A NEW bottom loading furnace from Melbourne-based furnace manufacturer B&L Tetlow has been developed to fire high-tech ceramics to 1650°C with a controlled rate of temperature increase and cooling.
The new furnace includes several 1800°C molybdenum disilicide heating elements and advanced fibrous alumina insulation along with controlled air cooling in the chamber.
The new design has allowed an Australian production company to achieve a 24-hour turn around firing of "high tech" ceramic components.
Eighteen high temperature U-shaped Kanthal molybdenum disilicide heating elements are evenly spaced around the work chamber and are fully recessed to maximise access to the work area.
Air intake is controlled by a modulating butterfly valve, and air outlet controlled by a modulating flap, to achieve a precise controlled uniform heating cycle.
Air is supplied from a centrifugal blower and preheated to prevent product being damaged during the process while the "modulated" motors control both the inlet and outlet of air allowing a 24-hour turn around.
The outside surface of the furnace remains cool to the touch even when the system is operating at its maximum temperature of 1700°C.
Tis feature, which is designed to assist work safety, is made possible by a continuous supply of fan-forced air circulating between the inner chamber and the outer furnace case, along with very efficient insulation on both the hot face and inner wall.
The furnaces have been designed with dual hearths so while one hearth is being fired, the second hearth can be loaded ready for processing.
A 3-phase power controller with soft start-up timer output control and current limiting is designed for use with the molybdenum disilicide elements.
A Shimaden SR72 type R controller is designed to prevent overfiring while a Shimaden FP21 type R microprocessor-based programmer controller provides nine full operating programs (with nine segments per program).
The programs can be linked to form an 81-step master program, while the microprocessor provides a digital display of process and set values with auto tune of PID parameters.