EWS-USA - New Improved Accurate Weight-per-Unit-Area Gauge for MDF Mills

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New Improved Accurate Weight-per-Unit-Area Gauge for MDF Mills

Electronic Wood Systems (EWS) announces the installation of their new Traversing Weight-per-Unit-Area Gauge for MDF mat Density at the St. Dizier MDF Mill in Isoroy, France. For the first time, this new system compensates for the Beam-hardening effect of x-ray in the mat and more accurately reports fibre distribution. Accurate on-line monitoring will allow for savings of material, resin and press time since variations can be adjusted for quickly and with confidence of accuracy beyond current devices.

MDF production managers recognize that the distribution in the MDF mat ahead of the press must be uniform. Traversing weight-per-unit-area gauges normally detect unwanted variations. The data reported is aimed at optimal fiber distribution in the forming section. Under proper performance of this function on the forming line, fibrous material and resin will be saved and press cycle times will be minimized.

Fig. 1: Selective removal of soft X-rays depends upon the MDF mat thickness.

Electronic Wood Systems of Hameln, Germany, (EWS) has introduced a new calibration method for MDF mills to substantially increase the accuracy of weight-per-unit-area measurement (kg/m2). Matthias Fuchs, head of the EWS R&D and new products departments, explains this development: “For the first time, this development takes the unique beam-hardening effect of X-ray radiation into account. This phenomenon is independent of the density, but is influenced by the thickness of the mat.”

Non-uniform attenuation processes in the mat result in preferential depletion of X-ray. In general, X-rays in energy ranges that are more easily attenuated are referred to as “soft X-rays,” while those in ranges that are more penetrating are referred to as “hard X-rays”. Thus, beam-hardening is the process of selective removal of soft X-rays from the X-ray beam. The amount of beam hardening depends upon the wave length that the X-ray beam requires to penetrate the MDF mat.

Fig. 2: Weight-per-unit-area after pre-press Siempelkamp line, Kwangwon Lumber MDF, South Korea

The common method in the industry to calibrate weight-per-unit-area gauges is by using various panel samples with known raw density values disregards the phenomenon of beam-hardening. Because the system runs on the MDF mat, the calibration also needs to be done either (a) by using MDF mats or (b) by using a mathematical function for beam hardening.

The new, more accurate, patented calibration method of the EWS weight-per-unit-area gauge is now being employed for the first time in the industry at the St. Dizier MDF mill at Isoroy, France.

Existing EWS installations can also be upgraded to utilize this new calibration technology.