EP0367035B1 - Press or punching machine - Google Patents

Abstract

The invention relates to a press or punching machine having a ram which carries a top tool half and whose plunging depth is adjustable and a press table which is arranged below the ram and carries the associated bottom tool half, and a control device for controlling the plunging depth of the ram during operation of the press or punching machine, which control device has at least one measuring pick-up arranged on the tool. In order to always achieve a uniform operating result with the least possible susceptibility to trouble, the measuring pick-up is designed as a pressure pick-up and, opposite the underside of the top tool half, is arranged on the top side of the bottom tool half or, opposite the top side of the press table, is arranged on the underside of the bottom tool half. <IMAGE>

Description

The invention relates to a press or punch with a plunger carrying an upper tool half, the depth of which can be adjusted, and a press table arranged below the plunger and carrying the associated lower tool half and with a control device having at least one measuring sensor arranged on the tool for adjusting the Immersion depth of the ram when the press or punch is in operation.

Adjusting the plunger depth during operation is desirable because the plunger depth changes with the heating of the press or punch and the tool. This change in plunger depth can have a negative impact on the quality of the machined workpieces.

From DE-PS 27 31 084 a ram adjustment is known, which makes it possible with high-speed cutting presses that the depth of immersion of an upper tool in an associated lower tool also with increasing working speed, i.e. higher stroke rate, can be kept constant. In a built version of this ram adjustment, an inductive displacement transducer is arranged between the tools, with which the immersion depth is recorded directly and passed on to the control device. The ram height is readjusted by a setpoint / actual value comparison.

A disadvantage of the known press is that the ram adjustment does not take fluctuating material thicknesses into account, at least when using embossing tools. But even if the tool halves are regrinded after a certain amount of wear, the specified nominal value of the immersion depth is no longer correct, so that complex readjustments are necessary. Otherwise, the inductive displacement sensor sensitive to pollution, heating and external influences, which can lead to malfunctions.

It is therefore an object of the present invention to improve a press or punch of the type mentioned in such a way that a constant work result can always be achieved with the greatest possible low level of interference.

This object is achieved in that the sensor is designed as a pressure sensor and, opposite the underside of the upper tool half, is arranged on the upper side or, opposite the upper side of the press table, on the underside of the lower tool half.

In contrast to the prior art, the plunger depth is no longer controlled directly, but indirectly via the tool pressure. This makes it possible to achieve consistent work results when using punching tools as well as embossing tools, regardless of any machine conditions. In the case of punching tools, the measuring sensor is expediently arranged on the upper side of the lower half of the tool, so that it interacts with the underside of the upper half of the tool. The pressure acting on the pressure transducer when the two tool halves are moved together is a measure of the immersion depth of the cutting punch of the upper tool half in the die of the lower tool half. This pressure measurement, which only indirectly reflects the immersion depth, enables the tool load to be read off directly and the ram immersion depth to be increased for blunt tools. The pressure transducer is significantly less susceptible to wear than the known contactless inductive displacement transducers and less sensitive to contamination, since there is no relative movement of two parts against one another, in which frictional forces could act.

If an embossing tool is inserted into the press, the immersion depth of the embossing die of the upper tool half in the die of the lower tool half is not so important; it is rather the goal to always keep the surface of the workpiece looking the same. If the pressure sensor is now arranged on the underside of the lower half of the tool and interacts with the top of the press table, the pressure that the stamping die exerts on the material is measured. This pressure is a measure of the depth of penetration of the die into the material, which must be distinguished from the depth of immersion of the die in the die. For a constant embossing result, it is important that the depth of penetration of the stamp into the material remains constant over the entire work process, regardless of any machine parameters or material thickness fluctuations. The invention is based on the finding that a constant work result can only be achieved by moving away from the displacement measurement and by using the pressure measurement, both for punched and embossed workpieces.

In the case of larger tools, it may be advantageous to arrange several pressure sensors on the lower half of the tool.

According to a preferred embodiment, the pressure sensor is formed from a pressure-resilient base body, in which a piezo element connected to the control device is embedded and the end of which is facing the top or the bottom of the lower tool half is covered with a rigid pressure plate. Since the piezo element is embedded in the elastically resilient base body, the pressure received by the pressure plate when the two tool halves are moved together is passed on uniformly to the piezo element, so that this pressure sensor is particularly insusceptible to faults.

It is favorable to produce the pressure body from a plastic, preferably a polyformaldehyde.

The pressure plate can be made of metal, preferably the same material as the tool.

If the tools are also to be used on other machines, it is advantageous if the pressure sensor is embedded in the lower half of the tool. Particularly good results can be achieved with punching tools if the pressure plate of the pressure transducer lies on the top of the lower half of the tool and is flush with the top of the lower half of the tool. As a result, the pressure plate of the pressure transducer is also ground to the same extent when regrinding the cutting punch, so that regrinding the tools has no influence on the measurements. In this embodiment of the pressure transducer, which is preferably provided for punching tools, the two tool halves are moved together during punching, the pressure between the two tool halves being measured directly, and not via the cutting punch, the material and the die. This means that with a thicker material where the cutting pressure is higher, a lower pressure is initially measured between the two tool halves, so that the material thickness during punching has no effect on the depth of the plunger and thus the work result.

When using embossing tools, the base body of the pressure transducer can also be conveniently embedded in the press table. The pressure plate of the pressure sensor then lies on the underside of the lower half of the tool. In this way, the pressure exerted by the stamp on the material and thus on the lower half of the tool is recorded. Even with different material thicknesses, this arrangement of the pressure sensor always ensures that the depth of penetration of the die into the material is always the same, so that here too the material thickness has no influence on the work result.

• Fig. 1 in einer schematischen Vorderansicht eine Stanze mit geschnittener unterer Werkzeughälfte, gemäß eines ersten Ausführungsbeispieles,
• Fig. 2 eine Seitenansicht der Presse aus Fig. 1,
• Fig. 3 in einer gleichen Ansicht wie Fig. 1 ein zweites Ausführungsbeispiel einer Presse, und
• Fig. 4 in gleicher Ansicht wie Fig. 1 ein drittes Ausfürungsbeispiel einer Presse.

Exemplary embodiments of the invention are explained in more detail below with reference to a drawing. Show it:

• 1 is a schematic front view of a punch with a cut lower tool half, according to a first embodiment,
• 2 is a side view of the press of FIG. 1,
• Fig. 3 in a same view as Fig. 1, a second embodiment of a press, and
• Fig. 4 in the same view as Fig. 1, a third embodiment of a press.

The presses or punches shown in the drawings have the same basic structure, which is described in more detail below.

All machines have a height-adjustable ram 1 and a press table 2 arranged underneath. The tappet 1 is connected to two connecting rods 3 which are mounted in a crankshaft 4 arranged in the upper part of the machine. The plunger 1 is adjustable in height with respect to the connecting rods 3, which is known per se. For this purpose, a known adjusting mechanism 5 is provided, which is connected to a servo motor 7 via a spline shaft 6. The spline 6 enables the servo motor 7 to be fixed in place while the spline can move with the stroke of the ram. By actuating the servo motor 7, the ram can be raised or lowered relative to the connecting rods 3 via the adjusting gear 5. The stroke is not adjusted, but rather the effective connecting rod length.

An upper tool half 8 is arranged on the underside of the ram 1, while a lower tool half 9 is arranged on the upper side of the press table 2. A feed device 10 is arranged to the side of the tools, with which sheet metal strips are intermittently passed between the tool halves.

Depending on the described embodiment, a pressure sensor 11 is provided in the area of the tool halves 8 and 9. The pressure sensor 11 consists of a base body 12 made of polyformaldehyde, in which a piezo element 13 is embedded. The base body 12 is covered by a metal pressure plate 14. The piezo element 13 is connected to an evaluation device 15, which forwards to a converter which transmits the pressure signal received by the piezo element, depending on whether the measured pressure is higher or lower than a predetermined target value. Depending on this, the converter 16 sends a signal to an angle encoder 17 of the servo motor 7, so that the ram height is adjusted via the servo motor and the angle gear, and the depth of the plunger is thereby regulated.

In the embodiment described in FIGS. 1 and 2, the base body 12 of the pressure transducer 11 is let into the lower tool half 9 and in such a way that the pressure plate 14 of the pressure transducer is arranged flush with the upper side 18 of the lower tool half 9. To achieve this, the pressure sensor 11 is installed in the lower tool half 9 before the lower tool half is ground flat on its upper side. From Fig. 1 it can be clearly seen that 9 individual punches 19 are arranged on the underside of the upper tool. In addition to the cutting dies, a pressure piece 20 is provided, which lies exactly above the pressure plate 14 of the pressure sensor 11. This arrangement of the pressure transducer 11 is particularly suitable when the tool halves 8 and 9 are provided for punching out workpieces, ie when they are provided with cutting dies 19 are. Then it depends on the fact that regardless of any machine or material conditions, the depth of immersion of the punch 19 in the associated dies of the lower tool half 9 is always the same, so that the workpieces are cut out cleanly. When the punch is heated, however, components such as the connecting rods 3 and the plunger 1 expand, so that the immersion depth of the cutting punches 19 would change if the plunger immersion depth were not readjusted. In the arrangement shown in FIG. 1, the pressure between the two tool halves is therefore measured, which is measured on the tool halves 8 and 9 during the cutting outside the cutting punches 19. If this measured pressure is too high, the plunger immersion depth must be reduced. The evaluation device 15, which carries out a corresponding setpoint / actual value comparison, effects a corresponding actuation of the servo motor 7 via the converter 16 and the angle encoder 17, which then reduces the immersion depth of the plunger 1 via the adjustment gear 5. The plunger immersion depth is increased in an analogous manner.

The second exemplary embodiment of a press according to the invention shown in FIG. 3 differs from the previously described exemplary embodiment essentially in that two pressure transducers 11 are provided which are embedded in the lower tool half 9 in such a way that their pressure plate 14 is flush with the underside 21 of the lower one Tool half 9 completes and touches the top 22 of the press table 2. The tool halves 8 and 9 are an embossing tool; Embossing dies 23 are accordingly provided in the upper tool half 8.

When working the press shown in Fig. 3, the plunger 1 moves up and down in the rhythm of the crankshaft 4, the dies 23 press on the material, not shown here, guided by the feed device 10 between the tool halves 8 and 9. The pressure exerted is from measured the two pressure transducers 11 and signaled to the evaluation device 15. If, when the press heats up, the pressure measured by the pressure transducers 11 increases during the operation of the press, the evaluation device 15 sends a signal to the servo motor 7 via the converter 16 and the angle encoder 17, whereupon the latter reduces the immersion depth of the plunger 1 via the adjustment gear 5 To the extent that the actual pressure continuously measured by the pressure sensor 11 corresponds to the predetermined target pressure. If the pressure is reduced, the depth of the plunger 1 is increased in an analogous manner. This ensures that the dies 23 always penetrate the material with the same pressure, so that all the stampings produced with the press have the same appearance, regardless of any material fluctuations, since these material fluctuations also increase or decrease the result in pressure measured by the pressure transducers and thus cause an adjustment of the plunger immersion depth.

4 shows a third exemplary embodiment in which the base body 12 of the pressure sensor 11 is let into the press table 2, so that the pressure plate 14 lies on the upper side 22 of the press table 2 and touches the lower side 21 of the lower tool half 9. In the exemplary embodiment shown in FIG. 4, the tool halves 8 and 9 are also designed as embossing tools. The operation of this press corresponds to the press shown in Fig. 3, however, both tool halves 8 and 9 can be exchanged for another tool without the pressure transducer 11 having to be replaced. If the press is to be converted, it is therefore only necessary to specify a new pressure setpoint for the evaluation device 15.

As shown in FIG. 3, several pressure sensors can also be arranged in the other exemplary embodiments. In the exemplary embodiment shown in FIG. 4, this is even recommended if tools of different sizes are used in a press, since then at least one pressure transducer is always arranged below the underside of the lower tool half.

Although the exemplary embodiments according to FIGS. 3 and 4 are described using embossing tools and the exemplary embodiment according to FIGS. 1 and 2 using a cutting tool, it is also conceivable to use cutting tools in the presses according to FIGS. 3 and 4 and in the press according to FIG. 1 and 2 to use an embossing tool or a combination of cutting and embossing tool.

It is also conceivable for the pressure body to be made of a material other than plastic, e.g. As rubber, to manufacture, a material of high elasticity is preferred, the tensile strength is 50-70 N / cm².

Claims (8)

1. Press or punch having a ram (1), which carries an upper die half (8) and the depth of penetration of which is adjustable, and a press platen (2) arranged underneath the ram and carrying the associated lower die half (9), and having a regulating device which possesses at least one measuring transducer (11) arranged on the die and which regulates the depth of penetration of the ram (1) during the operation of the press or punch, characterised in that the measuring transducer is designed as a pressure transducer (11) and is arranged opposite the underside of the upper die half (8) on the top side (18) of the lower die half (9), or opposite the top side (22) of the press platen (2) on the underside (21) of the lower die half (9).
2. Press or punch according to Claim 1, characterised in that a plurality of pressure transducers (11) are arranged on the lower die half (9).
3. Press or punch according to Claim 1 or 2, characterised in that the pressure transducer (11) is formed from a basic body (12) which is flexible elastically under pressure and in which is embedded a piezoelectric element (13) connected to the regulating device (5, 6, 7, 15, 16, 17) and which is covered with a rigid pressure plate (14) at its end facing the top side (18) or the underside (21) of the lower die half (9).
4. Press or punch according to one of Claims 1 to 3, characterised in that the pressure body (11) consists of plastic.
5. Press or punch according to one of Claims 1 to 4, characterised in that the pressure plate (14) consists of metal.
6. Press or punch according to one of Claims 1 to 5, characterised in that the basic body (12) of the pressure transducer (11) is recessed into the lower die half (9).
7. Press or punch according to one of Claims 1 to 6, characterised in that the pressure plate (14) of the pressure transducer (11) lies on the top side (18) of the lower die half (9) and is flush with the top side (18) of the lower die half.
8. Press or punch according to one of Claims 1 to 5, characterised in that the basic body (12) of the pressure transducer (11) is recessed into the press platen (2).

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