Size control of sawn timber by optical means in breakdown saw machines

The thesis investigates optical measuring and statistical data processing, and presents a method to understand and reduce sawing variation by examination of sawn timber sizes. Continuous timber size control offers improved opportunities for analysing saw machines or even individual sawblades. The thesis is illustrated with seven saw machine case studies that relate to the development of the technique. Log and cant breakdown is examined in single- and double-arbor circular saws and bandsaws. The first analysis of each saw machine is made in normal production, and the second using a controlled benchmarking test. A total of 44350 logs were sawn in the study. The behaviour of a saw machine is described using such descriptors as total, within-board and between-board standard deviations, and sawblade bend. Based on observations in benchmarking, an equation y=αeβx±R, where α and β are constants, R the process reproducibility, and x a variable that expresses sawing time and saw load, can be established for each of the saw machine descriptors. An example is the total standard deviation descriptor function s=0.21e0.58x±0.11, established for a single-arbor circular saw in a 4-piece saw set-up. The method will help a sawmill to establish descriptors and equations used to describe the behaviour of their saw machines, to baseline saw machine performance and to compare it to best practices in the industry. The descriptors may be used to establish current, short- or long-term capabilities and characteristics. The method can be used to examine various production conditions and tooling, such as effects of log size, feed speed, and sawing time. Other factors include saw speed, sawblade parameters, operation of setworks and feedworks, and effects of seasons. The results of the study show that sawblade behaviour, feedworks and work piece holding problems, and previous saw machines may be causes of large sawing variation.

Department dc:contributor.department

Department of Forest Products Technology

Grantor dc:publisher

Helsinki University of Technology

Year dc:date.issued

2001

Author dc:creator

• Vuorilehto, Jaakko

Contributors dc:contributor

• Aalto-yliopisto
• Aalto University

Language dc:language.iso

en

Repository record dc:identifier.uri

https://aaltodoc.aalto.fi/handle/123456789/2352

OAI identifier oai:identifier

oai:aaltodoc.aalto.fi:123456789/2352