Is wood quality still relevant?
Planting forests is a long term commitment. Choosing the right trees and management regime requires good site knowledge and a long term perspective about the future value of wood. It also requires a better understanding of what constitutes quality from a consumer’s perspective. Only a small premium is paid for higher quality logs in the current market, with maximum returns achieved through increasing log volume. The recent market domination by China has also blurred traditional quality criteria accepted by local wood processors, making this an opportune time to reassess just how important wood quality is for our major markets now and into the future. Read more...
Ultrasonics for Check Detection
In appearance manufacturing checks in wood cause significant issues. These checks may be on the surface, at the ends of boards or, even worse, hidden inside boards such that they may become exposed during planing or profiling after considerable manufacturing cost has been incurred. For fingerjointed board products one bad shook which reveals checking during manufacturing will result in the whole board being rejected....read more
Through a research relationship developed between Airstar Corporation, a US based company specialising in non contact ultrasonics, and Solid Wood Innovation, the technology to use ultrasonics for internal check detection has been developed, trialled, and permanently installed in two NZ manufacturing companies. The systems, which are relatively low cost (around $80k) are used to scan shook as they enter a fingerjointing line and significant reductions in reject rates in final board product has resulted.
Drying collapse and end check detection using ultrasonics has also been commercially deployed in Australia and is proving highly successful in ensuring product quality is maintained.
Other applications for ultrasonics are being explored by Solid Wood Innovation and a test facility has been established in Napier by Wooden It Ltd (in association with Airstar). As well as internal check detection at other stages in processing, the testing of finger joint integrity and grain mapping are also being investigated.
Optimising Structural Lumber Production in Processing Radiata Pine
Radiata pine grown under typical structural regimes produces a mix of structural and non structural lumber when processed. The central ‘core’ of the log is of lower stiffness and is least likely to produce structural grades (MSG 8). The tree to tree variability in stiffness is also large and hence structural lumber producers need to make the most from a resource that is of marginal stiffness and very variable log to log.
To ensure that structural lumber is only cut from positions in the log that will meet the structural grade requirements when dried and tested, a Cant Optimisation technology has been developed by Solid Wood Innovation (SWI). It uses pencil X-ray and acoustic technology, applied after the ‘wing’ boards are removed from the log and a cant is produced, to do two things: (1) determine the size of the low stiffness core where structural lumber cannot and should not be cut and (2) the location of the pith around which the low stiffness zone sits. The technology tells the processor where to position the saw pattern, from which parts of the cant to saw structural lumber and from which parts to cut lumber where structural properties are not important, e.g. industrial uses. Hence, cant by cant, sawing patterns are altered so that the manufacture of structural lumber that ultimately will pass grade is maximised (see the diagram below.) Typically the yield of structural lumber can be increased by 1 to 2 % and the separation of structural and non structural made much cleaner.
A typical cant is shown below. Operational data using an Australian resource is shown in the tables and demonstrates the large variability in both the size of the low stiffness zone and its position.
|Width of Low Stiffness Zone
||Pitch Offset (from centre)
||Off set = 0
|Low stiffness zone 0-50mm
||Off set <5mm
|Low stiffness zone 50-87mm
||Off set 5-10mm
|Low stiffness zone 87-100mm
||Off set 10-20mm
|Low stiffness zone >100mm
||Off set >20mm
The Cant Opti Technology was developed in NZ by Solid Wood Innovation and component parts are manufactured by GNS Sciences and Calibre Ltd, both NZ companies. The technology has application in NZ, Australia and the Southern USA where ‘variable’ stiffness forest resource is grown.
Understanding the internal properties of logs is key to efficient processing of radiata pine. Whilst full x-ray scanning of logs may be the ‘Gold Standard’ smaller processing companies in NZ can use the Cant Opti with minimal changes to their existing operations.
Source: Solid Wood Innovation