Bulk of the industrial round wood logs is presently used for the introduction of sawn wood. Improvements in processing technologies in the sawmill sector, comprising of over 23000 units need to be focused on priority basis.
Considering the various problems involved in processing plantation grown small diameter logs the Institute has undertaken development of appropriate technologies related to production of quality sawn timber for several end use applications and for higher volume and value recovery. These efforts have yielded following results:
Layout for small and medium scale sawmills including specifications of machinery and equipment, costing etc.
Techniques for log grading, grade sawing like S-D-R technique and sawn timber grading for maximum value output.
Modifications in sawing machinery and equipment to make them suitable for processing small diameter logs at the small and medium scale sawmills that constitute about 95 per cent of total sawmills in the country.
The modified system comprises mainly of suitable attachments to existing narrow band saw machine for converting it into an initial breakdown head rig saw and an improved band re-saw with fence and feeding attachments and involves little additional cost. A double edger, simple trolleys and conveyor systems have also been developed. Prototypes of these machines and attachments were fabricated locally and are presently in operation - for demonstration and training. However, technology absorption is rather slow due mainly to unorganized and dispersed nature of the saw mill industry in the country and also lack of consumer awareness.
Detailed studies have been carried out for manufacturing quality sawn-timber from silver - oak, eucalyptus, rubber wood, and coconut/palm wood.
Introduction: A large quantity of timber used in India is not properly dried resulting into development of defects like warping, cracking, splitting or decay and insect attack in the products. Everyone connected with the wood working industry, or its use in manufactured products, is aware of the difficulties encountered in properly seasoning or removing the moisture without injury to the timber. A need for consolidated information regarding proper seasoning, based upon scientific study of the behaviour of various species at different temperatures and humidities, and under different drying processes, is keenly felt. Seasoning of wood is one of the critical processing requirements to ensure satisfactory service from manufactured wood products. To ensure that timber products maintain their shape and size and to eliminate losses through cracking, splitting and warping in service, it is essential to “season” the timber, that is, to reduce its moisture content to an average equilibrium with the atmospheric condition of the locality of use.
Purpose and scope
Wood in growing trees contains considerable quantities of water. Most of this water has to be removed in order to obtain satisfactory performance from the wood in use. Freshly felled timber contains a large quantity of moisture, in many cases roughly 100 percent based on the oven dry weight of wood, though in some light timbers the quantity of water in green condition is twice as much as the weight of wood substance ( that is, roughly 200 per cent). A well seasoned piece of wood should on the other hand contain about 10 to 12 percent moisture on an average. This should be in equilibrium with the atmospheric humidity in several parts of the country. This degree of seasoning is necessary for proper retention of shape and size of component parts for high class articles, such as cabinet work, railway carriages, panelling etc. For rough work and for outdoor uses, drying of timber, say up to 15 to 20 percent moisture content, is considered enough. This also makes preservative treatment easy and effective.
Advantages of seasoning of timber.
1. Seasoning timber is lighter and hence the transport and handling costs are reduced.
2. Seasoned timber is stronger than the green timber in most of the strength properties.
3. Timbers which are to be impregnated with preservatives have to be properly dried, if proper penetration is to be accomplished, particularly in the case of oil-tyre of preservatives.
4. Seasoned wood-work finishes and glues better than green timber. Paints and finishes last longer on seasoned timber.
5. The electrical and thermal insulation properties of wood are improved by seasoning.
Finger jointed wood
With growing use of plantation timber, maximizing the utilization of small dimension timber is becoming a requirement, not an option. A new generation of wood processing machinery, finger-jointing machine (FJM) have been developed that offer a financially viable approach to maximize wood recovery. Using FJM it is possible to efficiently turn a large proportion of wood waste materials into valuable products. Finger jointing short length sawn timber, particularly from warp prone plantation species can facilitate production of higher quality solid wood products.
Research and training facility for finger jointing was established at the Institute with the generous support from the for which BMTPC, New Delhi. The prototype FJM machine developed by BMTPC was installed at the Institute and commissioned in December 1999. During the year BMTPC provided additional funds for providing additional facilities such as Glue Applicator, Dust extractor for Finger Shaping machine, Surface cum thickness planer and developing Finger jointed products.
A study was conducted to evaluate the strength of Finger joined timbers from plantation grown species. It was found that finger jointed timbers from plantation grown species such as Eucalyptus, Silver oak and Rubber wood gave finger joint efficiency in the range of 60 - 73% of the original defect free wood of the species. In addition the finger jointed wood is found to have greater dimensional stability.
A few potential products were also developed to demonstrate the use of Finger jointed timber sections.
Glued Laminated (GLULAM) Timber
Glued laminated timber offers a means to fabricate components of any length and section from short length, small section timber without any warping or significant loss in strength/stiffness. Few articles such as glued laminated beam, door and window frames, shutters, cot and table, using finger jointed plantation timber in combination with glued laminating techniques were made during the year and are under observation and testing.