Improved cavity mould for highly efficient plastic injection moulding process

 The main goal of a mould is to produce plastic parts for several years with very high precision, a good aesthetic aspect and a fast throughput. To reach all these characteristics, traditional technologies are exploited, such as: milling, grinding, Electrical Discharge Machining (EDM), etc. This way of working originates strong limitations for the manufacture of shapes and cooling systems that cannot be overcome with conventional technologies. The alternative, already used by several players, is Additive Manufacturing (AM) - generally known as 3D printing - with metal powder; however, this process is still based on the company’s know-how rather than on a scientific approach.

 

Challenge
The EU-supported project CAxMan developed tools, enabling Novatra to conceive better cavities of the moulds. Thanks to CAxMan tools, the cavities were produced through a hybrid approach based on AM and followed by machining, to reach high quality parts.
Mechanical and thermal simulations are performed to test both the resistance of the cavities to moulding pressure (with CNR-IMATI’s Iso-Geometric Analysis tool) and the feasibility of the 3D-printing process (with CIMNE’s process simulation tool). Inner structures are added to the parts with a dedicated tool from Fraunhofer IGD, to make them lighter without affecting the structural soundness.
As soon as the optimal production parameters are found with the tools developed by CNR-IMATI, the 3D-printing process starts. In CAxMan, this step is performed by TRONRUD. For that, laser power is applied along a specific path to melt the metal powder and to generate a thin layer. As it solidifies, new thin layers are generated, and finally the powder that was not melted is removed and the 3D-printed part is obtained.
The parts are then 3D-scanned with Trimek’s equipment and software, and machined to obtain the required shape and precision, thanks to the CAM interface developed by Missler.
The cavities produced with this approach are then integrated in a mould and tested on an injection machine, to assess the improvements achieved in the injection process.

Benefits
Thanks to the CAxMan tools, the production of mould cavities uses 10% less powder than with current AM-based techniques that do not rely on process simulations and automatic design of inner structures. Besides, the design process is more reliable and deterministic, meaning that the right amount of extra material to be 3D-printed for subtractive finishing can be determined through simulations. The design process is also 15% faster, thanks to the automatic design of inner structures and the AM-process simulations that allow the user to overcome the conventional trial-and-error approach.
These are strong advantages for Novatra, because nowadays costs of AM are still higher than those of traditional techniques. CAxMan provides a real advantage by the optimisation of the design. The reduction of extra-material (that is 3D-printed and machined at the end of the process) turns into cost saving for metal powder and less energy consumed for 3D-printing and machining; parts are also lighter.
Moreover, Novatra’s customers will benefit from a cycle time reduction for their parts of 10%, thanks to the improved cooling system, thus increasing productivity, extending the operational life of their tooling and reducing the energy required for the moulding.

Organizations involved
Partners on Caxman project