Research Brief #5

Sorting Lumber By Grade Prior To Rough Mill Processing
Louisiana Forest Products Development Center
Louisiana State University
Baton Rouge, LA

Research Objectives

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

• 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

Researchers

Rado Gazo, Post-Doctoral Researcher
Louisiana Forest Products Development Center
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 process-oriented 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 one third 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.