wood chips

Reasons to measure wood fibers during the production process

  1. Monitoring of the mass fractions of size fractions.
  2. Monitoring of particle production and particle processing.
  3. Quality control of raw materials.
  4. Prediction of material properties

More information about wood particle size measurement can be found in the following publications:

Burkhard Plinke, Jan Thore Benthien, Andreas Krause, Kim Christian Krause, Arne Schirp, Laura Teuber (2017): Optische Größenvermessung von Holzpartikeln für die WPC-Herstellung. Vergleich dreier Messverfahren.

Abstract: Optical size measurement of wood particles for WPC – Comparison of three methods

The production process and properties of WPC (wood-polymer composites) are strongly affected by the shape and size of the wood particles (e.g. length, diameter, the ratio of length to diameter) as well as frequency distributions of these parameters and the percentage by weight of specific mass fractions. For the time being, characterization of compounds and of particles used for the preparation of WPC is mostly insufficient and inconsistent. Suitable methods are the sieve analysis or optical measurements. Several optical measurement methods were evaluated using materials which are typical for WPC. The measurement systems FibreShape, QICPIC and additionally FibreCube were tested with wood flours with grain size varying from “very fine” to “comparatively coarse” and evaluated with respect to informational value, test duration, and applicability. All systems tested provided very similar results regarding the type of distribution and its characteristic percentiles for the particle length and a shape factor (length / width ratio) when optical resolution and weighting method were similar. However, mechanical as well as optical methods show constraints with respect to particle dispersion, measurement range and resolution. These constraints have to be considered. Optical size measurements are suitable for the characterization of particle size distributions and may be readily established in the process monitoring for quality of raw materials as well as in trade and standardization and can be included in the standard prEN15534-3.

Plinke, B., Schirp, A. und Weidenmüller, I. (2011): Methoden der Holzpartikelgrößenmessung – Von der technologischen Fragestellung zur aussagefähigen Statistik. In: 9. Holzwerk­stoff­kolloquium, S. 177-187. Institut für Holztechnologie, Dresden, 1.-2.12.2011.

Abstract: Methods of wood particle size measurement – From the technological question to informative statistics

The size distribution of wood fibres or particles as raw materials for fibreboards or particleboards is an important parameter for the production control. Size characteristics are currently measured using simple means such as sieve analysis which provides only weight fractions. However, contour details (e.g. length, width, aspect ratio of each particle) can be evaluated only by optical measurements. Today, automatic image processing methods for laboratory and on-line measurements are available which can be adapted to the material type. Shape measurements for manually separated particles together with weighted size distributions provide detailed information: E.g. the different lengths of particles from various wood species which originate from the same sieve fraction; the amount of shives and fibre bundles in MDF fibre material corresponding to the gap size in the refiner; different components (e.g. particles and fibres) in particle mixtures. The FibreShape system operated at WKI is a helpful tool for these investigations. In addition, using specific image processing procedures which were developed at WKI, it is also possible to recover and measure particle shapes in mat and board surfaces for a continuous monitoring of particle geometry in the production.

Further information concerning the measurement of wood particle size with FibreShape can be found at the Fraunhofer Institute of wood research.

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