Wood Processing

PROCESSED RUBBER WOOD

Processing of rubber wood essentially include sawing, preservative treatment and kiln drying. The quality control measures of the company starts from the raw wood ensuring its proper maturity and continues in the preservative treatment and computerized controlled seasoning process to make the timber in tune with the ambient conditions.

Processed rubber wood attributes
1. Light colour
2. Attractive grain structure
3. Good strength properties
4. Good working, machining and finishing properties
5. Good staining properties
These make the rubber wood a versatile wood.

SAWMILLING

Log sorting and barking

On arrival at the mill’s storage yard, rubber wood logs are sorted and stored according to diameter, length and end-use, etc. Sufficient quantities are stockpiled to ensure the sawmill’s continuous operation, particularly during adverse weather conditions when log extraction and supply from the forests may be adversely affected.

Debarking of logs is undertaken by mechanical debarkers at the mill site. Before the log is presented to the headrig for breakdown, it is cut to the longest permissible straight length with a cut-off saw, whereupon it is loaded onto the headsaw carriage and positioned in such a manner as to allow the operator to achieve a sawing pattern, which will result in the optimum production of sawn timber with the minimum of waste. The pattern of cut is largely determined by the dimension and condition of the log, as well as the market requirements for the widths and thicknesses of the lumber.

Sawing of the log is achieved by the use of a bandsaw or a circular saw with a second saw mounted vertically above the first in the event of sawing large diameter logs. A log carriage conveys the log through the headsaw on which the log may be clamped and turned, so as to enable it to be presented to the headsaw in order to achieve the best sawing pattern.

Following the headrig, further breakdown of slabs, flitches and cants takes place in the resaw, which enables the wood to be upgraded; thick slabs being sawn into planks and the flitches and cants sawn into planks and boards. The rough round edges of the pieces coming from the headrig and resaws are removed by either a circular saw or chipper edger so as to produce standardized widths as required.

On leaving the headrig, resaw or edger, the lumber is cut to standardized lengths, edges squared and defects removed by the use of one or more fixed or moveable trimming saws, whereupon the lumber proceeds to be sorted and graded.

The sawn and trimmed timber is sorted according to thickness, width, length, quality, grade and species depending on the market requirements; grading is a means to segregate the lumber according to the overall quality, direction of grain, presence of knots and defects, as well as general appearance, etc. To protect the sawntimber against attack from fungi and insects, as well as to inhibit the tendency of air-dried lumber to check and split, the ends may be brushed either manually or mechanically dipped in a suitably prepared chemical solution. Wax or paint is applied to the end-grain of lumber to be air-dried, either by brush or spraying, so as to act as a sealant in order to bring about a slower drying of the extremities and hence, give rise to a more uniform drying of the lumber.

Preservative Treatment

Due to the absence of heart wood – the durable and usable part of the wood – rubber wood is susceptible to the attack of fungi and insects. Immediately after felling and sawing, to improve the durability of the wood, preservative treatment with suitable preservative chemical is carried out. It is important to say that preservative treatment is meant only for improving the durability. It does not change the anatomical structure, strength, shape or any other property of wood. The structure of the vessels in rubber wood permits easy and effective preservative treatment. Rubber wood belongs to the treatability class ‘B’ and durability class III.
Being naturally non-durable rubberwood would not be economically usable without preservative treatment.
The preservation is carried out by impregnation under pressure and vacuum in cylindrical chambers. In vacuum pressure process, the timber is subjected to an initial vacuum followed by pressure treatment and a final vacuum. In the oscillating pressure and vacuum method the cycle is repeated 10 to 15 times.

Kiln Drying

Rubber Wood belongs to refractoriness to seasoning class ‘B’ of IS:1141-1993. When freshly cut, moisture content of the timber will be above 60 %. For any use, the moisture content has to be reduced to the Equilibrium Moisture Content (EMC) and this is about 12%.
This is for dimensional stability and for obtaining good machining and finishing properties. Rubber Wood contains tension wood and hence seasoning is carried out by our Kiln Dry chambers with utmost care at controlled conditions of temperature & humidity so that the drying takes place uniformly throughout the entire charge. The final moisture content will be 10-12%. The drying time is dependent on the timber thickness.