Veneer incising at the lathe, a new technology developed at Forintek, has been increasingly applied in the Canadian softwood plywood industry. The benefits include reducing veneer curl-up and spin-outs and increasing veneer recovery. However, a comprehensive study of the effect of veneer incising on veneer stress grading and LVL strength properties has not been thoroughly undertaken. In response to requests from our Forintek member mills, this report investigated the effect of veneer incising on the veneer stress grading and strength properties of spruce LVL products. Both incised veneer and non-incised veneer were peeled with blocks from same log using a Forintek mini-lathe equipped either with incisor bar or smooth roller bar. Then veneer sheets were randomly and proportionally sampled from the peeled veneer ribbon. These veneer sheets were stress wave tested and used to make LVL panels. The t-test was used to examine the significance of the differences in veneer stress wave time (equivalent to UPT) and LVL panel mean strength properties. The results showed that:
Veneer incising did not significantly affect veneer stress grading (identified by the measurement of veneer stress wave time or UPT), veneer density and veneer MOE.
Veneer incising also had no significant effect on the spruce LVL conventional hot pressing times for the core temperature to rise to 1050C and LVL compression ratio.
Further, there were no significant differences in LVL edgewise bending MOE, MOR and block shear strength parallel to grain between the non-incised and incised veneer. However, the difference in mean LVL block shear strength through-the-thickness between the non-incised veneer and incised veneer was significant. The block shear strength through-the-thickness using the incised veneer was slightly lower compared to that using the non-incised veneer using a glue spread level of 32 lbs/1000 ft2 per single glueline. A previous study showed that at higher glue spread levels normally used for LVL, 40 lbs/1000 ft2 per single glueline, the block shear strength through-the-thickness was slightly higher for the incised veneer compared to that using the non-incised veneer.