CN111601680A - Method for grinding and/or polishing defects and apparatus for carrying out the method - Google Patents

Abstract

A method for grinding and/or polishing defects (1) in the surface coating of a workpiece, wherein a grinding or polishing disc held on a tool is guided over the defect (1) by means of pressure by means of an orbital, rotary and/or oscillating movement, the grinding or polishing disc being configured such that the tool fitted with the grinding or polishing disc (7) is automatically moved over the defect (1) in a computer-controlled manner on the basis of a stored program, wherein the grinding or polishing disc (7) is first guided along a concentric inner grinding path (2) relative to the defect (1) and then, without interruption, along a helical grinding path (3) to an outer concentric grinding path (4).

Description

Method for grinding and/or polishing defects and apparatus for carrying out the method

technical field

The present invention relates to a method for grinding and/or polishing defects in a surface coating of a workpiece according to the preamble of claim 1 and a device for carrying out the method.

Background technique

Especially in the case of defects in painted surfaces, such as car bodies, these defects are ground at various points, and the ground points are then polished. In this case, the grinding and polishing tool on which the grinding or polishing disc is held is manually guided by an operator who performs the corresponding grinding motion under contact pressure.

Due to machine design, the pads on which the grinding or polishing tool, on which the grinding or polishing blades are held, are moved in an orbital, rotary and/or vibratory manner, i.e. the pads can be moved without the operation of the machine personnel impact.

In addition to the correct selection of abrasives and polishing pastes, the contact pressure and the grinding or polishing motion are also critical to the machining result. When machining horizontal surfaces, in this case, the contact pressure is created by the quality of the grinding tool and the additional hand force exerted on the surface.

However, so far, ie manual means, cannot ensure an optimal and constant contact pressure during grinding or polishing of the surface. The same applies for an optimal and constant movement of the grinding tool, wherein due to the shape and size of the grinding tool and the pad, the exact center position of the defect to be machined can only be reached to a limited extent.

As a result, extra effort was put into post-processing and, moreover, only yielded corresponding results at unacceptable spread widths.

SUMMARY OF THE INVENTION

The present invention is based on the object of further developing a method of a general type that provides reproducibility while optimizing the grinding or polishing results.

This object is solved by a method having the features of claim 1 .

When using the method according to the invention, the quality of the grinding tool is compensated to such an extent that it has no influence on the result. The grinding motion of the grinding tool and its motion type (ie orbital, rotary and/or vibratory motion) are coordinated with each other and stored in the grinding and polishing path for execution in the computer.

The grinding or polishing disk is first guided along an inner grinding path that is concentric with the defect, and then the grinding or polishing disk is guided into the outer concentric grinding path along the helical grinding path without interruption.

During the circular grinding motion, the grinding or polishing disc is preferably inclined inwardly by a predetermined angle relative to the perpendicular of the defect, thereby defining a taper angle. This taper angle increases grinding capability at the center of the circular path for more precise, easier and faster processing of defects and a smooth transition to the edge of the grinding point.

In this case, the radius of the outer concentric grinding path is no greater than half the diameter of the grinding disc, or grinding or polishing disc.

The apparatus according to the method of the present invention is designed such that the grinding or polishing tool is designed as a robot connected to a computer having a pad attached to the arm and which can orbitally, rotate and/or vibrate move in a computer-controlled manner to hold a grinding or polishing disk, where the arm can move in a computer-controlled manner.

Description of drawings

The method according to the invention is described again below with reference to the accompanying drawings, wherein:

Figures 1 and 2 show schematic diagrams of the sequence of movements during grinding according to the invention,

Figures 3 to 5 also show in schematic diagrams the sequence of movements during polishing according to the invention.

Detailed ways

The grinding movements and the types of movements of the grinding tool are stored in the computer as work programs as automatic grinding paths.

At the beginning of the grinding motion, the center of the grinding disc or pad is aligned with the defect 1 to be ground, wherein the grinding path starts from the inner circle 2 . During the grinding motion of the grinding path 2 , the center vertical direction of the grinding disc is inclined inwardly at a predetermined angle with respect to the vertical of the defect 1 at a taper angle.

As mentioned above, when grinding a profile, the grinding tool and the workpiece to be machined are generally aligned orthogonally to each other.

Adjusting the grinding disc to a taper angle increases the grinding power at the center of the grinding disc, making it easier and faster to grind defects.

Depending on requirements, the grinding disc can be guided along the grinding path 2 one or more times.

Along the helical path 3, the grinding disc is guided into the concentric grinding path 4 without the need to adjust the grinding disc with a taper angle, resulting in a smooth grinding transition and a flat end result. This produces a grinding point area F2 as shown in FIG. 2 . The grinding path 4 can also be ground one or more times.

The distance between defect 1, grinding path 2 and grinding path 4 depends on the size of defect 1 and its extent and the diameter D of the grinding disc. The helical path 3 may have different lengths depending on the extent of the defect.

The radius of the grinding paths 2 and 4 must always be less than half the diameter D of the grinding pad or grinding disc, whereby, especially due to the inner circular path 2, the defect points of the workpiece to be machined are subjected to more intensive continuous machining, Thus, a so-called effective grinding area F1 as shown in FIG. 2 is obtained.

The distance between the radii R1, R2 of the grinding paths 2 and 4 can be adjusted according to the defect to be machined. For example, the distance between the inner grinding path 2 and the outer grinding path 4 is chosen to be as small as possible in order to be able to effectively operate at edges such as along the edges of the body, along the thick edges of body modules and at tight radii of the body Machining defects in the area.

Grinding time is allocated to grinding paths 2 and 4, as well as grinding tool contact pressure, speed or stroke rate. In this case, the grinding spots produced in a shorter time than before always have the same shape and properties and are therefore reproducible. The taper angle decreases continuously to 0 at the beginning of the grinding path 3 in a predefined area.

Another advantage of the method according to the invention is that the shape of the abrasive on the carrier can be made smaller, which greatly reduces the amount of abrasive required and the energy consumption required.

Computer-supported statistical evaluation between many defects and abrasive consumption is the basis for continuous process improvement.

3-5 schematically illustrate the motion sequence of polishing tools during automatic polishing. The polishing movement and the type of movement of the polishing tool are also computer controlled, with the corresponding parameters stored in the computer.

As with grinding, the center of the polishing head is perfectly aligned with defect 1.

When polishing a profile, such as the surface of a body, the polishing tool and the surface are aligned orthogonally to each other.

Figure 3 shows a first polishing path 5, which starts from defect 1 and extends helically outward.

As the process continues, the subsequent second polishing path 6 spirals back to defect 1 . In this case, the movement along the polishing paths 5, 6 may take place one or more times as desired.

Figure 5 shows an outline of the sequence of motions according to polishing paths 5 and 6, which corresponds to the polishing process, wherein the first polishing path 5 is shown as a solid line and the second polishing path 6 is shown as a dashed line.

Within the polishing paths 5, 6, the contact pressure is adjusted in steps, wherein the adjustment is made according to the path length. In this case, the contact pressure is regulated, for example, by a pressure sensor in the robot.

Starting from defect 1 , the movement starts with a contact pressure P1 , which decreases outwardly along the polishing path 5 according to polishing path 5 .

At the transition from polishing path 5 to polishing path 6, the contact pressure is further reduced to smooth the polishing transition.

In a further process, ie on the polishing path 6 back to the defect, the contact pressure is reduced to prevent heating of the polishing pad, which is usually designed as a polishing sponge.

The polishing time along the polishing path 5, 6 and the contact pressure of the polishing tool and the corresponding rotation or stroke rate are stored in a corresponding program of the computer. The polishing time is also adapted to the size of the grinding point.

By means of the method according to the invention, polishing points can be produced in a relatively short time, and incidentally, the polishing points always have the same characteristics and shape and are therefore reproducible. As a result, the amount of polishing agent used and the energy requirement can be significantly reduced.

A statistical evaluation between polishing times and polishing agent consumption is now possible as a basis for continuous process improvement.

list of reference signs

1 defect

2 grinding paths

3 spiral paths

4 grinding paths

5 polishing paths

6 polishing paths

7 Grinding or polishing discs

F1 effective grinding area

F2 grinding area

R1 radius

R2 radius

D The diameter of the grinding or polishing disc.

Claims (9)

1. A method for grinding and/or polishing defects (1) in the surface coating of a workpiece, wherein a grinding or polishing disc (7) held on a tool is guided over the defect (1) by means of pressure by means of an orbital, rotary and/or oscillating movement, wherein the tool equipped with the grinding or polishing disc is automatically moved over the defect (1) in a computer-controlled manner according to a stored program, characterized in that the grinding or polishing disc (7) is first guided along a concentric inner grinding path (2) relative to the defect (1) and then is guided uninterruptedly along a helical grinding path (3) to an outer concentric grinding path (4).

2. Method according to claim 1, characterized in that at the beginning of the grinding or polishing process the centre of the grinding or polishing disc (7) is directly aligned with the internal grinding path (2).

3. A method according to claim 1 or 2, wherein the tool is aligned orthogonally relative to a contoured surface when grinding or polishing the surface.

4. Method according to any of the preceding claims, characterized in that during the grinding movement in the grinding path (2) the grinding or polishing disc (7) is inclined inwardly by a predetermined angle with respect to the perpendicular to the defect (1).

5. Method according to any of the preceding claims, characterized in that the grinding or polishing disc (7) is guided along the internal grinding path (2) one or more times.

6. Method according to any one of the preceding claims, characterized in that, starting from the defect (1), the grinding or polishing disc (7) is guided outwards along a spiral-shaped polishing path (5) and subsequently the grinding or polishing disc (7) is guided directly along a spiral-shaped polishing path (6) back to the defect (1).

7. The method according to any of the preceding claims, characterized in that the radius (R1) of the outer grinding path (4) is less than half the diameter (D) of the grinding or polishing disc (7).

8. Method according to any one of the preceding claims, characterized in that the contact pressure of the grinding or polishing disc (7) is reduced along the polishing path (6) starting from the defect (1) along the polishing path (5) and in the further course towards the defect (1).

9. An apparatus for performing the method according to claim 1, characterized in that the grinding or polishing tool is designed as a robot connected to a computer, which robot comprises a pad attached to an arm of the robot, and which pad is movable in an orbital, rotary and/or oscillating manner for holding a grinding or polishing disc (7), wherein the arm is movable in a computer-controlled manner.

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