WO2013144036A1 - Hydraulic intermittently operated press - Google Patents

Description

 Hydraulic cycle press Description:

The invention relates to a hydraulic cycle press for the production of molded plastic parts, in particular fiber composite plastic, in a tool consisting of upper tool and lower tool press tool, with - a press frame with upper beam, lower beam and side panels, an upper tool carrier and a plurality of attached to the upper beam pressing cylinders whose pistons are working on the upper tool carrier, wherein the lower tool is arranged on the lower beam / and the upper tool is attached to the upper tool carrier or fastened. Plastic means z. As thermosetting plastics, that is in particular resins, z. As epoxy resins, polyester resins or polyurethane resins which are initially liquid, viscous or powdery and harden under the action of a hardener and / or pressure and / or heat. Basically, the invention also includes the production of molded parts made of thermoplastic materials, the z. B. heated (as a melt) are introduced into the mold and then cure by cooling. Plastic in the context of the invention particularly preferably means a fiber-reinforced plastic and consequently a fiber composite material in which fibers are embedded or embedded in a matrix of plastic. The fibers may preferably be glass fibers and / or carbon fibers or carbon fibers, but also ceramic fibers, metal fibers and / or natural fibers and corresponding combinations

act. The fibers may be loose, but preferably in the form of semi-finished products, for. B. as fiber mats or the like. Moldings means z. B. molded parts for the automotive industry, for. As body parts, or moldings for aerospace engineering, z. B. fuselage, wing parts or the like for aircraft construction. Furthermore, it may be components for mechanical engineering, z. B. components for power plant construction, plant construction and in particular wind turbines or the like.

The invention preferably relates to a hydraulic cycle press for the production of molded parts made of fiber composite materials by means of transfer molding, which is also referred to as RTM process (Resin Transfer Molding). In this known method, first the fibers (eg a semifinished fiber product) are placed in a mold, which as a rule consists of upper tool and lower tool. After closing the mold, the molding compound (eg a two-component molding compound comprising a resin and a hardener) is injected into the molding space so that the molding compound encloses the fibers as a matrix and hardens to form the molding. Before and / or during the injection of the molding compound, the mold can be subjected to negative pressure or vacuum. Since the molding material usually not only by the hardener or z. As heat, but in particular cures under pressure, it is necessary to clamp the tool halves against each other. For this purpose, the tool halves are mounted in a press, so that the molding compounds is injected after inserting the fibers and after closing in the closed mold.

Such presses operate in clock mode. In practice, it is customary to use plunger cylinders as press cylinders and additionally more or less complex closing devices and possibly retraction devices,

z. B. Retract cylinder provide. The structure of the known from practice hydraulic presses for the production of molded parts made of fiber composite material is relatively expensive. This is also related to the fact that very high pressing forces must be applied. In order to be able to work with pressing cylinders with relatively small volumes of hydraulic fluid and still be able to use press tools of different dimensions, separate opening devices have been proposed so that only small paths can be covered with the pressing cylinders. The known concepts have in common that the tool carrier is usually moved with long-stroke cylinders and clamped or locked against the press frame. For applying the pressing force or closing force and for accurate control separate Kurzhubzylinder are provided. To describe z. B. DE 36 37 544 A1 and DE 36 37 545 A1 discloses a hydraulic Schnellhubpresse in window frame construction for the production of fiber-reinforced plastic Fornnteilen, with a the upper mold half carrying Pressbär, with a hydraulic high-speed device for the idle stroke and a hydraulic Kurzhubeinrichtung for the working stroke can be raised and lowered. Differenziaizylinder be used for the working stroke. The Pressbär, however, in the idle stroke of a centrally acting in the crosshead, hydraulic high-speed traction drive can be raised and lowered and slidably guided by push rods in the crosshead. From DE 35 23 164 C1, a hydraulic press for the production of molded parts made of fiber-reinforced plastic is known, which also has a Schließhubantrieb and a Presshubantrieb. The Schließhubantrieb is equipped with at least one Schließhubzylinderkolbenanordnung

tet, which operates between the upper (movable) press bar and press truss, wherein the arranged on the upper (movable) press beam Presshubantrieb comprises a plurality of Presshubzylinderkolbenanordnungen with hollow piston and surrounding cylinders.

DE 20 2010 007 238 U1 alternatively describes a press in the embodiment as a direct drive servo screw press, the press comprising a machine frame comprising at least one press table, a head piece with at least one drive assembly and at least one side stand with slide guides. At least one linear absolute displacement measuring system is assigned to the control circuit of the drives, in which each drive is acted on either by the signals of a permanently assigned measuring system or in which signals defined and computationally processed are assigned to each drive. This should be done an active and dynamic compensation of the constantly fluctuating distance error between the lower edge of the plunger and the surface of the press table.

Overall, the known presses have basically proven in practice. However, the structure is relatively expensive. However, the structure is relatively expensive.

Moreover, DE 10 2010 017 912 A1 discloses a hydraulic press drive for a forming or forging press with a cylinder and a plunger movably mounted in the cylinder, wherein the plunger divides the cylinder into a compression pressure space and a return stroke space. In this case, a control unit is provided, which controls the pressure generating means as a function of the respective stroke position of the plunger and / or of the respective pressure prevailing in the compression pressure space and / or return stroke space

regulates. The control is set up in such a way that, when the pressure generating means are actuated to generate a pressing stroke, the pressure generating means for generating a counterpressure in the return stroke chamber are controlled in such a way that the force resulting from the pressing pressure is greater than the force resulting from the counterpressure , so that hydraulic fluid is compressed from the Rückhubraum urged.

A similar hydrostatic drive system is known in connection with injection molding machines from DE 198 42 534 A1.

DE 195 24 042 A1 describes a drive for hydraulic presses with a high number of strokes, in particular for forming and / or cutting of sheets, plastics or the like. A circuit arrangement for controlling the fast feed and return of press dies, in particular on high-pressure hydraulic presses, is also known from DE 274 385 A1.

Finally, DE 10 2004 046 493 A1 proposes a press for the production of plastic moldings in which both the idle stroke and the drive for the press ram are effected by means of a toggle lever system comprising a controlled drive.

The invention has for its object to provide a hydraulic cycle press, which enables a simple construction of an economical production of molded plastic parts, in particular fiber composite material.

To solve this problem, the invention teaches in a generic hydraulic timing press for the production of plastic moldings, in particular fiber composite plastic, that the pressing cylinders are designed as double-acting differential cylinders whose pistons are connected by train / pressure connections directly to the upper tool carrier and are arranged both for opening and closing and for applying the pressing force.

The invention is based on the recognition that the structure and operation of a hydraulic cycle press can be considerably simplified if the plunger cylinder known in principle are replaced by double-acting differential cylinder and also dispenses with additional impression cylinder, retraction cylinder, quick lift drives or the like. Rather, the cycle press according to the invention has exclusively the double-acting press cylinder, so is dispensed with additional linear actuators. This can be based on a positioning of the pressing cylinder itself, z. B. by separate spindle drives or the like can be omitted. Even complex locking devices are not required. Both the opening and closing of the press and the application of the pressing force is realized solely on the press cylinder, which are connected in the sense of a train / pressure connection with the upper tool carrier, so that an exact positioning of the upper tool and / or an exact adjustment of the pressing force without additional cylinders can be realized. In the case of two press cylinders, the press thus operates with only two axes, without the need for additional axes for further linear drives. Preferably, however, four press cylinders, six press cylinders or even more press cylinders are provided between the upper beam and the upper tool carrier, so that work is then carried out with four axes or six axes. The use of modern

Press cylinder with suitable valves and a suitable control and / or regulating device not only allows the production of high pressing forces with high accuracy, but in particular an exact positioning of the upper tool relative to the lower tool. According to the invention, the pistons of the pressing cylinders can be positioned with a path accuracy of 0.05 mm, preferably with a path accuracy of 0.02 mm. This means within the scope of the invention that deviations of the actual position of the piston and thus also of the upper tool from a desired value amount to a maximum of 0.05 mm, preferably a maximum of 0.02 mm. This is advantageous in the production of fiber composites, especially in the so-called "open-die mode", in which upper tool and lower tool are not directly adjacent to each other, but with the interposition of the introduced in the mold cavity molding compound by a (small) gap spaced from each other, wherein such a gap in the order of z. B. can be 0.1 to 1 mm. In principle, however, the invention also includes presses for production in the "closed-die mode", in which upper tool and lower tool abut each other directly.

Advantageous developments of the invention are explained below:

It has already been pointed out that the pressing cylinders are connected as double-acting differential cylinders by means of tension / pressure connections directly to the upper tool carrier. It is expedient if the pistons of the pressing cylinder are pivotally connected to the upper tool carrier. Preferably, then, a connection can be realized with the interposition of pressure and tension resilient, spherical plain bearings. This technology is known z. B. in continuous presses for the production of wood-based panels, in which the pistons of the press

Cylinder are pivotally connected to a press plate (see, for example, DE 10 2005 009 298 A1). In the same way it is expedient to connect the cylinder pivotally connected to the upper beam. Furthermore, it is expedient if the upper tool carrier is guided in the vertical direction laterally on the side parts of the press frame, so that a proper positioning of the upper tool relative to the lower tool, taking into account the small gap widths in the dipping edges is possible. Such leadership is z. B. then makes sense if the cylinders are "hinged" on both sides.

With the press according to the invention can in particular moldings made of fiber composite plastics, for. B. for the automotive industry and / or aerospace engineering. The existing of upper tool and lower tool press tool generally has a large mass of more than 10 t, z. B. also more than 25 t.

The press according to the invention is usually equipped or connected to a control and / or regulating device. Consequently, the pressing cylinder or its control valves are connected to the control and regulating device, preferably for a pressure control and / or path control. Such a press can thus be regulated and / or operated pressure-controlled.

The control and / or regulating device of the press can be set up in such a way that during the pressing, the pressures in the individual cylinder chambers or the resulting pressing forces of all the pressing cylinders are ascertainable and can be supplied to the control / regulating device. With the control / regulating device, from the determined pressures / forces, taking into account

tion of stored in the control / regulating device structural data of the press continuously deformations of the press frame can be determined. In this case, taking into account the determined deformations of the press frame, the pressing cylinders can be acted upon in such a way that the determined deformations can be compensated in this way and consequently compensated. The deformations of the press frame are continuously iteratively ascertainable during the increase of the pressing pressure and / or during the pressing and can be compensated taking into account finite element calculations carried out on-line. The compensation of deformations of the press frame can take place taking into account temperature values which are recorded at several points of the press frame (eg with temperature sensors).

Overall, mold parts can be produced quickly in a particularly economical manner with the hydraulic cycle press according to the invention with a simple structure. Modern double-acting differential cylinders allow, despite relatively large volumes of oil, a quick and accurate closing and opening and also the application of even the highest pressing forces. Of particular importance in the context of the invention, therefore, the use of double-acting Differenziaizylindern as a press cylinder in a hydraulic cycle press for the production of moldings made of plastic, in particular fiber composite plastic. Of particular importance is the use of these press cylinders for a RTM press.

The invention also relates to a process for the production of molded plastic, in particular fiber composite plastic, with a press of the type described. According to the invention during the

Pressing continuously determined the pressures in the individual cylinder chambers or the resulting pressing forces of all press cylinders and fed to a control / regulating device. This control / regulating device determined from the determined pressures / forces taking into account stored in the control / regulating structure data of the press continuously deformations of the press frame. In this way, the pressing cylinders are then subjected to such determined deformations of the press frame in such a way that the determined deformations (when setting the desired values) are compensated. According to the invention, therefore, a computational compensation of the deformations of the entire frame structure takes place. The deformations of the press frame or of the frame structure are determined continuously during the pressing or during the increase of the pressing pressure iteratively and compensated for taking into account online calculations (eg, according to the finite element method). This can be done in principle compensation for deformations of the entire frame structure waiving separate position or displacement measuring in the field of press tool. The control / regulating device is designed as a powerful data processing system in which comprehensive information about the frame structure is stored. By means of the chamber pressures in the cylinders, it is possible, during the pressure build-up or during the pressing, taking into account the stored data, to draw conclusions about structural deformations which can then be correspondingly compensated. This is achieved in particular by online finite element calculations performed online. In this way, the required accuracy in the field of press tool for complex RTM processes can be achieved, so that can produce economically manufactured moldings of the highest quality. Alternatively or additionally, it may be expedient, the compensation also under

To take into account temperature values that are recorded at several points of the press frame. In this way, not only (via the press cylinder) mechanical deformations can be determined, but in particular also deformations caused by temperature, which must be taken in practice for various reasons in purchasing.

In the following the invention will be explained in more detail with reference to a drawing showing only one exemplary embodiment.

The sole figure shows a hydraulic cycle press (as RTM press) in a highly simplified representation.

It is a hydraulic cycle press (eg RTM press) for the production of plastic moldings, in particular fiber composite plastic. In such a cycle press a press tool is mounted, which is composed of upper tool 1 a and lower tool 1 b. Such a mold can, for. B. fed with a semi-finished fiber and then closed. After loading, the mold cavity can be filled with the molding compound, eg. As resin and hardener to be filled. The molding compound cures using pressure and possibly heat in the press.

The press has a press frame 2 with upper beam 3 and lower beam 4 and side parts 5. It can be z. For example, a frame-type press is used which is composed of a plurality of (closed) press frames arranged one behind the other. Alternatively, however, is also a press in column design into consideration, so that the side panels are then formed by press columns or the like. The press has an in

vertical direction movable upper tool carrier 7 on which the upper tool 1 a is attached. The lower tool 1 b rests usually stationary on the lower beam 4 or arranged on the lower beam 4 press table 4 '. On the upper beam 3 of the press frame 2, a plurality of pressing cylinders 8 are fixed, the piston 9 to work on the upper tool carrier 7.

These press cylinders 8 are designed as double-acting differential cylinders, the pistons 9 are connected by train / pressure connections directly to the upper tool carrier 7, so that not only the pressing force is applied with these Differenzialzyl by 8, but also the opening and closing of the press , The stroke of the pressing cylinder 8 is sufficiently large, so that a tool change and adaptation to different tool geometries and in particular tool heights is possible. Additional linear drives for positioning the tool carrier are therefore dispensed with. The known combinations of z. B. long-stroke cylinders and Kurzhubzylindern be replaced by the differential cylinder according to the invention. In the front view of the press only two juxtaposed pressing cylinder 8 can be seen. However, it is expedient to provide several such rows of cylinders one behind the other, so that z. B. can be worked with a total of four press cylinders or six press cylinders. On additional linear actuators and in particular lock cylinder or the like is omitted.

The upper tool carrier 7 can be guided laterally on the side parts 5 of the press frame 2 in the vertical direction. This is not shown in the figure.

provides. In order to enable an exact and variable positioning of the upper tool relative to the lower tool, the pistons 9 of the pressing cylinder 8 are pivotally connected to the upper tool carrier 7. In the exemplary embodiment, a connection is indicated with the interposition of loadable on pressure and train spherical spherical bearings 10. The cylinders 8 are pivotally connected to the press frame, namely hinged to the upper beam 3, also with the interposition of spherical spherical plain bearings 6. Furthermore, it is indicated that the pressing cylinder 8 are equipped in a known manner with control valves 1 1, via which the two volumes of double-acting differential cylinder are acted upon. The pressure cylinder 8 and its control valves 1 1 are connected to at least one (not shown) control or regulating device with which an exact control / regulation of the pressing pressure and / or the path and consequently the position is possible. The pistons 9 of the pressing cylinder 8 can be positioned with a path accuracy of 0.05 mm or optionally also 0.02 mm, so that a total of a simple construction with a very precise control.

In particular, deformations of the frame structure can be compensated by suitable press control.

Claims

claims: 1 . Hydraulic cycle press for the production of molded plastic, in particular fiber composite plastic, in a from upper tool (1 a) and lower tool (1 b) existing press tool, with - a press frame (2) with upper spar (3), lower beam (4) and Side parts (5), an upper tool carrier (7) and - a plurality of the upper beam (3) fixed pressing cylinders (8) whose pistons (9) on the upper tool carrier (7) work, wherein the lower tool (1 b) on the lower spar (4) is arranged and the upper tool (1 a) on the upper tool carrier (7) is fastened or fastened, characterized in that the pressing cylinder (8) are designed as double-acting Differenziaizylinder whose piston (9) by means of train / pressure Connections are directly connected to the upper tool carrier (7) and are set up both for opening and closing and for applying the pressing force. 2. Press according to claim 1, characterized in that between the upper spar (3) and upper tool carrier (7) four or more pressing cylinder (8) are arranged. 3. Press according to claim 1 or 2, characterized in that the pressing cylinder (8) pivotally attached to the upper spar (3) and / or the piston (9) of the pressing cylinder (8) pivotally attached to the upper tool carrier (7). are closed, z. B. with the interposition of pressure and tensile load, spherical spherical bearings (6, 10). 4. Press according to one of claims 1 to 3, characterized in that the upper tool carrier (7) in the vertical direction laterally on the side parts (5) of the press frame (2) is guided. 5. Press according to one of claims 1 to 4, characterized in that the press tool (1 a, 1 b) has a mass of more than 10 1. 6. Press according to one of claims 1 to 5, characterized in that the pressing cylinder (8) or the control valves (1 1) with a control and / or regulating device for a pressure control or regulation and / or a path control or regulation equipped or connected. 7. Press according to one of claims 1 to 6, characterized in that the pistons (9) of the pressing cylinder (8) with or with a control and / or regulating device with a path accuracy of 0.05 mm, preferably 0.02 mm are positionable. 8. Press according to one of claims 1 to 7, characterized by a control / regulating device which is set up such that during the pressing continuously the pressures in the individual cylinder chambers or the resulting pressing forces of all pressing cylinders determined and the tax / Can be fed to the control device that with the control / regulating device from the determined pressures / forces taking into account stored in the control / regulating device structure deformations of the press frame can be determined continuously and that the pressing cylinders can be acted on in such a way that the deformations determined can be compensated, taking into account the deformations of the press frame determined. 9. Use of double-acting differential cylinders as a press cylinder of a hydraulic cycle press for the production of moldings made of plastic, in particular fiber composite plastic, according to one of claims 1 to 8, in particular a hydraulic RTM press. 10. A method for producing molded parts made of plastic, in particular fiber composite plastic, with a press according to one of claims 1 to 9, characterized in that during the pressing continuously determines the pressures in the individual cylinder chambers or the resulting pressing forces of all press cylinders and supplied to a control / regulating device, that the control / control device continuously determined from the determined pressures / forces, taking into account stored in the control / structure structure data of the press deformations of the press frame and that the pressing cylinders are acted upon taking into account the determined deformations of the press frame so in that the determined deformations are compensated. 1 1. A method according to claim 10, characterized in that the deformations of the press frame during the increase of the pressing pressure and / or during the pressing continuously iteratively determined and compensated taking into account finite element calculations performed online. 12. The method according to claim 10 or 1 1, characterized in that the compensation of deformations of the press frame takes into account taking into account temperature values which are recorded at several points of the press frame.