Wood working02.11.2015

Scent of resin in the air at the sawmill

The scent of resin from the sawmill can be detected from far away – and it is appreciated by many of the sawmill’s visitors. The scent of resin is released into the air at the Järvelä sawmill every weekday from morning till evening; in more traditional terms, spruce is sawn three weeks a month and pine one week a month in three shifts, five days a week.

The quality of the sawn timber is determined already in the log yard, where the logs are sorted by length, diameter and quality into separate compartments. From there, the wheel loader collects the logs to be sawn according to the instructions of the production planner.

“The sawmill processes 3,000 cubic metres of logs a day, or roughly 60 truckloads; that’s the volume that Koskitukki procures for us from an area of roughly 15–20 hectares,” says the sawmill’s production manager, Jaakko Huttunen.

The sawmill operator checks the sawing pattern before sawing begins.

The sawmill operator Ville Hautoniemi checks the sawing pattern before sawing begins.

The logs are debarked before being sawn; this ensures that the chips are pure for the pulp industry, allows the shape of the log to be seen for measurement, ensures fulfilment of the ISPM standard on wooden packaging materials, and saves sawmilling blades by removing sand and other impurities along with the bark.

Koskisen Finnish sawn timber

The wheel loader loads logs onto the sawmill’s log infeed, and from there they are sorted one by one on the line, top first.

“The bark is used for heat, steam and electricity production in Koskisen’s own power plants. It is also used to heat several detached homes in Järvelä via the municipality’s district heating network,” explains Jaakko.

“The clean woodchips are delivered to the pulp mill. Finnish long-fibre spruce chips are in high demand in the pulping process,” he says.

Before the actual sawmilling operation, the logs are measured using a 3D laser scanner and, based on those results, the logs are rotated to the optimal sawing position for the first chipper-canter. This ensures that the raw material is utilised to the maximum.

Chipper-canter – circular log saw – resaw – edging saw

The opposite sides of pine log are chipping

Cants are made from logs by chipping off the opposite sides of the log and then sawing off side boards.

Although some might consider the sawing process simple, to the uninitiated it is an enigma, and it’s easy to mix up the terms, such as chipper, saw, cant and baulk. 

A round log becomes a cant when two of its sides are chipped off and at the same it is straightened using the first chipper-canter. Boards are sawn off the sides of the cant by the first circular saw. 

A baulk on its way to be milled

A baulk on its way to be milled.

The side boards continue along to the edging saw, whereas the cant is turned onto its side and the second chipper-canter makes the cant into a baulk with rounded edges. 

The system measures the baulk’s length, width and thickness and uses 3D scanning to optimise the yield of the raw material in terms of value.

“Sawn timber is five times as valuable as the next most valuable by-product, chips,” says Jaakko, illustrating the importance of yield to the sawmill.

Koskisen Finnish sawn timber is refined into boards and centre goods

The log is refined from a cant and a baulk into boards or centre goods.

After the scanning, the baulk is milled to show the profiles of the sideboards, and then the circular saw is used to separate 0–4 sideboards from the baulk and 2–6 pieces of centre goods.

All products produced on the sawmilling line are sorted by dimension (width*thickness) into their own compartments; they are not always sorted according to length. After that, the sawn timber proceeds to sticking and drying in the timber yard.

More than two cubic metres of logs are required for one cubic metre of sawn timber. That rule of thumb is continuously being honed through scanning and optimisation. At Koskisen, all parts of a log, including by-products, are made use of, from base to top.

Koskisen’s Järvelä sawmill in a nutshell

- three shifts, five days a week with a staff of roughly 30
- Processes some 60 truckloads of logs daily, with 30 truckloads of fresh sawn timber leaving the sawmill 
- annual production 315,000 m³ 
- 75% spruces and 25% pine