Dimension yields from Factory Grade 2 and 3 red oak logs

With rising timber costs and a decreasing supply of high-grade timber resources, manufacturers of solid wood products need to adopt more efficient processing methods that better utilize existing timber resources. To address this need, this study explores the potential of converting hardwood logs directly into dimension parts. The specific objective of this study was to estimate the potential cutting yield of dimension parts and potential value recovery obtainable from Factory Grade 2 and 3 red oak sawlogs under various processing configurations and cutting bills. A combination method of sawing logs into flitches and then cutting flitches into dimension parts was used. Two log sawing patterns (live sawing and five-part sawing) combined with two cutting sequences (rip first and crosscut first) and three cutting bills were tested. The results indicated that Grade 2 logs produced higher dimension yield than Grade 3 logs. However, Grade 2 logs resulted in much less value recovery per dollar log input than Grade 3 logs because of the notably higher price of Grade 2 logs. These results suggest that direct processing systems offer a very promising method for converting low-grade timber resources into high-value solid wood products. Other results of the study show how different processing configurations and cutting orders can affect yield and value recovery. flitches is edged and trimmed off at the sawmill and put into chips to “up-grade” the board and maximize the market value of the boards. In a previous study (6), it was found that the resulting volume of furniture cuttings could be increased by 25 percent by eliminating edging and trimming of hardwood flitches at the sawmill. This large increase calls attention to a more efficient and economical use of hardwood resources that would have otherwise been converted to a less valuable product. As the price of timber resources increases and as environmental constraints limit the volume of logs that can be harvested, the processing concept of directly converting logs into dimension parts needs to be explored. This direct processing concept can be defined as a manufacturing system that converts hardwood logs directly into rough green dimension parts without the intermediate steps of lumber manufacturing, grading, trading, shipping, drying, and storage. In the direct processing system (Fig. 1), logs are sawn into flitches that may or may not be rectangular pieces, depending on the sawing patterns used. These flitches are immediately cut into green rough dimension parts. The green rough dimension parts are then dried and shipped to furniture makers, cabinet makers, and other users of solid wood parts. The main advantage of the direct processing system is that it can use lower grade logs to produce high-value dimension products. Therefore, the direct processing system will The conversion of logs into dimension parts in a conventional processing system usually takes place in The authors are, respectively, Research Associate, Fortwo steps. In the first step (Fig. 1), logs are sawn into est Products Development Center, School of Forestry, lumber and the lumber is marketed according to Auburn Univ., Auburn, AL 36849; Assistant Professor, standard grades specified by the National Hardwood Dept. of Wood Science and Forest Prod., Virginia Tech, Blacksburg, VA 24061-0323; and Project Leader, USDA Lumber Association (8). In the second step, the lumber Forest Serv., Southeastern Forest Expt. Sta., Virginia Tech, is dried and processed into dimension parts in a Blacksburg, VA 24061-0503. This research was supported dimension mill or a rough mill associated with a by the USDA Forest Serv., Southeastern Forest Expt. Sta. furniture or cabinet plant. In this conventional sysThis paper was received for publication in December 1993. © Forest Products Society 1994. tern, some usable solid wood material from the log Forest Prod. J. 44(9):19-25. FOREST PRODUCTS JOURNAL Vol. 44, No. 9 19 Figure 1. — Comparison of the conventional processing system and the direct processing system. provide a greater value added opportunity for the U.S. hardwood dimension industry with its abundance of lower grade hardwood logs. The direct processing system has been used in Japan and Europe (2) and there has been a recent trend to process dimension parts from logs in the United States (5, 10). However, little comprehensive research in evaluating the direct processing system has been reported. Many areas concerning cutting yield, value recovery, productivity, production costs, profitability, and economic feasibility of a direct processing system remain unanswered. To address the first two of these areas, the objective of this study was to determine the potential cutting yield and value recovery of dimension products that can be attained directly from logs. In particular, this study focused on estimating yield and value recovery from both Grade 2 and 3 red oak logs. The effect of various processing configurations and cutting bills on yield and value recovery was also investigated in this study. Materials and methods The methods used in this study were devised to investigate the potential yield and value recovery of a direct processing system that cuts logs directly to green dimension. Many factors can influence the yield and value recovery of such a system. The factors considered in this study include input log grade (Grade 2 vs. Grade 3), log sawing pattern (live vs. five-part), log flitch cutting sequence (rip-frost vs. crosscut-first), and cutting bill requirements (short, long, and mixed). The following section describes the methods, materials, and assumptions used in the study. Direct processing system configuration The proposed direct processing system that cuts logs directly to green dimension products combines sawmill operations with rough mill operations. Many different direct processing options can be considered including various combinations of headsaw breakLive Sawing Five-Part Sawing Figure 2. — Diagram of live sawing and five-part sawing. down patterns and rough mill cutting sequences. In general, logs enter the mill and are debarked and broken down as typically done in a hardwood sawmill. The flitches that result in this primary breakdown then go through a dimension rough mill process to be cut into green dimension blanks. Consequently, the selection of the primary sawing pattern and rough mill cutting sequences have a substantial effect on the yield and quality of the dimension parts produced. TWO sawing patterns for sawing logs to flitches (live and five-part sawing (Fig. 2)) were considered in this study. These two sawing patterns are currently used in many hardwood sawmills. Five-part sawing has been widely used for sawing low-grade hardwood logs into lumber and cants. In five-part sawing, parts 1 and 2 are usually sawn on a headrig saw, parts 3 and 4 are sawn on a gang resaw, and part 5 (a cant) is removed from the center of each log. The cant can be used for making pallet parts rather than dimension parts. The size of the center cant produced in this study for the five-part sawing method was assumed to be a 4by 4-inch cant. In this study, the two principal cutting sequences currently used in rough mills, rip-first and crosscut-first, were considered for cutting flitches into rough dimension parts.