DE102011111735A1 - Welding unit, useful for progressive tool or transfer tool of press, comprises a tool upper part, a tool lower part, a first electrode comprising a holder for holding an additional portion to be welded, a second electrode, and a receptacle - Google Patents

Abstract

The welding unit comprises a tool upper part (12) for attaching a press upper part, a tool lower part (14) for attaching a press table, a first electrode (16), which comprises a holder (18) for holding an additional portion to be welded, a second electrode (20) that is present opposite to the first electrode, and a receptacle for a sheet metal part at which the additional part is welded. The first electrode is surrounded by a ring nozzle, which is connected to a suction device for exhausting welding sparks. The first electrode is arranged on the tool lower part. The welding unit comprises a tool upper part (12) for attaching a press upper part, a tool lower part (14) for attaching a press table, a first electrode (16), which comprises a holder (18) for holding an additional portion to be welded, a second electrode (20) that is present opposite to the first electrode, and a receptacle for a sheet metal part at which the additional part is welded. The first electrode is surrounded by a ring nozzle, which is connected to a suction device for exhausting welding sparks. The first electrode is arranged on the tool lower part, and the second electrode is arranged on the tool upper part. The electrode is formed in an annular shape, and has a central centering pin that is made of ceramic and is resiliently mounted. One of the electrodes is resiliently mounted. The receptacle is formed on the tool as a support table for the sheet metal part. A capacitor is provided for a capacitor discharge welding. The welding unit is arranged in a progressive tool or a transfer tool having sheet processing units for punching and/or forming, where the processing units are arranged in series for successive conducting of sheet metal processing steps in a press. An independent claim is included for a method for processing a sheet metal part in a press by a sheet metal processing unit.

Description

The invention relates to a welding unit for a progressive tool or transfer tool of a press, having a tool top for attachment to a press top, a tool bottom for attachment to a press table, a first electrode having a support for holding an additional part to be welded, a second electrode, which first electrode and a receptacle for a sheet metal part to which the additional part is welded, according to the preamble of claim 1.

The invention further relates to a method for processing a sheet metal part in a press by means of at least one sheet metal processing unit, wherein in the press at least one welding unit is additionally arranged, with which an additional part is welded to the sheet metal part, according to the preamble of claim 10.

Sheet metal companies are producing increasingly complex sheet metal components, which are manufactured by successive punching and forming operations. These processes are often carried out in a so-called follow-on composite tool on a press. The sheet is processed step by step with each press stroke on a sheet processing unit and transported to the next step in a subsequent sheet metal processing unit on. With such a progressive tool complex sheet metal components are manufactured in a train of a coil and ejected at the output of the press.

It is desired to integrate further processing operations within the press.

From the DE 603 15 716 T2 or the DE 10 2009 045 252 A1 are generic welding units known for such progressive dies. With these welding units additional parts can be welded to a sheet metal part during a press stroke. Due to the clock of the press, which is usually in the range of one second, and the limited space in the press, achieving a good welding result is problematic.

The invention has for its object to provide a welding unit and a method for processing a sheet metal part in a press, with which an efficient welding can be done with very high quality.

According to the invention, the object is achieved on the one hand by a welding unit with the features of claim 1 and on the other hand by a method having the features of claim 10. Preferred embodiments are given in the dependent claims.

The welding unit according to the invention is characterized in that the first electrode is enclosed by an annular nozzle, which can be connected to a suction device for sucking up welding spatters.

A first aspect of the invention is to perform the welding step very quickly. Due to the limited processing time, high welding currents and high pressure forces are used during welding. This increases the risk of welding spatter during the pressing of the part to be welded into the molten material. Therefore, according to the invention, a suction of the weld spatter is provided during welding.

According to a further aspect, this is achieved in an efficient and compact manner in that an annular nozzle is arranged around the first electrode, which receives the additional part to be welded, which can be connected to a suction device for sucking off weld spatters. The suction device may be a suction pump or a vacuum source.

The invention achieves a clean and thus exact welding without contamination of the surrounding surface of the sheet metal component.

A preferred embodiment of the invention consists in that the first electrode is arranged on the lower tool part and the second electrode on the upper part of the tool. In this case, the first electrode for receiving the additional part is formed. The additional part can thus be placed on the first electrode. This facilitates feeding and positioning of the attachment on the electrode.

It is further advantageous according to an embodiment of the invention that at least one electrode is annular and has a central centering pin. The centering pin is particularly useful when an annular additional part, such as a nut, a ring or a sleeve to be welded. The centering pin ensures a central adjustment of the additional part in the electrode. Both electrodes may also preferably have a centering pin, which is particularly advantageous when the sheet-metal part has a punched opening in the region of the annular additional part to be welded. Thus, the sheet metal part can be adjusted to the upper centering pin.

A particularly wear-reducing embodiment of the invention is that the centering pin is formed of ceramic. It can in particular standard ceramic pins are used, as used in other welding devices.

A further reduction in wear results according to a variant of the invention in that the centering pin is resiliently mounted. By a resilient mounting in particular an overload during the stroke movement of the two tool halves can be avoided.

A particularly good maintainability results according to the invention in that at least one of the electrodes is resiliently mounted. By a resilient mounting of the electrodes can be ensured that the electrodes always protrude to a certain extent. As a result, the effort for frequent regrinding of the electrode can be avoided or at least reduced. In addition, overstressing of the electrodes by the lifting movement is also avoided by the resilient mounting of the electrodes.

For adjusting the sheet metal part in the welding unit a variety of adjusting devices can be used, in particular stop bars. It is particularly advantageous according to the invention that the receptacle is formed on the tool as a support table for the sheet metal part. This allows a large-scale recording and mounting of the sheet metal part.

According to a further embodiment of the invention, it is preferred that at least one capacitor is provided for a capacitor discharge welding. The effort for conventional welding power generators is avoided. In addition, capacitor discharge welding can provide a high welding current for a short time. The welding energy is charged in the capacitor device. By moving together the two parts to be welded, the capacitor is discharged in fractions of a second, wherein in the region of the sheet metal part and the adjacent additional part, the material is melted by the welding current. By a corresponding compression of the two parts with a pressure force of preferably two to three tons, a reliable, solid material connection is achieved. Other types of resistance welding may be used, in particular, medium frequency welding.

A further preferred embodiment of the welding unit according to the invention is that it is arranged in a follow-on composite tool or a transfer tool with a plurality of sheet metal processing units, in particular for punching and / or forming, which are arranged in series one behind the other for performing sheet metal processing steps in a press. The press is preferably a servo press, in which the course of the press stroke is adjustable.

In the previous sheet metal processing units, a cutting is performed by punching, while further cold forming can be carried out by further forming operations, such as bending, deep drawing, drawing, upsetting, etc. In this case, the sheet metal part is cut to length from a coil in a known manner at each press stroke and transferred from a processing unit to the next processing unit within the press. Within this processing sequence or preferably at the end of the sheet metal processing steps, the welding unit according to the invention is provided, so that in addition to the sheet metal processing steps, one or more welding steps can be performed.

The method according to the invention is characterized in that, during welding, spatters are sucked off via an annular nozzle, which is arranged around an electrode. As a result, a total of high-quality welding is achieved, with contamination of the surrounding areas is avoided.

The invention will be further explained with reference to a preferred embodiment, which is shown schematically in the accompanying drawing. The single drawing figure shows a schematic cross section through a welding unit according to the invention.

The illustrated welding unit 10 includes a tool shell 12 for attachment to a press upper part and a lower tool part 14 for attachment to a press table. At the lower tool part 14 is a changeable first electrode 16 arranged, which in a sleeve-shaped electrode socket 30 is releasably used. As a holder 18 for inserting a threaded nut as an additional part 5 into the first electrode 16 is formed in this one central recess. In this holder 18 a lower ceramic centering pin protrudes into the electrode base 30 is mounted resiliently and axially displaceably via a lower bearing spring. Compressed air can be introduced into the area below the lower centering pin via a pneumatic channel, so that this axially out of the first electrode 16 can be moved out to the threaded nut as an additional part 5 take. The feeding of the additional part 5 takes place from the side directly to the lower tool part 14 ,

The electrode socket 30 is axially displaceable via a bearing bar 32 stored, which via a printing device 34 , which in particular a Gas spring is, axially against the upper tool 12 is tensionable.

Around the annular first electrode 16 is at a distance of 1 to 3 mm, a ring housing 24 arranged, being between the ring housing 24 and the central first electrode 16 an annular gap is formed. The annular gap serves as an annular nozzle, which is connected via a pressure line, not shown, with a suction device, in particular a suction pump, so that sucked over the annular nozzle during welding spatter can be removed and removed from the workpiece. In the area of the first electrode 16 Furthermore, a receptacle for receiving the sheet metal part is arranged. The exception is formed according to the contour of the male sheet metal part.

The power supply to the first electrode 16 via a current bridge 42 , which is constructed of rigid copper parts. Between the rigid electricity bridge 42 and a lower part 43 the axially movable first electrode 16 are flexible, U-shaped curved conduit sheets 48 arranged from copper. A cooling of the current-carrying parts via cooling channels in the current bridge 42 as well as a cooling hose 52 , over which cooling liquid from the current bridge 42 to the electrode socket 30 is directed.

On the tool shell 12 is corresponding to the first electrode 16 a plate-shaped second electrode 20 arranged. This second electrode 20 is on a base plate 50 attached, which over arcuate conduit sheets 48 made of copper with an electrode connection plate 44 connected is. The electrode connection plate 44 is at a collapse of the upper tool 12 with the tool lower part 14 on a press stroke over the connection 46 electrically with the current bridge 42 to the lower tool part 14 connectable.

The second electrode 20 has a center hole through which an upper centering pin protrudes. The upper centering pin is resilient against the base plate via an upper bearing spring 50 stored. As a result, a wear compensation of the second electrode 20 reached. Via a lateral cooling connection, a cooling fluid to the second electrode 20 and its live parts are passed to cool the electrode components.

The welding current energy is provided via a capacitor device, not shown, through which a capacitor discharge welding is feasible. In an initial state are the tool upper part 12 and the lower tool part 14 moved apart. The lower centering pin is extended axially by introducing compressed air via the pneumatic channel. In this position, the lower centering reliably a threaded nut as an additional part 5 take up. Then, by venting the lower centering pin with the additional part 5 drove down, with the additional part 5 in the annular first electrode 16 is positioned with the hole-shaped receptacle. After feeding the sheet metal part to the recording, the tool shell 12 and the lower tool part 14 driven against each other due to the movement of the presses. In this case, the welding current energy is released from the capacitor at a given time, wherein between the sheet metal part and the additional part 5 at the first electrode 16 and the second electrode 20 due to the flowing electric current, a defined melting of the material takes place. Within a fraction of a second, the additional part becomes 5 through the printing device 34 pressed into the molten bath, creating a solid material-liquid compound. The additional part 5 is pressed with a pressure force of two to three tons against the sheet metal part. Arising spatters are about the first formed electrode via the formed annular nozzle 16 sucked around and removed from the workpiece.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 60315716 T2 [0005]
• DE 102009045252 A1 [0005]

Claims (10)

Welding unit for a false jointing tool or a transfer tool of a press, with - a tool upper part ( 12 ) for attachment to a press upper part, - a tool lower part ( 14 ) for attachment to a press table, - a first electrode ( 16 ), which a holder ( 18 ) for holding an additional part to be welded ( 5 ), - a second electrode ( 20 ), which of the first electrode ( 16 ), and - a receptacle for a sheet metal part, on which the additional part ( 5 ) is welded, characterized in that around the first electrode ( 16 ) is enclosed by an annular nozzle, which is connectable with a suction device for sucking off weld spatter. Welding unit according to claim 1, characterized in that the first electrode ( 16 ) on the tool lower part ( 14 ) and the second electrode ( 20 ) on the tool upper part ( 12 ) are arranged. Welding unit according to claim 1 or 2, characterized in that first an electrode ( 16 . 20 ) is annular and has a central centering pin. Welding unit according to claim 3, characterized in that the centering pin is formed of ceramic. Welding unit according to claim 3 or 4, characterized in that the centering pin is resiliently mounted. Welding unit according to one of claims 1 to 5, characterized in that at least one of the electrodes ( 16 . 20 ) is spring-mounted. Welding unit according to one of claims 1 to 6, characterized in that the receptacle on the tool ( 14 ) is designed as a support table for the sheet metal part. Welding unit according to one of claims 1 to 7, characterized in that at least one capacitor is provided for a capacitor discharge welding. Welding unit according to one of claims 1 to 8, characterized in that it is arranged in a follow-on composite tool or a transfer tool with a plurality of sheet metal processing units, in particular for punching and / or forming, which are arranged in series one behind the other for successive implementation of sheet metal processing steps in a press , Method for processing a sheet-metal part in a press by means of at least one sheet-metal processing unit, wherein in the press additionally at least one welding unit ( 10 ) is arranged, with which an additional part ( 5 ) is welded to the sheet metal part, characterized in that during welding welding spatter are sucked off via an annular nozzle, which around an electrode ( 16 ) is arranged around.

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