Canadian Forest Industries is highlighting innovations in the filing room, from new processes and techniques to new technologies, during File Week 2018 from April 30 to May 4!
For the second year in a row, our File Week coverage is serving as a hub for saw filers and sawmillers to learn best practices and find the latest information on advancements in saw filing technology.
We’re posting cutting edge content both from our archives as well as brand-new stories and product news from the BC Saw Filers Association convention that took place April 26-28 in Kamloops, B.C.
We are highlighting:
- stories from the filing room
- technical articles on saw filing automation
- equipment spotlights on the latest saw filing gear
- columns from long-time contributor and filer Trevor Shpeley, head filer Josh Penner, and Modern Engineering’s Udo Jahn
- strategies for employing the next generation of filers, and more!
Stay tuned to this landing page and our social media (#FileWeek) for the latest stories and videos during File Week 2018!
The large log, headrig mill consumes 347,000 cubic metres of logs annually from several species including western redcedar, hemlock, Douglas fir and cypress. The mill produces approximately 75 mmfbm annually and employs 135 people.
The large log mill is currently equipped with two double-cut head rigs; two shifting edgers; two gang edgers; an optimized trimmer with cut-in-two capabilities; a 56-bin J-Bar sorter; a coastal planer with auto setworks; a 46-bin planer sorter; chip and lumber barge loading facilities; and an anti-sap stain treatment dip tank.
To continue growing and adapting to the needs of its customers around the globe, Duke Point is undergoing several multi-phase capital projects, which will enable the mill to consume a wider spectrum of log sorts and species.
The management at Duke Point Sawmill and its parent company, Western Forest Products, are looking to position the mill to be able to add increased value to its lower quality fibre supply, while converting its large log, high value volumes. In other words, management is looking to optimize the various processes at the mill.
One of the more recent upgrades the mill has undergone to help improve efficiencies is the installation of a Precision Machinery CNC Guide Dresser for its filing room.
“We needed a dresser that would give us better tolerances and help with our lumber size accuracy,” explains Frank Singbeil, fileroom chargehand for Duke Point Sawmill. “We haven’t had a long relationship with Precision, but one of our other mills has an older model.”
The decision to invest in the new guide dresser has already been paying off at the predominantly old growth mill.
The standard CNC Guide Dresser from Precision Machinery is designed to have all of a mill’s guides processed in one machine with operators able to change between guide profiles and store up to 90 customized guide settings.
The unit’s ground slides are adjustable in increments down to 0.0002” so operators can fine tune guides with extreme precision in seconds. These are features of the equipment that have improved day-to-day efficiencies within Duke Point’s fileroom.
“The new Precision Machinery guide dresser has got our guide clearances to our exact specs,” Singbeil says. “We no longer have any taper in our guides. The machine saves us a lot of time, not only in the dressing time, but also the set-up time. Once we set our size, that is it. We can do 30-plus guides and sizes never change. We have large guides 20-inches long with 11-inch by six-inch pads.”
The set-up time for the machine was extremely fast. It took less than a day to get the machine into the filing room, setup and ready to go, and go through all of the necessary safety precautions.
“It was a really professional experience working with Precision,” Singbeil says. “The machine was in perfect condition, nothing was overlooked in the build.”
Since the installation of the CNC guide dresser, Duke Point has only had to overcome a few small challenges.
Of course, these issues were related to the learning curve involved in how to operate a new piece of equipment and training the necessary staff, and not with the machine itself.
“They were really helpful,” Singbeil recalls. “I just made a couple of calls and they were answered immediately with no waiting.”
Overall, Singbeil says the equipment has been an incredible addition and will significantly help increase efficiencies in the fileroom moving forward.
“The machine and service are second to none, and have exceeded our expectations,” he says.
Cut Technologies chose some of the largest, most productive sawmills in Western Canada, Quebec, and the United States to determine the tangible benefits of their chrome saw. "We've been overwhelmed with the amount of positive feedback the Cougar XX Chrome saw has received from the leading sawmills in North America. Our research and development team has truly developed a unique product that will benefit all of our customers, from 3 million board feet mills to smaller, independent operations," states Mike Weckel, VP Operations.
The saws have impressed established saw filers. Cam Weber, Miller Western Forest Products Boyle running a DDM 10 at 600fpm explains, "We reached a spot where we thought there was nothing else we could do to improve the performance of our machines, until we tried Cougar XX Chrome. One year later we're still running one third of our original trial test saws. Cougar XX Chrome saws need minimal bench work and the gullets have very little wear. We feel there's a payback in longevity and the positive results have motivated us to move our target size down."
Heiko Spreng, Filing Supervisor of Houston Forest Products a division of West Fraser Mills is another avocate of chrome saws, "we changed to chrome saws because of the excessive wear of up to .010"-.012" we were experiencing in the corners of the gullet due to sawdust spillage. Chrome saws virtually eliminate this proplem due to the anti-wear properties of chrome."
At Quebec sawmill, Barette Chapis, Jean-Francois Ouimet, Filing Supervisor noticed three main advantages of the Cougar XX Chrome saw, "Cut Tech has created a saw that reduces plate wear, reduces guide wear, and increases sawing accuracy by eliminating the wear in the gullets which caused spillage."
Rex Roe, Filing Supervisor of Weyhauser Oregan, summarizes the benefits as simply being, "guide wear, saw wear, and all around better than steel. The ridged nature of the saw allowed us to reduce the saw plate by .010 and kerf the same amount. The saws run longer and because of that they're worth the extra cost."
The convention saw more than 220 people come out to the Coast Kamloops Hotel & Conference Centre in Kamloops, B.C. to check out the latest technologies for the filing room.
The first day of the convention offered attendees a firsthand look at products like BGR Saws’ new SawControl 800V2, which offers features such as quad-view technology from four simultaneous cameras, a wide variety of saw information accesible via smartphone, and S.A.M.; the company’s unique saw blade automatic measuring software; and Williams & White’s fully programmable Auto Stretcher 36X2, which stores more than 100 saw profiles.
The second day of the convention offered attendees sessions on combustible dust, quality control, new sawmill technology, V-top saw teeth and an update on the Saw Filer Program run by Industry Training Authority B.C. (ITA).
Vince Strain, senior regional officer for WorkSafe BC, reminded attendees that all sawmill operations in the province will face at least one combustible dust management inspection in 2016. Strain also mentioned that WorkSafe’s next steps related to dust management will include expanding beyond the sawmill sector into shake and shingle, pulp mills, wood pellet and OSB plants, and finger joint and reman operations. The inspection approach will have a continued focus on dust mitigation and controls with an emphasis on audit and review.
Strain told the crowd that mill employees need to be vigilant in their efforts to minimize combustible dust hazards.
“A program is only as good as the people participating in that program,” he said. “The people that do the work know best on how to manage the issues.”
The next BC Saw Filers Convention will take place on April 28-29, 2017 in Kamloops, B.C.
Latest articles on saw filing:
Saw filers: The next generation
Saw filing 101: Washboarding
Saw filing 101: Saw tension
A cut above
In previous columns I stressed the fact that filers in different mills use different techniques to achieve the same goals and that none of them are wrong if they work. This is also the case when it comes to wheel grinds. The one thing almost all filers have in common is that none of them actually want to do one. It’s a long, dirty, tedious job and it isn’t cheap in terms of manpower and equipment.
So why do we do it at all? Well, put simply, if you have worn-out wheels then no amount of fancy benching or tricks with tension are going to keep you from fighting cracks and radically un-level saws until you bring them back into good condition. For most wheels this means grinding once or twice a year depending on the workload of the bandmill.
The first step is to measure the wheels and find out where you are starting from. The traditional method is to use a cloth tape long enough to go all the way around the wheel. You start on an edge and carefully note the measurement on the tape and then do the same for the other edge and the location of the crown. I would call the first mark “0”, the others would be plus or minus whatever they were. Next use a straight edge with a light behind it to determine if there are any hollows.
Another method is to use a Pi tape. This measures the diameter of the wheel rather than the circumference and is far more precise. When you consider that the average crown is roughly the thickness of a piece of paper, you can see the advantage to exact measuring tools. Remember that the Pi tape measures diameter so you have to divide by two to find the size of the crown. To do the actual wheel grind, most filers use a Barnhart wheel grinder which allows you to make perfectly angled grinds in controlled amounts until the wheel reaches the desired shape. The Barnhart’s barrel is squared up to the saw with the help of magnetically mounted dial indicators until the grinder tracks a perfect 90 degrees to the direction of wheel travel and on an angle that results in the desired crown.
The “crown” of the wheel is the apex of the two angles leading to the front and rear edges of the saw. The amount of desirable crown is the subject of much controversy and runs from “no crown at all” to about .012 maximum. You also want the front edge of the wheel to be about .003 larger than the rear edge to make the saw track naturally forward.
When you are ready to go, run the grinding head back and forth starting at the rear until you are grinding evenly all the way from the back to almost the front edge. (You will find a sharp drop at the front that is best left until you grind back the other way.) Then you change the angle of the Barnhart barrel and grind back towards the centre. When the edge is completely clean and the sparking is stopping at your desired crown location, stop and measure the wheel. Never stop and reverse the grinding head right at the edge and don’t try to make a crown just by stopping the grind where you want the crown to be. Both of these practices almost guarantee a hollow in the face of your wheel. Always allow the grinding head to keep moving until the sparking has ceased before heading back the other way.
If everything is how you want it, then congratulations! You’re done. If not, reassess and keep going until everything is perfect. My old head filer used to say to us whenever we would try to get away with a less than precise job, “Good for you, you now have a shiny, worn-out wheel. Start over.”
Wheel grinding isn’t easy; it takes skill and practice to do right. That is perhaps why many head filers choose to use a professional wheel-grinding service. No muss, no fuss and as long as you are clear about your expectations. If, however, you want to have total control over how your saws run and wish your filers to be as well rounded as possible, there is a lot to be said for doing the job yourself. Either way, as long as you get it done regularly, your saws will thank you.
Trevor Shpeley is the head filer for Tolko’s Kelowna division and is currently the financial secretary for the BC Saw Filers Association.
To eliminate or reduce the washboard effect on your lumber you must first determine what is causing it. The conditions that produce washboard are numerous and what works in one mill isn’t necessarily going to work in another, making the problem very difficult to diagnose and cure. Recognize also that the experts in the field are not in full agreement with each other on the specific causes and cures of washboarding, and you have all the ingredients of a difficult problem that will take careful experimentation and observation to solve.
The elevated diagonal ridges on an affected piece of lumber are often thought to be produced by a vibration of the saw teeth, perhaps as a result of skinny or “weak” tooth design. In fact, the travelling wave that causes the teeth to deflect from one side to the other in a serpentine pattern occurs in the saw body itself, although it is usually generated at the saw tips by the impact of the tooth into the cut. If you picture the contributors to washboarding occurring in an imaginary band with the least damaging forces occurring on the outside edges and the most damaging occurring in the middle, you can see why some washboard is easy to fix while other examples can be tenacious and difficult to solve. If the condition, or combination of conditions, that are causing your washboarding occur on the outside edges of the imaginary band, reducing the resonance sometimes requires a relatively small adjustment such as reducing your hook face or gullet depth by as little as 1/16 of an inch, or changing your wheel speed by five per cent. (Keep in mind that reducing your gullet capacity is possibly going to require other adjustments to your feeds and speeds to keep the saws cutting properly).
Other times you will need to be more aggressive. Reducing your hook face and gullet depth by 1/8 of an inch or more, or flattening out the bottom of your gullet will sometimes increase blade stiffness enough to help with your problem (for every 1/16 of an inch your hook angle is increased, your chance of washboard goes up by 50 per cent). Increasing the radial and tangential side-angles of your tooth a couple of degrees has been known to help as well. In extreme cases you may want to increase your plate thickness to increase the stiffness of the saw as thinner plate has a natural tendency towards washboarding, but since the next step in increasing plate thickness is usually to increase feed speeds, you can quickly lose any advantage you gain.
Another method that has long been known to dampen resonating forces in band and round saws is to switch to a variable pitch pattern. The principle being that the uneven spacing of the saw teeth, sometimes coupled with a corresponding change in gullet depth, will prevent the impact forces from multiplying and creating the damaging resonance. It’s simple in theory but in real life it can be a little more complicated. The causes of washboard are many, and in some cases your problem may be caused or exacerbated by something else entirely, such as vibration in your guide assembly or a bad bearing. The only way to really know if variable pitch will solve your problem is to try it, but since that is not without its own significant costs, it makes sense to reach for the low hanging fruit first and fix the small issues before laying out hard to come by capital on a large project.
The forces that produce washboarding are a complicated puzzle for even the most experienced filers. In some mills, a tiny change can make a huge difference while in others the path to smooth lumber can be long, frustrating and expensive. It’s always worth experimenting no matter how much trial and error it takes because washboarding costs your mill money and in most cases, improvements can be made, it just might take a while.
Trevor Shpeley is the head filer for Tolko’s Kelowna division and is currently the financial secretary for the BC Saw Filers Association.
At 51 years of age, Bruce Doroshuk is the youngest member of the saw filing staff at Tolko’s Armstrong, B.C., sawmill, and that’s a problem.
Like many skilled trades, saw filing is facing the challenge of replacing an aging workforce.
“The face of our trade is going to change enormously over the next five to 10 years,” says Doroshuk, who is the president of the B.C. Saw Filers Association. “The trend I’m seeing is that a lot of guys with many years of experience are retiring or are eligible for retirement. We’ll have to get the younger generation convinced that saw filing is an interesting and worthwhile career.
His shop is a prime example, where all eight of Doroshuk’s co-workers are over the age of 55.
With this situation in mind, the association has spent considerable time revamping its four-year saw filing apprenticeship program, which was shut down at the British Columbia Institute of Technology several years ago during the recession when a struggling industry began holding off on training apprentices.
For the past couple of years, Doroshuk has been intimately involved in updating the educational portion of the program as well as the documentation for on-the-job training, as mandated by the province’s Industry Training Authority (ITA), which oversees apprenticeship programs.
“I was on a panel of ‘subject matter experts,’ as they referred to us, or tradespeople, who were given the task of making the program current,” says Doroshuk. “And we’ve done that.”
As it stands, the program is expected to restart in the fall at Thompson Rivers University in Kamloops.
Filling the Gap
Now that sawmills have turned the corner and are increasing production to meet demand from the U.S., they’re attempting to replace some the saw filers they lost during the recession. According to Doroshuk, it’s tough to attract new recruits as well as entice experienced workers to return.
“People I know were lured away by the oil and gas industry. Some are driving trucks, making more money and telling me there’s no way they’re coming back.”
The Kootenay region is just one example, he says, of an area hurt by competition from mines in the area.
Filling that gap is automation technology, according to Mike Cloutier, president of saw manufacturer and distributor Cut Technologies, and a distributor in Canada for Vollmer saw grinders and Kahny automatic tippers. Mills that can’t train people fast enough look to run their filing rooms with fewer people, using automation in the filing room.
“A lot of mills are leaning towards filing room automation to make up for the manpower loss,” he says. “All the big forest companies in B.C. are purchasing new automated machines to fill the gap and help out the tradespeople they have left in the filing room.”
The types of machines being looked at and purchased include automated benching systems for band saws, robotic grinding systems for round saws and automated tipping systems.
As the sole agent for Germany’s Kahny Automation in North America, Cut Technologies recently introduced a new automated tipping machine for round saws, designed specifically for sawmills.
According to Cloutier, the Sawmill Kahny quickly changes over from carbide trim saws to v-tip trim saws to conventional 40-toothed gang saws and re-tips at a rate of 10 saws per hour. It also features double fluxing for first-time tipping and an alternative top program (tipping left and right tips in one setup). Further, the machine allows for up to a 35-degree hook on gang saws and up to negative five degrees on trim saws. The machine also allows for tip reduction and less grinding due to precise squaring and centring; tips need to be only 0.005 over final kerf.
On the benching side, Simmonds International offers its Automated Bench (AB) to improve filing room productivity by reducing saw performance variability through running properly benched saws (flat and evenly tensioned). This reduces target size, which can increase sawmill fibre yield.
The AB simultaneously levels and tensions the saw while measuring to .0004” across the entire area of the saw – length and width. The saw’s tire line is also accurately established throughout the entire length of the saw.
These systems may decrease the amount of handling done by saw filers, but for Doroshuk, you still need skilled personnel to operate the equipment.
“In my experience, the tools and equipment are only as good as the tradesperson operating them.
“We’ve got auto-tippers, which help, but you still need experience in the filing room, someone who knows how to manually tip,” he says.
Cloutier sees things like Vollmer grinding service centres, for sharpening saws, so mills can run 24 hours a day “lights out.”
He sees mills, instead of maintaining the grinder as its grinding saws, wanting automation, where they can load 25 to 50 saws on the robotic service centre “and walk away, so they can do other things.”
Downtime is also a major concern. “You need sharp saws and you need it done properly,” he says. “And recovering the cost of putting new machinery in the filing room is fast, compared to downtime in the middle of a shift, that can cost $1,000 a minute.”
Doroshuk says new technologies, such as monitoring programs, are allowing mills to “saw better” and work being done on the harmonics and critical speed of saw blades by FPInnovations’ Wood Products Division in Vancouver has been very
"Certain speeds are more stable,” he explains. “At a higher RPM, you reach a point where no matter what you do, you can’t get the saw to be stable, and that usually happens when you’re speeding up the machine centre and speeding up the feed.”
Speed is king these days, says Cloutier, pointing out that sawmills are looking to make their operations leaner, including the filing room.
“They’ve optimized everything in the mill and now they’re looking at the filing room and saying, ‘Look what we did in the sawmill. Now it’s time to update the filing room to keep up to production in the lumber mill.’
“Mills are all about throughput and grade,” he says. “We’re re-designing round saws to try and get an extra 50 feet per minute.”
Increasing log prices are also pushing mills to improve recovery and become smarter cutters. “As log prices continue to go up, mills are going to have to pay more attention to the filing room and look at getting new equipment so they can reduce kerf and plate size.”
Helping mills achieve those goals is the FPInnovations Wood Products Division in Vancouver, which is focused on the selection of proper saw speed, feed speed and plate thickness for circular saws.
“Most mills want to go faster or save kerf, so we provide a service to test the mill’s saws on our sawing test bench,” says Bruce Lehmann, associate research leader of sawing and machine performance. “The mill sends us the saw they want to test and a set of their guides, and in some cases, a package of the wood they cut. By doing full-scale cutting tests we determine the best feed speed and blade speed for the saw. In the case of a reducing plate thickness, we can verify that the thinner saw will cut. In many cases, the saw filers come to our lab to observe the tests, so they are convinced that the change will work before they go back to the mill.”
One of the benefits of the lab, says Lehmann, is improvement in performance, which typically saves hundreds of thousands of dollars a year, but also reduces the risk of trying something different, and that can help to ensure the project goes ahead.
The lab also provides machine alignment training and reviews. If the wood does not move in a straight line or moves while it’s being cut, then the sawing deviation will be high and there will be a high number of unscheduled saw changes, explains Lehmann. To combat this, more scanning and machine positioners are being put into use in mills. “In a sense, alignment is moving from a mechanical inspection to a calibration process, but whatever the issue, there is a lot of money being lost.”
On the theoretical research side, Lehmann says, they are developing computer simulations of circular saws and guides to monitor the movement of the saw and the wood during cutting on the production machine. “For band saws there are many systems available for monitoring blade deflection during cutting, but a similar system will not work for circular saws, so we are considering indirect measurements such as saw temperature,” he says.
“No matter what aspect of sawing we talk to the mills about, we always come back to the basics of preparing the best saws, tips and guides possible. These are the foundations for good sawing and without them none of the other work we are doing will be of much benefit.”
Increasing the profile of saw filing and creating some momentum to counteract the workforce crisis is the aim of BCSFA’s annual conference, being held April 26-17 in Prince George. Doroshuk hopes this is where the new generation of filers can rub shoulders with more experienced filers, engage in discussions and gain some valuable knowledge.
“We’re excited about our conference,” says Doroshuk, who is expecting 150 saw filers and more than 20 industry suppliers. “Our members are going to hear from a keynote speaker from senior leadership at a leading forest company.”
While the recruiting drive continues, for his part, Doroshuk remains committed to his chosen profession.
“Although it takes a certain type of individual to be a filer, I can’t say enough about the industry. I love my job and I love the challenges it presents.”
And he adds, “You can work at it into your 60s,” which is exactly what he plans to do.
Since thinner blades produce less sawdust, and therefore, more lumber from the logs, and higher feed speeds result in lower production costs, the next question posed in the saw blade optimization equation was, “How thin and how fast can we make them?”
This question has been answered through trial-and-error, but the results are generally specific to the conditions in a particular sawmill. For this reason, sawmill equipment manufacturers, saw makers and university researchers started developing an engineering model that can predict saw behaviour.
The first models for circular saws were designed for collared saws. The models worked well for predicting certain rotation speeds, called critical speeds, at which the saw has a dramatic loss of stiffness that causes it to wildly deviate when cutting.
The design rule for collared saws to avoid sawing problems is to avoid rotation speeds within 15 per cent of a critical speed. Models for guided circular saws were also developed to predict critical speeds, but the theory and the practice did not match as well as for the collared saws.
Cutting experiments at the FPInnovations Sawing Laboratory in Vancouver showed that guided saws cut very well, even if the rotation speed was at a critical speed.
There is also rotation speed for each blade at which it will start to vibrate wildly, even while idling. It is not possible to increase the rotation speed to get beyond the flutter zone, as it is called.
As a result of the uncertainty in the model regarding critical speeds and an inability to predict the onset of the flutter vibration, sawmills had to send saws to the Sawing Lab to be individually tested if a speed increase or change in plate thickness was wanted.
The cost of the change not working is significant, so these tests provided certainty that the new saws, or saw parameters, would work when implemented in the mill.
Ahmad Panah, a wood-machining scientist in Vancouver who recently completed research work for his PhD in mechanical engineering, has developed a refined model for guided circular saws that correctly predicts the onset of the flutter vibration and the good cutting performance at the critical speeds.
A set of charts and tables has been created for mill personnel to evaluate their saws.
The critical speed charts published by FPInnovations are still needed because worn and grooved arbours may create the conditions for a guided saw to perform poorly at a critical speed. A TechNote will be published that contains all the tables.
This step in refining the design guidelines for guided circular saws allows FPInnovations to bypass the step of having mills sending us saws for testing. That said, if a mill wants test run related to other aspects of the cutting process, such as tooth designs, saw deflection, sawing accuracy and horsepower, we are more than happy to accommodate them – we can do full-sized cutting at the lab up to 700 feet per minute and up to about 4,000 rpm.
If a mill wants to push the envelope, keep in mind that circular saws are like race cars, the faster they go, the more perfect everything else has to be. If the saws and the feed system are not maintained and aligned, the cuts won’t be straight and expect downtime.
Lehmann says that in addition to a flutter speed chart recently created for guided circular saws, the not-for-profit organization is currently performing research on new saw tooth inspection methods; saw temperature measurement and saw monitoring during cutting; and guide pad and lubrication.
Here’s what we learned about FPInnovation’s latest projects:
Tooth inspection methods
FPInnovations is testing out high-accuracy lasers to scan a tooth.
“We’re thinking of having this baby on the grinder,” Lehmann says. “As the tooth is being ground it’s being checked right there.”
This system would be an improvement over the old Video Tooth Inspector.
“A lot of people complained it was a bit too slow – they’d have to take the saw off, clean it really well, it wasn’t automated,” Lehmann explains.
Since many mills are short on people and time, increasing the automation for tools like this is a necessity.
Saw temp measuring and monitoring
FPInnovations has developed a prototype battery-driven, wireless sensor that can measure the temperature of a saw while it’s cutting.
“Right now it would probably just be for troubleshooting, but we’re hoping it leads to continuous monitoring of the saws and maybe use it for feed speed control,” Lehmann says. “We’ve had it for the band saws for a long time, but for circular saws we can’t get a probe to accurately measure saw deflection. There’s no physical place for it where it will survive. The temperature measurement is something that seems to work and we’ve got a nice, safe place for it underneath the guides.”
Guide pad and lubrication
The sawing research group has been looking at different guide pad designs for circular saws to improve how to take heat out of the saw.
This research is being done to assist mills that are experiencing water problems, such as flooding in basements or water shortages in cases where wells that mills run off of are running dry.
“We’re trying out some different shapes and configurations to see what we can do,” Lehmann says. “Our strategy is to get the water in contact with the saw as much as possible so the water has a better chance to take heat out of the saw. Also, we want to get the water as close to where the heat is being generated, mostly near the teeth, to take the heat out before it can distort the saw plate and reduce saw stiffness. Getting the water right onto the lands near the eye and rim, which depends on the location and design of the lub ports seems to be the critical design issue.”
Flutter speed chart
FPInnovations recently completed its flutter speed chart for guided circular saws and are introducing it to the saw filing community. The chart is based on a refined model for guided circular saws that accurately predicts the onset of flutter vibration and good cutting performance at critical speeds created by wood-machining scientist, Ahmad Panah.
“Flutter speed is the limit to arbour speed as far as saw stability goes – saws cannot be run faster. Critical speed theory was developed for collared saws and it was assumed they would also be a problem for guided saws, but this didn’t prove correct. Guided saws can cut even if they are at a first or second critical speed.” Lehmann says. “However, the critical speed charts published by FPInnovations are still needed because worn and grooved arbors may create the conditions for a guided saw to perform poorly at a critical speed.”
Sawing Douglas Fir
For many mills, the proportion of mountain pine beetle wood is decreasing and they are switching back to green wood, which can contain a lot of Douglas fir. However, Douglas fir is more difficult to cut and some mills have not been able to cut as fast or as accurately as they do with pine.
“The main problem is that Douglas fir is much more dense, so cutting forces are larger,” Lehmann says. “This also means more heat is being generated, and press rolls have to provide more force to keep the logs and cants from surging or moving sideways. The power and torque loads on motors also go up. We will be looking at these issues this year.”
As far as trends coming to filing room goes, increased automation has been a long time coming.
“Because of this, filers need to start thinking more about what their job role is,” Lehmann says. “It’s not always on the bench or waiting for a grinder to finish a saw. Maybe they need to be able to spend more time on the mill floor seeing what’s going on so they can be proactive.”
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TLA Convention & Trade Show
January 16-18, 2019
B.C. Natural Resources Forum
January 22-24, 2019
6th Annual Forest Industry and Timberlands Conference
January 24, 2019
Western Forestry Contractors' Association Conference and Trade Show
January 30-1, 2019