DE19711162A1

DE19711162A1 - Tool system for hydraulic forming of sheet

Info

Publication number: DE19711162A1
Application number: DE1997111162
Authority: DE
Inventors: Thomas Dipl Ing Weidner; Matthias Prof Dr Ing Kleiner
Original assignee: Individual
Current assignee: KLEINER, MATTHIAS, PROF. DR- ING., 58739 WICKEDE,
Priority date: 1997-03-18
Filing date: 1997-03-18
Publication date: 1998-09-24

Abstract

The tool system produces three-dimensional components from flat metallic blanks by hydraulic sheet forming. The working fluid is sealed in by a two-stage sealing system. During preliminary forming at not more than 200 bar. The low pressure seal (4) is effective. During pressing at not more than 2000 bar, the high pressure seal (5) lies against the traction ring and prevents the fluid leaking out. The system consists of a clamping plate (1) supported by pistons (2) on a holding-down plate (3), and hydraulic devices to move the plates relative to each other.

Description

Die laufenden Arbeiten innerhalb der Forschung zur Hydroblechumformung (HBU) haben ge zeigt, daß bisher eingesetzte einstufige konventionelle Dichtungssysteme zwar eingeschränkt praktikabel sind, doch sobald der Wirkmediendruck die Grenzen der Standardhydraulik über schreitet die Prozeßdurchführung mit erheblichen technischen Schwierigkeiten verbunden ist. Die Ursache hierfür liege in der Tatsache, daß die Dichtung zwei sich widersprechende Eigen schaften aufweisen muß:The ongoing work within the research on hydraulic sheet metal forming (HBU) has been shows that previously used single-stage conventional sealing systems are limited are practicable, but as soon as the active medium pressure exceeds the limits of standard hydraulics the process implementation is associated with considerable technical difficulties. The reason for this lies in the fact that the seal has two contradicting properties must have:

Während der Vorformung (p_Umform ≦ 200 bar) kann es im Einzugsflansch, dort erfolgt übli cherweise die Abdichtung, zu primärer Faltenbildung kommen. In diese Phase muß die Dich tung eine hohe Rückfederung ermöglichen um so auch bei relativ großen Spaltmaßen die Dichtkräfte aufbringen zu können, die zur Aufrechterhaltung der Dichtfunktion nötig sind. Das heißt letztendlich, daß die Dichtung aus einem ausreichend elastischen Material bestehen sollte. Eine zusätzliche Beanspruchung in dieser Phase stellt die Relativbewegung des Blechs zur Dichtung dar, was zusätzlich die Forderung nach ausreichender Verschleißfestigkeit der Dich tung aufkommen läßt.During preforming (p _forming ≦ 200 bar), primary wrinkling can occur in the feed flange, where sealing is usually carried out. In this phase, the device must enable you to achieve a high spring-back so that the sealing forces that are necessary to maintain the sealing function can be applied even with relatively large gap dimensions. Ultimately, this means that the seal should consist of a sufficiently elastic material. An additional stress in this phase is the relative movement of the sheet metal to the seal, which additionally leads to the demand for sufficient wear resistance of the device.

Während des Prägevorgangs (p_Umform ( 2000 bar) ist davon auszugehen, daß das Blech sich relativ zur Dichtung aufgrund der hohen Reibungskräfte nicht mehr bewegt. Da die in der er sten Phase eventuell aufgetretenen Falten nur teilweise durch eine Erhöhung der Niederhalter kraft abgebaut werden können, existieren auch hier hohe Dichtspalten die abgedichtet werden müssen. In diesem Fall muß eine Extrusion der Dichtung in den Spalt vermieden werden. Das wiederum heißt, das die Dichtung aus einem harten extrusionsfesten Material bestehen muß.During the embossing process (p _forming (2000 bar), it can be assumed that the sheet no longer moves relative to the seal due to the high frictional forces, since the folds that may have occurred in the first phase can only be partially reduced by increasing the hold-down force , there are also high sealing gaps that must be sealed, in which case extrusion of the seal into the gap must be avoided, which in turn means that the seal must be made of a hard extrusion-resistant material.

Da ein technisches Dichtungssystem, welches die obengenannten Anforderungen erfüllt, derzeit nicht existent ist, wurde die Zweistufendichtung für die Hydroblechumformung entwickelt. Hierbei handelt es sich um eine Trennung der Funktionen, wodurch die obengenannten Anfor derungen zwischen zwei unterschiedlichen Dichtungen aufgeteilt werden.As a technical sealing system that meets the above requirements, currently does not exist, the two-stage seal was developed for the hydraulic sheet metal forming. This is a separation of functions, which means that the above requirements be divided between two different seals.

In der ersten Phase, der Vorformung, dichtet nur die Niederdruckdichtung (4) das Wirkmedi um gegenüber der Umwelt ab da die Hochdruckdichtung (5) noch nicht am Ziehringradius anliegt. Die Anforderungen an die Niederdruckdichtung (4) sind hier hohe Elastizität und Ver schleißfestigkeit, bedingt durch die eventuelle Faltenbildung und der Relativbewegung zwi schen Blech und Dichtung. Technische Dichtsysteme hierzu werden innerhalb der HBU- Forschungstätigkeiten getestet und sind zum Teil schon mit Erfolg erprobt worden.In the first phase, the preforming, only the low pressure seal ( 4 ) seals the active medium from the environment since the high pressure seal ( 5 ) is not yet in contact with the drawing ring radius. The requirements for the low pressure seal ( 4 ) here are high elasticity and wear resistance, due to the possible formation of folds and the relative movement between the plate and the seal. Technical sealing systems for this are tested within the HBU research activities and some have already been successfully tested.

Die zweite Phase, der Prägevorgang, ist dadurch gekennzeichnet, daß durch Verschieben der Niederhalterplatte gegenüber der Spannplatte die Hochdruckdichtung an den Ziehring angelegt wird, wodurch eine Entlastung der Niederdruckdichtung erfolgt. Da an Ziehringradius keine Falten auftreten und Relativbewegung nicht einsetzt handelt es sich hier um eine statische Ab dichtung mit sehr geringem oder keinem Dichtspalt.The second phase, the embossing process, is characterized in that by moving the Hold-down plate opposite the clamping plate, the high-pressure seal is placed on the drawing ring , which relieves the pressure on the low pressure seal. Since there is no drawing ring radius Wrinkles occur and relative movement does not set in, this is a static ab Seal with very little or no sealing gap.

Systembedingt ergibt sich zusätzlich die Möglichkeit der Niederhalterregelung, wobei der Druck in den Zylinder (Abstützungen (8)) sowohl hydraulisch als auch pneumatisch geregelt werden kann. Eine Regelung ist in sofern sinnvoll, ca. über die Flächenpressung der Blechein zug beeinflußt werden kann, da sich in der Praxis gezeigt hat, daß bei fehlender Regelung je nach tribologischen Verhältnissen ein ungleichmäßiger Blecheinzug einstellen kann.Depending on the system, there is also the option of hold-down control, whereby the pressure in the cylinder (supports ( 8 )) can be controlled both hydraulically and pneumatically. A regulation is useful if it can be influenced, for example, by the surface pressure of the sheet metal, since it has been shown in practice that, in the absence of control, an uneven sheet feeding can occur depending on the tribological conditions.

Für den Fall, daß keine Regelung zum Einsatz kommt besteht die Möglichkeit die Zylinder zusammenzuschalten. Dadurch ist eine konstante Flächenpressung unter dem Niederhalter ge währleistet, die zu einem gleichmäßigen Blecheinzug beiträgt.In the event that no regulation is used, there is the possibility of the cylinders interconnect. This ensures a constant surface pressure under the hold-down device ensures that the sheet is fed in evenly.

Claims

1. Tool system for the production of three-dimensional components from flat, preferably as metallic semi-finished products (e.g. sheet metal) by the hydraulic sheet metal forming (HBU), characterized in that a two-stage sealing system is used to seal the active medium to the environment, during which Preforming (p _forming ≦ 200 bar) the low pressure seal ( 4 ) ensures the sealing function and at the time of stamping (p _forming ≦ 2000 bar) the high pressure seal ( 5 ) is placed on the drawing ring to prevent the pressure _{medium from} escaping.

2. Tool system according to claim 1, characterized in that this consists of a clamping plate ( 1 ), which is on the hold-down plate ( 3 ) via several pistons ( 2 ) pneuma table and / or hydraulically supported ( 8 ), the displacement between hold-down plate ( 3 ) and clamping plate ( 1 ) by the hydraulic and / or pneumatic systems.

3. Tool system according to claim 1, characterized in that the tool system is fastened via the clamping plate ( 1 ) in a press or in a machine tool specially developed for the HBU method.

4. Tool system according to claim 1, characterized in that the guide of the hold-down plate ( 3 ) centrally through the clamping plate ( 1 ) (as shown in the sketch), or can be realized by ge special guides.

5. Tool system according to claim 1, characterized in that a seal between the hold-down plate ( 3 ) and clamping plate ( 1 ) must be made in the low pressure area, which must enable a relative movement of the two components to each other.

6. Tool system according to claim 1, characterized in that the low pressure seal ( 4 ) in the preforming (p _forming ≦ 200 bar) takes over the sealing of the active medium between sheet metal ( 6 ) and hold-down plate ( 3 ) against the environment, with a relative movement between Low pressure seal ( 4 ) and sheet metal ( 6 ) must be made possible.

7. Tool system according to claim l, characterized in that the clamping plate ( 1 ) moves for embossing in such a way that the high-pressure seal ( 5 ) bears against the drawing ring, so that there is now a seal between the clamping plate ( 1 ) and sheet metal ( 6 ), whereby during embossing (p _forming ≦ 2000 bar) there is no relative movement between sheet metal ( 6 ) and high pressure seal ( 5 ).

8. Tool system according to claim 1, characterized in that a regulation of the hold-down force can be carried out by a separate supply with pressure medium of the individual hydraulic and / or pneumatic supports ( 8 ).

9. Tool system according to claim 1, characterized in that by the interconnection of the hydraulic and / or pneumatic supports ( 8 ) even even parallelism deviations between press table and ram can be compensated and so ei ne uniform surface pressure is achieved.

10. Tool system according to claim 1, characterized in that in the event of failure of the high pressure seal ( 5 ), the energy of the escaping liquid both through the low pressure seal ( 4 ) between the hold-down plate ( 3 ) and sheet metal ( 6 ), and also through the low pressure seal between Hold-down plate ( 3 ) and clamping plate ( 1 ) is reduced to a safe level.

11. Tool system according to claim 1, characterized in that by a modular rea lization of this tool concept an adaptation of the tool to different Die shapes can be made using components from tools that are no longer required can be reused.

12. Tool system according to claim 1, characterized in that the high-pressure seal ( 5 ) during the embossing process applies to the drawing ring radius, which can result in the fact that this seal with metallic material is plastically deformed at the transition between preforming and embossing process and it contact between the seal and the drawing ring, whereby an adaptation of the seal geometry when using thermoplastic or elastomeric materials caused by the active media pressure can be reversible.