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Pushing thin-kerf automated log processing farther
Wood-Mizer’s new SLP2 line is a systematic log processing line that uses thin-kerf technology to reimagine how narrowband blades can boost profits from logs while reducing operating costs.
A company best known for popularising their standalone mobile sawmills, Wood-Mizer has steadily been making an impact farther up into industrial wood processing for over a decade. Putting their experience with thin-kerf, low waste concepts to use in more industrial environments with breakdown headrigs and multihead resaws, among other products, their speciality has been alternative product choices that focus on maximising the advantage of thin-kerf processing – providing higher log yields at a lower operating cost.
In 2007, the company debuted their first SLP thin-kerf processing line at Ligna in Hanover, Germany. The modular line was designed to be a low-cost, low-maintenance system that installed quickly and increased profits from low-value logs. The successes achieved by the SLP line since its launch has surprised some whom initially doubted its abilities and has been successfully implemented throughout a variety of markets, especially in developing regions.
James Wong, Wood-Mizer’s Regional Manager for Asia shares, "Most countries in Asia are relying more and more on plantation timber. Normally these timbers are around 30 cm and below, therefore, it is more attractive to have some automation system to process these small logs.
As labour cost in Asia keep rising, the automated SLP2 becomes more and more attractive to potential customers. They can now cut down labour cost. In general, customers are using the SLP line to produce sawn timber for the furniture, flooring, decking and the pallet industry."
Keeping with the theme of releasing new products at Ligna, the new version of the line, the SLP2,was debuted this year in Hanover. The line processes logs that are 10-40cm in diameter and 1.2-3.6 metres in length into boards and cants as required. Designed to require as few as 2-3 workers, the line features several improvements that allow such a small crew to operate it successfully.
Roman Frontczak, Wood-Mizer’s Director of Engineering, promotes the compactness and modularity of the line as a distinct advantage. "The demands of our increasingly modern global economy require that all businesses make decisions to increase efficiency, and see how they can reduce costs in a smart way. The automated SLP2 line gives our customers an additional benefit by greatly reducing the necessary manpower as labour costs continue to rise."
SLP2 advancements were focused in these main areas - centralised controls, increases in material flow automation, comprehensive slab removal, and additional measures for dealing with odd-shaped and stressed logs.
Thin-kerf blades are the key
Although wide band and circular mills have traditionally ruled the industrial wood processing landscape, the SLP2 is designed to take advantage of the inherent advantages of the narrower cut of thin-kerf blades in order to maximise the profitability of the operating company. Marko Koscal, director of operations at a growing pallet and briquette plant in Croatia shares of their experiences with the thin-kerf recovery.
"We benefit in several ways - the narrow band saws wood with a 2mm kerf, so I get an extra board from each log. Labour costs are down since we now produce more cubic metres per worker. Productivity has increased by 2.5 times and even by three times if the diameter of the logs is about 30-40 cm."
Gone are the days when thin-kerf blades could only cut a limited range of species. Wood-Mizer’s wide range of blade brands and profiles cover the whole range of sawing applications – from knotty softwoods to dense and abrasive tropical hardwoods. SLP operators generally use Wood-Mizer’s SilverTip blade - an economy carbon steel blade designed for continuous production. For tropical hardwoods and extremely abrasive species, Wood-Mizer also manufactures premium quality Stellite® tipped RazorTip blades.
Compared with other automated lines on the market, the SLP2 is smaller and lighter. However, Wood-Mizer’s Roman Frontczak is quick to point out that this is intentional.
"Shorter log lengths require shorter conveyors which means less metal is used and the equipment is then less expensive, features a more compact layout, requires less maintenance and therefore uses less energy," he explains.
The point about less energy is key to Wood-Mizer’s efforts to decrease operating costs. The SLP2 draws less power than conventional equipment due to smaller motors required to power the thin-kerf blades.
The new SLP2 line - Overview
Although often adapted in different layouts, the basic line consists of:
Central Operator Control Station
New to the SLP2, the central operator station consolidates all line controls into one place, where machines can be started and stopped, line speed adjusted, and more. The pedestal can be placed where the main operator has the best view of the whole line, while keeping a close eye on incoming raw logs.
Log loading ramp
Logs are staged first on the ramps and then advanced automatically or manually onto the in-feed chain.
Twin Vertical Saw (TVS)
The TVS is the first saw in the line and removes two vertical sides of the log in one pass. The two offcuts drop to a cross conveyor, and the cant continues through the line. The TVS, designed to run in the SLP line, is commonly used in other lines as well. Its compactness and low cost make it a viable option for initial log breakdown in a variety of processing environments.
Computer controlled sizing provides quick and precise adjustments to the cut width. Two industrial strength 11.2 kW electrical motors power the belted blade wheels. Belted wheels are ideal for thin-kerf blades – they do not require crowning and result in less blade fatigue. The twin sawmill heads are set at an angle to the in-feed chain which reduces the initial impact on the blade as it makes contact with the timber. This lets the blade stays sharper for longer and limits damage to the blade body.
Three options of in-feed and out-feed tables are available to carry the timber through the TVS heads. Standard is a dog feed chain where the spacing intervals can be adjusted to suit the sawmiller’s standard log lengths. A flat feed option is available for timber with an already flat cut surface.
The latest feed option is a spiky chain system with spiked top rollers which add greater stability to the log as it goes through the TVS. The spiky chain feed also increases productivity due to the ability to load logs with little or no gaps between them onto the chain.
"The spiky system is a continuous spiked feed chain with overhead spiked rollers before the saw", explains Roman Frontczak. "These rollers grip the log as soon as it is loaded, which means logs can be fed butt to butt with no gaps between them. Depending on the length of logs, the spiky feed can increase productivity by 10-20%.A second factor behind the development of the spiky chain was to assist with short logs that are not straight - 'banana shaped' - as well as logs that have significant taper."
Offcut removal is handled in one of two ways, via spiral rollers that catch and then drop the offcuts to the waiting cross conveyor below, or by using the new pneumatic spiky side discs that secure and release the offcut only after it has been fully cut.
Single Horizontal Saw (SHS)
Another newly designed part of the line is the Single Horizontal Saw. Here, the third slab is cut off the bottom of the log, resulting in three-sided cant with a flat bottom. The bottom slab is removed for further processing, whilst the cant is guided by special fences and roller conveyors into clamps that pneumatically position the cant from both sides. The removal of the bottom slab eliminates the need to turn the cant before it reaches the resaw.
Multihead Resaw (HR500)
The HR500 resaw can be fitted with up to six cutting heads, depending on productivity requirements. Each head is equipped with an11kW electric motor. In its maximum configuration, this resaw will produce six pallet boards plus one slab in a single pass. The material is positioned precisely by side pneumatic clamps and top pneumatic rollers that operate together to keep the three-sided cant secure during sawing. The powered metal conveyor has an adjustable speed of up to 20m/min.
"As standard, each HR500 head has a single top roller of 200mm or 300mm diameter, which is suitable for many applications, "shares Roman Frontczak."However, for short cants with lots of tension, such as rubber wood, the heavy-duty option has two rollers for each head, one either side. This means that cants are held down onto the bed before and after the blade".
Since 2014 the HR500 features several new features and options – including computer setworks.
Offcut management conveyors
Throughout the line, cross conveyors catch offcuts and move them to centralized collection areas. Once the finished boards reach the end of the line, a green chain moves them to where they can be stacked.
Results and Applications
In summary, the SLP2 line seems well situated for new ventures and diversification of existing mills. New ventures can take advantage of the lower capital required to install and maintain the line. Existing mills can think whether they could be better utilising lower-value logs by increasing yields, and increasing capacity to diversify end products more quickly to match market demand.
Stephen Sufferin, owner of S& J Contracts in Northern Ireland shares his reasons for installing a SLP line several years ago. "In 2007 we had difficulty sourcing locally sawn pallet wood so diversification was in order. We decided to mill our own timber to guarantee supply and cut production costs."
Ed Robbins, owner of Ohio Valley Veneer from the USA also utilises three thin-kerf Wood-Mizer headrigs in his walnut production facility. His opinions are clear.
"I think that thin-kerf is definitely going to be a big part of the lumber industry in the future. The kerf is what it is going to be all about. The oversaw difference is tremendous. [But] it’s not only the kerf; it’s your electric bill, it’s your parts bill, it all comes together at one big savings."
One message is clear – thin-kerf processing is offering more and more attractive options for higher productivity and profitability than ever before, and it is a product segment to watch and to consider when looking to take advantage of new opportunities.
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The SLP2 reduces costs while increasing efficiency
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