Professional spraying in industrial wood machining, especially the production of boards, is gaining in importance. This is not just because of the increasing cost of energy and raw materials, it is also because increasingly high demands for quality in the manufacture of wooden boards encourages the demand for suitable processes and possibilities, in order to apply liquids as homogeneously as possible onto prepared base materials.

A frustrating factor is that these materials vary depending on the type of board, such as medium density fibreboard (MDF), hard wood fibre building board, chipboard or oriented strand board (OSB), which in turn have an effect on the spraying.

However, the production of all these types of boards is similar. The individual fibres or shavings are transported along a large conveyor line and sprayed and moistened with release agent, water or glue. Finally, the treated base material is pressed into boards.

When manufacturing chipboard or MDF board, the gluing process is carried out differently. While the application of glue to the shavings for chipboard takes place in mixing drums, the fibres for MDF board are processed in a blowline (for wet gluing) or in a hopper (for dry gluing).

The aim here is to distribute the glue in the blow pipe as homogeneously as possible, because an uneven application of glue leads to staining on the fibreboard and therefore a decrease in quality. As the shavings and fibres are transported along the conveyor lines to the presses, they are moistened with specially designed nozzles or various additives are applied.

Here, the flat jet nozzles are used almost exclusively because of their spray features. These nozzles are used as pressure nozzles (single-substance nozzles) or two-substance nozzles. When two substance nozzles are used, a second substance (air or steam) is used as an auxiliary atomisation medium. Pressure nozzles or two-substance nozzles?

For more information, visit our website (click the “news and facts” button, then “publications”, then “nozzles for the wood industry”).