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[September 2002]
Furnace and Ceramic Slurry Play Key Role in Tool Production
A specially designed furnace from Lenton Thermal Designs (Hope Valley, nr Sheffield, England) has been installed by Novarc Ltd as part of a major investment in capital equipment for the rapid production of tools and dies by sprayforming.
Oxford based Novarc is said to be the leading European specialist in sprayforming, which involves spraying molten tool steel on to a reverse replica of the required part and enables fully finished production tools to be completed with short lead times - typically 25% of that for a conventional tool.
Once a design for a part has been completed, an accurate three-dimensional model is machined from modelling board that is then filled with proprietary ceramic slurry. The slurry contained within the model is frozen and undergoes an irreversible hardening reaction.
The now frozen ceramic pattern is demoulded, then dried and cured in the Lenton furnace. This step produces a near net shape structure which is mechanically stable and will accept the metal spray without distorting. This procedure takes up to three days in total and involves close control of a wide range of temperatures from 60°C to 800°C. A 20-segment programmer allows Novarc to pre-programme the most common cycles.
In order to reduce cooling times at the end of the cycle and increase throughput, the furnace includes a rapid cooling system which can reduce temperatures from 850°C to 75°C within two hours.
The furnace chamber measures 1200mm wide x 1200mm deep x 1200mm high and is used for processing large moulds one at a time or, more commonly, batches of smaller items. Maximum loading is approximately 200kg.
ENDS