DE102010008255A1 - Press and operating procedures for it - Google Patents

Abstract

A press for forming workpieces of flat material, in particular for molding body parts for vehicles, comprises a table (2) and a punch (3) movable against the table, comprising a first and a second support (2, 3) for each mold (4, 5) form. In a space between at least one of the carrier (3) and the attached mold (5) a plurality of supports (10) is arranged. Assembly places (9), to each of which one of the supports (10) can be fastened, are distributed in the intermediate space according to a regular grid.

Description

The present invention relates to a press for forming workpieces made of flat material, in particular for molding body parts for vehicles.

Such presses conventionally comprise a table and a punch movable against the table, each carrying a mold and pressed against each other with high force, typically hydraulically or mechanically driven, to three-dimensionally shape a sheet cut between the mold parts.

The presses used in the molding of body panels for motor vehicles produce pressing forces of many hundreds or even several thousand tons. These forces inevitably result in operation in an elastic deformation of the table and the punch and, to an even greater extent, the molds. In the generation of this deformation drive energy of the press is useless lost, d. H. the energy efficiency of the press is impaired. In addition, such deformations may result in a portion of a workpiece already being clamped between opposing portions of the dies, while in other portions of the workpiece, the molding has not yet been completed. The part of the pressing force, which accounts for the clamped areas of the workpiece, fizzles useless. An unfavorable deformation behavior of the tools therefore considerably increases the pressing force required to achieve a desired shape of the workpiece.

It is obvious that the manufacturing costs of press-formed parts can be reduced considerably if it is possible to minimize the proportion of the workpiece surface which is clamped between the forming tools before the shaping is completed. Since then the proportion of the pressing force, which acts in clamped areas of the workpiece and remains unused, is low, a low pressing force and a correspondingly inexpensive press is sufficient to form the workpieces. The lower the pressing force, the lower the bending of the molds resulting from it. Consequently, the power loss of the press can be kept low.

The object of the present invention is to provide a press with which these goals can be achieved.

The object is achieved by forming in a press for molding workpieces made of flat material, in particular for molding body parts for vehicles, with a table and a movable against the table punch, the table and stamp carriers for each mold, wherein in a space between at least one of these carriers and the mold attached thereto is arranged a plurality of supports, assembly stations, to each of which a support can be fastened, are distributed in the intermediate space according to a regular grid.

The assembly sites specified by the grid allow a fast and reproducible placement of the supports and thereby facilitate the finding of an optimized arrangement in which clamping and / or elastic deformation are minimized. In order to achieve this minimization, the supports are preferably arranged at the most heavily stressed points of the molding tool.

Conveniently, at least one support and preferably each support is designed as a force sensor in order to measure directly the forces occurring during a molding operation.

Preferably, a pressure distribution plate is disposed between each support and the mold. This allows the use of largely hollow, on their side facing away from the workpiece by ribs stiffened molds, without the arrangement of the ribs must be considered in the determination of the grid of the columns.

To set the grid, a grid plate with a plurality of holes is expediently arranged in the intermediate space between the carrier and the mold, wherein each mounting position is defined by one of the holes, which can accommodate one of the supports. The grid plate may also be assembled from a plurality of partial plates, each covering a part of the mutually facing surfaces of the carrier or of the mold, each with a plurality of holes.

Preferably, the grid plate is separated from the mold or from the carrier by an air gap, so that the force exerted on the mold force is transmitted exclusively via the supports.

The holes of the grid plate are preferably blind holes with a support facing the opening. As the supports partly protrude from these bores, it follows that the above-mentioned air gap in particular comes to rest between the grid plate and the carrier. The non-pierced part of the grid plate may expediently represent the above-mentioned force distribution plate. As a result, a closed surface of the grid plate rests against the mold, stiffening ribs of the mold can be placed largely freely; ie the possibilities for arranging these ribs are not limited by the use of the grid plate.

In order to minimize the deformation of the mold, preferably the density of the supports between a highly loaded area of the mold, in particular a region in which a strong three-dimensional deformation of the workpiece takes place, and the support higher than between a low-loaded region of the mold and the carrier ,

Due to the higher density of the columns in the heavily loaded area, the range of forces to which the individual supports are exposed during operation is limited. An optimized arrangement of the supports may be considered to be suitable for production if the ratio of the forces acting on the most heavily loaded and least stressed support during the molding of a workpiece falls below a suitably predetermined ratio of, for example, a maximum of two. If the ratio is greater than 2, it can usually be made smaller by replacing the most heavily loaded support with two supports at adjacent grid locations, or by omitting a support not required due to too little stress.

• – Anbringung von Kraftsensoren an einem Teil der Montageplätze;
• – Messen der während des Formens eines Werkstücks an den Kraftsensoren auftretenden Kräfte;
• – Hinzufügen einer Stütze, insbesondere eines Kraftsensors, an einem Montageplatz, der einem hochbelasteten Kraftsensor benachbart ist, und/oder
• – Entfernen eines gering belasteten Kraftsensors oder einer zu dem gering belasteten Kraftsensor benachbarten Stütze.

The invention therefore also provides a method for operating a press of the type described above, comprising the steps of:

• - Attachment of force sensors to a part of the assembly sites;
• - Measuring the forces occurring during the molding of a workpiece on the force sensors;
• - Adding a support, in particular a force sensor, at a mounting location, which is adjacent to a highly loaded force sensor, and / or
• - Removal of a low loaded force sensor or adjacent to the low loaded force sensor support.

After having been found in this way a suitable for the production arrangement of the supports, it is possible in principle to replace the supports designed as a force sensor by supports without force measuring function; Preferably, however, the force sensors also remain in place during manufacturing to allow monitoring of ongoing manufacturing.

A quick optimization of the arrangement of the supports is possible by estimating a force gradient at the assembly site of a heavily loaded force sensor, such as by forming the differences between the force applied to the highly loaded force sensor and the forces acting on adjacent force sensors, and the mounting location for the additional support Direction of the force gradient is selected offset against the mounting location of the highly loaded force sensor. This method is based on the idea that a strong force gradient is due to leverage forces acting in the mold. If the workpiece has a force on the mold z. B. exerted on the left of a first force sensor and the right of the first second force sensor is arranged, the force causes due to acting as a two-armed lever mold a relief of the second and a greater load of the first sensor. By placing the additional support in the direction of the force gradient, in this case to the left of the highly loaded first force sensor, the leverage is reduced, and a more uniform distribution of force is the result. In this case, the first force sensor can remain in place, or it can be replaced with the new one.

Further features and advantages of the invention will become apparent from the following description of embodiments with reference to the accompanying figures. Show it:

1 a schematic view of a press according to the invention;

2 a schematic view of a equipped with force sensors grid plate; and

3 a schematic plan view of a portion of a grid plate mounted thereon with force sensors for illustrating force gradients occurring between pairs of sensors.

1 shows a schematic side view of a press according to the present invention. The press comprises a portal in a manner known per se 1 with a stationary table 2 and one above the table 2 vertically movable, mechanically or hydraulically driven punch 3 , table 2 and stamp 3 are with complementary molds 4 . 5 stocked. At one of the molds, here the upper tool 5 , is a sheet metal blank to be processed 6 attached. The press is in a position immediately before the onset of blank deformation 6 shown.

Between the stamp 3 and the mold attached to it 5 is a grid plate 8th with a plurality of grid openings 9 some of which are empty and others with force sensors 10 are equipped. The force sensors 10 are between the stamp 3 and the mold 5 clamped, z. B. with the help of in 1 not shown screws, the openings of the mold 5 prevail and in thread of the punch 3 intervention. This causes the force sensors 10 constantly pressure-loaded, even if the mold 5 without contact with the complementary tool 4 freely hanging down.

The grid openings 9 are blind holes leading to the stamp 3 are open. A the mold 5 facing closed side of the grid plate distributed over the force sensors 10 transmitted force of the punch in the lateral direction, so that the force is also efficient on the mold 5 can be transmitted when the force sensors against stiffening ribs 15 are laterally offset at the back of the mold.

The force sensors 10 protrude from the grid openings 9 out, leaving an air gap 7 the grid plate 8th from the stamp 3 separates. The power of the stamp 3 is therefore only via the force sensors 10 on the mold 5 and their distribution across the effective cross-sectional area of the mold is fully measurable.

From the consideration of 1 It is immediately apparent that the forces occurring during deformation are generally not uniform across the effective surfaces of the dies 4 . 5 are distributed. There are areas, in the example of the 1 about a narrow area 11 on the left edge of the molds 4 . 5 where the three-dimensional deformation of the blank 6 is very strong, a central area 12 with low deformation and a right area 13 with mediocre deformation. The resistance that the cut 6 the movement of the stamp 3 Accordingly, is not uniform over the surface of the blank accordingly 6 distributed but maximally in the left border area 11 and minimal in the central area 12 , However, if the stamp 3 a homogeneously distributed over its entire cross-sectional area pressure on the mold 5 Exercises, can lack of back pressure of the blank 6 in the central area 12 to a deflection of the mold 5 to lead. The consequence of this is that the cut 6 in the central area 12 between the molds 4 and 5 is clamped before this in the more deforming areas 11 . 13 happens. Consequently, only part of the pressing force of the punch is left 3 available to the intended deformation of the blank 6 in the fields of 11 . 13 bring about. If no appropriate countermeasures are taken, therefore, the press must be dimensioned so strong that after the production of the clamping in the area 12 on the areas 11 . 13 attributable remainder of their pressing force for the desired deformation of the blank 6 sufficient.

The press according to the invention allows the elastic bending of the molds 4 . 5 or their carriers, the table 2 and the stamp 3 to avoid or to a previously in the shaping of the molds 4 . 5 to limit the calculated amount by the force sensors 10 or other rigid props in the grid openings 9 can be distributed quickly and reproducibly in a manner adapted to the distribution of the molding forces. As in 1 shown is the density of the sensors 10 in that area 11 with the highest deformation highest and in the low deformation area 12 the lowest. The screening of the plate 8th allows the position of the sensors 10 quickly changing out of a given distribution of force sensors 10 To measure the resulting forces and reproducibly restore the best under various investigated distributions after completion of the measurements.

2 shows an example of a possible distribution of force sensors 10 on the grid plate 8th which may result as a result of such a series of measurements. Again, the density of the sensors 10 in a front left edge area 11 relatively high, in a central area 12 low and moderate in a right rear area 13 ,

The grid plate 8th can extend over the entire effective cross-sectional area of the stamp 3 or of the mold 5 extend; but it is also conceivable, this cross-sectional area with several adjoining grid plates 8th To cover.

A rough estimate of which area of a grid plate is denser and which area is less dense with force sensors 10 should be fitted, is based on a simple consideration of the molds 4 . 5 possible. An individual decision, which opening 9 the grid plate 8th with a force sensor 10 should be equipped and which not, but requires either elaborate calculations or optimization.

A concept for an optimization method is described below with reference to FIG 3 shown.

An initial distribution starting from the optimization can already be roughly related to the distribution of strongly and less strongly deforming areas on the forming tools 4 . 5 be adjusted; but it is also conceivable to start from a standard distribution, in which all force sensors 10 after a regular pattern in the grid openings 9 are distributed. 3 shows such a standard distribution, the force sensors 10-i , i = 1, 2, ..., are arranged in a uniform square grid whose edge length in each case four times the distance between adjacent grid openings 9 equivalent. An ellipse 14 shows the location of a region of the molds 4 . 5 in which the deformation resistance of a sheet metal blank to be machined 6 is especially big. The in this area 14 between the molds 4 . 5 acting force is distributed mainly to the area 14 nearest adjacent force sensors 10-1 . 10-2 . 10-4 . 10-5 . 10-7 . 10-8 , where the most heavily loaded is obviously the area 14 immediately adjacent sensor 10-5 will be. The rigidity of the mold 5 may in particular cause the force sensor 10-5 acts as a pivot point of a two-armed lever from which a lever arm to the area 14 extends and the opposite to the force sensor 10-6 , This two-armed lever causes by the in the area 14 transmitted pressure the sensor 10-6 is relieved, and the sensor 10-5 in addition to that in the area 14 transmitted pressure and the discharge of the sensor 10-6 must wear. It is obvious that the occurring bending moments to a strong undesirable deformation of the mold 5 being able to lead.

In order to detect and compensate for these cases, the difference of the forces measured by them is calculated for each pair of two neighboring force sensors. In 3 are the differences on the central sensor 10-5 and its neighbor sensors 10-i , i ≠ 5 acting forces respectively at the neighboring sensors as force gradients ΔFi, wherein the length of each force gradient ΔFi is proportional to the difference of the forces and its direction parallel to a connecting line between the respective sensors. The peak of each force gradient ΔFi points in the direction of that of the two sensors, which is exposed to the higher force. The sum of the force gradients ΔFi is calculated; it is a vector ΣF at the central sensor 10-5 applied. The vector ΣF points in the direction in which an additional sensor 10-10 is to be arranged. The larger ΣF, the closer to the central sensor 10-5 becomes the new sensor 10-10 placed.

Instead of using a new, additional force sensor, the central sensor can also be used 10-5 be moved in the direction of the vector ΣF. Which of the two options is chosen, the ratio of the individual sensors 10 acting forces are made dependent. When the on the central sensor 10-5 acting force significantly greater than an average of the surrounding sensors 10-i acting forces, or if it is greater by a predetermined factor than the force acting on the least loaded sensor, then the addition of the sensor results 10-10 to that this and the central sensor 10-5 significantly less burden than before the central sensor 10-5 alone, and that the ratio between the forces on the most loaded and lowest loaded sensor decreases. If none of the above conditions is met, the addition of the sensor may occur 10-10 cause it and the central sensor are significantly under-loaded; in this case, one becomes more the central sensor 10-5 move in the direction of ΣF.

During an optimization run, each sensor is selected once as a central sensor.

In order to limit the number of sensors, under-loaded sensors can be removed.

By performing optimization passes multiple times, an array of sensors may finally be obtained in which the ratio between the most heavily loaded sensor measured force and the lowest loaded sensor is below a predetermined threshold of, for example, 2. So can the deformations of the tools 4 . 5 be kept within tolerable limits and the press force of the press is used efficiently.

After the arrangement of the sensors 10 has been optimized, it would in principle be possible to replace them with supports without sensor function. Appropriately, however, remain the sensors during series production 10 at their optimized places, to those at the processing of each individual blank 6 to measure forces occurring in series production. By deviations of these forces from those obtained during the optimization, errors such as a defect of the blank can be obtained 6 or one of the molds 4 . 5 be recognized immediately.

LIST OF REFERENCE NUMBERS

1

portal

2

table

3

stamp

4

mold

5

mold

6

sheet metal blank

7

gap

8th

grid plate

9

screen door

10

force sensor

11

left border area

12

central area

13

right area

14

ellipse

15

rib

Claims (10)

Press for forming workpieces from flat material, in particular for molding body parts for vehicles, with a table ( 2 ) and a movable against the table punch ( 3 ) comprising a first and a second carrier ( 2 . 3 ) For each a mold ( 4 . 5 ), wherein in a space between at least one of the carrier ( 3 ) and the mold attached thereto ( 5 ) a plurality of supports ( 10 ), characterized in that mounting places ( 9 ), on each of which one of the supports ( 10 ) is fastened, are distributed in the space according to a regular grid. Press according to claim 1, characterized in that at least one of the supports ( 10 ) as force sensor ( 10 ) is trained. Press according to claim 1 or 2, characterized in that a pressure distribution plate ( 8th ) between each support ( 10 ) and the mold ( 5 ) is arranged. Press according to claim 1 or 2, characterized in that in the intermediate space a grid plate ( 8th ), each mounting place ( 9 ) through a hole ( 9 ) of the grid plate ( 8th ) is defined. Press according to claim 4, characterized in that the grid plate ( 8th ) of the mold ( 5 ) or from the carrier ( 3 ) through an air gap ( 7 ) is disconnected. Press according to claim 4 or 5, characterized in that the bores ( 9 ) of the grid plate ( 8th ) Are blind holes with an opening facing the carrier. Press according to one of the preceding claims, characterized in that the density of the supports ( 10 ) between a heavily loaded area ( 11 ) of the molding tool ( 5 ) and the carrier ( 3 ) is higher than between a lightly loaded area ( 12 ) of the molding tool ( 5 ) and the carrier ( 3 ). Press according to one of the preceding claims, characterized in that the force generated during the molding of a workpiece ( 6 ) on the most heavily loaded prop ( 10 ) is at most twice as large as that on the least loaded column ( 10 ) Acting force. Method for operating a press according to one of the preceding claims, comprising the steps of: attaching force sensors ( 10 ) at a part of the assembly sites ( 9 ), Measuring during the molding of a workpiece ( 6 ) on the force sensors ( 10 ) occurring forces; Add a support ( 10-10 ) on a high-load force sensor ( 10-5 ) adjacent assembly site ( 9 ), and / or removing a low loaded force sensor or a support adjacent to the lightly loaded force sensor. A method according to claim 9, characterized in that a force gradient (☐F6, ☐F) at the assembly site of a high-load force sensor ( 10-5 ) and the installation site ( 9 ) for the additional support ( 10-10 ) in the direction of the force gradient (□ F6, □ F) against the mounting position of the highly loaded force sensor ( 10-5 ) offset is selected.

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