DE2825988C2 - Process and cold forming press for cold forming cylindrical wire sections into spherical, cylindrical or similar workpieces - Google Patents

Description

The invention relates to a method for cold forming cylindrical wire sections into spherical, cylindrical ones or similar workpieces, with the wire section having shear edges between a pair of dies is formed into a workpiece of uniform shape. Also concerns the invention a cold forming press for performing this method, the two relatively movable Has dies and a die drive.

In known cold forming presses for cold forming cylindrical wire sections into spherical, cylindrical ones or similar workpieces (DE-OS 27 28 647, DE-OS 19 07 787 and US-PS 39 19 874) the two dies are driven by the die drive at a relatively high initial speed driven against each other, so that at the beginning of the deformation process with a relatively large Deformation force act on the wire section having sharp shear edges. This results at the beginning, when the shear edges of the wire section with the working surfaces of the dies in Contact, high local area loads on the matrices, which lead to a relatively rapid Wear and tear on the dies. In order to keep wear and tear within limits, you have the speed with which the dies are brought together, limited to about 600 work cycles per minute. That was when using hard metal dies you are able to work around five hundred thousand with one die pair Manufacture balls from cylindrical wire sections by cold forming before the wear and tear of the Matrix reached a level that made it necessary to replace or rework the matrices.

In multi-stage presses for producing screw bolts, it is known that the operating speed to control the relatively movable parts of the press in such a way that this speed is reduced is when a critical tool, namely the trimming tool, comes into engagement to one

ίο to prevent rapid wear of the same (DE-AS 21 09 210 and DE-AS 12 25 4/0). However, no measures are provided to prevent wear and tear on the die due to excessively high localized surface loads at the beginning of the deformation process avoid. Rather, the deformation process begins at a relatively high relative speed of the Die parts and is then continued and ended at a reduced speed.

The invention is based on the object of reducing the wear of the dies when cold forming cylindrical wire sections with shear edges into spherical, cylindrical or similar workpieces and thereby increasing their service life.

In a method of the type mentioned at the outset, this task is carried out with the features of characterizing part of claim 1 solved. Also, this task is done with a cold forming press of the type mentioned above, which has the features of the characterizing part of the claim 2 has.

Advantageous configurations of the cold forming press according to the invention are the subject matter of claims 3 and 4.

According to the invention, the cylindrical wire sections having shear edges are arranged in two on top of one another deformed following stages, namely initially with a relatively low deformation force until the Shear edges of the cylindrical wire sections are sufficiently flattened that relatively large There are contact surfaces between the pre-deformed wire section and the matrices. Then the Deformation force increased and the initially pre-deformed wire section in the same operation brought final shape. Because of the increased contact area between the Wire section and the dies occurs in spite of the second work phase in the final cold forming process not excessively high due to the increased deformation force

so surface loading between wire section and dies, so that the wear on the dies can be significantly reduced compared to known cold forming presses, even if the operating speed overall is increased. In practice it has been found that when applying the present invention, the The service life of the dies is two to three times that of the previously known cold forming presses, namely even when the cold forming press works at a higher operating speed than before. So were

so on a cold forming press with hard metal dies a working speed of 720 working cycles per minute about 1.25 million balls by cold forming made of cylindrical wire sections without excessive wear on the Matrices showed. Rather, the matrices were still dimensionally accurate enough to allow them to be used again to be able to produce a larger number of other flawless balls. This is due to the fact that despite

increased working speed of the cold forming press the speed with which the dies are approaching impinging deforming wire sections, is much less than in the known cold forming presses.

According to the invention, the cylindrical wire sections to be cold-deformed are initially relatively low deformation force and with a relatively low relative speed of the dies detected and pre-deformed to first of all the contact surface between the wire section and the dies to increase. If this contact area is sufficiently large, the Deformation force and also the initial relative speed between the dies is considerable increased to deform the wire section into the final shape. According to the progression of the Deformation process decreases the relative speed between the dies, but remains the deformation force at the increased level, so that with reduced wear of the dies, the output the cold forming press, d. H. their working speed can be increased.

To further explain the invention, the drawing shows an exemplary embodiment of one according to the invention working and trained cold forming press shown, namely shows

F i g. 1 is a perspective view of the cold forming press;

Fig. La is a schematic view of the drive system this cold forming press,

F i g. 2 is a partially sectioned plan view of the cold forming press;

F i g. 3 shows a longitudinal section of the cold forming press along line 3-3 in FIG. 2,

4 shows a partial section of the cam drive for the adjustable stop and

F i g. Fig. 5 is a graph for explaining the work cycle of the cold forming press.

The cold forming press shown in the drawing has a frame 10 with an exchangeable anvil 11 and a stationary die 12. A crankshaft 13 driven by a motor 14 is mounted in the frame 10. A press slide 16 is arranged in the frame 10 relative to the anvil 11 and is of a connecting rod 17 and the crankshaft 13 are driven so that when the crankshaft rotates through 360 ° it has a carries out a full duty cycle.

A die holder 21 can be moved in the frame 10 in the same direction as the press carriage 16 stored, namely in a replaceable stationary die carrier 19 provided on the frame 10 in a cylindrical bearing 22 is slidably supported for limited movement with respect to the anvil 11 enable. A movable die 23 is in the die holder 21 in front of two spacer blocks 24 and 26 arranged. A locking screw 27 is used to lock the movable die 23 in the movable Die holder 21.

The die holder 21 can be from the position shown in FIGS. 2 and 3, in which a to be deformed cylindrical workpiece 28 is gripped by the dies 12 and 23, is advanced against the stationary die 12 will be to deform the workpiece, and be pushed back from this position to the two Matrices 12 and 23 for ejecting a workpiece and for inserting a following workpiece far enough apart.

In a bearing bush 227 is behind the die holder 21 a sliding body 29 is arranged, which delimits a chamber 31 with the die holder, into which through compressed air can be introduced into an inlet (not shown). The compressed air is used for the elastic The die holder 21 is pretensioned in the direction of the stationary die 12 and presses the sliding body 29 towards the rear against a drive element 32 which is arranged on the press carriage 16.

Therefore, the die holder 21 is always adjustable in the direction of the stationary die 12 and against one Pressed stop 33, which is explained in more detail below. A wedge 34 is used to adjust the drive element 32 in the press slide 16. A screw 37 is used to fix the drive element 32 against the wedge 34.

Since the sliding body 29 from the prevailing pressure in the chamber 31 against the front end of the Drive element 32 is pressed, it moves together with the press carriage 16. The press carriage 16 and the sliding body 29 are shown in FIG. 2 and 3 shown in the rear dead center, the sliding body 29 is a considerable distance from the rear face of the spacer block 26. When the press slide 16 is advanced to the front dead center, the slide body 29 comes in Contact with the spacer block 26 and now pushes the movable die 23 against the stationary die 12 in order to deform a workpiece 28 located between the dies. If then the press carriage 16 begins its return movement to the rear dead center, the sliding body moves away 29 from the spacer block 26 so that the movable die 23 does not come from the press carriage 16 from the stationary die 12 is withdrawn. Rather, the stop 33 ensures that the two dies to separate from each other.

The movable die 23 is moved largely independently of the press carriage 16, except during the actual working part of each stroke when the movable die 23 passes through the press slide 16 is advanced to deform the workpiece 28. The movements of the die 23 are controlled so that one can increase the operating speed of the cold forming press.

Wire 41 is fed to the cold forming press, from which a shearing device 66 removes the workpieces 28 shears off. These workpieces are brought to a transport station, in which a transport pin 44 they out of the The shearing device 66 between the gripper 46 pushes the individual workpieces 28 into the processing position transport between the dies 12 and 23, while the dies from the stop 33 from each other are separated. Then the stop 33 is withdrawn so that the die holder 21 is in the in F i g. 2 and 3 position shown can be advanced, in which the ends of the workpiece of the two Matrices are seized. The grippers 46 are now moved out between the dies, whereupon the movable die 23 taken along by the press carriage 16 when it moves into the front dead center is used to deform the cylindrical workpiece into a ball.

F i g. la shows a number of cams for actuating various mechanisms of the cold forming press. At one end of the crankshaft 13 is a gear 47 is provided with a drive gear 48 with a gear ratio of 1: 1. The gear 48 is arranged on a transverse shaft 49 which

drives a shaft 51 extending in the longitudinal direction of the frame 10 via bevel gears 52. Two cams 53, 54 are arranged on the shaft 51. The first cam 53 is used to actuate the transport device and the second cam 54 is used to actuate an arm 62 (FIG 61 provided. The cam 58 confirms the transport pin 44. The cam 59 actuates an ejector 45 and the cam 61 actuates the adjustable stop 33, which is a pin displaceable in its longitudinal direction. Since all cams are driven at the same speed as the crankshaft, each cam rotates 360 ° during each work cycle of the cold forming press, so that the mechanisms operated by these cams are automatically controlled in the work cycle of the press slide 16 together with the other mechanisms.

As in Fig. 4, the stop 33, designed as a pin, is provided with a connecting piece 121 which connects it to the upper end of a pivot lever 122 which is pivotably arranged on an axis 112 . A follower roller 123 is arranged on the lever 122 , which rests on the cam 61. A spring arrangement 124 biases the pivot lever 122 in a clockwise direction (as seen in FIG. 4), so that the stop 33 is forcibly pressed forward by the cam 61 and is brought back by the spring arrangement 124 .

The control of a work cycle of the cold forming press is explained below with reference to FIG. 5 explained. In This diagram shows the rotation of the crankshaft on the abscissa and the movements of each Assemblies of the cold forming press plotted on the ordinate. The actual movements are there not necessarily shown to scale.

The lower curve 181 represents the movement of the press slide 16 , which takes place essentially harmoniously over a complete rotation of the crankshaft 13 through 360 °. The rotation of the crankshaft begins in the diagram in front dead center at 0 °. The rear dead center of the crankshaft is 180 °.

The curve 182 shows the movement of the die holder 21 and thus the movable die 23. This begins its return movement from its front position after rotating the crankshaft by about 10 ° from point 183 and reaches its fully retracted position at point 184 after rotating the Crankshaft by about 100 °. The various parts are designed such that the ejection of a finished workpiece begins at about 62 ° at point 186. At about 110 ° of the rotation of the crankshaft at point 187 , the die holder 21 begins its movement in the direction of the stationary die 12 and reaches the gripping position between 170 ° and 190 ° and points 188 and 189. The exact gripping position depends on the size of the ball to be produced and this in turn depends on the size of the workpiece 28 to be deformed in the cold forming press.

The cam 61 is designed in such a way that the movable die 23 remains in the 200 ° position from point 191 if a workpiece is not arranged in a suitable gripping position between the dies. The dwell time from point 191 prevents the movable die from coming into contact with the grippers even if a workpiece is not properly positioned between the dies. The dwell time of the movable die ends at approximately 265 ° at point 192, from which the stop 33 is withdrawn in order to enable the workpiece 28 to be deformed when the press carriage 16 takes the movable die 23 with it. The press slide 16 engages the movable die 23 at approximately 315 ° at point 193 of curve 182 and at point 184 of curve 181 of the press slide. The deformation of the workpiece takes place between this point and the front dead center at 360 °, i.e. corresponding to a rotation of the crankshaft of about 45 °.

The speed of the die 23 at the time a wire section 28 is gripped is determined exclusively by the shape of the cam 61. It is completely independent of the speed of the carriage 16. The cam 61 enables the die 23 to be advanced under the influence of the air pressure prevailing in the chamber 31 at a speed which is less than the speed of the carriage 16 at the time a wire section is detected 28 is. The speed of wear of the dies 12 and 23 is a function of the speed of the die 23 at the time of the first contact with the individual wire sections 28, since this speed determines to a large extent the local pressure that is exerted at the contact points between the rough ends of the wire sections and the working surfaces of the dies 12 and 23 are created. Although the wire sections 28 are shown as having smooth ends, in fact when they are sheared off, even with a closed ring shear device, irregularities occur on their surfaces. These lead to points or points of high surface pressure on the working surfaces of the dies when grasping the wire sections. Such a locally high surface pressure is the main cause of wear on the working surfaces of the dies. Since the first contact between the ends of the wire sections 28 and the dies 12 and 23 takes place while the die 23 is moving at a relatively low speed, the local surface pressures that occur are very much smaller than in the case of a high relative speed. However, the speed of the die 23 is sufficiently high to cause the wire sections 28 to deform sufficiently so that their shear edges are deformed and smooth contact surfaces are formed between the ends of the wire sections 28 and the dies 12 and 23. As a result, the deformation force is distributed over larger areas during the second phase, when the carriage 16 moves the die 23 in order to bring the wire section 28 into its final shape. In other words, the wire portions 28 are uniform in two phases to workpieces shape deforms the first phase results in a small deformation when the wire portion 28 is first gripped between the dies 12 and 23 and the die 23 having a through the shape of the cam 61 certain small speed moved during the second phase, the die 23 is moved by the carriage 16 at a speed determined by the speed of the shaft 13, since the the first detection of the wire portion 28 between this and the matrices occurring point or line contact 12 and 23 is converted into a surface contact in the first phase, destructive and wear-promoting pressures do not occur during the second phase of the deformation process,

although the cold forming press is operating at greater speed.

Comparative example

If, for example, a known cold compress according to DE-OS 27 28 647 at a speed of 600 work cycles per minute works, the speed of the movable die is at the time of the first detection of a section of wire when making 7.93 mm spheres was approximately 1283 mm / second and when making 6.35 mm balls, about 1270 mm / second. In the case of the cold forming press described above, which works at a considerably higher speed of 720 work cycles per minute the speed of the die 23 at the time of the first detection of a wire section 28 is approximately 648 mm / second when making 7.93 mm balls and about 457 mm / second when making 6.35 mm bullets. The reduced speed at

ίο

Making smaller balls relies on the fact that the cam 61 is shaped so that the movable die 23 is stopped and between points 191 and 192 (Fig. 5) to prevent damage in the event that none Workpiece is located between the dies, and that the point of the first detection of a smaller wire section required for smaller balls on the curve is closer to point 191 and the cam 61 has then already slowed the die 23 further.

The speed of the press slide and thus the speed of the movable die is at the beginning of the second phase, during which the main deformation of the wire section takes place known cold forming press about 990 mm / second at 600 work cycles per second and at 720 Work cycles per second working present cold forming press about 1180 mm / second.

In addition 5 sheets of drawings

Claims (4)

Patent claims: 1. Process for cold forming cylindrical wire sections into spherical, cylindrical ones or similar workpieces, the wire section having shear edges between a A pair of dies is formed into a workpiece of uniform shape, characterized in that that the wire section is initially pre-deformed with a relatively low deformation force and then in the same operation with increased deformation force into the final shape is brought. 2. Cold forming press for performing the method according to claim 1, with two relative to each other movable dies and a die drive, characterized in that the die drive when the dies (i2, 13) are moved together for pre-deforming the wire section (28), a smaller one Speed and at the end of the deformation a much higher speed at the beginning Has. 3. Cold forming press according to claim 2, characterized in that the die drive has two each having separate drive parts derived from the main drive of the press. 4. Cold forming press according to claim 3, characterized in that the die drive has a Cam (61) for moving the one movable die (23) during the pre-deformation and one Crank mechanism (13, 17) for moving the movable die (23) during the final deformation having.