Incising is a pre-treatment mechanical process in which bespoke designed blades are inserted into the face and edge of the timber section longitudinally. By passing the sawn timber products through the machine, a consistent pattern of incisions are applied to each face of the product that then provide highways for the preservative chemical to penetrate the product in the following treatment process. The machine feed speed, incision pattern, density and depth can all be varied depending on the target market and product.
Incising as a routine technique for improving preservative penetration and retention is primarily used in the United States (Crawford et al 1999) and Canada. The techniques are also being employed to some extent in Japan for railway sleepers and South Africa for wood poles.
The techniques are employed to a much lesser extent in Europe and Australia. Incising is applied to a variety of timber species, including Western hemlock (Bramhall 1967), Douglas fir (Perrin 1978), Japanese cedar (Hattori 1957) and spruce (Schulz 1971). Railway sleepers and other square sawn timbers are incised on all four sides completely along the length of the timber. The first commercial incising machine for square timbers was built in the USA in 1915 and the first practical pole incising machine in 1920.
Incising is a relatively simple and potential cost-effective additional step in the processing of sawn or round timber that can enable wider applications of the treated timber end product.
The incising is done by rotating heads that are variable sprung loaded to cope with the variation within a timber section including different timber density and knots.
The blades make a pattern of incisions into the timber as it travels through the machine, the incising heads are synchronised to give a pattern of incisions which are closely spaced to ensure sufficient levels of penetration.
Incorporated into each head is a writhing/cleaning knife system which provides three important functions to the machine:
They clear out any build up of debris between the blades.
They act as a guide for the timber and hold it in the correct position to ensure equal depth incisions to all four faces.
They prevent tear out of timber on the faces of the post caused by the incising knives.