WO2013110555A1

WO2013110555A1 - Method for polishing a flat surface of a workpiece made of a brittle material, and a device for carrying out the method

Info

Publication number: WO2013110555A1
Application number: PCT/EP2013/050938
Authority: WO
Inventors: Fábio SOUSA; Jan Aurich
Original assignee: Technische Universität Kaiserslautern
Priority date: 2012-01-27
Filing date: 2013-01-18
Publication date: 2013-08-01
Also published as: DE102012100680A1

Abstract

The invention relates to a method for polishing a flat surface (21) of a workpiece (10) made of a brittle material and to a device for carrying out the method. A polishing process on the surface (21) of the workpiece (19) along a first polishing direction (P1) is carried out in a first polishing step. A polishing process on the surface (21) of the workpiece (19) along a second polishing direction (P2) is carried out in a second polishing step, said first polishing direction (P1) and second polishing direction (P2) running in different directions.

Description

A method for polishing a flat surface of a workpiece made of a brittle material and an apparatus for performing the

process

Description

The invention relates to a method for polishing a flat surface of a workpiece made of a brittle material and to an apparatus for carrying out the method.

When polishing a flat surface of a workpiece made of a brittle material, such as the surface of a porcelain stoneware tile, arises on the polished surface polished uneven distribution of the gloss generated by the polishing. This uneven distribution of the gloss, which is also referred to as uneven gloss distribution, is caused by the Pol iervorgang own kinematics of the polishing tools that are used to polish the surface.

The uneven gloss distribution on the surface of the polished workpiece is also referred to as a polishing shade. Sometimes they are Polished shadows sharp enough to be visually perceived by the human eye and considered a product defect.

Polishing lines used to polish porcelain stoneware tiles have two main directions of movement during the polishing cycle. One direction is the rotation of the polishing heads of the polishing tools. The second movement is the forward movement of the conveyor belt

Polishing road. The then polished porcelain stoneware tiles have a distinct polishing shade. In order to reduce the polishing shadow, it is known to introduce additional movement in polishing lines, namely, a swinging movement of the polishing heads transversely to the forward movement of the conveyor belt. As a result, polishing shadows can not always be sufficiently reduced.

Due to the transverse vibration of the polishing head and the simultaneous

As the tile advances through the conveyor belt, each polishing head makes a sinusoidal motion with respect to the tile. This sometimes causes a zig-zag gloss pattern to appear on the polished surface (see also C. Cass's "Optical Haze on Polished Porcelain Tiles, A Consumer's Perspective", World Congress on Ceramic Tile Quality - QUALICER, Castellon - Spain, 2010) It is known that the above-mentioned defects in the polishing of the surface can be partially improved by the fact that the sinusoidal transverse vibrations of the individual polishing heads partially overlap (see also FJP Sousa, JC Aurich, WL Weingaertner, OE Alarcon, "Kinematics of a Single abrasive particle during the industrial polishing process of porcelain stoneware tiles ", Journal of the European Ceramic Society, 3,183-31,90, 2007). Regardless of the previously used kinematics when polishing the

Surface of a workpiece made of a brittle material are regularly, however, always uneven Glanzvertei treatment and polishing shadow recognizable, which is particularly pronounced along the transport direction of the tiles on the conveyor belt.

The invention is based on the object, the gloss distribution in the

Polishing a flat surface of a workpiece from a brittle

Improve material and reduce the visibility of the polishing shadow. Another object of the invention is to produce less oriented gloss patterns along a direction on the surface.

This object is achieved according to the invention by a method for

Polishing a flat surface of a workpiece from a brittle

Material comprising the following steps:

Polishing the surface of the workpiece in a first polishing step, wherein a polishing operation is performed along a first polishing direction on the surface of the workpiece;

Polishing the surface of the workpiece in a second polishing step, wherein a polishing operation is performed along a second polishing direction on the surface of the workpiece, wherein

the first polishing direction and the second polishing direction are in different directions.

The basic idea of the invention is therefore first to polish the surface of the workpiece to be polished in a first polishing step, wherein this polishing process is carried out along a first polishing direction, and then the already polished surface However, this second polishing operation is carried out along a second polishing direction, which of the first

Pol ierrichtung is different. Preferably, both in the first and in the second polishing step, the surface is completely or at least substantially polished. The first and second polishing direction can intersect at an angle or, for example, run in opposite directions, ie be opposite by 180 °.

According to the invention, it has surprisingly been found that such a double polishing of a surface of a workpiece to be polished from a brittle material improves the gloss distribution, reduces a visible course of the glossy coating on the surface and clearly reduces visible polishing shadows.

Due to the double polishing of the surface along different polishing directions, there is a superposition of each

Polishing process resulting gloss pattern. This overlay of the

Gloss pattern apparently leads to the effect that the course of the individual gloss patterns is less perceptible to the eye. Furthermore, the superposition of the gloss pattern leads to a homogenization of the gloss, resulting in a

Reduction of gloss and polishing shadow leads.

The polishing direction in the sense of the invention is the direction of the

Polishing process relative to the workpiece, so no direction absolutely to the room. The polishing direction is preferably a straight-line or linear direction. The polishing process can be performed, for example, oscillating or oscillating along the polishing direction, that is, for example, curved along the straight polishing direction, in particular sinusoidally along the straight polishing direction. at the polishing direction is therefore the main direction in which the corresponding polishing process is performed and along which the

Surface of the workpiece is polished.

The polishing process can by means of at least one polishing tool

be performed. Accordingly, in the first polishing step, a

Pol ierwerkzeug and the workpiece whose surface is to be polished, moves relative to each other, that the polishing tool along the first

Polishing direction is moved over the surface of the workpiece, and in the second polishing step, a polishing tool and the workpiece are moved relative to each other, that a polishing tool along the second polishing direction is moved over the surface of the workpiece, according to the invention, the first polishing direction and the second polishing direction in different directions. The first polishing step and the second polishing step may be performed with the same or different polishing tools. In this respect, the first polishing step can be carried out, for example, by a first polishing tool and the second polishing step by a second polishing tool. Alternatively, for example, the first and second polishing steps may be performed on the same polishing tool.

Since the polishing direction, as stated above, is the direction of the polishing operation relative to the workpiece, the polishing direction when performing the polishing operation by means of a polishing tool is the direction along which the surface of the workpiece and the polishing tool are relative

move each other.

In order to achieve that when performing the polishing process by means of at least one polishing tool, the surface of the workpiece and the Pol ierwerkzeug along the first and second polishing direction relative to each other move, for example

• al lein the workpiece to be moved relative to the polishing tool or

- Only the polishing tool are moved relative to the workpiece or

can

- Both the workpiece and the polishing tool are moved relative to each other.

In order to achieve that the first polishing direction and the second polishing direction are in different directions, the polishing operation in the second polishing step (relative to the workpiece) is performed in a different direction than the polishing process in the first polishing step. Whether in the first or second polishing step alone the workpiece or only the polishing tool or both the workpiece and the polishing tool are moved relative to each other, is arbitrary.

According to a preferred embodiment of the method according to the invention, the workpiece alone is moved relative to the polishing tool, that is carried to carry out a polishing operation, the polishing tool in the first and second polishing step along a first and second polishing direction on the polishing surface of the workpiece.

According to a development of this inventive idea, the workpiece is moved in the same direction during the first and second polishing steps, ie moved in space in the same absolute direction. It can be provided that the workpiece for polishing its surface in a first

Polishing step is moved relative to the first polishing tool

or is guided along such a first polishing tool that the polishing tool along the first direction of polishing on the the policrende surface of the workpiece is moved. In order to achieve that the workpiece in a second polishing step in the same (absolute)

Direction can be moved and still the second direction of polishing in a different direction (relative to the workpiece or relative to

Surface of the workpiece), the workpiece between the first and second polishing step can be repositioned or aligned differently to the direction of movement. Concretely, the workpiece is repositioned such that the polishing direction in the second polishing step is in a different direction than in the first polishing step. Subsequently, the workpiece for polishing its surface in a second

Polierschritt such relative to a second polishing tool moves or guided along a second polishing tool along, that the second polishing tool along the second polishing direction is moved over the surface to be polished of the workpiece.

The workpiece can be transported in the same direction in the first and second polishing step, for example, and repositioned after the first polishing step such that the polishing direction in the second

Polishing step in a different direction than in the first polishing step.

The repositioning of the workpiece after the first polishing step can be done for example by a positioning. This positioning means is designed such that it can reposition the workpiece to be polished or align it differently in space. It can be provided that the positioning means is controllable by a controller.

In particular, the positioning means can be controlled by a controller such that the workpiece is repositioned by the positioning means in a predetermined position. The positioning means may for example be a turntable or a gripper, by which the workpiece to be polished can be detected and repositioned.

The method can basically be used to polish a flat surface of a workpiece made of any brittle material. Particularly preferred is the method for polishing a

Surface of a workpiece made of an inorganic, non-metallic material used, in particular a ceramic material.

The method is particularly preferably used for polishing the surface of a tile, in particular a porcelain stoneware tile, from a ceramic material.

In a preferred embodiment, the method according to the invention is carried out on a polishing line. Polishing lines for polishing the

Surface of ceramic workpieces, in particular for example for polishing the surface of porcelain stoneware tiles, are known from the prior art. On polishing lines usually several workpieces to be polished are arranged and moved by means of transport along a straight-line direction. According to the invention, it may be provided that the surfaces of a plurality of workpieces are polished on a polishing line according to the invention during their transport by means of the transport means of the polishing line.

For movement or transport of the workpiece, this can be moved by any means of transport, which are known from the prior art for the transport or movement of workpieces to be polished from a brittle material, such as belts, chains or rollers. For polishing the surface of the workpiece, any polishing tools known in the art for polishing surfaces of workpieces of a brittle material, in particular polishing tools for polishing the surface of ceramics, in particular, for example, for polishing the surface of porcelain stoneware tiles may be used. The polishing tool used is preferably a polishing machine with a polishing disk which can be rotated about an axis of rotation.

According to a preferred embodiment, the polishing tool is in the first polishing step and the second polishing step along the first and second Pol eierrichtung over the surface to be polished

Workpiece moves so that the axis of rotation of the polishing pad cuts the central region of the surface of the workpiece. Accordingly, the polishing tool is moved over the central area of the surface of the workpiece during the first and second polishing steps, whereby a very uniform pole can be generated across the surface.

Preferably, in the first and second polishing steps, the polishing operation is performed along the first and second polishing directions respectively completely over the surface of the workpiece. Along the first and second polarization direction, the surface of the workpiece is accordingly polished completely. This has the advantage that even edge regions along the first and second polishing direction are polished. In this embodiment, the entire or only part of the surface to be polished of

Workpiece polished.

Preferably, in the first and second polishing step, the entire surface of the workpiece to be polished can be polished in each case. According to a preferred embodiment, it is provided that the first polishing direction and the second polishing direction extend at an angle of 90 ° or 180 ° to each other. According to the invention, it has been found that it is possible to produce a particularly uniform gloss distribution and a particularly slight polishing shadow when the first and second polishing directions are perpendicular to one another or opposite to each other.

According to one embodiment, it is provided that the first and second

Polishing direction do not run at a predetermined angle to each other, but each be determined depending on the gloss distribution after performing the first polishing step. In particular, it can be provided that after the first polishing step, the gloss distribution on the

Surface is detected and the second polishing direction is determined depending on the detected gloss distribution.

According to a development of this inventive concept, it can be provided in particular that the gloss distribution is detected by a sensor, particularly preferably by at least one optical sensor. The sensor is designed to detect the topography of the surface polished by the first polishing step, in particular to detect the optical

Appearance or the gloss distribution on the polished surface after performing the first polishing step.

It can be provided that the second polishing direction is determined or controlled by a control as a function of the topography or gloss distribution detected by the sensor on the surface polished by the first polishing step. For example, can be provided be. a control in dependence on the gloss distribution detected by the sensor after the first polishing step controls a positioning means for repositioning the workpiece after the first polishing step such that the workpiece is repositioned by the positioning means after the first polishing step such that the polishing direction at the second pole The step proceeds in a different direction determined by the controller than in the first polishing step. The positioning center] can be, for example, the positioning means described above.

The gloss distribution on the surface of the sensor detected by the sensor

Workpiece after the first polishing step can be used as a data signal to the

Control be forwarded. Depending on this received data, the controller may send a control signal for repositioning the workpiece to the positioning means.

According to one embodiment, it is provided that the gloss distribution detected by the sensor is compared with gloss distributions stored in a database, and the second polishing direction is dependent on this

Comparison is determined. It can be provided that for each deposited in the database gloss distribution, a second polishing direction is set, in particular, such a second polishing direction is determined by an optimal polishing result is expected, so after the second polishing step less visible course of the gloss distribution and the polish shade. It is preferably provided that by a

Data processing device, the brightness distribution detected by the sensor compared with the deposited in the database gloss distributions and the deposited gloss distribution is determined, the detected

Gloss distribution is closest to or most similar. The second polishing direction is then dependent on this deposited gloss distribution fixed second polishing direction set.

It can be provided that the control in dependence of the determined by the data processing device second Pol eierrichtung such a control signal for repositioning the

Send workpiece to the positioning that the workpiece is repositioned so that in the second polishing step a polishing process along this second polishing direction is performed on the surface of the workpiece.

According to the invention, it can be provided that the method is repeated as often as desired. Thus, for example, two or more second polishing steps may be performed in which a polishing operation is performed along second polishing directions on the surface of the workpiece, respectively, wherein the first polishing direction and the plurality of wide polishing devices each extend in different directions.

The invention further provides an apparatus for carrying out the method described herein. Such a device may in particular comprise the following features:

a first polishing tool and a second polishing tool by which a surface of the workpiece is respectively polishable;

Transport means by which the workpiece is each transportable relative to the first and second polishing tool such that the surface of the workpiece by the first polishing tool in a first polishing step along a first Poiierrichtung is polierbar and by the second

Polishing tool in a second polishing step along a second

Polishing direction is polishable;

Positioning means by which the workpiece after the first polishing step and before the second polishing step is repositioned such that the Polishing direction in the second polishing step in a different direction than in the first polishing step.

The device according to the invention may each comprise one or more first and second polishing tools. Furthermore, one or more workpieces may be transportable by the means of transport.

The means of transport and the polishing tools of the invention

Device can, as described above, be formed. In particular, the means of the device can be designed such that they can carry out the steps described for carrying out the method according to the invention.

In particular, the device according to the invention in the form of a

Polishing be provided for polishing porcelain stoneware tiles.

The device according to the invention may further comprise a sensor for detecting the Glanzvertei ment on the surface of the polished workpiece after the first polishing step. As described above, the sensor can be designed to detect the topography, in particular to detect the gloss distribution of the surface. It can be provided that the

Positioning means in dependence of the data detected by the sensor, regarding the topography or gloss distribution, is controllable. For example, provision can be made for the positioning means to be controllable in dependence on the data detected by the sensor such that the workpiece is repositionable by the positioning means after the first positioning step such that the polishing direction in the second polishing step is in another direction (determinable by the controller) runs as in the first polishing step. The gloss distribution on the surface of the sensor detected by the sensor

Workpiece after the first polishing step can as Datenigna] to the

Control be forwarded. The controller can be designed such that it sends a control signal for repositioning the workpiece to the positioning means as a function of this received data.

Further features of the invention will become apparent from the figures, the

associated figure description and the dependent claims.

All features of the invention may be combined individually or in combination, as desired.

An embodiment of the invention will be explained in more detail with reference to the following description of the figures.

It shows, each highly schematized,

FIG. 1 shows an exemplary embodiment for carrying out the

inventive method on a device according to the invention and

Figure 2 shows the gloss distribution of porcelain stoneware tiles after the first and second polishing step.

The inventive device shown in Figure 1 for carrying out the method according to the invention is in its entirety with the

Reference numeral 1 marked. Figure 1 shows the device 1 in a view of the device 1 from above. The device 1 comprises a Transport means in the form of a conveyor belt 3, the upper belt visible in Figure 1 moves in Figure 1 in the direction of arrow P from left to right.

The device I further comprises a first polishing tool 5 and a second Poi ierwerkzeug 7. On its side facing away from the viewer, the first polishing tool S and the second polishing tool 7 each have one

Pol ierscheibe (not visible in Figure 1) with an annular polishing surface. The polishing wheels are each rotatable about a plane perpendicular to the plane of rotation.

The first polishing tool S and the second polishing tool 7 are arranged at a distance from each other so oberseiti g of the conveyor belt 3 that they transported the surface of 2 on the conveyor belt 3

Porcelain stoneware tiles 19 can polish.

In the area between the first polishing tool 5 and the second

Polishing tool 7, an optical sensor 9 is arranged above the conveyor belt 3. The optical sensor 9 is designed to detect the gloss distribution of porcelain stoneware tiles 19 transported on the conveyor belt 3.

In the area between the optical sensor 9 and the second

Polishing device 7, a positioning means 1 1 in the form of a turntable 1 1 is arranged. The turntable 1 1 is formed such that it on the

Transport belt 3 can reposition transported porcelain stoneware tiles.

The position in which the turntable can be repositioned 1 1 porcelain stoneware tiles, by a controller 1 3 controllable. For repositioning a located on the turntable 1 1 porcelain tile 19 sends the controller 13 a S buzzer signal 15 for repositioning the porcelain stoneware tile 19 in a position determined by the controller to the turntable 1 first

The turntable 1 1 is designed such that it is controllable in dependence of the data collected by the optical sensor 9, concerning the gloss distribution on the surface 2 1 of the porcelain stoneware tiles 19. For this purpose, the relevant data 1 7 can be forwarded by the optical sensor 9 to the electronic controller 13. The controller 1 3 comprises a data processing device, in the present case a microcontroller which processes the data 1 7 and in response to the data 1 7, the control signal 1 5 to

Positioning of a tile 19 to the turntable 1 1 passes.

An embodiment of the method according to the invention can be carried out on the device 1 as follows:

At the inlet side, in Figure 1 left end of the conveyor belt 3 porcelain stoneware tiles 1 9 are placed on this. By the conveyor belt 3, the tiles 1 are first transported to the first polishing tool 5 along such that the surface 2 1 of the tiles 1 9 in a first

Polishing step is polished by the first polishing tool 5. On the basis of the transport direction P of the conveyor belt 3, the tiles 19 are polished by the first polishing tool 5 in each case along a first polishing direction P I.

By the first polishing tool 5, the tiles 19 get in the first

Polishing step an uneven gloss distribution, indicated by the line G l.

During further transport of the tiles 1 9 through the conveyor belt 3 they are guided along the optical sensor 9 along. The optical sensor 9 detects the uneven gloss distribution G l on the surface 21 of the tiles 1 9. The acquired data 17 are from the optical sensor 9 to a

Data processing device forwarded, which is part of the controller 13. The data processing device compares the data 1 7 acquired by the sensor 9 and compares them with digital distributions stored in a digital database, to each of which an optimally second one

Polishing direction is set. The data processing device determines the deposited gloss distribution, which according to the data 1 7

corresponding gloss distribution comes closest. Subsequently, the controller forwards such a control signal 1 5 to the turntable 1 1 further that this repositioned the tile 1 9 such that they are polished by the second Pol ierwerkzeug 7 along a second polishing direction P2, which was determined by the data processing device.

After the tiles 19 have been guided along the optical sensor 9, they are supplied by the conveyor belt 3 Drehtel ler 1 1, the tiles 1 9, as described above, in response to the received from the optical sensor 9 control signal IS repositioned such that these can be polished by the second polishing tool 7 in a second polishing direction P2.

In the illustrated embodiment, the tiles 19 through the

Drehtel ler 1 1 jewei ls rotated by 90 ° and then deposited again on the conveyor belt 3 so that they then so on the second

Polishing tool 7 along that the surface 2 1 of the tiles 19 is polished by this in a second polishing step along a second polishing direction P2. Due to the rotation of the tiles 1 9 by 90 ° extend the first polishing direction PI and the second direction of polishing P2 at an angle of 90 ° to each other. When polishing the surface 2 1 of the tiles 1 by the second polishing tool 7, the surface 21 also receives an uneven gloss distribution, indicated by the dashed line G2.

Since the gloss patterns of the uneven gloss distributions G 1 and G 2 are superimposed on the surface 21 of the tiles 19, these are for the

hardly recognizable to the human eye, so that the gloss distribution on the surface 21 of the tiles 19 is substantially more homogeneous after the second polishing step has been carried out, and the polishing shadows are considerably less pronounced than after the first polishing step has been carried out.

FIG. 2 shows the appearance of the surface of tiles 101 after a first polishing step 103, after a rotation of 90 ° 105 and after a second polishing step 107 has been carried out.

Claims

claims

, A method of polishing a planar surface (21) of a brittle material workpiece (1), comprising the steps of: 1.1 polishing the surface (21) of the workpiece (19) in a first polishing step, wherein a polishing operation along a first polishing direction (FIG. PI) is performed on the surface (21) of the workpiece (19);

1.2 polishing the surface (21) of the workpiece (19) in one

second polishing step, wherein a polishing operation along a second polishing direction (P2) on the surface (21) of the workpiece (19) is performed, wherein

1.3 the first polishing direction (PI) and the second polishing direction (P2) in different directions. , The method of claim 1, wherein the workpiece (19) in the first and second polishing step in the same direction (P) is transported and repositioned after the first polishing step such that the second direction of polishing (P2) in another direction extends the first polishing direction (PI). Method according to at least one of the preceding claims, in which the first polishing direction (PI) and the second polishing direction (P2) extend at an angle v of 90 ° or 180 ° to one another. Method according to at least one of the preceding claims, in which, after the first polishing step, the gloss distribution on the

Surface (21) is detected and the second polishing direction (P2) is determined depending on the detected gloss distribution. Method according to at least one of the preceding claims, in which the gloss distribution is detected by a sensor (9). Method according to at least one of the preceding claims, in which the gloss distribution is detected by an optical sensor (9). Device for carrying out the method according to at least one of the preceding claims, comprising the following features:

7. 1, a first Poiierwerkzeug (5) and a second polishing tool (7) through which a surface (21) of the workpiece (19) is each polishable;

7.2 transport means (3) through which the workpiece (1 9) relative to the first and second polishing tool (S, 7) is transportable, that the surface (21) of the workpiece (1 9) by the first polishing tool (5) in a first polishing step along a first polishing direction (PI) is pol ierbar and by the second polishing ierwerkzeug (7) in a second polishing step along a second polishing direction (P2) polishable;

7.3 positioning means (1 1), through which the workpiece (19) after the first polishing step and before the second polishing step in such a way repositionable such that the second polishing direction (P2) is in a different direction than the first polishing direction (PI).

Apparatus according to claim 7, further comprising a sensor (9) for detecting the gloss distribution on the surface (2 1) after the first polishing step.

Device according to at least one of the preceding claims, in which the positioning means (1 1) is controllable in dependence on the data (17) detected by the sensor (9).