Sorting Lumber By Grade Prior To Rough Mill Processing
Research Brief #5
Louisiana Forest Products Laboratory
Louisiana State University
Baton Rouge, LA
Research Objective
Develop and demonstrate a procedure to determine the benefits of sorting
lumber by grade prior to rough mill processing.
Synopsis of Results
A computer program and procedure was developed to determine yield,
processing time, and machine utilization differences between processing unsorted and sorted by
grade lumber in both crosscut-first and rip-first rough mill systems.
Crosscut-First Case Study
- A yield increase of about 1 percent was obtained for lumber sorted by grade prior to processing.
- Total processing time was not influenced by sorting lumber prior to processing.
- The actual machine utilization was increased by 9.4 percent for the crosscut saw and decreased
by 16.7 percent for the salvage crosscut saw when sorted lumber was processed.
Rip-First Case Study
- Sorting lumber by grade prior to processing in the rip-first rough mill increased yield by 0.3
percent.
- Total processing time was decreased by 2.0 percent when processing sorted lumber.
- The actual machine utilization was increased by 25 percent for the crosscut saws, decreased by
1.8 percent for the sorting operation, and increased by 13.5 percent for the salvage straight-line
rip saws when processing sorted lumber.
Conclusions
Simulation software can be employed to determine the benefits of sorting lumber prior to rough
mill processing. Simulation of each specific rough mill situation is required to determine these
benefits because differences in rough mill variables will influence the results. The examples
given here, however, showed rough mill sorting to have influence on rough mill yields,
processing times and percentage machine utilization.
Researchers
Rado Gazo, Post-Doctoral Researcher
Louisiana Forest Products Laboratory
LSU Agricultural Center
Philip H. Steele, Professor
Mississippi Forest Products Laboratory
Target Group
Secondary wood manufacturers
Methodology
Rough mill yield, throughput, processing time and machine utilization can be determined by
simulating the material flow in the rough mill. The RAM (Rough Mill Analysis Model) is a
processoriented simulation software. The user describes the rough mill operation, and RAM then
simulates the flow of the specified lumber grade mix through the model rough mill in real time.
The lumber can be processed as either sorted by grade or unsorted. Boards for the simulation are
randomly sampled from a digitized database of lumber.
Existing crosscut-first and rip-first rough mills were simulated using computer program RAM to
provide the comparisons of yield and processing times of sorted versus unsorted lumber.
For both the simulated crosscut-first and rip-first rough mill systems, six identical cutting orders
were filled for both sorted and unsorted lumber. The grade mix was specified to contain onethird
of each of the grades of Firsts and Seconds, No. 1 Common, and No 2A Common.
Rough mill type, processing method, and cutting order were the factors analyzed in a three-factor
completely randomized, balanced experimental design.
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This page was last updated: 29-MAR-95, by: James Babin <jbabin1@tiger.lsu.edu>