# How flexible parts with a large radius (options)

The invention relates to the field of metal forming, in particular for cold sheet metal stamping. How flexible parts with a large radius can be carried out in a die having a punch and die or plate bending roller machine. The peculiarity is that carried out by the local excesses details at the end of the punch (in the case of stamp) or flexible (in the case of plate bending roll machine). Use the stamp, one of the elements which has a working surface in the form of constructive elements of “the ledge” - “depression”, the step between which is selected depending on the material thickness and radius of bending, or bending roller machine, one of the shafts which has a working surface in the form of constructive elements of “the ledge” - “depression”, the step between them and their number on the shaft selected constructively. Increases accuracy when benching with a large radius in the stamp or plate bending roller machine. 2 ad and 3 C.p. f-crystals, 6 ill.

The invention relates to machine building and instrument engineering, in particular for cold sheet metal stamping, and may be used to obtain details about flexible parts on a large radius (R/S>10) stamp when the punch radius is obviously smaller than the radius of the workpiece after bending (Reference designer stamps: stamping. /Under the General editorship of L. I. Rudman. - M.: mechanical engineering, 1988, pp. 210-211) (prototype). This is because when bending over a large radius in addition to the large angle of springback is the elastic change of the radius of curvature. The radius of the punch are calculated according to the formula, according to which it depends on the material thickness s of the flexible radius r and the K-factorvthat is determined by the mechanical characteristics of the material. It follows from this formula that the stamp prototype impossible flexible with given radius parts of different thickness and with different mechanical characteristics. The calculation formula is only approximate and, as shown, gives satisfactory results.

The disadvantages of this method are:

- low accuracy in bending, related to the fact that the amount of springback depends on many factors, the main of which are the mechanical properties of flexible material, the harder the material, the greater the angle of springback), the radius of bending (the larger the radius, the greater the angle of springback), material thickness (the thinner mater,, p. 75).

- inability to obtain parts with a very large radius (curvature), related to the fact that when the ratio of the radius of the items to the punch radius more than two after removal of the load is complete straightening details;

- inability flexible in one stamp parts of different thicknesses;

- inability flexible in one stamp parts with different mechanical properties;

- inability flexible strip (narrow and long) parts with a very large radius (curvature). A conventional flexible such details cannot be obtained, since the bend with a large radius of deformation of the cross-section will be entirely or substantially elastic, whereupon the workpiece is representivity and straightened. These parts are produced by the method of bending to stretching of the workpiece (Reference cold stamping. B. N. Romanovsky. - L.: “engineering”, 1979, page 69).

The result of the above factors is the need for subsequent finishing of the working parts of the stamp.

The technical task of the invention is to improve the accuracy in the bending of the parts with a large radius in stamps, implementing flexible in one stamp parts of different thickness, the implementation of flexible in one very large radius (curvature).

At the end of the punch due to the presence of one of the elements of the punch (the punch or matrix) of structural elements “the ledge” - “depression” carry out local bending parts in the area which is changing directions of stresses under bending. The area of the curve is the distance between points of inflection. The inflection point is the point on the curve (in this case, the neutral point of the line layer) separates the convex and concave side of the curve. During the main flexible inner layers of metal (from punch) having compressive stress, and the external voltage is stretching. In point of inflection is a change of sign of internal stresses, namely: stretch compressed during the main flexible inner layers of detail and contraction of the stretched during flexible outer layers of detail. At the end of a flexible (at the end of the plug) voltage compression and tension strains on the numerical value become equal. In other words, if the bend in details create voltage numerically equal to the stresses that occur when the primary bending and opposite in sign. There is a redistribution and complete removal of internal stresses. After removal of the external load, provided ravennatis punch. During the execution of the kinks need to create the details of the voltage were firm and did not lead to plastic deformation details on the local area of inflection (the distance between the projections of the punch). This is achieved by proper choice of the step between the tabs and the value of the executed kinks (press settings).

Thus the precision of bending depends only on the value of the completed bending part, which is determined by the accuracy of the settings press equipment. Mechanical properties of flexible material and shape of the parts do not affect the bending process, so lapping stamp in the course of its operation is not required. Instead of projections and depressions allowed to use other structural elements (the number of rollers and so on), allowing at the end of the punch to perform local excesses details.

How flexible parts with a large radius in the stamp includes the implementation of local excesses details at the end of the punch through the use of one of the elements of the stamp, the working surface of which is made in the form of constructive elements of “the ledge” - “depression”, the step between which is selected depending on the material thickness and radius of bending. In special cases managemore invention is to improve precision in the bending of the parts with a large radius in the stamp, which depends only on the accuracy of manufacturing tooling and precision settings press equipment, the implementation of flexible one stamp at a given radius parts of different thickness, the implementation of flexible one stamp parts with different mechanical characteristics, the implementation of flexible stamps strip of details with a very large radius (curvature) which cannot be achieved by conventional flexible and which are produced by the method of bending to stretching of the workpiece.

In Fig.1 shows a diagram of stresses during bending parts with a large radius in the stamp, punch radius which is smaller than the radius of the part (prototype). Internal metal layers (from punch) having compressive stress, and the external voltage is stretching. After removal of the external load angle springback will have a positive value, the radius of the details will have more punch radius.

In Fig.2 shows a diagram of a flexible, using local inflection details at the end of the punch, the radius of which is equal to the radius of the part. During the break there is a redistribution of internal stresses. After removal of the external load angle springback will be equal to zero, the radius of the details will be equal to the radius of the punch.

In Fig.3 and the bending at the specified radius of the details of different thickness.

In Fig.4 depicts a flexible circuit using a stamp with a matrix containing two rows of rollers. The pressure rollers on the item constantly throughout the bend radius.

Of great importance for the implementation of the specified technical result is the step between the projections, which can be in a wide interval of values. The step size is prescribed constructively depending on the thickness and radius of bending. For example, for flexible parts with a thickness of 6 mm radius 120 mm step between the projections on the punch equal to 20.9 mm, which thickness is 3.5 details.

There is a method of bending parts with a large radius for bending rollers (roller machines) (cold forming Technology. M. E. Teeth. - L.: the motor cycle " State scientific and technical publishing house of the engineering literature. Leningrad branch, 1950, page 392) (prototype).

The disadvantages of this method are:

- low accuracy in the bending associated with the above listed factors influencing the bending process;

- inability flexible strip (narrow and long) parts with a very large radius (curvature).

A conventional flexible in bending roller machine such details cannot be obtained, since the bend with a large radius of fact deformation is Asparaginate and straightened. These parts are produced by the method of bending to stretching of the workpiece (Reference cold stamping. B. N. Romanovsky. - L.: “engineering”, 1979, page 69).

The technical task of the invention is to improve the accuracy in the bending of the parts with a large radius on the plate bending roller machine, the implementation of a flexible strip of details with a very large radius (curvature).

In the process of bending due to the presence on one of the shafts bending roller machine structural elements “the ledge” - “depression” carry out local bending parts in the area which is changing directions of stresses under bending. The area of the curve is the distance between points of inflection. The inflection point is the point on the curve (in this case, the neutral point of the line layer) separates the convex and concave side of the curve. During the flexible bending shafts Flex item, with the internal metal layers (from the minimum radius parts) having compressive stress, and the external voltage is stretching. In point of inflection is a change of sign of internal stresses, namely: stretch compressed during the flexible inner layers of detail and compression stretched in time the surrounding when bending details and opposite in sign. There is a redistribution and complete removal of internal stresses. After removal of the external load under the condition of equality of compression stress and tensile stresses elastic springback is missing, the radius of the details after leaving the working area is not changed. During the execution of the kinks need to create the details of the voltage were firm and did not lead to plastic deformation details on the local area of inflection (the distance between the projections of the shaft). This is achieved by proper choice of the step between the tabs and the value of the executed kinks (the setting of the bending equipment).

Thus, the precision of bending depends on the setting accuracy of the bending equipment. Mechanical properties of flexible material and shape of the parts do not affect the bending process.

How flexible parts with large radius for bending rollers includes the implementation of local excesses of items during flexible through the use of one of the shafts, the working surface of which is made in the form of constructive elements of “the ledge” - “depression”, the step between them and their number on the shaft choose constructively. In the particular case can be used per working Poveda increase in accuracy when the bending of the parts with a large radius on the plate bending roller machine, which depends only setting accuracy bending equipment, a flexible plate bending roller machine bandpass parts with a very large radius (curvature) which cannot be achieved by conventional flexible and which are produced by the method of bending to stretching of the workpiece.

In Fig.1 shows a diagram of stresses during bending parts with a large radius on the plate bending roller machine (prototype). Internal metal layers (from the minimum radius parts) having compressive stress, and the external voltage is stretching.

In Fig.2 shows a diagram using local break parts during bending. During the break there is a redistribution of internal stresses. After removal of the external load elastic springback is missing, the radius of the details after leaving the working area is not changed.

In Fig.5 shows a diagram of the bending parts for plate bending roller machine. Design of shafts improves the accuracy flexible.

In Fig.6 shows a diagram of the bending parts for plate bending roller machine. One of the shafts has a working surface of the elastic polymer materials.

Important for the implementation of the specified technical result is the step in between the persons of flexible parts with a large radius in the stamp, contains the punch and die, characterized in that the implement local excesses details at the end of the punch through the use of one of the elements of a stamp having a working surface in the form of constructive elements of the protrusion - depression, the step between which is selected depending on the material thickness and radius of bending.

2. How flexible under item 1, characterized in that use elastic matrix.

3. How flexible under item 1, characterized in that use a matrix containing two rows of rollers.

4. How flexible parts with a large radius on the plate-bending rolls with bending shafts, characterized in that the implement local excesses of items during flexible through the use of one of the shafts having a working surface in the form of constructive elements of the protrusion - depression, the step between them and their number on the shaft selected constructively.

5. How flexible under item 4, characterized in that use shaft with the working surface of the elastic polymer materials.

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SUBSTANCE: method comprises steps of punching central portion of blank for making preliminary opening less than opening of ready part; placing blank between die and punch and drawing it at stretching said opening; selecting size of flat blank according to calculated condition for making two blanks; before drawing forming in flat blank preset shaped profile of parts and performing drawing in the form of U-shaped circular profile; dividing parts by removing excess material.

EFFECT: increased factor of using material, lowered labor consumption, improved accuracy of formed parts.

3 dwg, 1 ex