Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B12/00—Arrangements for controlling delivery; Arrangements for controlling the spray area
  • B05B12/08—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means
  • B05B12/082—Arrangements for controlling delivery; Arrangements for controlling the spray area responsive to condition of liquid or other fluent material to be discharged, of ambient medium or of target ; responsive to condition of spray devices or of supply means, e.g. pipes, pumps or their drive means responsive to a condition of the discharged jet or spray, e.g. to jet shape, spray pattern or droplet size
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B12/00—Arrangements for controlling delivery; Arrangements for controlling the spray area
  • B05B12/004—Arrangements for controlling delivery; Arrangements for controlling the spray area comprising sensors for monitoring the delivery, e.g. by displaying the sensed value or generating an alarm
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B5/00—Electrostatic spraying apparatus; Spraying apparatus with means for charging the spray electrically; Apparatus for spraying liquids or other fluent materials by other electric means
  • B05B5/025—Discharge apparatus, e.g. electrostatic spray guns
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05D1/00—Processes for applying liquids or other fluent materials
  • B05D1/02—Processes for applying liquids or other fluent materials performed by spraying
  • B05D1/04—Processes for applying liquids or other fluent materials performed by spraying involving the use of an electrostatic field
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
  • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
  • B05B13/00—Machines or plants for applying liquids or other fluent materials to surfaces of objects or other work by spraying, not covered by groups B05B1/00 - B05B11/00
  • B05B13/02—Means for supporting work; Arrangement or mounting of spray heads; Adaptation or arrangement of means for feeding work
  • B05B13/04—Means for supporting work; Arrangement or mounting of spray heads; Adaptation or arrangement of means for feeding work the spray heads being moved during spraying operation
  • B05B13/0447—Installation or apparatus for applying liquid or other fluent material to conveyed separate articles
  • B05B13/0452—Installation or apparatus for applying liquid or other fluent material to conveyed separate articles the conveyed articles being vehicle bodies

Definitions

• the invention relates to a method and a painting system for painting a workpiece with a nebulizer.
• the invention is directed to the problem of optimizing the spray produced by the sprayer with the aim of improving paint quality and minimizing the amount of paint and overspray consumed.
• housing parts or other workpieces application equipment are usually used, which have a robot and a supported by a movable arm of the robot atomizer.
• the atomizer generates a spray of paint, which is directed to the workpiece.
• the robot With the help of the robot, the atomizer is guided over the workpiece along a predetermined path so that the spray jet sweeps over the parts of the workpiece to be coated and evenly coats it with lacquer.
• rotary atomizers in which the paint on a very fast rotating disc, which is often referred to as a bell cup, is passed.
• the paint is accelerated to the outside and rips off at the edge of the bell cup.
• the paint film is thereby broken up into fine droplets. Since the paint is thrown radially outward, occurs at the atomizer additionally pressurized shaping air. This entrains the paint particles and deflects them so that an axially forwardly directed spray is formed.
• Lenkluft is understood to mean any air flow emerging from the atomizer.
• Some atomizers emit different airflows from the atomizer, which can be independently affected by special rings or caps.
• the paint is often electrostatically charged prior to atomization to minimize overspray.
• a voltage to the workpiece can be achieved that this electrostatically attracts the electrically charged paint particles. In this way, a larger proportion of the paint particles adhere to the workpiece.
• the spray jet geometry can be parameterized by several features. These include in particular the width of the spray jet at a predetermined distance from the atomizer, the maximum angle of the spray jet on exit from the atomizer with respect to a longitudinal axis of the atomizer, the density distribution of the spray jet, the outer contour of the spray jet and temporal changes of one of the aforementioned features. Changes to one Paint change, between successive Lackiervorticiann with the same paint or even within a single painting the spray jet geometry, this can lead to painting defects occur.
• the object of the invention is to provide a method and a painting system for painting workpieces, with which a desired geometry of the spray can be set particularly quickly.
• this object is achieved by a method for painting a workpiece, comprising the following steps: a) an application device with a sprayer directs a spray jet onto the workpiece whose spray jet geometry can be changed by the application device; b) a camera captures an image of the spray; c) an image processing device detects deviations between the spray jet recorded on the image and a desired spray jet; d) a control device controls the application device as a function of the deviations detected by the image processing device.
• the invention is based on the consideration to automate the visually performed by a skilled worker checking the spray jet geometry.
• the electronic processing of an image taken with a camera from the spray jet makes it possible to quantify characteristics of the spray jet in such a way that the geometry of the spray jet can be approximated to the target geometry by appropriate control of the application device on the basis of the information obtained thereby.
• the setting of a desired Sprühstrahlgeometrie is thus accessible to a control that leads to a constant and independent of variable paint parameters generating a defined spray jet geometry.
• an optical axis of the camera should be aligned at least substantially perpendicular to a longitudinal axis of the atomizer.
• the geometry of the spray jet is then easier to detect, as geometric distortions are minimized. In principle, however, it is also possible to take a picture from an oblique perspective. The image analysis is then more complicated because of the geometric distortions.
• an axis verstan the, which is aligned with an axis of symmetry of the spray.
• the longitudinal axis is an axis of symmetry of the exit nozzle of the atomizer.
• the longitudinal axis is defined by the axis of rotation of the bell cup.
• the image of the spray jet can be picked up while it is pointed at the workpiece. Especially when a control of Sprühstrahlgeometrie is performed during a painting process, this is usually preferable. Al lerdings, the surface of the workpiece can affect the shape of the spray. Because of it, it is at least then, if only at longer intervals the spray jet geometry is checked in the manner according to the invention, usually cheaper if currency rend the recording of the image in step b) the painting of the workpiece is interrupted.
• the nebulizer may acquire a test object, e.g. B. a plate, paint.
• a test object e.g. B. a plate, paint.
• conditions are created that come as close as possible to a real painting process, but are nevertheless exactly reproducible. It is possible to additionally detect the painted surface of the test object by the same or another camera. Then also the painting result achieved there to assess certain parameters of the spray, z. B. the density distribution, are used.
• the image processing device can subject the recorded image of the spray jet to edge filtering.
• edge filtering By determining the outer edge of the spray jet, particularly important features of the spray jet geometry can be determined, including the width of the spray jet at a given distance from the atomizer, the maximum angle the spray jet at the outlet from the atomizer with respect to a longitudinal axis of the atomizer and the shape of the outer contour of the spray jet.
• control device can change at least one of the following control parameters of the application device: pressure of a shaping air delivered by the rotary atomizer, rotational speed of the rotary atomizer, volume flow and temperature of the paint fed to the atomizer.
• control parameters have a direct influence on the geometry of the spray and are therefore suitable for influencing the spray jet geometry in order to minimize deviations from a desired geometry.
• the invention also relates to a painting system for painting a workpiece with an application device which is adapted to direct a spray jet onto the workpiece with a sprayer whose spray jet geometry can be changed by the application device.
• a camera is set up to take a picture of the spray.
• An image processing device is set up to detect deviations between the spray jet recorded on the image and a desired spray jet.
• a control device is set up to control the application device as a function of the deviations detected by the image processing device.
• the camera may be located outside of a spray booth.
• the camera is in the Additional cleaning devices, for example, an air curtain or a liquid cleaning, may be provided to prevent contamination of the camera optics with overspray on the lower area of the spray booth.
• an arrangement of the camera on a movable arm of a robot carrying the atomizer may be advantageous in certain applications.
• Figure 1 is a perspective view of a painting system according to the invention, wherein only a part of the painting booth is shown;
• Figure 2 is a schematic representation of important component of the coating system according to the invention.
• Figure 3 is a schematic representation of how a camera takes a picture of a
• FIGS. 4a to 4d show an image taken by the camera in different stages of image processing.
• FIG. 1 shows a perspective view of a painting system according to the invention and denoted overall by 10.
• the painting booth 12 includes in the illustrated embodiment, a bottom portion 14, four side walls 16, of which only two are shown in the figure 1, and also not shown ceiling.
• the left side wall 16 shown is provided with a window 18, which releases the view into an interior 20 of the spray booth 12.
• the paint booth 12 stands on a floor structure 20, as is well known in the art.
• the bottom portion 14 of the paint booth 12 carries in the illustrated embodiment, an indicated at 22 conveyor system on the workpieces - here vehicle bodies 24 - can be conveyed along a conveying direction.
• the vehicle bodies 24 are introduced by means of the conveyor system 22 by roller shutters or other closable openings before painting in the paint booth 12 and discharged after completion of painting again from the spray booth 12.
• Each application device 26a, 26b includes a robot 28a or 28b, each having a movable robot arm 30a or 30b.
• Each robotic arm 30a, 30b carries a rotary atomizer 32a, 32b, to which liquid paint and compressed air are supplied via lines not shown.
• the paint and compressed air supply is part of the application devices 26a, 26b and can be arranged at least partially outside of the spray booth 12.
• the paint can be, for example, a basecoat which is responsible for the coloring of the body, or a clearcoat, which protects the previously applied basecoat from UV radiation and ensures the gloss of the vehicle bodies 24.
• the paints used differ not only in their transparency and color, but also in their viscosity and surface tension.
• the geometry of the spray 34 generated by the rotary atomizers 32a, 32b therefore depends on the type of paint to be applied. Since the temperature of the paint also influences its viscosity and surface tension, the geometry of the spray jet 34 and thus also the painting result can vary even if one and the same paint is applied.
• the robot arms 30a, 30b move the rotary atomizers 32a, 32b mounted therein rapidly along predetermined paths over the vehicle bodies 24.
• the spray jet 34 generated by the rotary atomizers 32a, 32b covers the surface of the vehicle body at a predetermined distance. series 24, so that the paint particles can settle on it.
• the painting system 10 differs from conventional systems in that the painting process is monitored by a first camera 36a and a second camera 36b.
• the first camera 36 a is mounted outside of the spray booth 12 and takes pictures of the painting process through the window 18 therethrough.
• the second camera 36b is mounted inside the spray booth 12 and may be provided with an additional guard (not shown) for protection against overspray.
• the cameras 36a, 36b are normal cameras which record images in the visible wavelength spectrum.
• FIG. 2 shows important components of the coating system 10 according to the invention in a schematic representation. Shown above is the first camera 36a, which is connected via a signal line to an image processing device 38, which is also part of the painting system 10. The image processing device 38 is connected via a further signal line to a control device 40 for the application device 26a. In FIG. 2, the image processing device 38 and the control device 40 are shown as separate structural units. Of course, these devices can also be spatially combined and in particular realized as different modules of a computer program that is executed on a microprocessor.
• the first camera 36a receives images of the spray jet 34 during the ongoing painting process-as shown at the top right in FIG. These images are processed by the image processing device 38 and compared with a desired spray. Since the position of the robot arm 30a, and thus the position of the rotary atomizer 36a, is known at all times, the perspective distortion resulting from the oblique observation of the spray 34 by the first camera 36a can be calculated out in the image processor 38. The result is an equalized image 34 'of the spray jet 34, as shown by way of example in FIG. 2 on a screen 42 of the image processing device 38. The image 34 'of the spray jet 34 can now be processed with suitable image processing algorithms and analyzed geometrically.
• the geometric parameters derived therefrom are compared in the image processing device 38 with desired parameters of a desired spray jet. If the deviations between the geometry detected by the camera 36a and the desired geometry of the spray jet exceed predetermined tolerances, then a control algorithm of the control device 40 calculates therefrom control commands for the application device 26a in order to minimize the deviations.
• the control device 40 can act in particular on the pressure with which steering air from the rotary atomizer 32a ausstritt, on the pressure and thus the volume flow of the output from the rotary atomizer 32a paint and / or to the temperature of the rotary atomizer 32a supplied paint. It is also contemplated to alter the trajectory of the robotic arm 30a to thereby adjust the distance between the rotary atomizers 32a and the surface of the vehicle body 24.
• the spray 34 is directed to a test object 44, which in the simplest case is a plate.
• the axis of rotation 46 of the rotary atomizer 32a is aligned with the aid of the robot arm 30a such that it runs perpendicular to the planar surface of the test object 44.
• the optical axis 48 is parallel to the surface of the test object 44 and perpendicular to the axis of rotation 46 of the rotary atomizer 32a.
• a light source indicated at 50 is oriented so that its main emission direction is perpendicular to both the axis of rotation 46 and the optical axis 48.
• the geometry of the spray jet 34 can be detected particularly precisely with the aid of the camera 36.
• the illumination of the spray 34 by means of the light source 50 transversely to the optical axis 48th the camera 36 can be the paint particles recognize well.
• the distinctiveness of the paint particles is supported when a screen 52, which is illuminated as evenly as possible, is located on a side opposite the camera 36.
• FIG. 3 Plotted in FIG. 3 are important geometric features of the spray jet 34, which can be derived from the image taken with the aid of the camera 36. Shown is the width B of the spray 34 at a distance A from the rotary atomizer 32a and the opening angle ⁇ of the spray directly on the bell cup 54 of the rotary atomizer 32a.
• FIGS. 4a to 4d show an image of the spray jet 34 in different image processing stages.
• Figure 4a shows a binary image obtained from the captured color image by applying a simple filtering algorithm.
• the color image is first converted into a grayscale image.
• a pixel is given the color white or black.
• an edge detection algorithm is used to obtain the contour of the spray as shown in Figure 4d.
• the setpoint values can be derived, for example, from images of a spray jet that have already been taken, which results in a good painting result for the relevant spray painting Workpiece has led.
• the setpoints can be determined from functional relationships that z. B. in the form of tables and based on experience gained over a longer period. Such empirical values can also be included in an expert system, which then outputs suitable setpoints.
• the robot arm 30a brings the rotary atomizer 32a back into the correct processing position relative to the vehicle body 24. If the detected deviations between the recorded spray jet and the desired spray jet are intolerably large, the painting process is continued with changed control parameters.
• the painting system 10 can be controlled so that the above-described check of the spray jet geometry is always performed when a property of the target spray is to be changed.
• the properties of the desired spray jet include the paint used. Therefore, the check is typically done after each color change and after each change of the workpiece type.

Landscapes

• Chemical & Material Sciences (AREA)
• Analytical Chemistry (AREA)
• Application Of Or Painting With Fluid Materials (AREA)
• Spray Control Apparatus (AREA)

Applications Claiming Priority (2)

Publications (1)

Family

ID=61223898

Family Applications (1)

Country Status (5)

Families Citing this family (4)

Family Cites Families (9)

• 2017
  • 2017-02-15 DE DE102017103007.7A patent/DE102017103007A1/de not_active Withdrawn
• 2018
  • 2018-02-08 EP EP18705120.6A patent/EP3703867A1/de not_active Withdrawn
  • 2018-02-08 CN CN201880024785.2A patent/CN110545920A/zh active Pending
  • 2018-02-08 WO PCT/EP2018/053152 patent/WO2018149725A1/de unknown
  • 2018-02-08 US US16/485,956 patent/US20200047207A1/en not_active Abandoned

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