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Graphic element Research > Growth > Research projects > Previous projects > Industrial Processes > Laser-based automation optimises sawmill fields
Graphic element Laser-based automation optimises sawmill fields
     
 
Sawmills consume more than 50% of the timber grown in southern Europe's forests. However, difficulties in optimising cutting strategies for the non-uniform natural logs result in significant levels of wastage. In Brite/Euram project 5056, sawyers from France, Spain and Portugal joined specialist engineering company Ciris to develop an automation system that would improve operating economy and help to safeguard stocks of this valuable resource.
 

Many European sawmills employ remotely controlled log chariots to cut hardwood and softwood trunks into shape for a variety of end products. Manual control of such equipment is a demanding occupation, involving careful overall surveillance and selection of the most appropriate cutting patterns.

Even for experienced operators, it is sometimes difficult to take full account of the form and quality of a log in deciding how to achieve the highest yield. Consequently, waste levels run at an estimated 5% to 10%. As raw materials constitute 50% to 70% of a mill's overall costs, any improvements in this area can have a dramatic impact on the bottom-line.

Need for automation

In the past, various efforts have been made to automate the process, using scanners based on light barriers or cameras to determine the log shape and select a preferred position for the initial saw-cut. So far, these have met with only limited success.

Project 5056 was therefore launched in July 1996, with the objective of creating a more effective solution. The consortium brought together six saw milling SMEs and Ciris Engineering, a specialist in process design and system installation for primary and secondary wood processing. EC funding supported a two-year programme, in which the group explored the use of laser triangulation as the measuring technique. They also developed and tested new control software to translate the readings into optimised application-specific cutting strategies.

The differing requirements of the partner mills reflect a broad cross-section of industry needs. Etablissement Darré from southern France, for example, is mainly active in hardwood milling - especially as a producer of railway sleepers. These have a particularly complex shape, and must be cut so that wane defects are minimised on the rail-bearing face. Spanish company Maderas Gallastegui, on the other hand, handles pine balks, typically ranging in diameter from 25 cm to 80 cm, which pose a different set of problems.

In fact, Castellegui had already participated in an earlier EC project under the CRAFT (Cooperative Research Action For Technology) programme. It was thus able to bring valuable know-how related to the treatment of resinous woods.

Consistent high accuracy

Ciris - which has more than twenty years of timber industry experience spanning Europe, North and South America - proceeded to develop a prototype laser scanning system. This comprises a series of laser sensors mounted at 30 cm intervals above the loading cradle of the chariot.

Initial introduction of a log remains a manual procedure. The log is then advanced to bring it to the sawing position. During this process, the sensors take measurements at each centimetre along the full length of the balk. The resultant readings are downloaded to a PC, with a total of 30,000 reference points per linear meter producing much more highly detailed digital images than had previously been possible.

Data processing is completed in less than one second, determining the location of the critical first cut and adjusting the chariot settings without any delay in throughput. This cut reveals the so-called 'minimum opening face', which corresponds to the smallest width considered acceptable as a starting point. In contrast to traditional practice, each log is treated with the same high degree of accuracy throughout the working day - so such decisions are not affected by human fallibility.

The balk then is rotated through 180° and rescanned to determine the position of the second parallel cut. The software provides graphical displays of the profile, together with the measured cross section at various points. In this way, it is possible to decide how many products of given dimensions can be produced, indicating the most economical strategy for subsequent cutting. The log optimiser measures, calculates the best pattern, displays results on a screen and sends requirements to the carriag settings thus resulting in the achievement of higher recovery factors and better productivity.

Advantage for SMEs

The automation system has now completed 2 years of extensive trials in partner mills, and is now being marketed under the brand-name 'Oscar'. Its fully modular design means that it is adaptable to retrofit virtually all sawmills where log chariots are used, without necessitating extensive modification. An important advantage for European SMEs is that the EC's financial backing of the development programme will permit commercial introduction at a significantly lower price that that of competitive tools now emerging in the USA.

Cordis RCN: 42067
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