Wood working15.04.2010

Plywood going strong

irch plywood is being used in van linings

irch plywood is being used in van linings

The Koskisen plywood mill has for years had a strong foothold in the manufacture of both light and heavy transport equipment. The mill is known as a punctual high-quality supplier of products which are constantly developed on the customers’ terms.

Transport means are divided into heavy and light vehicles mainly based on their weight. All means of transport weighing less than 3,500 kg are light vehicles and range fromvans to horse boxes and car trailers. Heavy transport includes ships, trains, buses and coaches, rigid trucks and truck and trailer combinations.

Plywood has long been used in the floors and walls of transport vehicles. Plywood’s advantages over many other materials include its impact resistance, strength, density, machinability and versatile use. It is also an excellent stiffener in various structures. What counts most in heavy vehicles is the weight-to-strength ratio of plywood. Light vehicles, on the other hand, require above all plywoods that are mechanically resistant, allow the use of different attaching mechanisms, resist moisture and insulate against sound.

A plywood’s moisture resistance is based on the bonding method used during the manufacturing process. The weather- and boil-proof phenolic resin bonding used meets the requirements set for exterior plywoods, and moisture resistance is further enhanced by a water-repellent coating that is easy to keep clean.

Products for a variety of applications

The KoskiSound sound reduction board, which has been included in the Koskisen plywood mill’s product range for years, consists of a rubber sound barrier sandwiched between plywood sheets. KoskiSound is primarily intended for insulating air-borne sound, but it also has certain structure-borne dampening properties, especially in low temperatures. This type of board is mainly used for trains, buses and ship decks.

The plywoods used for walls are relatively thin, with thicknesses ranging from 4 to 6.5 mm. The minimum floor thickness in light transport vehicles varies in general between 9 and 12 mm, in heavy vehicles it is much higher, even 30 mm or more as specified in the order.

Many variables

Plywood is also chosen for each specific vehicle based on the cargo and the required load bearing capacity. To facilitate the choice, the plywood manufacturers’ manual indicates the load capacity for each panel, the type of support needed and the panel thickness required for each span.

The Koskisen plywood mill constantly co-operates with its customers to improve the quality of its products. A panel basically comprises three technical areas: the panel itself, the coating and its thickness, and a pattern which can be varied as required. By varying the thickness and the veneer layout the plywood’s strength can be matched to the requirements of the specific application. The various coating patterns are intended to make the flooring panels less slippery and to reduce the noise level during loading. The colours, again, are largely a matter of taste, but Koskisen has preferred to stick to discreet and neat colours. Strength is the most important property required of the actual coating materials.

“We keep looking for different colours and materials and testing coating combinations.” says Plywood Industry Product Manager Riitta Ahokas.

Ahokas also says that the keys to durable floors in the heavy transport vehicle industry are the plywood’s structure and the inherent strength and span lengths. In light vehicles, the visual aspect is also a consideration.

“We have been looking for new kinds of structures and making strength calculations in the search for an optimal solution, she says.

The rolling test equipment is used to test the resistance of the coating and panel to rolling. This test consists of loading a forklift-like vehicle with different loads and moving it along the surface to be tested. The rolling test result for KoskiTrailer panels, for example, is 8000. In addition to the load resistance of the panels, coatings have been submitted to a wide variety of tests. The Taber value indicates the friction resistance of the coating and is 5000 R for the KoskiTrailer panels intended for heavy-duty flooring applications.

Success is important to everyone

Riitta Ahokas says that the situation in the plywood industry is currently good, citing competitive advantages such as the quality and flexibility of service at the Koskisen mill, and the degree to which the range of products is suited to the customers’ end uses.

“We constantly aim for the highest level of customer focus possible. For this to be profitable we need sufficiently high volumes.”

She says that the critical factors in the plywood business are having the right sized panel, the right surfaces, and the right panel stiffness, and for any machining to be done accurately. Ahokas believes that Koskisen has excelled in these areas, and that the plywood mill’s flagship product, the large NewSize panel, was the final breakthrough that opened the door to the transportation equipment industry.