Magnetostrictive Position Sensor Increases Sawmill Productivity

The Wood-Mizer line of portable sawmills provides independent woodlot operators with a reliable, efficient means of converting logs into lumber at rates ranging from 100 to 800 board ft per hour. Known for their speed and efficiency, Wood-Mizer sawmills employ thin-kerf sawblade technology that removes less wood with each cut, maximizing the yield from each log. In fact, three logs can yield the same amount of lumber as four logs if using a conventional circular blade mill.

But reducing wasted wood per cut is only part of the Wood-Mizer story. It's also necessary to cut boards accurately, getting them as close to the minimum nominal size as possible without going under tolerance. And, the re-adjustment of the cutting thickness for different-sized lumber has to be accomplished quickly and easily. Wood-Mizer realized that any operator-intensive process of manually re-adjusting the exact cutting position for every board was incompatible with the goal of higher production.

In response, Wood-Mizer's engineering team, led by Jeff McKnight, developed a sawmill command center called Accuset2(R), which allows remote control of the mill in manual or automatic modes. One of its key features is the "auto-down mode" which allows the operator to remotely set the cutting thickness of the board. In order to ensure the most efficient operation of this feature, Wood-Mizer needed a means of dependably and accurately determining when the blade was positioned at the correct depth, ready to cut.

The solution was to install a Balluff Micropulse(R) linear position transducer on the machine. The Micropulse transducer's digital output signal provides exact saw blade position information to the Accuset2 controller. Operating with the magnetostrictive pulsed measurement sensing principle, the Micropulse transducer is mounted on the chassis of the mill and reads the location of a target magnet that tracks the position of the saw blade. Totally non-contact and wear-free, the Micropulse transducer operates reliably in dirty outdoor environments under tough conditions of shock and vibration.

Jeff McKnight, design engineer at Wood-Mizer in Indianapolis, IN, said, "We needed a reliable, rugged, yet accurate position transducer. We also wanted to reference the blade position to the sawmill log bed as well as from the last cut. The Balluff Micropulse met these challenges and then some. Their engineering team was very responsive to our OEM application. They widened their power supply spec to help meet ours, they customized the sensor's connector and they even developed a custom magnet to meet our head-to-bed tolerances. Balluff's warranty and customer service has been excellent, as well as their product availability. The Wood-Mizer/Balluff relationship has been a very productive one."

This position sensing solution from Balluff fits the straightforward design philosophy and rugged construction of Wood-Mizer's high production portable mills.

 

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