EP0288705A2 - Method of making complicated sheet metal parts, and device for carrying out the method - Google Patents

Abstract

Method of making complicated sheet metal parts in one, two or more operation/operations, at least one operation comprising a plurality of processing steps. The sheet-metal blank is placed on the tool and the pressure is then increased continuously up to, for example, 800 bar, passing through different pressure phases, in the first phase a continued flow of the material into the recesses of the form tool taking place and, in the subsequent phase, the forming blank being trimmed in an intermediate stage at relatively low points of the tool, the material flowing further into the recess, corners and undercuts. The pressure is then increased until the end phase and the workpiece then undergoes final stamping, final trimming, perforation and/or edging. The pressure is then reduced and the sheet-metal part removed. (Figure 3). <IMAGE>

Description

The invention relates to a method for producing complex sheet metal parts according to the preamble of claim 1. The invention also relates to a tool for carrying out the method, that is to say for the pressure forming of such sheet metal parts with a shaping tool part which enables a deep-drawing process.

In conventional deep drawing, the sheet (blank) is placed on a die. A hold-down holds the circuit board. The descending deep-drawing stamp pulls the material over a rounded drawing edge into the drawing ring. A hollow part is created.

Rationalization and a greater variety of products, particularly in the automotive industry, and an increased use of lightweight construction have led to a large number of complicated deep-drawing molds, which pose problems for sheet metal manufacturers and sheet metal fabricators.

The limits of conventional deep drawing with rigid tools are now overcome with flexible tools that you work with active media and active energies (DIN 8584, Sheet 3 (5.1)).

In conventional deep drawing, in addition to high tensile stress in the frame, there are point-by-point stress concentrations, locally different wall thicknesses, fold formation, in particular second-order folds, and high tool costs, especially for irregular parts and for parts with undercuts.

The draw ratio is limited. For this reason, several three-part tools are necessary for the production of a sheet metal part, for example drawing tools, cutting tools, punching tools, folding tools, slide tools and demolding tools.

This results in high tool costs, i.e. high part costs with low quantities, which is particularly noticeable in prototypes and small series.

The invention has for its object to develop a method of the type mentioned in which a variety of separate drawing, cutting, punching, folding, etc. tools can be dispensed with to manufacture a sheet metal part.

To achieve this object, a method for producing complex sheet metal parts according to the preamble of claim 1 is proposed, which according to the invention has the features mentioned in the characterizing part of claim 1.

An advantageous embodiment of the method are mentioned in claims 2 to 4.

A tool for performing the method is characterized according to the invention by the features mentioned in claim 5.

Advantageous embodiments of this tool are mentioned in claims 6 to 15.

In the method according to the invention, all the manufacturing steps necessary for producing a sheet metal part are carried out in one or more tool parts and / or tools with the aid of a single tool.

• a) zunächst die Blechplatine aufgelegt,
• b) der Druck kontinuierlich bis beispielsweise 800 bar unter Durchlaufen von verschiedenen Druckphasen erhöht,
• c) in der ersten Phase die Randbeschneidung des Bleches zur Formplatine vorgenommen, wobei das Material in die Ver­tiefungen des Formwerkzeugs nachfließt,
• d) in der folgenden Phase die Formplatine an tieferen Stel­len des Werkzeugs zwischenbeschnitten, wobei der Werk­stoff weiter in die Vertiefungen, Ecken und Hinter­schneidungen nachfließt und der Druck bis zur Endphase erhöht wird,
• e) das Werkstück endgeprägt, endbeschnitten, gelocht, durch­gestellt und abgekantet.

In the method according to the invention, for example

• a) first put on the sheet metal board,
• b) the pressure is continuously increased up to, for example, 800 bar while passing through various pressure phases,
• c) in the first phase, the sheet metal is trimmed to form the blank, the material flowing into the recesses in the mold,
• d) in the following phase, the blank is cut at deeper points of the tool, the material continues to flow into the recesses, corners and undercuts and the pressure is increased until the final phase,
• e) the workpiece is finally embossed, trimmed, punched, put through and folded.

The above processes a) to e) are only an analysis of the process. The process itself is practically one.

The process is suitable for deep drawing with active media. It is also suitable for deep drawing with active energy (DIN 8584, sheet 3 (5.1)).

With the method according to the invention, all of the manufacturing stages required for the production of a sheet metal part, such as drawing, embossing, folding, throughput, hole, cutting, flanging, and other operations, such as a tool part, can be carried out in a pressing process, for example be performed. Of course, several tools or tool parts and one or more pressing operations are possible, but without the need for special tools, as was previously the case, namely drawing tools, cutting tools, drawing tools of the next level, drawing tools of the last level, or tools for trimming, folding or re-edging.

A hole is preferably punched against a pressure sufficient to shape the part geometry.

A tool is preferably provided for the pressure forming of such sheet metal parts with a shaping tool part which enables a deep-drawing process, the pressure being applied by active media, such as fluid-pressurized rubber or polyurethane membranes or rubber cushions, or exclusively by active energy, such as explosive forming or sound waves in the respective function as a counter tool.

• 1. während einer ersten Ziehstufe die Blechplatine beschnei­denden Werkzeugteile;
• 2. bei Druckerhöhung in einer zweiten Ziehstufe zwischenbe­schneidende Werkzeugteile, die ein weiteres Nachfließen des Werkstücks der vorgeformten Blechplatine ermöglichen;
• 3. bei weiterer Druckerhöhung das volle Ausformen des Werk­stücks ermöglichende Werkzeugteile mit einem nachgebenden Gegenhalter.

The tool expediently has a shaping tool part which may consist of several parts and which comprises, for example, the following parts:

• 1. tool parts trimming the sheet metal blank during a first drawing stage;
• 2. in the case of pressure increase in a second drawing stage, tool parts that cut in between, which allow the workpiece of the preformed sheet metal plate to flow further;
• 3. in the event of a further increase in pressure, the tool parts, which allow full shaping of the workpiece, with a resilient counter-holder.

So far, only stamping parts could be produced with such a press. Completely new in this area is the production of drawn parts with such a press, whereby there is only one counter tool, ie no actual tool.

Expediently, cut strips are arranged in the drawing trench for intermediate trimming in the case of block deformation or cavity deformation.

It is favorable that for intermediate and end trimming in the event of cavity deformation, the cut trench or the sheet metal holder or in the case of a divided tool, the tool elements are spring-loaded against an end resistance with an adjustable series resistor. It is thus possible that a circular hole is not produced in a phase which is followed by a deforming phase in which a previously formed circular hole would be undesirably deformed into an ellipse. Rather, in the method according to the invention, the part is first practically finished, before the spring yields when the spring counter pressure is exceeded, and the die cuts the hole.

The adjustable series resistor is expediently formed by a punch passing through a cutting ring, which is supported against a series resistor via a plate spring. In the case of large holes, however, a rigid cutting ring and a rigid insert are used.

In practice, the method or tool known for stamping and folding, which works against rigid mold blocks by means of a fluid-loaded membrane, is applied to deep-drawing dies or to dies that enable deep-drawing and trimming without counter-tools.

Compared to the known movable sheet metal holder, a rigid sheet metal holder can also be used according to the invention, or work is carried out entirely without a sheet metal holder.

The cutting strips in the molding tool also have no counterpart in the prior art. The processing is unusually gentle.

For demolding, the tool part carrying the undercuts can be designed as a separately operable loose part.

If the sheet metal part is pressed in several stages, for example drawn, punched and / or cut, etc., loose parts made of different materials can be inserted into the shaping tool part in order to allow the material to flow again or to be able to press with uniform pressure.

During the pressing process, for example, a membrane is pressurized with oil under very high pressure. As a result of the extremely high pressing pressure, the membrane behaves like a liquid and the blanks on the tool or the stamp and the sheet metal holder or the die and the sheet metal holder assume the shape of the tool with high accuracy.

The part can therefore be manufactured completely in a single pressing process.

This results in cost savings (tool and sheet metal part manufacturing costs) of 90% and more. Handiwork at the Tei Manufacturing is no longer necessary, which is important for prototypes and small series. There is no fear of material hardening.

The result is a near-series statement regarding crash and corrosion behavior (significantly less scope of changes after the crash series with failure patterns), optimal series preparation, for example in the automotive industry, through near-series prototype parts. The finished part is available faster. The dimensional accuracy is increased. The surface quality is improved; Cutting edges (cutting edges) are omitted. The effort for tool changes is low. There is no need to wash the tools. Tool wear is lower compared to the conventional method. Higher draw ratios (+ 30%) can be achieved. A difficult design is also possible. Sheet thickness reduction and sheet thickness variants are possible. All of the production stages required to produce a sheet metal part can be produced in one tool part. This saves conventional press capacity and makeready times. The formability, in particular in the case of aluminum, can be increased by placing a second steel, aluminum or another material on it, which is then removed again. A material presentation through inserts (e.g. plastic, aluminum, or steel) is possible.

• Figur 1 ein zu fertigendes Blechteil,
• Figur 1a einen Schnitt längs der Linie A-A in Figur 1,
• Figur 1b einen Schnitt längs der Linie B-B in Figur 1,
• Figur 1c das in Figur 1a im Kreis X dargestellte Detail in vergrößertem Maßstab,
• Figur 2 ein Ausführungsbeispiel eines Blechformungswerkzeuges nach der Erfindung in Explosionsdarstellung,
• Figur 3 einen Schnitt durch das in Figur 2 gezeigte Werk­zeug,
• Figur 4 eine Einzelheit zu Figur 3,
• Figuren 5 bis 9 den Arbeitsablauf beim Arbeiten mit dem neuen Blechformungswerkzeug.
• Figur 10 ein Werkzeug mit einem Blechhalterring.

The invention will be explained in more detail with reference to the exemplary embodiments shown in the figures. Show it

• 1 shows a sheet metal part to be manufactured,
• FIG. 1a shows a section along the line AA in FIG. 1,
• 1b shows a section along the line BB in FIG. 1,
• 1c shows the detail shown in FIG. 1a in circle X on an enlarged scale,
• FIG. 2 shows an exemplary embodiment of a sheet metal forming tool according to the invention in an exploded view,
• FIG. 3 shows a section through the tool shown in FIG. 2,
• FIG. 4 shows a detail of FIG. 3,
• Figures 5 to 9 the workflow when working with the new sheet metal forming tool.
• Figure 10 shows a tool with a sheet metal holder ring.

Figure 1 shows a sheet metal part to be produced, for example, here a car side wall in the front right. It requires cutting, folding, snapping, pulling, and other operations to make it, typically cutting, snapping, pulling, and pusher tools for undercuts.

The undercuts can be seen in FIGS. 1 a to 1 c, FIG. 1 a drawing a section along line AA and FIG. 1 b a section along line BB in FIG. 1 and FIG. 1 c the detail enclosed by circle X in FIG. 1 a, namely the water channel , enlarged.

According to Figure 2, the new sheet metal forming tool consists of several parts so that the finished sheet metal part can also be lifted off the punch (see the undercuts in Figures 1a and 1b). According to the invention, all the tool elements required for manufacturing the sheet metal part are integrated in the stamp and sheet metal holder (FIGS. 2 and 3). Figure 3 shows the complete universal tool shown in section. This consists of shaping tool parts 1a, 1b and 1c, which are designed here as positive tool parts. The invention is not limited to this, however, it can be also act as negative tool parts. These shaping tool parts 1a, 1b, 1c are designed in such a way that they allow demolding for undercuts. The lateral sheet metal holder 2, which can be rigid or movable, the perforating device 3 to be described below (see FIG. 4), the demoulding mechanism 4 and the cutting strips 5 for intermediate cutting, the cutting strips 6 for final cutting, cutting strips 7 for the shaped plate can be clearly seen as well as (process-dependent) lot parts 8, which are necessary in sheet metal part production in several pressing stages. 9 is an insert for presenting the material in difficult areas or for changes. One recognizes the mechanism necessary for assembly, for lifting and for operations such as the pivot guide 20, the pivotable loose part with undercut 21, centering cams 22 which are received in a corresponding bore 23, the lifting device 24 or locking device 25, the component 1c For example, for punching and putting through (closed folding) is suitable. The cutting ring 3, which is only partially shown, can be clearly seen in FIG. 3. It consists of the hole, the actual cutting ring to be used, the counterholder and the disc spring to be described.

In FIG. 3, the same parts are designated with the same reference symbols as in FIG. 2. A forming pressure p, which acts on the membrane, is indicated. Figure 3 shows essentially in the right part of the figure that a number of components (apart from the hole device 3 already mentioned) are spring-loaded, such as the cutting strips 5 for intermediate trimming and the cutting strips 6 and 7. Stamp and sheet metal holder are thus mutually movable here . In the left part of Figure 3, the corresponding parts are arranged without spring support. The stamp and sheet holder are rigid. You can also use one piece for simpler sheet metal parts be formed when a separate lifting mechanism 24 is not required due to the lack of undercuts. However, the stamp 1a, 1b, 1c is movable relative to the sheet metal holder 2. The movement can be brought about by mechanical, hydraulic, pneumatic or other means.

22/23 are guides and S is the cut trench.

FIG. 4 shows the punching device 3 of FIGS. 2 and 3 in detail. The punching process has already taken place. One recognizes (in the middle) the waste part 10a and the remaining sheet metal part 10, the piston 28, which has compressed the spring 27 when a certain presettable pressure (for example 700 bar) is exceeded.

How to work with the sheet metal forming tool or how the method according to the invention is illustrated schematically in FIGS. 5 to 9 described below.

Figure 5 shows the sheet metal forming tool 1 before the pressing process in section, with the sheet 10 placed on it (p₀ = 0 bar).

The start of the pressing process is shown in FIG. The metal sheet (blank) is cut at the points shown by arrows A. The material flows after (first intermediate trimming) (p₁> p₀). The pressure continues to build.

Figure 7 shows the situation after a further increase in pressure. In order to allow a further "flow" of the material, cutting strips 5 are attached, on which the sheet material is cut. See arrows B (second intermediate trim (p₂> p₁). The pressure is increased further.

Figure 8 shows the molded part when pressed p₃> p2). The cutting strips 6 are used for the final trimming, which enables the material to flow again. The area X is shaped as well as punching, folding, undercutting and putting through. If necessary, certain tool elements are spring loaded. The hole through the punching device 3 is only cut when the sheet metal has been formed. The stroke movement C takes place, for example, mechanically, hydraulically or pneumatically.

Figure 9 shows the finished molded part (p = 0 bar).

The stamp elements 1a, 1b, 1c are raised, the finished part 10˝ (side wall of a car, for example) is removed just like the waste pieces.

The demolding process takes place as follows: The sheet metal part 10˝ is pushed to the left. The sheet metal part is then pushed forward and finally the sheet metal part is removed upwards. If required, any number of tool elements can be flexibly designed according to the spring base 3 described above.

The part can also be pressed in stages (in one or more tool parts, with or without loose parts). The intermediate cuts can be made in the press or conventionally (for example by hand, using a laser, cutting tools, etc.).

Which of the methods is used depends on the number of pieces required (economic efficiency assessment).

FIG. 10 shows a special design of the tool, which is intended in particular for the production of flat components with a low degree of deformation. With such parts there is a risk that the sheet in its central region very quickly comes to rest against the punch and is held here in such a way that sufficient stretching of the component in the central region is not achieved, with the result that this region has lower strength properties. In order to enable a defined extension of such components, the sheet metal holder ring 2 in the tool according to FIG. 10 is designed so high that it extends a sufficiently large distance above the highest point of the punch 1a. At the same time, a sheet metal holder ring 31 is provided, while the cutting strips 7 shown in FIG. 3 are omitted for the initial trimming. During the pressing process, the edge of the sheet metal is firmly held between the sheet metal holder and the sheet metal holder ring, so that a sufficient extension of the central area of the sheet metal is ensured before it contacts the upper areas of the punch. In order to make it easier to hold the sheet in place, the sheet metal holder is provided with one or more projections, for example beads (32), on its supporting surface, the corresponding depressions (33) in the sheet metal holder ring are adapted and project into this. Only when the pressure builds up further after the sheet has been sufficiently stretched in the middle region does an end or intermediate trimming take place in the drawing trench 34 shortly before the point at which the component threatens to tear. The tool shown in FIG. 10 can, moreover, be designed similarly to the tool in FIG. 3, that is to say with further tool parts.

Claims (15)

1. A method for producing complicated sheet metal parts in one, two or more operations / operations, wherein at least one operation comprises several processing steps, characterized in that a) the sheet metal board is first placed, b) the pressure is continuously increased up to, for example, 800 bar while passing through various pressure phases, the material flowing into the recesses of the mold in the first phase and the mold blank being cut at lower points of the mold in the subsequent phase, the Material continues to flow into the recess, corners and undercuts and that the pressure is increased to the final phase, the workpiece is finally embossed, trimmed, punched, put through and / or folded and c) the sheet metal part is demolded after pressure reduction. 2. The method according to claim 1, characterized in that during the first phase the edge trimming takes place to the form plate. 3. The method according to claim 1, characterized in that during the first phase the sheet metal plate is held at the edge by a sheet metal holding ring in such a way that sufficient stretching of the sheet metal plate is ensured in its central region. 4. The method according to any one of the preceding claims, characterized in that against one for Forming the telegeometry is punched sufficient pressure. 5. Tool for the pressure forming of sheet metal parts for carrying out the method according to one of the preceding claims with a forming tool part enabling a deep-drawing process, characterized by applying pressure by active media, such as fluid-pressurized rubber or PU membranes or rubber pads, or applying pressure exclusively by active energies, such as explosion forming or Sound waves, in their respective functions as counter tools. 6. Tool according to claim 5, characterized by a shaping tool consisting of the following parts: a) during a first drawing phase, the sheet metal plate (10) trimming (7) or holding it to the edge (31) tool parts, b) in the event of an increase in pressure in a second intermediate stage, the preformed sheet metal plate, which allows the additional cutting tool parts (5) to flow in further, c) in the case of a further increase in pressure, the tool parts, which allow full shaping of the workpiece, with a resilient counter-holder. 7. Tool according to any one of claims 5 or 6, characterized by cutting bars (7, 6, 5) and perforated units (3) which allow the material to flow. 8. Tool according to claim 7, characterized in that the cutting strips are arranged in the drawing trench (S) for intermediate trimming in the case of block deformation or cavity deformation. 9. Tool according to claim 7, characterized in that the tool elements are spring-loaded with an adjustable series resistor against a final resistor for intermediate trimming in the case of cavity deformation of the cut trench or the sheet metal holder or in the case of split tool. 10. Tool according to claim 9, characterized in that the adjustable series resistor is formed by a punch penetrating a cutting ring (Figure 4) which is supported via a plate spring (27) against a series resistor. 11. Tool according to one of claims 5 to 10, characterized in that work is carried out for larger holes with a rigid cutting ring and rigid insert. 12. Tool according to one of claims 5 to 11, characterized in that the tool part carrying the undercuts is designed as a separately operable loose part. 13. Tool according to claim 12, characterized in that when working in several operations in the tool rigid or spring-loaded loose parts (8) can be inserted such that a reflow of the material or pressing with a uniform pressure is possible. 14. Tool according to one of claims 5 to 13, characterized in that the bearing surface of the sheet metal holder (2) is significantly higher than the highest Point of the stamp (1a) and a sheet metal holder ring (31) is provided, which holds the sheet with its edge on the sheet holder during the first pressing phase. 15. Tool according to claim 14, characterized in that the sheet metal holder is provided on its support surface with one or more projections (32), the corresponding recesses (33) in the sheet metal holder ring are adapted.

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