U.S. patent application number 13/468328 was filed with the patent office on 2012-08-30 for system and method for detecting features on a laminated veneer lumber billet.
This patent application is currently assigned to WEYERHAEUSER NR COMPANY. Invention is credited to David C. Irving, Thomas J. Taylor.
Application Number | 20120216939 13/468328 |
Document ID | / |
Family ID | 44061217 |
Filed Date | 2012-08-30 |
United States Patent
Application |
20120216939 |
Kind Code |
A1 |
Irving; David C. ; et
al. |
August 30, 2012 |
System and Method for Detecting Features on a Laminated Veneer
Lumber Billet
Abstract
The disclosure relates to systems and methods for detecting
features on billets of laminated veneer lumber (LVL). In some
embodiments, an LVL billet is provided and passed through a
scanning assembly. The scanning assembly includes an x-ray
generator and an x-ray detector. The x-ray generator generates a
beam of x-ray radiation and the x-ray detector measures intensity
of the beam of x-ray radiation after is passes through the LVL
billet. The measured intensity is then processed to create an
image. Images taken according to the disclosure may then be
analyzed to detect features on the LVL billet.
Inventors: |
Irving; David C.; (Boise,
ID) ; Taylor; Thomas J.; (Seattle, WA) |
Assignee: |
WEYERHAEUSER NR COMPANY
Federal Way
WA
|
Family ID: |
44061217 |
Appl. No.: |
13/468328 |
Filed: |
May 10, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12622608 |
Nov 20, 2009 |
8197622 |
|
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13468328 |
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Current U.S.
Class: |
156/64 ;
378/54 |
Current CPC
Class: |
B32B 38/185 20130101;
B32B 41/00 20130101; G01N 23/04 20130101; B07C 5/3422 20130101 |
Class at
Publication: |
156/64 ;
378/54 |
International
Class: |
B32B 37/10 20060101
B32B037/10; G01N 23/083 20060101 G01N023/083 |
Claims
1. A system for detecting features on a laminated veneer lumber
(LVL) billet, the LVL billet having a first planar surface and a
second planar surface, the system comprising: a scanning assembly
comprising: an x-ray generator positioned above the first planar
surface, the x-ray generator being configured to project a beam of
x-ray radiation onto the first planar surface; and an x-ray
detector positioned below the second planar surface, the x-ray
detector being configured to measure intensity of the beam of x-ray
radiation after is passes through the LVL billet; and an image
processor configured to generate an image from the measured
intensity; wherein the measured intensity is inversely
proportionate to density of the LVL billet.
2. The system of claim 1, further comprising a platform attached to
the frame, the platform being configured for receiving the LVL
billet.
3. The system of claim 1 wherein the features are substantially
perpendicular to the beam of x-ray radiation.
4. The system of claim 1 wherein the features are selected from the
group consisting of lap lengths and slip sheets.
5. The system of claim 1, further comprising an x-ray collimator,
the x-ray collimator being configured to narrow the beam of x-ray
radiation generated by the x-ray generator.
6. The system of claim 1 wherein the x-ray generator, the x-ray
detector, and the image processor are mounted on a frame, the frame
comprising: one or more upper components arranged in a
substantially parallel configuration; one or more lower components
located a distance from the one or more upper components, the one
or more lower components being arranged in a substantially parallel
configuration; and four or more side components connecting the one
or more upper components to the one or more lower components.
7. The system of claim 5 wherein the frame is positioned at an
outfeed of a press in an LVL manufacturing line.
8. The system of claim 1 wherein the image is a 128 pixel scan
line.
9. A method for detecting features on laminated veneer lumber (LVL)
comprising: providing a first group of veneers; forming a first
billet from the first group of veneers by: aligning the first group
of veneers; and pressing the first group of veneers; exposing the
first billet to a beam of x-ray radiation; detecting information
about one or more features on the first billet; providing a second
group of veneers; and forming a second billet from the second group
of veneers by: aligning the second group of veneers; and pressing
the second group of veneers; and using the information about the
one or more features on the first billet to optimize forming of the
second billet.
10. The method of claim 9 wherein the step of forming a second
billet from the second group of veneers using the information about
the one or more features on the first billet to optimize forming of
the second billet comprises: altering alignment of the second group
of veneers based on the information about the one or more features
on the first billet; or altering pressing of the second group of
veneers based on the information about the one or more features on
the first billet.
11. The method of claim 9 wherein the information about the one or
more features on the first billet is selected from the group
consisting of information about lap length and information about
existence of slip sheets.
12. The method of claim 9 wherein the step of forming a second
billet from the second group of veneer using the information about
the one or more features on the first billet to optimize formation
of the second billet further comprises: generating an image of the
information about the one or more features on the first billet, the
image comprising one or more pixels arranged in a one or more
columns; calculating a mean intensity for each of the one or more
columns; creating a one dimensional array based on each mean
intensity; fitting a second order polynomial to the one dimensional
array; subtracting the second order polynomial from the
one-dimensional array to create a difference array; passing the
difference array through a low pass filter to create a filtered
array; performing a peak and valley search on the filtered array to
identify overlaps or gaps on the first billet.
13. The method of claim 9 wherein the step of exposing the first
billet to a beam of x-ray radiation is performed by a scanning
assembly, the scanning assembly comprising: an x-ray generator
positioned above the first billet; and an x-ray detector positioned
below the first billet.
Description
TECHNICAL FIELD
[0001] The present disclosure is directed generally to systems and
methods for detecting features on laminated veneer lumber (LVL).
More specifically the disclosure is directed to detecting the
presence of slips sheets on LVL and determining the lengths of lap
joints on LVL.
BACKGROUND
[0002] Laminated veneer lumber (LVL) is an engineered wood product
that is fabricated from sheets of thin wood pieces (e.g., veneers)
that are glued together in panels called billets. When LVL is
manufactured, the veneers are oriented so that the grain in each
individual sheet is aligned primarily along the length of the
billet. Pieces of LVL are trimmed from the billet for use in a
variety of applications (e.g., joists, headers, beams, rafters,
flanges for I-joists, etc.).
[0003] FIG. 1 is a flow chart depicting a conventional LVL
manufacturing process 100. The start of the LVL manufacturing
process 100 depends on how the plant running the process 100
obtains the veneers. Plants may either peel and dry veneers onsite
(step 102), purchase green veneers (step 104) and dry them onsite
(step 108), or purchase pre-dried veneers (step 106).
[0004] After initial processing, the veneers are graded for
stiffness and/or strength as shown in step 110. Generally, veneer
grading is a highly automated process involving both visual grading
methods and automatic grading methods (e.g., ultrasonics). The
objective of grading is to permit the most efficient use of the
available veneer. The lower grade veneers are used for the LVL core
and the higher grade veneers are used in the LVL face.
[0005] Following grading, the veneers are laid out and prepared for
pressing. An adhesive (e.g., a resin) is applied to the veneers
(step 112) and the veneers are aligned or laid up (step 114). FIG.
2 shows a typical veneer lay up 200 according to the method
described in FIG. 1. As shown in FIG. 2, a first veneer piece 202
having a first edge 204 is aligned next to a second veneer piece
206 having a second edge 208 so that the first edge 204 and the
second edge 208 overlap. The overlapping distance is shown as
reference character 210. LVL billets are produced by applying
layers of veneer and adhesive sequentially. Some plants utilize
modular assembly systems containing a station for each successive
layer of veneer in the product.
[0006] After lay up, the veneers are pressed. During pressing (step
116), LVL is manufactured to either a fixed length using a batch
press, or to an indefinite length using a continuous press. FIG. 3
shows an example of a pressing operation 300. In FIG. 3, the
veneers and placed between a first platen 302 and a second platen
304. The first platen 302 and second platen 304 are pressed toward
each other to form a lap joint 306. The presses are heated by
electricity, microwaves, hot oil, steam, or radio-frequency (RF)
waves. Press temperatures range from about 120.degree. to
230.degree. C. (250.degree. to 450.degree. F.). The exact pressing
conditions are designed to bring the veneer surfaces tightly
together without over-compressing the wood.
[0007] FIG. 4 shows the lap joint 306 in a finished billet 400
after it is removed from the press. Billets exiting the press may
be up to 8.9 centimeters (3.5 inches) thick. Billets are produced
in widths of up to 2.8 meters (4 feet). After exiting the press,
the billets are visually inspected (step 118) to identify
particular features (e.g., lap lengths, slip sheets).
[0008] After inspection, the billets are cut into LVL (step 120).
The billets are typically cut into numerous strips based on
customer specifications. The LVL is produced in lengths up to the
maximum shipping length of 24 meters (80 ft). After the LVL is cut,
other finishing applications may be performed (e.g., sorting,
treating, stacking, stamping) as depicted by step 122.
[0009] A common challenge in veneer manufacturing is avoiding the
formation of slip sheets. A slip sheet is a feature where two
pieces of veneer intended to form a lap joint have failed to
overlap. FIG. 5 is a top view of a billet 500 which illustrates
this problem. The portion of the billet 500 shown is formed by a
first veneer sheet 502, a second veneer sheet 504, a third veneer
sheet 506, and a fourth veneer sheet 508. The first veneer sheet
502 and the second veneer sheet 504 have failed to overlap, forming
a slip sheet depicted as reference character 510. In contrast the
second veneer sheet 504 has been pressed to adhere to the third
veneer sheet 506, forming a lap joint shown as a dotted line 512.
Likewise, the third veneer sheet 506 has adhered to the fourth
veneer sheet 508 forming a lap joint shown as a dotted line 514.
Features such as the slip sheet 510 may cause the potion of the
billet 500 where the veneer sheets do not properly overlap to
exhibit inferior mechanical properties when compared with the
portions of the billet 500 where proper lap joints have been
formed. Currently slip sheets and other features are detected
visually by workers who inspect the billets for visible defects
(see step 120 in FIG. 1). Therefore, there is an opportunity to
improve LVL manufacturing processes by developing automated methods
for inspection.
[0010] In addition to avoiding slip sheet formation, LVL
manufacturers also strive to optimize the length of the lap joints
which are successfully created. The length of a lap joint is
commonly referred to as a lap length. Lap length is currently
determined visually during the inspection step 120 from FIG. 1. Lap
lengths that are too short may result in the manufacture of final
product that has inferior mechanical properties. On the other hand,
manufacturing LVL with a lap length that is too long is not an
efficient use of the raw materials in supply. Currently presses are
without any direct feedback or indication of lap position.
Therefore, it is common practice to operate with excessive laps to
reduce the risk of product fall down.
[0011] Thus, there is a need to develop improved systems and
methods for detecting features during LVL manufacturing.
Specifically, there is a need to develop systems and methods for
detecting lap lengths and slip sheets in billets. Such systems and
methods could be used to optimize the LVL manufacturing process and
to control the quality of the final product.
SUMMARY
[0012] The following summary is provided for the benefit of the
reader only and is not intended to limit in any way the invention
as set forth by the claims. The present disclosure is directed
generally towards to systems and methods for detecting features on
laminated veneer lumber.
[0013] In some embodiments, the system includes a frame, a scanning
assembly, and an image processor. The scanning assembly includes an
x-ray generator and an x-ray detector. The x-ray generator
generates a beam of x-ray radiation and the x-ray detector measures
intensity of the beam of x-ray radiation after is passes through
the LVL billet. The measured intensity is then processed to create
an image. Images taken according to the disclosure may then be
analyzed to detect features on the LVL billet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] The present disclosure is better understood by reading the
following description of non-limitative embodiments with reference
to the attached drawings wherein like parts of each of the figures
are identified by the same reference characters, and are briefly
described as follows:
[0015] FIG. 1 is a flow chart depicting a conventional LVL
manufacturing process;
[0016] FIG. 2 is a perspective view of a veneer alignment step
according to the method described in FIG. 1;
[0017] FIG. 3 is a side view of the veneer being pressed according
to the method described in FIG. 1;
[0018] FIG. 4 is a perspective view of a lap joint on a finished
billet after it is removed from the press according to the method
described in FIG. 1;
[0019] FIG. 5 is a top view of a finished billet;
[0020] FIG. 6 is an isometric view of a system for detecting
features on a billet according to embodiments of the
disclosure;
[0021] FIG. 7 is another isometric view of a system for detecting
features on a billet according to embodiments of the
disclosure;
[0022] FIG. 8 is an isometric view of a scanning assembly according
to embodiments of the disclosure;
[0023] FIG. 9 is a schematic illustrating the operation of the
scanning assembly according to embodiments of the disclosure;
[0024] FIG. 10 is a flow chart depicting methods for manufacturing
LVL according to embodiments of the disclosure; and
[0025] FIGS. 11-13 show images of billets taken according to
embodiments of the disclosure alongside plots of intensity vs.
length of the billets.
[0026] The present disclosure describes generally to systems and
method for detecting features (e.g., slip sheets, lap lengths) on
laminated veneer lumber. Certain specific details are set forth in
the following description and FIGS. 6-13 to provide a thorough
understanding of various embodiments of the disclosure. Well-known
structures, systems, and methods often associated with such systems
have not been shown or described in details to avoid unnecessarily
obscuring the description of various embodiments of the disclosure.
In addition, those of ordinary skill in the relevant art will
understand that additional embodiments of the disclosure may be
practiced without several of the details described below.
[0027] In this disclosure, the term "wood" is used to refer to any
cellulose-based material produced from trees, shrubs, bushes,
grasses or the like. The disclosure is not intended to be limited
to a particular species or type of wood. The term "laminated veneer
lumber" (LVL) is used to refer to engineered wood product that uses
multiple layers of thin wood pieces (e.g., veneers) assembled with
adhesives. The term "billet" is used to refer to a semi-finished
LVL product. The term "lap joint" is used to refer to a joint
formed when one piece of veneer is placed partly over another and
bonded. The term "lap length" is used to refer to the length of a
lap joint. The term "slip sheet" is used to refer to a feature
encountered in LVL manufacturing in which two pieces of veneer
intended to form a lap joint have failed to overlap.
[0028] FIGS. 6 and 7 are isometric views of a system 600 for
detecting features in an LVL billet according to embodiments of the
disclosure. The system 600 may include a frame 602 to support
equipment for scanning the billet to detect features. In some
embodiments, the frame 602 includes upper components 604, lower
components 606, and side components 608. In the embodiment shown,
the upper components 604 are arranged in a substantially parallel
configuration. The lower components 606 are located a distance from
the upper components 604. The lower components 606 are also
arranged in a substantially parallel configuration. The side
components 608 connect the upper components 604 to the lower
components 606. The frame 602 can be constructed from any
conventional material known to those of ordinary skill in the art.
Additionally, the components of the frame 602 may be arranged in
other configurations that are different from the specific
configuration shown in FIGS. 6 and 7.
[0029] The frame 602 supports a scanning assembly 610. An
embodiment of the scanning assembly 610 is shown in more detail in
FIG. 8. The scanning assembly 610 may include a platform 802 for
receiving an LVL billet (not shown in FIG. 8) for scanning. An
x-ray generator 804 may be positioned above the platform 802 so
that a beam of radiation generated by the x-ray generator 804 is
directed toward a first planar surface on the LVL billet when the
LVL billet placed on the platform 802. In the embodiment shown, the
x-ray generator 804 is an x-ray tube; however, radioactive isotope
sources of x-ray radiation may also be used. The scanning assembly
610 may further include a collimator 806 which serves to narrow the
beam generated by the x-ray generator 806. In FIG. 8, the
collimator 806 is shown as a box extending through the platform
802. An x-ray detector (not visible in FIG. 8) is positioned inside
the box on the side of the platform 802 opposite the x-ray
generator 804.
[0030] FIG. 9 is a schematic which illustrates the operation of the
scanning assembly 610 according to embodiments of the disclosure.
Referring to FIG. 9, the x-ray generator 804 generates a beam of
radiation (shown as dotted lines 902) which is narrowed and
directed by the collimator 806. The beam 902 is projected toward a
billet 904 having a first planar surface 906 and a second planar
surface 908. An x-ray detector 910 is positioned below the billet
904 to measure the intensity of the beam 902 after passing through
the billet 904. In some embodiments, the x-ray detector 910 may be
a linear array detector or any other device that is suitable for
the purpose of x-ray detection known to one of ordinary skill in
the art. The x-ray detector 910 is connected to an image processor
912 (e.g., any standard computer suitable for such use), which
generates an image based on the intensity measured by the x-ray
detector 910.
[0031] The generated image represents a measurement of the absolute
density of the billet 904 across its length. According to
embodiments of the disclosure, the image may be analyzed to detect
features (e.g. lap lengths, slip sheets). The image generated may
be comprised of one or more pixels arranged in one or more columns.
In some embodiments, the entire image is used to identify features;
in other embodiments, the image may be cropped and the analysis
based on only a portion of the image.
[0032] According to embodiments of the disclosure, the first step
for the detecting features on the billet 904 includes calculating
the mean intensity of the one or more columns to create a
one-dimensional array along the length of the billet 904. The next
step includes fitting a second order polynomial to the one
dimensional array. To correct for background noise, the second
order polynomial may then be subtracted from the one-dimensional
array to create a difference array. The next step may involve
passing the difference array through a low pass filter to create a
filtered array. In some embodiments, a fourth order Butterworth
filter having a cutoff frequency that is one tenth of the sample
resolution (the rate at which images are captured) may be used for
this step. The final step involves performing a peak and valley
search on the filtered array to identify overlaps or gaps on the
billet 904. Overlaps may be used to identify and measure lap
length. Gaps may be used to identify and measure slip sheets. Since
the x-ray beam is purposely oriented parallel to the overlap
features of the billet, the lap features are accentuated and easily
distinguished from normal background billet density variation.
[0033] In operation, systems and methods according to the
disclosure may be used (1) as a method of quality control to
eliminate products with slip sheets; or (2) to provide feedback to
optimize LVL manufacturing. FIG. 10 is a flow chart depicting
methods for detecting features in an LVL billet according to
embodiments of the disclosure. According to FIG. 10, veneers are
either peeled and dried onsite (step 1002), green veneers are
purchased (step 1004) and dried onsite (step 1008), or pre-dried
veneers are purchased (step 1006). The veneers are then graded
according to conventional processes (step 1010) and laid out and
prepared for pressing.
[0034] In embodiments related to quality control, the process
resembles conventional LVL manufacturing to some degree. An
adhesive is applied to the veneers (step 1012) and the veneers are
aligned or laid up (step 1014). The veneers are then pressed into a
billet (step 1016) using any type of pressing technology known to
those of ordinary skill in the art. In embodiments according to the
disclosure, a system for detecting features in an LVL billet (e.g.,
as shown in FIGS. 6 and 7) may be arranged at the outfeed of the
press to receive the billet and scan it using methods described in
the disclosure. The information obtained from the scanning may then
be used to detect slip sheets on billets and remove billets having
too many slip sheets or slip sheets whose size exceeds a threshold
value. The billets not removed may then by cut (step 1020) and
further processed (step 1022) according to conventional
methods.
[0035] In embodiments related to optimizing LVL manufacturing, the
information obtained from scanning may be used to detect slip
joints and lap lengths and change the LVL manufacturing process to
affect the production of these features. For example, the
information may be fed back to step 1016 to optimize pressing
cycles. Alternatively, the information may be fed back to step 1014
to alter veneer alignment. This scope of this disclosure is
intended to include other methods of optimizing LVL manufacturing
using the scanning information that may be apparent to those of
ordinary skill in the art.
[0036] From the foregoing, it will be appreciated that the specific
embodiments of the disclosure have been described herein for
purposes of illustration, but that various modifications may be
made without deviating from the disclosure. For example, some
non-essential steps may be eliminated from the procedure described
for image analysis. Aspects of the disclosure described in the
context of particular embodiments may be combined or eliminated in
other embodiments. For example, aspects related to embodiments
associated with quality control may be combined with those
associated with optimization of LVL manufacturing.
[0037] Further, while advantages associated with certain
embodiments of the disclosure may have been described in the
context of those embodiments, other embodiments may also exhibit
such advantages, and not all embodiments need necessarily exhibit
such advantages to fall within the scope of the disclosure.
Accordingly, the invention is not limited except as by the appended
claims.
[0038] The following example will serve to illustrate aspects of
the present disclosure. The example is intended only as a means of
illustration and should not be construed to limit the scope of the
disclosure in any way. Those skilled in the art will recognize many
variations that may be made without departing from the spirit of
the disclosure.
EXAMPLE
[0039] Thirty-eight specimens of LVL billets were tested using
systems and method according to the disclosure for detecting
features. Each of the thirty-eight billets was manufactured using
standard LVL processes and materials. The length of each billet was
approximately 10 feet.
[0040] A system having a scanning assembly similar to the one shown
in FIG. 8 was constructed and calibrated to measure absolute
density. Each billet was passed through the scanning assembly and
high resolution image was captured. For this specific test, each
image captured was 128 pixels wide (e.g., a 128 pixel scan line).
The billets were scanned at a length-wise resolution of 0.100
inches.
[0041] The images were then analyzed according to methods described
in this disclosure. A mean value was determined for each 128 pixel
scan to create a one-dimensional array. A second order polynomial
was then fit to the one dimensional array. The second order
polynomial may then be subtracted from the one-dimensional array to
create a difference array. The difference array was passed through
a low pass filter to create a filtered array. Finally, a peak and
valley search was performed on the filtered array to identify
overlaps or gaps.
[0042] FIGS. 11-13 show images of billets taken according to
embodiments of the disclosure alongside plots of intensity vs.
length of the billets. Comparing the image to the plot clearly
demonstrates that the peak and valley search is effective to detect
features on the billets tested. For example, in FIG. 11, methods
according to the disclosure correctly identified three overlap
locations and one gap locations. This information may then be used
to measure and identify slip sheets and lap lengths as described
above.
* * * * *