Views: 457 Author: Site Editor Publish Time: 2024-06-30 Origin: Site
In the building sector, laminated veneer lumber (LVL) is a frequently used engineered wood product. It's a manufactured product consisting of multiple thin veneer layers oriented longitudinally in the finished wood product. This article compares LVL to various engineered wood products for building structures, including its advantages, disadvantages, and basic manufacturing techniques.
Production of LVL started in 1941. It was made from 3.6 mm thick Sitka spruce veneer to construct aircraft parts. Due to high interest in LVL, the USDA Forest Products Laboratory conducted extensive research to enhance its strength characteristics.
Douglas fir is the primary raw material utilized for producing LVL in the United States, along with Yellow poplar, Southern pine, and other softwoods. Radiata pine is commonly utilized in New Zealand while rubberwood is widely used in Southeast Asian countries.
Veneer sheets with thicknesses ranging from 2.5 mm to 4.8 mm are produced by the rotary peeling method. Veneer typically employed in the creation of LVL is 3.2 mm thick.
Logs are peeled rotary on a lathe; the quality of the veneer is determined in large part by the geometry and placement of the knife. For example, to effectively peel softwood, a bevel angle of roughly 23 degrees is selected for the knife.
The veneer is regularly peeled from the log at a constant thickness and crack-free condition by applying a precise amount of pressure with the pressure bar. The veneer on one side opposite the knife-edge is called the tight side, and the veneer adjacent to it is called the loose side. Numerous microscopic cracks generated by lathe checks aligned with the grain are visible on the loose side of the veneer.
Depending on its diameter, a bolt, a short log, can take anywhere from 5 to 10 seconds to be peeled before its core is removed and the charger is prepared for the next round. Ribbon-like veneer sheets are continuously cut to a specific width and subjected to jet tube dryers to reach a desired moisture level.
Hot air is directed onto the veneer sheets' surface to remove moisture, decreasing the veneer's overall moisture content to a specific point within the jet tube dryer. A typical 3 mm thick Douglas fir veneer might require 10-13 minutes to lower its moisture level to 8 to 10 percent.
Although the processes utilized in the production of LVL and structural plywood are similar, the main difference is in the veneers' grain orientation. A variable quantity of veneer sheets are stacked on top of one another throughout the manufacturing process to create plywood, which has better mechanical properties and increased dimensional stability.
As a result of each lamina being aligned with the board axis, LVL offers qualities that are similar to those of solid lumber by arranging extra veneers in a longitudinal manner.
During the clipping process, flaws on every veneer are removed. Although defects may be present on individual veneer sheets, the random dispersion of these defects when assembling the veneers leads to a final product that is more consistent and has strength properties similar to high-quality lumber. The veneer sheets are stacked and compressed at temperatures ranging from 250 to 450 degrees Fahrenheit after external adhesive, usually phenol formaldehyde, is applied to their surfaces.
LVL presses are longer in comparison to plywood presses. The press line can be either in batch mode or continuous mode. A batch-type press can be equipped with either one or multiple openings, making it more effective for manufacturing shorter length LVL.
However, the majority of mills utilize a continual press line. Billets are produced in widths of up to 6 feet and can be shipped in lengths of up to 80 feet. Diagrams in figures 4 and 5 depict a typical manufacturing process of LVL.
Laminated veneer lumber is a flexible product made from wood. In combination with plywood, lumber, or oriented strand board (OSB), LVL has various structural uses.
Some common applications of LVL are I-joists, headers, rimboards, truck bed decking, roadway signposts, beams, trusses, specialized uses like skateboards, and custom panels for marine purposes.
Primary benefits of LVL consist of its size, form, exceptional durability characteristics, and affordable price. The can be manufactured in any size because its production method is not limited by log dimensions. It is among the most durable wood-based building materials in relation to its weight.
Its constant quality, with few or evenly dispersed faults, allows one to predict the end product's mechanical qualities. Generally speaking, depending on its intended use, LVL can be produced in a variety of ways. It also gains a great deal from the effective use of wood resources.
On the other hand, it also has severa drawbacks as a type of wood composite. There is only a small increase in the strength properties of LVL when the veneer is densified during the pressing process. Even though it has superior dimensional stability compared to solid wood, if not stored correctly in the warehouse, this product may still end up with defects like warping.
Furthermore, LVL requires a substantial capital investment despite having comparatively low production costs. Thus, strong demand is necessary for a prosperous business.
Please contact Miranda for all of your woodworking machines and equipment needs if you would want comprehensive information about the creation of LVL and its features.