Relative kerf and sawing variation values for some hardwood sawing machines

Information on the conversion efficiency of sawing machines is important to those involved in the management, maintenance, and design of sawmills. Little information on the conversion characteristics of hardwood sawing machines has been available. This study, based on 266 studies of 6 machine types, provides an analysis of the machine characteristics of kerf width, within-board, between-board, and total sawing variations and wood loss per sawline. Machine conversion efficiency was found to be explained by feedworks and setworks type, and sawblade thickness and type. This analysis of machine characteristics provides information for a rational choice of sawing machines for hardwood sawmills. Those involved in the management, maintenance, and design of sawmills need information on the conversion efficiency of sawing machines. Raw material costs may comprise 75 percent or more of total sawmill manufacturing costs. The choice of sawing machines that convert logs to lumber with least waste is economically important. Some sawing machine characteristics that influence conversion efficiency are saw kerf width, sawing variation, and surface roughness. Saw kerf width determines the amount of fiber lost as each board is sawn from the log. Sawing variation and surface roughness determine the amount of wood fiber that must be added to the green thickness to assure that the final dry dressed thickness can be attained. Increased thickness of green lumber to allow for higher sawing variation and surface roughness results in higher costs for raw material as well as drying, planing, and other lumber processing costs. For softwood sawing machines, a relative abundance of information on kerf width values (1,4,6,9,17,19) and sawing variation (2,4,5,8, 15,18, 19) is available. One publication has examined relative surface roughness of softwood sawing machines (18). Information on the conversion characteristics of hardwood sawing machines is scarce. Only Robichaud (13) compared the characteristics of horizontal and vertical bandsaws. He reported kerf and sawing precision values for four horizontal and four vertical bandsaws and found no significant difference between the machines. The objective of this study was to provide information about the conversion characteristics of hardwood sawing machines and to determine statistical differences between them.