Method of positioning a metal sheet for a sheetmetal working machine

• US 5,187,958 A
• Filed: 08/28/1991
• Issued: 02/23/1993
• Est. Priority Date: 12/29/1989
• Status: Expired due to Term

• Current Assignee: Amada Company Limited
• Original Assignee: Amada Company Limited
• Inventors: Sartorio, Franco, Prunotto, Gianpaolo
• Primary Examiner(s): Larson, Lowell A.
• Assistant Examiner(s): Gurley, Donald M.
• Application Number:
  US07/752,494
• Time in Patent Office: 545 Days
• Field of Search: 72/9-12, 72/420, 72/422
• US Class Current: 72/16.2
• CPC Class Codes: B21D 43/003 Positioning devices B21D28/04 and B21D28/265 take precedence; stops B21D43/26; centering moving strips B21D43/023
• CPC Class Codes: B21D 43/105 Manipulators, i.e. mechanical arms carrying a gripper element having several degrees of freedom
• CPC Class Codes: B21D 5/002 Positioning devices

Abstract

The method is of the type in which the metal sheet (W) is manipulated by means of a movable gripping member (G) of a manipulator robot controlled by a programmer (PC) according to a program for positioning successive lines of working of the metal sheet in correspondence with a pair of linear tools (16, 18).

The programmer (PC) starts the working program by transporting the metal sheet to the position which corresponds with the first virtual or imaginary working line (B_o). Sensors (S₁, S₂, S_y) detect the position of the virtual working line and signal to the programmer whether and to what extent the position of this virtual working line differs from the correct position. This is equivalent to the entering in the programmer of a datum relating to the displacement of the engagement point (C_o) of the gripping member from its theoretical engagement point (C) on the metal sheet.

The programmer moves the gripping member (G) on the basis of the error detected, repositions it relative to the metal sheet (W) at the theoretical engagement point (C).

Claims

1. A method of positioning a metal sheet which is initially flat between a pair of linear tools in which the metal sheet is manipulated by a movable gripping member of a manipulator robot controlled by a programmer according to a working program for positioning successive lines of working of the metal sheet in correspondence with the tools, comprising steps of:

a) establishing a preliminary, physically-detectable, virtual working line on the metal sheet;

b) providing the programmer with a spatial and angular coordinate of a theoretical engagement point at which the gripping member is to engage the metal sheet;

c) gripping the metal sheet by said gripping member;

d) moving the metal sheet by said gripping member so that the virtual working line is brought into parallel with the tools;

e) comparing the position of the actual engagement point of the gripping member with that of the theoretical engagement point when the virtual working line is in parallel with the tools, thereby deriving and storing a first position error;

f) rotating the gripping member and the metal sheet by a predetermined angle so as to bring a first actual working line into coincidence with the tools;

g) comparing the position of the actual engagement point of the gripping member with that of the theoretical engagement point, thereby deriving and storing a second position error;

h) correcting the first position error by means of corresponding movement of the gripping member and the metal sheet;

i) holding the metal sheet between the tools without working it and releasing the gripping member from the metal sheet;

j) moving the gripping member to the theoretical engagement point according to the first and second position error; and

k) carrying out the working program starting with the first actual working line.

2. A method according to claim 1, wherein the virtual working line is an edge of the metal sheet.

3. A method according to claim 2, a pair of position sensors spaced apart in a direction parallel to the tools is used for detecting the virtual working line, the sensors being situated in the plane in which the metal sheet lies.

4. A method according to claims 1, 2 or 3, wherein the gripping member is movable along at least two axes, a first of which is parallel to the tools and a second of which is perpendicular to the tools, and which is rotatable at least about a third axis movable with the gripping member and normal to a plane in which the sheet lies at the start of the working cycle, and wherein the first acutal working line is at the predetermined angle to the virtual working line in the plane, the gripping member moving along the first and second axes and about the third axis.

5. A method of positioning a metal sheet which is initially flat between a pair of linear tools in which the metal sheet is manipulated by a movable gripping member of a manipulator robot controlled by a programmer according to a working program for positioning successive lines of working of the metal sheet in correspondence with the tools, the gripping member being movable along at least two axes, a first of which is parallel to the tools and a second of which is perpendicular to the tools, and which is rotatable at least about a third axis movable with the gripping member and normal to a plane in which the sheet lies, comprising the steps of:

a) establishing a preliminary, physically-detectable, virtual working line on the metal sheet;

b) providing the programmer with a spatial and an angular coordinate of a theoretical engagement point at which the gripping member is to engage the metal sheet;

c) gripping and moving the metal sheet to a position sensor and detecting the virtual working line;

d) detecting an angular position error of the metal sheet about the third axis;

e) rotating the gripping member about the third axis to bring the virtual working line into parallel with the tools and thus correcting the angular position error;

f) detecting a first position error of the virtual working line and correspondingly of the actual engagement point of the gripping member relative to the theoretical engagement point in the direction of the second axis;

g) rotating the gripping member and the metal sheet about the third axis through a predetermined angle to bring a first actual working line into coincidence with the tools;

h) translating the gripping member and the metal sheet along the first axis by a distance which corresponds to the product of the first position error and the sine of the predetermined angle in a direction such as to return the theoretical engagement point to a correct centered position relative to the tools;

i) gripping the metal sheet between the tools and releasing the gripping member from the metal sheet;

j) comparing the coordinates of the theoretical engagement point with those of the actual engagement point of the gripping member and deriving therefrom a second position error;

k) moving the gripping member according to the first and second position error to bring the gripping member to the theoretical engagement point;

l) carrying out the working program starting with the formation of the first actual working line.

6. A method according to claim 5, wherein an angle of 90°

is selected as the predetermined angle between the first actual working line and the virtual working line.

7. A method of bending a metal sheet which is initially flat between a pair of linear tools in which the metal sheet is manipulated by a movable gripping member of a manipulator robot controlled by a programmer according to a working program for positioning successive lines of working of the metal sheet in correspondence with the tools, comprising the steps of:

a) establishing a preliminary, physically-detectable, virtual working line on the metal sheet;

b) providing the programmer with a spatial and an angular coordinate of a theoretical engagement point at which the gripping member is to engage the metal sheet;

c) gripping and moving the metal sheet so that the virtual working line is brought into parallel with the tools;

d) comparing the position of the actual engagement point of the gripping member with that of its theoretical engagement point when the virtual working line is in parallel with the tools, thereby deriving and storing a first position error;

e) rotating the gripping member and the metal sheet by a predetermined angle so as to bring a first actual working line into coincidence with the tools;

f) comparing the position of the actual engagement point of the gripping member with that of its theoretical engagement point, thereby deriving and storing a second position error; and

g) carrying out the working program with starting with the first working line, while correcting the working program according to the first and second error.