Toolcraft, Georgensgmünd, Germany, has collaborated with its partner, Siemens PLM Software to additively manufacture a mould for producing plastic injection moulded components for the optical industry. The result was reportedly a mould with an optimised topology, which is not only easier to manufacture, but also significantly improves the process of producing the plastic component. The company states that the opportunities created by metal Additive Manufacturing will allow new avenues to be explored and moulds to be completely reimagined.
According to Toolcraft, the conventional tool used for plastic injection moulding comprises mould inserts, mould plates, mounting plates and standardised components. It measures around 125 x 125 x 130 mm (width x length x height) and weighs approximately 60 kg. The objective of the project was to improve the injection moulding process in terms of its cycle time, to make the unit less complex and to simplify the development process. The flexibility offered by metal Additive Manufacturing meant that the design engineer could completely reconfigure the insert and improve its topology in line with the specific loads and requirements. The result was a brand new mould which was smaller and lighter with integrated conformal cooling.
Ralf Domider, Design and Simulation Metal Laser Melting at Toolcraft, stated, “Certain surfaces had to be retained during the topology optimisation process in order to preserve the functionality of the mould. Special requirements, such as the need for both parts to fit together precisely, the position of the ejector and the connectors for the machine’s peripherals, had to be taken into account when optimising the topology.” Toolcraft reported that options for later clamping the mould for reworking in a CNC machining centre had to be considered during the design stage. In order to make full use of the technological advantages of Additive Manufacturing, functional surfaces, such as a conformal cooling channel with an optimised cross-sectional area, were integrated into the blank.
A further challenge that the company faced was the warping of components during the metal AM process. It reported that arranging the components in the best possible way and creating the necessary supports requires an understanding of the process as well as experience in preparing data for Additive Manufacturing. This reportedly also has a strong influence on component warping. With the support of integrated process simulation, this warping can be calculated efficiently which allows unwanted components or disruptions in the construction process to be avoided from the outset.
Toolcraft states that the new and improved metal additively manufactured mould has much smaller dimensions. “The original unit comprising several individual components has been reduced to a mould half. The optimised tool therefore weighs almost 50% less than its predecessor,” added Domider. The low weight means that less mechanical power is required which makes the mould easier to assemble into the injection moulding machine. Additionally, the tool is higher performing despite the shorter development period. The lower mass and the conformal cooling reduces the cycle time by 30%, while ensuring that the component quality remains the same.