Com­pact, fast, ac­cu­rate so­lu­tion

Australian Forests and Timber - - MILL OPTIMISATION -

SYN­ERGY IS de­fined as co­op­er­a­tive in­ter­ac­tion that cre­ates an en­hanced com­bined re­sult. A re­cent syn­er­gis­tic so­lu­tion was cre­ated at Stim­son Lum­ber’s op­er­a­tion at Til­lam­ook, Ore­gon, when the com­pany chose a pri­mary break­down con­fig­u­ra­tion that merged de­signs of prod­uct lines from the USNR fam­ily. The re­sult is com­pact, fast and ac­cu­rate.

The Stim­son mill at Til­lam­ook is pre­dom­i­nantly a stud mill. The pri­mary line uti­lized man­ual pro­cess­ing tech­niques, so the pri­mary goal of the project was to em­ploy more ad­vanced tech­nol­ogy to re­cover greater quan­tity and qual­ity of lum­ber.

Jeff Web­ber is vice-pres­i­dent of op­er­a­tions for Stim­son, based at its head­quar­ters in Port­land, Ore­gon. Af­ter study­ing dif­fer­ent in­stal­la­tions, dif­fer­ent ven­dors, and dif­fer­ent prod­uct mixes, he says, “At the end of the day we were con­vinced that the USNR sys­tem was the right one for us, for our log char­ac­ter­is­tics and what we wanted to do.”

Jeff ex­plained that the so­lu­tion they chose for this project in­cor­po­rates a com­pact sharp chain po­si­tion­ing in­feed sys­tem with side chip­ping heads, and cants are pro­cessed down­stream at the mill’s ex­ist­ing hor­i­zon­tal re­saw.

Po­si­tioned for ac­cu­racy

This con­fig­u­ra­tion was cho­sen be­cause it will han­dle the spe­cific char­ac­ter­is­tics of the mill’s log diet, with its proven de­sign for po­si­tion­ing ac­cu­racy and to main­tain con­trol of the log through the cut­ting tools. This is a very high piece count ma­chine, ca­pa­ble of op­er­at­ing at 600 fpm and pro­cess­ing 24 pieces per minute.

The USNR sup­ply in­cludes the log feeder, po­si­tioned at the last step of the log loader to fa­cil­i­tate pre­cise gap man­age­ment be­tween logs. Once loaded on the vee-flight chain, each log is scanned for de­fects, turned, skewed to po­si­tion, thumped on a sharp chain, and a fi­nal scan is per­formed be­fore pro­cess­ing - all within a very short dis­tance. Af­ter the first scan a re­cip­ro­cat­ing quad roll log turner ac­tu­ates the turn so­lu­tion. Then the po­si­tion­ing in­feed takes over the fi­nal log po­si­tion ad­just­ments by skew­ing the log end to end. This fea­ture of­fers a big ad­van­tage al­low­ing the line to po­si­tion for spe­cific log de­fects to achieve max­i­mum re­cov­ery.

The skew is ac­com­plished with two sets of cen­ter­ing rolls fit­ted with lin­ear po­si­tion­ing cylin­ders. One moves the front end of the log left or right, the other moves the back end left or right. Once the log is in po­si­tion the over­head press­rolls come down and thump the log onto the sharp chain. Then it is scanned again, and the sys­tem has the ca­pa­bil­ity to move the chip­ping heads to make fur­ther ad­just­ments be­fore pro­cess­ing.

The at­tributes that make this de­sign unique is that it is com­pact and sim­pler than an ex­tended length in­feed, it op­er­ates at high speeds and is ex­tremely ac­cu­rate. With this in­feed con­cept there is no tran­si­tion into the can­ter, so there is lim­ited op­por­tu­nity for the log to lose po­si­tion prior to pro­cess­ing. This de­sign will han­dle small to medium sized logs.

The op­ti­miza­tion sys­tem Stim­son se­lected is the Mil­lEx­pert plat­form with Smart TriCam lin­eal scan­ning. From the first scan it cre­ates a dense 3D model of each log. Mil­lEx­pert’s Log Turner Op­ti­mizer and Log Op­ti­mizer work to­gether for op­ti­mal turn­ing and po­si­tion­ing to achieve the most valu­able break­down so­lu­tion. Once the log is turned and skewed a sec­ond scan is per­formed to con­firm the po­si­tion of the piece, and the log op­ti­mizer fi­nal­izes the break­down so­lu­tion based on any dis­crep­ancy be­tween the op­ti­mal po­si­tion and the log’s ac­tual po­si­tion.

With the ap­pro­pri­ate log diet, these com­pact in­feed sys­tems have an ad­van­tage over tra­di­tional ex­tended length in­feed sys­tems be­cause the logs are po­si­tioned onto the sharp chain in a very short dis­tance, scanned for the break­down so­lu­tion and then pro­ceed on the same con­veyance into the cut­ting de­vices.

De­tect­ing the turn

A par­tic­u­larly valu­able fea­ture of Mil­lEx­pert log op­ti­miza­tion is the turn de­tec­tor. The turn de­tec­tor al­lows users to mon­i­tor how well the ro­ta­tion sys­tem is do­ing on ev­ery log, and pro­vides re­ports that can in­di­cate when prob­lems oc­cur. With the turn de­tec­tor fea­ture the mill per­son­nel can eas­ily mon­i­tor the per­for­mance of their po­si­tion­ing sys­tem and tune it, as re­quired. To uti­lize the turn de­tec­tor fea­ture, a sec­ond scan must be taken af­ter the log is po­si­tioned. Turn de­tec­tor re­ports on the fi­nal ro­ta­tion that was achieved.

Ex­ceed­ing ex­pec­ta­tions

Jeff Web­ber is pleased with the per­for­mance of the line. “It’s ex­ceeded our ex­pec­ta­tions. We as­sumed some re­cov­ery im­prove­ment, which is why we did the project. We did not as­sume any pro­duc­tiv­ity im­prove­ment be­cause we thought we had other con­straints in the mill. But we did get more pro­duc­tiv­ity, so that was a bonus, and our (lum­ber) qual­ity is bet­ter.”

“This is the best project I’ve ever seen in my 30-plus years. Ev­ery­thing just fell into place. It was on bud­get, it was on time, and the per­for­mance was bet­ter than ex­pected,” Jeff says.

Now, Stim­son plans to turn its at­ten­tion down­stream.

“Be­cause this ma­chine has a lot of pro­duc­tion ca­pac­ity that we’re not uti­liz­ing, we’re go­ing to work in the rest of the sawmill to fig­ure out how to tap into that ca­pac­ity.”

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