Calibration Technique for the Drum Style Chip Thickness Classifier, Technical Information Paper TIP 0602-03 (2005) WITHDRAWN

The drum style chip thickness classifier* is a commonly used machine to describe the size distribution of wood chips destined for consumption in the pulp and paper industry. A wood sample of about 3 kilograms is placed inside a drum containing fixed and movable bars. The movable bars open to desired gaps dependent upon the number of revolutions a stepper motor is instructed to turn. This document describes a preferred procedure to determine the number of revolutions the stepper motor should be instructed to turn so the classifier will accurately separate wood chips at a set of defined sizes.

The objectives are:

• Identify machines that are in need of repair due to wear on drum components,

• Provide a calibration technique that can be used by various operators so they will achieve like results,

• Provide a calibration technique that can be used on various classifiers so they will achieve like results, and

• Lessen the difference seen among different classifiers that classify similar material.

In addition to calibration of the mechanical aspect of the classifier, other factors also affect accuracy and repeatability, including the timing settings (floor, slope and threshold), and the version of installed software. The objective of establishing uniformity of chip segregation among different machines may not be achieved if these factors are different among machines. This procedure is designed for use with Windows based software.

Calibration is achieved by using a set of calibration chips of defined dimensions and by adjusting the gaps between bars until the calibration chips are retained or passed through the bar gaps at defined success rate.