In the past, different shapes of ingots, return material and aluminium chips were melted in different furnace types according to their material. This method does not pay off for die casting foundries with very low volumes of aluminium chips or return material, so only ingots were molten down.
The new plant from ZPF is equipped with an automatic charging system and can melt up to 500 kg of raw material per hour, for eg., 250 kg of aluminium chips and 250 kg of ingots. The company says its new melting furnace technology will be premiered at the international foundry trade fair GIFA 2019 in Düsseldorf.
The production of by-products such as scrap material, runner systems and even aluminium chips are usually collected and recycled externally in most foundries, which are not melted right away for economic reasons. This results in high storage and transport costs, not forgetting the logistics involved.
“A material mix of ingots and recirculation aluminium parts was previously only possible to a limited extent because of the desired boundary parameters such as melting loss and melting rate," Sven-Olaf Sauke, R&D at ZPF notes.
"For some foundries, a pure chip furnace is uneconomic, since the metal-cutting share in the cast product is often too low." With ZPF's new technology that enables melting furnaces to simultaneously melt chips, ingots and return material while still keeping the melting loss values at an extremely low level, companies now can enjoy greater flexibility in the recycling process and new opportunities to optimise the melting process.
Sump melting furnace with chips as the main material
For an optimal constructive design of the new furnace, simulations were used during the development to assess the basic system behaviour. Moreover, power and exhaust gas measurements were carried out under foundry conditions to determine functional parameters. "The decisive factor for us was the optimum melting of the metal and the required temperature control in the furnace," explains Sauke. He adds that apart from the energy consumption, other factors that strongly influence the melting result play a role in a modern furnace system, like the quality of the raw material or the melt loss. The company then analysed the data collected and determined the parameters required for the simultaneous melting of chips and other aluminium materials. A prototype with the new technology was then introduced based on the results collected.
The dimensions of the melting furnace are (L x W x H) 575 x 380 x 445 cm with an empty weight of about 28 t, allowing for a maximum throughput of 500 kg/h. The furnace system has an automatic charging unit. The modular unit is designed for different types of material as per customer requirements.
"For the simultaneous melting of different material forms in one furnace, the first step is to determine the leading material variant," Sauke says. Sauke noted that for the prototype, aluminium chips were the main material, meaning that the furnace was designed as a heel melter. As a result, the chips can be molten down in combination with return material, return wheels and ingots. Whichever variant that is added to the chips can be selected by the operator. The one important factor is the optimum quantity ratio of chips to the secondary material to ensure optimum melting performance is achieved.
Keeping ahead with R&D
In addition to R&D projects with universities and research institutions, ZPF says it practices direct dialogues with the foundry industry to continuously further develop its melting furnace technology to achieve further optimisation potential through feedback from practical experience. "This helps us to be prepared for future challenges in melting plants. For example, the modularity of the automatic charging unit makes it possible to introduce precisely metered quantities of aluminium scrap into the furnace," adds Sauke. "This has the special feature that, depending on the sprue system, has a large or small weight-to-volume ratio and must be handled accordingly - mechanically but also in terms of melting technology."