Download Non-Contact Laser Gauge Advantages

New Non-Contact, Laser-Based Gauge
for Measuring Length and Speed of
Gypsum Board
Stuart Manser
Beta LaserMike
Non-Contact Laser Gauge
Introduction
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Technology of a Non-Contact Length and Speed
gauge
Describe how it works
Two applications examples:
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Cut Length
Cutter Control
Non-Contact Laser Gauge
Traditional Length & Speed Measurements
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Accomplished by using a roller that contacts the
material being measured
The material turns the roller as the material
moves
An encoder or tachometer is attached to the
roller
 Generates pulses as the wheel or roller
rotates
 Relies on friction between the material and
roller
Non-Contact Laser Gauge
Disadvantages Tachometers/Encoders
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Error caused by slippage
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Recalibration
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Dependent on friction
Wheel pressure
Product surface
Diameter change because of wear
Diameter change because of build-up
Maintenance
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Bearings and other mechanical parts wear out
Non-Contact Laser Gauge
LaserSpeed History
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LaserSpeed technology was developed in
1984
Aluminum/Steel Mills
Small integrated gauge developed in 2001
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Compact
Lower Cost
Easy to Install
High Accuracy – 0.05%
Non-Contact Laser Gauge
System Concept
FPGA- Signal
processing PCB
Laser diode assembly
with temperature control
Proprietary beams
steering optics and
receiving optics
Measuring region
Non-Contact Laser Gauge
Non-Contact Gauge Technology
Non-Contact Laser Gauge
Non-Contact Gauge Technology
Two laser beams cross at an
angle 2K
K bisects the two laser beams
Constructive and Destructive
Interference cause a Fringe
Pattern
The Fringe Pattern consists of
light (constructive) and dark
(destructive) stripes
Non-Contact Laser Gauge
Fringe Pattern Expanded
 Constructive Interference
occurs when two laser
beams are in phase and add
together to equal the original
laser density - light stripe
 Destructive Interference
occurs when two laser
beams are out of phase and
the two laser beams cancel
each other out - dark stripe
Non-Contact Laser Gauge
Fringe Pattern Generation
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Fringe Pattern looks
like an elongated
football
Measuring region
(Depth of Field) is
where the fringe
pattern exist
Project this fringe
pattern on the
surface of the
product to be
measured
Non-Contact Laser Gauge
Laser Doppler Velocimetry (LDV) Theory
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d
2 sin
d
v
t
1
t
f
V d* f
L
T
0 vd t
Fringe direction
Non-Contact Laser Gauge
No Calibration Required
d
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2 sin 
of the laser is fixed
Wave length
and constant
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 is created optically
Crossing angle
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Laser diode based system
Laser diode is temperature controlled
No moving parts in optics package
Crossing angle is permanently fixed
Fringe Spacing ‘d’ is fixed and
cannot change
Non-Contact Laser Gauge
No Calibration Required
d
v
t
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Frequency measurement uses an
all Digital Signal Processor
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1
t
f
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V d* f
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Autocorrelation algorithm
High measurement rate
High measurement accuracy
High measurement repeatability
Signal processor is all digital
and has no drift or measurement
error
Non-Contact Laser Gauge
No Calibration Required
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T
L  0 vd t
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Length is achieved by
numerically integrating
the speed
Permanently calibrated
with very high accuracy
Non-Contact Laser Gauge
Non-Contact Gauge Block Diagram Dual-Beam Laser Interferometer
Diode Laser
Acusto-Optical Modulator
Optical Beam Splitter
Photo -Detector
Product
Received Light
Receiving Lens
(15mm)
Measurement Region
Fringe
Direction
Non-Contact Laser Gauge
Cut-to-Length Application
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Gypsum board manufacturer
Plant produces 4 x 12 ft (120 x 366
cm) boards
Needed more accurate method for
measuring length of wallboards
after cut
Used mechanical wheel encoders to
perform cut-to-length
measurements
Non-Contact Laser Gauge
Problem
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Contact method caused boards to
crumble and stick to encoder
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Clean-up, repair, and calibration of
encoders
Discrete boards difficult to measure
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Changes diameter of roll wheel
Damage to product
3- to 4-inch (7.6 to 10.2 cm) gaps
between boards
Inaccurate length measurements
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2% error
Non-Contact Laser Gauge
Scrap Cost Calculation
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260 production days per year
22 hours of production a day
Line rate of 550 ft/min (152 m/min)
Cost per unit length to manufacture material
is $.20*
Current encoder accuracy is 2.0%
Total scrap per year: $736,276
*Cost of material for example purposes only.
Non-Contact Laser Gauge
Solution
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Installed non-contact laser gauge
after the cutting system
Controls cut-to-length accuracy
and product quality
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12” standoff distance
Perpendicular to board
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Measures discrete product length
0.05% accuracy
No damage to product
Dramatically decreases product
scrap and material reprocessing
Significant production savings
Low cost of ownership
Non-Contact Laser Gauge
Cutter Control Application
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Gypsum board manufacturer
Needed to:
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Accurately measure product length during
production
Perform precise cut lengths
Optimize product quality
Non-Contact Laser Gauge
Problem
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Used mechanical contact encoders to measure
product length during board cutting
Signals sent from encoder via PLC to cutting system
Mechanical encoder 2% inaccurate:
 Wet, debris-laden boards caused slippage
 Vibration caused encoder wheels to bounce
 Damage to product surface and encoder
Inaccurate length caused synchronization issues with
cutter
Frequent downtime to clean, recalibrate, or service
encoder; reset cutting system
Resulted in material loss and product quality issues
Non-Contact Laser Gauge
Scrap Cost Calculation
Scrap = amount of material produced/year x
material cost/unit of measure x
contact encoder accuracy (2%)
Significant product loss and downtime costs
to manufacturer
Non-Contact Laser Gauge
Solution
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- Installed upstream from cutting
system
- 12” standoff distance
- Perpendicular to board
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Replaced mechanical contact
encoders with non-contact
laser gauge
Accurate length
measurements (0.05%)
Precise synchronization with
cutting system
Reduced a significant amount
of scrap
Minimized maintenance,
decreased downtime
Non-Contact Laser Gauge
Summary
Non-Contact Laser Gauge Advantages
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No slippage error or debris accumulation optical system and does not contact the
product
Direct measurement of product
Permanently calibrated – Laser
Interferometer Optical system
No moving parts to wear out
Accuracy: +/-0.05%
Repeatability: +/-0.02%
Non-Contact Laser Gauge
Summary Continued
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Complete System
in one small
rugged package
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26.25 X 20.67 X 10.5 cm
2.54 Kilograms
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Sensor
Processor
I/O
Power Supply
24 VDC operation
IP67 protection
Built-in water
cooling ports
Non-Contact Laser Gauge
New Non-Contact, Laser-Based Gauge
for Measuring Length and Speed of
Gypsum Board
Stuart Manser
Beta LaserMike