Potential for Yield Improvement in Combined Rip-First and Crosscut-First Rough Mill Processing

• Main Authors: R. Edward Thomas, Urs Buehlmann
• Format: Article
• Language: English
• Published: North Carolina State University 2015-12-01
• Series: BioResources
• Subjects: Rip-first; Rough mill lumber yield; Performance; Cut-up systems; Crosscut-first
• Online Access: http://ojs.cnr.ncsu.edu/index.php/BioRes/article/view/BioRes_11_1_1477_Thomas_Yield_Improvement_Rough_Mill_Processing

Traditionally, lumber cutting systems in rough mills have either first ripped lumber into wide strips and then crosscut the resulting strips into component lengths (rip-first), or first crosscut the lumber into component lengths, then ripped the segments to the required widths (crosscut-first). Each method has its advantages and disadvantages. Crosscut-first typically works best for the production of wider components, while rip-first favors the production of narrower and longer components. Thus, whichever type of processing method is selected for a given rough mill usually depends on the characteristics of the cutting bills the mill expects to process. There is a third option, a dual-line mill that contains both rip-first and crosscut-first processing streams. To date, such mills have been rare for a variety of reasons, complexity and cost being among them. However, dual-line systems allow the mill to respond to varying cutting bill size demands as well as to board characteristics that favor one method (rip-first or crosscut-first) over the other. Using the Rough Mill Simulator (ROMI 4), this paper examines the yield improvement potential of dual-line processing over single-system processing (i.e., rip-first or crosscut-first processing alone) for a variety of cutting bills and lumber grade mixes.