Process for casting components

Abstract

Method (20) for casting components, comprising the steps of: filling (21) a casting mold (2) with a casting material (10), and pressing (23) the casting material (10) for a predetermined pressing time, wherein the pressing (23) begins after a predetermined delay time has elapsed after the filling (21), and wherein the casting material (10) is a pure metal.

Description

[0001] The present invention relates to a method for casting components and a casting device for casting components.

[0002] Processes and devices for casting components are known, for example, rotors for electric motors. Die casting is typically used for this purpose. It is also known that additional pressing tools, so-called "squeezers," are used to prevent porosity caused by volume contraction during solidification by pressing the component. Conflicting requirements regarding material selection and effective pressing often arise, since, for example, pressing materials with optimal electrical properties is often difficult or impossible using the conventional die casting process.

[0003] It is therefore an object of the present invention to provide a method for casting components with which components with optimal electrical properties and high material quality can be provided efficiently and cost-effectively. Furthermore, it is an object of the invention to provide a casting device for casting components that has a simple design and with which components with optimal electrical and mechanical properties can be cast efficiently.

[0004] The object is achieved by a method according to claim 1 and by a casting device according to claim 12.

[0005] The method according to the invention for casting components comprises the steps: - Filling a casting mold with a casting material, and - Pressing the casting material for a predetermined pressing time.

[0006] Pressing only begins after a predetermined delay period has elapsed after filling. A pure metal is used as the casting material in this process.

[0007] In particular, pressing begins immediately after the predetermined delay time has elapsed.

[0008] Preferably, the start of the delay time is considered to be an end time at which the complete filling of the casting mold with the casting material is completed.

[0009] A pure metal is considered to be, in particular, a metal or a metal alloy whose main component is a metal having a concentration of at least 90%, preferably at least 95%, particularly preferably at least 97%.

[0010] In other words, the method first involves completely filling the casting mold with the casting material. Preferably, the casting is performed by die casting. After the casting mold has been completely filled, a predetermined delay time is allowed before the casting material is pressed. This allows the casting material, for example, to cool slightly and solidify before pressing begins.

[0011] The process offers the advantage of enabling the production of components of particularly high quality. In particular, it was recognized that the special coordination of the process sequence, with the delayed start of pressing only after the predetermined delay time, also enables the simple and efficient pressing of pure metal as a casting material. This allows the use of pure metals with a particularly high concentration of the main component, which, for example, enables the production of components with particularly high-quality electrical properties. For example, the process can be used to produce rotors for electric motors, particularly asynchronous motors, with optimal component properties particularly efficiently.By pressing the cast material, a particularly good and homogeneous material quality of the manufactured components can be achieved, whereby porosity in the components can be reduced in particular.

[0012] Preferably, the casting material has an aluminum content of at least 95%. This means that the casting material used is, in particular, aluminum or an aluminum alloy containing at least 95% aluminum. This allows for the production of lightweight components with optimal electrical properties, for example, for use in electric motors.

[0013] The casting material is particularly preferably pure aluminum. Preferably, the casting material has an aluminum content of at least 99%, preferably at least 99.7%.

[0014] Preferably, the delay time is a multiple of the pressing time, in particular at least twice. This allows for cooling and partial solidification of the casting material, particularly when casting pure aluminum, by selecting a sufficient delay time, allowing for efficient and reliable pressing.

[0015] Preferably, the delay time is at least 1 second, preferably a maximum of 10 seconds, in particular a maximum of 3 seconds. This allows for a simple and time-efficient implementation of the method, reliably enabling effective pressing of the casting material to ensure optimal electrical and mechanical properties of the component to be manufactured.

[0016] More preferably, the pressing time is at least 0.1 second, preferably a maximum of 1 second. This allows the pressing to be carried out reliably and time-efficiently, achieving optimal contraction of the casting material and enabling an optimal and homogeneous material structure of the component to be produced.

[0017] Preferably, pressing is carried out with a pressing pressure of at least 100 bar, preferably a maximum of 1000 bar. Particularly preferably, pressing is carried out with a pressing pressure of at least 400 bar, and in particular a maximum of 500 bar. This enables effective pressing of the casting material, particularly adapted to the delay time and pressing time, in order to reliably reduce porosity, especially when casting pure aluminum, and thus enable optimal material quality of the component to be cast.

[0018] The casting mold further preferably has a material reservoir provided for casting material that is pressed during the pressing process. In particular, the material reservoir is configured to provide casting material to be pressed during the pressing process. This means that the material reservoir is provided in addition to the component cavity of the casting mold, which shapes the component to be cast. The material reservoir thus provides a cavity into which casting material can flow when the casting mold is filled, whereby this casting material can be pressed during the pressing process. This allows components with the desired geometries and with particularly good material properties to be manufactured particularly easily and reliably.

[0019] More preferably, the material reservoir has a predetermined volume that corresponds to at least twice, preferably a maximum of five times, the expected pore volume that occurs during casting without pressing. This means that the size of the material reservoir is dimensioned such that its volume is at least twice the expected pore volume during casting without pressing. This pore volume corresponds in particular to the total volume of all pores in the component, which occurs, for example, due to volume contraction during solidification. In particular, the pore volume is assumed for a casting process in which all parameters and properties of the casting tool are identical, except that no pressing takes place during the process.Such an expected pore volume can be estimated or determined, for example, during the design of the casting process, taking into account the tool properties of the casting tool and / or the process parameters and / or the material properties. Alternatively or additionally, it is possible for a person skilled in the art to determine such an expected pore volume by means of simple experiments, for example, by performing the casting process once or several times without pressing. This makes it easy to reliably provide a sufficient amount of casting material to compensate for the volume contraction during solidification, in order to efficiently and reliably achieve the desired component geometry of the component to be manufactured.

[0020] Preferably, pressing is carried out using at least one metal pin and / or at least one contour punch. A cylindrical pin, for example made of steel, can be used as the metal pin. A contour punch can, in particular, be a punch with any geometry, adapted, for example, to the casting mold and / or the component to be cast. Preferably, the metal pin and / or contour punch can be actuated by a hydraulic unit. This enables pressing to be carried out simply and precisely with high pressing forces.

[0021] Particularly preferably, a rotor for an electric motor, in particular for an asynchronous motor, is produced by the method. Such a rotor can, for example, comprise a laminated core comprising a plurality of axially stacked laminations, wherein electrically conductive rods and preferably additional short-circuit rings at the axial ends of these rods are cast into the laminated core by the method. Rotors with particularly good electrical properties and particularly high material quality can be provided by the method.

[0022] Furthermore, the invention leads to a casting device for casting components, comprising a casting mold, a filling device configured to fill the casting mold with a casting material, a pressing device configured to press the casting material located in the casting mold, and a control unit. The control unit is configured to actuate the filling device and the pressing device. Furthermore, the control unit is configured to carry out the described method, in particular by actuating the filling device and the pressing device.

[0023] The invention is explained in more detail below using an exemplary embodiment. In the drawings: Fig. 1 a highly simplified schematic view of a casting device for casting components, which is designed to carry out a method according to a preferred embodiment of the invention, and Fig. 2 a highly simplified schematic view of the method according to the invention.

[0024] In the following, a preferred embodiment of a method for casting components, which is carried out by means of a casting device 1, is explained. Fig. 1 and Fig. 2. Identical or functionally identical components are always provided with the same reference symbols.

[0025] Rotors for electric motors, in particular for asynchronous motors, can be produced by means of the casting device 1 according to the invention. Such rotors comprise a laminated core having a plurality of laminations stacked along a laminated core axis. This laminated core has a plurality of axial grooves and / or through-holes into which a highly electrically conductive metal is to be introduced in order to form axial bars through the laminated core. In addition, a short-circuit ring is provided on each of the two axial end faces of the laminated core, which extends in the circumferential direction and connects all of the bars to one another. By means of the casting device 1, the bars and short-circuit rings can be cast directly into or onto the laminated core as a single, one-piece component and in a single step. This component is referred to below as the component to be cast.

[0026] The component to be cast is cast from pure aluminum as casting material 10. The pure aluminum has an aluminum content of at least 99%, preferably at least 99.7%.

[0027] The casting device 1 is designed to produce the component by means of pressure casting, with additional pressing, also known as “squeezing”, being provided.

[0028] First, the casting device 1 is described using the Fig. 1, then procedure 20 based on the Fig. 2.

[0029] The casting device 1 comprises a casting mold 2 with a casting cavity 29 into which the casting material 10 is poured to produce the component to be cast. For this purpose, the casting device 1 comprises a filling device 3, which is configured to pressurize the casting material 10 into the casting cavity 29. The filling device 3 can be actuated by a control unit 5.

[0030] In addition, the casting device 1 comprises a pressing device 4, by means of which the pressing of the casting material 10 can be carried out.

[0031] The pressing device 4 comprises a plurality of pressing dies, which are designed in particular as cylindrical metal pins 45. All metal pins 45 are arranged parallel to an axis 44 and connected to a common pressing plate 42. In particular, all metal pins 45 are mechanically fixed to the pressing plate 42.

[0032] The pressing plate 42 can be actuated by means of an actuating device 43, in detail moved along the axis 44 in the direction of the casting mold 2. The actuating device 43 can also be actuated by the control unit 5.

[0033] The pressing device 4 is designed in such a way that in the unactuated normal state, which is Fig. 1, a material reservoir 29 is provided for casting material that is pressed during pressing 23. The material reservoir 29 is part of the casting cavity 20 and can be viewed in particular as an extension for the material that is pressed during pressing 23.

[0034] The material reservoir 29 is designed such that it has a predetermined volume that corresponds to at least twice, preferably a maximum of five times, the expected pore volume that occurs during casting without pressing. This means that the size of the material reservoir 29 is dimensioned such that its volume is at least twice the expected pore volume during casting without pressing.

[0035] In procedure 20 (cf. Fig. 2) In a first step, the casting mold 2 is filled 21 with the casting material 10 by means of the filling device 3.

[0036] Subsequently, when the filling 21 is completely finished, the next step is to wait 22 for a predetermined delay time.

[0037] After the delay time has elapsed, the next step is immediately pressing 23 the casting material 10 for a predetermined pressing time.

[0038] After the pressing time has elapsed, the actuation of the pressing plate 42 is stopped and further solidification 24 of the casting material can take place, for example for a predetermined cooling time.

[0039] After the cooling time has elapsed, the finished component can be ejected 25 from the casting mold 2.

[0040] The delay time of the waiting step 22 is a multiple of the pressing time of the pressing step 23. Specifically, the delay time is at least 2 seconds, preferably a maximum of 3 seconds. The pressing time is preferably at least 0.1 second and a maximum of 1 second.

[0041] Furthermore, the pressing is carried out with a pressing pressure of preferably at least 400 bar and a maximum of 500 bar.

[0042] Method 20 offers the advantage that components with particularly good material quality and dimensional accuracy can be manufactured. Manufacturing can be carried out in a particularly simple and cost-effective manner using simple means. By specifically coordinating the process sequence with the delayed start of pressing 23 only after the predetermined delay time, the pressing of pure aluminum as a casting material can also be made simple and efficient. Pressing 23 can reduce porosity in the component, allowing components with particularly high material quality to be manufactured reliably and uniformly. The use of pure aluminum allows the production of rotors for electric motors with particularly good electrical properties. List of reference symbols 1 device 2 casting mold 3 Filling device 4 Pressing device 5 Control unit 10 Casting material 20 procedures 21 Fill 22 Waiting 23 presses 24 Solidification 25 Eject 29 Material reservoir 42 press plate 43 Actuating device 44 Axis 45 metal pin

Claims

[1] Method for casting components, comprising the steps: - filling (21) a casting mold (2) with a casting material (10), and - pressing (23) the casting material (10) for a predetermined pressing time, - wherein the pressing (23) begins after a predetermined delay time has elapsed after the filling (21), and - wherein the casting material (10) is a pure metal. [2] Method according to claim 1, wherein the casting material (10) has an aluminum content of at least 95%. [3] Method according to one of the preceding claims, wherein the casting material (10) is pure aluminum, and in particular has an aluminum content of at least 99%, preferably of at least 99.7%. [4] Method according to one of the preceding claims, wherein the delay time is a multiple of the pressing time. [5] Method according to one of the preceding claims, wherein the delay time is at least 1 second, preferably a maximum of 10 seconds, in particular a maximum of 3 seconds. [6] Method according to one of the preceding claims, wherein the pressing time is at least 0.1 second, preferably at most 1 second. [7] Method according to one of the preceding claims, wherein the pressing (23) is carried out with a pressing pressure of at least 100 bar, preferably at most 1000 bar, preferably at least 400 bar, in particular at most 500 bar. [8] Method according to one of the preceding claims, wherein the casting mold (2) has a material reservoir (29) for casting material (10) to be pressed during the pressing (23). [9] Method according to claim 8, wherein a volume of the material reservoir (29) corresponds to at least twice, preferably at most 5 times, an expected pore volume in a casting without pressing (23). [10] Method according to one of the preceding claims, wherein the pressing (23) is carried out by means of at least one metal pin (45) and / or at least one contour stamp. [11] Method according to one of the preceding claims, wherein a rotor for an electric motor, in particular an asynchronous motor, is produced by means of the method (20). [12] Casting device for casting components, comprising: - a casting mold (2), - a filling device (3), - a pressing device (4), and - a control unit (5) which is arranged to actuate the filling device (3) and the pressing device (4), - wherein the control unit (5) is configured to carry out the method (20) according to one of the preceding claims.

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