Wood Southern Africa and Timber Times visited Boskor Sawmill in Storms River to learn more about the adaption and automation of the sawmill’s operations since its takeover by Swartland.

Swartland purchased the Boskor Sawmill from MTO roughly three and a half years ago. At the time of the takeover, Boskor was producing structural timber in addition to custom cutting timber to size for Swartland products.

The sawmill has since been redesigned and mechanised to cater solely for the processing of timber for Swartland’s products. Other processes such as finger jointing and treating have also been eliminated.

Hugo Westraadt, operations manager at the mill, explains that the redesign of the mill simplified the layout and streamlined the production flow. The lengths of logs put through the sawmill could also be limited.

Logs are offloaded onto a step feeder by a crane before being fed into the wetmill
Logs are offloaded onto a step feeder by a crane before being fed into the wetmill

Wetmill

When Swartland took over Boskor, the wetmill had two frame saw lines and one band saw line for structural cutting patterns. Boskor now runs a through and through cutting pattern on all of its lines, explains Westraadt. This has allowed the mill to change the feeding of the logs and utilise all the machines as a primary break down line.

While this provides increased capacity for the sawmill, Westraadt explains that only two frame saw lines are run at a time. A third line is set up to take over if there is a breakdown on one of the two running lines, and a fourth line is being serviced. “This is a great position to be in on the wetmill side,” says Westraadt.

According to Westraadt, Boskor’s process is slightly different from most mills in that it uses flitches rather than squaring the timber in the wetmill before drying. The flitch can then be optimised after drying.

Boskor only cuts products required by the Swartland Manufacturing Plants. In this way, Westraadt says the sawmill does not need to hold unnecessary finished goods stock. Each flitch is therefore cut to size depending on the product it will be used for, and the dimensions cut from flitches are based on orders of finished products.

The use of flitches also allows Boskor to select the visually better quality timber for use in components where the timber will be seen, such as mouldings, and cut accordingly. Visually lower grade timber will be used for internal components in products such as doors.

“We are one of the few mills still hunting clear and semi-clear material,” says Westraadt. “The structural mills do not mind if material is not pruned, but for us that is still critical, because we demand visually attractive timber.” For this reason, Boskor works with MTO to source butt logs for clearer material. This has resulted in the need for a butt end reducer to chip away butt flare that accompany these logs.

The wetmill is run largely by a Lindex log control system, supplied by German company Lindex Tools. The system operates the log separation and conveyors and joins the sawing lines.

Lindex reorganised the separate log infeeds for the four framesaws and one bandsaw. All the regular logs are now  placed on one log deck and the logs that have to be reduced on another log deck. The logs are then run automatically through a debarker before they pass the Alfha 2D scanning system. This is a 2D scanner that scans from all four sides to determine the shape, length and volume of the log before allocating the log to a specific line based on diameter grouping. The system is pre-programmed with the information on which logs are to be fed to the various machine. The scanning system also makes it easy to identify any logs to be rejected. Logs are cut into flitches on the frame saws and band saw.

The band saw has a lower throughput than the frame saw, but is used to retrieve the highest value product to be channelled into products such as veneers and mouldings. The log is turned by the operator between each cut in order to retrieve the best quality.

After being cut, the flitches are carried along conveyor belts to be grouped and sorted according to Boskor’s four product sizes before proceeding to one of four Kalfass autostackers (one for each product) which Boskor had installed after the takeover.

These stacking machines can set down up to five layers a minute. They can produce packets with a width of 1 850 mm and height of 1 800 mm which gives a maximum total packet weight of roughly 5 tons. These can then be transported by forklift to the drying kilns.

Boskor 3
The four Kalfass autostackers in the wetmill

Drying

Timber is dried in flitch form in one of five compartment kilns. The kilns are fitted with coils inside the roof and sides with a booster coil in the middle. The fans are also programmed to automatically change air flow direction. 16 probes are inserted into each stack and are connected to the kilns’ control system to determine the moisture content of each stack. The automated system determines when the timber is dry.

Boskor places an emphasis on quality over volume in all of its production process, especially the drying. For this reason, the sawmill’s drying schedules are sometimes double those of structural timber sawmills. The 25 mm thicknesses are dried in the kilns for 80 hours while the 38 mm thicknesses are dried for between 100 and 110 hours. According to Westraadt, the normal drying time for 38 mm thicknesses of structural timber is only 40 to 45 hours.

The Swartland group requires furniture quality timber, thus drying schedules are made a lot longer and softer to ensure no defects accrue such as sugar stain, checking and warping.

Timber stacked and ready for drying
Timber stacked and ready for drying

Drymill

The dried timber is destacked one layer at a time and each board is run through an inline Wagner moisture meter.

In the drymill the flitches undergo top and bottom planing on a Yates surface planer to ensure correct size and thickness before being run through a scanner which optimises the flitch based on both value and volume.

A multi-rip machine then cuts the flitches into planks, operating at high speeds of between 120 to 140 m/min. An upgrade was done on the multi-rip to include two additional telescopic blades, allowing the machine to cut up to five different sizes per flitch. Offcuts as small as 17 mm are collected in the drymill and used to manufacture small components.

In 2013, Kallfass installed a box sorting system for Boskor with 24 boxes for dry wood. The machine is installed downstream of the edging line.

The sorting computer defines which cross-section combined with which length and amount is required for one package. The box is closed and marked as full as soon as the required amount per box has been reached. The sorting programme now automatically opens a new box for this cross-section to start the next package. The full box is automatically emptied once the chain conveyor under the sorting line has been emptied, and the goods are transported to the separator. Here the boards are separated and conveyed to the Kalfass automatic stacking line.

The operator at the stacking line receives the data from the sorting computer, and the stacking line is automatically adjusted to this dimension. Once the last layer has been stacked, the package automatically leaves the machine and is conveyed to the strapping line where it is strapped before the PE strap is laid around the package and heat-sealed.

After the package has left the stacking line, the package data is transmitted via an interface to the Swartland ERP system. Thus, the company headquarters is immediately informed about the produced quantities which they can enter in their company stock programme.

Timber being stacked on the Kalfass autostacker in the drymill
Timber being stacked on the Kalfass autostacker in the drymill

Waste handling

Boskor has also undergone upgrades in terms of waste handling. The company recently installed a Bruks Tubulator which carries waste from the drymill to the boiler house. The Tubulator is totally enclosed, providing spill free transport. It also offers low noise levels and low energy consumption.

Lindex designed and supplied an automatic storage facility for all of the sawmill’s chips and sawdust to feed the boiler house. The wet and dry fuel is combined in the fuel house where it goes through a screen to check its size. Oversized fuel is run through a small grinder before being fed back into the main supply. The mixed fuel then goes to one of three storage bunkers.

Lindex installed Vecoplan walking floors in two of the bunkers, with the third operating as an overflow. Sensors automatically determine whether a bunker is full and channels the fuel to the next bunker. From the walking floors, the material is then fed on demand to the main scraper to the boilerhouse. The whole system is fully automatic and runs without an operator.

Picture 9 - Infeed to a bunker with walking floor
The infeed bunker from Vecoplan

Final product

After being strapped and marked, timber is transported to Swartland’s Atlantis branch where the timber is made into components that are distributed to other branches for further use. Here these components will be used in the manufacturing of Swartland’s quality windows, doors, door frames and mouldings.

Swartland prides itself on being a world class manufacturing company with procedures and techniques that supersede its competition. This has resulted in the company implementing similarly superior systems in the sawmill. The result of this is that Boskor has been transformed into a sawmill with superior technology, and is likely one of the leanest mills in the country.

 

By Danielle Petterson

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.