Metal deforming – With indication of condition or position of work – product,... – Including deformation by simple bending
Reexamination Certificate
2001-02-08
2004-03-23
Jones, David (Department: 3725)
Metal deforming
With indication of condition or position of work, product,...
Including deformation by simple bending
C072S031110, C072S389300, C072S389500, C072S702000
Reexamination Certificate
active
06708541
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a bending angle measuring method and apparatus, and a bending method and bending angle controller utilizing the above bending angle measuring method and apparatus. More specifically, the present invention relates to a bending angle measuring method and apparatus in which an accurate bending angle can be measured by moving and positioning an angle detecting head to a portion suitable for measuring a bending angle. Particularly, the present invention relates to a bending method and bending angle controller in which a desired bending angle can be obtained accurately in consideration of a spring back amount in a bending process.
BACKGROUND ART
In general, in a bending machine such as a press brake provided with an NC device, driving mechanisms for a table drive shaft are disposed on both of right and left sides, respectively, and the NC device controls the respective driving mechanisms based on a depth value (D value) corresponding to a target angle to bend a workpiece to the vicinity of the target angle.
Here, the D value is a distance (i.e., distance between blades) between a punch and a die which corresponds to the target angle, and it is, in other words, a pressing stroke amount of a table which corresponds to the target angle. Moreover, the NC device can be classified into a type in which an operator directly inputs and sets the D value, and a type in which the operator only inputs the target angle and the NC device calculates and sets the corresponding D value based on the target angle.
In either type, if necessary, the operator operates a hand pulser (a pulse generator for manual operation) to finish (increase a bend of) the bent workpiece, so that a finished angle is placed within an allowable range.
In the bending machine, the workpiece whose bending process has ended is removed from the bending machine, and then spring-back inevitably occurs. Moreover, a bending angle spread by spring-back is the finished angle of the workpiece.
Therefore, during an actual bending process, instead of setting an angle to be originally finished as the target angle, the target angle needs to be set in consideration of the spring-back amount. For this purpose, it is necessary to grasp, in advance, the spring-back amount which is to be generated in the workpiece as a bending object.
In a conventional art, the operator uses the workpiece to first try bending the workpiece, and the spring-back amount is measured from the workpiece.
However, when considering conditions for accurately measuring the spring-back amount [(I) Pressing of the workpiece by NC is accurately performed until the target angle is obtained. (II) The bending angle of the workpiece during final pressing is accurately measured. (III) After applied pressure is removed, the bending angle of the workpiece in a completely unloaded state is accurately measured.], in a conventional method, it is difficult for operators other than experienced operators to accurately obtain the spring-back amount by performing an operation once or twice. Moreover, even when trying bending the workpiece many times, the spring-back amount is not necessarily accurately obtained. Therefore, in practice, it is considerably difficult to grasp the accurate spring-back amount beforehand, and set the target angle with the spring-back amount considered therein as the target angle. As a result, there is a problem that it is difficult to enhance a finishing precision of the workpiece.
On the other hand, the present applicant has proposed a so-called non-contact type bending angle measuring method and measurement apparatus in which the workpiece bent by the bending machine is irradiated with a laser light and a returned light is detected to measure the bending angle.
FIG. 1
shows one example of the non-contact type bending angle measurement apparatus proposed by the present applicant. As shown in
FIG. 1
, a bending angle measurement apparatus
507
is mounted on a bending machine
505
in which a punch P disposed on an upper table
501
and a die D disposed on a lower table
503
cooperate to bend a workpiece W to a desired angle, so that the bending angle can be measured immediately after the bending process without removing the workpiece W from the bending machine
505
.
As shown in
FIGS. 1 and 2
, the bending angle measurement apparatus
507
is constituted of a bracket
511
movable along a guide rail
509
extending parallel to the die D on the front surface of the lower table
503
, and a detecting head
513
attached to the bracket
511
. As shown in
FIG. 2
, the detecting head
513
is provided with a projector for irradiating the workpiece W with the laser light, and a pair of receivers for receiving the light reflected by the workpiece W, and the detecting head can rock centering on a rotation center Po in a certain angle range.
That is to say, as shown in
FIG. 3
, the detecting head
513
is rocked by a stepping motor
519
attached to a common shaft
517
. Additionally, an encoder
521
is attached to the shaft
517
on a side of the stepping motor
519
opposite to a side thereof on which the detecting head
513
is located.
In the bending angle measurement apparatus
507
, the workpiece W is irradiated with the laser light from the projector while the detecting head
513
is vertically rocked. The bending angle of the workpiece W is detected from a peak value of an amount of the light received by the pair of receivers, or a rotation angle of the detecting head
513
corresponding to a gravity center position obtained from an area of a peak waveform. Concretely, for a bending angle 2&thgr; of the workpiece W, as shown in
FIG. 4
, respective peak values &thgr;
1
, &thgr;
2
of a point at which the reflected light is received by the pair of receivers are measured, and the bending angle is obtained from the peak values &thgr;
1
, &thgr;
2
. That is to say, the bending angle is calculated as 2&thgr;=(&thgr;
1
+&thgr;
2
). Additionally,
FIG. 4
shows a case in which the bending angle is 90 degrees, the abscissa shows the angle by the encoder
521
, and the ordinate shows the received light amount.
Additionally, shapes of the workpieces W to be bent/worked have different bending widths, and are various. Additionally, the bending angle broadly ranges from an acute angle to an obtuse angle. Therefore, in order to accurately measure the bending angle, the detecting head
513
needs to be brought as close to a bent portion as possible. That is to say, the bending angle increases toward a tip end of a bent side because of an influences of sag or deflection of the workpiece W and an aimed angle cannot be obtained. Therefore, to measure the angle of the bent portion is most reliable.
However, the angle detecting head
513
constituted as described above rotatably rocks centering on the point Po as the rotation center with respect to the workpiece W, and can only move parallel to the die D along the guide rail
509
. Therefore, for a workpiece W bent at an acute angle or a workpiece W bent in a complicated manner, the detecting head
513
cannot be brought close to the bent portion. Particularly, with a workpiece W which interferes with the angle detecting head
513
, or a workpiece W which has a hole or a molded material, when the angle detecting head
513
is simply moved parallel to the die D, it is difficult to set the angle detecting head
513
in a predetermined angle detection position. Therefore, the bending angle measurement apparatus
507
constituted as described above cannot detect the accurate bending angle.
Consequently, in order to detect the bending angles of the workpieces having different bending widths and various shapes with a good precision, it is necessary to bring the angle detecting head close to the bent portion of the workpiece.
DISCLOSURE OF INVENTION
An object of the present invention is to solve the aforementioned problems of the conventional art, and provide a workpiece bending method and bending angle controller which can accurately measure a spring-back amo
Aoki Takayuki
Matsumoto Masateru
Tsuchiura Kenichi
Uchida Kazuyuki
Greenblum & Bernstein P.L.C.
Jones David
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