Stage 1: CHIPPING OF WOOD Logs of eucalyptus, casuarina and acacia firewood are stripped of their bark. A drum chipper reduces the logs into even shaped chips of about 25x25 mm, which are stored in a silo.
To refine them for processing, quantities of chips are placed on a vibrating screen to remove bits of bark, dirt, dust etc. If required, they are soaked in water to increase moisture content and improve the quality of fibre.
They are passed through a vibrating chute and a metal detector drum to remove all traces of metal contaminants. A blower sends all the dust, bark, metal particles etc., from the screen to a dust silo pneumatically.
Stage 2: DEFIBRATING, GLUEING AND DRYING The chips are ‘digested’ in a defibrator for about 4 minutes under pressure (about 8 bar) in saturated steam. Fed into the defibering discs, they are injected with urea formaldehyde resin and other additives through a blow line system into the fibre coming out from the defibrator.
Before defibration, the chips are coated with molten paraffin wax. The glued fibres are simultaneously dried and pneumatically transported by hot air through a dryer ducting system to a cyclone separator, which takes out any defective fibres, and finally, to a scale where they are weighed.
Stage 3: MAT FORMING AND PROCESSING The dry fibres are conveyed to the mat forming system. Here they drop down to a mat former belt, where distribution arms spread the falling fibres into a uniformly even mat.
The thickness of this ‘scalped’ mat will depend upon the thickness of board to be produced. It is run through a series of heavy rollers in a pre-press to compress the mat to about 1/3 thickness. The pre-pressed mat is then passed through a metal detector.
Thereafter, edge-trimming saws trim the edges, while cross-cut saws size the mat to the required lengths of board. The fibres not formed into mats are sucked out by vacuum boxes and recycled.
The mat passes through a series of conveyors to a mat stacker, from where it is fed into the hot press. The hot press allows up to 10 mats to be pressed at a time to the specified thicknesses. Powerful hydraulic pressure and high temperature (produced by steam) make for strong and homogeneous bonding of the fibre mats.
The resulting boards are unloaded on to a conveyor to be fed out, and heat is dissipated by axial exhaust fans. Mats unsuitable for pressing are tippled to a silo for either recycling or transferring to a waste fibre bin through a blower.
Stage 4: COOLING, SANDING & TRIMMING The boards are weighed on a weighing platform, cooled to room temperature in a star cooler, and then stacked on a platform.
Each stack of boards is taken by forklift truck to a roller conveyor, and transferred one by one to a wide-belt sanding machine to be surface-finished. They are then trimmed with the help of saws to the required sizes.
Stage 5: GRADING & STORAGE The trimmed boards are inspected while on the roller conveyors, stacked by grade, and sent for either storage or lamination. The finished non-laminated boards are later despatched to various destinations by truck.
Stage 6: IMPREGNATION Base paper for lamination is unwound from a paper roll, passed through a tray filled with a special resin, and then through dryer chambers. The air in the dryer chambers is heated up to 150°C by thermic fluid circulated through coils heated to 250°C from a thermic fluid heater.
The paper is then cut to the required size and stacked on a scissor lift. The stacks of impregnated paper are then shifted to storage racks in an air-conditioned store.
Stage 7: LAMINATION Finished MDF board stacks of up to 5490 mm x 1220 mm are transferred by fork lift truck, placed first on a floor mounted stack roller conveyor, and then moved to a roller conveyor mounted on a hydraulic lifting platform.
Through an automatic paper lay-up station and knife-edge transport system, the paper and the board are precisely aligned and centered on the assembly table before being moved to a single daylight short cycle press.
If boards are to be laminated on both sides, one of the paper stacks is turned upside down and brought to the paper lay-off station.
Otherwise, the paper pallet is brought straight from the store to the loading table, where electrostatic charge causes the paper sheet to adhere to the board before pressing.
After pressing, the laminated board is edge-trimmed, cut to the required size, and sent on to the inspection and quality sorting station.
Lops and tops of short cycle plantation timber are sent to the CHIPPER and the chips are converted to WOOD FIBRE.
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The plant operation is totally automated assisted by program logic control system.
The fibres are prepressed to form fibre mats.
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These mats are then pressed under high temperature and pressure to form MEDIUM DENSITY FIBRE BOARDS of desired thicknesses.
The pressed raw boards are sanded to give a smooth and uniform surface.
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The finished boards are then stacked ready for despatch or to be sent for lamination.
Imported paper is resin impregnated and prepared for lamination.
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The boards are laminated with the resin impregnated paper in a short cycle lamination press under high temperature and pressure.
The laminated boards are trimmed to the required size.
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