Numerically controlled pyramid roll forming machine

As a part to be contour formed passes through the rolls of a pyramid roll forming machine, the vertical position of the upper roll is continuously controlled. Specifically, upper roll position feedback signals are summed with position command signals and the resultant position error signals used to control hydraulic actuators. The hydraulic actuators, in turn, control the position of the upper roll. In an elongate pyramid roll forming machine (e.g. one designed to contour panels or plates) both ends of the upper roll are controlled such that the axis of the upper roll may be skewed with respect to the axes of the lower set of pyramid rolls, or lie parallel to the axes of the lower rolls. In such a machine the positions of the ends of the upper roll are continuously controllable as a part is being contour formed. In a narrow pyramid roll forming machine (e.g. one designed to contour structural parts) the vertical position of the upper roll alone is controlled, as opposed to controlling each end of the upper roll. In either case, synchronization is provided by controlling the rate of summation or comparison between position feedback signals and position command signals. Rate control is provided by sensing the rate of movement of the part through the pyramid roll forming machine and using the resultant rate information to control the rate of feedback and command position signal comparison. Part springback may be sensed and the resultant information used to modify the position errors signals prior to their being used to control the position of the upper roll.

BACKGROUND OF THE INVENTION 
This invention is directed to metal forming machines and, more 
particularly, to pyramid roll forming machines. 
There are two basic types of pyramid roll forming machines extensively used 
by industrial organizations to contour parts. The first type is used to 
contour structural elements, such as stringers, ribs, stiffeners etc., and 
comprises a set of narrow, interchangeable, profiled rolls mounted on 
short shafts cantilevered from a drive housing. The second type is used to 
contour sheet metal and plate and comprises a set of long, cylindrical, 
rolls suspended between drive housings located at each end of the rolls. 
These elongate rolls are normally not changed, and must be of a diameter 
sufficient to keep roll deflection to a minimal amount under forming 
loads. This deflection restriction severely limits the capability of such 
machines to contour form in environments where the roll diameter cannot be 
allowed to exceed a maximum amount, e.g. 12 inches, because of the nature 
of the desired contour. The prior art, however, has overcome this 
restriction by providing an arrangement wherein reinforcing roll sets are 
arranged in a semi-planetary manner about small diameter work rolls. The 
semi-planetary reinforcing roll sets prevent the small diameter pyramid 
rolls from deflecting by an excessive amount. Regardless of the 
longitudinal length of the rolls (e.g., narrow for shaping structural 
elements or elongate for forming sheet and plate), all pyramid roll 
forming machines include three horizontally arrayed forming rolls that 
form a pyramid when viewed from an end. The pyramid includes two lower 
rolls and an upper roll having its axis located vertically above, and 
horizontally between, the axes defined by the lower rolls. Usually, the 
lower rolls are fixed in position and the upper roll is vertically 
movable. 
As noted above, the rolls of pyramid roll forming machines designed to bend 
structural elements are relatively narrow. Contrawise the rolls of pyramid 
roll forming machines designed to bend relatively large sheets or plates 
are elongate and the position of the upper roll is controlled at both 
ends. In the past, jack screws, hydraulic cylinders and the like have been 
used to control the position of the upper forming rolls of such machines. 
Indicating dials, adjustable position stops and the like have been used in 
conjunction with such control subsystems to indicate and assist in 
controlling the position of the upper roll. Because of the high roll 
forces involved, these adjusting arrangements have been primarily designed 
for load carrying ability, rather than precision. As a result, part 
accuracy and process reliability have suffered. 
Further, in the past, pyramid roll forming machines have been best suited 
for producing relatively simple curved parts. Specifically, under variable 
contoured parts have been produced using prior art pyramid roll forming 
machines, the technique used to control such machines to produce such 
parts has been costly, time consuming and unreliable. More specifically, 
in the past, variable contoured parts have been produced by prior art roll 
forming machines by frequently starting and stopping the rolls as the part 
has progressed through the machine. This start-stop action has been 
required on both narrow and elongate machines to allow the operator time 
to manually vary the position of the adjustable forming roll. Conical part 
contours (as opposed to cylindrical part contours) have been produced on 
elongate roll forming machines in a generally similar fashion, i.e., using 
a start-stop technique and manual adjustment at each end of the adjustable 
elongate roll. Obviously, manual roll adjustments are time consuming, 
whereby the resultant parts are expensive to produce. Moreover, it is 
extremely difficult, and in many cases impossible, to reliably manually 
reproduce the position of the adjustable forming roll when more than one 
part is to be formed. As a result, usually, expensive contoured templates 
or gauges must be formed for the operator's use. And, frequently, multiple 
roll passes must be made before the desired contour is achieved. 
Even more importantly, in the past, the productivity of prior art pyramid 
roll forming machines has been relatively low, particularly when the 
machines are used to create only a small number of each of a variety of 
different parts; even through the parts are similar and, a start-stop 
technique is not required. Low productivity is a direct result of the 
prior art requirement that the vertical position of the upper roll be 
manually adjusted prior to each different part being formed. 
Therefore, itis an object of this invention to provide a method of and 
apparatus for improving the flexibility and capability of pyramid roll 
forming machines. 
It is a further object of this invention to provide a method of and 
apparatus for improving the versatility and productivity of pyramid roll 
forming machines. 
It is another object of this invention to provide a new and improved 
pyramid roll forming machine suitable for forming a wide variety of part 
contours and shapes. 
It is a still further object of this invention to provide a new and 
improved pyramid roll forming machine adapted to create cylindrical, 
elliptical, conical and varying conical parts. 
It is a still further object of this invention to provide a numerical 
control method of operating a pyramid roll forming machine. 
SUMMARY OF THE INVENTION 
In accordance with this invention, a numerically controlled pyramid roll 
forming machine and method of operation of the machine is provided. In its 
least complicated form, the position of the upper forming roll of the roll 
forming machine, with respect to the lower forming roll is continuously 
controlled in a closed loop manner. The continuous control is such that 
the radius of curvature of the part being formed is controllable 
throughout the length of the part, whereby elliptical as well as 
cylindrical part curvatures can be created. 
The preferred form of the invention includes a position sensor that 
continuously senses the position of the upper roll. The sensed position 
information controls a position feedback signal that is compared or summed 
with a position command signal. Any error signals, produced as a result of 
the summation, are used to control a hydraulic actuator that controls the 
position of the upper roll. The command signals are, preferably, derived 
from a suitable numerical control signal source, such as punched or 
magnetic tape or cards. Further, the rate of movement of the part through 
the machine during contour forming is sensed and the resultant rate 
information used to control the rate of comparison between the position 
command signals and the position feedback signals so that desired contour 
changes occur at the appropriate part positions, as the part is being 
formed. 
In accordance with the invention, in pyramid roll forming machines wherein 
the forming rolls are elongate, the position of both ends of the upper 
roll are controlled. The end positions are controlled such that the axis 
of the upper roll lies parallel to the axes of the lower rolls, or 
transverse (skewed) thereto. When the upper roll is in a transverse or 
skewed position, conical or varying conical parts can be formed, depending 
upon whether the position of the upper roll remains fixed or is changed as 
the part is formed. (A varying conical part is one wherein the end 
curvatures are radially different, with the end radii changing as the part 
is being formed.) The preferred form of an elongate pyramid roll machine, 
formed in accordance with the invention includes position sensors for 
sensing the position of the ends of the upper roll. The resultant position 
information controls feedback signals that are summed with end position 
command signals. The results summations are used to control hydraulic 
actuators, which control the end positions of the upper roll. Information 
regarding the rate of part movement is used to control the rate of 
summation between the end position feedback signals and the end position 
command signals so that desired contour or radii changes occur at 
appropriate part positions. 
In accordance with a more sophisticated form of the present invention, one 
or more springback sensors sense the springback of parts as they exit from 
the pyramid roll forming machine. In this "adaptive" embodiment of the 
invention, the springback information produced by the sensors is used to 
modify the position error signals prior to the use of these signals to 
modify the position of the upper roll, such that compensation for part 
springback is provided. Preferably, in an elongate pyramid roll forming 
machine formed in accordance with the invention, a springback sensor is 
located near either end of a part as it exits from between the elongate 
pyramid rolls and the springback information developed by each sensor is 
used to modify its respective end position error signal. 
As will be readily appreciated by those skilled in the pyramid roll forming 
art, in some situations, springback control is neither feasible nor 
desirable. In such situations, obviously, the springback or adaptive 
embodiment of the invention cannot be used. On the other hand, in other 
situations, such an embodiment can be used to provide springback 
compensated parts. 
It will be appreciated from the foregoing summary that the invention 
provides a new and improved pyramid roll forming machine. Because the 
position of the upper roll of the roll forming machine is automatically, 
numerically controlled, i.e., controlled by command signals derived from a 
control source, as opposed to being manually controlled, overall 
productivity is greatly enhanced. Because the lateral position of the 
upper roll with respect to the lower rolls can be modified as a part is 
being contour formed, flexibility of part contour is greatly enhanced. For 
example, the invention can be used to create ellipitcal parts i.e., parts 
wherein the radius of curvature change as the part is being formed. 
Moreover, when the invention is used to control the ends of the upper roll 
of an elongate pyramid roll forming machine, conical and varying conical 
parts are readily formed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 is a pictorial diagram illustrating the general position of the 
forming rolls of an elongate pyramid roll forming machine and the path of 
a part 27 passing between the rolls. Specifically, FIG. 1 illustrates 
three elongate forming rolls -- two lower rolls 21 and 23; and an upper 
roll 25. As will be readily understood by those persons familiar with 
pyramid roll forming machines, both the upper roll and the lower rolls are 
driven by a suitable power source. The two lower rolls are rotatably 
mounted such that their axes remain fixed and lie in a common, generally 
horizontal, plane. Located between, and above, the two lower rolls 21 and 
23 is the upper roll 25. Thus, when viewed from an end, the two lowers 
rolls and the upper roll generally define a pyramid. 
In prior art pyramid roll forming machines, the upper roll 25 has been 
vertically moved, with respect to the lower rolls, by manually operated 
mechanical or hydraulic devices. In an elongate pyramid roll forming 
machine, vertical movement is created by raising or lowering the ends of 
the upper forming rolls and, in the past, normally taken place prior to a 
part 27 being moved through the forming rolls, between the upper roll, and 
the lower rolls, as illustrated in FIG. 1. As will be readily understood 
by those skilled in the roll forming art, the position of the upper roll 
with respect to the lower roll controls the radius of curvature (contour) 
of the resultant part. 
In the past, one primary disadvantage of pyramid roll forming machines has 
been their lack of flexibility. Specifically, primarily because of the 
manual control arrangement previously used, the contour of a part cannot 
be readily changed as a part is moved between the rolls. As a result, 
generally, only simple curved parts have been formed using pyramid roll 
forming machines. Varying contour parts have been formed, but only by 
interrupting the rolling cycle intermittently to provide for the manual 
adjustment of the position adjustable (e.g. upper) roll. The present 
invention is directed toward making pyramid roll forming machines more 
flexible and versatile. In essence, an apparatus formed in accordance with 
the invention includes a standard pyramid roll forming mechanism modified 
as herein after described, and a digital control subsystem. 
FIG. 2 is a front elevational view of a pyramid roll forming mechanism 31 
and includes a frame comprising a base 33 and a pair of housings 37, 
projecting upwardly from opposing ends of the base 33. The base 33 is 
adapted to support the mechanism on the floor 35 of a machine tool shop, 
for example. (Very large machines may incorporate a structural framework 
embedded in the shop floor in place of the base 33.) 
The housings 37 rotatably support an upper roll 41 and a pair of lower 
rolls 43 (only one of which is viewable in FIG. 2) in the manner more 
fully described hereinafter with respect to FIGS. 3 and 4. The upper and 
lower rolls 41 and 43 are each connected at one end by a universal joint 
45 or 47 to an associated drive shaft 49 or 51. The drive shafts 49 and 
51, in turn, are connected to a suitable power source, such as a gear box 
driven by an electric or hydraulic motor (not shown). Alternatively, a 
toggle gear arrangement can be used to drive the upper roll 41. 
Mounted atop each of the housings 37 is a hydraulic actuator 53. The shafts 
of the hydraulic actuators are connected to vertically moveable journal 
boxes adapted to rotatably support the ends of the upper forming roll 41 
as illustrated in FIG. 3 and hereinafter described. As a result, control 
of the hydraulic actuators 53 results in control on the ends of the upper 
roll 41 and, thus, control of the vertical position of the upper roll. 
FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 2 and 
illustrates the mechanism for controlling the position of the left end (as 
viewed in FIG. 2) of the upper roll 41 and a mechanism for sensing the 
position of the same end. Specifically, the left end of the upper roll 41 
is illustrated as rotatably mounted in a journal box 61. The journal box 
is mounted in the vertical slide of a frame 63. The frame 63 and a lower 
section, atop which the frame 63 is mounted, generally form the left 
housing 37. 
The hydraulic actuator 53 is mounted atop the frame 63 such that its rod 65 
is vertically arrayed. The lower end of the rod 63 of the hydraulic 
actuator is connected to the journal box 61. As will be readily understood 
by those skilled in hydraulics, the hydraulic actuator includes a cylinder 
67 within which a piston is mounted. The piston is affixed to the upper 
end of the rod 65. Upper and lower conduits 69 and 71 communicate with 
chambers formed in the housing 67, on opposite sides of the piston. In a 
conventional manner, the flow of hydraulic fluid into and out of the 
chambers, via the upper and lower conduits 69 and 71, cause the piston to 
move upwardly and downwardly, whereby the journal box 61 and the related 
end of the upper roll 41 are also moved upwardly and downwardly. Such 
movement is illustrated by the arrows 73 shown in the center of the upper 
roll 41. For purposes of discussion, up movement is illustrated as 
positive (+) and down movement is illustrated as negative (-). Control of 
fluid flow to the hydraulic actuator is provided by a standard servo 
value. 
The vertical position of the illustrated end of the upper roll is sensed by 
a position sensor 75. The position sensor 75 may take the form of a linear 
potentiometer or a linear variable differential transformer (LVDT), for 
examples. Regardless of its exact form, the positive sensor 75 includes a 
housing 77 and a linearly movable member or shaft 78. The position of the 
shaft with respect to the housing controls the level of an impedance or 
resistance, which in turn, controls the value of a signal. In the 
illustrated structure, the position sensor is in the form of a 
potentiometer having its housing affixed to the frame 63 and, its shaft 78 
vertically arrayed and connected at its lower end to the journal box 61 by 
a bracket 79. Thus, as the journal box 61 is moved up and down by the 
actuator 53, the shaft 78 is moved vertically. The position of the end of 
the upper roll, thus, controls the value of an electrical signal present 
on a conductor 81 connected to the potentiometer. 
In addition to a mechanisms for controlling the position of the illustrated 
end of the upper roll and sensing the position of that end, FIG. 3 also 
schematically illustrates a rate sensor 83. The rate sensor may take the 
form of a shaft encoder positioned so as to sense the rate of movement of 
a part 85 as it moves between the upper roll 41 and the lower rolls 43. In 
the mechanism illustrated in FIG. 3, the rate sensor is positioned beneath 
the upper roll and between the lower rolls. Preferably, the rate sensor 
includes a sensing element (e.g. serated wheel) that is spring loaded 
against the lower surface of the part 85. In this manner part travel, and 
thus part position, is monitored. As will be better understood from the 
following discussion the resulting part travel information is used to 
precisely relate changing upper roll position commands to part position. 
In accordance with the invention, the ends of the upper roll of an elongate 
pyramid roll forming machine may be displaced by unequal amounts, with 
respect to the lower rolls. When such an unequal displacement exists, a 
part moving through the pyramid rolls will have a different radius of 
curvature at either end. If the position of the ends remain fixed as the 
part is formed the radii, while being different, will be constant. If the 
position of the ends changes not only will the radii be different, they 
will also change. In any event, in order for differential end displacement 
to be accomplished, it will be appreciated that each end of the upper roll 
must be rotatable about a horizontal axis that lies orthogonal to the axis 
of rotation of the upper roll. As illustrated schematically in FIG. 4, 
this is accomplished by mounting the bearings 87, in which the upper roll 
41 is rotatably mounted, in spherically radiused housings. More 
specifically, the outer race of the bearing 87, in which the ends of the 
upper roll 41 are mounted for rotation about their longitudinal axis, is 
journaled in a spherical aperture 88 formed in the related journal box 61. 
As a result, the outer race is free to rotate about a horizontal axis, 
whereby compensation for the difference in vertical displacement of the 
ends of the upper roll 41, is provided. The universal joint 45 coupling 
the power source to the upper roll allows power to be applied to the upper 
roll even though it is unevenly displaced as its ends. 
It will be appreciated from the foregoing discussion that to this point a 
pyramid roll forming mechanism modified such that the position of the ends 
of the upper roll can be independently controlled has been described. Not 
only is independent end position control provided, information in the form 
of position feedback signals denoting the position of each end of the 
upper roll is also provided. Finally, part position information in the 
form of a rate signal is provided by the output of the rate sensor. 
The foregoing description, in general, pertains to an elongate pyramid roll 
forming machine, i.e., a roll forming machine suitable for contouring 
sheet and plate. However, it should be recognized that the description 
also applies to a narrow pyramid roll forming machine for forming 
structural shapes. In such a machine, FIG. 3 depicts a side elevational 
view of a mechanism wherein interchangeable profiled forming rolls 41a and 
43a (FIG. 11) are mounted on shafts extending in a cantilevered fashion 
from a single journal housing. The mechanism for controlling the position 
of the upper forming roll and monitoring part travel are identical to 
those described above for use with an elongate pyramid roll forming 
mechanism. (It should be noted the FIG. 11 is a simplified schematic, as 
opposed to a detailed pictorial view, of a narrow roll forming machine.) 
The following portion of the description describes a digital control 
subsystem that uses the signals produced by the position and rate sensors 
in combination with externally produced control signals to control the 
position of the ends of the upper roll in a manner such that a wide 
variety of parts can be readily formed by the invention. The raw parts can 
be elongate or panels or sheets, or structural elements having a variety 
of shapes including but not limited to Z-shapes (FIG. 11), L-shapes and 
T-shapes. The finished parts can have constant curvatures (e.g., 
cylindrical), or changing curvatures (e.g., elliptical). If the parts are 
sheets or panels, the radius of curvature at either end can be made equal 
or unequal (e.g., conical or varying conical). A block diagram of an 
overall pyramid roll forming machine formed in accordance with the 
invention and including a suitable control subsystem is illustrated in 
FIG. 5, and hereinafter described. 
The system illustrated in FIG. 5 includes a controller 91 connected to 
receive position control signals produced by a control signal source 93. 
The control signal source may be a punched or magnetic tape or card 
reader, for examples. Regardless of its exact nature, the control signal 
source produces position control signals adapted to control the position 
of the upper roll in the manner herein described. The controller 91 is 
also connected to the rate sensor 83 so as to receive the rate signals 
produced or controlled by the rate sensor. In addition, assuming an 
elongate pyramid roll forming mechanism is being controlled, the 
controller receives the end position feedback signals produced or 
controlled by the end position sensors 75. The controller, in essence, 
produces end position command signals based on the position control 
signals and compares the end position feedback signals with the end 
position command signals. End position error signals produced as a result 
of such comparison are used to control servo valves, which control the 
volumetric flow of hydraulic fluid to the hydraulic actuators 53 
controlling the position of the ends of the upper roll 41. A simplified 
illustration of a suitable comparator is illustrated in FIG. 6. 
Specifically, FIG. 6 illustrates an electrical summing junction 99 adapted 
to sum position feedback signals having a voltage falling in the range of 
from 0 to -X volts with position command signals having a voltage falling 
in the range of from 0 to +X volts. The outputs of the summing junction 99 
forms the error signal applied to the related servo valve. Obviously such 
a summation of comparison is performed for each end of the upper roll when 
the upper roll is an elongate roll that is controllable at either end. On 
the other hand, in the case of a pyramid roll forming machine designed to 
roll structural elements only a single summation or comparison is 
performed. In this regard, the controller (FIG. 5) would only receive 
single position control signals for controlling the position of the upper 
roll, not a pair of signals for independently controlling the ends, and 
the position of the upper roll would be sensed by a single sensor, not a 
pair of sensors adapted to sense the position of the end of an elongate 
roll. 
An illustration of a more complete and detailed subsystem for carrying out 
the comparison step, illustrated in simple form in FIG. 6, is illustrated 
in FIG. 9 and hereinafter described. However, prior to describing this 
subsystem a description of the springback sensors illustrated in FIGS. 7 
and 8 is first presented, since these sensors, if utilized, produce or 
control signals used in the subsystem illustrated in FIG. 9. 
FIGS. 7 and 8 illustrate a uniplanar sensor 121 suitable for sensing the 
contour of a part as it exists from between the forming rolls. Preferably, 
as illustrated in FIG. 2, a sensor of this nature is mounted near each 
part edge when a panel or sheet is being contour formed. Regardless of how 
many, and were mounted, the sensors sense springback automatically. 
Springback, of course, is the tendency of a part to return to its original 
shape after being formed. The sensors sense the amount of springback that 
occurs by measuring actual part curvature, after part contouring has taken 
place. 
The uniplanar sensor 121 illustrated in FIGS. 7 and 8 comprises a sensor 
body 123. A small roller 125 is located at the lower corner of each end of 
the sensor body 123. The axes of rotation of the rollers 125 is parallel 
to the longitudinal axis of the sensor body 123 and the sensor body is 
supported in the manner hereinafter described such that its longitudinal 
axis lies parallel to the direction of movement of the part 85 being 
contour formed. The rollers are, thus, separated in the direction of 
movement by a predetermined span, ten (10) inches, for example. This span 
establishes a cord of length L (FIG. 8). Mounted in the exact center of 
the sensor body 123 is a linear variable differential transformer (LVDT) 
127, or some other form of linear transducer. The probe of the LVDT 127 is 
located orthogonal to the cord of length L and projects so as to intersect 
the part 85 midway between the rollers 125. A suitable spring (not shown) 
forces the probe against the part and a suitable limiting mechanism (also 
not shown) prevents the probe from leaving the LVDT when the sensor is not 
in use. 
The signal controlled by the linear variable differential transformer is 
related to part radius by the following equation: 
##EQU1## 
where: H = the arc length of the cord joining the rollers; 
L l = the cord length; and, 
R = the contour radius. 
It should be noted that the span of the sensor body does not necessarily 
need to be 10 inches. A longer or shorter span may be used. In this 
regard, improved sensitivity will result if a longer span is used; 
however, transportation signal lag will increase. The opposite result 
occurs if a shorter span is used; that is, sensitivity is decreased and 
transportation lag reduced. 
In order for the information produced by the LVDT 127 to be usable, it must 
be related to some known position. This is accomplished in the present 
invention by a locating assembly 129 that maintains the rear roller 125 a 
fixed distance from the horizontal centerline of the exit lower roll 43. 
The locating assembly 129 comprises a link 131 having a U-shaped apertured 
end pinned to an upward projection forming a part of the sensor body 123. 
The upper projection lies on the side of the LVDT 127 nearest to the 
pyramid rolls. The upper projection is pinned to the U-shaped aperture in 
the link 131 by a pin 133 having a longitudinal axis lying parallel to the 
longitudinal axes of the lower rolls. The other end of the link 131 is 
connected by a pin 135 to a pair of flanges 137 projecting outwardly from 
an upper support channel 139 lying above the part 85. The upper support 
channel extends between the housings 37 and, thus, spans the part as it 
exists from the pyramid rolls. The pin 135 also has an axis that lies 
parallel to the axes of the lower rolls. While the flanges 137 are shown 
as located in a fixed position along the longitudinal length of the upper 
support channel 139, obviously, the flanges may be position adjustable, or 
the support channel may include a plurality of flanges to which the link 
131 may be pinned. 
It will be appreciated that the locating assembly, best illustrated in 
FIGS. 7 and 8, accurately locates the uniplanar sensor in the direction of 
part movement. It also will be appreciated that because of the way in 
which it is supported, the uniplanar sensor 121 may weight down the part 
85 in the region where the sensor rides on the part. In order to prevent 
the sensor weight from distorting the part and,thus, the output of the 
sensor (or similarly, in the case of thin parts, to prevent the part from 
distorting as a result of its own weight when extending from the rolls, 
and causing the sensor to provide a false contour indication) a part 
support mechanism 141 may be located downstream of the sensor. The part 
support mechanism is attached to a lower support channel 143, lying 
beneath the part 85, and extending between the housings 37. Thus, the 
lower support channel lies parallel to the lower rolls. 
The part support mechanism 141 includes a support block 145 affixed to the 
lower support channel 143. The support block supports a bracket 147 lying 
generally vertical. Angularly extending outwardly from the bracket 147, in 
the direction of part movement, is a support arm 149. The support arm 149 
is pinned by a pin 151 to the bracket 147 so that the support arm is 
movable about an axis lying generally parallel to the axes of the lower 
rolls 43. The support arm may be spring loaded to support part and/or 
sensor weight. Alternatively, in the case of heavy duty applications, 
pneumatic or hydraulic cylinders may be used to apply the needed force to 
the support arm 149. Rotatably mounted in the outer end of the support arm 
149 is a roller 153. The roller 153 is mounted so as to rotate in the 
direction of movement of the part 85. Preferably, the loading of the 
support arm 149, either by spring or other sources, is just adequate to 
compensate for the weight of the part and the uniplanar sensor 121, so as 
not to allow the part to elastically distort from its true contour. 
Turning now to a description of the end position control subsystem 
illustrated in FIG. 9; it is first pointed out that a subsystem of this 
nature is needed to control the position of each end of the upper roll 41 
in an elongate pyramid roll forming machine formed in accordance with the 
invention. In a narrow pyramid forming machine, i.e. one directed to 
contouring structural elements as schematically illustrated in FIG. 11, of 
course, only a single such subsystem is needed. 
The end position control subsystem illustrated in FIG. 9 includes a command 
memory 201 suitable for storing the position signals produced by the 
control signal source 93. Preferably, the command memory 201 sequentially 
receives and stores data blocks completely describing a part shape in one 
continuous input using wellknown digital data techniques. As the 
information contained in each control signal block is needed, the data 
(control commands) is transferred from the memory to a comparator 203. The 
comparator continuously compares the incoming control commands with the 
last control commands produced by a position memory 205. The position 
memory contains the current axes position commands present in the 
preceeding data block. The position memory is continuously updated in the 
manner hereinafter described, as succeeding data blocks become active. In 
this regard, if a new control command and the current command are or 
become unequal, the comparator 203 produces two signals. One signal is a 
UP/DN control signal that is applied to the position memory 205. The UP/DN 
signal indicates the direction in which the position of the upper forming 
roll axis is to change, i.e., up or down with respect to the previous 
position, based on the direction of the difference between the control 
command and the current command. 
The second output of the comparator is an equal/unequal signal that is 
applied to one input of a two-input AND gate 207. The rate signal 
controlled by the rate sensor 95 is applied to the second input of the AND 
gate 207. When the comparator determines that the new control command and 
the current command are unequal, the equal/unequal signal enables the AND 
gate 207. When enabled, the AND gate applies the rate sensor signal to the 
position memory 205. This signal, which is in the form of a pulse train 
having a frequency related to the rate of part movement through the 
pyramid rolls, causes the position memory to search "up" or "down" as 
directed by the UP/DN control signal. As a result, the position memory is 
searched in the appropriate direction at a rate determined by the rate of 
part movement. Searching continues until the control command and the 
current command are equal. 
As the position memory is searched, it outputs a series of end digit 
commands, which are applied to a digital-to-analog converter 209. The 
digital-to-analog converter converts the end digit commands into analog 
commands that are applied to a summing junction 213, via a multiple 211 if 
the system includes and is using a springback sensor to produce adaptive 
control signals. The analog signals are used to control the movement of 
the related end of the upper roll in the summation manner generally 
illustrated in FIG. 6 and previously described. 
In summary, it will be appreciated at this point, from viewing FIG. 9 and 
the foregoing description, that as long as the related end of the upper 
roll is correctly positioned (i.e., positioned at the point determined by 
the control command being produced by the command memory), the comparator 
will generate an equal output and no UP/DN control signal. Thus, the AND 
gate 207 will not be enabled and the position memory will constantly 
product the same end digit command. When the position of the related end 
of the upper roll is to change, the control command changes and an unequal 
output signal is produced by the comparator 203. The unequal output 
enables the AND gate 207 and rate pulses are applied to the position 
memory 205. If the control command or new position is up from the actual 
command or present position, an up control signal is also applied to the 
position memory 205. Alternatively, if the new position is down from the 
present position, a down control signal is applied to the position memory 
205. In accordance with the received UP/DN and rate pulses, the position 
memory searches for an output (current command) that compares with the 
control command. As the searching takes place, the position memory outputs 
changing end digits commands that are used to move the end of the upper 
roll. When equality occurs, the end digit commands stabilize and upper 
roll end movement terminates. 
As will be obvious to those skilled in the art to which this invention 
relates, to this point, a hardwired system using discrete subsystems 
and/or components has been described. Obviously, a computer control system 
with the above described control functions contained in a software program 
will serve equally as well. 
Depending upon the nature of the part being formed (i.e., the material 
being used, the thickness of the material, the radius of curvature 
involved, the complexity of curvature changes, etc.), the use of a 
springback sensor arrangement of the type illustrated in FIGS. 7 and 8 may 
not be desirable. In this regard, in many situations, empirically 
developed springback coefficients included in the control program will 
provide adequate control of part contour. In any event, if desirable, the 
adaptive control signal produced by the springback sensor(s), positioned 
near one or both ends position controlled by the subsystem illustrated in 
FIG. 9, is (are) applied to the input(s) of an integrator(s) 213. The 
output(s) of the integrator(s) 213 is (are) applied through an 
amplifier(s) 215 to the input(s) of a correction control(s) 217. For 
purposes of discussion, this(these) input(s) is(are) designated q.sub.1. 
The correction control circuit(s) 217 receives a second signal designated 
q.sub.0. q.sub.0 is a contour value signal produced by the control signal 
source 93. This signal is calculated from desired part geometry and 
designates what the expected output of the sensors should be at any 
particular point in time. The correction control circuit computes a 
correction factor signal designated K in accordance with the algorithm: 
##EQU2## 
where: q.sub.0 and q.sub.1 are as indicated above; and, K.sub.0 equals an 
initial or preceding correction factor. While the foregoing algorithm is 
preferred, other algorithms based on a constant (offset) factor based on 
machine idiosyncracies plus a proportional (e.g. q.sub.o /q.sub.1 or 
q.sub.1 /q.sub.0) factor may be equally applicable, particularily in cases 
where very rapidly changing contours are involved, or where it is not 
desirable to include empirical springback coefficients in part program. 
The correction control 217 includes a memory that stores and continuously 
generates the correction factor signal, which is applied to the second 
input of the multiplier 211. Obviously, the contour reference values 
(q.sub.0) produced by the control signal source 93 are offset by an 
incremental amount equal to the transport delay in the system, i.e., the 
time required for a particular region of the contoured part to reach the 
uniplanar sensor 121, after exiting from between the pyramid rolls. Thus, 
the contour reference value signals (q.sub.0) come on line at the time a 
corresponding part increment reaches the sensor and is measured. 
In operation, initially, the correction control computes the q.sub.0 
/q.sub.1 ratio. If no previous correction factor is stored in memory, 
q.sub.0 /q.sub.1 is used as the initial correction factor. If a K.sub.0 is 
stored in memory q.sub.0 /q.sub.1 - 1 is added to K.sub.0 in accordance 
with the above algorithm. The next block of commands are then multiplied 
by the new correction factor, K, as they are received by the multiplier 
211. Obviously, a K value larger than unity increases the analog output of 
the digital-to-analog converter and a K value of less than unity decreases 
the output. K will continuously change as the part is formed until q.sub.0 
= q.sub.1. When this condition is satisfied, the desired part contour is 
being created. This last value of K is retained as the appropriate factor 
the remaining part length, and for succeeding parts (i.e., it is recorded 
for future use), unless subsequent changes in contour require the 
development of a new K. If a computer based control system is being used, 
it may be desirable to store the K values applied to each data block as 
the first part is contoured. Those stored values can then be used to 
generate a second part program refined by the springback variations 
experienced with the first part. In this manner springback coefficients 
can be fine tuned by the adaptive control system and the system relieved 
of the requirement to control the making of gross corrections. 
Turning now to the servo control portion of FIG. 9, as noted above, the 
output of the multiplier 211 is applied to one input of a summing junction 
213. As illustrated in FIG. 6 and previously described, the summing 
junction sums feedback signals with command signals. The output of the 
multiplier forms the command signals. 
The output of the summing junction 213 is connected to the input of a servo 
amplifier 215. The output of the servo amplifier is applied to a servo 
valve 217 adapted to control the flow of hydraulic fluid to the hydraulic 
actuator 53. The position of the upper roll is controlled by the hydraulic 
actuator. The related position sensor (potentiometer 75) monitors roll 
position in the manner previously described. The position sensor signal is 
applied through a buffer amplifier 223 to the second input of the summing 
junction 213. As a result a control servo loop using a position command 
signal and a position feedback signal is formed. The summing junction 213 
compares or sums the output of the multiplier 211 (the position command 
signal) with the position signal, as amplified by the buffer amplifier 
223, (the position feedback signal). As illustrated in FIG. 6, the 
multiplier output may vary between zero and +X volts, for example; and, 
the output of the buffer amplifier 223 may vary between zero and -X volts. 
When the absolute value of these signals is unequal, a positive or 
negative error signal (equal in value to the absolute difference between 
the two signals) is produced. This signal is used to control the servo 
valve 217. Specifically, the polarity of the error signal controls the 
direction of movement of the hydraulic actuator and the magnitude controls 
the amount of movement. More specifically, in a conventional manner, the 
servo amplifier 215 receives the error signal and outputs a current 
proportional to the error. The current is applied to the torque motor of 
the servo valve 217, causing the spool thereof to shift in accordance with 
the current level and polarity, as is well known in the machine tool art. 
As the servo valve changes position, hydraulic fluid causes the piston of 
the actuator 53 to move, whereby the position of the related end of the 
upper roll is changed. Maintaining the upper roll in the desired position 
is accomplished, preferably, by metering small amounts of fluid to the 
actuator as required to compensate for leakage and any mechanical 
deflection that occurs. 
Also illustrated in FIG. 10 is a scaling amplifier 225 connected to the 
output of the buffer amplifier 223. The output of the scaling amplifier is 
applied to a suitable display to provide a visual indication of the 
position of the upper roll. 
FIG. 10 is a block diagram of an alternative system for controlling the 
position of the ends of the upper roll of an elongate pyramid roll forming 
machine formed in accordance with the invention. The system illustrated in 
FIG. 10 is primarily designed for implementation in mini(or micro) - 
processor form, even though it could be implemented in hard wired form. In 
general, the FIG. 10 system is based on the subsystem illustrated in FIG. 
9 and previously described. However, it is implemented somewhat 
differently. In addition, because, in many instances, an adaptive 
arrangement, (i.e., one wherein springback sensed data is used to modify 
end command signals) cannot be used in certain environments, the system 
illustrated in FIG. 10 also provides for the manual modification of the 
command signals used to control the position of the ends of the upper 
roll. 
More specifically, the system illustrated in FIG. 10 comprises: a 
springback signal conditioner 301; a controller 303; a tape reader 305; a 
display 307; a controller-CNC roll signal conditioner 309; a manual input 
control 311; and, a controller-CNC roll interface 313. The controller-CNC 
roll interface receives shaft signals from a shaft position encoder, e.g., 
rate sensor; and, feedback signals from the end position transducers 
(potentiometers). The received signals are appropriately conditioned by 
the controller-CNC roll interface 313 and applied to the controller 303. 
In addition, the tape reader reads a control tape and, in accordance 
therewith, stores end position control signals in the controller's memory. 
Alternatively, part programs can be input manually, read from an auxillary 
disc storage source or received from a remote, large scale, host computer. 
The controller 303, in accordance with the end feedback and control 
signals, produces end command signals and applies them to the 
controller-CNC roll signal conditioner 309. The end command signals are 
suitably conditioned and, either adaptively modified if the system is 
using adaptive modification or not modified, as herein described, by the 
controller-CNC signal conditioner. The resultant signals are applied to 
the controller-CNC roll interface 313. The controller-CNC roll interface, 
in accordance with the received signals, produces servo commands that 
control the position of the ends of the upper roll. 
If the system is conditioned to adaptively modify the end command signals, 
the springback signal conditioner 301 receives signals from the LVDT's of 
the right and left springback sensors, i.e., the sensors located near the 
edges of the part being formed. The springback signal conditioner 
conditions these signals, generally in the manner illustrated in FIG. 9 
and previously described, and applies the signals to the controller-CNC 
signal conditioner, which appropriately modifies the end command signals 
prior to their application to the controller-CNC roll interface 313. 
As an alternative to adaptively modifying the end command signals based on 
springback data, the signals can be manually modified based on operator 
experience, or chart or table data. This result is obtained by the 
operator appropriately operating the manual input control, which may be in 
the form of a keyboard, for example. More specifically, when it is desired 
to modify the end command signals in accordance with, for example, an 
operator's experience with the type and thickness of the metal being 
contour formed, the operator appropriately conditions the manual input 
control. In accordance therewith, the manual input control applies signals 
to the controller 303. The controller, in turn, modifies the end command 
signals prior to their application to the controller-CNC roll signal 
conditioner. In addition, the manual input control can be utilized to 
manually control the position of the upper roll. In this case, the manual 
input control produces signals that override signals produced by the 
controller. The override signals cause the upper roll to move a 
predetermined position. This method of operation may be used, for example, 
to rapidly move the upper roll to an initial position prior to a part 
being contour formed, or to an open position to provide for ease of 
removal of a part, either subsequent to its being formed or because the 
part has become jammed between the rolls. 
A display 307, also illustrated in FIG. 10, is included to provide a means 
to display any desired information. For example, a display of one or both 
end positions at any desired point in time can be provided. 
While a preferred embodiment of the invention has been illustrated and 
described, it will be appreciated by those skilled in the art and others 
that various changes can be made therein without departing from the spirit 
and scope of the invention. For example, rather than hydraulic control 
systems for controlling the position of the ends of the forming roll, 
other types of position control mechanisms, such as electro-mechanical 
mechanisms, i.e., stepping motors, may be utilized. In addition, part 
travel sensors other than shaft position encoders, may be utilized, if 
desired. Also, position sensors other than LVDT's and linear 
potentiometers can be utilized to sense the position of the ends of the 
upper roll and the curvature of a part exiting from the machine, if 
desired. Hence, the invention can be practiced otherwise than as 
specifically described herein.