In Part 2 of LMI's wood scanning blog post they will explore board optimization with Gocator 200 series multi-point laser scanners.
Board optimization (secondary breakdown)
After logs are reduced to flitches and cants, secondary operations are required to edge pieces for width then trim to length at two different machine centers—an edger and a trimmer optimizer.
In both of these machine centers, transverse 3D scanning is introduced to digitize each wood piece and generate 3D shape, 2D surface color, and tracheid (laser scatter effect in wood) data. This information is used to determine the best cutting patterns that yield maximum value recovery based on a constantly changing demand for certain dimensions and grades.
Transverse conveyor systems use multi-point scanners organized above and below the wood flow to build fully stitched 3D models based on the principles of laser triangulation and color imaging running at 3000 Hz. Speed of data acquisition is very important for secondary operations where part rates of 70 to 300 boards per minute are common.
Modular Board Scanning Systems for Finished Grading
With the Gocator® 200 series multi-point scanners, a modular board scanning system can be easily configured to mix 3D profiles, tracheid, and color data. Color, for example, may be used only on the wane-up surface, while profile and tracheid is used on both top and bottom board surfaces.
Gocator profile+tracheid scanner with bolt-on color scanner and one white LED lightbar
A bank of modular Gocator® 200 multi-point scanners mounted above and below boards travelling in a transverse transport system
Multi-Point Scanning for Tracheid
In addition to multi-point scanners minimizing scanner frame space and seeing both edges of a board, these scanners achieve another critical capability––the measurement of tracheid effect.
When a laser spot is projected onto healthy tracheid wood cells, laser light is scattered into the cells in the direction of cell growth. If the wood fibre is dead (as in a knot), then the laser light does not scatter. This effect can be measured to identify good wood from defective wood and even determine grain angle.
From Left to Right - Color, Tracheid Scatter, Tracheid Angle, Knot Detection, 3D Profile
Adding Color Vision for Defect Detection
The introduction of color scanning to identify surface defects such as knots, splits, rot, speck, beetle damage, etc., has led to grade-based recovery optimization, where lumber is cut into boards to obtain the highest grade as opposed to extracting the highest volume. Higher grade output leads to higher dollar returns from the input wood fibre.
Color scanning requires the addition of white light to illuminate the board surface and megapixel color cameras to build high resolution color images. Resolutions down to 0.25 mm are typical in today’s high performance color scanners.
The bolt-on Gocator® 205 vision module (along with a white LED light bar that is strobed to maximize efficiency and lifetime) provides Gocator® 200 scanners with color vision for detection and measurement of surface defects including knots, splits, and rot.
Lumber Optimization with Gocator®
The Gocator® smart sensor feature set offers onboard processing to configure triggering, exposure, resolution, board detection, filtering, stitching, measurement, and built-in communication protocols to other factory equipment using PLC protocols. With an open source SDK, customers can build sophisticated, modular scanning solutions and deliver unique capabilities that are specific to mill requirements.
For more information on 3D scanning for wood optimization applications, visit our wood industry page at http://www.lmi3d.com/solutions/industries/wood.