This project focuses on the affect of errors that exist in log rotation systems for optimized double length infeed (DLI) log breakdown lines common to the sawmills in North America. The potential value recovery increase that could be achieved by adjusting log turner optimizer settings and/or PLC programming, to match the actual machine centre log rotation capability, is estimated. The potential of the newest commercially available log rotation systems to improve accuracy of log rotation and thus, increase product value recovery are also estimated.
Using both analytical and experimental data, the loss in lumber value that can occurr due to errors between the desired opitmized log rotation angle and the actual rotation angle are simulated. Five log rotation systems are investigated from the theoretical “perfect” system with accurate settings and no errors down to older, poorly maintained, systems with incorrect settings and large errors in rotation performance.
The work done here provides new knowledge about the importance of using accurate values of log turner settings and/or making suitable adjustments of the log turner PLC, to select best rotation angle and minimize rotation errors. The increase in value recovery and ROI that may be achieved in a particular mill will depend on the magnitude of differences between the current values of log turner settings and their correct values and/or the quality of the adjustments of the log turner PLC. The results presented here show that in typical sawmills the optimal adjustment to log turner settings and/or PLC may increase value recovery in 0.5% - 1.5% range and a ROI over 1,250%, using $20,000 cost of determining the adjustment. Replacing older, worn out, log turning systems with the newest conventional systems may increase value recovery in 0.5% - 1.2% range and ROI in 80% - 190% range. Replacing conventional log turning systems with the newest systems utilizing advanced technologies may increase value recovery in 1.2% - 2.4% range and ROI in 100% - 240% range.
The appendendices mentioned in the report are found at this link: