The effect of log heating temperature on the peeling process and veneer quality: beech, birch, and spruce case studies

Abstract

Heating green-wood prior to peeling is necessary to improve both peeling process and quality of veneer. This study investigates optimum heating temperatures by soaking of beech, birch and spruce. Experiments have studied the influence of heating temperatures from 20 to 80 C on thickness deviations and veneer lathe checking using a pneumatic rugosimeter and image analysis of opening checks with the SMOF device (Système de Mesure de l’Ouverture des Fissures). Conclusions account for reduced heating temperatures compared to the temperatures currently in-use in the industry. Already at 50 C, positive effects of heating ensure efficient peeling process. Low temperatures produce veneers with deeper and more spaced checks than high temperatures when checks are closer and less deep, becoming even unpredictable especially in case of spruce. These results establish the SMOF as an essential non-destructive control device to control the quality of the veneer produced at research level.