BLASTING DEVICE

Abstract

Abrasive device (10) for matting a workpiece by means of a suitable abrasive, which flows out in a cabin (12) of the device during the operation by means of a blast nozzle under pressure, wherein the device has a workpiece holder (20) which comprises a support frame (24) held in a rotary mount (22), on which holding means for fixing a workpiece are provided, which holding means are movably attached to the support frame so that when the support frame (24) is pivoted in the rotary mount (22), a workpiece to be processed can be rotated and / or pivoted about a selectable axis of rotation by adjusting the position of the respective holding means in the cabin space, characterized in that the support frame (24) of the workpiece holder (20) held on rotary mounts (22) has support arms (26) projecting radially from the axis of rotation, which are connected to a cross member (28) of the support frame.a radial support (30) of the support frame, corresponding to the length of the support arms (26), is provided in the center, and at least one positionable saddle support (32) and at least one positionable clamping arm (34) of the support frame with a gripper (36) are held by means of this support frame.

Description

[0001] The present invention relates to the field of surface treatment using abrasive media, also known by the general term "sandblasting." Such a process serves to clean and mat surfaces, and in particular metal surfaces. The process thus fulfills a dual function, insofar as the surfaces are cleaned and also roughened for subsequent painting or coating. The blasting effect is achieved by the aforementioned abrasive media, such as corundum, garnet sand, slag, cast steel, or glass beads, which impact the surface to be treated at high speed. In this respect, a surface structure can be determined by the choice of abrasive media used, with the choice of the degree of cleaning also depending on the subsequent surface protection required. During the blasting process, a powerful jet of air is generated and used to accelerate the abrasive media.The required air pressure is generated by special compressors, and the powdered or granular blasting media can be added either dry or mixed with water from a collection container. For example, a sand-air mixture is blasted at high speed onto the surface in question via a hose and nozzle system. Surface particles are dislodged by the abrasive blasting action and subsequently removed. This process thoroughly cleans surfaces of contaminants, rust, paint, or scale. Depending on the process duration, choice of blasting media, and pressure, various degrees of cleaning can be achieved.

[0002] In most cases, painting a surface requires mechanical sanding to create a roughness depth and thus ensure good paint adhesion. This process is often referred to as "matting" the surface. Depending on the processing time, choice of blasting media, and pressure applied, different roughness depths can be achieved to achieve the desired matting effect.

[0003] Corresponding sandblasting systems are known from documents DD 239 977 A1, WO 00 / 27592 A1, CN 113043513 A and DE 197 34 939 C2.

[0004] Due to the above aspects, sandblasting is a popular technique, particularly for parts or components in the automotive industry that are to be painted. Such parts can be quite large. When conventionally sandblasting such automotive parts, like a bumper, these are typically blasted in a large, walk-in booth on skids. The kinetic energy of the particles during blasting creates a large amount of dust in all directions, which can then cause unwanted contamination in the subsequent painting process. Therefore, a closed booth is necessary for blasting so that the blasting media, dust, and other contaminants can be extracted and do not escape.The booth size must be such that the operator can walk all the way around the bumper, which is positioned in the center of the booth, to work on it along its entire length ("from ear to ear") as well as on the top and bottom. This is problematic because the distance between the blast nozzle and the workpiece should generally be between 20 and 50 cm. A car bumper can also be up to 200 cm wide. This results in typical booths being enormous in size and taking up a lot of space in the paint shop. With increasing booth size, the extraction system, substrate return, substrate preparation, filter units, and much more of the system technology must also be correspondingly large. This, in turn, requires large volumes of air for the system to operate, which is associated with high energy consumption. Furthermore, the operator must wear a protective suit including a helmet with a breathing apparatus.This is time-consuming in terms of preparation time before the system is operational. Walk-in blast cabinets like these require large doors to allow the large workpieces to be brought inside. Due to the large volume of air within the blast cabinets, the extraction system also needs a certain amount of time to sufficiently minimize the dust load inside the cabinet. If the doors are opened prematurely, blasting media and dust can escape into the workshop, exacerbating the contamination problem.

[0005] The invention is therefore based on the objective of improving the conventional blasting cabinets described at the outset, in particular for paint preparation and especially for elongated workpieces, such as motor vehicle bumpers, fenders, sills, aluminum rims or other medium-sized workpieces with the associated blasting media processes.

[0006] This problem is solved by a device according to claim 1. Advantageous embodiments are evident from the respective dependent claims.

[0007] The starting point of the task is therefore to achieve almost complete blasting of different workpieces in a blast cabinet that is as small as possible, whereby a suitable distance between the blast nozzle and the workpiece surface can be maintained continuously over the entire surface of the workpiece to be processed.

[0008] The basic concept of the invention can be formulated as an abrasive device for cleaning and / or matting a workpiece, in which a workpiece holder is provided in the device's cabin to hold the workpiece. This holder also allows the workpiece to be repositioned within the cabin, ensuring that, firstly, the entire surface of the workpiece to be treated is accessible to the blasting nozzle, and secondly, that the appropriate distance between the blasting nozzle and the surface being treated can be maintained. The phrase "entire surface to be treated" does not necessarily refer to the entire surface of the workpiece, but only to the portion of the surface to be matted. A workpiece such as a bumper, for example, does not need to be matted entirely, because its surface to be painted often only comprises the outer surface of the bumper.

[0009] According to the invention, the workpiece holder in the cabin is rotatable in at least one axis of rotation. A workpiece fixed in or on the workpiece holder can thus be rotated or pivoted during processing, thereby maximizing the surface area accessible for processing in relation to an unchanged nozzle position of the blasting device.

[0010] When a workpiece is rotated in the blast cabinet, a mathematically known envelope is generated, which reflects an imaginary body of revolution. According to the invention, this body of revolution should be kept as small as possible in order to achieve a fundamentally small cabinet size. For this purpose, the invention advantageously provides that the mounting parts of the workpiece holder, on which the workpiece is held, are adjustable in their position, so that the workpiece can be rotated about an approximately freely selectable axis of rotation centrally located in the cabinet.

[0011] The device according to the invention is characterized in that it has a workpiece holder comprising a support frame held in a rotary mount, on which holding means for fixing a workpiece are provided. These holding means are movably attached to the support frame so that, when the support frame is pivoted in the rotary mount, a workpiece to be machined can be rotated or pivoted around the selectable axis of rotation in the cabin space by adjusting the position of the respective holding means. In other words, the workpiece holder can be adjusted so that, for example, the workpiece to be machined can be positioned with its longitudinal axis parallel to the longitudinal axis of the cabin, so that during rotation, the workpiece is rotated as centrally as possible in the cabin space around its own longitudinal axis.

[0012] According to an advantageous embodiment, a rotary mounting is provided at each of the lateral ends of the blasting device—that is, at the ends of the cabin's longitudinal axis—within the cabin, either on or near its side walls. The workpiece holder is mounted in these rotary mountings. The workpiece holder itself, mounted on the rotary mountings, comprises a support frame that allows the workpiece to be fixed with its longitudinal axis as coaxially as possible between the mounting points. The workpiece itself can then be rotated with a minimal envelope, i.e., with a minimal swept area resulting from the rotation, by rotating the workpiece holder and the support frame.This creates an advantageous condition that, with the blast nozzle remaining in its position within the cabinet, a nearly uniform distance is maintained between the blast nozzle and the workpiece surface being treated. Furthermore, this allows for a minimization of the blast cabinet's dimensions. This distance between the blast nozzle and the surface being treated is also maintained if the blast nozzle is moved linearly along this longitudinal axis through the cabinet space.

[0013] According to an advantageous embodiment, the support frame of the workpiece holder, which is held on the rotary mounts, has support arms projecting radially from each of the rotary mounts and from the axis of rotation. These support arms are connected to a crossbeam extending the length of the cabin. A radial support for a fixing frame, approximately corresponding to the length of the support arms, is provided on the crossbeam approximately in the center. This fixing frame comprises at least one seat post and at least one clamping arm, both held in a slide guide.

[0014] The support arms are positioned as far out as possible on the sides of the blasting cabinet at its longitudinal ends, so that the workpiece can be completely fixed between these support arms, thus preventing a rotating workpiece from being obscured by the support arms during processing and ensuring that the blasting process taking place between the support arms is not disturbed.

[0015] The seat post serves to initially place the workpiece upon its insertion into the blasting cabinet, and subsequently to secure it using the clamping means provided on the clamping arm. According to an advantageous embodiment, at least two seat posts and at least two clamping arms are provided along the crossbeam, each adjustable in at least two spatial directions within its slide guides. This enables reliable fixation of any three-dimensional workpiece of varying shapes, ensuring that it is securely held during rotation within the blasting cabinet. Alternatively, according to an advantageous embodiment, ball joints can also be provided, allowing each seat post or clamping arm to be freely positioned in three-dimensional space.

[0016] Advantageously, the fixing devices on the clamping arms are spring-loaded clamping grippers. Furthermore, it is advantageous to provide free positioning of the clamping grippers on the clamping arms in three spatial dimensions. For this purpose, the clamping arms, which can be moved in slides, can be combined with grippers held on ball joints.

[0017] With the above design concept, the cabin size could be significantly reduced compared to conventional cabins. Large workpieces, such as vehicle bumpers, can now be blasted across their entire surface, including any undercuts. Due to the compact size of the device and its enclosure for the workpiece, the required air volume for the blasting process and the amount of particles are lower. This translates into significant energy savings for the extraction system, the filter system, and the substrate recirculation. The smaller air volume within the system allows for faster extraction and cleaning, thus also reducing contamination from dust and other contaminants generated during the blasting process.

[0018] The device according to the invention provides that the operator can move freely outside the machine body along the entire length of the workpieces, such as a vehicle bumper, without interrupting the blasting process, and is able to guide the blasting nozzle. The matting can be carried out along its entire length ("from ear to ear") without removing or repositioning the operator's hands on the blasting cabinet. The invention enables this procedure through the rotation and adjustment of the seat supports and clamping arms of the workpiece holder, even for curved workpieces such as vehicle bumpers. The workpiece holder is thus designed to accommodate the respective workpiece in such a way that the workpiece can be rotated coaxially and centrally to the axis connection of the lateral pivot points, so that the envelope, i.e., the space required when rotating the workpieces, is as small as possible.paint over the smallest possible area.

[0019] In an advantageous embodiment, the workpiece holder has a rotational stop. When the workpiece holder rotates, this stop rotates with it and defines the maximum envelope. When fixing the workpiece in the workpiece holder, care must be taken to ensure that the workpiece does not protrude beyond the rotational stop. The workpiece is therefore fixed in the same plane as the rotational stop. This allows it to be seen even when clamping the workpiece that the envelope resulting from the workpiece's rotation will be smaller than the maximum envelope of the rotational stop. In other words, it can be seen before the workpiece holder and workpiece begin to rotate that the workpiece will not collide with any fixture element in the cabinet. The rotational stop thus prevents the workpiece from rubbing against the machine body uncontrollably during rotation.can get stuck.

[0020] Advantageously, the workpiece holder according to the invention can be provided with additional adapters in order to clamp and hold the range of workpieces, such as rims, fenders, sills, but also other workpieces for industrial use, in order to subject them to almost all-round machining.

[0021] The workpiece holder can advantageously be rotated electrically by means of motor force in both directions of rotation relative to the longitudinal axis of the device.

[0022] According to an advantageous embodiment, the workpiece carrier is mounted in a tilting position, with each end position of the tilting process defining a "processing position" and a "loading position." In practice, this means that for loading, the workpiece holder is moved to a forward position facing the cabin opening to allow good access for positioning and securing a workpiece. Before blasting, the workpiece holder is then tilted backward into the "processing position," thereby achieving the necessary distance between the workpiece and the blasting media nozzle. From a design perspective, this tilting process is provided, according to an advantageous embodiment, such that the rotary mounts in which the workpiece holder is supported on both sides are arranged in radial arms, the opposite ends of which are each mounted on rotary bearings in the floor area of ​​the blasting cabin.This allows the rotary fixtures to be pivoted along a circular arc within the blasting cabinet. This pivoting movement can advantageously be limited by a stop, thus defining the two respective end positions of the tilting process as the aforementioned "processing position" and "loading position".

[0023] The invention advantageously provides that the tilting device can be operated automatically. For this purpose, at least one corresponding pneumatic cylinder is provided, which automatically moves into the forward loading position when the machine cover is opened. When the cover is closed, the pneumatic cylinder automatically moves the workpiece holder into the machining position, for example, by pressing a button.

[0024] According to an advantageous embodiment, the device has a cabin cover that includes a continuous viewing window along the longitudinal direction of the device, so that a worker has a view of the workpiece from any position along the longitudinal axis of the device. Even more advantageous is a cabin cover that also extends over the side walls of the device. A viewing window installed therein then extends equally over the side walls of the cabin cover.

[0025] The cabin lid can be advantageously pivoted upwards as a single component, completely opening the cabin interior from the front and sides. This allows for quick and easy loading and unloading of workpieces. Pneumatic cylinders or gas springs positioned on the respective side walls of the cabin lid can provide beneficial assistance in raising and lowering the lid.

[0026] According to a further advantageous embodiment, an ergonomically positioned hand grip is provided in the cabin lid for guiding a blast nozzle from outside the device and along the entire longitudinal axis of the device and along the side walls of the cabin lid, past the viewing window. Such a hand grip can advantageously be equipped with a brush guard to protect against escaping matting substrate.

[0027] The nozzle is guided by a special device that allows the operator to grip and precisely control the blast nozzle, similar to a paint gun. The blasting process is advantageously activated by a safety-monitored hand lever on this device. An operator outside the blasting cabinet can thus guide the blast nozzle gun inside the cabinet with one hand using the aforementioned hand grip.

[0028] According to an advantageous embodiment, an axis system is located above the device. This allows, among other things, the further development of an automated process, for which the invention provides that, instead of manual blasting by an operator, automated processing by a robot can also be carried out, thereby utilizing the advantages of the existing rotary device of the workpiece holder as an automation axis. In an advantageous further development, this embodiment is complemented by an equally automated blasting nozzle in the cabin. Ultimately, the blasting process can thus be carried out fully automatically by means of an industrial robot or axis system.

[0029] According to a further advantageous embodiment, the device according to the invention has a collection tray for the blasting media that empties into a flat conveyor system. This allows the blasting media to be selectively recycled and reused. In an advantageous embodiment, the collection tray has a surface sloping at an angle from the horizontal, so that the matting substrate can automatically reach the flat conveyor below by gravity.

[0030] Furthermore, according to an advantageous embodiment of the invention, suitable maintenance hatches are provided, allowing access to components of the plant technology from the side and rear of the device. This allows the device – except during machine maintenance – to be positioned directly against a wall. This saves additional space during installation.

[0031] Overall, the device according to the invention is not only particularly well suited for matting vehicle bumpers, as described above. Rather, the invention also generally encompasses the use of this system for preparing elongated components for painting, such as vehicle side skirts. Furthermore, other add-on parts, such as alloy wheels and other vehicle add-on parts, can also be matted with the device according to the invention. Many other carbon fiber components and other industrial applications are also conceivable. Finally, the term "workpiece to be painted" used within the scope of the invention includes not only sheet metal and aluminum components but also plastic components, such as fenders and spoilers.

[0032] The system is designed specifically for use with an eddy current rotary process for the microabrasive matting of the surface in question. The microabrasive eddy current process results in significantly improved paint adhesion during subsequent recoating. This is particularly true for areas of bumpers that are difficult or impossible to access manually, or for tight spaces in alloy wheels. This is achieved through a considerably stronger bond between the new paint layer and the treated substrate. Tests using the paint cross-cut method have demonstrated this. The microabrasive eddy current process and the resulting improved paint adhesion also provide significantly better corrosion protection. The microabrasive eddy current process features a swirl body positioned before the nozzle inlet, with, for example, four angled bores that are advantageously inclined at 12° to 20° to the flow axis.The micro-jet particles flow at an angle through the aforementioned angled bores into the nozzle. The nozzle is conically flared towards the outlet, so that when compressed air is applied, a single, flared, and rotating vortex cone is formed, resulting in optimal particle distribution across the entire cross-section of the rotating jet cone. The resulting rotational effect of the airflow guides the microfine micro-jet particles almost tangentially across the surface to be matted. This reduces the negative impact of the blasting medium and prevents any negative marks on the paint or coating surface. The overall result is a uniformly matted surface that ensures optimal mechanical adhesion for recoating. A Venturi or Laval nozzle type can be used, preceded by a swirl-element attachment.An advantageous air pressure is approximately 1.5–2 bar. The nozzle distance to the object is variable depending on the prevailing air pressure, but is generally preferably 20–50 cm. Particles with a hardness of 4–10 (Moh scale) are advantageously used as the blasting medium. The grain shape is advantageously angular or crystalline. Preferred grain sizes are 50–200 µm.

[0033] The invention will now be described in more detail in one embodiment, as shown in the accompanying drawings.

[0034] The drawings show Fig. 1 a blasting media device according to the invention in a side and front view as well as in a top view; and Fig. 2 a workpiece holder according to the invention in front and side view as well as in top view.

[0035] The in Fig. The dimensions of the blasting device 10 shown are clearly visible in the illustration with the operator. Top left in Fig. Figure 1 shows the blasting device 10 with the cabin lid 14 partially open. The cabin lid can be pivoted further upwards, allowing full access to the cabin interior from above. The cabin lid extends over the entire front longitudinal side of the blasting device and also over its respective side walls. The technical components of the blasting device are mounted on the rear housing wall. These include, among other things, an extraction system 40 and a filter system 42. A viewing window 16 is provided in the cabin lid 14, allowing a view into the cabin even when the lid is closed. This viewing window 16 advantageously extends over the entire length of the blasting device and over the angled side walls of the cabin lid.

[0036] Below the viewing window 16 is a hand opening 18. This extends parallel to the viewing window along the entire length of the blasting media device and also into the angled side walls of the cabin lid 14. The hand opening 18 includes a brush guard around its perimeter, which prevents the blasting media from escaping. Using the hand opening 18, an operator can guide a blasting media nozzle inside the cabin with the cabin lid 14 closed.

[0037] The blast nozzle (not shown) itself is integrated into a nozzle gun (not shown), which has a hose connection at one end for supplying the abrasive, with the nozzle located opposite at the other end. The abrasive is discharged via a pistol-like trigger. In the case of an eddy current process, a swirl body with, for example, four angled bores is positioned in front of the nozzle opening. These bores advantageously have an inclination of 12° to 20° to the flow axis. The micro-blast particles thus flow into the nozzle at an angle through these angled bores. The nozzle then widens conically towards the outlet end, so that when compressed air is applied, a single, expanded, and additionally rotating eddy current cone is formed, with optimal particle distribution across the entire cross-section of the rotating blast cone.The resulting rotational effect of the airflow guides the microfine micro-jet particles almost tangentially across the surface to be matted. This reduces the negative impact of the blasting medium and prevents any negative marks on the paint or coating surface. The result is a uniformly matted surface that ensures optimal mechanical adhesion for recoating. A Venturi or Laval nozzle can be used. An advantageous air pressure is approximately 1.5–2 bar. The nozzle distance to the object varies depending on the ambient air pressure, but is generally preferably 20–50 cm. Particles with a hardness of 4–10 (Moh scale) are advantageously used as the blasting medium. The particle shape is preferably angular or crystalline. Preferred particle sizes are 50–200 µm.

[0038] Fig. Figure 2 shows the workpiece holder 20: This is located inside the cabin. The workpiece holder 20 has a support frame 24 for the workpiece to be matted. The support frame 24 includes two saddle supports 32 and two clamping arms 34. A workpiece (not shown) can be placed on the saddle supports 32 and subsequently fixed by means of the grippers 36 attached to the clamping arms. The grippers are advantageously spring-loaded and have rubberized stops to hold the workpiece gently. The assembly of saddle supports 32 and clamping arms 34 is held on the crossbeam 28 by a radial support 30. Alternatively, radial support 30s of the support frame 24, spaced apart from each other and arranged approximately centrally, can be provided on the crossbeam 28 of the support frame 24 (not shown). These radial support 30s each correspond approximately to the length of the support arms 26.Both the seatposts 32 and the clamping arms 34 are slidably mounted by means of slide guides 38. A single seatpost or clamping arm can be moved in two directions, allowing the end pieces – either a gripper 36 or a cushion of a seatpost 32 – to be positioned anywhere in a plane. The clamping arms 34, which are slidably mounted by means of slide guides 38 and have end pieces in the form of the gripper 36 or the cushion of the seatpost 32, can be arranged directly on one or more spaced-apart radial supports 30 (not shown). This allows the seatposts and the clamping arms to be adjusted to the respective workpiece in order to hold it firmly and immovably on the support frame 24. This also applies when the support frame 24 is rotated.

[0039] During rotation, the support frame 24 rotates around two rotary mounts 22 located at the respective lateral ends of the cabin. An electric motor 44 is provided on one of the rotary mounts, shown on the left side in the figure. When activated, this motor rotates the support frame 24. Two support arms 26 extend from each of the two rotary mounts 22 and are connected to each other via a crossbeam 28. As the support frame 24 rotates, the crossbeam 28 and its two support arms 26 form a rotating cylinder, which creates an envelope. Since the crossbeam 28 represents the greatest radial distance to the two rotary mounts 22, a workpiece held within the rotating cylinder is protected from becoming caught on or colliding with a component of the blast cabinet. The crossbeam thus acts as a rotational stop for the workpiece.Therefore, when clamping the workpiece on the support frame 24, care must be taken to ensure that the workpiece does not extend beyond the crossbeam 28 in the plane formed by the rotary supports 22 and the crossbeam 28.

[0040] The two support arms 26 are rotatably mounted on radial arms 46, which are positioned as close as possible to the side walls of the cabin. This allows long workpieces, such as car bumpers, to be accommodated along the entire length of the blasting cabinet.

[0041] As can be seen from the side views in the Fig.As can be seen in Figure 2, the radial arms 46 are mounted in their respective rotary bearings 48. This allows the entire workpiece holder to tilt inside the cabin. The respective end position of the tilting process defines a "processing position" and a "loading position." In practice, this means that for loading, the workpiece holder is moved to a forward position facing the cabin opening to allow good access for positioning and securing a workpiece. Before the blasting process, the workpiece holder is then tilted backward into the "processing position," thereby establishing the necessary distance between the workpiece and the blasting nozzle. This pivoting movement is limited by a stop, thus defining the two respective end positions of the tilting process as the aforementioned "processing position" and "loading position."

[0042] The features of the invention described with reference to the embodiments shown may also be present in other embodiments of the invention, unless otherwise stated or is prohibited for technical reasons. Reference symbol list: 10 Abrasive device 12 cabins 14 Cabin lids 16 viewing windows 18 manual surgery 20 workpiece holder 22 Turning shot 24 Support frame 26 support arm 28 crossbeams 30 radial beams 32 Seatpost 34 clamping arm 36 grippers 38 Slide guide 40 extraction system 42 filter system 44 Electric motor 46 Radial alarm 48 rotary bearings of a radial arm

Claims

[1] Abrasive device (10) for matting a workpiece by means of a suitable abrasive, which flows out in the operation by means of a blast nozzle in a cabin (12) of the device, wherein the device has a workpiece holder (20) which comprises a support frame (24) held in a rotary mount (22), on which holding means for fixing a workpiece are provided, which holding means are movably attached to the support frame so that when pivoting the support frame (24) in the rotary mount (22) a workpiece to be processed can be rotated and / or pivoted about a selectable axis of rotation by adjusting the position of the respective holding means in the cabin space, characterized by, that the support frame (24) of the workpiece holder (20) held on rotary supports (22) has support arms (26) extending radially from the axis of rotation, which are connected to a cross member (28) of the support frame, on which a radial support (30) of the support frame corresponding to the length of the support arms (26) is provided in the center, over which at least one positionable saddle support (32) and at least one positionable clamping arm (34) of the support frame with a gripper (36) are held. [2] Abrasive device (10) according to claim 1, characterized by , that the positioning of the seat post (32) and that of the clamping arm (34) is carried out by means of respective slide guides (38). [3] Abrasive device (10) according to claim 2, characterized by , that the slide guides (38) for the seat post (32) and for the clamping arm (34) provide a respective three-dimensional positioning in the cabin space. [4] Abrasive device (10) according to one of the preceding claims, characterized by , that the support frame (24) can be moved in the rotary mounts (22) by means of an electric motor. [5] Abrasive device (10) according to one of the preceding claims, characterized by , that the support frame (24) is held on radial arms (46), wherein the radial arms (46) are held at the opposite end of the rotary mounts (22) in rotary bearings (48), so that by pivoting the radial arms a tilting of the support frame (24) over a circular path sector in the cabin space is made possible. [6] Abrasive device (10) according to one of the preceding claims, characterized by , that the jet nozzle is arranged on a manually operated nozzle gun which can be guided inside the cabin by an operator located outside the cabin. [7] Abrasive device (10) according to one of the preceding claims, characterized bythat an industrial robot rotates the workpiece holder and / or guides the jet nozzle.

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