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Raw Materials of Cogent Home Prefabricated Wooden House
Time:2012-03-02

 Lumber Products

Machine-graded Lumber Most lumber is visually graded by lumber graders who examine each piece and apply visual grading rules to establish its grade, which determines the structural design value. While visual grading still works well, the demand for high-performance lumber has led to enhanced grading
techniques.
Unlike other engineered wood products that rely on product design to impart engineered qualities, machine-graded lumber is solid sawn lumber that relies on mechanical evaluation to more closely ascertain its engineering properties.
As part of this process, each piece of lumber is non-destructively evaluated by equipment designed to measure physical properties. The machine tests each piece of lumber and strength properties are determined from longestablished property relationships verifi ed by daily quality control testing.

As lumber is fed continuously into typical mechanical evaluating equipment, stiffness is measured and recorded by a small computer, and strength is assessed by correlation methods.

Machine-graded lumber is also visually checked for properties other than stiffness, which might affect the suitability of a given piece. The result is a more precise understanding of the strength distribution of the grade of machine-graded lumber than is possible with visually graded lumber. There are two types of machine - graded lumber: machine stress-rated (MSR) lumber and machine evaluated lumber (MEL). MSR is the more common and traditional lumber product; MEL offers some less traditional
grades and properties.

The major advantage of machine-graded lumber is that the engineering properties are determined more directly than by visual grading alone, making it possible to use structural lumber elements closer to the limit of their design capacity. Therefore machine- graded lumber is used where higher and more consistent
structural properties are required. For example, machine-graded lumber is typically used for wood trusses, where the performance of each member is critical.

Machine-graded lumber can be produced for a wide variety of end-use applications. In addition to the grades found in the grade rules, special E-Rated (LAM) laminating stock, and export grades are commonly produced to specifi c customer requirements.