Abstract:
Object of the present invention is to provide a method or a system by which an operator without skills in bending operation can easily and quickly perform precise bending operations on a sheet workpiece by following skilled operator&#39;s experience, hints or data. To achieve this object, the method of this present invention comprises the steps of storing data for a shape of said part; storing data for a bending order for manufacturing said part from said workpiece; selecting tools for performing each of bending operations; storing data for the selected dies; storing bending press control data for controlling the operation of said press to performs the bending operations in said bending order; and storing bending operation support information for supporting an operator for performing the bending operation by using said bending press. The bending operation support information includes at least one of hints regarding operations of: attaching a protective tape on the shoulder of a die; arranging small tools on the bending press so that punch and die are laterally shifted from each other; attaching small die on a ram with a fixing tape; aligning the punch and die relative to each other in a longitudinal direction; determining the original point of one of the punch and die relative to the other; positioning the workpiece relative to the punch and die; positioning the workpiece relative to a back gauge device; and checking a dimension of a shape of the workpiece after a bending operation.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This is a continuation of U.S. patent application Ser. No. 09/482,893, filed Jan. 14, 2000, which is the continuation of U.S. patent application Ser. No. 09/082,005, filed May 20, 1998, which is a continuation of U.S. patent application Ser. No. 08/771,308 filed Dec. 20, 1996, the contents of which are expressly incorporated by reference herein in its entirety.  
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The present invention relates to a method of bending operations and a bending system using the same, and more particularly to a method of bending operations in a plate material such as sheet metal by using a bending press such as a press brake, and a bending system using that method.  
           [0004]    2. Prior Art  
           [0005]    When various parts or products with complicated shapes are manufactured by bending operation, various preparation steps have to be carried out before actual bending operation. Examples of such preparation steps are as follows: determining the order of bending operations along bending lines; arranging bending tools on a bending press; and adjusting the positions of the bending tools in the bending press. In fact, conventionally, enormous working hours has been wasted to carry out these preparation steps. Further, when a bending operation for manufacturing a specific product has been finished, the data concerning the preparation steps has been thrown away. Thus, even when products that are the same as or similar to the previous product are manufactured later, the preparation steps had to be carried out again.  
         SUMMARY OF THE INVENTION  
         [0006]    The object of the present invention is to solve the foregoing problems of the conventional method and system.  
           [0007]    Specifically, the object of the present invention is to provide a method and a system for bending operation in which various data concerning preparation steps for a particular bending operation are suitably stored in a memory so that they can be used in a subsequent bending operations for manufacturing parts having the same shape or similar shapes.  
           [0008]    Other object of the present invention is to provide a method or a system by which an operator without skills in bending operation can easily and quickly perform precise bending operations on a workpiece by following skilled operator&#39;s experience, hints, or data.  
           [0009]    To achieve the foregoing objects, according to a first aspect of the present invention, there is provided a method of generating data for manufacturing a product or a part with a predetermined shape by using a bending press that is provided with a detachable die. The method comprises the steps of:  
           [0010]    entering shape data relating to the part or product;  
           [0011]    entering a bending order for manufacturing the part or product from the workpiece;  
           [0012]    selecting tools for performing the bending operations in the bending order;  
           [0013]    entering die data for specifying the selected tools;  
           [0014]    entering bending press control data for controlling the operation of the press for performing each bending operation which is performed in the bending order; and  
           [0015]    entering bending operation support information for supporting an operator for performing the bending operation.  
           [0016]    The bending operation support information includes at least one of hints regarding the operations of:  
           [0017]    attaching a protective tape on the shoulder of a die;  
           [0018]    arranging small tools on the bending press so that punch and die are laterally shifted from each other;  
           [0019]    attaching a small die on a ram with a fixing tape;  
           [0020]    aligning the punch and die relative to each other in a longitudinal direction;  
           [0021]    determining the original point of one of the punch and die relative to the other;  
           [0022]    positioning the workpiece relative to the punch and die;  
           [0023]    positioning the workpiece relative to a back gauge device; and  
           [0024]    inspecting dimensions of a shape of the workpiece after a bending operation.  
           [0025]    According to a second aspect of the present invention, there is provided another method of manufacturing a part or a product with a predetermined shape by using a bending press that has a detachable die. This method comprises the steps of:  
           [0026]    entering shape data relating to the part or the product;  
           [0027]    entering a bending order for manufacturing the part or the product from the sheet metal:  
           [0028]    selecting tools for performing each of bending operations to be performed in the bending order;  
           [0029]    entering die data for specifying the selected tools;  
           [0030]    mounting the selected die on the bending press;  
           [0031]    entering bending press control data for controlling the operation of the bending press for performing each of the bending operations to be performed in the bending order;  
           [0032]    bending the sheet metal in accordance with bending press control data for each of the bending operations; and  
           [0033]    entering bending operation support information for supporting an operator who is to perform bending operations to manufacture a part or a product that has the same shape as or a shape similar to the part or the product produced in the foregoing bending step.  
           [0034]    According to a third aspect of the present invention, there is provided a still another method of manufacturing a part or a product having a predetermined shape by bending a sheet metal by a bending press. This method comprises the steps of:  
           [0035]    determining a bending order and tools for use to manufacture the part or the product in accordance with the shape thereof;  
           [0036]    storing the determined bending order and the tools in a computer memory;  
           [0037]    selecting the determined tools from a die storage;  
           [0038]    determining arrangement of the tools on the bending press;  
           [0039]    storing the determined arrangement of the tools in the computer memory;  
           [0040]    mounting the tools on a bending machine with the determined arrangement;  
           [0041]    determining an attitude of insertion of the sheet metal into the bending press in each of the bending steps to be performed in the bending order;  
           [0042]    storing the determined attitude of insertion of the determined sheet metal for each of the bending steps; and  
           [0043]    inserting the sheet metal with the insertion attitude into the bending press for each of the bending steps and bending the sheet metal along predetermined bending lines on the sheet metal by the bending press.  
           [0044]    According to a fourth aspect of the present invention, there is provided a system for generating data for manufacturing a part by bending a workpiece along a plurality of bending lines by a bending press that has detachable tools. The system comprises:  
           [0045]    a section that stores data for a shape of said part;  
           [0046]    a section that stores data for a bending order for manufacturing said part from said workpiece;  
           [0047]    a section that stores data for specifying the selected dies for each bending operation;  
           [0048]    a section that stores bending press control data for controlling the operation of said press to performs the bending operations in said bending order; and  
           [0049]    a section that stores bending operation support information for supporting an operator for performing the bending operation by using said bending press.  
           [0050]    In accordance with the present invention, various optimum steps (or procedures) relating to the bending operations, which are carried out by a skilled operator for manufacturing a predetermined part or a product, are stored in a computer memory as operation information for each part. Therefore a non-skilled operator can learn, from the computer memory, the stored optimum operation information for each part or product later and easily and quickly perform the optimum steps (or procedures) for manufacturing the part or the product by following the skilled operator. That is, even a non skilled operator can quickly start the bending operation without taking an excessively long time for standby operations (or preparation steps) for manufacturing the part or product.  
           [0051]    The term “part” in this specification means a product that is to be distributed in a market as well as a portion of the product.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0052]    [0052]FIG. 1 is a block diagram of an embodiment of a plate bending system according to the present invention;  
         [0053]    [0053]FIG. 2 is a flow chart of the overall operation of the plate bending system shown in FIG. 1;  
         [0054]    [0054]FIG. 3 is a flow chart showing a detailed operation of a step in the flow chart shown in FIG. 2, and specifically showing the operation of a step for manufacturing a new part or product in FIG. 2;  
         [0055]    [0055]FIG. 4 is a flow chart showing a detailed operation of a step in the flow chart shown in FIG. 3, and specifically showing the operation a step for performing an i-th bending operation on the plate to manufacture the new part in FIG. 3;  
         [0056]    [0056]FIG. 5 is a schematic view showing a part that is displayed on the screen of a terminal computer in step S 22  in FIG. 3;  
         [0057]    [0057]FIG. 6A and FIG. 6B respectively are a 2D unfold view of the shape of the part and a view of a table that shows bending lines and tools to be used, both of the views being displayed on the screen of the terminal computer in step S 23  shown in FIG. 3;  
         [0058]    [0058]FIG. 7A and FIG. 7B are views showing layout of tools to be used and operation support information relating to the layout, the views being displayed on the screen of the terminal computer in step S 25  and step S 26  in FIG. 3;  
         [0059]    [0059]FIG. 8 is a cross sectional view of a die and a back gauge device that are displayed on the screen of the computer terminal in relation to a alignment and an original-point determination operations in steps S 28  and S 30  in FIG. 3;  
         [0060]    [0060]FIG. 9A, FIG. 10A and FIG. 11A are schematic views showing attitudes of a workpiece with respect to tools on a bending press and operation support information relating to positioning of the workpiece with respect to the bending press, which are displayed on the screen of the terminal computer in step S 44  in FIG. 4;  
         [0061]    [0061]FIG. 9B, FIG. 10B and FIG. 11B are schematic views showing the parts with dimensions data and operation support information relating to the inspection of the dimensions, which are displayed on the screen of the terminal computer in step S 48  in FIG. 4;  
         [0062]    [0062]FIG. 9C, FIG. 10C and FIG. 11C are other schematic views showing the parts with dimension data and operation support information relating to the inspection of the dimensions, which are displayed on the screen of the terminal computer in step S 48  in FIG. 4;  
         [0063]    [0063]FIG. 12A is a flow chart showing a detailed operation of a portion of the operation shown in the flow chart of FIG. 2, and specifically the flow chart showing the operation when the same or a similar part is manufactured in FIG. 2;  
         [0064]    [0064]FIG. 12B is a flow chart showing a detailed operation of a portion of the operation shown in flow chart of FIG. 12A, and specifically the flow chart showing the operation for performing an i-th trial bending operation on a sheet metal in FIG. 12A;  
         [0065]    [0065]FIG. 13A and FIG. 13B respectively are a perspective schematic view and a schematic cross sectional view of a bending press used in an embodiment of the plate bending system according to the present invention; and  
         [0066]    [0066]FIG. 14 is an explanatory view for explaining value D, value L and value Yz in the bending press.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0067]    Examples of the present invention will now be described with reference to the drawings.  
         [0068]    [0068]FIG. 1 is a block diagram of a plate bending system according to the present invention. As shown in FIG. 1, the plate bending system according to this embodiment includes a factory office  30  for receiving from a customer an order for manufacturing a part or a product (a bent workpiece) with a predetermined shape and a plurality of bending stations  20  and  22  with bending presses. The banding stations receive from the factory office  30  instructions to manufacture the ordered part or product.  
         [0069]    The factory office  30  is provided with a server computer (hereinafter called a “server”)  31  having a data base  33 . The data base  33  in the server  31  stores a variety of data about parts which have been manufactured by the bending system, as will be described later in detail. A bar-code preparation apparatus  31   a  for preparing bar codes is connected to the server  31 .  
         [0070]    The first bending station  20  of the bending stations  20  and  22  has a first bending press  21  such as a press brake and a first computer terminal (hereinafter called a “terminal for a press” or simply called a “terminal”)  25 . The terminal  25  includes an NC unit for controlling the first bending press  21 .  
         [0071]    The first bending press  21  includes, for example, a C-shape frame  35 , as shown in FIGS. 13A and 13B. A plurality of punches  39  are disposed at the lower end of an apron  37   a , which is provided on an upper support plate  37  of the C-shape frame  35 , along a straight line running in the x-axis direction. Moreover, a ram  43 , which is movable vertically, is supported by a lower support plate  41  of the C-shape frame  35 . A plurality of dies  45  for bending a plate (hereinafter called a “workpiece”) W in cooperation with the punches  39 , are disposed at the top end of the ram  43  along a straight line running in the x-axis direction. That is, when the workpiece is inserted between the punches  39  and the dies  45  and then the ram  43  is moved upwards, the punches  39  and the dies  45  are mutually engaged to one another so that the workpiece W held therebetween is bent upward.  
         [0072]    Again referring to FIG. 1, connected to the terminal  25  are a keyboard  25   c  for entering data into the terminal  25 , a CRT unit (hereinafter called a “CRT”)  25   b  serving as a display unit for displaying data supplied from the terminal  25  and a bar-code reading unit (bar code scanner)  25   a  for reading bar codes made by the bar-code preparation apparatus  31   a  and providing the read bar code data to the terminal  25 . Here, data can be entered into the terminal  25  by using touch keys provided on the CRT screen as well as the keyboard  25   c.    
         [0073]    Similarly to the first bending station  20 , the second bending station  22  is provided with a second bending press  23  and a second computer terminal  27 . A keyboard  27   c , a CRT  27   b  and a bar-code reading unit  27   a  are connected to the terminal  27 . The server  31  of the factory office  30  and the terminals  25  and  27  of the bending stations  20  and  22  are connected through a network  29  to one another so as to allow mutual data communication therebetween.  
         [0074]    Referring to FIG. 2, the overall operation of the plate bending system will now be described.  
         [0075]    In step S 1 , various data concerning ordered part are received by the factory office  30 . Such data contains, for example, the part number of the ordered part and data on the shape of the part. The part number is, for example, a combination of symbols and numerals, such as “PT123a”. The symbol “PT” indicates the ordered part being a part of a complete product, and the numeral “123” specifies the type of the part, and the symbol “a” specifies the dimensions of the part indicated by “123”. The data on the shape of the part consists of data for a 3D perspective view of the ordered part, data for a 2D unfolded view of the same or data for 2D, three views of the same; the 2D, three views consist of a front view, a plan view and a side view. In step S 1 , such data for the ordered part are entered into the server  31 .  
         [0076]    In step S 2 , the server  31  performs a searches on the basis of the entered part number to see whether bending operation data for a part that is the same as the ordered part is stored in the data base  33 .  
         [0077]    When no data on the same part is in the data base  33 , an operator inputs into the server  31  the data on the shape of the ordered part in step S 3 . The data on the shape entered in step S 3  consists of data concerning a 3D perspective view of the ordered part, data concerning a 2D unfolded view of the same or 2D three views of the same. When data on one of the views are entered, the server  31  calculates data on two other views on the basis of the entered data by a predetermined calculation method. For example, if data for the 2D three views are entered, the server  31  calculates data for the 3D perspective view and 2D unfolded view.  
         [0078]    In step S 4 , the server  31  carries out a search on the basis of the part number to see whether data for bending operations for parts similar to the ordered part (i.e. similar parts) are stored in the data base  33 . For example, when the part number of the ordered part is “PT123a”, a search is carried out to see whether the data base  33  includes data for the parts designated by part numbers “PT123b”, “PT123c” and “PT123d” and the like.  
         [0079]    If it is detected in step S 4  that the data for the similar parts is stored in the data base  33 , the operation proceeds to step S 5 , where data for the similar parts are retrieved from the date base  33 . Moreover, in step S 5 , the retrieved data, data on the shape of the ordered part, and the part number of the ordered part are stored into the data base  33  together with information indicating the associated data is for a similar part. That is, in step S 5  the operator stores into the data base  33  the retrieved data, the part number of the ordered part, data on the shape of the ordered part, and the data indicating that the retrieved data item is data for a similar part, as a set of data.  
         [0080]    If no part number of a similar part is detected in step S 4 , the operation proceeds to step S 6 . In step S 6 , the data on the shape of the ordered part and the part number of the ordered part are stored in the data base  33  together with data indicating that the ordered part is a new part. That is, in step S 6 , the server  31  stores in the data base  33  the data indicating that the ordered part is a new part, the part number of the ordered part, and the shape of the ordered part as a set of data.  
         [0081]    In step S 2 , if the same part number as the part number of the ordered part is detected, the operation directly proceeds to step S 7 .  
         [0082]    In step S 7 , the bar-code preparation apparatus  31   a  connected to the server  31  prepares a bar code sheet that specifies the part number of the ordered part. The prepared bar code sheet is attached to an operation instruction sheet to be delivered to bending stations  20  and  22 .  
         [0083]    In step S 8 , it is determined whether data of all of the ordered parts has been processed. When all data have not yet been processed, the operation returns to step S 1 . If the process has been completed, the operation proceeds to step S 9 .  
         [0084]    In step S 9 , the factory office  30  assigns and delivers the operation instruction sheets to the bending station  20  or the bending station  22  in accordance with the skill of the operator at each bending station  20 ,  22  and with the availability of the bending stations. For example, an operation instruction sheet for a new part is delivered to a bending station at which a skilled operator is working, while an operation instruction sheet for the same or a similar part is delivered to a bending station at which a low skill operator is working.  
         [0085]    When the operation instruction sheet is received by each of the bending stations  20  and  22 , the operation proceeds to step S 10 . In step S 10 , the bar code attached to the operation instruction sheet is read by the bar-code reading unit  25   a  or  27   a . Thus, data for the ordered parts assigned to a bending station are retrieved from the data base  33  and transmitted to either one of the terminals  25  and  27 . As described above, when a ordered part assigned to a station is a new part, the retrieved data contains the part number of the ordered part, the shape of the ordered part, and information indicating that the ordered part is a new part. When the ordered part assigned is the same part—which means that the data for the same part as the ordered part has been stored in the data base  33 —, the retrieved data contain the part number of the ordered part and data for the same part retrieved from the data base and information indicating that the retrieved data is for the same part. When the ordered part assigned to a station is a similar part—which means that the data for part(s) similar to the ordered part has been stored in the data base—, the retrieved data contain the data for the similar part, the part number of the ordered part, and the shape of the ordered part, information indicating that the retrieved data is data for the similar part.  
         [0086]    In step S 11 , it is determined whether the assigned part is a new part, in other words whether the bending operation is for a new part, When the assigned part is a new part, the operation proceeds to step S 12 . In step S 12 , a new bending operation or new-part bending operation is performed as described in detail in the following with reference to FIGS. 3 and 4. On the other hand, when the ordered part is the same or a similar part, the operation proceeds to step S 13 , where a repeat (reiteration process) or a similar bending operation is performed as described in detail in the following with reference to FIGS. 12A and 12B. Then, the operation proceeds to step S 14 , where the overall operation is completed.  
         [0087]    Referring now to FIG. 3, the new-part bending operation performed in step S 12  will be described in detail. It is supposed that the new-part bending operation is performed in the first bending station  20 .  
         [0088]    As described above, when the assigned part is a new part, the data that the terminal  25  retrieves in step S 10  of FIG. 2 includes the part number of the ordered part, data for the shape of the part (i.e. data of the 2D three views, the 3D perspective view or the 2D unfolded view) and information indicating that the part is a new part.  
         [0089]    If, in step S 11  of FIG. 2, it is determined that the ordered part is a new part, the operation proceeds to step S 21 , where a guide program for a new bending operation is activated.  
         [0090]    In step S 22 , in accordance with the guide program, the shape of the ordered part as well as the part number of the ordered part and information indicating that the ordered part is a new part are displayed on the screen of the CRT  25   b . For example, a 3D perspective view  47  of the part with dimension lines for “ 600 ”, “ 700 ” and “ 50 ” as shown in FIG. 5 and/or a 2D unfolded view  49  of the part with bending lines B 1 , B 2 , B 3  as shown in FIG. 6A are displayed on the screen of the CRT  25   b . Moreover, a bending order/tool table  51  as shown in FIG. 6B are displayed on the screen of the CRT unit  25   b  together with the views of the part. In FIG. 6B, when the table initially appears on the screen, the bending line column, the tool column, and the tool length column are blank (not shown in the drawings).  
         [0091]    In step S 23 , the operator refers to, for example, the 3D perspective view  47  as shown in FIG. 5 and the 2D unfolded view as shown in FIG. 6A and determines a bending order in which a workpiece is bent along the bending lines B1, B2 and B3. Moreover, the operator selects tools (punches and dies) for bending the workpiece along the bending lines B1, B2 and B3. The determination of the bending order is performed by, for example, sequentially clicking the bending lines B1, B2 and B3 on the 2D unfolded view as shown in FIG. 6A with a mouse pointer and the like. As a result, each of the bending line numbers B1, B2, B3 are entered, in order of bending operation, into each line of the bending line column of the bending order/tool table  51  as shown in FIG. 6B. For example, as shown in FIG. 6B, if the bending lines are bent in order of B3, B2 and B1, bending line B3 is entered into the first line for the bending order  1 , bending line B2 entered into the second line for the bending order  2  and bending line B1 entered into the third line for the bending order  3 .  
         [0092]    Then, the operator determines tools for bending the workpiece along the bending lines B1, B2 and B3. Selections of the tools are performed by, for example, entering suitable die numbers into lines in the column for the tool number in FIG. 6B. In the example shown in FIG. 6B, punch P1 and die D1 are used for the bending along the bending lines B3 and B2, and punch P2 and die D2 used for the bending along the bending line B1. Thus, data of P=P1 and D=D1 are entered into each of the lines for bending lines B3 and B2, and data of P=P2 and D=D2 are entered into the line for bending line B1. For example, the data P1 and D1 indicate the punch number 402 and the die number 30286 (11) and, the data P2 and D2 indicate the punch number 14702 and the die number 30286 (10). To assist the selection of the tools, a menu for available tools may be displayed on the screen of the CRT so that the operator can select a suitable tool from the menu.  
         [0093]    Then, the lengths of the selected tools are determined and entered into the tool length column of the table  51 . For example, as the length of punch P1 and die D1, 835 mm is entered into the first and the second lines of the table, while 50 mm is entered into the third line thereof, as the length of the punch P2 and die D2, as shown in FIG. 6B. Then, the bending order/die table  51  are entered into a memory of the terminal  25  by suitable operation at the keyboard  25   c.    
         [0094]    In step S 24 , the operator selects tools (punches and dies) from a die magazine while referring to the bending order/die table  51  on the CRT screen  25   b . Then, the operator places and mounts the selected tools on the apron  37   a  and the ram  43  of the first bending press  21  by using his experience and skill.  
         [0095]    In step S 25 , the operator enters into the terminal  25  data for the arrangement of the tools (or the layout of the tools) on the apron  37   a  and the ram  43 . For this purpose, when a suitable key on the keyboard  25   c  is depressed, an image as shown in FIG. 7A appears on the screen of the CRT  25   b . Although omitted from the drawing, when the image of FIG. 7A initially appears on the screen, only figures showing the apron  37   s  and the ram  43 , central position O and a direction symbol  53  are displayed, while the other figures and characters are not displayed. After the foregoing screen is displayed, the operator enters symbols and/or figures of the punch P1 and die D1 into the terminal in such a manner, for example, that the central position of each figure is positioned away from the central position O by a distance of −500 mm, as shown in FIG. 7A.  
         [0096]    Moreover, description, “front-side mounting” or “reverse-side mounting” may be entered for each of the punch and the die; these information specify whether punch P1 and die D1 are mounted with the font-side facing forward or the reverse side facing forward. Likewise, symbols and/or figures showing punch P2 and die D2 are entered in such a manner, for example, that the central position of each figure is positioned away from the press central position  0  by a distance of +500 mm. The information, “front-side mounting” or “reverse-side mounting” that indicates whether punch P2 and die D2 are mounted with the font-side facing forward or the reverse side facing forward may also be entered.  
         [0097]    In step S 26 , after the data for the arrangement of the tools are entered, the guide program generates a question whether there are additional hints that are useful for performing the tool set-up operation and that are worthwhile to be recorded. If the operator thinks of such hints, he enters the same into the terminal  25  as an operation support information. For example, when the punch and the die are to be mounted on the bending press, it is preferable to attach a tape to the shoulder portion of the die D1, D2 so that the dies D1, D2 are not flawed when attached on the ram  43 . Thus, a message  1 , “Attach a protection tape to the shoulder portion of the die” may be entered as a hint, as shown in FIG. 7A. Further, if the punch P1 and the die D1, for example, respectively are composed of small punches P 5 ′, P 6 ′ and dies D 5 ′, D 6 ′, it is preferable to preliminary secure the small dies D 5 ′, D 6 ′ to a rail (not shown) of the ram  43  with an adhesive tape; further it is preferable that the small punches P 5 ′, P 6 ′ and dies D 5 ′, D 6 ′ are arranged on the rail of the ram so as to be laterally shifted from each other, as shown in FIG. 7B. Thus, additional hints, such as message  2 , “Secure the small dies to the rail of the ram with an adhesive tape” and message  3 , “Arrange the small punches and dies so as to be shifted from each other” are entered into the terminal, as shown in FIG. 7B.  
         [0098]    In step S 27 , an alignment of the punch and the die in the longitudinal direction is performed. This operation is as follows. As shown in FIG. 8, the die  45  of the first bending press  21 , for example, is generally mounted on the ram (or the rail of the ram)  43  so as to be movable in the longitudinal direction (i.e. in the lateral direction in FIG. 8). Therefore, when the die  45  is initially mounted on the ram  43 , the position of a bottom portion  45   a  of a recess of the die  45  is normally displaced in the longitudinal direction from the position of the apex  39   a  of the punch as shown in FIG. 8. As a result, before bending operation, the longitudinal position of the die  45  is adjusted in the longitudinal direction so that the bottom portion  45   a  of the recess coincides with the apex  39   a  of the punch. This operation is called the alignment of the tools in the longitudinal direction. Here, when the lengths of the punch and the die are too short to precisely align the tools, supplemental punch and die with the same shape and longer dimensions are temporarily mounted on the rail of the ram  43 .  
         [0099]    In step S 28 , after the alignment of the tools are performed, the operator enters an instruction on the execution of the alignment of the tool as operation support information. Then, the guide program generates a question whether there is hints that are useful for performing the alignment of the tool. If the operator thinks of such hints, he enters the same into the terminal  25  as additional operation support information. For example, the operator may input a hint that “When short punch and die are to be aligned, supplemental long punch and die with the same shape should be used with the short ones” is entered as a message  4 , as shown in FIG. 8. The guide program may generate similar questions in the following steps whenever useful hints relating to those steps are to be entered although it may not be explicitly mentioned hereinafter.  
         [0100]    In step S 29 , an original-point determination operation (or an original-point adjustment operation) is performed. The original-point (or a reference point) is a position of the die  45  relative to the punch  39  in which position the die  45  is directly engaged to the punch  39  with a predetermined engaging force without workpiece being held between the punch  39  and the die  45 . The original-point determination operation is necessary for the reason as follows. That is, the bending angle of a workpiece bent by the punch and the die is generally determined by the distance moved by the die  45  relative to the punch  39  during bending operation. However, during the bending operation, the side frame  35  or the like of the bending press is deformed. Thus, the distance moved by the die  45  from a reference point determined with no engaging force between the punch and die does not corresponds to the bending angle of the workpiece to be bent by the punch and the die. Therefore the position of the die  45  in the above-mentioned condition where a predetermined force acts between the punch and the die is determined as a correct original position (or a reference position) of the die  45 . It should be noted here that the load, which is applied between the punch and the die, is selected in accordance with the length of the mounted die. That is, if a die having a length longer than a predetermined length is mounted, a load of 7 tons is applied between the punch and the die to determine the original point of the die. On the other hand, if a die shorter than a predetermined length is mounted, the load of 7 tons may break the punch and the die. Therefore, a 3 tons, for example, which is smaller than the durable pressure for the punch and the die is applied between the punch and the die to determine the original point of the die. In the present embodiment, it is supposed that the mounted die is longer than the predetermined length, and the load of 7 tons is applied between the punch and the die.  
         [0101]    In step S 30 , an instruction for performing the original-point determination operation (or the original-point adjustment operation) and a hint relating to the original-point determination operation are entered and stored in the memory of the terminal  25  as operation support information. For example, a message  5 , “When a die having a length shorter than x mm is mounted, set the original-point determination operation load to be 3 tons ” is entered as shown in FIG. 8. In place of entering the message  5 , a program for performing following steps may be provided in the terminal: First, it retrieve the tool number and the length of the tool entered in step S 23 . When the tool is longer than a predetermined length, it generates a first message “Perform the original-point determination with 7 tons” is generated. On the other hand, when the die is shorter than the predetermined length, it generates the second message “Perform the original-point determination with 3 tons”.  
         [0102]    In steps S 31 , S 32 , S 33  and S 34 , trial bending of a workpiece for manufacturing the part (or the product) as shown in FIG. 5 is performed.  
         [0103]    For this, in step S 31 , a trial bending operation number i for specifying each of bending operations is set as 1.  
         [0104]    In step S 32 , the i-th trial bending operation is performed while operation support information relating to the i-th bending are entered, as described in detail below.  
         [0105]    In step S 33 , it is determined whether all of the trial bending operations have been completed. If they have not been completed, the step number i is increased by one in step S 34 , and then the operation returns to step S 32 . If all of the trial bending operations have been completed in step S 33 , the operation proceeds to step S 35 , where a plurality of workpieces are successively bent in the manner determined by the trial bending operations in step S 32 . During this successive bending operations, the bending accuracy is inspected each time a predetermined number of workpieces are processed. If the operation accuracy does not satisfy a predetermined requirement, values D and L, which is described later, are modified.  
         [0106]    After the successive bending operation has been completed, in step S 36 , the operator enters an operation support information on the frequency of checking of the bending accuracy, which is performed in other bending operation, such as in the operations in steps in FIGS. 11. For example, an operation support information to inspect the accuracy for every ten workpieces is entered.  
         [0107]    In step S 37 , a variety of information and data including the operation support information relating to the bending operation entered in steps S 23 , S 24 , S 26 , S 28 , S 30 , S 32 , S 35  and S 36  are transmitted from the terminal  25  to the server  31  together with the part number and the shape of the part, and they are all stored in the data base  33  of the server  31 . In step S 38 , the bending operation for the new part is completed.  
         [0108]    [0108]FIG. 4 is a flow chart for showing in detail the i-th trial bending operation and operation of entering support information relating to the same, which are performed in step S 32  in FIG. 3.  
         [0109]    In step S 41 , a memory area is reserved under a number i in a memory of the terminal  25 . When the program of FIG. 4 is first called upon, the number i is set to be 1 since the i has been set to be 1 in step S 31 .  
         [0110]    In step S 42 , in order to bend a workpiece along bending line B 3  (FIG. 6A) through an angle of 90°, numerical control data D, L and Yz for the bending press  21  are entered into the terminal  25 . As shown in FIG. 14, the data D specifies the vertical position of the die  45  relative to the original position (or the reference position) H 0  determined in step S 29 . The data L specifies the position of a back gauge device  55  in the longitudinal direction (i.e. in the lateral direction in FIG. 14) relative to a reference position which is, for example, the central position Y 0  of the die  45 . The data Yz specifies the vertical position of the back gauge device  55  relative to a reference position, which is, for example, the top end of the die  45 . As described above, the data D determines the bending angle of the workpiece W to be bent by the bending press  21 , while the data L determines the width of the workpiece W between an edge E 1  (see FIG. 9A) and the bending B 3 . The value Yz is used to adjust the vertical position of the back gauge device  55  during bending operation. Specifically, the height of the back gauge device is adjusted to correspond to the height of a flange formed at the rear end of the workpiece (for example, flange W 2  shown in FIG. 9B). For example, in FIG. 10A, the workpiece is inserted between the punch and die in an attitude or position that the flange W 2  projects downward relative to a major portion of the workpiece. Thus, the back gauge device  55  is located in a vertical position lower than that as shown in FIG. 9A so as that the flange W 2  is properly brought into contact with the back gauge device  55 .  
         [0111]    When the data L and Yz are entered, the back gauge device  55  is moved by the control of the terminal  25  in the vertical and longitudinal directions to a position determined by the data.  
         [0112]    In step S 43 , the workpiece W is inserted between the punch  39  and the die  45 , and the rear end thereof is brought into contact with the back gauge device  55  to position the same with respect to the punch and die. Thereafter, the first trial bending is performed on the workpiece W along the bending line B 3 .  
         [0113]    In step S 44 , on the basis of the trial bending operation performed in step S 43 , operator enters operation support information in relation to the positioning of the workpiece W relative to the punch and die. These operation support information includes hints relating to the positioning of the workpiece. Specifically, as shown in FIG. 9A, when the first trial bending operation is completed, a figure showing the tools P1, D1 on bending press  21  and the workpiece W appears on the screen of the CRT  25   b  in response to a completion signal from the bending press  21 . In order to inform the operator the appearance of the figure, a sound buzzer and the like may be provided. Thus, for example, when the sound buzzer is activated, the operator moves to a position in front of the terminal  25 . In the first bending operation, the punch P1 and the die D1 on the bending press  21  are used to perform the bending operation (see FIG. 6B). In order to save this information, the color of the figures of the punch P1 and D1 is changed into gray as shown in FIG. 9A,. Then, information concerning positioning of the workpiece W with respect to the punch and die is saved. For this, the figure of the workpiece W on the CRT screen is moved translationally and rotationally to a position in front of the punch P1 and the die D1, as shown in FIG. 9A. This movement of the figure of the workpiece can be carried out by using a mouse (not shown) or a joystick (not shown) connected to the terminal  25 . As described before, in the first bending operation, the edge E 1  of the workpiece W is brought into contact with the back gauge device  55 , and the bending operation is performed along the bending line B3. Therefore, the figure of the workpiece W is located in a attitude as shown in FIG. 9A with respect to the figure of the punch P1 and die D1.  
         [0114]    Then, as shown in FIG. 9A, the operator enters the messages  6  and  7  relating to the positioning of the workpiece W as hints. Specifically, the message  6 , “Insert the workpiece between the punch and die in a manner that its sheet surface faces upwards” is a hint for specifying the side of the workpiece W to be inserted between the tool. The “sheet surface” means a surface of the workpiece on which a vinyl sheet is attached; the vinyl sheet is attached on that surface to protect that surface from being scratched during transportation. The side of the workpiece can also be designated by specifying the directions of burrs formed on the workpiece. In this case, a message, for example, “Locate the workpiece in such a manner that the direction of burrs face downward” is entered. The message  7 , “Securely bring the workpiece into contact with right and left back gauge devices” is a hint for reminding the operator to securely engaging the rear end of the workpiece with the right and left back gauge devices  55  when the workpiece W is inserted between the punch and die. This message  7  is entered because a precise bending cannot be achieved if either one of the back gauge devices fails to contact the rear end of the workpiece. After these information are displayed on the CRT  25   b , all data are stored in a memory of the terminal  25 .  
         [0115]    In step S 45 , the operator determines in accordance with the result of the trial bending operation whether buckling of the workpiece has occurred during first trial bending operation or whether the buckling of the workpiece could occur during the first bending operation during the successive bending operation in step S 35 . If an affirmative determination is made, the operation proceeds to step S 46 .  
         [0116]    In step S 46 , the operator enters an instruction to support the end of the workpiece W from a lower position during the bending operation as a operation support information (see message  6   a  shown in FIG. 9A).  
         [0117]    In step S 47 , the part manufactured by the trial bending operation is inspected. Specifically, the operator measures the length and angle of a flange W 2  formed by the first bending operation.  
         [0118]    After the measurement has been carried out, in step S 48 , the operator enters into the terminal an instruction or a hint for specifying dimensions and angles to be measured and together with their tolerances, as operation support information. Specifically, as shown in FIG. 9B, when the shape of the workpiece W including the flange W 2  formed by the trial bending operation is displayed on the screen of the CRT  25   c , the operator enters symbols relating the length “L1” of the flange W 2  and symbols relating the angle “θ1” of the same as an operation support information. Moreover, a message  8  “Check that height L1 is 15 mm (+0.1 mm)” and a message  9  “Check that angle θ1 is 90°” are entered. The shape of the flange W 2  may be displayed in the form of a cross sectional view, as shown in FIG. 9C. By displaying the shape of the flange with the cross sectional view, the height L 1  of the flange being a dimension including the thickness of bottom surface portion W 1  of the workpiece W can be more easily understood. In order to emphasize that the dimension L1 includes the thickness of the bottom surface portion W 1 , a message “Note that the dimension L1 includes the thickness of the bottom surface portion W 1 ” may be added to the display in FIG. 9B or  9 C.  
         [0119]    After entering the instruction or hint for measuring the height L 1  and the angle θ1 of the flange, in step S 49 , the operator determines whether the dimension L 1  and the angle θ1 are within a required tolerance. For example, it is determined whether the dimension L1 is within a range of 15 mm±0.1 mm. If it is determined in step S 49  that the dimension L1 is not within the range, either or both of the values D and L are modified in step S 50 . Then, the operation returns to step S 43  so that the trial bending operation is again performed.  
         [0120]    If the dimension L1 and the angle θ1 are within the required range in step S 49 , the foregoing data D, L and Yz are stored in step S 51  in the memory area under the number i.  
         [0121]    Trial bending operations for the process number i=2 and for the process number i=3 are performed in a manner similar to the trial operation for the process number i=1.  
         [0122]    Specifically, when the process number i=2, in step S 44 , the figure of the workpiece W that has been bent along the bending line B 3  is displayed on the screen of the CRT  25   c  together with the bending press  21 , as shown in FIG. 10A. In the second trial bending operation, the punch P1 and the die D1 are again used to perform the bending operation along the bending line B2. Therefore, the figures of the punch P1 and the die D1 are displayed in gray, as shown in FIG. 10A. The back gauge device  55  is brought into contact with the flange W 2  formed in the first bending operation. Therefore, as shown in FIG. 10A, the figure of the back gauge device  55  is moved to a position lower than that of the back gauge device  55  in FIG. 9A. Then, the figure of the workpiece W is suitably moved until it has an attitude (or an orientation) that the edge E 2  faces toward the punch P1 and the die D1, as shown in FIG. 10A. In the second trial bending operation, the workpiece W is bent along the bending line B 2  in a direction opposite to that in the first bending operation. Therefore, a message  10 , “Insert the workpiece W in such a manner that the sheet surface faces downwards” is entered.  
         [0123]    In step S 48  in the second trial bending operation, the shape of the workpiece including the flange W 2  formed in the first trial bending operation and the flange W 3  formed in the second trial bending operation is displayed, as shown in FIG. 10B. Therefore, the operator inputs figures or symbols relating the dimension L2 and the angle θ2, which must be measured in relation to the flange W 3 , as shown in FIG. 10B. Moreover, messages  11  and  12  to measure the dimension L2 and the angle θ2 are entered. The shape of the workpiece including the figures or symbols relating the dimension L2 and the angle θ2 may be displayed in the form of a cross sectional view, as shown in FIG. 10C. This view clearly shows that the dimension L2 includes the thickness of the flange W 2  and the base portion W 1 .  
         [0124]    In case of the process number i=3, in step S 44 , the shape of the workpiece W that has been subjected to the first and second bending operations is displayed together with the punches and dies of the press  21  on the screen of the CRT  25   c , as shown in FIG. 11A. In the third trial bending operation, the punch P2 and the die D2 are used for the bending operation. Therefore, the punch P2 and the die D2 are displayed in gray. Moreover, the figure showing the back gauge device  55  is moved to positions around the punch P2 and the die D2. Then, the operator moves the figure showing the workpiece W until the end E 3  faces the punch P2 and the die D2, as shown in FIG. 11A. In the third bending operation, the workpiece W is bent along the bending line B1 in the same direction as that in the first bending operation. Therefore, a message  13  instructing this, that is, “Insert the workpiece W in such a manner that the sheet surface faces upwards” is entered.  
         [0125]    In step S 48  in the third trial bending operation, the shape of the workpiece W that has the flange W 2  formed in the first bending operation, the flange W 3  formed in the second bending operation and the flange W 4  formed in the third bending operation is displayed, as shown in FIG. 11B or FIG. 11C. Then, the operator inputs symbols relating to width L3 and angle θ3 relating to the flange W 4  formed in the third trial bending operation and messages  14  and  15  to measure these dimensions.  
         [0126]    As described above, in the new bending method according to this embodiment, a skilled operator stores into the terminal computer  25  the operation information for efficiently performing a trial bending operation in the part, as operation support information or guide information or hints, while performing the trial bending operations. Moreover, the operation information is transmitted to and stored in the data base  33  of the server  31 . Therefore, if the same or similar part is ordered later, the operation information stored for each part is retrieved from the data base  33  so that an optimum operation for manufacturing the ordered part is performed easily and quickly. In particular, even an operator without skill can perform a necessary bending operation easily and quickly by referring to the operation information above.  
         [0127]    Further, in the foregoing method, a guide program for guiding a new bending operation is activated (see step S 21 ) when an operator enter into the terminal  25  an instruction for the novel bending operation. According to the guide program for a novel bending, operation, the terminal  25  urges the operator to enter suitable information including operation support information relating to set-up operation (preparation operation) and the bending operation after the operator has completed actual set-up operation and bending operation. Therefore, the operator can securely enter suitable information including the operation support information.  
         [0128]    As described above, in step S 37 , the variety of the information that relates to the bending operation for the new part and are entered in steps S 23 , S 25 , S 26 , S 28 , S 30 , S 32  (including steps S 42 , S 44 , S 46 , S 48 , S 50  and S 51 ) and step S 36  are stored in the data base  33  of the server  31  together with the part number and the shape of the part. The following Tables 1 to 5 show a manner in which the foregoing various information including the operation support information are stored in the data base  33 .  
         [0129]    First, a part file specified by a part identifying data (refereed to hereinafter as “part ID”) such as the part number for specifying a part is provided. As shown in Table 1, the part file has a file for shape, a file for set-up operation and a file for bending operation. The file for the shape stores data for the shape as shown in FIGS. 5 and 6A.  
                             TABLE 1                       Part ID       Part File                                    File for Shape   FIGS. 5 and 6A           File for Set-up Operation   Table 2           File for Bending Operation   Table 5                      
 
         [0130]    The file for the set-up operation has a file for the bending order, a file for the tools, a file for the tool layout, a file for the alignment of the tools and a file for the original-point determination operation, as shown in Table 2. Here, the file for the bending order stores bending order data shown in FIG. 6B or Table 3, the file for the die stores data of the dies shown in FIG. 6B or Table 4, the file for the die layout stores data for the layout of the die shown in FIG. 7A and FIG. 7B, the file for the alignment of tools stores data for the FIG. 8 and the message  4  therein, and the file for the original-point determination operation stores data for FIG. 8 and the message  5  therein.  
                         TABLE 2                       File for Set-up Operation                                File for Bending Order   FIG. 6B, Table 3       File for Tools   Table 4       File for Tool Layout   FIG. 7A, FIG. 7B       File for Tool Alignment   FIG. 8 and Message 4       File for Original-Point Determination Operation   FIG. 8 and Message 5                  
 
         [0131]    [0131]                             TABLE 3                           A Portion of File for Bending Order                Bending Line   Bending Order                       B1   3           B2   2           B3   1                        
         [0132]    [0132]                             TABLE 4                           File for Tools                Punch Number   Punch Length       Bending Line Number   Die Number   Die Length               B1   P2 = 14702    50           D2 = 30286(10)    50       B2   P1 = 402   835           D1 = 30286(11)   835       B3   P1 = 402   835           D1 = 30286(11)   835                    
         [0133]    The file for the bending operation stores bending operation data as shown in Table 5. That is, data for symbols and figures as shown in FIG. 9A and FIG. 9B (or FIG. 9C) and data of D 1 , L 1  and Yz 1  for the D, L and Yz as shown in FIG. 14 are stored in relation to the bending line number B 1 . In relation to the bending line number B 2 , data for symbols and figures as shown in FIG. 10A and FIG. 10B (or FIG. 10C) and data of D 2 , L 2  and Yz 2  for the D, L and Yz are stored. In relation to the bending line number B 3 , data for the symbols and figures as shown in FIG. 11A and FIG. 11B (or FIG. 11C) and data of D 3 , L 3  and Yz 3  for the D, L and Yz are stored.  
                             TABLE 5                           File for Bending Operation            Bending Line   Bending Operation Support           Number   Information   Data for D, L, Yz               B1   FIGS. 9A and 9B (or FIG. 9C)   D = D1               L = L1               Yz = Yz1       B2   FIGS. 10A and 10B (or FIG.10C)   D = D2               L = L2               Yz = Yz2       B3   FIGS. 11A and 11B (or FIG.11C)   D = D3               L = L3               Yz = Yz3                  
 
         [0134]    A method of manufacturing parts by using data for bending operation stored in the data base  33  will now be described with reference to FIG. 2 and FIGS. 12A and 12B. Hereinafter this operation is called a repeat/similar bending operation or a same part/similar part bending operation. Note that FIG. 12A is a detailed flow chart of step S 13  shown in FIG. 2, and FIG. 12B is a detailed flow chart of step S 72  shown in FIG. 12A. The repeat/similar bending operation is supposed to be performed at the second bending station  22  in FIG. 1.  
         [0135]    Referring again to FIG. 2, in step S 10 , an operator at the second bending station  22  reads the bar code attached to an operation instruction sheet by using the bar code scanner  27   a . Then, bending operation data for manufacturing a ordered part, which is the same as or similar to the part stored in the data base  33  of the server  31 , is retrieved to the terminal  27 .  
         [0136]    In step S 11 , if it is determined that the ordered part is not a new part (that is, if the data base  33  includes bending operation data for one or more parts that are the same as or similar to the ordered part), the operation proceeds to step S 61  in FIG. 12A. In step S 61 , a guide program for guiding the operator in performing the repeat/similar bending operation is activated.  
         [0137]    In step S 62 , a perspective view of the ordered part and that of a part that is the same as or similar to the ordered part a retrieved and displayed on the CRT screen  27   b  as shown in FIG. 5; here, a statement that the ordered part is the same as or similar to the part or parts data of which have been stored in the database  33  is simultaneously displayed on the CRT screen  27   b  (not shown). When bending data for a similar part is used to manufacture the ordered part, the shape of the ordered part and the shape of the similar part are also simultaneously displayed on the CRT screen  27   b . Here, in the following, it is supposed that the shapes of the ordered part and of the similar part differs from each other slightly, for example, in width of the flange W 2  as shown in FIG. 5. Then, the operator observes the perspective views of the parts to confirm the shape of the part to manufacture.  
         [0138]    In step S 63 , the operator depresses an suitable key on the keyboard  27   c  so that data for unfolded views of the ordered part (and that of the similar part), data for the bending order for manufacturing the part and data for the tool numbers to be used are retrieved and displayed on the screen, as shown in FIGS. 6A and 6B. Thus, the operator can easily confirm the unfolded views of the parts, the bending order and the die to be used.  
         [0139]    In step S 64 , the operator selects necessary tools (i.e. punches and dies) P1, D1, P2 or D2 from an suitable die magazine by referring to the tools displayed on the screen  27   b.    
         [0140]    In step S 65 , the operator again depresses an suitable key on the keyboard  27   c  so that the layout (arrangement) of the tools on the second bending press  23  and hints for arranging the tools are displayed on the screen as operation support information, as shown in FIG. 7A and FIG. 7B.  
         [0141]    In step S 66 , the operator places or mounts selected tools on the bending press  23  by referring to the tool arrangement displayed on the CRT screen  27   b  in step S 65 .  
         [0142]    In step S 67 , the operator depresses an suitable key on the keyboard so that the cross sectional shape of the tools, the instructions (not shown) for performing the alignment of the tools and the hints or operation support information relating to the alignment of the tools (such as the message  4 ) are displayed on the screen  27   b , as shown in FIG. 8.  
         [0143]    In step S 68 , the operator aligns the tools on the bending press  23  by referring to the figures and statements displayed on the screen  27   b.    
         [0144]    In step S 69 , the operator again depresses an suitable key on the keyboard  25   c  so that the cross sectional view of the tools, the instruction (not shown) for determining the original point of the die and hints for performing original-point determination (such as the message  5 ) are displayed on the screen, as shown in FIG. 8.  
         [0145]    In step S 70 , the operator performs the determination of the original-point of the die in the bending press  23  while referring to information displayed on the screen  27   b  in step S 69 .  
         [0146]    When the original-point determination operation is completed, the process proceeds to step S 71 , where the bending operation number i is set to 1.  
         [0147]    In step S 72 , the operator performs an i-th trial bending operation in a workpiece referring to operation support information for the i-th trial bending operation displayed on the screen of the CRT  27   b.    
         [0148]    In step S 73 , it is determined whether all of the trial bending operations have been completed. If all of the trial bending operations have not been completed, the bending operation number i is increased by one at step S 74 , and the process returns to step S 72 .  
         [0149]    If all of the trial bending operations have been completed in step S 73 , the operation proceeds to step S 75 .  
         [0150]    In step S 75 , the frequency for checking the accuracy of the bending operations carried out during successive bending operation performed in step s 76  is displayed on the screen. For example, an instruction to check the accuracy for every 10 workpieces is displayed on the screen of the CRT  27   b.    
         [0151]    In step S 76 , the operator successively bends a plurality of workpieces in accordance with the trial bending operations performed in step S 72  so as to manufacture the plurality of the ordered parts. During this operation, the operator follows the instructions displayed in step S 75  to check the bending accuracy each time 10 parts are processed. If the processing accuracy does not satisfy a predetermined tolerance, the value L and value D are modified.  
         [0152]    In step S 77 , the value L and the value D modified in step S 76  are stored in the data base  33  through the terminal  27 . In step S 78 , the repeat/similar being process is completed.  
         [0153]    [0153]FIG. 12B is a flow chart showing details of the i-th trial bending operation performed in step S 72  shown in FIG. 12A.  
         [0154]    When the operator sets the bending operation number i to 1 in step S 71 , the process proceeds to step S 80 , where information for positioning the workpiece W relative to the tools P1 and D1 and the hints relating to the operation for locating the workpiece are displayed as operation support information on the screen of the CRT  27   b , as shown in FIG. 9A.  
         [0155]    In step S 81 , the operator locates the workpiece V with respect to the punch P1 and the die D1 by referring to the display on the screen. Moreover, the workpiece W is located so that the bending line B3 of the workpiece W is positioned between the punch P1 and the die D2. Here, the position of the back gauge device  55  is located to a predetermined height in the rear of the punch P1 and the die D1 in accordance with the data of L and Yz retrieved from the database  33 .  
         [0156]    When the ordered part has a shape similar to that of the part retrieved from the database  33 , the position of the back gauge device  55  in the longitudinal direction (that is, the value of L) is somewhat modified in step S 81  in accordance with the actual width of the flange W 2  of the ordered part (as described above, it is supposed here that the length of the flange W 2  of the ordered part is somewhat different from the length of the flange W 2  of the similar part stored in the database  33 ).  
         [0157]    In step S 82 , the operator executes the ith trial bending operation on the workpiece W along the bending line B3.  
         [0158]    After the bending operation has been completed, in step S 83 , the shape of the workpiece formed with the flange W 2  as well as the figures (and instructions) relating to the dimension L1 and angle θ1 to be measured for inspection of the bending accuracy are displayed on the screen of the CRT  27   b , as shown in FIG. 9B or  9 C.  
         [0159]    In step S 84 , the operator inspects or measures the dimension L1 and the angle θ1 of the workpiece by referring to the dimension and the angle displayed on the screen.  
         [0160]    In step S 85 , it is determined whether the dimension L1 and the angle θ1 are within a predetermined tolerance. If the predetermined tolerance is not satisfied, the value D and the value L are modified in step S 86  and in step S 87 , the i-th trial bending operation is completed.  
         [0161]    In the second trial bending operation where i=2, the figures and symbols shown in FIG. 10A are displayed in step S 80 , and in step S 83 , figures and symbols shown in FIG. 10B or FIG. 10C are displayed.  
         [0162]    Likewise, in the third bending operation where i=3, figures and symbols shown in FIG. 11A are displayed in step S 80 , and in step S 83 , figures and symbols shown in FIG. 11B or FIG. 11C are displayed.  
         [0163]    As described above, in the repeat/similar bending operation according to this embodiment, variety of data including operation support information stored for manufacturing one of more parts that are the same as or similar to the ordered part are retrieved from the data base; then the bending operation is performed on the basis of the retrieved data. Therefore, an operator without skill at bending operation can completely use the operation information stored by a skilled operator. As a result, even the non-skilled operator can easily and quickly perform a precise bending operation.