Method and apparatus for monitoring and inspecting strip edge

A method of monitoring and inspecting an edge of strip metal includes providing at least one image producer having a field of view that substantially frames the edge, using the at least one image producer to form a first series of images of the edge after the edge has been formed by a knife; and analyzing in real time the first series of images to determine the shear angle and/or the burr height of the edge.

BACKGROUND OF THE INVENTION 
The present invention relates generally to metal strip edge and, more 
particularly, to a method and apparatus for monitoring and inspecting in 
real time various characteristics of the strip edge. 
Strip metal is a commodity that is commonly produced by the metals 
industry. Typically, various operations must be performed on the metal 
strip before the strip can be processed into one or more final products. 
Operations typically performed on metal strip include edge-trimming, 
slitting, shearing and stamping operations. 
In a slitting operation, a wide, metal strip is cut into any suitable 
number of narrower strips. Likewise, in an edge-trimming operation, a 
metal strip of, usually, non-uniform width is trimmed to a desired width. 
Slitting and edge-trimming operations are typically performed by rotary 
cutting knives mounted, respectively, above and below the strip at a 
desired location for cutting or trimming same. In the above-noted 
operations, new edges for the metal strip are produced thereby. 
It is important for a number of reasons to obtain high-quality strip edges 
from the above-noted operations. For example, low-quality edges may 
subsequently crack or rust, or cause subsequent coating or welding 
problems, or reduce the "fit and finish" of the strip, all of which 
results in increased processing costs and scrap rates. 
In slitting and edge-trimming operations, the quality of the edge is 
usually dependent on the setting or positioning of the knives. For 
example, the upper knife can be adjusted vertically to create a desired 
amount of overlap with the lower knife. In addition, the lower knife can 
be adjusted horizontally to adjust the amount of clearance between the 
upper and lower knives. 
Customarily, the knives are initially positioned and subsequently adjusted 
according to settings which, from empirical experience with strip of the 
same thickness and metallurgical composition, are thought to be correct. 
In addition, the edges of strip produced by the knives are periodically 
manually and visually inspected to determine whether the knives are 
properly set and otherwise in good working order (e.g., the knife edges 
are sharp and defect-free). 
Because strip edge inspection has only been done periodically and not in 
real time, a number of strip metal coils may be processed before a problem 
with one or more of the knives is detected. This can lead to many of the 
strip metal coils being scrapped or reworked if the edge quality has 
become unacceptable. 
SUMMARY OF THE INVENTION 
The present invention provides a method and apparatus for monitoring and 
inspecting, in real time, various characteristics of strip edge that can 
be influenced by improper knife settings or worn or degraded knives. By 
continuously monitoring in real time the strip edge produced by the 
knives, the knives can be timely adjusted or replaced when they begin to 
operate outside of normal operating parameters, thereby preventing the 
unnecessary scrapping or subsequent re-working of the metal strip. 
According to a first aspect of the present invention, a method of 
monitoring and inspecting an edge of strip metal includes the following 
steps: providing at least one image producer having a field of view that 
substantially frames the edge; using the at least one image producer to 
form a first series of images of the edge after the edge has been formed 
by at least one knife; and analyzing in real time the first series of 
images to determine the shear angle of the edge. 
According to a dependent aspect of the present invention, the method of 
monitoring further includes the steps of: comparing the shear angle to a 
standard operating parameter for shear angle; determining whether the 
shear angle is within the standard operating parameter; and alerting an 
operator if the shear angle is not within the standard operating 
parameter. 
According to a second aspect of the present invention, an apparatus for 
monitoring and inspecting an edge of strip metal includes at least one 
image producer having a field of view that substantially frames the edge. 
The at least one image producer is operable to form a first series of 
images of the edge after the edge has been formed by at least one knife. 
In addition, the apparatus includes an analyzer that is connectively 
associated with said at least one image producer. The analyzer is operable 
to determine in real time the shear angle of the edge and to compare the 
shear angle to a standard operating parameter for shear angle. 
According to a third aspect of the present invention, a method of 
monitoring and inspecting an edge of strip metal includes the following 
steps: providing at least one image producer having a field of view that 
substantially frames the edge; using the at least one image producer to 
form a first series of images of the edge after the edge has been formed 
by at least one knife; and analyzing in real time the first series of 
images to determine the burr height of the edge. 
According to a fourth aspect of the present invention, an apparatus for 
monitoring and inspecting an edge of strip metal includes at least one 
image producer having a field of view that substantially frames the edge. 
The at least one image producer is operable to form a first series of 
images of the edge after the edge has been formed by at least one knife. 
In addition, the apparatus includes an analyzer that is connectively 
associated with said at least one image producer. The analyzer is operable 
in real time to determine the burr height of the edge and to compare the 
burr height to a standard operating parameter for burr height. 
By continuously monitoring and inspecting in real time various 
characteristics of strip edge, including shear angle and burr height, line 
operators will be able to determine when rotary knives need to be replaced 
or readjusted before poor edge-quality occurs in strip edge. Such 
monitoring and consequent knife replacement or adjustment will result in 
lowered reprocessing costs and scrap rates for strip edge. 
The present invention, together with further objects and attendant 
advantages, will best be understood by reference to the following detailed 
description, taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS 
The present invention is described below in terms of an edge-trimming 
operation for metal strip. However, it should be understood that the 
apparatus and method of the present invention may be adapted for use in 
any suitable operation wherein metal or other strip is processed such that 
a strip edge is formed thereby. 
Turning now to the drawings, FIGS. 1a-1c show a pair of rotary knives 10 in 
operational contact with a metal or other strip 12 to create a new edge 14 
therefor. As shown, the knives 10 are positioned with respect to each 
other such that a horizontal clearance X is defined therebetween. 
Each of the knives 10 is supported by a shaft 16 that is, in turn, mounted 
in a support block or arbor (not shown) by means of, for example, roller 
bearings. The strip 12 is typically disposed between the support blocks 
and is fed between the knives 10. 
As best shown in FIG. 1b, as the strip 12 moves into contact with the 
knives 10, the knives 10 initially penetrate or cut the strip 12. The 
region of penetration 18 into the strip 12 is typically called the "nick." 
As shown in FIGS. 1b and 1c, the knives 10 penetrate the strip 12 until the 
cutting forces exceed the ultimate tensile strength of the strip material 
and the strip 12 separates. The region of separation 20 of the strip 12 is 
typically called the "break." Thus, it can be seen that an edge-trimming 
operation typically has both a cutting and a shearing or fracturing 
component thereto. 
As will be appreciated by those skilled in the art, the depth of 
penetration into the strip 12 is determined by the ultimate tensile 
strength of the strip material and its relationship to the yield strength 
and the thickness of the strip 12. 
The quality of the edge 14 formed by the knives 10 can be affected by 
various conditions, including the relative positioning and operational 
characteristics of the knives 10, which are discussed in detail in a 
copending application (Our Docket No. 95-233) filed on Jan. 5, 1996, the 
contents of which are hereby incorporated by reference. Therefore, by 
continuously monitoring in real time the quality of the edge 14 formed by 
the knives 10, an operator will be able to timely determine when an 
adjustment in the positioning of the knives 10 is required or when the 
knives 10 need to be replaced. 
Edge quality can be monitored, for example, in terms of the burr 22 and the 
shear angle A of the edge 14 formed by the trimming process. As shown and 
discussed below, the shear angle A of a strip edge 14 is defined by the 
angle formed between the "nick" region 18 and the "break" region 20 of the 
edge 14. Typically, for high-quality edges 14, the shear angle A should 
remain relatively constant within certain operating parameters, which 
usually have been empirically determined over time. 
As shown and discussed in more detail below, burrs 22 are formed on trimmed 
edges 14 by, among other things, excess shearing or fracturing pressure 
being exerted on the edges 14 by the knives 10. This excess pressure can 
be caused by incorrect or inaccurate horizontal and/or vertical 
positioning of the knives 10 with respect to one another and the strip 12. 
Burrs 22 formed on strip edges 14 can cause safety and operational problems 
with the strip 12. For example, burrs 22 are often sharp and can 
consequently lacerate material handlers. In addition, depending on the 
application, many final products formed from the processed strip 12 cannot 
have large, or any, burrs thereon. Thus, if the burrs 22 are too large, or 
cannot be present at all on the strip edge 14, they must be subsequently 
removed by means of a deburring process, which increases productivity 
costs and reduces output. 
FIGS. 2 and 3 illustrate two preferred embodiments of the present invention 
used to analyze, respectively, the shear angle A and the burr 22 of a 
strip edge 14. FIGS. 2 and 3 are both intended to be similar to those 
shown in FIGS. 1a-1c. However, for clarity and ease of illustration, the 
knives 10 have been removed from the drawings. 
As will become apparent below, FIG. 3 differs from FIG. 2 only in the 
presence of a burr 22 on the edge 14 and the positioning of the image 
producer 24, light source 28 and analyzer 30. It should be appreciated 
that, depending on the specific edge-quality characteristics of the edge 
14 being monitored, the image producer 24 and the light source 28 may be 
positioned in various orientations to frame specific areas of the edge 14. 
As shown in FIG. 2, the nick region 18 and the break region 20 of the edge 
14 form a shear angle A with respect to each other. As shown, the line 40 
along the break region 20 forms the hypotenuse of a triangle having one 
side S.sub.1 and a second side S.sub.2. An angle of 90.degree. is formed 
between sides S.sub.1 and S.sub.2. Through the side-angle-side (SAS) 
geometric principle, the shear angle A can be derived if the lengths of 
sides S.sub.1 and S.sub.2 can first be determined. 
As also shown in FIG. 2, two image producers 24, such as video cameras, are 
positioned such that their fields of view 32 substantially frame the break 
region 20 of the edge 14. In a preferred embodiment, one image producer 24 
is positioned below the strip 12 and the other image producer 24 is 
positioned to the side of the strip 12. 
In addition, a light source 28 focuses an intense light beam 34 on the nick 
and break regions 18, 20 of the edge 14. The rest of the beam 34 extends 
into the relatively dark or "black" area of the background environment 36. 
Typically, due to the respective cutting and shearing phenomena that occur 
on an edge 14 during an edge-trimming operation, the nick and break 
regions 18, 20 of the edge 14 exhibit different light reflectivity 
coefficients. Thus, the nick region 18 of the edge 14 may be able to 
reflect a greater portion of the incident light beam 34 than would the 
break region 20, or vice-versa. The contrast between the reflectivity of 
the nick and break regions 18, 20 of the edge 14, and the relative 
non-reflectivity of the background environment 36, is utilized to provide 
the monitoring and inspection apparatus and method of the present 
invention. 
As the edge 14 is created by the knives 10 during the edge-trimming 
operation, the image producers 24 create a series of real-time images of 
the edge 14. The real-time images of the edge 14 contain a first "bright" 
area that corresponds to the nick region 18 or the break region 20, and a 
second, less "bright" area that corresponds to the other of the nick or 
break regions 18, 20. The "bright" areas are caused by the portion of the 
light beam 34 that is reflected by the nick and break regions 18, 20 of 
the edge 14. In addition, the images contain "dark" areas that correspond 
to the background environment 36. The "dark" areas are caused by the 
portion of the light beam 34 that is absorbed (i.e., not reflected) by the 
background environment 36. 
By measuring the lengths of the transition zones between the "dark" area 
that correspond to the background environment 36 and the "bright" or "less 
bright" areas that correspond to the nick region 18 of the edge 14--i.e., 
the "bright" or "less bright" areas that correspond to the break region 
20--, the dimensions of the sides S.sub.1 and S.sub.2 can be derived. As 
discussed above, once the lengths of the sides S.sub.1 and S.sub.2 are 
known, the shear angle A can be determined. 
As shown in FIG. 3, the apparatus and method of the present invention can 
also be used to measure the height of a burr 22 formed on the strip edge 
14 and extending below the bottom side 50 of the strip 12. 
In a preferred embodiment, at least one image producer 24, such as a video 
camera, is positioned such that its field of view 32 substantially frames 
the backside 52 of the burr 22. Preferably, the image producer 24 is 
positioned below and to the left of the strip 12. 
In addition, a light source 28 focuses an intense light beam 34 on the 
backside 52 of the burr 22. The rest of the beam 34 extends into the 
relatively dark or "black" area of the background environment 36 or onto 
the bottom side 50 of the strip 12. 
As can be ascertained, the backside 52 of the burr 22 will be able to 
reflect a large amount of the incident light beam 34, especially as 
compared to the relative non-reflectivity of the background environment 
36. The contrast between the reflectivity of the backside 52 of the burr 
22 and the relative non-reflectivity of the background environment 36 is 
utilized to measure the height of the burr 22. 
As the edge 14, and thus the burr 22, is created by the knives 10 during 
the edge-trimming operation, the image producers 24 create a series of 
real-time images of the edge 14. The real-time images of the edge 14 
contain a "bright" area that corresponds to the backside 52 of the burr 22 
and a "dark" area that corresponds to the background environment 36. The 
"bright" and "dark" areas are caused by the portions of the light beam 34 
that are, respectively, reflected by the backside 52 of the burr 22 and 
absorbed (i.e., not reflected) by the background environment 36. 
By measuring the length of the "bright" area that corresponds to the 
backside 52 of the burr 22, the height dimension of the burr 22 can be 
derived. As can be deduced, the outer dimension of the "bright" area will 
terminate at the beginning of the "dark" area corresponding to the 
background environment 36. 
As is known in the art, each of the images of the edge 14 formed by the 
image producers 24 is divided into a number of pixels. For example, a 
standard "frame grabber" forms images having 512 pixels along the 
horizontal and 512 pixels along the vertical. Thus, with respect to FIG. 
2, the images formed by the image producers 24 will be divided into a 
large number of "bright, "less bright" and "dark" pixels that define the 
transition between the nick and break regions 18, 20 of the edge 14 and 
the background environment 36. In addition, with respect to FIG. 3, the 
images formed by the image producer 24 will be divided into a number of 
"bright" and "dark" pixels that define the transition between the backside 
52 of the burr 22 and the background environment 36. 
The images produced by the image producers 24 are supplied to an analyzer 
30, which may be a PC-type computer. Although not shown, the analyzer 30 
may include peripherals connected thereto, including one or more display 
monitors, a keyboard and/or a trackball for operator use and interaction 
with the monitoring and inspection apparatus. 
As discussed below, the analyzer 30 is programmed to digitize the images of 
the strip 12, and to compare the digitized image information for the shear 
angle A and the burr height of the edge 14 to standard operating 
parameters therefor. 
The standard operating parameters for shear angle A and burr height may be 
derived from the line operator's own experience in processing the specific 
strip stock in issue. For example, by forming images of a high-quality 
edge, and comparing those images with other images formed for known, 
poor-quality edges having, for example, unsatisfactory shear angles and 
burr heights, a line operator may be able to broadly define a set of 
standard operating parameters for, among other things, shear angle and 
burr height for strip edge 14. 
If the digitized image information falls outside of the standard operating 
parameters for shear angle or burr height, the analyzer 30 alerts the line 
operator. The line operator may then independently determine whether the 
shear angle A or the burr height needs to be adjusted. If the shear angle 
A or the burr height does need to be adjusted, the knives 10 may then be 
repositioned, either automatically or manually, or replaced, depending on 
what is required to remedy the problem. If the knives 10 do not need to be 
adjusted or replaced, the image information that caused the alert to be 
given can be utilized by the analyzer 30 to narrow and thereby refine the 
standard operating parameters for the shear angle A and/or the burr 
height. 
On the other hand, if the analyzer 30 determines that the digitized 
information falls within the standard operating parameters, the knives 10 
are permitted to continue trimming the strip 12. 
As discussed above, the image information may be stored and subsequently 
used to generate a revised set of standard operating parameters for that 
particular strip 12 and process. Suitable software for handling the 
above-described information processing will be apparent to those in the 
data processing art, and does not directly form a part of the present 
invention. One suitable image processing software is available from 
Integral Vision Limited of Woburn Industrial Estate, Kempston, Bedford, 
Great Britain. 
It is anticipated that the above-described iterative process will in time 
result in accurate standard operating parameters being defined for, among 
other things, the shear angle A and the burr height of the edge 14. As the 
standard operating parameters are refined, the line operators will be able 
to rely on them exclusively to determine when the knives 10 in a line 
operation need to be repositioned or replaced. 
The edge characteristics discussed above (i.e., shear angle and burr 
height) are intended to illustrate the operation and capabilities of the 
present invention and are not considered to be comprehensive; many 
additional edge characteristics may be monitored and inspected by the 
present invention. 
The image producers 24 and light sources 28 utilized in the present 
invention may be oriented or positioned in any suitable manner to monitor 
and inspect one or more edge characteristics. To operate efficiently, the 
image producers 24 and the light sources 28 have to be positioned such 
that the relevant surfaces of the edge 14 are included within their 
respective fields of view. 
Further, depending on the application and the number of edge 
characteristics that are desired to be monitored and inspected, it should 
be appreciated that any suitable number of image producers 24 and light 
sources 28 may be used in the present invention. For example, two light 
sources 28 may be used with each single image producer 24, or vice-versa. 
The following instruments may be used in the present invention: the 
analyzer 30 may comprise a PC-type computer having at least a 66 Mhz 80486 
processor, 8 MB of RAM, 2 camera inputs, 16 digital input/output (24 Volts 
DC) and a 400 MB hard disk; the peripherals for the analyzer 30 may 
include a SVGA monitor, a keyboard and a mouse or trackball; the image 
producers 24 may comprise "TM-6" series CCD cameras having 75 mm lenses 
provided by Pulnix; and the light sources 28 may be "Type 800 Microlight" 
infrared illuminators provided by Dennard. 
The present invention, by monitoring in real time the various 
characteristics of strip edge, allows the knives 10 to be timely adjusted 
or replaced when they begin to operate outside of normal operating 
parameters. Such real-time monitoring of the strip edge may prevent the 
unnecessary scrapping or subsequent re-working of strip product. 
It should be appreciated that the apparatus and method of the present 
invention may be configured and conducted as appropriate for the 
application. The embodiments described above are to be considered in all 
respects only as illustrative and not restrictive. The scope of the 
invention is defined by the following claims rather than by the foregoing 
description. All changes which come with the meaning and range of 
equivalency of the claims are to be embraced within their scope.