EP3048181B1 - Installation and method for producing a metallic coating on a workpiece - Google Patents

Description

The invention relates to a plant for the metallic coating of a workpiece with a coating device, which has a movable coating lance, by which a metal plasma jet for forming a coating of metal articles can be generated, according to the preamble of claim 1.

The invention further relates to a method for the metallic coating of a workpiece with a movable coating lance, by means of which a metal plasma jet is generated, wherein a metallic coating of metal particles is formed on the workpiece, according to the preamble of claim 12.

In particular, in engine construction, it is necessary to provide the running surfaces of cylinder bores with a special metallic coating, so that adequate friction and lubrication conditions between the cylinder surface and a cylinder piston are ensured. This is especially true when both the engine housing and the cylinder piston are made of the same metal, such as aluminum.

From the generic DE 199 34 991 A1 or the WO 2004/005575 A2 It is known to apply directly to a bore wall a metal coating through a coating lance, with which a metal plasma jet is generated. In this way, very thin-walled and very stable metal coatings can be formed on bore walls.

In this case, the coating lance is moved into a cylinder bore of an engine block, wherein the generated metal plasma jet is directed to the bore wall.

Due to a certain scattering of the metal plasma jet, not all metal particles reach the bore wall. These unapplied metal particles are referred to as overspray and can lead to undesirable spurious coatings in the engine block or on the coater.

From the DE 199 34 991 A1 shows a plant for the metallic coating of a workpiece, in which various processing stations are arranged linearly along a belt conveyor. As a final processing station, the coating of the workpiece is provided. Subsequently, the workpiece is removed directly from the plant.

The information leaflet by oerlikon metco (issue 5 - October 2014) on "Athmospheric Plasma Spray Solutions" discloses a device for coating cylinder casings according to the atmospheric plasma spray method. For this purpose, a plasma lance is attached to a robot arm. Here, a processing station for processing cylinder housings is provided, which is surrounded by a housing. For real-time monitoring of the plasma spray, a number of parameters can be monitored during coating.

The invention has for its object to provide a system and a method for the metallic coating of a workpiece, which allow a particularly efficient and accurate application of the coating.

The object is achieved according to the invention on the one hand by a system with the features of claim 1 and on the other hand by a method having the features of claim 12. Preferred embodiments of the invention are specified in the respective dependent claims.

The plant according to the invention is characterized in that the coating device with the coating lance and a measuring device for measuring the Coating thickness are formed integrated in the system and that the coating device with the coating lance and the measuring device are enclosed by a housing.

A basic idea of the invention can be seen in the fact that the processes of coating and measuring of the applied coating are brought close together, so that overall immediate and therefore more accurate statements about the coating that has taken place can be made. This is achieved in that the coating device and the measuring device are arranged in the same system and in particular on the same machine bed and are enclosed by a common housing. The determined measurement data of the measuring device, in particular the layer thickness and the contour of the applied coating allow very accurate conclusions about the coating process. This can be used in the control of the coating apparatus for coating a subsequent workpiece can be used in a timely manner to prevent any possible incorrect coatings.

The invention thus takes a different route in comparison with known systems in which, due to the risk of undesired deposits by the metal overspray in the coating device, the measuring device has been significantly spaced and arranged separately from the coating device. With reduction of a necessary travel of the coated workpiece from the coating device to the measuring device increases according to a finding of the invention, the positioning and thus measurement inaccuracy.

According to the invention, it is provided that the housing has a loading station for feeding and discharging the workpiece, that the measuring device is arranged in the loading station and that the measuring device is additionally designed for measuring the workpiece before coating. In this arrangement variant, the workpiece thus passes through twice the charging station of the system, namely during feeding and during removal of the workpiece. In the arrangement of the measuring device in the charging station, the measuring device can thus fulfill a dual function, namely the measurement of the workpiece before coating and then measuring the workpiece with the coating. In particular, in the case of a coating of bores in a workpiece, a measurement by recording the bore contour by the measuring device can thus take place with particularly great accuracy. Because the measuring device detects the surface of the uncoated hole and then the surface contour of the coated bore. By a corresponding comparison of the measurement results, a particularly accurate determination of the layer thickness and the layer thickness profile can thus be determined.

According to another embodiment variant of the invention, it is advantageous that the measuring device has a movable measuring sensor, which can be moved between a calibration station and a workpiece holder in the loading station. The measuring device may in particular have an optical measuring sensor, which preferably cooperates with a laser device. These basically known measuring devices allow an exact detection of a surface contour. By a corresponding adjustment and calibration of the measuring device At the same time a diameter of a bore and in particular a diameter profile over the axial length of the bore can be detected. Preferably, the workpiece remains from the time of feeding to removal in the system on a workpiece holder, in particular a workpiece holder or a workpiece pallet, so that a positioning of the workpiece with high repeatability in the repeated measurement is possible.

According to the invention, it is provided that the coating device is arranged in a processing station, which is separated from the loading station, and that a cleaning station for cleaning the coating lance is arranged in the processing station. By separating the processing station, in which the coating process with the metal plasma jet takes place, and the charging station, in which the surveying is performed, in particular by a partition wall, the coating and measuring can be carried out spatially close, but without undesirable interactions with each other. An improvement in the accuracy of the order is further increased according to a variant of the invention in that a cleaning station is provided in the processing station, with which at certain times the coating lance is cleaned of accumulated metal particles. These unwanted deposits result from the metal overspray during coating in the processing station.

A further improvement can still be achieved by arranging in the processing station a test station for testing the metal plasma jet generated by the coating lance. In this test station, the beam pattern can be detected, measured and compared with a desired beam pattern, for example, by means of a camera. If deviations are detected to an excessive extent, a maintenance, in particular a cleaning of the coating lance in the cleaning station can be initiated by a controller. The test results can also be used directly for controlling the coating apparatus and in particular for forming the metal plasma jet.

A further improvement is achieved according to another embodiment of the invention in that a suction device is provided, through which for sucking air from the coating device of the calibration, the Test station and / or the cleaning station is formed. In particular in the coating apparatus, metal overspray can thus be removed from the processing station during the coating with the ambient air. Preferably, the plant with the suction device is designed so that in the processing station with the coating device relative to the environment and in particular the charging station with the measuring device, a certain negative pressure is set. With this negative pressure, a transfer of overspray from the processing station into the charging station with the measuring device can be counteracted. This prevents impairment of the measuring device by unwanted metal accumulation by overspray.

Another positive influence on the measurement accuracy of the system is achieved according to a development of the invention in that at least one workpiece holder is provided, in which a workpiece is received and tensioned in a defined position, and that the workpiece holder between the loading station and the processing station is movable , The workpiece is thus continuously in a workpiece holder when conveying through the system. As a result, the measurement data allow particularly accurate conclusions about the manner of the coating, so that they can be used according to the control of the coating device during coating.

According to the invention, it is provided that the processing station and the charging station are separated by a partition and that the partition has at least one closable passage. The partition, which divides the housing into two sections, hermetically separates the processing station and the charging station. This serves in particular to prevent a transfer of overspray from the processing station to the charging station with the measuring device and thus unwanted deposits of metal particles on the sensitive measuring device. For the passage of the workpiece from the loading station in the processing station at least one passage in the partition wall is provided, which is closable. The passage is opened in each case only for a brief moment for the passage of the workpiece from one station to the other.

It is particularly preferred according to a development of the invention that the passage is closed by a closure element, which releases the passage for the passage of the workpiece. The closure element may be a door and in particular a displaceable or pivotable closure plate. By a servomotor, a control cylinder or by an adjustment mechanism while the closure element is moved to a release position when the workpiece reaches the passage. After passage of the workpiece, the closure element is moved back into the closed position in which the passage is sealed.

A particularly efficient operation of the system according to the invention results according to a further preferred embodiment in that the at least one workpiece holder can be moved by means of a conveyor which has an annular circulation path. The conveyor can be any circulation conveyor, such as a chain conveyor, a belt conveyor or a similar conveyor with endless circulating conveyor element.

It is particularly advantageous that the conveyor is designed as a turntable, which is arranged horizontally movable. The turntable can have space for preferably two or more workpiece holders.

In particular, in the case of a circulation conveyor, it is expedient according to a development of the invention that two passages, each with a closure element, are provided in the dividing wall. A passage serves for the passage of the workpiece from the loading station into the processing station, while the second passage serves in a reverse manner for the passage of the workpiece from the processing station into the loading station.

A further preferred embodiment of the invention is that the conveyor is formed horizontally encircling and that the workpiece holder on the conveyor adjustable, in particular pivotable about a horizontal pivot axis, is mounted. In this case, the workpiece holder, in which the workpiece is held and clamped, arranged horizontally in a basic orientation. When machining engine blocks with, for example, a V or W arrangement of the cylinder bores, the workpieces can each have a horizontal position Swiveling pivot axis and be adjusted that the respective cylinder bores to be machined are aligned vertically. This allows both a precise coating by the vertically movable coating lance and an accurate measurement by the measuring device, in which the measuring sensor is also mounted vertically movable.

The method according to the invention is characterized in that the formation of the coating and the measurement of the coating thickness are carried out integrated in a system which has been described above. With this method according to the invention, the advantages described above can be achieved when coating a workpiece, in particular when coating bores in a workpiece.

The invention is preferably provided for coating bores in workpieces, in particular cylinder bores in engine blocks. Other applications are also possible.

Fig. 1:

eine schematische Seitenansicht einer erfindungsgemäßen Anlage;

Fig. 2:

eine um 90° geklappte Seitenansicht der Anlage von Fig. 1 in stark schematisierter Form;

Fig. 3:

eine Draufsicht der Anlage gemäß den Figuren 1 und 2;

Fig. 4:

eine schematische perspektivische Ansicht der Anlage gemäß den Figuren 1 bis 3, jedoch ohne Gehäuse.

The invention will be further described below with reference to a preferred embodiment, which is shown schematically in the accompanying drawings. In the drawings show:

Fig. 1:

a schematic side view of a system according to the invention;

Fig. 2:

a 90 ° folded side view of the plant of Fig. 1 in a highly schematized form;

3:

a plan view of the system according to the Figures 1 and 2 ;

4:

a schematic perspective view of the system according to the figures 1 to 3, but without housing.

An inventive system 10 for the metallic coating of holes 3 in a workpiece 1 is in FIGS. 1 to 4 shown. The workpiece 1 is in the illustrated embodiment, an engine block with 12 holes 3, which are arranged as cylinder bores in two rows of six in V-shape in the workpiece 1.

The system 10 has a machine bed 11 on which a housing 13 is arranged. The box-shaped housing 13 encloses a loading station 12 and a processing station 14 with a coating device 29.

On the machine bed 11 for receiving a workpiece 1, a base frame 16 of a conveyor 20 is arranged, which is formed in the illustrated embodiment as a turntable 22. The rotatable about a vertical axis of rotation driven horizontal turntable 22 has two opposite workpiece holders 23, in each of which a plate-shaped pallet module 21, each with a workpiece 1 is receivable. Via a pivoting device 26, the pallet module 21 can be pivoted with the workpiece 1 relative to the horizontal, so that the holes 3 in the workpiece 1 can be arranged vertically to carry out a metallic coating.

The workpiece 1 is received at the loading station 12 by a feed device, not shown. The housing 13 has in the region of the charging station 12 an opening, not shown, with a door. Furthermore, in the region of the charging station 12, a measurement of the workpiece 1 can take place with a measuring device 52. Subsequently, the turntable 22 is rotated by 180 °, wherein the workpiece 1 is conveyed from the loading station 12 to the opposite processing station 14. The processing station 14 is separated from the charging station 12 via a partition wall 24. In Fig. 2 the partition 24 is only partially shown in the lower area. However, the partition 24 extends through the entire space of the housing 13, so that the processing station 14 is sealed off from the charging station 12. For the passage of the workpieces 1 from the loading station 12 to the processing station 14 and back again two passes are provided. The passages are each closed by a sliding closure element 27, which can be opened for the passage of the workpiece 1 and then closed again.

In the processing station 14, the workpiece 1 is pivoted with the pivoting device 26 about a horizontal pivot axis, wherein in each case a series of holes 3 is aligned vertically, as shown in FIGS FIGS. 1 to 4 is apparent.

For applying the metallic coating, a coating device 29 with a rod-shaped coating lance 30 is provided, which has at its lower end at least one outlet opening 32 for a metal plasma jet. The metal plasma jet is generated in a known manner by a plasma generator with a cathode and a metallic anode. By means of a correspondingly high electrical voltage, an arc is formed between the cathode and the anode, by means of which the metallic anode is melted. The metallic anode is designed as a feedable wire, so that there is always sufficient material to form a metal plasma jet with the molten metallic particles. As a source of the metallic particles, a supply of powder may be provided instead of a wire. Via a gas nozzle device, a gas stream is generated, which emerges at supersonic speed from the outlet opening 32 at the lower end of the coating lance 30 approximately horizontally. In this case, the coating lance 30 is retracted with the outlet opening 32 in the bore 3 to be coated in the workpiece 1. The coating device 29 further comprises a sleeve-shaped suction bell, which surrounds the coating lance 30, but in the FIGS. 1 to 4 is not shown for reasons of clarity.

To process the coating lance 30, a portal device 40 with two parallel first track axes 41 is provided. On the two first track axes 41, a frame-like first carriage 47 is mounted horizontally movable. The first traversing carriage 47 itself has two linear, horizontal second traverse axes 42, which are arranged parallel to one another and perpendicular to the first traverse axes 41.

Along the two second track axes 42, a beam-shaped second carriage 48 is arranged horizontally movable. The second carriage 48 itself has a single vertical third travel axis 43. Along this third travel axis 43, a receiving carriage 45 is mounted vertically movable. On the receiving carriage 45, the coating lance 30 is rotatably supported.

After a workpiece 1 is positioned in the processing station 14, the coating lance 30 of the coating device 29 is retracted into a first bore 3 to be coated in the workpiece 1. The continuously operated coating lance 30 thereby generates a metal plasma jet which impinges on a bore wall of the bore 3 at supersonic speed. By rotating the coating lance 30 and the axial process in the vertical direction, a uniform defined metallic coating with a thickness of for example 10 .mu.m to 300 .mu.m is applied to the bore wall.

After moving out of the coating lance 30 from the first coated bore 3 of the metal plasma jet is directed directly on exit from the bore 3 on an impact surface of a receiving unit in a suction bell, not shown, which is supported together with the coating lance 30 on the receiving carriage 45. The receiving unit receives the particles of the metal plasma jet and is moved together with the coating lance 30 to the next hole to be coated 3. Then, the metallic coating is repeated at this second bore 3, wherein a corresponding coating of the further bore 3 in a row of the workpiece 1 is connected. Subsequently, the workpiece 1 can be pivoted about the pivoting device 26 about a horizontal axis, so that the second row of the engine block is arranged for processing in the vertical position. Then, a coating of these six holes 3 in the engine block-like workpiece 1 can join.

After completion of the coating, the coating lance 30 is retracted with the portal device 40 and the finished coated workpiece 1 can be fed back with the simultaneous supply of a new workpiece to be machined 1 in the charging station 12 through the right passage. In this case, the closure element 27 is opened at the passage. At the same time, a new workpiece 1 is conveyed from the loading station 12 into the processing station 14 through the opened left passage with the rotary movement of the turntable 22. About a handling robot 50 with a measuring device 52, the layer thickness and contour of the applied coating can be measured. With the measuring device 52 and the still uncoated holes 3 of a newly supplied workpiece 1 can be measured in advance, so that even more accurate testing of the performed coating by comparing the measurement data is possible. The coated workpiece 1 can then in the loading station 12 from the workpiece holder 23 of the turntable 22 are removed. Thereafter, a new workpiece 1 in the workpiece holder 23 of the conveyor 20 can be used. Thus, in the system 10 according to the invention, the loading and unloading as well as a measuring parallel to the machining of a workpiece 1 in the processing station 14 and thus made neutral to the machine main time. This allows efficient machine use.

With the portal device 40, the coating lance 30 can be moved at certain time intervals to a test station 54 for checking the jet pattern of the metal plasma jet or to a cleaning station 60.

The measuring device 52 has a laser, with which can be detected by retracting the measuring device 52 vertically into a bore 3 of the workpiece 1 on the handling robot 50, the contour shape and the diameter of the bore 3 over the axial length of the bore 43. By comparing the measurement data of the bore 3 before and after the coating can be determined exactly by a control of the system 10, the resulting coating with respect to the course of the layer thicknesses and the surface contour. On the basis of a comparison with predetermined nominal values, it can thus be decided by the control of the system 10 whether a correct coating has taken place or the workpiece 1 has to be fed to a post-processing. In addition, based on the measured values determined, the controller can set and change setting parameters of the coating device 29, in particular parameters for adjusting the metal plasma jet or the movement data of the coating lance 30, in order to counteract undesirable developments in the coating of subsequent workpieces 1 in good time.

Claims (12)

1. Installation for the metallic coating of a workpiece (1), with
   a housing (13), in which a loading station (12) for the supply and discharge of the workpiece (1),
   a coating device (29) which comprises a displaceable coating lance (30), by which a metal plasma jet can be generated to create a coating of metal particles, characterized in that
   the coating device (29) with the coating lance (30) and a measuring device (52) for measuring the coating thickness are designed integrated in the installation (10), that the coating device (29) with the coating lance (30) and the measuring device (52) are enclosed by the housing (13),
   that the coating device (29) is arranged in a processing station (14) which is separated from the loading station (12) by a partition wall (24),
   that the partition wall (24) comprises at least one closable passage (25),
   that the measuring device is arranged in the loading station, and
   that the measuring device is additionally designed to measure the workpiece before and after the coating.
2. Installation according to claim 1,
   characterized in that
   the measuring device (52) comprises a displaceable measuring sensor (53), which is displaceable between a calibration station and a workpiece holder (23) placed in the loading station (12).
3. Installation according to one of the claims 1 or 2,
   characterized in that
   a cleaning station (60) for cleaning the coating lance (30) is arranged in the processing station (14).
4. Installation according to claim 3,
   characterized in that
   in the processing station (14) a testing station (54) for testing the metal plasma jet generated by the coating lance (30) is arranged.
5. Installation according to one of the claims 1 to 4,
   characterized in that
   a suction device is provided, which is designed to extract air from the coating device (29), the calibration station, the testing station, and/or the cleaning station (60).
6. Installation according to one of the claims 1 to 5,
   characterized in that
   at least one workpiece holder (23) is provided, in which a workpiece (1) can be deposited and clamped in a defined position, and that the workpiece holder (23) is displaceable between the loading station (12) and the processing station (14).
7. Method according to one of the claims 1 to 6,
   characterized in that
   the passage is closed by a locking element (27), which releases the passage in order to allow the through-passage of the workpiece (1).
8. Installation according to one of the claims 6 or 7,
   characterized in that
   the at least one workpiece holder (23) is displaceable by means of a conveyor (20), which has an annular circulation path.
9. Installation according to claim 8,
   characterized in that
   the conveyor (20) is designed as a rotary table (22) that is arranged horizontally displaceable.
10. Installation according to one of the claims 1 to 9,
    characterized in that
    in the partition wall (24) two passages (25) are provided with one locking element (27) each.
11. Installation according to one of the claims 8 to 10,
    characterized in that
    the conveyor (20) is designed circumferentially in horizontal direction, and
    that the workpiece holder (23) is adjustably mounted to the conveyor (20), in particular pivotably around a horizontal pivoting axis.
12. Method for the metallic coating of a workpiece (1) with a displaceable coating lance (30), by which a metal plasma jet is generated, wherein a metallic coating of metal particles is created on the workpiece (1),
    characterized in that
    the creation of the coating and a measuring of the coating thickness are carried out integrated in an installation (10), which is designed in accordance with any one of the claims 1 to 11, whereby in a loading station (12) for supplying and discharging the workpiece (1) a measuring device is provided, with which the workpiece (1) is measured before and after the coating.

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