This document describes research to develop an automated optical method for measuring face checking in maple veneered panels. The method uses cameras to monitor panel surfaces and detect checks as small as 0.2mm wide. Tests showed industrial cameras could simultaneously monitor multiple panels in a climate chamber maintained at low moisture levels to accelerate check formation. Future work involves building a modular test chamber and further testing camera capabilities to characterize many factors that influence checking.

1. An automated optical method for
measuring and characterizing face
check development in maple
veneered panels
Mike Burnard
Lech Muszynski, Ph.D.
Scott Leavengood, Ph.D.
Lisa Ganio, Ph.D.
Oregon State University

2. Outline
• Introduction
• Background & Motivation
• Objective
• System Requirements & Components
• Future work

3. Background: maple panels
• Decorative
• Used indoors
• Can be expensive
• A composite with face, core, & back

4. Background: panel manufacturing
Decorative maple panel
manufacturing involves
many factors including:
veneer, adhesives,
cores & pressing
oakwoodveneer.com, inhabitat.com

5. Background: checking
Checking is
caused by the
differential
drying rate
between the face
and the core of
the panel

6. Background: panel checking
Many factors have been
identified as possibly
contributing to checking:
• Veneer properties
• Panel construction
• Service conditions

7. Background: checking factors
• Veneer thickness • Adhesive type
• Lathe check • Core type
orientation • Pressing cycles
• Sliced/peeled • Cross-band lathe
• Log prep method check orientation
• Source region • others…

8. Background: panel checking
Standards allow 2 small, mended
checks in specific regions:
.8mm wide, 72mm long on
edges

9. Motivation
• Checking is an expensive problem for
manufacturers and the industry
• Manufacturing maple veneer plywood panels
is complex and involves many factors

10. Motivation
• Large studies testing many factors have been
impractical because of the laborious manual
inspection methods used in the past
• An experimental method to efficiently
measure and quantify checks as they occur

11. Background: optical method
Kang et al (2007)
developed a non-
contact optical method
to detect checks as
they occur. The
method lends itself to
automation.

12. Background: optical method
Uses two cameras
trained on an object to
monitor how it
changes over time in
three dimensions.

13. Strain, εx
Kang et al, 2007 Negative Positive
110 min
185 min

14. Objective
Develop an efficient procedure in which the
optical method can be applied to measure
checks as they develop in multiple panels
simultaneously to test an unprecedented
number of factors

15. Checking factors
• Veneer thickness • Adhesive type
• Lathe check • Core type
orientation • Pressing cycles
• Sliced/peeled • Cross-band lathe
• Log prep method check orientation
• Source region • others…

16. System Components
• Modular optical unit with sufficient resolution
to detect critical checks
• Climate chamber capable of maintaining a low
equilibrium moisture content to accelerate
check formation

17. Requirements: critical checks
Determined critical checks
are those with a minimum
width of:
~0.2 mm

18. Requirements: optical unit
Detecting critical
checks in multiple
panels
simultaneously is
imperative.

19. Requirements: optical unit
Utilizing multiple cameras
allows more panels to be
examined simultaneously.
Test single vs. dual cameras &
industrial vs. consumer
cameras

20. Requirements: optical unit
Consumer cameras
proved unreliable and
not easily automated.
Both single and dual
industrial cameras
proved sufficient to
detect critical checks.

21. Strain, εxx
0.010 50mm Lens Single Camera
12mm Lens Single Camera
0.005 50mm Lenses Dual Camera
Strain
0.000
-0.005
-0.010
0 1 2 3 4 5 6 7
Image

22. Requirements: climate chamber
• Size
• Dedicated
• Climate conditions
Temperature and relative humidity tests
revealed an average equilibrium moisture
content of:
8%

23. Requirements: climate chamber
Introducing a space heater with a fan reduced
the equilibrium moisture content to:
6%

24. Future Work
• Purchase and test lower-resolution industrial
cameras
• Build modular test chamber
Work in progress…

25. Thank you.
Questions? Comments?

26. Temperature (°C), Relative Humidity (%) & Equilibrium
Moisture Content (%)
45 9
RH, % Temp, C
Temperature (°C), Relative Humidity (%)
EMC, % 8
40
7
35 6
EMC (%)
5
30
4
25
3
20 2
1651
1
Time intervals (x5 minutes)

27. Panel weight loss
21C, 41%RH 31C, 27%RH
1100
1095
1090
Weight (g)
1085
1080
1075
1070
0 50 100 150 200 250 300
Time (minutes)

28. References available upon request