Timber is one of the major construction material in Sri Lanka and timber seasoning is a common practice for achieving dimensional stability. The industry uses timber for interior and exterior joinery work such as doors, windows, door and window frames and panelling. However, forming seasoning defects is a common issue which prevalent in this industry. Therefore this study is conducted to identify defects caused by seasoning for teak timber and to find out solutions. For this reason, there different kilns located in Biyagama, Horana and Kottawa, operated under different schedules were selected. The impacts of three schedules were tested using teak planks. Kiln temperature and moisture content were measured for the entire seasoning period. Cupping, twisting and end cracking were measured as defects. Moreover, prong test was also conducted to determine the stress condition of the dried wood samples. Among the selected kilns, only one was maintained under the operating parameters recommended by the kiln manufacturer. The results revealed that the kiln which was programmed to regulate temperature produced the least amount of defects. However, moisture content was not programed for any of the kilns. Therefore it can be concluded that temperature has more impacted on causing defects on timber drying in the seasoning period. Therefore it is essential to regulate the temperature as per with kiln schedule.
Keywords: Construction industry, Timber identification, Seasoning issues, Kiln drying
In recent years, due to rising raw material and labor costs, increasing attention is being devoted to improve wood sawing practices. While a high cutting rate is still among the most desired characteristics, other factors such as improved cutting accuracy and surface quality, reduced kerf losses, noise, downtime, and maintenance of the machine are becoming increasingly important. However, band sawmilling have advantages over circular saws which include higher cutting speeds lower kerf waste, and typically lower noise levels. Considering above advantages several Sri Lankan companies have now established band saw milling factories. Thus the key objectives of this study were to evaluate cutting time of band sawmills and to investigate waste generation. Three different band saws (TRAK-MET TTP 600 premium; TM, Wood-Mizer LT20; WM, and Veheran; V) which are commonly used in Sri Lanka were used to this study. Evaluation of cutting time and waste generation in different band sawmills were done with special reference to Teak timber. Results show that the fastest cutting time in WM (mean cutting time of 27s), medium cutting time in TM (mean cutting time of 60s) and the slowest cutting time in Veheran (mean cutting time of 180s). The factors such as tooth profile, setting value, sharpening frequency, status of lubrication, tensioning pressure of the blade and capacity and the condition of the machine may have affected to the fastest cutting time. According to the results of evaluation of saw dust Veheran showed the highest wastage owing to high kerf and factors such as poor lubrication, lower tensioning pressure. Moreover, cutting time negatively correlated with the lubrication and saw tension in band sawmills. Therefore, it can be concluded that proper saw mill management is necessary for reduction of timber wastage and increase the efficiency of the industry.
A large scale solid wood flooring factory is to be established in Sri Lanka. On the planning stage of this industry it was found that information on wood properties of local timbers such as Hevea brasiliensis for wood flooring are not available. Hence, the present study has been conducted to gather data on selected wood properties of Rubber wood and how the wood quality changes with growth rate of trees.Hevea brasiliensis 35 year old trees were selected from three size classes: suppressed, co-dominant and dominant. Sample disks were removed at top (80%), middle (50%) and breast height of the log length. Radial variations were also studied at percentage distances from pith to bark.Wood quality was assessed by ring specific gravity. Ring width remained more or less constant from pith towards bark with slight decrease towards the bark indicating the uniform growth rate. However no specific variation was observed in ring specific gravity. This radial variation of growth rate and specific gravity was similar in all three size classes.
Application of Rubber wood as solid wood elements for flooring was experimentally assessed by hardness to loads applied to the wood and specific gravity. The mean specific gravity of suppressed, co-dominant and dominant trees were 0.564, 0.629 and 0.631 respectively indicating that the specific gravity of Rubber wood lies within the required standard for flooring which is 0.5-0.75. In the hardness test, it was observed that all three size classes generally show a gradual increase in hardness from pith towards bark. The values of average hardness of suppressed, co dominant and dominant trees were 341 kgf, 405 kgf and 433 kgf, hence co dominant and dominant trees have hardness values above 400 kgf, the standard value for wood flooring. These results indicate that Hevea brasiliensis has wood properties which are within European standard and Indian standard for manufacture of wooden flooring.