EP3612351B1 - Method for partially grinding a surface and grinding device for carrying out the method - Google Patents

Description

The present invention relates to a method according to the preamble of claim 1 and a grinding device for carrying out the method.

After a check of a surface, in particular a fully varnished surface, by means of a sensor system, this defect identified in this way has so far been processed manually, for which purpose a hand-operated grinding machine with a grinding plate on which a grinding sheet is held is used.

The mounting of the sanding sheet on the sanding plate is usually achieved by a Velcro connection, the pairing of sanding plate / sanding sheet being designed accordingly on their mutually facing sides.

Another way of attaching the sanding sheet to the sanding pad is achieved with a self-adhesive bond.

Another way of holding the sanding sheet on the sanding pad is by suction, for which purpose the sanding machine is connected to a suction device.

A sanding sheet with a very fine grain size is used to remove the defect, i.e. to match the adjacent defect-free areas, whereby the sanding process itself is punctiform, but with orbital, rotating and / or vibrating movements.

The manual processing of the point of failure results in a whole series of necessary work steps which are particularly opposed to cost optimization.

Changing the sanding sheet is relatively time-consuming and therefore costly, especially since the sanding sheet has to be attached to the sanding pad with a precise fit, centrically and with the correct side.

Placing the hand-held grinding machine with the associated grinding plate and the grinding sheet attached to it not parallel to the surface is very error-prone and requires additional work.

When the sanding sheet protruding laterally over the sanding pad is removed, sanding dust in the grain can loosen and disrupt the machining process as a whole, especially since the sanding dust is distributed over a larger area on the surface.

The U.S. 5,394,654 discloses a method for removing a flaw from a treated surface, in which the flaw is recognized visually, that is to say on the face of it, and marked manually. This marking is then recorded by cameras as the basis for subsequent processing. However, due to the exclusively visual detection of the fault location, this method is not suitable for ensuring a consistent, reproducible workflow.

A prior art deviating from the generic method is given by DE 20 2013 101 858 U1 again. It describes that a system is used to grind the surface before surface refinement, for example by painting. This literature does not provide any information on the processing of a final lacquered surface as provided by the generic method.

Next is in the U.S. 2,258,733 A discloses a grinding device which has a grinding belt as a grinding sheet, this grinding device, however, not being suitable for performing generic grinding work.

The invention is based on the object of further developing a method of the generic type in such a way that it can be carried out more cost-effectively.

This object is achieved by a method with the features of claim 1 and by a grinding device for performing the method.

The invention automates the grinding of the surface in the area of a defect, which results in a number of advantages over the method according to the prior art.

Post-processing time is shortened because the sanding belt is precisely aligned in the connection area with the sanding pad for optimal use. The exact guidance, which is typically not strictly adhered to during manual processing and which requires a longer processing time in order to achieve the corresponding result, is no longer to be taken into account with regard to the processing time, i.e. the processing to achieve an optimal grinding result is now more reliable, reproducible and possible in a significantly shorter time.

Another advantage of the invention is the possibility of setting the sanding pad at an angle, which has proven to be particularly effective. This influences both the number of grinding points and the grinding result with a reduction in the roughness depth.

Naturally, this results in considerable cost advantages, which are remarkable insofar as the processing of the surface in the sense of the invention takes place on series products, that is to say in a quasi-uninterrupted workflow.

According to a further concept of the invention, the sanding belt is fed from a dispenser to the sanding plate and fixed thereon. This fixation can be done by a Velor Velcro connection, an adhesive connection or a vacuum connection, in which case the sanding plate, modified accordingly with suction openings, is connected to a suction device.

To release the connection, in particular the Velcro and adhesive connection, an ejector is provided in the area of the sanding plate, after which the sanding belt is moved the appropriate distance into a subsequent unused area of the sanding belt. The sanding belt is preferably transported in cycles, whereby, depending on experience, the sanding belt can be used in an immovable position relative to the sanding plate for several processing steps.

The intermittent advancement of the sanding belt into the effective area of the sanding plate, depending on requirements, also results in a considerable reduction in processing time compared to manual changing of the sanding sheet.

When a robot is used according to the invention, there is a further reduction in set-up time compared to the prior art due to the elimination of the necessary ways to remove and change the sanding sheet.

According to a further idea of the invention, the sanding belt dispenser is designed in the sense of a cassette, with one unwinding and one winding shaft each. This cassette is part of a grinding device with a robot arm and is to be completely replaced if necessary, i.e. after the grinding belt has been used up, and if necessary, re-equipped with grinding belt.

Instead of using the cassette in the automatic grinding machine, the cassette can also be part of a hand-held grinding device. With the appropriate construction of the cassette, the grinding dust that arises during grinding can be separated in the cassette.

Furthermore, in the case of the grinding device according to the invention, the grinding belt can be kept partially taut in the cassette, for which purpose a braking device can preferably be provided in the cassette or directly adjacent outside, but which is functionally connected to the grinding belt.

To tighten the sanding belt, pneumatically or hydraulically operated cylinders can be provided, one of which presses the sanding belt onto a pulley and thus fixes it before the sanding belt enters the sanding pad and another cylinder engages the sanding belt on the outlet side, this cylinder with a force sensor, for example a pressure sensor is in operative connection.

The grinding movement to the surface, as it is known from the prior art, takes place in the automatic grinding machine by a corresponding modification of the drive, an orbital or vibrating movement being generated. In the case of rotating grinding, the entire cassette is moved along with it.

In order to be able to process more sensitive surfaces better, the longitudinal edges of the sanding belt are designed differently in terms of their shape, for example straight, wavy, serrated or a combination of these.

The length of the sliding track used can be recorded by means of a sensor system. This can be determined under computer control via the initial length and the end of the sanding belt.

In addition or as an alternative, a sensor, for example in the form of a laser, is connected upstream of the sanding plate in the direction of advance of the sanding belt, which detects an opening provided at the end of the sanding path, this opening being placed in such a way that the length of the sanding belt can be used to the maximum.

So far, problems have arisen when the sanding belt, especially one whose backing is made of paper, tears, which leads to damage both to the surface to be sanded and to the sanding device itself.

To detect such a tear, according to a further concept of the invention, a corresponding sensor system is provided, which is preferably arranged in front of the sanding plate as viewed in the direction of passage of the sanding belt. This sensor system is designed, for example, so that it has a motion sensor and a follower that moves synchronously with the grinding belt and is provided with markings, this sensor system being assigned to the non-driven output of the grinding belt, preferably in the cassette.

If the grinding belt tears, its withdrawal is interrupted by an unwinding shaft, so that it comes to a standstill, as does the follower, which is arranged in a non-rotating manner relative to the unwinding shaft and can be designed as a gearwheel, for example, with the teeth forming the markings. Another configuration of the follower is also conceivable, provided that it has elements as markings that allow the movement of the follower or its standstill to be recognized via the motion sensor.

Further advantageous developments of the invention are characterized in the subclaims.

The method according to the invention and an embodiment of a grinding device according to the invention are described below with reference to the accompanying drawings.

Fig. 1 und 2

jeweils in einer schematischen Seitenansicht einen Teilausschnitt einer erfindungsgemäßen Schleifeinrichtung

Fig. 3

eine Einzelheit der Schleifeinrichtung in verschiedenen Ausführungsvarianten

Fig. 4 - 7

jeweils weitere Ausführungsvarianten der Schleifeinrichtung in schematischen Seitenansichten

Fig. 8

eine erfindungsgemäße Schleifeinrichtung in einer Vorderansicht

Fig. 9

einen Teil der Schleifvorrichtung in einer perspektivischen Ansicht.

Show it:

Figs. 1 and 2

each in a schematic side view of a partial section of a grinding device according to the invention

Fig. 3

a detail of the grinding device in different versions

Figures 4-7

each other design variants of the grinding device in schematic side views

Fig. 8

a grinding device according to the invention in a front view

Fig. 9

a part of the grinding device in a perspective view.

In the Figures 1 and 2 is a part of a grinding device 1 for removing a flaw, shown in a, for example, finished, especially varnished surface by grinding, after an optical detection of the flaw by means of an optical sensor system, not shown, a flexible sanding belt 5 is moved across the surface and against the surface to be processed Error location is pressed.

A robot arm 2 carrying a sanding plate 3 is in operative connection with the sensor system and is moved to the fault location according to the requirement by the sensor system.

The sanding belt 5 is held on the sanding plate 3, which can be moved to the surface for sanding the flaw, for example orbital, vibrating or rotating.

The grinding belt 5 is held in a dispenser in the form of a cassette 4 and is wound onto a winding shaft 7 to form a roll 6 and is wound onto a winding shaft 8, preferably in cycles, in accordance with the grinding process.

The holding of the sanding belt 5 on the sanding plate 3 takes place in a material or non-positive manner, for example by a detachable adhesive connection or by a Velcro or suction connection. For the latter, a suction device (not shown) is provided which is connected to the sanding plate 3.

The sanding belt 5, which is in the Figure 3 is recognizable as a section in different design variants, can have differently contoured edges. So is in the Figure 5a) one edge of the grinding belt 5 is wavy and the other edge is straight. In the Figure 5b) are both opposite longitudinal edges straight, while the Figure 5c) shows a variant in which both longitudinal edges are jagged.

To release the sanding belt 5 from the sanding plate 3, ejectors 9 are provided in the area of the sanding plate 3, according to the illustrations in FIG Figures 5 to 7 .

In the case of the Figure 5 The example shown is provided on both sides of the grinding plate 3 ejectors 9, the direction of passage of the grinding belt 5 being indicated by an arrow.

In the Figures 6 and 7 the sanding plate 3 is covered by the ejector 9. In operation, the grinding plate 3 is raised relative to the ejector 9 in such a way that the ejector 9 releases the connection of the grinding plate 3 to the grinding belt 5 in the sense of an abutment.

In the Figure 4 The cassette 4 accommodating the grinding belt 5 is shown as a detail, the unwinding and winding shafts 7, 8 being separated by a partition 10 in such a way that grinding dust does not get into the area where the unused grinding belt 5 in the form of the roll 6, on the left in the figure.

The Fig. 8 shows a grinding device equipped with the grinding belt 5, the passage of the grinding belt 5 being indicated by arrows.

The take-up shaft 8 is driven and pulls the grinding belt 5 from the unwinding shaft 7, the grinding belt 5 being guided over a plurality of deflection rollers 13.

In order to be able to recognize the end of the sanding belt after use, a laser source 14 is provided downstream of the unwinding shaft 7, which detects an opening (not shown) made at the end of the sanding belt 5 during its production with the help of a laser beam 15, so that the useful length of the sanding belt 5 can be used optimally.

Since the cassette 4 in the exemplary embodiment is firmly connected to the robot arm 2, while the grinding plate 3 with associated units is held on the robot arm 2 via a movable contact flange, the grinding belt 5 in the area of the grinding plate 3 must be kept under constant tension.

For this purpose, two tensioning elements are provided in the example, namely in the form of pneumatically or hydraulically operated cylinders 11, 12, a cylinder 11 pressing the grinding belt 5 against a deflection roller 13 before the grinding belt 5 enters the grinding plate 3.

Outlet side, d. H. downstream of the sanding plate 3, the sanding belt 5 is tensioned by the cylinder 12, which engages the sanding belt 5 between two deflection rollers 13 over which the sanding belt 5 is guided.

In the Fig. 9 a sensor system is shown as a detail, with which a tearing of the grinding belt 5 is detected.

This sensor system consists of a movement sensor 16 and a corresponding follower 17, which is designed as a gear and which is held non-rotatably on the unwinding shaft 7 so that it performs a synchronous movement with the freely rotating unwinding shaft 7.

Since the unwinding shaft 7 is dragged along with the grinding belt when the winding shaft 8, which is connected to a motor, is actuated, the idler 17 is also rotated accordingly. If the grinding belt 5 breaks, the unwinding shaft 7 stands still, as does the idler 17, which is detected by the movement sensor 16, so that the drive of the take-up shaft 8 is interrupted.

List of reference symbols

1

Grinding device

2

Robotic arm

3

Sanding pad

4th

cassette

5

Sanding belt

6th

role

7th

Unwinding shaft

8th

Take-up shaft

9

Ejector

10

Partition

11

cylinder

12

cylinder

13th

Pulley

14th

Laser source

15th

laser beam

16

Motion sensor

17th

Fellow travelers

Claims (15)

1. A method for removing a flaw of a treated, in particular finish-painted surface by grinding, wherein after a detection of the flaw, a flexible abrasive sheet is moved toward the surface and pressed against the flaw to be treated, characterized in that the flaw is detected by means of a sensor system, which is operationally connected to a robot arm (2) supporting a grinding disk (3), wherein the abrasive sheet formed as an abrasive belt (5) is supplied to the grinding disk (3) and it is pressed against the flaw.
2. The method according to Claim 1, characterized in that the abrasive sheet (5) is detachably connected in an integrally-joined or friction-locked manner to the grinding disk (3).
3. The method according to Claim 1 or 2, characterized in that the abrasive belt (5) is held on the grinding disk (3) by a hook-and-loop connection or adhesive bond or by suction.
4. The method according to any one of the preceding claims, characterized in that the grinding disk (3) having the abrasive belt (5) fastened thereon is moved in a rotating, vibrating, or orbital manner.
5. The method according to any one of the preceding claims, characterized in that the abrasive belt (5) is detached from the grinding disk (3) after the grinding of the flaw.
6. The method according to any one of the preceding claims, characterized in that the abrasive belt (5) is moved further cyclically by the associated longitudinal extension of the flaw after the detachment from the grinding disk (3).
7. A grinding device for carrying out the method according to Claim 1, having a flexible abrasive belt, characterized in that a grinding disk (3) supporting the flexible abrasive belt (5) is fastened on a robot arm (2), which is operationally connected in a computer-controlled manner to a sensor system detecting the flaw, whereby an ejector (9) is associated with the grinding disk (3) for detaching the abrasive belt (5) held on the grinding disk (3).
8. The grinding device according to Claim 7, characterized in that the abrasive belt (5) is mounted in a dispenser, said dispenser consisting of a cassette (4) arranged in the region of the robot arm (2).
9. The grinding device according to any one of Claims 7 to 8, characterized in that at least one of the longitudinal edges of the abrasive belt (5) is contoured.
10. The grinding device according to any one of Claims 7 to 9, characterized in that the cassette (4) comprises a winding shaft (8) and an unwinding shaft (7), for winding and unwinding the abrasive belt (5), whereby the winding shaft (8) is cyclically drivable.
11. The grinding device according to Claim 10, characterized in that a sensor, using which the end of the abrasive belt (5) is detectable, is associated with the unwinding shaft (7).
12. The grinding device according to Claim 11, characterized in that the sensor for the end detection of the abrasive belt (5) consists of a laser emitter (14), wherein the abrasive belt (5) comprises a passage in the end region, which corresponds to a laser beam (15) of the laser emitter.
13. The grinding device according to any one of Claims 10 to 12, characterized in that a sensor system is provided associated with the unwinding shaft (7), for detecting a torn abrasive belt (5).
14. The grinding device according to Claim 13, characterized in that the sensor system consists of a movement sensor (16) and a follower (17), which moves synchronously with the abrasive belt (5) or the unwinding shaft (7), and which is provided with markings detectable by the movement sensor (16).
15. The grinding device according to any one of Claims 7 to 14, characterized in that tensioning means are provided, using which the abrasive belt (5) is tensioned, whereby one tensioning means is provided on the intake side to the grinding disk (3) and a further tensioning means is provided on the outlet side.

Images