Sawmill

United States
Department of
Agriculture
Forest Service
Forest
Products
Laboratory
General
Technical
Report
FPL-48
Sawmill Simulation
and the
Best Opening Face
System
A User’s Guide
David W. Lewis
Abstract
Computer sawmill simulation models are being used to
increase lumber yield and improve management control.
Although there are few managers or technical people in the
sawmillindustry who are not aware of the existence of these
models, many do not realize the models’ full potential.
The first section of this paper describes computerized
sawmill simulation models and their use for those who have
an interest in the subject, but who will not necessarily be
involved in their implementation. The areas of use discussed
include management planning and decisionmaking,engineering, automated control systems, and evaluating
operating efficiency.
The second section details the Best Opening Face program
(BOF), the most widely used of the sawmill models
simulating the process of recovering dimension lumber from
small-diameter, sound, softwood logs. The assumptions
used in the program and the theoretical sawing process are
discussed.
The third sectiondescribes the mechanics and possible
pitfalls of using BOF. The sawmill configuration simulated by
BOF is controlled by data describing a particular mill and
options which control the program flow.
The appendices contain several formulas, examples of
various BOF report formats, and a discussion of using BOF
to simulate sawing metric-sized lumber.
Keywords: Best Opening Face; sawmilling;simulation;
system analysis; computer techniques; sawing patterns;
process control; automation; lumber recovery factor; lumber
yield; log breakdown; models.
December 1985
Lewis, David W. Sawmill simulation and the Best Opening Face
system:A user’s guide, Gen. Tech. Rep. FPL-48. Madison, WI: U.S.
Department of Agriculture, Forest Service, Forest Products Laboratory;
1985. 29 p.
A limited number offree copies of this publication are available to the public
from the Forest Products Laboratory, One Gifford Pinchot Drive, Madison, WI
53705-2398. Laboratory publications are sent to over 1,000 libraries in the
United States and elsewhere.
The Laboratory is maintained in cooperation with the University of Wisconsin
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . .
Uses for Sawmill Simulation Models . . . . . . . . . . . . . . .
In Management Planning . . . . . . . . . . . . . . . . . . . . . .
In Engineering and Design . . . . . . . . . . . . . . . . . . . . .
In Automated Control Systems . . . . . . . . . . . . . . . . .
In Evaluating Sawmill Efficiency . . . . . . . . . . . . . . . .
Best Opening Face System . . . . . . . . . . . .. . . . . . . . . .
Assumptions in the BOF Model . . . . . . . . . . . . . . . . .
Geometry of Logs and Pieces . . . . . . . . . . . . . . . .
Target Size Calculations . . . . . . . . . . . . . . . . . . . . .
Lumber Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wane.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Yield Maximization . . . . . .. . . . . . . . . . . . . . . . . . . .
Value Maximization . . . . . . . . . . . . . . . . . . . . . . . . .
Volume Maximization . . . . . . . . . . . . . . . . . . . . . . . .
Theoretical Sawing Process . . . . . . . . . . . . . . . . . . . .
Primary Log Breakdown . . . . . . . . . . . . . . . . . . . . .
Edging and Trimming . . . . . . . . . . . . . . . . . . . . . . . .
Cant Breakdown .. . . . . . . . . . . . . . . . . . . . . . . . . . .
Yield Maximization . . . . . . . . . . . . . . . . . . . . . . . . . .
Using the Best Opening Face System . . . . . . . . . . .
Required Information . . . . . . . . . . . . . . . . . . . . . . . .
Minimum and Maximum Small-End Log
Diameter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Taper . . . . . . . . . . . . ....