Whether it is artificial Christmas trees for the living room, bottle tops or plastic spoons – they are all plastic parts made in the injection moulding process. Plastics are not only used in everyday situations, but also in industry. Their low weight, an ability to be easily shaped plus a high resistance to corrosion and the very attractive manufacturing costs for high quantities offer a range of benefits.
As does the DNN-5-/63 PPV buffer piston, which is used in many Festo pneumatic cylinders. It is produced in the plastic parts production in the Global Production Centre (GPC) Hassel, at the St. Ingbert site in the Saarland. Attention is also paid here to energy efficiency, which is a major issue at Festo.
How is a plastic part made?
For each previously optimised component, a corresponding injection mould, the so-called tool, is created in the toolmaking department using CAD and CAM. It consists of two tool halves and hollow spaces in between. In the case of the buffer piston, the tool has eight hollow spaces, also called cavities. Production is then done fully automatically on an injection moulding machine in cycles lasting only seconds.
Production is then done fully automatically on an injection moulding machine in cycles lasting only seconds. The polyoxymethylene granulate, or POM for short, a thermoplastic polymer, is melted in a heated injection cylinder under pressure and the viscous mass is poured into the injection mould. After a few seconds the plastic is cooled down, the tool halves open and eight finished buffer pistons fall onto the conveyor belt every 35 seconds.
Energy-efficient plastic parts production
A lot of energy is used during the production process; particularly when melting the POM granulate, temperatures of 225 degrees Celsius are required. The machines therefore have to be cooled, which requires additional energy. In order to be able to reduce energy consumption, over the past two years Festo designed a new plastic parts production, completely aimed at energy efficiency, at the GPC Hassel. Together with the company Arburg, a manufacturer of injection moulding machines, Festo took a close look at the machinery with regard to power consumption and production efficiency and optimised it.
Klaus Hilmer, head of technology development and toolmaking at Hassel: “Apart from new machinery and the conversion of existing drive concepts, the new concept also included insulating the tools and reducing waste. We can do without heat recovery, as the temperature levels can be selected so that cooling is only necessary at the height of summer.”
And that has paid off: up to 50 % of the energy can now be saved. In addition, Festo was presented the Energy Efficiency Award by Arburg for this concept on 18 March 2014.