2017 International Forest Industries Magazines April May 2017 | Page 36

LUMBER PROCESSING
SCANNING & OPTIMISATION – LMI
Delivering a flexible
wood-scanning solution
Transverse board scanning
Wood scanning in
today’s saw and
planer mills demands
a flexible sensor
solution that delivers
several technologies
to achieve maximum
value recovery at high
speed, CEO of LMI
Technologies Terry
Arden told International
Forest Industries
recently
L
MI’s new Gocator 200 series
offers a modular approach
to build a transverse board
scanning solution that evolves with
the mill to meet changing wood
supply and optimization needs,”
he said.
“The Gocator 200 concept
builds on the success of the
chroma+scan series for board
scanning by combining the Gocator
smart sensor capabilities with an
optimized chroma+scan engine to
create greater choices at various
price points and deliver a more
flexible solution to address a
variety of mill scenarios.”
Transverse board-scanning
layout
Transverse scanning requires
multiple 3D scanners positioned
along the length of a board to
deliver profile data for maximizing
volume recovery with optimization
software.
In this setup, scanners are
arranged in opposing pairs along
the board length and generally
cover about 2 ft at a time. In a 20 ft
scanner frame, for example, there
will be 20 sensors with 10 on the
top and 10 on the bottom.
Profile data measures the shape
of a board as it passes through
a scan plane. With opposing
scanners (top and bottom),
the difference between profile
data can be used to accurately
34 International Forest Industries | APRIL / MAY 2017
measure board thickness. Ideally,
the top and bottom scanners
should be aligned to the same
scan plane for maximum board
thickness accuracy. Aligned scan
planes minimize errors due to
vertical board movement caused
by vibration or unstable board
transport.
Multi dot versus line profiling
technologies
Scanners generate 3D profile
data by projecting a laser pattern
onto the board surface and then
measuring the position of the
reflected pattern using cameras.
As the board height varies, the
laser pattern shifts in the receiving
camera. A factory calibration of
the scanner determines how laser
patterns on a camera are mapped
Gocator profile+tracheid scanner
with bolt-on colour scanner and
one white LED lightbar: Gocator
profile+tracheid scanner with bolt-
on colour scanner and one white
LED lightbar
to physical units in thousands of an
inch or millimeters.
The laser and camera are
positioned in a scanner head based
on laser triangulation geometry,
where the camera is tilted on an
angle to view the projected laser
pattern such that board height
changes cause laser patterns to
shift in the camera image.
Two types of scanners are
common in today’s market: multi-
dot and line profiler. Aside from the
difference in laser pattern (a single
laser line versus many laser dots),