Oversize assessment of dry and planed timber of the ejido Pueblo Nuevo, Durango

Abstract

Timber sawing accuracy varies depending on the working methods, the degree of maintenance and the precision of the sawing equipment, and therefore its implications in planed dry timber have not been documented. The objective of this work was to determine if the saw thickness of 7/8” (22.23 mm) guarantees the obtainment of dry and planed timber with a final size that coincides with the nominal one. A sample of 150 boards of the Pinus genus produced at the La Peña sawmill was monitored during the drying and planing processes in order to determine their sawing accuracy through statistical process control; the volume that did not reach the final nominal size was thus quantified. The total standard deviation (St) of the sawmilling process was found to be 0.85 mm, which is influenced by the fact that the saw cuts are not homogeneous within the boards, and it is difficult to obtain boards with adequate surface quality and dimensional accuracy in the planing process. The quality control procedures showed that 67.50% of the planed boards were within the limits of dimensional quality control (20.92 to 22.32 mm), and 15.83% were above the upper control limit, together representing 83.33% of the total volume with adequate final nominal dimension; while the remaining 16.67% did not reach the final nominal size in dry and planed timber because they were insufficiently thick. It is concluded that the sawing variation in this sawmill compromises up to 17% of the timber.