduced through various methods and measures, they can lead to warpage after machining. Stressed processed plates are then of no use to the mould builder, and costs and delays will be incurred. HASCO minimizes this risk of warpage over the length of the entire value-added process – from the production of the steel at the supplier’s works to the processing of the plates at HASCO, then right through to the provision of support for its customers in achieving the optimum design of mould.
Stress-reduced right from the start
At the steelworks, the steel used by HASCO for manufacturing plates is first produced by uphill casting and then formed to the desired dimensions by open die forging or rolling. Stresses develop in the steel as a result of heating, cooling, and processing. To achieve a clear reduction in these stresses, HASCO has an agreement with the steel producers and suppliers that they should incorporate an additional production stage, namely stress relief annealing. The material is slowly heated to 550 to 650°C in an annealing furnace and kept at this temperature for up to two hours according to its size, which considerably reduces the stresses that have developed. Following this, the steel is cooled down gradually in order to prevent the build-up of new stresses.
Gentle separation and machining
The steel produced in line with HASCO’s requirements is delivered in big slabs, to begin with. These have to be divided into smaller-sized plates for further processing. HASCO employs a high-performance, automated sawing technology for this. The gentle separation process with a precision circular saw minimizes the amount of stress introduced into the material’s edge structure through continuous cooling of the saw blade and the material, among other measures.
During the subsequent milling operation too, the company not only ensures that convincing surface results are achieved in the typical HASCO quality but also pays further attention to keeping stress to a minimum. A completely homogeneous structure is achieved by removing the rolling or forging skin from the unfinished slabs absolutely uniformly on both sides, using consistently sharp milling and cutting tools to avoid surface heating. The careful clamping of the plates with a specially developed clamping fixture additionally contributes towards further minimizing the inherent stress in the material. At the end of the HASCO production process, low-stress standard components are obtained with a minimized risk of warpage for the customers.
Support for mould makers
HASCO has been dealing intensively with the subject of stress reduction for many years. The company has acquired comprehensive experience and built up the corresponding specialist knowledge, which it passes on to mould makers and designers. Klaus Zimmermann, a technical salesman at HASCO and an expert on stress reduction: “We do everything possible, over the full length of the value-added chain, to ensure that our standard components have only a low level of inherent stress, keeping the risk of warpage as low as possible for our customers. In addition to this, we support our customers in optimizing their processes in respect of warpage too. This starts with the design of the moulded parts. Over-sized slide tracks, for example, mean that too much material has to be removed through machining. The level of inherent stress in the material then increases, as does the risk of warpage. We are pleased to advise our customers in cases such as these and support them with our experience in finding optimum solutions.”
