EP2460605B1 - Method for producing a series of cast components and device for producing a cast component - Google Patents

Description

The invention relates to a method for producing a series of cast components according to the preamble of claim 1 and to an apparatus for producing a cast component according to the preamble of claim 7.

In light metal casting, especially in the processing of aluminum alloys or magnesium alloys, it is very important for the quality of the cast products that the mold filling is controlled and reproducible. This requirement is particularly important when casting with a semi-liquid or semi-solid molten metal, semi-solid or semi-solid cast pulp, in a semi-solid casting process, in particular with a liquid-cooled metal melt having a solid content, since the properties of the semi-liquid molten metal, the Casting pulp strongly depend on a variety of parameters, especially temperature.

Due to the often complicated geometry or topology of the products and thus the cavity of the mold to be filled a plurality of gate points is often used, so that the cavity with sufficiently high speed with minimization of casting defects, preferably without casting defects such as voids or the like, with the Light metal melt can be filled. For example, in the document DE 10 2008 052 062 A1 describes the casting of a frame-like structural component with an opening, as required, for example, in a specifically designed design for backrests of vehicle seats. So that the products obtained need only be slightly reworked and have changed, especially increased mechanical characteristics in defined areas, the molten metal is supplied to at least two heated melt feeds and passes from there into the mold, wherein the mold has a channel in which melt streams opposite to each other or to flow towards each other.

In the context of casting with a semi-solid Gießbrei it can lead to different formation of cold metal plug when using multiple melt supply lines or hot channels at uneven temperature at the outlet of the molten metal and / or different geometric outflows (for example, different closures of the openings), such as a valve lock act and the warm molten metal of part of the cold mold. In such a case, with different sized cold plugs, the molten metal takes the path of least resistance and fills the channel through the one opened melt supply until enough back pressure is built up so that the other melt supply opens. In this way, filling fronts of the molten metal can arise, which spread at different rates when entering the cavity and meet at different times, so that the position of the contact surfaces, also referred to as binding seams, varies. Since the contact surfaces have different physical and / or chemical properties than a material section in the interior of the cast component, this variation also means a scattering of the component properties. These process variations are unacceptable for sufficiently high quality.

From the document DE 44 44 092 A1 is known for conventional plastic die casting or conventional aluminum die casting by means of a hot runner in an injection mold that the actual temperature measured during a casting cycle and depending on a deviation from a target temperature, a cooling and / or heating medium for controlling the temperature of the injection mold be supplied.

The EP 0 982 089 A1 describes a method for process monitoring in die casting or thixoforming of metals. Here, liquid metal is injected via a sprue in a mold cavity in a die casting, which consists of a fixed and a movable mold half. At points of the mold surface, where the thermal equilibrium and the solidification are easy to detect, sensors are arranged for temperature measurement. The measured characteristic values are compared as actual values with corresponding nominal values. If the actual values deviate from the setpoints excessively, either an alarm is triggered (if the deviation moves within a tolerance range) or the die casting process is aborted (if the tolerance range is exceeded). The acquisition of the measured data takes place in real time. The data is controlled, displayed and archived. This monitoring system maintains a consistently high quality standard.

The object of the present invention is, when casting a molten metal, in particular a semi-molten casting pulp, to control the time course of the melt flow starting from a plurality of sprue points into the casting mold in such a way that the position of at least one contact surface of filling fronts entering the casting mold is reproducibly in one Series of casting operations can be controlled.

This object is achieved by a method for producing a series of cast components with the features of claim 1. Advantageous developments of the invention are characterized in the dependent claims.

In the method according to the invention for producing a series of cast components, at least the following steps are carried out: A casting mold having a cavity and a plurality of sprue points, in particular hot runner exit points or nozzles, is provided. A light metal melt is introduced into the casting mold for producing a first cast component by at least two sprue points, in particular hot runner exit points or nozzles, each having a temperature and a pressure. The light metal melt flows along at least two paths in at least two streams (one stream per path), in particular oppositely flowing streams, each with a front into the mold, wherein at least two fronts of the streams meet in a region of the casting mold. At least one temperature and / or at least a pressure in the region in which the currents meet, measured. The measured temperature and / or the measured pressure are taken into account during the subsequent production of a second cast component in the casting mold for the selection of the respective temperature and / or the respective pressure and / or the respective triggering time at the respective sprue point during the introduction of the light metal melt.

The procedure according to the invention makes it possible to actively reliably control or regulate the position of the contact surfaces of the filling fronts. In this way, it is achieved that the material flow of the molten metal into the casting mold takes place in a manner compatible with the component, in particular in a way that is reproducible in terms of geometry. In particular, it can be realized that the filling fronts contact one another at intended points. It is particularly preferred if the contact takes place in the vicinity of a vacuum outlet of the casting mold. By providing an individual control for the series of casting operations as a function of the currently measured values, advantageously high process reliability is achieved so that an increase in quality is possible by reducing the scattering of the individual results.

The method is preferably an injection molding process. The sprue points can in particular be tempered. The casting mold can then also be referred to as a hot runner casting mold. The light metal melt is fluid, in particular flowable. For the purpose of the measurement, one or more sensors, detectors, measuring probes or the like can be used. The sensor or sensors, detectors or probes may be incorporated on or in the mold. The respective temperature and / or the respective pressure at the multiple gate points for the subsequent production of a further cast component can be adjusted as a function of the measured temperature. In other words, a change in the set respective temperature and / or the set respective pressure at the multiple gating points can be effected as a function of the deviation of the measured temperature, the actual temperature, from a predetermined temperature, a desired temperature. The single measurement or multiple measurements may be made initially for one or more first components of the series, with subsequent products being made with the found optimized settings, or made periodically during production of the series so as to take into account previous measurements for the manufacture of subsequent products ,

Preferably, the light metal melt is introduced into the mold with elevated pressure compared to the ambient pressure. In other words, the method may be a so-called die casting method in which at least when filling the mold pressure forces greater than the ambient pressure on the molten metal melt act.

A light metal is understood in this illustration to mean a metal whose density is less than 5 g / cm ³ . In particular, the metals are aluminum, magnesium, titanium, lithium and strontium light metals. Particularly preferred in industrial applications, in particular in the context of the invention, the light metals are aluminum, magnesium and titanium, since they are workable with tools.

In a group of preferred embodiments of the method according to the invention, an aluminum alloy or a magnesium alloy is used as light metal. The term alloy also includes the pure metal, which is essentially, in particular within production-related foreign components and / or impurities, free of other constituents. Furthermore, or alternatively, in the process according to the invention preferably a semisolid (semi-solid) Gießbrei with solid phase content or solids content is used. That is, the light metal melt is poured as a semi-solid Gießbrei, in particular, with a non-dendritic, preferably globulitischen solid phase portion. The molten metal may be fluid, in particular flowable, liquid, mushy, muddy, doughy or pasty. The molten metal may have been cooled to a temperature below the liquidus temperature. The processed molten metal may be thixotropic. The molten metal may in particular globulitic and / or non-dendritic Solid, for example, spherical or ellipsoid solids, in the liquid phase portion.

In a concrete embodiment of the method according to the invention for producing a series of cast components, the light metal melt is discharged at the at least two sprue points by hot runner nozzles whose temperature and / or their pressure is adjusted. By means of the adjustable hot runner nozzles, the material flow of the molten metal into the casting mold can be controlled in an advantageous manner with regard to the quantity and the time course of the volume flow.

According to the invention, a temperature distribution and / or a pressure distribution are measured over a specific path or section in the region in which the streams meet. Specifically, measured values can be taken at a number of measuring points, for example at two measuring points on the opposite sides of the expected position of the contact surface of two filling fronts. In this way, differences in the values of the parameters, in particular with regard to the values of the parameters assigned to the individual filling fronts, can be detected, so that individual separate measures for adjusting the temperature and / or pressure at the respective sprue points are derived from this information and subsequently carried out can be.

With regard to the aim of a reproducible, consistently high quality, it is particularly preferred in the method according to the invention to make or to make an adjustment of the respective temperature and / or the respective pressure at the respective sprue point when introducing the light metal melt such that during each individual production of a cast component in FIG In the series, the streams essentially meet one another at the same location and, on the other hand, at the same temperature and / or pressure within tolerance intervals. If a series of products is manufactured in this way, then the position of the contact surface of the filling streams can be adjusted in a targeted manner. In this case, contact surfaces can be placed at desired positions for the specific product geometry, for example those in which a structural weakening of the product is desired.

In the context of the inventive idea is also an apparatus for producing a cast component. The device according to the invention may preferably suitably carry out a method for producing a series of cast components with individual or all Be features or feature combinations according to this representation. The device comprises a mold having a cavity and a plurality of sprue points, through which a light metal melt, each with a temperature and pressure in the mold can be introduced such that the light metal melt along at least two paths in at least two streams, each with a front into the mold flows, wherein at least two fronts of the streams meet in a region of the mold. It further comprises at least one device for measuring the temperature and / or at least one device for measuring the pressure, which are arranged in the region in which the streams meet. In addition, the device comprises a temperature and / or pressure control device at the plurality of gate points for taking into account the measured temperature and / or the measured pressure in the subsequent production of a second cast component in the mold for the selection of the respective temperature and / or the respective Pressure at the respective sprue point when introducing the light metal melt.

In a specific embodiment, the control device of the device according to the invention may have a computing unit and a software program running on the arithmetic unit, which enables a calculation or retrieval of values of temperature and / or pressure to be set at the plurality of sprue points for subsequent casting operations as a function of the measured values , and / or contain one or more tables (look-up tables), which permit an assignment of respective values of temperature and / or pressure to be set at the plurality of gating points in function of the measured values.

The topology of the cavity can be complex so that detailed structured components are available as products. For this purpose, the cavity of the mold may be a not simply connected space. Expressed more vividly, within the cavity there can exist at least one closed path that contracts steadily to a point outside the cavity, in other words, shortens with the inclusion of the orbited center. For example, the cavity can be like a frame, lattice-like or net-like or have handle-like space regions with at least two transition points to the residual volume. When filling such cavities with molten metal, starting from a plurality of sprue points, there are widespread situations in which filling fronts flow in partial areas toward one another and finally form a contact surface. Often it makes sense to fill the mold with molten metal starting from only one starting point without the risk of generating casting defects.

In a particularly preferred embodiment of the device according to the invention, at least one of the gate points is formed by the outlet of a hot runner nozzle.
In this case, tempering devices of the hot runner nozzles are activated with the values determined as a function of the measured values. The control device can be designed such that it also performs the control of the temperature control of the hot runner nozzles. A temperature control can be for example a cooling device, preferably a CO ₂ impulse cooling.

In the procedure according to the invention, specifically by means of the method according to the invention with individual or all features or feature combinations according to this representation or the device according to the invention with individual or all features or feature combinations according to this representation, cast components are available in series with consistently high quality. The invention therefore provides a cast component that is obtained in a method with individual or all features or feature combinations according to this representation and / or by means of a device with individual or all features or feature combinations according to this representation.

In concrete applications, the cast components may be structural components for assemblies of a vehicle, in particular an agricultural vehicle, a wheeled vehicle, for example a trackless automobile.

Figur 1

eine Skizze eines Gießwerkzeugs mit zwei Heißkanalaustrittsdüsen zur Durchführung einer Ausführungsform eines erfindungsgemäßen Verfahrens zum Herstellen einer Serie von Gussbauteilen,

Figur 2

eine Skizze einer Struktur eines Systems zur Steuerung einer Ausführungsform eines erfindungsgemäßen Verfahrens zum Herstellen einer Serie von Gussbauteilen, und

Figur 3

eine vergrößerte Darstellung des Heißkanals mit zwei Heißkanalaustrittsdüsen.

Further advantages and advantageous embodiments and developments of the invention will be described with reference to the following description with reference to the figures: It shows in detail:

FIG. 1

2 shows a sketch of a casting tool with two hot runner nozzles for carrying out an embodiment of a method according to the invention for producing a series of cast components;

FIG. 2

a sketch of a structure of a system for controlling an embodiment of a method according to the invention for producing a series of cast components, and

FIG. 3

an enlarged view of the hot runner with two hot runner nozzles.

The FIG. 1 is a sketch of a casting tool with two hot runner nozzles for carrying out an embodiment of a method according to the invention for producing a series of cast components. In the casting mold 30 is a casting mold 10, which has a frame-like cavity. By means of an on the basis of FIG. 3 described in detail, not shown here hot runner 12 is the mold 10 at a first hot runner nozzle 14 and a second hot runner 16 in operation a light metal melt, here a magnesium melt fed as a semi-solid cast pulp in the die casting. In order to fill the cavity, the semisolid casting slurry flows through the cavity in streams in various ways such that in each case two converging fronts of the streams meet in two regions of the casting mold 10, whereby a contact surface is formed. This meeting takes place in areas of the mold that are reachable from the molten metal in essentially the same time from the two hot runner nozzles 14,16. In the concrete in the FIG. 1 In the embodiment shown, this is the case in each case in the vicinity of the two vacuum supports 18 for die casting.

According to the invention, for the active control of the exact position of the contact surfaces in each of the two areas addressed at different locations grouped pairs of sensors are arranged: A temperature controller 20 is connected to four temperature sensors 24, and a pressure controller 22 with four pressure sensors 26 for data transmission , In each case, a temperature sensor 24 and a pressure sensor 26 are adapted to measure the prevailing temperature or the prevailing pressure at a position which passes one of the cavities filling the streams of Leichtmetallgießbreis before he meets with the oncoming stream and forms a contact surface. Quantitatively, the position about 350 to 450 mm in this embodiment is away from the expected position of the contact surface.

The FIG. 2 outlined a structure of a system for controlling an embodiment of a method according to the invention for producing a series of cast components, which already in connection with the FIG. 1 designated components like reference numerals are used. It is possible to calculate or to predict at which point the two contact surfaces are formed for a specific production process of a cast component from the progressions of the parameters temperature or pressure respectively measured as a function of time at the four different locations. The course of the measured parameters is dependent on the setting parameters, in particular the time, the temperature and the pressure, when introducing the casting slug through the hot runner nozzles 14, 16. Therefore, the parameters measured at the various locations of the parameters Temperature or pressure can be influenced by one, several or all adjustment parameters are changed. According to the invention signals from the temperature controller 20 and the pressure controller 22 are transmitted to a hot runner controller 28. In the hot runner control device 28 it is determined which specific controls, which specific values of the adjustment parameters, are required in order to achieve desired profiles of the parameters temperature or pressure at the specific different locations. For this purpose, the corresponding functional relationship is deposited in the hot runner control device 28, for example in the form of tables. The hot runner controller 28 then controls the individual hot runner nozzles 14,16 accordingly.

The FIG. 3 shows an enlarged view of the hot runner 12 with two hot runner nozzles 14,16. The feeding of the light metal melt, here the magnesium alloy is effected by a common supply line, which branches to the individual outlets. Both an adjustable pressure generating device and an adjustable tempering device are provided on each of the hot runner nozzles 14,16, so that the pressure and temperature parameters prevailing during die casting can be controlled.

Not shown in the drawing, a further development also includes pairs of sensors (temperature sensors and pressure sensors) each near the hot runner nozzles 14,16, quantitatively about 350 to 450 mm away from their position in the two directions into which the light metal melt flows into the cavity , As a result, additional information about the development over time of parameters of the molten metal, in particular its temperature, can be obtained and advantageously also taken into account in the method according to the invention.

As an example of the concrete application, the magnesium alloy AZ91 should be mentioned here. This can be processed according to the invention in the form of a thixotropic casting slurry in the temperature range from 560 to 620 degrees Celsius. As an operating point, the temperature is typically 585 degrees Celsius ± 10 degrees Celsius. The solid phase content varies in the specified temperature interval partially sensitive to the temperature, so that the consideration according to the invention of the measured temperatures and pressures in areas where currents of the incoming molten magnesium in the mold, special importance to achieve a uniform quality in a series of manufactured castings achieve.

LIST OF REFERENCE NUMBERS

10

mold

12

hot runner

14

first hot runner outlet nozzle

16

second hot runner outlet nozzle

18

Vacuum support

20

Temperature controller

22

Print controller

24

Temperature sensor

26

pressure sensor

28

Heißkanalregelgerät

30

casting tool

Claims (9)

1. Method for producing a series of cast components, in which method a casting mould (10) with a cavity and a plurality of gate points is provided, a molten light metal is introduced into the casting mould (10) through at least two gate points at in each case one temperature and one pressure in order to produce a first cast component, and the molten light metal flows into the casting mould along at least two paths in at least two flows with in each case one front, at least two fronts of the flows meeting in a region of the casting mould, characterized in that at least one temperature and/or at least one pressure are/is measured in the region, in which the flows meet one another, and the measured temperature and/or the measured pressure are/is taken into consideration during the subsequent production of a second cast component in the casting mould (10) for the selection of the respective temperature and/or the respective pressure and/or the respective triggering instant at the respective gate point during the introduction of the molten light metal, measured values being taken at two measuring points on sides which lie opposite one another of the expected position of the contact area of two filling fronts.
2. Method for producing a series of cast components according to Claim 1, characterized in that the molten light metal is introduced into the casting mould (10) at an elevated pressure in comparison with the ambient pressure.
3. Method for producing a series of cast components according to Claim 1 or 2, characterized in that an aluminium alloy or a magnesium alloy is used as light metal, and in that the molten light metal is cast as a semi-solid casting paste with a solid fraction.
4. Method for producing a series of cast components according to one of Claims 1 to 3, characterized in that the molten light metal is output at the at least two gate points through hot runner nozzles, the temperature and/or pressure of which are/is set.
5. Method for producing a series of cast components according to one of Claims 1 to 4, characterized in that a temperature distribution and/or a pressure distribution are/is measured over a defined path in the region, in which the flows meet one another.
6. Method for producing a series of cast components according to one of Claims 1 to 5, characterized in that setting of the respective temperature and/or the respective pressure at the respective gate point during the introduction of the molten light metal is carried out in such a way that, during each individual production of a cast component in the series, the filling fronts of the flows make contact with one another reproducibly at provided points in the casting mould and at the same temperature and/or the same pressure within tolerance intervals.
7. Apparatus for producing a series of cast components by way of a method according to one of the preceding Claims 1 to 6, having a casting mould (10) with a cavity and a plurality of gate points (14, 16), through which a molten light metal can be introduced at in each case one temperature and one pressure into the casting mould in such a way that the molten light metal flows into the casting mould (10) along at least two paths in at least two flows with in each case one front, at least two fronts of the flows meeting in a region of the casting mould (10), characterized by at least one apparatus (20, 24) for measuring the temperature and/or at least one apparatus (22, 26) for measuring the pressure, which are/is arranged in the region, in which the flows meet one another, and a control unit (28) for temperature and/or pressure at the plurality of gate points, in order to take the measured temperature and/or the measured pressure into consideration during the subsequent production of a second cast component in the casting mould (10) for the selection of the respective temperature and/or the respective pressure at the respective gate point during the introduction of the molten light metal.
8. Apparatus for producing a cast component according to Claim 7, characterized in that the cavity of the casting mould (10) is a space which is not simply contiguous.
9. Apparatus for producing a cast component according to Claim 7 or 8, characterized in that at least one of the gate points is formed by the outlet (14, 16) of a hot runner nozzle.

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