A “clear” length of lumber, say a 2×4 or 1×8, should have no knots. That’s part of what sets it apart from lesser grades. It often has a sheen, and it should match standards for its size within two- or three-thousandths of an inch. That exactness is important for the export market and high-end buyers, so a machine that can produce such precision in a sawmill’s planer operation is worth money to the mill’s owner.
The planer needs knives sharpened with near-absolute precision for those infinitesimal tolerances. Lumber being planed passes through cutter heads that may have anywhere from 10 to 44 knives; the heads spin rapidly as wood passes through them at speeds up to 3,500 feet per minute (fpm). When the knives are sharp and within a few thousandths of an inch in height, the wood has a very smooth, even satiny, finish.
But how do mills get the knives that sharp, smooth and even? As the knives plane thousands of feet of lumber, they get dull from jointing, or are perhaps nicked by rocks, dirt and gravel. To sharpen the knives, planer mills use a machine called a cutter head grinder that grinds the knife edges back to sharpness within precise size tolerances.
That presents a tricky exercise in motion control. The device has a grinding wheel that moves up and down in relation to the cutter head and in and out to specific knives. In addition, a control system must index the cutter head to position the next knife and track the number of knives sharpened
-Kreiling, J. 2018″See how a lumber cutting machine OEM implemented motion control, connectivity and remote diagnostics for precise knife-sharpening and remote troubleshooting.” The Journal From Rockwell Automation and Our PartnerNetwork™ , Putman Media, Inc. 2018, web.
Western Integrated Systems handles the cutter head grinder’s electrical parts, while our client handles the mechanical ones,.
Our solution solution comprises an Allen-Bradley® CompactLogixTM 1769-L27ERM programmable logic controller (PLC) from Rockwell Automation along with Kinetix® 350 servo drives to control the grinding wheel’s movement. Allen-Bradley PowerFlex® 525 variable-frequency drives (VFDs) control the spinning of the grinding wheel and the cutter head knife movement across it.
Servos and VFDs are controlled over Ethernet links, which reduce wiring and allows the PLC to show more faults and errors on the display.
Side Head Grinder
• Designed and supplied position control system for with Ultra 500 servo drive and
Panelview 600 with DeviceNet.
• Designed and supplied PLC control system.
• Complete electrical design, supply and installation.