RU2569864C2 - Sheet bending machine and production of increasing radius of curvature - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: bending is executed at the sheet bending machine. Forming drum is mounted at the bed of said machine. Said drum is composed of shaped cams coupled by two rods. One of the latter makes the shaft resting on two brackets arranged at said bed and revolved by the handle. The sheet blank end is fitted into the forming drum cutout, the drum being turned clockwise by aforesaid handle. Sheet elastoplastic straining starts after the sheet is pressed to the bed and ends at the moment the drum cams rest on the bed. After removal of the torque applied to the handle the sheet blank springs back to preset shape of the part.

EFFECT: higher precision of bending to low curvature radii of resilient steel sheets.

2 cl, 7 dwg

Description

The invention relates to the field of metal forming, in particular to bending sheet metal with increasing radius of curvature, and can be used for the manufacture of sheathing of propeller blades of wind turbines, as well as sheathing of wing socks, horizontal tail and other load-bearing parts of aircraft. The invention can also be used for profile (coordinate) bending of metal plating.

The prior art methods of metal forming for bending sheet metal parts (RF patents for inventions No. 2243843, 2414980, 2272690, 2307719, 2243049), the shaping of which is performed by deformation of the workpieces using deforming elements having a profile surface of a given curvature.

There is a method of bending parts over a large radius in the stamp, in which the radius of the punch is known to be smaller than the radius in the part after bending (Reference stamp designer: Sheet stamping. / Under the general editorship of LI Rudman. - M.: Engineering, 1988 p. 210-211). This is due to the fact that when bending along a large radius, in addition to a large spring angle, an elastic change in the radius of curvature occurs. The radius of curvature of the punch is calculated by the formula according to which it depends on the thickness of the material, the bending radius and the coefficients of the mechanical characteristics of the material. The calculation by the formula is approximate.

The disadvantage of this method is the low accuracy during bending due to changes in the magnitude of the spring.

Rotary table bending machines for bending long products and pipes are widely known. The end of the bent workpiece is fixed on a round table, and its bending is carried out by rotating the table. In this case, the free end of the workpiece is held by a roller. The curvature of the bend is determined by the template in the form of a flat shaped cam mounted on a table. The disadvantage of this machine is that it does not perform the functions of a bending machine.

Rotary bending machines with symmetrical or asymmetric roll arrangement are widely known. The symmetrical arrangement of the rolls allows bending of the workpiece at lower values of force and torque. In this case, both ends of the workpiece remain straight. With an asymmetric arrangement of the rolls, only one of them remains straight.

Despite the widespread use in mechanical engineering of rotary bending machines, they cannot be used to form a profile with a variable radius of curvature at precisely specified profile coordinates.

The prior art bending press for bending sheet metal (options) (patent RU No. 2433008 C1, class B21D 5/01, publ. 10.11.2011), containing the upper and lower tables with a bending tool and slots and adjusting stops. Using this bending press according to one of the options, it is possible to form a predetermined curvature of the sheathing of the blades of the propeller of a wind power plant, wing or tail of an airplane according to the coordinates of the aerodynamic profile.

However, the use of such powerful and expensive press equipment for profile bending of thin sheet metal is impractical for economic reasons.

The technical task of the claimed group of inventions is to increase accuracy when bending sheet metal parts with an increasing radius of curvature in the manufacture of skins for aerodynamic profiles, for example, propeller blades of wind turbines, wing and empennage of light aircraft and unmanned aerial vehicles, especially in small-scale production.

To solve the technical problem and implement the proposed method, a bending machine was developed to produce parts with an increasing radius of curvature from a sufficiently elastic sheet metal, for example, aluminum alloy D16AT, with the corresponding given coordinates of the aerodynamic profile.

The inventive method for producing parts with increasing radius of curvature from thin elastic metal billets of a given thickness using a bending machine provides a technical result - improving the bending accuracy when obtaining small radii of curvature of thin elastic metal sheets, reducing the complexity and energy consumption of the forming process.

A bending machine for producing parts with an increasing radius of curvature from thin elastic metal sheet blanks of a given thickness is made in the form of flat profiled cams fixedly mounted on two rods, one of which is a shaft supported on the bushings of two brackets fixed on the frame with the possibility of rotation from the handle, while the profiled cams are made with a slot for setting the end of the sheet stock and a contour defined taking into account the selected thickness of the sheet blank and Ivanov workpiece material used.

The solution of the technical problem of the invention according to the method lies in the fact that in the method for producing parts with increasing radius of curvature from thin elastic metal blanks of a given thickness using a bending machine, including setting the end of the sheet blank in the slots of the profiled cams of the forming drum, its pressing against the base, according to the invention wrap the sheet blank on the forming drum when it is rotated using the handle until the profiled cams rest on the bed, removed from the handle torque and raspruzhinivayut sheet blank, prior to taking a predetermined shape of the part.

The essence of the invention is illustrated by the following drawings and graph.

FIG. 1 - General view of the bending machine;

FIG. 2 - the same, the beginning of work, in the slot of the cams inserted the end of the sheet blank;

FIG. 3 - the same, the beginning of the elastoplastic deformation of the sheet stock;

FIG. 4 - the same, the end of the working cycle, the moment of support of the cams of the profiling drum on the base;

FIG. 5 is a graph of the radii of a bent sheet of a workpiece (after its release) and a cylindrical surface;

FIG. 6 is a graphical depiction of a given shape of the blank profile;

FIG. 7 is a graphical representation of a cam profile contour.

The main part of the machine (Fig. 1) is a forming drum 2 mounted on the frame 1, assembled from profiled cams 3, interconnected by two rods, one of which is a shaft 4, supported by two brackets 5 on the frame 1 and driven by a handle 6.

The end of the sheet blank is inserted into the slot 7 of the cams of the forming drum 2 (Fig. 1), after which it is rotated using the handle 6 clockwise. The elastic-plastic deformation of the sheet begins from the moment it is pressed against the frame 1 and ends when the cams 3 of the profiling drum 2 rest on the frame. The full duty cycle of elastoplastic deformation is shown in FIG. 2-4. After removing the torque applied to the handle 6, the workpiece, springing, acquires the specified shape of the part.

In this case, the specified profile shape will be accurately provided only for a pre-selected thickness of the material used, under which the forming drum 2 is developed.

Like a punch (see. Stamp Designer Handbook: Sheet Metal Stamping. / Under the General Editorship of LI Rudman. - M.: Mashinostroenie, 1988, p. 210-211) the current radius of the forming drum is obviously smaller than the radius of the part after bending . This is because when bending along a large radius, in addition to a large spring angle, there is an elastic change in the radius of curvature. The radius of curvature of the punch is calculated by the formula according to which it depends on the thickness of the material, the bending radius and a certain coefficient determined by the mechanical characteristics of the material. The calculation, according to the authors of the above source, is approximate and, as practice has shown, gives only approximate results.

Based on this, the claimed new method of bending is based on experimental data when working with sheet material:

- cut a number of narrow sheet blanks-plates (in the amount of 5 ... 10 pcs.) from the material of the workpiece;

- choose cylindrical surfaces of different diameters, to which these plates are pressed around the circumference; measure the diameters of the used cylindrical surfaces and the diameters of the corresponding curved plates and plot (Fig. 5) the dependence of the radius of the curved plate (after its release) on the radius of the cylindrical surface to which it was pressed during the experiment.

According to this graph (Fig. 5), for the selected material and its thickness, cam profiles 3 are constructed for any profile, including aerodynamic. To do this, it is necessary: to build a profile contour (Fig. 6) and divide it into separate sections, placing the perpendiculars to the tangents at the beginning and end of each section, determine the current radii of curvature using the previously constructed graph (Fig. 5), determine the current radii of curvature for each of the sections of the forming drum 2;

- draw an arc with the smallest radius of the drum 2 and set aside the length of the arc measured on the outline profile of the part (Fig. 6);

- the operation is repeated for each subsequent section, while the arc is laid so that the combined curves form a curve, then the profiled cams 3 of the forming drum 2 are made according to the obtained contour of the curve.

One of the profiled cams 3 is cut out according to the obtained contour. A plate is cut from the workpiece material. Wrap along the contour of the sheet blank plate on the cam 3, and then release. After partial straightening, the plate should correspond to the contour of the manufactured profile.

Claims (2)

1. A bending machine for producing parts with increasing radius of curvature from thin elastic metal sheet blanks of a given thickness, comprising a forming drum mounted on a bed, made in the form of flat profiled cams fixedly mounted on two rods, one of which is a shaft supported on two bushings brackets mounted on the bed with the possibility of rotation from the handle, while the profiled cams are made with a slot for installing the end of the sheet blank and the contour defined taking into account the selected thickness of the sheet stock and springing of the used material of the workpiece. 2. A method of producing parts with increasing radius of curvature from thin elastic metal sheet blanks of a given thickness using a bending machine according to claim 1, comprising setting the end of the sheet blank in the slotted profiled cams of the forming drum, pressing it to the base and winding the sheet blank onto the forming drum when turning it with the handle until the profiled cams rest on the bed, removing the torque from the handle and springing the sheet blank before accepting This form details.

Images