EP0428780A1 - Punch press with correction value input for the penetration depth and the feed length - Google Patents

Abstract

A punch press, which can be controlled by a control device to a setpoint characteristic (40) for the depth of penetration as a function of the number of strokes, is provided with a control input by means of which a correction value (W) can be entered. The press then operates at a new operating point (41). When the number of strokes changes, the control device forms a new operating characteristic (44) with the value (W) and the previous setpoint characteristic (40). Using such a punch press, punched parts can be produced with increased accuracy over the entire range of strokes. <IMAGE>

Description

The present invention relates to a punch press with stroke rate adjustment and a control device which contains a target characteristic, by means of which signals for an adjusting device can be generated according to the target characteristic, and by which setting direction an immersion depth adjustment of the punch of the punch press while the punch press is running, depending on the signals the control or regulating device takes place.

Furthermore, the invention relates to a punch press with stroke rate adjustment and a control device containing a target characteristic, by means of which signals for an adjusting device according to the target characteristic can be generated and by which adjusting device a feed length setting for the material to be punched while the punch press is running as a function of the signals the control or regulating device takes place.

In punching presses, changes in operating parameters such as the number of strokes, tools and workpieces always cause deviations from specified target values. Changes in the number of strokes have the effect that the inertial forces change, for example the inertial forces increase with increasing number of strokes. Small, elastic changes in the dimensions of moving parts of the press and changes in play in the bearings result in changes in the height of the tool, or the depth of immersion of the tools. difference Liche tools, which differ from each other in terms of their mass, also cause different inertia forces during operation, which, if necessary, add up with the aforementioned inertia forces, further lead to deviations from the specified target values. Specifically with regard to the immersion depth, the nature of the blank to be processed, for example its metallurgical properties, as well as the manufacture itself or the shape of a workpiece to be manufactured, play a major role.

Setpoint deviations also occur in the feed device, in which the dimension of the feed length deviates from a respectively predetermined setpoint, with increasing number of strokes and accelerated belt mass forming further sources of error.

From DE-PS 27 31 084 it is known to provide a punch press with an adjustable immersion depth of the ram or the tool with a control device. A characteristic curve is entered into this control or regulating device, which is intended to represent the immersion depth function as a function of the number of strokes per minute of the punch press. This characteristic curve serves as the setpoint. The measured immersion depth actual value is compared with this nominal value. If the actual value deviates, the control or regulating device carries out a correction in the direction of the setpoint.

In practice, however, it has been shown that such control or regulation does not always lead to satisfactory results. This is because the actual operating sizes of a press are subject to very complex changes during the passage of the stroke rate range, which will be explained in more detail below. The control device mentioned above is therefore often unable to deliver satisfactory results over the entire stroke rate range. This is all the more true since there is a desire to be able to produce stamped products with greater precision.

The invention seeks to remedy this. The invention as characterized in the claims solves the task of creating a punch press in which these disadvantages do not occur and in which parts can be produced with the desired precision over the entire range of strokes with each tool, in that the control device has an input means by means of which a value deviating from the target characteristic curve can be entered for the immersion depth at any number of strokes, and that the control or regulating device for generating the signals is designed in such a way that the entered value can be changed as a function of the stroke number and can be linked to the desired characteristic curve.

As described above, basically the same task also arises with regard to the feed length for the material to be punched. This object is achieved for the feed by means of the same general inventive idea in a punching machine of the type mentioned at the outset in that the control or regulating device has an input means by means of which a value for the feed length deviating from the nominal characteristic curve can be entered at any number of strokes and that the control or regulating device for generating the signals is designed in such a way that the entered value can be changed depending on the stroke rate and can be linked to the target characteristic curve.

Using the punch press according to the invention, precise punched parts can be produced over the entire stroke rate range. If - as is known - a low number of strokes of, for example, 100 strokes per minute is used to set the desired number of strokes along the tool-specific characteristic curve, immersion depth errors with a high number of strokes on the stamped parts become visible and measurable. By entering a value as a correction for the immersion depth, the error when the speed is approached can be visibly and measurably reduced. The open-loop or closed-loop control leaves the target characteristic curve that is predetermined per se. If the number of strokes is changed again, the control device regulates a new setpoint. The entered value is changed by the device and together with the fixed setpoint characteristic used to determine the immersion depth suitable for the new stroke rate.

The control or regulating device proceeds analogously when changing the target feed length value.

The invention is explained in more detail below with the aid of drawings which illustrate only one embodiment.

• Figuren 1-4 vereinfacht die hauptsächlichsten beweg­ten Teile einer Stanzpresse;
• Figur 5 ein Diagramm einer bekannten Regelungsein­richtung;
• Figur 6 eine erfindungsgemässe Regelungseinrichtung, und
• Figur 7 eine Kennlinie zur Illustration der Wirkung der Regelungseinrichtung gemäss Figur 6.

Show it:

• Figures 1-4 simplify the main moving parts of a punch press;
• Figure 5 is a diagram of a known control device;
• 6 shows a control device according to the invention, and
• FIG. 7 shows a characteristic curve to illustrate the effect of the control device according to FIG. 6.

For the time being, the problems relating to the immersion depth are explained with reference to FIGS. 1-4, which show in simplified form the parts of a punch press that are essential for understanding the invention. The crank arm 1, the levers 2, the adjusting spindles 3, the drive connecting rods 4, the plunger 5 and the table 6 are drawn from the punch press. WHS means the tool closing height. Furthermore, the deflection amount F and the play S are shown schematically in accordance with the respective operating states.

In Figure 1, a press is now shown, which with a stroke rate of 100 H / min. and is in operation without tools. The various bearings 7 are drawn as journal bearings and the game in each case is exaggerated. All components, in particular lever 2, act as rigid components and are therefore not deformed. The relative position of the bearing journal and the bearing bush, that is to say the location of the play in the bearing, is only determined by the plunger 5, ie by its weight. It can be seen that all components are pulled "down" by the plunger 5. The tool closing height WSH corresponds to the specified target tool closing height.

In Figure 2, the same machine is at a relatively high speed or high number of strokes, for example 1500 H / min. and again shown simplified without tools. This high number of strokes creates elastic deformations of work parts, the so-called dynamic suspension. This is shown schematically in FIG. 2 as the deflection of the levers 2. However, the tool closing height WSH must now be kept constant, since this ultimately has an effect on the immersion depth. In order to keep this tool closing height WSH constant in the dynamic suspension shown, the ram height would have to be corrected by the amount that corresponds to the dynamic suspension. This means that a height correction that is equal to the deflection amount would have to be carried out.

Figure 3 shows the same machine that with a stroke rate of 100 H / min. punches. The speed is therefore again the same as that of FIG. 1. In addition, the upper tool part 8, the lower tool part 9 and the workpiece, i.e. the tape 10 from which the product is punched and embossed is shown. The reference number 13 denotes a punched-out piece of material.

Due to the low speed of e.g. 100 h / min. analogous to the state of FIG. 1, no dynamic forces occur in the machine. However, due to the punching, embossing, i.e. generally the processing, forces which, as shown in FIG. 3, are directed upwards, which state is illustrated by the schematic representations of the individual bearings and the position of the levers. The source of errors here are the games, especially in the camps. In order to be able to perform a perfect punching, the entire game would first have to be saved. Since the plunger is "pushed up" here, the plunger adjustment would consequently have to be adjusted downwards by the amount s, so that the specified tool closing height WSH can again be maintained.

Figure 4 shows the machine with a high number of strokes, ie analogous to the number of strokes in FIG. 2. Because of the large dynamic forces (at approx. 300-400 H / min.) the game is run through and at the same time the dynamic suspension occurs analogously to FIG. In order to keep the tool closing height WSH constant again, the plunger adjustment would have to be corrected by the amount F + S.

From the explanations above it is clear that depending on the number of strokes, the tool and also the workpiece (e.g. metallurgical properties) the ram must have a different height position. It must also be noted that the height position is inaccurate for immersion depth measurements without punching.

FIG. 5 schematically shows a block diagram of a known regulation, which is basically based on FIG. 1 of DE-PS 27 31 084. The number of strokes is fed from a corresponding sensor 26 to a first element 20, in which a target characteristic curve is stored. Such a target characteristic curve is provided for each tool used. The target characteristic is programmable via an input 21 of the control device. The target characteristic curve e.g. represents the immersion depth as a function of the number of strokes. In a second element 22, a comparator, the target immersion depth emitted by the element 20 is compared with the actual immersion depth, which is measured by a sensor 25 on the motor 24 of the immersion depth adjustment. If the actual immersion depth adjustment deviates from the target immersion depth by a predetermined threshold value, the element 22 activates one of the switches 23 in order to actuate the motor for the immersion depth adjustment for raising or lowering the ram or tool. The actuation continues until the actual value is again adjusted to the setpoint within the control accuracy.

FIG. 6 shows roughly schematically how the control device of a punch press according to the invention can be designed. Only one element 30 of the control device is shown, which is basically the element 20 of Figure 5 corresponds. The other elements of FIG. 5 have been omitted from FIG. 6 for the sake of simplicity. These elements 22, 23, 24, 25 are basically of the same design in the control device according to FIG. 6 as in the known control device according to FIG. 5.

Element 30 also has a tool-specific target characteristic curve of a known type that has been programmed via input 21. It also has an input for a stroke-dependent signal from a sensor 26. An input or input means 31 is now provided, by means of which a value can be entered by which the immersion depth is corrected at the number of strokes present at the moment. This will be explained in more detail with reference to FIG. 7, which shows a nominal characteristic curve 40 in an immersion depth / stroke rate diagram. For the sake of simplicity, this nominal characteristic curve is shown as a straight line. While this is correct for a feed device, the target characteristic curve for the immersion depth will usually be parabolic. The schematic nominal characteristic curve shows the value to which the immersion depth is adjusted at the respective number of strokes.

However, it can be seen from the previous discussion of FIGS. 1-4 that the setpoint characteristic curve can inevitably only be an imperfect image of the complex real function. Correspondingly, the parts punched according to the nominal characteristic curve can show large deviations from the desired manufacturing tolerance, even - and especially - if the control device according to FIG. 5 follows the nominal value characteristic curve 40. The control device of the punch press according to the invention therefore has input 31, into which a value can be entered by which the control device detaches itself from the setpoint characteristic.

FIG. 7 shows how this manifests itself in the immersion depth / stroke diagram. At the number of strokes H 1, the operator of the stamping press was able to determine that the operation on the associated target characteristic point 42 does not give the desired precision of the stamped parts. The control device can receive a correction value via input 31 W can be entered. The punch press then operates at the operating point 41, which results from the nominal characteristic curve 40 and the entered correction value W. The value W can be entered using a wide variety of means, for example using a numerical keyboard as a digital value, using a variable resistor as an analog value or using ± keys in predetermined small steps. The type of input will depend on the design of the control device.

The example shown basically shows the value W; W can of course be larger or smaller or can also be effective on the other side of the nominal characteristic curve, so that an operating point 43 would result. If the precision of the parts achieved at the new operating point 41 is not satisfactory, a different value for W can of course be entered.

If the number of strokes is now changed, the value W is automatically changed by the control device. This can be done continuously, so that there is again a continuous curve (shown as curve 44 in dashed lines) between the stroke numbers H₁ to H₄ or H _max to H _min . This can be done in such a way that an additional characteristic curve is calculated from the known nominal value characteristic curve parameters, which in the example shown passes through the new operating point 41 and touches or intersects the nominal value characteristic curve at the minimum number of strokes. However, it is also possible to form corrected correction values W₂ to W₄ only for individual stroke numbers H₂ to H₄, the new "operating setpoint curve" which arises, for example, being step-like or being formed between the points by a straight line.

Preferably, the nominal characteristic curve 40 is parabolic for the immersion depth, and when it is changed, all parabolic parameters are recalculated starting from the value W set at any number of strokes, and a new nominal nominal characteristic curve is thus formed. In this case, the control device is of course preferably formed by a digital process control, which carries out the necessary calculations and the corresponding regulation.

However, FIG. 6 indicates, for example, how a configuration of the control device according to the invention can be achieved with little effort. The signal at the output 33 to the comparator 22 is formed in such a way that an adder / subtractor 35 links the basic value from the setpoint characteristic curve with the entered value W in order to obtain the new operating point. When the number of strokes changes, a second adder / subtractor 36 is activated, which from the previous new operating point 41 e.g. counts a constant K when the number of strokes drops or adds the constant K when the number of strokes increases.

Since the values W or the new target operating characteristic are generally valid for a certain time for a certain tool, the control device is preferably provided with a memory in which at least one value W, at most the entire new target operating characteristic and a number associated with the tool, can be stored are. This makes it possible to call up a tool that has already been used and has been driven with a changed setpoint characteristic curve and to start operation on the changed curve.

The above statements regarding the immersion depth also apply to the feed length. The corresponding setpoint characteristic curve can be a straight line. The principle of correction and the means used remain the same. Of course, only one of the corrections, that is, either the feed length or the immersion depth, can be carried out on a punch press. Preferably, however, both options are provided in the same punch press.

Claims (8)

1.Punching press with stroke rate adjustment and a control device containing a setpoint characteristic, by means of which signals for an adjustment device can be generated in accordance with the setpoint characteristic curve and by which setting device an immersion depth adjustment of the ram of the punch press while the punch press is running, depending on the signals from the control or Control device takes place, characterized in that the control or regulating device has an input means by means of which a value for the immersion depth deviating from the target characteristic can be entered at any number of strokes, and that the control or regulating device is designed to generate the signals in this way is that the entered value can be changed depending on the stroke rate and can be linked to the target characteristic. 2. Punching press according to claim 1, characterized in that the control device has a memory in which at least one entered value can be stored. 3. Punching press according to claim 1, characterized in that the control device is designed to link an input value with a parameter for the punching tool used. 4. Punching press according to one of claims 1 to 3, characterized in that a target characteristic curve can be stored in the form of a parabola in the control or regulating device and that the control or regulating device is designed for changing all the parabola parameters as a function of the stroke rate. 5. Punching press according to one of claims 1 to 4, characterized in that signals for a feed device of the punch press can be generated by the control or regulating device in accordance with a second nominal characteristic curve, that a value for the feed length of the material to be punched can be entered and that the control or regulating device for generating the signals for the feed device is designed such that the entered value can be changed depending on the stroke rate and can be linked to the target characteristic. 6.Punching press with stroke rate adjustment and a control device containing a setpoint characteristic, by means of which signals for an adjustment device can be generated according to the setpoint characteristic curve and by which setting device a feed length setting for the material to be punched while the punch press is running, depending on the signals from the control or control device, characterized in that the control or regulating device has an input means by means of which a value for the feed length deviating from the nominal characteristic curve can be entered at any number of strokes, and in that the control or regulating device for generating the signals in this way it is designed that the entered value can be changed depending on the stroke rate and can be linked to the target characteristic curve. 7. Punching press according to claim 6, characterized in that the control device has a memory in which at least one entered value can be stored. 8. punch press according to claim 7, characterized in that the control or regulating device is designed to link an input value with a parameter for the punching tool used.

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