EP0381089B1 - Hydraulic press - Google Patents

Description

The invention relates to a hydraulic press according to the preamble of the main claim and a method for pressing and compacting pressed parts made of fine-grained materials.

Hydraulic presses are known in which pressing parts consisting of fine-grained materials are pressed between an upper and a lower pressure piece. The workpieces resulting from the resulting shaping are sintered in a subsequent process, agglomerates being formed as a result of surface melting and caking or as a result of the fusion processes. The conventional manufacturing methods for shaping powder compaction are "ejecting", "pulling off" and "counter-pressing".

A press for producing powder compacts is known from DE-OS 31 42 126. This includes an adapter system that has a fixed base position to a basic press fixed table. A press train with a fixed reference, however, only allows one of the named powder-pressing process methods, whereby the press mentioned is the process method of stripping.

From GB-A-2 025 834 a hydraulic press according to the preamble of the present claim is known. This known hydraulic press requires an extensive, large-scale multi-plate adapter, which can only work according to a fixed method to manufacture a powder-pressed part. The production process is pressure-controlled on fixed adapter stops. The press has two pressure-controlled press axes. There is only one upper and one lower plunger, and the punches within the adapter are actuated by means of the adapter plunger. The press with multi-plate adapter is therefore only designed for the "pull-off process". "Compound presses" are not possible with this press.

When "ejecting" as the oldest pressing method, the upper punch, which acts on the pressed part from above, is moved downward, while the die comprising the pressed part and the lower punch, on which the pressed part rests, are in a stationary position. When the pressing piece is exposed, the upper punch and the lower punch are then moved upwards, while the die is still in a resting position. This exposes the powder-compacted pressed part.

When "pulling off" as the most commonly used pressing method, both the upper punch and the die comprising the pressed part are moved downward during the compression process. The lower stamp remains in a resting position. When the press part is exposed, the upper punch moves upwards, while the lower punch remains in a fixed position. The compacted pressed part is then exposed by a further downward movement of the die.

With the pressing method of "counterpressing", the upper punch moves downward during the compression process, while the lower punch moves upward. The die surrounding the powder material to be compacted remains in a resting position. The die also remains in this resting position during the process of exposing the press piece, while the upper punch and the lower punch move upward and the press piece is thus guided out of the die through the lower punch.

The pressing method described in the first place proves to be inflexible since it is only suitable for pressing single-stage parts. The unfavorable density profile that occurs with this also leads to increased crack formation, which can occur in the form of slate cracks or exposure cracks.

The pressing method described in the second place is characterized by high maintenance costs and high demands on the operation. The press system is often unstable, which causes the risk of slate.

In the pressing method of counterpressure, cracking is possible when the pressed parts are exposed due to the movement sequences that occur.

The powder pressing methods used to date are strictly process-related and are directly dependent on the press and the tools used in it, an adapter also being required. The possibility of combining the three pressing methods could not be realized so far, since each of the three pressing methods listed required their special tool and apparatus structure as well as a method-related press design.

The invention is therefore based on the object of creating a hydraulic press for compacting fine-grained substances which enables the combination of the motion sequences of the three different pressing methods both as a single step and as an overarching production sequence.

This object is achieved by the features specified in the main claim and by the method characterized in claim 6.

By equipping the hydraulic press with a plurality of plungers which can move independently of one another and at different speeds relative to one another, a combination of the movement sequences of the three different pressing methods becomes both as a single step, as well as a comprehensive manufacturing process. The pressure pistons, which are controlled and pressure-monitored by means of a computer-aided numerical path control, have a very favorable tool design. In particular, the shapes of the pressed parts to be pressed can be varied as desired without requiring multiple pressing processes or having to replace the tools used. Since the press punches are characterized by a short tool structure, they have high tool stability, which also increases the stability of the overall system.

In the multi-axis hydraulic press with path control according to the invention, there is also no need for an adapter with extended pressing functions or a mechanical reference base fixed by a fixed basic table. By eliminating the need for a tool and adapter structure specially adapted to the previously known pressing methods, the advantages of the respective pressing methods can be included in the new pressing method of "composite pressing". With this new pressing method, slate or crack formation occurring on the pressed part in particular can be excluded.

• Figur 1 den Aufbau einer erfindungsgemäßen Presse mit einer Teilansicht des Gehäuses,
• Figur 2 den inneren Aufbau der durch Figur 1 dargestellten Presse in einer Gesamtansicht,
• Figur 3 einen vergrößerten Ausschnitt aus der durch Figur 2 dargestellten Presse,
• Figur 4 eine schematische Darstellung des Verfahrensablaufs beim "Verbundpressen",
• Figur 5 den Ausschnitt eines durch die Verpressung verdichteten Preßteils in räumlicher Darstellung,
• Figur 6 eine Pressenansicht ohne Werkzeuge und
• Figur 7 eine erfindungsgemäße Presse im Querschnitt entlang der aus Figur 6 ersichtlichen Schnittlinie A-B.

The invention is explained below with reference to the drawing. Show it:

• FIG. 1 shows the structure of a press according to the invention with a partial view of the housing,
• FIG. 2 shows an overall view of the internal structure of the press represented by FIG. 1,
• Figure 3 shows an enlarged detail from the figure 2 shown press,
• FIG. 4 shows a schematic representation of the course of the method in "composite pressing",
• FIG. 5 shows a detail of a section of a pressed part compressed by the pressing,
• Figure 6 is a press view without tools and
• 7 shows a press according to the invention in cross section along the section line AB shown in FIG. 6.

From Figure 1, the plunger 1 to 5 can be seen, between which a press part 6 consisting of fine-grained materials is pressed and compressed. During the pressing process, the plungers 1 and 2 act as a cooperating composite plunger from above and the plungers 3 and 4 as a composite plunger from below on the press part 6. The plunger 5 act as a synchronizing plunger on the die table 8 shown in FIG. 2. An adapter 7 for the purpose of a tool assembly with coupling and handling function, as well as the tools of the plunger 1 to 5 can be inserted into the press as a complete package. In view of the further pressing movements, however, further pressing functions from the adapter are not necessary.

FIG. 2 shows the die table 8 and the die holder 9 with the die 10 located thereon. The die holder 9 can be inserted into the press with the complete tooling. The coupling connection between the plungers 1 to 5 can be made as a straight coupling or via a bayonet system by means of a 90 ° rotation. The position assignment and transport securing is done via an auxiliary bracket, which is removed after the coupling. The through the plunger 3 and 4 guided lower punches 11 to 13 are unclamped and are positioned or guided over the die 10. The upper punches 14 and 15 are clamped or oriented using a special guide. A core punch 16 held by a friction lock is brought into position after coupling from below via an auxiliary axis 17 or subsequently placed and fastened via a screw connection. The plungers 1 to 5 work within the press as a free-floating tool system that is clamped and moved by the oil columns of the five plungers 1 to 5.

By dividing the matrix table 8 into an upper and a lower half, with connection to 2 plungers for each table half, a divided matrix can be used. By inserting a split die, undercuts can be made on the pressed part.

The enlarged section of FIG. 3 shows the pressing tools 11 to 15 and the pressing part 6 pressed between them.

The movement sequence of the press rams shown in FIG. 4 during the composite pressing shows the stage of filling the metal powder under position I, the pressing process itself under position II and the exposure of the pressed part under position III. During the pressing process, in which the filled metal powder is compacted, the upper punch 1a moves downward in the direction of the arrow, while the die 2a remains in a stationary state. The lower punch 3a moves upwards from the position I given during the filling process, as can be seen in position II. After pressing, both the upper punch 1a and the lower punch 3a remain in a resting position while the die 2a, as can be seen from position III, is moved downward in the direction of the arrow. The Press part 6 is exposed during this process.

For a corresponding need, the die 2a can also be moved in both directions during the counter-pressing. This circumstance can be used to deliberately under- or overpressure.

FIG. 5 shows a possible form of a compacted pressed part. Such molded parts can be compressed by a pressing process without the use of an adapter or several pressing processes. The different shapes of the pressed parts are made possible by the differently positioned press dies, which can be moved at different speeds, with the individual press dies being controlled by a computer-assisted numerical path control and additionally being monitored for pressure.

From Figure 6 displacement sensors 61 to 65 can be seen, which work as displacement measuring systems. The path control takes place via a computer-aided numerical path control for machine tools. Displacement sensor 61 measures the relative movement of plunger 1 to the press stand (press housing) P, while displacement sensor 62 measures the relative movement of plunger 1 to plunger 2. Displacement sensor 63 measures the relative movement of plunger 3 to press stand P in the lower region of the press according to the invention, while displacement sensor 64 measures the relative movement between plunger 3 and 4. Displacement sensor 65 decreases the relative movement between press stand P and die table 8.

In the plan view of Figure 7, the plunger 5 are shown, which act on the die table 8. Since this press view is also shown without tools, the plungers are also from the drawing 3 and 4 can be seen in a plan view.

Claims (6)

1. Hydraulic press having a press housing and pressing pistons (1-5) which are movable therein towards each other from the top and from the bottom, and having, arranged in the central region of the press, a mould (10) which can be withdrawn from the compact, for compressing and shaping pressed parts consisting of finely particulate materials, especially metal powders, characterised in that the press has a plurality of upper and a plurality of lower pressing pistons (1-5), one pressing piston (5) forming a central table piston system consists of a plurality of synchronized plungers which act from above and from below on a mould table (8) having a mould (10) arranged thereon, the pressing pistons are path-controlled and pressure-monitored by means of a computer-aided numerical continuous-path control system for machine tools, and pressing pistons (1-4) cooperating from above and below in a combination are movable with one another or independently of one another and act on a plurality of upper and lower rams (11-15) that serve as pressing tools and that can be moved independently of one another and relative to one another and to the mould at different speeds.
2. Hydraulic press according to claim 1, characterised in that the pressing rams (11 to 15) have a short tool construction and are mounted offset in their tool holder.
3. Hydraulic press according to claim 1 or 2, characterised in that the press is equipped with up to five pressing pistons (1 to 5), wherein four pressing pistons (1 to 4) act on the pressing rams (11 to 15) and one pressing piston (5), consisting of four or two synchronized plungers, acts on the movable mould (10).
4. Hydraulic press according to any one of the preceding claims, chracterised in that it operates by means of path-measuring sensors without a fixed mechanical reference base.
5. Hydraulic press according to any one of the preceding claims, characterised in that the pressing rams (11 to 15) are inserted into the press by means of an intermediate mould part (9) and together with the mould (10) which is dependent upon the shape of the pressed parts (6).
6. Process for the compaction of pressed parts consisting of finely particulate materials by means of a hydraulic press, characterised in that the pressed part (6) is compacted by combination pressing, in which an upper and a lower pressing ram are moved towards each other in combination and, during the pressing operation, a mould surrounds the pressed part (6) and the pressed part (6) is exposed after completion of the pressing operation by guiding the mould downward while the upper and lower rams remain stationary.

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