Misellaneous
Gunns veneers is the largest Australian company to produce wood veneer. Twenty five and half percent of Gunns veneer output is exported overseas, with 3 million square meters being supplied to the domestic market.
Veneer logs are hand picked, the biggest and the best trees in the regrowth forest are selected. Specially trained log graders oversee the trees removal to ensure they are fallen correctly and cut to appropriate lengths. This minimises waste and ensures the timber that arrives at the mill is top quality.
Once the log is selected for veneer production and sent to the veneer mill it will be further inspected and graded for its intended purpose. Logs in the yard are kept wet to minimise drying and splitting prior to slicing.
The logs are first debarked, then cut to the desired length usually between 2.4 and 3.6 meters. If the log is intended for sliced veneer production it then goes to a flitch mill where it is cut into sections. To maximise 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 system allows the logs to be cut along the Y shaped log splits, if the log is intended for rotary peeling the log is left whole.
Once cut the flitches then go back to the soaking vats where they are cooked in heated water at temperatures between 50 to 90 degrees Celsius. The duration of heating is determined by their species, size and structure, but is usually between 24 and 36 hours. The cooking processes softens the timber and makes slicing easier resulting in a superior finish.
Once removed from the vats the flitches are prepared for slicing. Any remaining surface bark is removed and the flitch is sent to the slicer.
Flitches can be prepared for slicing in different ways. This depends on the type of slicer being used and also whether the veneer is primarily required as quarter cut or crown cut.
Veneers were not always sliced, before the industry revolution veneers where cut by hand using large frame saws and a good deal of skill. Mechanisation ushered in the development of veneer sawing machines but this was relatively wasteful as the saw removed as much wood as it produced veneer. The advent of the veneer slicers in the early 1900's revealed the true potential of timber veneer. Slicing has been refined over the decades and today there are four primary systems used.
- Rotary slicing or peeling
Predominantly used in the manufacture of structural plywoods. 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.
- Staylog 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 fiddleback. Because of its flexibility it can maximise the yield of these timbers and is particular suited to cutting smaller logs such as regrowth.
The log or flitch is locked into the machine arm which rotates on a centre axis like a lathe. with each revolution the flitch contracts the knife, which cuts across the width of the face. The veneer is sliced off in a tangential arc to the centre axis, and therefore produces veneer which is actually wider than the dimensions of the flitch it came from. This is particularly advantageous when using smaller logs. As the flitch is sliced, both the log arm and knife carriage move together to maintain balance and the correct cutting angle. In addition to being an optimum system for small regrowth logs this technique offers another important advantage over conventional slicing. The staylog lathe has the facility to manipulate the position and angle of the flitch in the slicer, thus avoiding or minimising impact of unsound or undesirable sections, or conversely taking advantage of the better sections.
As the veneer leaf comes off the slicer it is staked into bundles in exact order that it comes of the flitch. This is essential if the original sequence and pattern of veneer is to be maintained for panel production. Bundles are numbed 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, emerge and be staked again in the same sequence as they came of the log. Moisture content is reduced to approximately 10% and during this process the veneer will shrink by about 10-12%.
The veneer is the passed in bundles to a grading station were it is separated by log number, colour, 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 record and the bundles tagged. When bundles are sold they are charged on the basis of recoverable size not measurement.
Before use the veneer is generally staked and allowed to recondition and stabilise after the production operation. Then it is ready for use and conversion into layons for pressing, or for shipping interstate or overseas.
The storage and handling of veneers are critical factors in producing good quality products. The moisture content of each bundle of veneer should be checked before cutting. The moisture content of the veneer should be between 8% and 12%. During humid seasons in tropical and semi-tropical places like Queensland or even Sydney, the lack of controlled conditions in the veneering storage and handling area may see the relative humidity rising as high as 80-85%. The equilibrium moisture content of veneer will consequential be increased and may reach 15-16%. In such cases there is need to reduce the moisture content of veneer prior to pressing by redrying the veneer in a press.
Various methods of laying up veneer layons are used, each can highlight or promote the grain structure of the individual veneer layons in a different way. An important factor utilising veneer is determined by the tightside of the veneer. When veneer is sliced from the flitch, the veneer side closets to the centre of the flitch usually has more fissures and checks than the outer side. The tight side is generally smoother, less porous and gives a better surface for finishing than the loose side. Veneer should be laid tight side up where possible, and the two slip match method should be used . Bundles of veneer are usually stacked loose side to the top.
Veneer leaves can be matched in a variety of ways to achieve different grain pattern effects. But its important to always lay veneer tight side up wherever possible. the tight side can usually be determined by bending the veneer leaf along the grain. The leaf will usually bend more easily towards the tight side. Bundles of veneer leaves are generally stacked and labelled loose side to top. It is smoother and less porous, thus providing a better surface for finishing. Position the veneer so that Cathedrals and Crowns point upwards. For a balanced grain layout on table and desk tops, use Reverse Slip Match technique. Do not Book match veneers unless necessary for achieving designs such a Starburts or Reconstructed Crowns.
Three types of matching recommended are
- Slip matched
The veneer leaves are simply laid side by side so the figure pattern is repeated. this method requires centre crowns on the leaves to ensure a balanced grain pattern on the finished layon.
- Reverse Slip match
The veneer leaves are laid slip matched, except that the alternate leaves are reversed end for end. This technique is used to balance the crown in veneer leaves so that all the crowns do not appear at on end of the sheet. It os often used in horizontal veneered surfaces such as table and desk tops.
- Book Matching
The veneer leaves are folded out as if opening the centre page of a book, so that one veneer leaf is a mirror image of the next. Inherent in this method is the need for alternate tight and loose sides to be uppermost, which create some problems in finishing.
Veneers are bonded using Urea Formaldehyde or Cross-linked PVA resigns. All veneered panels must be layed with a balancing back layon, generally the same species but of lower grade, unless both sides of the panel are visible G2S (Good 2 sides) panel should be specified.
Crown cut veneer can be finished in a variety of fashion colours and finishes, due to the reactively open grain structure high quality finishing systems incorporating a sanding sealer and at least two top coats should be used.
If the veneer is to be stained, the advice of the coating manufacture should be sought to ensure top quality results. Veneered furniture and components should be sealed on all surfaces. The type of finish used should suit the end use application of the furniture. For example kitchen cabinets should have a more durable finish than bedroom furniture.
Finished furniture from crown cut veneer panels is both stylish and durable. If cared for properly it will outlast many generations of owners
As veneer are a natural timber product some furniture mellowing of the colour can be expected as natural chemicals within the wood react with the surface coating.
The integrity of the surface coating must be maintained at all times to minimise the ingress of moisture, any damage to the surface coating should be repaired and the surface protected with a quality furniture polish.
Always ensure blades and cutters are sharp and properly adjusted.
Minor dents can be removed by steaming with a clean household iron and a damp rag.
This sustainable timber veneer product is ready as a high quality product for supplying the furniture Manufactures, Cabinet Makers, Construction and Joinery Industry, Interior Designers and Architects. Veneer products give the illusion of solid timber but with a cost benefit, as well as freedom in design, and individuality with the incorporation of other timber veneers or materials.
Three distinct grain patterns are available all are suitable for Doors, Draws, Shelves, Wall Panelling, Cabinet Interiors, Desk and Table tops;
- Cathedral cut
- Swirl cut
- Flatcut
Various substrate's are available to suit the end use application of the panel, these include MDF, Particleboard, Solid core, and Plywood. The highly moisture resistant version of both MDF and Particleboard should be used in areas of high humidity, such as bathrooms, kitchens, and furniture destined for tropical climates.
The crown cut veneers are sliced from ash groups of Eucalypts and are then graded by colour and grain. Species included are Acacia melonoxylon (Blackwood), Atherosperma moschatum (Blackheart sassafras), Doryphora sassafras (Golden sassafras), Eucaltyptus delegatensis (Alpine ash), E. obliqua (Messmate), E. regnans (Mountain ash), Eucryphia lucida (Leatherwood), Nothofagus cunninghamii (Mrytle), Pinus radiata (clear and knotty),and Phyllocladus aspeniifolius (Celery top pine).
Contact Number
For further information contact Gunns Veneers at 11 Morrison Street, Hobart Tas 7000 or Telephone (002) 242277, Facsimile (002)242288.
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