Problem
The large plywood lathes in use in the Pacific Northwest in the 1970s were not very efficient, often peeling logs to a core up to a foot in diameter and producing a lot of waste. With the huge old growth logs available then the mills operated at a profit. But old growth was in limited supply and the industry needed mills that were profitable with the smaller second growth "tooth picks" that would soon be all that was left in the forests. Our customer hired Alpha Omega to produce electronics and software to operate new lathes that were much more efficient.
Solution
Plywood lathe systems are made up of three main parts. The XY Charger picks up the log and moves it to the lathe. The Core Drive receives the log and spins it - this is the lathe motor. The Carriage Drive moves the knife blade carriage into the spinning log to peel the veneer. Downstream from the lathe are conveyer belts for scrap and veneer and a gate to direct lathe output onto the correct conveyer. Additional improvements included Powered Backup Rolls to prevent the smaller logs from bending away from the knife and other additions to increase speed and efficiency. We developed control software for all of these processes.
The key to improving lathe efficiency is an optical scanner system and software that allows us to calculate the largest possible cylinder within a log. The log is positioned by the Charger and delivered to the Core Drive in the proper orientation to produce the maximum amount of useable veneer. The program then drives the Core Drive and Carriage Drive to peel the log. Scrap veneer is diverted into a waste gate until the log is peeled to a cylinder. Then the useable veneer is directed into the collection line as fast as the conveyer can accept it. Meanwhile the software is scanning the next log and positioning it ready to go to the lathe.
Our initial control computers were PDP 11-23 minicomputers, but these were overpriced and under powered, and not especially reliable in the less than electronics friendly environment in the older mills. AO designed and produced a more powerful and cheaper STD-Z80 Bus microcomputer system that operated reliably through the 1980s and early 1990s. Then we switched to more powerful VME Bus machines.
Plywood mills aren't portable and are inconveniently large for installations in the back room at AO, so we designed a small simulated mill with motor driven sensors and light/switch panel arrays to allow monitoring and control of the many hundreds of control signals. A separate computer operated the simulated mill.
Later improvements included powered rollers to prevent the smaller logs from bending away from the knife and other additions to increase the speed and efficiency of the lathes.
Results
The initial systems installed in the early 1980s doubled production efficiency, producing more veneer from logs and doing it twice as fast as the old lathes. The majority of veneer produced in North America in the 1980s and 1990s was generated by AO hardware and software. Alpha Omega has continued to contribute to the improvement of veneer mills for 30 years. Modern lathes peel up to twenty logs per minute and almost none of the wood fiber is wasted. Some irregular features of logs that were once discarded as trash now increase the amount of veneer produced.
