Deep embossing of MDF by compression moulding can be used to create three dimensional surfaces on furniture components, kitchen doors for instance, and on a wide range of panelling for interior design applications. Textures up to 1 mm depth can be obtained on MDF panels of 10 mm thickness and greater textures 5 to 6 mm in depth on thicker panels which have been premachined to remove surplus material.
With the compression Moulding process using a heated die, the wood fibres in the MDF surface are first softened by heat. Sufficient pressure is then applied to the fibres into conformity with the die and the heating is continued for a short period to set the fibres in position with minimum spring back and to harden the surface ready for painting or other decorative treatment.
The dies may be cast or machined from beryllium copper alloy, chosen because of its ductility and high thermal conductivity. The die is Mounted in a heavy duty, heated platen, hydraulic press
operating at temperatures in the range 245-265°C. Pressures up to 8 N/mm2 may be required for deep mouldings. Cycle times can vary from 10 to 15 seconds for shallow embossing to several minutes for deeper Moulding. Apart from considerations of temperature, pressure and time, the rate of application of pressure insofar as it affects the heating of the fibres in advance of the die, has been found to have a major effect on the ease of embossing and the quality of the embossed panels.
Many different moulded shapes can be created in MDF with smooth or lightly textured surfaces using the compression moulding process. The high temperature of the die heat Cures the surface fibres leaving a surface ready for finishing without the need for preparatory sanding or scaling.
As an additional feature, dies can be designed to compression mould panel edges as part of the surface moulding operation subject to a minimum angle of 12° with the surface.