Wood Veneer Manufacturing
Veneer logs are handpicked; the biggest and best trees in the regrowth forest are selected. Selected log is sent to the veneer mill. It is further inspected and graded for its intended purpose. These logs are kept wet to minimize drying and splitting prior to slicing.
The logs are first debarked, and then cut to the desired length, which is usually between 2.4 and 3.6 meters. Log selected for sliced veneer production are sent to a flitch mill, where they are cut into sections. To maximize the potential for veneer recovery, the saw operator determines his cut by the size and type of log. The use of regrowth forest requires the use of specialise equipment as regrowth logs are small and prone to splitting at the ends. A special centre sawing systems allows the logs to be cut along the Y shaped log splits. For rotary peeling, the log is left as whole.
After cutting, the flitches are sent to soaking vats to be cooked in heated water at 50 to 90 Degrees Celsius. The duration of heating is usually between 24 and 36 hours. The cooking processes soften the timber and makes slicing easier resulting in superior finish.
After the heat treatment, the flitches are prepared for slicing. Remaining surface bark is removed and the flitch is sent to the slicer. Slicing is done in four primary systems.
- Rotary slicing or peeling predominantly used in the manufacture of structural plywood’s. The complete round log is mounted into a lathe and the veneer is peeled off.
- Longitudinal slicing, the log is cut into flitch slabs usually between 50 and 100 mm thick. The slabs are drawn under the stationary slicer blade end on and the veneer is paired off down the length of the flitch.
- Crosscut slicing, over the years, more decorative veneer has been produced by this method. It is fast and very efficient. Wastage from each flitch is minimal. In crosscutting, the flitch or full log is locked into the machine. Systems have been developed with stationary or moving knifes but the principle is the same. The knife moves across the width of the flitch at a slight angle and because of its short travel, quick cycle times are achieved with high output. As the flitch is sliced away the carriage gradually moves closer to the blade with a pressure bar controlling the knife position.
- Stay log Lathe Slicing, this technique can accommodate the quarter cut slicing, crown cut slicing, semi rotary peeling or highly decorative difficult timbers such as burls, butts, ripple and fiddle back. Because of its flexibility it can maximise the yield of these timbers and is particular suited to cutting smaller logs such as regrowth.
As the veneer leaf comes off the slicer it is stacked into bundles in the exact order of its coming out of the flitch. This is essential if the original sequence and pattern of veneer is to be maintained for panel production. Bundles are numbered and kept in order so that entire logs can be sequentially laid out as timber veneer.
After slicing, the veneer leaf is fed into a drier taking about 2-3 minutes to pass through the drying chambers, and stacked again in the same sequence as they come of the log. Moisture content is reduced to approximately 10% and during this process the veneer shrinks by about 10-12%.
The veneer is then passed in bundles to a grading station where it is separated by log number, color, grain type and grading category. The bundles are then bound and docked to remove any end splitting and marked for length and recoverable width. These dimensions are recorded and the bundles are tagged.
