Metal deforming – With indication of condition or position of work – product,... – Including deformation by simple bending
Reexamination Certificate
2002-07-17
2004-09-28
Tolan, Ed (Department: 3725)
Metal deforming
With indication of condition or position of work, product,...
Including deformation by simple bending
C072S020100, C072S020200, C072S389300
Reexamination Certificate
active
06796155
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a plate thickness detection method, a plate thickness detector, a reference inter-blade distance detection method, and a reference inter-blade distance detector for a bending machine for bending a workpiece by causing a punch to make a relative stroke and to cooperate with a die in the bending.
In addition, the present invention relates to a bending method and a bending apparatus for directly detecting the relative stroke value of a punch to a die and controlling the relative stroke of the punch by a vertically movable displacement gauge which is provided in the die and protruded from the V groove of the die.
The present invention also relates to a bending method and a bending apparatus capable of conducting accurate bending by calculating a D-value in light of a change in the plate thickness of a workpiece which is generated during the bending.
BACKGROUND ART OF THE INVENTION
According to conventional bending, a nominal plate thickness is input to an NC device and a D-value for a desired bending angle is thereby calculated. An actual plate thickness, however, varies according to the difference in manufacturer or a lot and a desired angle cannot be often obtained.
Considering this, as disclosed in Japanese Patent Application Laid-Open No. 63-157722, the relative pressure of a punch against a die from the torque of a servo motor elevating a ram is measured, and a position corresponding to a rising point of torque is considered as a workpiece upper position so as to detect a plate thickness.
Further, as disclosed in Japanese Patent Application Laid-Open No. 6-74746, a plate thickness is measured by setting a point at which the difference between a linear scale value and an NC device instruction value occurs based on the backlash of a ball screw which drives a ram, as a reference point at which a punch contacts with a workpiece.
However, in the method disclosed in 63-157722, it is disadvantageously difficult to detect the rising of pressure for a thin workpiece.
Further, as in the case of the method disclosed in 6-74746, if a point at which the difference between a linear scale value and an NC device instruction value occurs based on the backlash is determined as a point at which a punch contacts with a workpiece, “an excessive lash” which causes a backlash to enable detection is necessary. This makes it disadvantageously impossible to apply this method to a hydraulic bending machine.
Meanwhile, as shown in
FIG. 1
, if a workpiece W is bent by a punch P and a die D cooperatively in a press brake, for example, as a bending apparatus, a ram position detection means
103
for detecting the upper and lower positions of a ram
101
is provided so as to measure the distance between the punch P and the die D to thereby obtain a predetermined bending angle. A D-value is calculated in light of die conditions, workpiece conditions and the like, the ram position detection means
103
controls the D-value to bend the workpiece W.
However, even if the predetermined D-value is calculated and the relative distance of the punch P to the die D is controlled to obtain the D-value, mechanical deflections such as the deflections of side plates, those of upper and lower tables and that of the die occur due to the bending reaction of the workpiece W during the bending. Unless these deflections are corrected, bending with accurate angle cannot be ensured. However, it is quite difficult to accurately calculate and correct these mechanical deflections.
To solve this, as disclosed in, for example, Japanese Utility Model Application Publication No. 6-49374, there is proposed a bending method for directly detecting a D-value without the need to consider mechanical deflections. That is, as shown in
FIG. 2
, this position detection means
105
has a vertically movable detection pin
109
protruded from a V groove
107
of a die D and provided in the die D to be always urged upward, and detects the vertical movement of the detection pin
109
using a displacement gauge
111
.
Therefore, if a punch P descends to thereby bend the workpiece W downward, then the lower surface of the workpiece W which is being bent is abutted on the detection pin
109
to press the pin
109
down. The descent of the detection pin
109
is detected by the displacement gauge
111
to thereby directly detect a D-value.
Even with the conventional art, however, it is difficult to accurately calculate the relative stroke value of the punch P to obtain a target bending angle because of the various characteristics of the workpiece W, e.g., spring-back by which if the workpiece W is unloaded after being bent, the bending angle recovers.
On the other hand, with both the method shown in 63-15772 and that shown in 6-74746 as described above, a phenomenon that the actual plate thickness of the workpiece changes (decreases) during bending occurs. According to each method, the D-value is calculated not in light of the decrease of the thickness but based on the detection of the position at which the punch contacts with the workpiece at the start of bending. Since the D-value is not calculated in light of the thickness change (decrease) after the bending completely starts, the method has a disadvantage in that a target angle cannot be accurately obtained.
The present invention has been made while paying attention to the above-stated conventional disadvantages and the object of the present invention is to provide a plate thickness detection method, a plate thickness detector, a reference inter-blade distance detection method and a reference inter-blade distance detector for a bending machine capable of accurately detecting the actual plate thickness of a workpiece during bending.
Further, the present invention has been made while paying attention to the above-stated conventional disadvantages and the object of the present invention is to provide a bending method and a bending apparatus capable of accurately calculating the relative stroke value of a punch for a target bending angle and carrying out bending with high accuracy.
DISCLOSURE OF THE INVENTION
To attain the above object, the invention is a plate thickness detection method for a bending machine causing a punch to make a relative stroke and bending a workpiece mounted on an upper surface of a die cooperatively by the punch and the die, characterized by relatively descending the punch from a reference position away from the die by a reference inter-blade distance; detecting a relative stroke quantity of the punch if a change in a displacement quantity of a displacement gauge provided in the die, always urged upward from a die V-groove, and measuring a distance to a lower surface of the workpiece is detected, or at a predetermined point after the detection, using a ram position detection means and detecting the displacement quantity of the displacement gauge at this time; and subtracting the detected relative stroke quantity from the reference inter-blade distance and adding the displacement quantity of the displacement gauge to the subtraction result, thereby detecting a plate thickness of the workpiece.
Further, the invention is characterized not only by the previously noted features of the invention, but also in that the reference inter-blade distance is a distance between the punch and the die at a top dead center before relatively descending the punch.
Further, the invention is characterized not only by the above-noted features of the invention, but also in that the reference inter-blade distance is calculated by mounting a workpiece having a known plate thickness on the die before actual bending, relatively descending the punch to detect the stroke quantity using ram position detection means and to detect the displacement quantity of the displacement gauge at this time, adding the plate thickness of the workpiece to the relative stroke quantity of the punch and subtracting the displacement quantity of the displacement gauge from the addition result.
To obtain the above object, the invention is a reference inter-blade distance detection
Hayama Osamu
Ikeda Hidekatsu
Imai Kazunari
Koyama Junichi
Omata Hitoshi
Amada Company Limited
Greenblum & Bernstein P.L.C.
Tolan Ed
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