Optimizing Lumber Production through Improved Accuracy of Side Clearance of Bandsaw Teeth and Quality Control Measures

Abstract

As log costs increases as a result of increasing demand for wood products with a corresponding poor management of forest resource it has become more critical to obtain the maximum yield of useful product from each tree in order to sustain the wood industry. This work looks at the effect of the accuracy of side clearance of band saw teeth on the surface quality of sawn lumber as well as the level of adherence to quality standards when sawing Triplochiton scleroxylon (Wawa). The results obtained from the relationship between the accuracy of side clearance of band saw teeth and surface quality of sawn lumber indicates that there is a strong linear relationship between the two parameters. That is as the standard deviation of the side clearance of the band saw teeth decreases the surface quality of the sawn lumber becomes better. The correlation coefficient and coefficient of determination values for the two variables, that is, the accuracy of side clearance of the band saw teeth and the surface quality of the sawn lumber were -0.9042 and 0.8176 respectively. These values show that about 82% of the variations of the surface quality of the sawn lumber is influenced by the standard deviation of the side clearance of the band saw teeth. A graph of the relationship between the surface quality of the sawn lumber and standard deviation shows that on the average when the standard deviation of the side clearance of the band saw teeth is 0.225mm or low the surface quality of the sawn lumber produced could be qualitatively classified as good, very good or excellent. The result also indicated that the surface quality of the sawn lumber was excellent when the standard deviation of the side clearance of the band saw teeth was 0.07mm or low and was poor or very poor when the standard deviation of the side clearance was 0.252mm or more. A statistical control chart of sampled boards from the production process of the mill used for the study indicated that the mean thickness of the sawn boards was 42.42mm. The upper and lower control limits at 1.65 standard deviation were 44.08mm and 40.76mm respectively. The result indicates that about 15% of the total boards sampled were outside the control limits of the chart. The mean thickness of the sawn lumber at the mill for the study was 42.42mm as against nominal thickness of 41.00mm. This will result in a loss of about 3.46% timber for every board sawn and a subsequent loss of about 3.46m3 for every 100m3 of sawn lumber produced. African Journal of Educational Studies in Mathematics and Sciences Vol. 5 2007: pp. 1-7