EP2072161B1 - Method for controlling the pouring movement of a ladle - Google Patents

Abstract

The method for controlling a pouring movement of a spoon (18) for pouring a molten material (12) e.g. molten metal into a casting mold (14) e.g. cast, comprises predetermining a mold-specific casting characteristic (A) with respect to a volume of the molten product in the mold via a time course and storage of the casting characteristic, determining a spoon-specific pouring characteristic as function of a volume of the molten product from the spoon over the inclination of the spoon and storage of the pouring characteristic, and automatically generating the progress of the pouring movement. The method for controlling a pouring movement of a spoon (18) for pouring a molten material (12) e.g. molten metal into a casting mold (14) e.g. cast, comprises predetermining a mold-specific casting characteristic (A) with respect to a volume of the molten product in the mold via a time course and storage of the casting characteristic, determining a spoon-specific pouring characteristic as function of a volume of the molten product from the spoon over the inclination of the spoon and storage of the pouring characteristic, and automatically generating the progress of the pouring movement, where the volume of the molten product is determined on the basis of the casting characteristic at each time, and is equated to an optimal volume of the molten product, so that an optimal inclination is regulated to each time via the pouring characteristic. The casting characteristic is simulated as function of the volume of the molten product over the time course by simulation software or manually simulated. The pouring characteristic is empirically determined as a function of the pouring volume of the molten-product over the spoon inclination, where a full-filled spoon is gradually inclined in an automatic calibration procedure until completely emptying the spoon. During the tilting motion, the filled quantity is measured by an electronic balance and the measured value is transferred to a controller (32), in which the measured values are recorded and are created under the knowledge of the specific density of the molten product. The pouring characteristic is analytically calculated as a function of the pouring volume of the molten-product over the spoon inclination that is accumulated volume, under the knowledge of spoon geometry such as three-dimensional-model and under a condition of a horizontally lying molten-product reflector. After a change of spoon geometry, the pouring characteristic is determined according to the new spoon geometry. The mold is moved from an inclined initial position into a vertical end position, where the progress of the movement of the mold in a characteristic for the tilting motion (mold characteristic) is determined and stored as function of the mold position over a time course. The mold characteristic is determined by a simulation method and with external control by recording the mold movement using a coupled position detector (34) during a casting process. The pouring movement of the spoon and the movement of the mold are controlled by the same control. The casting characteristic and the mold characteristic lie in a common time axis. The mold position on the basis of the casting characteristic at each time during the casting process from the mold characteristic and the spoon inclination on the basis of the optimal casting volume over the pouring characteristic are determined so that an automatic control of the inclination of the spoon and the mold takes place. The mold is controlled by an independent controller. The actual position of the mold is detected by the position detector and is transferred to the control of the spoon, where a casting-melt volume is obtained from the casting characteristic at each time and is determined via the associated pouring-melt volume by the pouring characteristic of the associated spoon position. The tracking of the pouring movement of the spoon takes place by a kinematic transformation, where the actual position of the mold is considered and a tool center point is adjusted in such a way that a curvature of the spoon is moved over a charging hole of the mold. Intermediate values are interpolated between discretely measured characteristic values and are provided by controlling the casting machine at a drive of the mold and/or a spoon drive, so that it results a continuous movement. An off-line program generation is carried out, where a movement program for controlling the automation equipment is produced over an algorithm from information of the casting characteristic, pouring characteristic and optionally mold characteristic. An on-line movement generation is carried out, where the position of the spoon and/or the mold is continuously determined via a time course from the given characteristic data and/or characteristic tables and is immediately adjusted by controlling the automation equipment as casting machine.

Description

The invention relates to a method for controlling a pouring movement of a ladle for pouring a molten metal such as molten metal into a mold such as mold, wherein a mold-specific Eingießkennlinie is predetermined and stored in dependence of a cast into the mold melted volume over time.

A method of the type mentioned above is in DE-A-10 2006 034 044 described. In this case, a casting curve for a robot controller of a robot is detected, which leads a ladle. With a remote control device, a manual pouring of a melt from the ladle is performed. During pouring, the time course of the robot movement and / or the time course of the casting weights are recorded and stored. The stored time history is provided for use in the robot controller. Further, a method for casting castings and a robot system for detecting a casting curve will be described. Changes in the geometry of the pouring ladle, for example when using different ladles, are not taken into account in the known method.

In the WO-A-85/04607 a method for controlling the repeated casting of molds and a casting plant is described. During a manual or after an empirically predetermined curve controlled casting process is continuously the weight of the ladle and thus the melt therein and determines the level in a casting funnel. The course of the pan weight during the casting process, recorded by means of measuring doses, is stored by means of an electronic control. Further pouring operations are then automatically controlled, in which the ladle is tilted so that there is the same course of the weight. Also in this method, the change of a Gießlöffelgeometrie is not considered.

Other methods of controlling the pouring motion of a ladle are also out DE 32 23 803 A1 . JP 10058120 . JP 07227668 known.

Chill casting is used to cut metal foils with liquid molten aluminum to produce parts with complex geometries. The filling with molten metal can u. a. also be automated with robots or other automation devices.

For the quality of chill castings, the time course of material filling is of the utmost importance. In order to determine the optimal course of the material filling process, there are simulation systems that provide the input quantity (material flow) over the course of time in the form of a pouring characteristic as output information.

The automation device for filling the molten metal into the mold is equipped with a ladle. The ladle is attached to a numerically controlled axle and is tilted over the casting axis during the pouring process. Depending on the kinematic arrangement of the ladle on the automation device, it may be necessary to coordinate the movement of several axes so that the required pouring movement is achieved.

Since the timing of the pouring stream depends critically on the geometry of the pouring ladle, it is necessary to adjust the pouring motion for a given pouring ladle geometry. This is usually done empirically. After changing the ladle, especially when changing the geometry of the ladle, the pouring movement must be optimized again.

Based on this, the present invention is based on the object of developing a method of the type mentioned at the outset in such a way that the pouring movement can be completely automated, planned and controlled. Also, the set-up times are to be shortened after a change of Gießlöffelgeometrie.

• Ermittlung einer gießlöffelspezifischen Ausgießkennlinie als Funktion eines aus dem Gießlöffel ausgegossenen Schmelzgutvolumens über der Neigung des Gießlöffels und Speichern der (zumindest einen) Ausgießkennlinie,
• automatische Generierung des zeitlichen Verlaufs der Ausgießbewegung, wobei auf der Grundlage der Eingießkennlinie zu jedem Zeitpunkt das notwendige Eingießschmelzgutvolumen bestimmt wird, welches einem optimalen Ausgießschmelzgutvolumen gleichgesetzt wird, dem über die Ausgießkennlinie eine optimale Neigung zu jedem Zeitpunkt zugeordnet ist.

The object is achieved according to the invention by the following method steps:

• Determination of a pouring bucket-specific pouring characteristic as a function of a pouring material volume poured out of the pouring ladle over the inclination of the pouring spoon and storage of the (at least one) pouring characteristic,
• automatic generation of the time course of the pouring movement, wherein on the basis of Eingießkennlinie at any time the necessary Eingießschmelzgutvolumen is determined, which is equated with an optimum Ausgießschmelzgutvolumen, which is assigned via the Ausgießkennlinie an optimal slope at any time.

The pouring movement is automatically generated on the basis of a given casting-specific pouring characteristic and at least one casting spoon-specific pouring characteristic. The generated data are the position and inclination of the ladle as a function of time. The movement is controlled in such a way that results in a continuous speed profile of all axes involved in the casting process, for example of a robot.

The basis for automatic motion generation is the pouring characteristic, which defines the required filling quantity (material flow) over the course of time. The characteristic curve is read into the controller of the automation device and can be visualized there and, if necessary, adjusted manually and graphically and / or numerically.

The pouring curve must be in the form of "poured material volume over time", ie. accumulated volume. It can be specified by simulation software or manually.

If the pouring characteristic is present only as "material flow per unit of time", then the accumulated material volume over the course of time must be calculated by integral formation. Since the material flow characteristic is not always functionally describable, numerical integration methods are used here.

The pouring characteristic must be in the form of "poured volume of material above the bucket tilt", i. H. accumulated volume. This characteristic can be created using two different methods.

Preferably, the pouring characteristic is determined empirically as a function of the poured out volume of molten material above the pouring ladle inclination. In an automatic calibration process, a fully filled ladle is gradually tilted until it is completely emptied. After every single step or continuously, the amount of material poured out is measured by an electronic balance and the measured value is transmitted to the automatic casting machine control. The control records the measured values and, knowing the material-specific volume weight, creates a characteristic curve of the (accumulated) material volume. After changing the geometry of the pouring ladle, the pouring characteristic must be determined again.

According to another preferred method, the pouring characteristic as a function of the poured out volume of molten material above the casting ladle inclination, i. H. accumulated volume, with knowledge of the casting bucket geometry as 3D model and assuming a horizontal melt level mirror calculated analytically.

From the knowledge of the pouring characteristic and the pouring characteristic curve, the time course of the pouring movement can be calculated and controlled automatically.

In addition to the procedure described above with a fixed casting machine, the casting machine can also be tilted during the pouring movement in another procedure (tilting molding machine). In this case, the mold can be transferred during the pouring, for example, from an inclined initial position to a vertical end position. Thus, in addition to controlling the timing of the pouring movement and the spatial movement of the pouring position by the movement of Kippgießmaschine to control so that the ladle is always correct to Eingießposition.

The time profile of the mold movement can be determined and stored in a characteristic curve for the tilting movement over the course of time.

According to a preferred procedure, the characteristic curve for the tilting movement over time can be determined by a simulation software. Alternatively, it is also possible to determine the characteristic curve for the tilting movement over time by recording the mold movement with the aid of a coupled position controller during a real pouring process, namely when the mold is moved by an external control.

A first procedure provides that both the pouring movement of the ladle and the movement of the mold are controlled by one and the same controller, wherein the Eingießkennlinie and the characteristic for the tilting movement are based on a common time axis, starting from the Eingießkennlinie to each Timing during the pouring from the characteristic curve for the tilting movement the required Gießformstellung and starting from the optimum pouring volume on the Ausgießkennlinie the corresponding Gießlöffelneigung is determined, whereby an automatic control of the inclination and the position of the ladle and the mold takes place.

Alternatively, it is possible to control the mold by an independent controller, wherein the current position of the mold is detected by a position sensor coupled thereto and transmitted to the control of the ladle, wherein the Eingießkennlinie taken at any time a Eingießvolumen and the associated pouring volume by means of Ausgießkennlinie the associated inclination and position of the ladle is determined, wherein the tracking of the pouring of the ladle is carried out by a kinematic transformation, taking into account the current position of the mold and wherein a tool Center Point (TCP) is tracked so that a spout of the ladle is always moved over an insertion opening of the mold.

A further preferred procedure provides that interim values are respectively interpolated between discretely tapped characteristic values and output by the controller of the automatic casting machine to a drive of the casting mold and / or a casting spoon drive, so that a continuous movement results.

Another preferred procedure is an offline program generation, wherein a motion program for the control of the automation device is generated via an algorithm from information of Eingießkennlinie, Ausgießkennlinie and possibly. Characteristic curve for the tilting movement. This method has the advantage that the generated program can be archived, manually changed and possibly transferred to other casting machines.

A further preferred procedure is characterized by an online generation of motion, wherein the required position or inclination of the ladle and / or the mold continuously determined from the given characteristic data or characteristic tables over time and set immediately by the controller of the automation device such as casting machine ,

The presented methods offer the advantage that a casting task can be completely automated, planned and executed. In particular, the automatic calibration after changing the Gießlöffelgeometrie significantly reduces set-up times.

For more details, advantages and features of the invention will become apparent not only from the claims, the features to be taken these - in itself and / or in combination but also from the following description of the drawing to be taken preferred embodiments.

Fig. 1

schematische Darstellung eines Gießautomaten mit Gießlöffel und Kokille,

Fig.

2a eine Eingießkennlinie als Funktion eines in eine Gießform einzugießenden Schmelzgutvolumens über dem Zeitverlauf,

Fig. 2b

eine Ausgießkennlinie als Funktion eines aus dem Gießlöffel ausgegossenen Schmelzgutvolumens über der Neigung des Gießlöffels,

Fig. 2c

eine Kennlinie für die Kippbewegung als Funktion der Gießformstellung über dem Zeitverlauf,

Fig. 3

Generierung der Gießlöffelbewegung auf der Grundlage von Eingießkennlinie, Ausgießkennlinie und Kennlinie für die Kippbewegung bei Steuerung der Gießform durch die Gießautomatsteuerung und

Fig. 4

Ermittlung der Gießformstellung auf der Grundlage der Eingießkennlinie, der Ausgießkennlinie sowie der Kennlinie für die Kippbewegung, wobei die Gießform von einer unabhängige Steuerung bewegt wird.

Show it:

Fig. 1

schematic representation of an automatic pouring machine with ladle and mold,

FIG.

FIG. 2a shows a pouring characteristic as a function of a molten material volume to be poured into a casting mold over the course of time, FIG.

Fig. 2b

a pouring characteristic as a function of a volume of molten material poured out of the ladle over the inclination of the ladle,

Fig. 2c

a characteristic for the tilting movement as a function of the casting mold position over time,

Fig. 3

Generation of Gießlöffelbewegung based on Eingießkennlinie, Ausgießkennlinie and characteristic for the tilting movement in the control of the mold by the casting machine control and

Fig. 4

Determining the casting mold position on the basis of the pouring characteristic, the pouring characteristic and the characteristic for the tilting movement, wherein the mold is moved by an independent controller.

Fig. 1 shows purely schematically an apparatus 10 for filling a melted material 12 such as molten metal in a mold such as mold 14 for producing a molded part. The apparatus 10 comprises an automation device 16, such as a casting machine or robot, which is equipped to fill the liquid metal 12 with a ladle 18. The ladle 18 is attached to a numerically controlled axle 20 and is at the Eingießvorgang inclined over this axis. In order to achieve the required pouring movement of the ladle 18, further kinematic axes 22, 24, 26, 28 of the robot 16 can be coordinated.

The mold 14 may have a tilting device 30, with which the mold 14 during the pouring process from an example inclined initial position in an example vertical end position is tilted. The control of the robot 16 via a controller 32 which can simultaneously control the tilting device 30 of the mold. Alternatively, the tilting device 30 may also be controlled by an independent controller 33. In this case, the position of the mold 14 is detected via an external position encoder 34 and passed to the controller of the robot 16.

The invention is based on the idea, starting from a given Kokillpezifischen Eingießkennlinie A, a pouring bucket specific Ausgießkennlinie B and, if necessary. Characteristic for the tilting movement of the mold C, hereinafter called Kokillenkennlinie C automatically generate the pouring of the ladle.

Fig. 2a shows the Eingießkennlinie A as a function of a cast-in volume of molten material Ve [liter] 1 over the time course t [sec]. The Eingießkennlinie A can be specified by a simulation software or manually. It describes the optimal course of the melt-filling process and provides as initial information the amount of waste Ve [liters] (melt stream or material flow) over time.

Fig. 2b shows a pouring characteristic B as a function of the poured out volume of molten material Va [liters] above the Gießlöffelneigung G [°]. Here, the accumulated melt volume is shown.

The pouring curve B can be created by means of two different methods. On the one hand, the knowledge of the geometry of the pouring ladle, for example of a 3D model, and the level of the molten material always lying horizontally enables the amount of molten material poured out to be calculated analytically as a function of the pouring ladle inclination G. On the other hand, there is the possibility in an automatic calibration process gradually tilt a fully filled ladle until completely drained. During the tilting movement, the amount of material poured out is measured by an electronic balance and the measured value is transmitted to the casting machine controller 32. The controller 32 logs the measured values and prepares the pouring characteristic curve B from the (accumulated) melt material volume, knowing the material-specific volume weight. This is a pouring bucket-specific pouring curve B. After changing the pouring ladle geometry, the pouring curve B must be determined again.

Finally, in Fig. 2c the Kokillenkennlinie C shown. In some casting processes, it is necessary, the mold 14 during the Eingießvorgangs z. B. to transfer from an inclined initial position in a vertical end position. The temporal course of the mold movement can be described in the Kokillenkennlinie as a function of the mold position K [deg °] over the time course t [sec].

The Kokillenkennlinie C can be determined either by a simulation software or - when the mold 14 is moved by the external control 33 - by recording the Kokillenbewegung using the coupled position controller 34 during a real Eingießvorgangs.

From the characteristics described above, namely Eingießkennlinie A, Ausgießkennlinie B and Kokillenkennlinie C can be the time course of the pouring automatically controlled. The following cases can be distinguished.

Fig. 3 shows a method wherein the mold 14 is controlled by the automatic casting machine 32. The Eingießkennlinie A and the Kokillenkennlinie C is based on a common time axis t [sec]. During the pouring process, the required casting mold position Kact is tapped off via the time Tact elapsed since the start of pouring with the aid of the mold characteristic curve C and the required pouring volume Vact from the pouring characteristic A. About the now known Eingießvolumen Vact the corresponding Gießlöffel tilt Gact is tapped in the Ausgießkennlinie B. The casting machine control 32 sets about the required inclination G, K for ladle and mold.

Fig. 4 shows a process flow, wherein the mold 14 is controlled by the independent external controller 33. In this case, it is assumed that the mold inclination K [° degrees] does not have to be set exactly, and the mold 14 is time-adjusted by an external controller 33. The current position of the mold 14 is detected by the position sensor 34 coupled thereto and transmitted to the casting machine control.

In this case, only the pouring characteristic A and the pouring characteristic B are used. The amount of volume Vact is taken from the pouring characteristic A via the continuous pouring time t [sec] and the pouring spoon position Gact is taken from the pouring characteristic B. The tracking of the casting machine or robot 16 is carried out by a kinematic transformation, which takes into account the current position of the mold 14 according to position sensor 34 (conveyor synchronization). Here, a spout 36 of the ladle 18 as TCP (Tool Center Point) without orientation tracked so that the spout 36 of the ladle 18 is always moved over a filling opening of the mold 14. The additionally required inclination G of the ladle 18 and thus the metering takes place via pouring ladle inclination Gact from the pouring characteristic D.

In both cases, the automation device 10 moves the ladle 18 so that the Gießlöffelposition is always tracked optimally to the filling opening of the mold. In each case, intermediate values are interpolated between the discretely tapped characteristic values and output by the automatic casting machine controller 32 to the mold drive 30 and / or the ladle drive 16, so that a continuous movement is generated.

There are two different ways to use automatic robot motion generation.

In the case of offline programming, an algorithm generates a movement program for the robot 16 from the above-mentioned information. In this case, intermediate positions are generated, each with a speed specification for each intermediate position. This method has the advantage that the generated program can be archived, manually changed and possibly transferred to other robots or casting machines.

In the online generation of motion, the required position of the ladle 18 is continuously determined from the given characteristic tables or characteristic values over the course of time and set on the robot or casting machine formats. The other axes 20, 22, 24, 26, 28 of the robot are tracked by a kinematic transformation so that the spout 36 of the ladle 18 performs a defined path movement (casting movement). An altered inclination K of the mold 14 is also included in the calculation of the robot movement.

The presented method offers the advantage that after replacing the ladle 18 or when using different ladle geometries, the controller, after automatic calibration, can automatically calculate a movement for the robot or automatic casting machine.

To the Kokillenkennlinie B is noted that these in the case of a non-tilted mold 14 is a straight line z. B. represents at a tilt angle of 0 °.

Claims (13)

1. Method for controlling a pouring-out movement of a casting ladle (18) for pouring out a molten material (12) such as molten metal into a casting mold (14) such as an ingot mold, where a pouring-in characteristic (A) specific to the casting mold as a function of a molten material volume (12) poured into the casting mold (14) over the time axis is preset and saved, wherein the method comprises the following method steps:

   - determination of a pouring-out characteristic (B) specific to the casting ladle as a function of a molten material volume (12) poured out of the casting ladle (18) over the tilt (G) of the casting ladle (18), and saving of at least one pouring-out characteristic (B),

   - automatic generation of the time axis of the pouring-out movement, where on the basis of the pouring-in characteristic (A) the necessary poured-in molten material volume is determined at any time and matched to an optimum poured-out molten material volume, to which an optimum tilt (G) of the casting ladle (18) is assigned at any time over the pouring-out characteristic (B).
2. Method according to Claim 1,
   wherein
   the pouring-in characteristic (A) is preset by a simulation software or manually as a function of the poured-in molten material volume (12) over the time axis, i.e. accumulated volume.
3. Method according to Claim 1 or 2,
   wherein
   the pouring-out characteristic (B) is empirically determined as a function of the poured-out molten material volume (12) over the casting ladle tilt, where in an automatic calibration operation a fully filled casting ladle is gradually tilted in individual steps until it is completely empty and the poured-out material quantity is weighed during the tilting movement by an electronic scale and the values measured are transmitted to a control unit (32), where the values measured are recorded in the control unit (32) and, with knowledge of the volumetric weight specific to the molten material, the pouring-out characteristic (B) over the (accumulated) material volume is obtained from them.
4. Method according to at least one of the preceding claims,
   wherein
   the pouring-out characteristic (B) is analytically calculated as a function of the poured-out molten material volume (12) over the casting ladle tilt, i.e. accumulated volume, with knowledge of the casting ladle geometry such as a 3D model and assuming a constantly horizontal molten material level.
5. Method according to at least one of the preceding claims,
   wherein
   after a change in the casting ladle geometry the pouring-out characteristic (B) is determined in accordance with the new casting ladle geometry.
6. Method according to at least one of the preceding claims,
   wherein
   the casting mold (14) is moved during the pouring-in operation from a, for example, tilted initial position into a, for example, vertical end position, where the time axis of the movement of the casting mold (14) is determined and saved in a characteristic (C) for the tilting movement (casting mold characteristic) as a function of the casting mold position over the time axis.
7. Method according to at least one of the preceding claims,
   wherein
   the casting mold characteristic (C) is determined by a simulation method.
8. Method according to at least one of the preceding claims,
   wherein
   the casting mold characteristic (C) is determined in particular in the case of external control by recording the casting mold movement with the aid of a connected position sensor (34) during an actual pouring-in operation.
9. Method according to at least one of the preceding claims,
   wherein
   both the pouring-out movement of the casting ladle (18) and the movement of the casting mold (14) are controlled by the same control unit (32), where the pouring-in characteristic (A) and the casting mold characteristic (C) are based on a common time axis, where proceeding from the pouring-in characteristic (A) the required casting mold position is determined from the casting mold characteristic (C) at any time during the pouring-in operation and proceeding from the optimum pouring-in volume the appropriate casting ladle tilt (G) is determined from the pouring-out characteristic (B), so that automatic control of the tilt of the casting ladle and of the casting mold is achieved.
10. Method according to at least one of the preceding claims,
    wherein
    the casting mold is controlled by an independent control unit (33), where the current position of the casting mold (14) is detected by a position sensor (34) connected thereto and transmitted to the control unit (32) of the casting ladle (18), where a poured-in molten material volume is obtained from the pouring-in characteristic (A) at any time and the associated casting ladle position is determined using the associated poured-out molten material volume by means of the pouring-out characteristic (B), where the tracking of the pouring-out movement of the casting ladle (18) is achieved by a kinematic transformation, where the current position of the casting ladle (14) is taken into account and where a tool center point is tracked such that a spout (36) of the casting ladle is always moved over a filling opening of the casting mold.
11. Method according to at least one of the preceding claims,
    wherein
    intermediate values are interpolated between discretely recorded characteristic values and are transmitted by the control unit (32) of the casting machine to a drive unit (30) of the casting mold (14) and/or to a casting ladle drive unit (20), so that a continuous movement is achieved.
12. Method according to at least one of the preceding claims,
    wherein
    an offline program generation is conducted, where a movement program for controlling the automation equipment is generated using an algorithm made up of information on the pouring-in characteristic (A), the pouring-out characteristic (B) and if required the casting mold characteristic (C).
13. Method according to at least one of the preceding claims,
    wherein
    an online movement generation is conducted, where the required position of the casting ladle (18) and/or the casting mold (14) is continuously determined from the given characteristic data or characteristic tables over the time axis and is immediately set by the control unit (32) of the automation equipment such as the casting machine.

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