METHOD FOR OPERATING A TREATMENT SYSTEM, TREATMENT SYSTEM, AND COMPUTER PROGRAM PRODUCT
A disclosed method for operating a treatment system and to a treatment system for electrophoretic dip coating, more particularly dip painting of a metal workpiece, more particularly of a vehicle body, in a dipping tank filled with a paint, wherein: a relative movement between the workpiece and a bus bar is carried out in the dipping tank; a voltage is applied to the workpiece; and, while the workpiece is in the effective range of at least one bus bar portion of the bus bar, electric current is fed to the workpiece from the at least one bus bar portion at least some of the time. Examples disclosed herein also relate to a treatment system and to a computer program product.
Examples disclosed herein relate to a method for operating a treatment plant for the electrophoretic dip painting of a metal workpiece, in particular a vehicle body, and to a treatment plant and a computer program product for carrying out the method.
BACKGROUNDFor the treatment of vehicle bodies, electrophoretic dip coating plants, for instance cathodic dip coating plants (CDC plants), are used, in which vehicle bodies are for example pretreated and/or painted by immersing them in dip baths in which paint is applied by means of electrophoresis. Electrophoretic deposition (EPD) is a widespread industrial process in which colloidal particles are deposited on a workpiece as an electrode under the influence of an electric field. The workpiece, for example a vehicle body, is immersed in an electrically conductive aqueous dipping paint and a DC voltage field is applied between the workpiece and a counterelectrode. The basic principle of electrodip painting consists in precipitating water-soluble binders on the surface of the workpiece connected as an electrode, and thus generating a continuous adhering paint film.
SUMMARYThe object of examples disclosed herein is to provide a method for operating a treatment plant for the electrophoretic dip coating of a metal workpiece, in particular a vehicle body, with which a better coating outcome can be achieved.
A further object consists in providing a treatment plant for electrophoretic dip coating, with which a better coating outcome can be achieved.
A further object consists in providing a computer program product with which the improved method can be carried out.
The objects are achieved by the features of the independent claims. Favorable configurations and advantages of examples disclosed herein may be found in the further claims, the description and the drawing.
The features mentioned individually in the patent claims may be combined with one another in a technologically expedient way and may be supplemented with explanatory facts from the description and by details from the figures, further embodiment variants of examples disclosed herein being presented.
A method is proposed for operating a treatment plant for electrophoretic dip coating, in particular dip painting, of a metal workpiece, in particular a vehicle body, in a dip bath filled with a paint, wherein a relative movement between the workpiece and a busbar is carried out in the dip bath, wherein an electrical voltage is applied to the workpiece, and wherein during the residence of the workpiece in the region of action of at least one busbar section of the busbar, an electrical current is at least temporarily supplied to the workpiece by the at least one busbar section.
The busbar is subdivided into individual busbar sections. On each busbar section, there is only ever one body, the length of each busbar section being less than the cycle distance of the successive bodies.
The current that flows to each busbar section is determined by a corresponding measuring device of a current supply unit. The workpiece is thus respectively arranged during the treatment only in the region of one busbar section. The busbar section may be longer or shorter than the workpiece, although it is expediently always shorter than the cycle distance between the workpieces.
The electrophoretic dip coating may be cathodic dip coating, in which the workpiece to be coated is connected as a cathode, or anodic dip coating, in which the workpiece to be coated is connected as an anode. During cathodic dip coating, the electrodes are filled with an anolyte as electrolyte fluid. During anodic dip coating, a separate anolyte system is not required as in the case of cathodic dip coating.
According to a favorable configuration of the method, regulation of the electrical current supplied to the workpiece may be carried out.
The electrical current for the current regulation may favorably be determined in each busbar section. The current regulation advantageously also allows simple specification of the desired coating current for each busbar section in the case of a current supply unit having modular rectifier modules. In this way, a better coating outcome may be achieved on the treated vehicle body.
According to a favorable configuration of the method, an electrical voltage may be applied to the workpiece by means of at least two electrically equivalent electrodes arranged in the dip bath in the region of action of the at least one busbar section, at least one rectifier module being connected to at least one of the electrodes, the current supplied to the workpiece forming a sum of the partial currents supplied by the individual rectifier modules, and a jointly regulated voltage setpoint value for the individual rectifier modules in the region of the workpiece being derived from a specified current setpoint value of the total current supplied to the workpiece and being specified to the individual rectifier modules.
During the electrophoretic dip coating, in particular dip painting, separate rectifier modules may respectively be expediently used for the current supply of the electrically equivalent electrodes. For supply with direct current, each of these rectifier modules may be electrically connected to an electrode or a group of electrodes, or a plurality of rectifier modules may be connected to a common electrode. By the modular structure, the voltage in the dip baths may be controlled or regulated very accurately.
Conventionally, in a body treatment section, which also corresponds to a busbar section, a plurality of electrodes are used, which may be arranged on both sides of the body in order to achieve a favorable treatment outcome. Typically, for flat or semi-round electrodes, from ten to sixteen electrodes may be provided. In the case of round electrodes, up to forty electrodes may be provided. Depending on the plant, more or fewer electrodes may of course be provided.
All the rectifier modules have a common pole, in the case of cathodic coating a common negative pole and in the case of anodic coating a common positive pole, which is connected to the bodies via a busbar having individual busbar sections.
Advantageously, a total current for the treatment of the body may thus be specified and regulated, which is made up of the sum of the individual partial current values of the at least one electrode and of their at least one supplying rectifier module. Particularly in the case of a plurality of rectifier modules, these may be controlled and/or regulated independently of one another. A current-led operating mode of the treatment unit may therefore advantageously be set up and implemented.
According to a favorable configuration of the method, an equal average voltage setpoint value may be specified for the rectifier modules and the voltage at the rectifier modules may be regulated so that the respectively specified total current setpoint value is reached.
The body is connected via the busbar to the common pole of the rectifier modules. The flow of current to the busbar is measured and corresponds to the current consumption of the body. The voltage regulation is switched over to current regulation. The average voltage of all the electrodes in the region of a body, without a run-in and run-out of the treatment, may for example be calculated in a PLC program of a control unit and assigned to the currently occupied busbar section.
During the current regulation, all the electrodes in the treatment region, including the run-in and run-out, receive the same voltage setpoint value.
The voltage is regulated so that the desired current setpoint value is reached.
The voltage may in this case vary between two setpoint values, namely a minimum voltage of the current regulation and a maximum voltage of the current regulation.
According to a favorable configuration of the method, in the case of a plurality of busbar sections following one another in the feed direction, PID regulation may be used for each busbar section, an average voltage of the respectively preceding busbar section being used as a start value for the PID regulation.
For each busbar section, separate PID regulation may thus be used and adapted according to requirements. As a start value for the regulation, the so-called Y offset value, an average voltage of the preceding busbar section may for example always be adjusted. It is therefore possible to ensure that the voltage is regulated constantly over the entire feed path and voltage jumps can be avoided.
When extracting the body from the paint of the dip bath, the current regulation is stopped and the electrodes keep their current voltage or a special extraction voltage is applied to them.
According to a favorable configuration of the method, a lower limit voltage and an upper limit voltage may be specified for the current regulation. The voltage may thus vary during the current regulation between two setpoint values, namely a minimum voltage of the current regulation and a maximum voltage of the current regulation. The voltage is specified and the partial current varies between 0 A and the maximum possible partial current per rectifier module. At the start of the coating, the voltage is increased via an adjustable ramp from 0 V to the desired setpoint value.
According to a favorable configuration of the method, the treatment of the workpiece may be carried out by means of charge quantity regulation, by regulating the current through the busbar section so that a specified charge setpoint value is reached.
Since the coating particles to be deposited, in particular paint particles, are applied by means of current transport, the total charge quantity represents a measure of the coating thickness of the coating material deposited, for example the paint deposited.
Advantageously, charge quantity regulation may ensure that the same charge quantity, i.e. amount of coating material from the paint, is always deposited for each body. A fluctuation in the paint temperature may for example be compensated for automatically by means of a charge quantity regulator, so that all the coated, in particular painted, vehicle bodies have a favorable coating outcome. In this way, the paint consumption and the coating quality may be optimized.
Beyond an adjustable time point of the coating, the charge quantity regulation may favorably be activated. For this purpose, for example, a charge quantity still required in order to reach the desired charge setpoint value and a residual coating time until the body starts to be extracted from the paint may be determined.
Advantageously, the charge quantity delivered by the rectifier modules may thus be kept constant during the coating. In this way, it is possible to ensure that a favorable coating outcome is guaranteed for all the bodies.
By the charge quantity regulation, the coating layer thickness may be optimized and kept constant. During the coating, material costs may therefore be saved and quality problems due to defective coating may be avoided.
According to a favorable configuration of the method, the current setpoint value for the charge quantity regulation is determined as a quotient of a charge quantity still required and a remaining treatment time.
As soon as the charge quantity regulation is active, the coating current is regulated. The current setpoint value is calculated continuously in order to reach the desired charge quantity:
-
- current setpoint value=Δ charge/Δ time,
- or with the desired units:
- current setpoint value [A]=charge quantity still required [Amin]×60/remaining coating time [s].
When the charge quantity regulation is active, the total current through the body is regulated to the calculated setpoint value. The voltage varies automatically between the adjustable minimum and maximum.
At the end of the coating, the charge reached is checked and compared with the specified limit values. If the limits are exceeded or fallen below, corresponding warning or fault messages may be output.
According to a favorable configuration of the method, the charge setpoint value may be adapted during the charge quantity regulation by means of adaptive regulation, the regulation being carried out as a function of treatment parameters. In particular, the regulation may be carried out as a function of at least one of the following parameters: paint parameters, in particular a binder content, pigment content, solvent content, pH, electrical conductivity of the electrolyte fluid, in particular the anolyte fluid, of the treatment process. During cathodic dip coating, the electrodes are filled with an anolyte. During anodic dip coating, acid is formed on the workpiece and a separate anolyte system is not required as in the case of cathodic dip coating.
In a further step, additional parameters may be taken into account. For this purpose, it is possible to use adaptive regulation which adapts automatically to the charge setpoint value of the body by means of external process parameters.
External parameters may inter alia be the paint parameters, for example binder content, pigment content, solvent content, pH, electrical conductivity and electrical conductivity in the electrolyte fluid, in particular the anolyte fluid. The relationship between these external parameters and the charge consumption may, for example, be stored in a mathematical formula in the PLC program of a control unit of the current supply unit.
If the pH of the paint lies above a setpoint value, for example, the charge setpoint value may be reduced by a particular charge value. If the pH of the paint lies below the setpoint value, on the other hand, the charge setpoint value may be increased by a particular amount.
According to a favorable configuration of the method, the charge setpoint value may be adapted during the charge quantity regulation as a function of a measured thickness, deposited from the paint on the workpiece, of a coating, in particular a coating that comprises paint particles.
Alternatively, the layer thickness of each body may be determined automatically by means of a layer thickness measurement after the electrophoretic coating. If the layer thickness is too high, the charge setpoint value is automatically reduced. If the layer thickness is too low, the charge setpoint value is automatically increased.
According to a favorable configuration of the method, at a start of the treatment of the workpiece, the treatment may be carried out by means of voltage regulation, by the setpoint voltage of the rectifier modules being increased to a voltage setpoint value via an adjustable voltage ramp.
In this way, the initial current, which rises very steeply at the start of the treatment, may be regulated favorably. With an increasing coating thickness, when the applied coating, in particular the paint, increasingly has an insulating effect, the current decreases. This value may be adjusted favorably by means of the voltage setpoint value.
According to a favorable configuration of the method, the treatment of the workpiece may be carried out over a specified time interval by means of voltage regulation, and may then be carried out by means of current regulation coupled with charge quantity regulation until a specified charge setpoint value is reached.
By means of such a regulation strategy, relatively rapid coating with a first coating thickness may advantageously be achieved by means of the voltage regulation, and this may then be operated further by means of the subsequent charge quantity regulation to the desired coating thickness.
According to a favorable configuration of the method, for controlled treatment of individual regions of the workpiece, the voltage setpoint values of the rectifier modules, which supply the electrodes that are assigned to these regions along the feed direction, may be adapted.
By the modular structure of the current supply unit with individual rectifier modules, individual body regions may be influenced in a controlled way. For this purpose, the voltage is increased or reduced in particular body regions in order to influence the layer thickness, for example with a voltage adaptation of at most +/−20%.
A body region may in this case expediently always be larger than the distance between two electrodes. Favorable for this operating mode are small electrodes, for example round electrodes and as many rectifier units as possible, so that the dip bath may be subdivided into many small voltage regions.
According to a further aspect of examples disclosed herein, a treatment plant is proposed for the electrophoretic dip coating, in particular dip painting, of a metal workpiece, in particular a vehicle body, in a dip bath filled with a paint, for carrying out a method as described above.
The treatment plant comprises at least: at least two electrically equivalent electrodes, which in particular are arranged on both sides of the workpiece, a busbar, which is arranged along a feed direction of the workpiece in the dip bath and is subdivided into individual busbar sections, the busbar being electrically connected to the workpiece, and at least one current supply unit having at least one rectifier module, one pole of the at least one rectifier module being electrically connected to at least one of the at least two equivalent electrodes, and the other pole of the at least one rectifier module being electrically connected to the busbar, and the at least two electrically equivalent electrodes applying an electrical voltage to the workpiece.
The busbar is subdivided into individual busbar sections. On each busbar section, there is respectively only one workpiece, for instance a body, during the treatment, the length of each busbar section being less than the cycle distance of successive bodies. The current that flows to each busbar is determined by means of a corresponding measuring device of a current supply unit. The workpiece is thus respectively arranged during the treatment only in the region of one busbar section, which is shorter than the cycle distance.
According to a favorable configuration of the treatment plant, the treatment plant may be configured for current regulation of the electrical current supplied to the workpiece.
The electrical current is determined in each busbar section for the current regulation. The current regulation advantageously allows simple specification of the desired coating current for each busbar section even in the case of a current supply unit having modular rectifier modules. An improved coating outcome on the vehicle body being treated may therefore be achieved.
According to a favorable configuration of the treatment plant, the at least one current supply unit may be configured to operate the rectifier modules respectively separately by means of voltage regulation.
The body is connected by means of the busbar to the common pole of the rectifier modules. The flow of current to the busbar is measured and corresponds to the current consumption of the body. The voltage regulation is switched over to current regulation. The average voltage of all the electrodes in the region of a body, without a run-in and run-out of the treatment, may for example be calculated in a PLC program of a control unit and assigned to the currently occupied busbar.
During the current regulation, all the electrodes in the treatment region, including the run-in and run-out, receive the same voltage setpoint value. The voltage is regulated so that the desired current setpoint value is reached.
The voltage may in this case vary between two setpoint values, namely a minimum voltage of the current regulation and a maximum voltage of the current regulation.
According to a favorable configuration of the treatment plant, the at least one current supply unit may be configured to operate the rectifier modules by means of current regulation coupled with charge quantity regulation by means of the current of a busbar section.
Since the coating particles are applied from the paint by means of current transport, the total charge quantity represents a measure of the coating thickness of the coating applied, in particular the coating comprising paint particles.
Advantageously, charge quantity regulation may ensure that the same charge quantity is always deposited for each body. A fluctuation in the paint temperature may for example be compensated for automatically by means of a charge quantity regulator, so that all the coated vehicle bodies have a favorable coating outcome. In this way, the paint consumption and the coating quality may be optimized.
According to a favorable configuration of the treatment plant, the at least one current supply unit may be configured to operate the rectifier modules in a first time interval by means of voltage regulation and in a second time interval by means of current regulation coupled with charge quantity regulation until a specified charge setpoint value is reached.
Beyond an adjustable time point of the coating, the charge quantity regulation may favorably be activated. For this purpose, for example, a charge quantity still required in order to reach the desired charge setpoint value and a residual coating time until the body starts to be extracted from the paint of the dip bath may be determined.
Advantageously, the charge quantity delivered by the rectifier modules may thus be kept constant during the coating. In this way, it is possible to ensure that a favorable coating outcome is guaranteed for all the bodies.
By the charge quantity regulation, the layer thickness deposited may be optimized and kept constant. During the coating, material costs may therefore be saved and quality problems due to defective coating may be avoided.
By means of such a regulation strategy, relatively rapid coating with a first coating thickness may advantageously be achieved by means of the voltage regulation, and this may then be operated further by means of the subsequent charge quantity regulation to the desired coating thickness.
According to a further aspect of examples disclosed herein, a computer program product is proposed for carrying out the method according to examples disclosed herein, in order to operate a treatment plant for the electrophoretic dip coating, in particular dip painting, of a metal workpiece, in particular a vehicle body, in a dip bath filled with a paint, in which the workpiece is moved in a feed direction along a busbar and electrodes supplied by rectifier modules. The computer program product comprises at least one computer-readable storage medium having program code instructions stored thereon, wherein the effect of the program code instructions which can be executed by a data processing system is that, during the residence of the workpiece in the region of action of at least one busbar section of the busbar, an electrical current is at least temporarily supplied to the workpiece by the at least one busbar section.
According to a favorable configuration of the computer program product, the effect of the program code instructions which can be executed by the data processing system may be that, the treatment of the workpiece is carried out at least temporarily by means of current regulation, by a current setpoint value being specified for a busbar section of the busbar, an equal regulated voltage setpoint value being specified for the rectifier modules and the voltage being regulated so that the specified current setpoint value is reached; and/or that the treatment of the workpiece is carried out by means of charge quantity regulation, by the current through the busbar section being regulated in order to reach a specified charge setpoint value; and/or that the treatment of the workpiece is carried out over a first time interval by means of voltage regulation and in a second time interval by means of current regulation coupled with charge quantity regulation until a specified charge setpoint value is reached; and/or that for controlled treatment of individual regions of the workpiece, voltage setpoint values of the rectifier modules, which supply the electrodes in these regions, are adapted.
Advantageously, a total current for the treatment of the body may thus be specified and regulated, which is made up of the sum of the individual partial current values of the individual electrodes and of their supplying rectifier modules, controlled independently of one another.
A current-led operating mode of the treatment unit may therefore advantageously be set and implemented.
Advantageously, the charge quantity delivered by the rectifier modules may thus be kept constant during the coating. In this way, it is possible to ensure that a favorable coating outcome is guaranteed for all the bodies.
By the charge quantity regulation, the layer thickness deposited may be optimized and kept constant. During the coating, material costs may therefore be saved and quality problems due to defective coating may be avoided.
Further advantages may be found from the following description of the drawing. Exemplary embodiments of examples disclosed herein are represented in the drawings. The drawings, the description and the claims contain numerous features in combination. A person skilled in the art will also expediently consider the features individually and combine them to form suitable further combinations.
By way of example:
The figures merely show examples and are not to be interpreted as restrictive.
Before examples disclosed herein are described in detail, it should be pointed out that it is not restricted to the respective component parts of the device and the respective method steps, since these component parts and methods may vary. The terms used herein are merely intended to describe particular embodiments and are not used restrictively. Furthermore, when the singular or indefinite article is used in the description or in the claims, this also relates to the plurality of these elements so long as the contrary is not clearly disclosed in the overall context.
In what follows, direction terminology with terms such as “left”, “right”, “up”, “down”, “before”, “behind”, “after” and the like is used only for better understanding of the figures and is in no case intended to constitute a restriction of generality. The components and elements represented, their layout and their use may vary in the sense of the considerations of a person skilled in the art and be adapted to the respective applications.
The treatment plant 100 for the electrophoretic, for example cathodic, dip painting of a metal workpiece 40, in particular a vehicle body, in a dip bath filled with a paint comprises a multiplicity of electrodes 32, which in particular are arranged on both sides of the workpiece 40. A relative movement between the workpiece 40 and a busbar 21 is carried out in the dip bath 30, i.e. with the busbar 21 stationary the workpiece is moved in the dip bath 30 between the likewise stationary electrodes 32 in the feed direction 42.
During cathodic dip coating, the workpiece 40 to be coated is connected as a cathode and the electrodes are filled with an anolyte.
The treatment plant 100 furthermore comprises a busbar 21, which is arranged along a feed direction 42 of the workpiece 40 in the dip bath 30 and is subdivided into individual busbar sections 22, 24, 26. The busbar sections 22, 24, 26 have a length 46, which may be adapted to a length 44 of the workpiece 40 in the feed direction 42. The busbar sections 22, 24, 26 may have the same length as, but may also be longer or shorter than the workpiece 40, although expediently they are always shorter than the cycle distance.
The busbar 21 is electrically connected to the workpiece 40, for example by means of power cables. This, however, is not represented in
On each busbar section 22, 24, 26 there is always only one body, the length of each busbar section 22, 24, 26 being less than the cycle distance of the successive bodies. The current that flows to each busbar section 22, 24, 26 is determined by a corresponding measuring device 18 of a current supply unit 10. The workpiece 40 is thus respectively arranged during the treatment only in the region of one busbar section 22, 24, 26, which corresponds for example to a length of the workpiece 40. The electrical current is determined in each busbar section 22, 24, 26 for the current regulation.
The current regulation advantageously allows simple specification of the desired coating current for each busbar section 22, 24, 26 even in the case of a current supply unit 10 having modular rectifier modules 12. An improved coating outcome on the vehicle body being treated may therefore be achieved.
During the electrophoretic dip painting, separate rectifier modules 12 may respectively expediently be used for the current supply of the electrodes 32. Each of these rectifier modules 12 supplies an electrode 32 or a group of electrodes 32 with direct current. By the modular structure, the voltage in the dip baths 30 may be controlled very accurately. Alternatively, a plurality of rectifier modules 12 may also be provided for an electrode 32.
Conventionally, in a body treatment section, which also corresponds to a busbar section 22, 24, 26, from ten to sixteen flat or semi-round electrodes 32 are used, which may be arranged on both sides of the body in order to achieve a favorable treatment outcome. In the case of round electrodes 32, even more, for instance up to forty, may be provided. More or fewer electrodes may respectively be provided.
All the rectifier modules 12 have a common pole 16, which is connected to the bodies via a busbar 21 having individual busbar sections 22, 24, 26. In the case of cathodic dip coating, the common pole 16 is the negative pole, while in the case of an anodic dip coating the common pole 16 would be the positive pole.
Advantageously, a total current for the treatment of the body may thus be specified and regulated, which is made up of the sum of the individual partial current values 75 of the individual electrodes 32 and of their supplying rectifier modules 12, which may be controlled independently of one another. A current-led operating mode of the treatment unit 100 may therefore advantageously be set and implemented.
In the exemplary embodiment of
The workpiece 40 is respectively arranged only in the region of one busbar section 22, 24, 26 during the treatment.
The treatment plant 100 is configured for current regulation of the electrical current supplied to the workpiece 40. The electrical current may be determined separately in each busbar section 22, 24, 26 by means of current measuring units 18. The negative pole 16 of the rectifier modules 12 is electrically connected to the busbar sections 22, 24, 26 via the current measuring units 18, and optionally via a coupling thyristor 28.
Via the current supply units 10, the rectifier modules 12 may respectively be operated separately by means of voltage regulation.
The rectifier modules 12 may be operated by means of current regulation coupled with charge quantity regulation via the current of a busbar section 22, 24, 26.
The current supply units 10 are configured to operate the rectifier modules 12 in a first time interval by means of voltage regulation and in a second time interval by means of current regulation coupled with charge quantity regulation until a specified charge setpoint value 80 is reached.
According to the method according to examples disclosed herein, during the residence of the workpiece 40 in the region of action of at least one busbar section 22, 24, 26 of the busbar 21, regulation of the electrical current supplied to the workpiece 40 by the at least one busbar section 22, 24, 26 is at least temporarily carried out.
The current supplied to the workpiece 40 forms the sum of the partial currents supplied by the individual rectifier modules 12, a voltage setpoint value 71 for the rectifier modules 12 in the region of the workpiece 40 to be coated being derived from a specified current setpoint value of the total current supplied to the workpiece 40 and specified to the individual rectifier modules 12.
An equal average voltage setpoint value 71 (represented in
In the case of a plurality of busbar sections 22, 24, 26 following one another in the feed direction 42, PID regulation may for example be used for each busbar section 22, 24, 26, wherein an average voltage of the respectively preceding busbar section 22, 24, 26 may be used as a start value for the PID regulation.
A lower limit voltage and an upper limit voltage may be expediently specified for the current regulation.
For each busbar section 22, 24, 26, separate PID regulation may thus be used. As a start value for the regulation, the so-called Y offset value, an average voltage of the preceding busbar section 22, 24, 26 may for example always be adjusted. It is therefore possible to ensure that the voltage is regulated constantly over the entire feed path and no voltage jumps occur.
When extracting the body from the paint, the current regulation is stopped and the electrodes 32 keep their current voltage or a special extraction voltage is applied to them.
The body is connected via the busbar 21 to the common negative pole 16 of the rectifier modules 12. The flow of current to the busbar 21 is measured and corresponds to the current consumption of the body. The voltage regulation is switched over to current regulation. The average voltage of all the electrodes 32 in the region of a body, without a run-in and run-out of the treatment, may for example be calculated in a PLC program of a control unit and assigned to the currently occupied busbar section 22, 24, 26.
During the current regulation, all the electrodes 32 in the treatment region, including the run-in and run-out, receive the same voltage setpoint value 71. The voltage is regulated so that the desired current setpoint value is reached.
The voltage 70 may in this case vary between two setpoint values, namely a minimum voltage of the current regulation and a maximum voltage of the current regulation.
A run-in region 52 and a run-out region 50 and as well as a body region 54 of the treatment plant are marked.
During the current regulation with voltage and current values respectively for an electrode pair of electrodes 32 arranged on both sides of the workpiece 40, all the electrodes 32 receive the same voltage value 70 as the setpoint voltage. The voltage 70 is in this case regulated so that the desired total current 74 on the busbar 21 is obtained. In the exemplary embodiment represented, a current setpoint value of 700 A is specified, which is given by the total of the individual current values 75 of the electrodes 32.
For controlled treatment of individual regions 56, 58, 60 of the workpiece 40, the voltage setpoint values 71 of the rectifier modules 12, which supply the electrodes 32 that are assigned to these regions 56, 58, 60 along the feed direction 42, may be adapted.
By the modular construction of the current supply unit 10 with individual rectifier modules 12, individual body regions 56, 58, 60 may be influenced in a controlled way. For this purpose, the voltage in particular body regions 56, 58, 60 is increased or decreased in order to influence the layer thickness, for example with a voltage adaptation of at most +/−20%.
A body region 56, 58, 60 may in this case expediently be always greater than the distance between two electrodes. Small electrodes 32, for example round electrodes, and as many rectifier modules 12 as possible are favorable for this operating mode, so that the dip bath 30 can be subdivided into many small voltage regions.
For this purpose, the voltage setpoint values 71 of electrodes 32 assigned to the regions 56, 58, 60 may be corrected with correction values 73 for the voltage adaptation, with which values adapted voltage setpoint values 72 are then determined. With these adapted voltage setpoint values 72, the treatment of the workpiece 40 may be continued and individual regions 56, 58, 60 may be treated in a controlled way with higher or lower deposition rates of the coating to be applied.
In
This is based on the same correction values 73 as in the example in
The voltage setpoint values 71 represented in
Advantageously, charge quantity regulation may ensure that the same charge quantity 76 is always deposited for each body. A fluctuation in the paint temperature may, for example, be compensated for automatically by means of a charge quantity regulator, so that all the painted vehicle bodies have a favorable coating outcome. In this way, the paint consumption and the coating quality may be optimized.
Beyond an adjustable time point 82 of the coating, the charge quantity regulation may favorably be activated. For this purpose, for example, a charge quantity ΔQ still required in order to reach the desired charge setpoint value 80 and a residual coating time Δt until the body starts to be extracted from the paint may be determined.
Advantageously, the charge quantity 76 delivered by the rectifier modules 12 may thus be kept constant during the coating. In this way, it is possible to ensure that a favorable coating outcome is guaranteed for all the bodies.
By the charge quantity regulation, the coating layer thickness may be optimized and kept constant. During the coating, material costs may therefore be saved and quality problems due to defective coating may be avoided.
According to a favorable configuration of the method, the current setpoint value for the charge quantity regulation is determined as a quotient of a charge quantity ΔQ still required and a remaining treatment time Δt.
The voltage 70, the current 74 resulting therefrom and the charge 76 are plotted as a function of time 84 in
Initially, the rectifier modules 12 and the electrodes 32 operated by the latter are operated with voltage regulation until a time point 82, at which the charge regulation begins.
At a start of the treatment of the workpiece 40, the treatment is carried out by means of voltage regulation, by the setpoint voltage of the rectifier modules 12 being increased via an adjustable voltage ramp to a voltage setpoint value 71.
The treatment of the workpiece 40 is carried out for a specified time interval by means of voltage regulation, and is then carried out by means of current regulation coupled with charge quantity regulation until a specified charge setpoint value 80 is reached.
In the voltage-regulated phase, the current 74 initially increases steeply, while the voltage 70 increases moderately. The current 74 then decreases to a medium value since the insulating effect of the paint deposited on the workpiece 40 has an effect.
Beyond the time point 82 at which the charge regulation is switched, the rectifier modules 12 are operated with current regulation according to the determined charge quantity ΔQ still remaining for the charge setpoint value 80, which is intended to be achieved in the time Δt still remaining. The charge 76 therefore increases linearly on this section as far as the charge setpoint value 80.
The treatment of the workpiece 40 is carried out by means of charge quantity regulation, by regulating the current through the busbar section 22, 24, 26 so that a specified charge setpoint value 80 is reached.
The charge setpoint value for the charge quantity regulation is determined as a quotient of a charge quantity still required and a remaining treatment time.
The charge setpoint value 80 during the charge quantity regulation may advantageously be adapted by means of adaptive regulation. The regulation may, for example, be carried out as a function of treatment parameters. In particular, the regulation may be carried out as a function of at least one of the following parameters: paint parameters, in particular a solvent content, pH, electrical conductivity and the electrical conductivity of the electrolyte fluid, in particular the anolyte fluid, of the treatment process.
The charge setpoint value 80 during the charge quantity regulation may, for example, also be adapted as a function of a measured thickness, deposited on the workpiece 40 from the paint, of a coating, in particular a coating comprising paint particles.
Advantageously, the current supply units 10 of the treatment plant 100 are connected to a computer which implements a computer program product for carrying out the method according to examples disclosed herein for operating the treatment plant 100 for electrophoretic, for example cathodic, dip painting of a metal workpiece 40, in particular a vehicle body, in a dip bath 30 filled with a paint, in which the workpiece 40 is moved in a feed direction 42 along a busbar 21 and electrodes 32 supplied by rectifier modules 12, comprising at least one computer-readable storage medium having program code instructions stored thereon, wherein the effect of the program code instructions which can be executed by a data processing system is that, during the residence of the workpiece 40 in the region of action of at least one busbar section 22, 24, 26 of the busbar 21, an electrical current is at least temporarily supplied to the workpiece 40 by the at least one busbar section 22, 24, 26.
The program code instructions may furthermore advantageously have the effect that the treatment of the workpiece 40 is carried out at least temporarily by means of current regulation, by a current setpoint value being specified fora busbar section 22, 24, 26 of the busbar 21, an equal average voltage setpoint value 71 being specified for the rectifier modules 12 and the voltage being regulated so that the specified current threshold value is reached; and/or that the treatment of the workpiece 40 is carried out by means of charge quantity regulation, by the current through the busbar section 22, 24, 26 being regulated in order to reach a specified charge setpoint value 80; and/or that the treatment of the workpiece 40 is carried out over a first time interval by means of voltage regulation and in a second time interval by means of current regulation coupled with charge quantity regulation until a specified charge setpoint value 80 is reached; and/or that for controlled treatment of individual regions 56, 58, 60 of the workpiece 40, voltage setpoint values 71 of the rectifier modules 12, which supply the electrodes 32 in these regions 56, 58, 60, are adapted.
REFERENCE SIGNS
-
- 10 current supply unit
- 12 rectifier module
- 14 positive pole
- 16 negative pole
- 18 current measuring unit
- 20 connecting line
- 21 busbar
- 22 busbar section
- 24 busbar section
- 26 busbar section
- 28 coupling thyristor
- 30 dip bath
- 32 electrode
- 34 transport unit
- 36 carrier
- 40 workpiece
- 42 feed direction
- 44 length of workpiece
- 46 length of busbar
- 50 run-in
- 52 run-out
- 54 body region
- 56 region 1
- 58 region 2
- 60 region 3
- 70 voltage
- 71 voltage setpoint value
- 72 adapted voltage setpoint value
- 73 correction value
- 74 current
- 75 partial current
- 76 charge
- 80 charge setpoint value
- 82 start of charge quantity regulation
- 84 time
- 100 treatment plant
Claims
1. A method for operating a treatment plant for electrophoretic dip coating, in particular dip painting, of a metal workpiece, in particular a vehicle body, in a dip bath having a paint, the method comprising:
- causing relative movement between workpiece and a busbar in the dip bath,
- applying an electrical voltage to the workpiece, and
- supplying an electrical current to the workpiece by at least one busbar section during residence of the workpiece in the region of action of the at least one busbar section of the busbar.
2. The method as defined in claim 1, further including regulating the electrical current supplied to the workpiece.
3. The method as defined in claim 1, wherein the electrical voltage is applied to the workpiece by at least two electrically equivalent electrodes arranged in the dip bath in the region of action of the at least one busbar section,
- wherein at least one rectifier module is connected to at least one of the electrodes;
- wherein the current supplied to the workpiece corresponds to a sum of partial current supplied by the individual rectifier modules, and
- wherein a voltage setpoint value for the rectifier modules in the region of the workpiece to be coated is derived from a specified current setpoint value of the total current supplied to the workpiece and is specified to the individual rectifier modules.
4. The method as defined claim 3, wherein an equal average voltage setpoint value is specified for the rectifier modules and the voltage at the rectifier modules is regulated so that ai specified total current is reached.
5. The method as defined in claim 4, wherein for a plurality of busbar sections following one another in a feed direction, PID regulation is used for each busbar section, an average voltage of the respectively preceding busbar section being used as a start value for the PID regulation.
6. The method as defined in claim 4, wherein a lower limit voltage and an upper limit voltage are specified for the current regulation.
7. The method as defined in claim 1, wherein the treatment of the workpiece is carried out by charge quantity regulation, by regulating the current through the busbar section so that a specified charge setpoint value is reached.
8. The method as defined in claim 7, wherein the current setpoint value for the charge quantity regulation is determined as a quotient of a charge quantity still required and a remaining treatment time.
9. The method as defined in claim 7, wherein the charge setpoint value is adapted during the charge quantity regulation by adaptive regulation, the regulation being carried out as a function of treatment parameters, the regulation in particular being carried out as a function of at least one of the following parameters: paint parameters, in particular binder content of the paint, pigment content, solvent content, pH, conductivity or electrical conductivity of an electrolyte fluid, in particular an anolyte fluid, of the treatment.
10. The method as defined in claim 7, wherein the charge setpoint value is adapted during the charge quantity regulation as a function of a measured thickness, deposited from the paint on the workpiece, of a coating, in particular a coating that includes paint particles.
11. The method as defined in claim 1, wherein at a start of the treatment of the workpiece, the treatment is carried out by voltage regulation, by a setpoint voltage of rectifier modules being increased to a voltage setpoint value via an adjustable voltage ramp.
12. The method as defined in claim 1, wherein the treatment of the workpiece is carried out over a specified time interval by voltage regulation, and is then carried out by current regulation coupled with charge quantity regulation until a specified charge setpoint value is reached.
13. The method as defined in claim 1, wherein for controlled treatment of individual regions of the workpiece, voltage setpoint values of rectifier modules, which supply electrodes that are assigned to these regions along a feed direction, are adapted.
14. A treatment plant for the electrophoretic dip coating, in particular dip painting, of a metal workpiece, in particular a vehicle body, in a dip bath filled with a paint, for carrying out a method as defined in claim 1, comprising at least
- at least two electrically equivalent electrodes, which in particular are arranged on both sides of the workpiece,
- a busbar, which is arranged along a feed direction of the workpiece in the dip bath and is subdivided into individual busbar sections, the busbar being electrically connected to the workpiece, and
- at least one current supply unit having at least one rectifier module, one pole of the at least one rectifier module being electrically connected to at least one of the at least two equivalent electrodes, and the other pole of the at least one rectifier module being electrically connected to the busbar, and the at least two equivalent electrodes applying an electrical voltage to the workpiece (40).
15. The treatment plant as defined in claim 14, wherein the treatment plant is configured for current regulation of the electrical current supplied to the workpiece.
16. The treatment plant as defined in claim 14, wherein the at least one current supply unit is configured to operate the rectifier modules respectively separately by voltage regulation.
17. The treatment plant as defined in claim 14, wherein the at least one current supply unit is configured to operate the rectifier modules by current regulation coupled with charge quantity regulation by the current of a busbar section.
18. The treatment plant as defined in claim 14, wherein the at least one current supply unit is configured to operate the rectifier modules in a first time interval by voltage regulation and in a second time interval by current regulation coupled with charge quantity regulation until a specified charge setpoint value is reached.
19. A computer program product for carrying out the method according to claim 1, in order to operate a treatment plant for the electrophoretic dip coating, in particular dip painting, of a metal workpiece, in particular a vehicle body, in a dip bath filled with a paint, in which the workpiece is moved in a feed direction along a busbar and electrodes supplied by rectifier modules,
- comprising at least one computer-readable storage medium having program code instructions stored thereon, wherein an effect of the program code instructions which can be executed by a data processing system is that, during the residence of the workpiece in the region of action of at least one busbar section of the busbar, an electrical current is at least temporarily supplied to the workpiece by the at least one busbar section.
20. The computer program product as defined in claim 19, wherein the effect of the program code instructions which can be executed by the data processing system is that,
- the treatment of the workpiece is carried out at least temporarily by current regulation, by a current setpoint value being specified for a busbar section of the busbar, an equal average voltage setpoint value being specified for the rectifier modules and the voltage being regulated so that a specified current threshold value is reached, and/or that the treatment of the workpiece is carried out by charge quantity regulation, by the current through the busbar section being supplied to the workpiece to reach a specified charge setpoint value; and/or that the treatment of the workpiece is carried out over a first time interval by voltage regulation and in a second time interval by current regulation coupled with charge quantity regulation until a specified charge setpoint value is reached, and/or that for controlled treatment of individual regions of the workpiece, voltage setpoint values of the rectifier modules, which supply the electrodes in these regions, are adapted.
Type: Application
Filed: Apr 29, 2022
Publication Date: May 2, 2024
Inventors: Markus RAMSAIER (Ludwigsburg), Michael DIETERICH (Asperg), Sebastian BROSI (Großbottwar), Jens HOFMANN (Stuttgart)
Application Number: 18/557,388
