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Optimized processes in sawmills
2007 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

This work was initiated in order to show the potential for Swedish sawmills to achieve higher productivity by implementation of improved process control tools in breakdown and production flows. Accessible and reliable production data are crucial information concerning the area of process control; hence the objective in this study was to create a "toolbox" of suitable tools for decision support, surveys and analyses. Modern sawmills are becoming increasingly like process industries. Process control and optimization tools in sawmills have, however, not followed the rapid development of automation and increased production speed. Each machine, monitoring system or data system is commonly viewed as a detached system rather than as part of the same process. This fact makes it difficult to access process data and monitor the performance of a sawmill and, further, to address problems at the sawmill. Hence there is an identified need to introduce and use effective methods of collecting and connecting information, analysis and evaluation, as well as methods for rapid linking of results and measures that have been decided on back to the production line. Reliable and relevant information is also vital to creating a measure of confidence that changes are indeed implemented based on facts, not merely on assumptions or prior experiences. Thus, reliable systems for collecting process data and benchmarking methods such as Overall Equipment Effectiveness must be implemented. A mobile diagnostic monitoring and analysis tool developed during the study enables detailed and simplified registration of downtime and error causes in the sawmill. An increased and optimized usage of a suitable "tool package" including benchmarking methods, simulation software and process monitoring and analysis tools creates a solid base for implementation of process control and for increased productivity. An effective and profitable sawmill must utilize its raw material and the skill of its staff effectively. Sawmill production could usefully adopt appropriate areas of process thinking and optimizing methods from the mechanical process industry. Results achieved during surveys and simulations reveal a large potential to improve equipment availability and effectiveness on the sawline. Breakdown simulations show a potential to improve volume yield by improving sorting capability and, furthermore, by handling logs as single individuals during the breakdown procedure rather than as parts in a batch. Optimal volume yield can be achieved from every log by applying optimal sawing pattern, log rotation and offsets in first and second saw.

Abstract [sv]

Moderna sågverk liknar alltmer en processindustri. Mycket stora värden flödar genom processen varje sekund. Tyvärr har inte utvecklingen av processkontroll och processtyrning inom sågverken följt med i sågverkens utveckling mot en processindustri. I ett modernt sågverk genereras enorma mängder av data som utnyttjas för att styra processen men det saknas också på de flesta sågverken en mängd data för att kunna genomföra en fullständig processtyrning. På många sågverk görs ingen kontinuerlig kontroll av processparametrar som måttnoggrannhet, felinläggning, utbyte på sågklassnivå, matningshastighet, fliskvalitet, hanteringsskador, driftstoppsfrekvens och driftstoppsorsak (alla driftstopp, även korta). Vad som definitivt saknas på de allra flesta sågverk är metoder för sammankoppling av information, utvärdering, analys och återkoppling till processen. Problemet är att man ser varje bearbetningsmaskin, mätsystem eller databehandlingssystem som fristående system i stället för en del av en process. Lundahl har i sitt arbete använt sönderdelnings- och flödessimuleringsmodeller för att analysera sågverksprocessen. Som ett sammanhållande kitt mellan dessa modeller har konceptet "Overall Equipment Efficiency" (OEE) använts. Styrkan med OEE-konceptet är att man samtidigt kan ta hänsyn till processens kapacitet och till dess kvalitet. Under arbetets gång visade det sig att värdsågverkens data beträffande stopptider var för bristfälliga för att kunna erhålla en valid flödesmodell. Som en del av projektet har därför ett datainsamlingsverktyg utvecklats. Lundahls arbete visar att moderna sönderdelnings- och flödesmodeller har en stor potential för analys och optimering av sågverksprocessen. I det flesta fall krävs dock att kvaliteten hos processinformationen förbättras. Det datainsamlingsverktyg som utvecklats inom ramen för projektet ger härvidlag möjligheter till väsentligt förbättrad informationskvalitet.

Place, publisher, year, edition, pages
Luleå: Luleå tekniska universitet, 2007. , 181 p.
Series
Licentiate thesis / Luleå University of Technology, ISSN 1402-1757 ; 2007:02
National Category
Other Mechanical Engineering
Research subject
Wood Technology
Identifiers
URN: urn:nbn:se:ltu:diva-17358Local ID: 3071dc60-ad32-11db-905c-000ea68e967bOAI: oai:DiVA.org:ltu-17358DiVA: diva2:990362
Note
Godkänd; 2007; 20070126 (ysko)Available from: 2016-09-29 Created: 2016-09-29 Last updated: 2017-11-24Bibliographically approved

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