Method and apparatus for cleaning components manufactured in a powder bed

Abstract

Method for cleaning components (1) produced in a powder bed, wherein at least one process step (V1, V2) comprises the application of kinetic energy by linear tools (11, 21), and the movement of the linear tools (11, 21) is vertical towards the components (1) and a plurality of linear tools (11, 21) are moved alternately onto a component surface of the components (1), characterized in that in a first process step (V1) the components (1) are separated by means of lances (11) moving up and down, in a second process step (V2) the components (1) are roughly cleaned by means of chains (21) that can be lowered from above onto the components (1) and then raised again, and in a third process step (V3) the components (1) are finely cleaned by means of compressed air lances (31) arranged in a grid.

Description

[0001] The invention relates to a method for cleaning components manufactured in a powder bed and a device for carrying out the method.

[0002] The custom production of components using 3D printing is becoming increasingly important, especially for industrial applications. These processes are particularly attractive for small series production, as no tools are required for production. Another advantage is that changes to the components being manufactured can be implemented quickly. Various 3D printing processes are known. Especially with printing processes carried out in a powder bed, the problem of cleaning the manufactured component after printing arises, as the components emerging from the powder bed are unusable due to the adhering powder residue.

[0003] From an industrial perspective, there is a desire for a continuous process for cleaning components after they have left the powder bed. This continuous process should, if possible, be applicable to a wide variety of components and materials without significant changes, so that a wide variety of components can be manufactured and cleaned fully automatically within a single production line.

[0004] Various solutions for this have been demonstrated in the prior art. For example, DE 10 2017 002 448 A1 proposes a production line and a method for the automated operation of this production line. The production line comprises a conveyor belt that can be vibrated by a separating device to separate the components from one another and remove adhering powder. Furthermore, it is provided to subject the components to compressed air and / or particles for further cleaning. A disadvantage is that the cleaning performance of the proposed production lines and the associated method is insufficient, meaning that many component designs and many materials cannot be adequately cleaned.

[0005] GB 2517490 A, DE 10 2010 019 447 A1, EP 3 069 805 A2, DE 10 2017 200 382 A1, and US 2013 / 0052291 A1 each disclose methods for cleaning the interior of a component produced in a powder bed. Cleaning is performed by inserting linear tools into the interior.

[0006] US 2017 / 0144382 A1 discloses the possibility of removing powder residues adhering to the outside of components using compressed air.

[0007] DE 10 2017 206 815 A1 discloses a method in which mechanical energy is applied to components by subjecting them, for example, to an air flow or sound waves.

[0008] The invention is based on the object of proposing a method and a device for cleaning components manufactured in a powder bed, which have a significantly improved cleaning performance while at the same time being highly flexible with regard to component geometry and material.

[0009] The object is achieved by a method according to claim 1 and a device according to claim 10. Preferred developments of the invention are the subject of dependent claims.

[0010] The inventive method for cleaning components produced in a powder bed has at least one method step in which kinetic energy from linear tools acts on the components to be cleaned. The components were previously produced in a powder bed, for example by means of selective laser melting. Due to the process, a large amount of powder still adheres to the components when they leave the powder bed, which must be removed before they can be reused. According to the invention, in a first method step, the components are separated using lances moving up and down; in a second method step, the components are roughly cleaned using chains that can be lowered onto the components from above and raised again; and in a third method step, the components are finely cleaned using compressed air lances arranged in a grid.

[0011] For the purposes of this application, linear tools are tools that have a significantly greater length compared to their width and height, such as lances, nails, chains, straps, ropes, or similar. Preferably, a plurality of linear tools are arranged in a grid-like manner in a holder. The linear tools execute their movement in the direction of their length, with additional movement components in a direction transverse to the length.

[0012] According to the invention, the cleaning of the components is carried out by moving the linear tools in a vertical direction onto the components and by moving a plurality of linear tools alternately onto a component surface of the components.

[0013] The linear tools preferably move from above onto the component. The kinetic energy of the linear tools is used upon impact with the component to loosen the adhering powder. This advantageously allows the weight of the linear tools to be used for their acceleration.

[0014] It goes without saying that the weight of the linear tools and the impact speed depend on the components to be cleaned. This is another advantage of the invention, as the process can be adapted to very different components without any technical modifications to the system.

[0015] Advantageously, the method according to the invention allows both the pulse energy when the linear tools impact the component and the friction and scratching motion as they slide past the component after impact to be utilized for cleaning. Furthermore, the method is cost-effective to implement and perform and enables efficient cleaning.

[0016] In a preferred embodiment of the invention, the components to be cleaned are located on a conveyor belt during the process. This advantageously allows for a simple, continuous process.

[0017] In a preferred embodiment, the movement in the direction of the longitudinal extension of the linear tools on the component is carried out alternately, preferably at different impact speeds. Particularly preferably, a movement from above is superimposed with a lateral movement. This advantageously allows the kinetic energy of the linear tools to also act on laterally oriented surfaces of the components.

[0018] In a further preferred embodiment of the invention, the components are detected by sensors during the process. In particular, the weight of the components is recorded and their geometry is scanned. This advantageously enables an assessment of the cleaning progress. This information can also be incorporated into the system control system. If the detection reveals that the component is still heavy and therefore has a lot of adhering powder, and possibly also that the size is significantly larger than the anticipated component dimensions, the system control system can automatically trigger another cleaning cycle. By detecting the geometry of the component, it is also possible to identify local powder adhesions and treat them specifically.

[0019] In a further preferred embodiment of the invention, the powder bed is dissolved onto a conveyor belt, i.e., the components are transferred directly from the powder bed onto the conveyor belt. For this purpose, for example, the boundaries of the powder bed are moved apart and the powder bed is dissolved onto a conveyor belt. The method according to the invention can then be used to separate the components on the conveyor belt. Advantageously, this allows both the separation of components that are connected after the manufacturing process and an initial rough cleaning of the components to be achieved in a single work step.

[0020] In an alternative embodiment, the components are manufactured in a powder bed within a job box, which is transferred to the conveyor belt after production and emptied there. The components remain on the conveyor belt, and the unused powder falls through or past the conveyor belt into a powder collection device, making it available again for the manufacturing process. This embodiment is advantageously very well integrated into a continuous process.

[0021] In a further preferred embodiment, the conveyor belt has holes through which dissolved powder can fall. The powder collected under the conveyor belt can, depending on its condition, be recycled or directly returned to the production process. In a particularly preferred embodiment, the conveyor belt is a grid, for example, made of steel wire. This advantageously allows almost all of the dissolved powder to be recycled, eliminating the need to clean the conveyor belt.

[0022] In a further preferred embodiment, the linear tools are chains, belts, or rigid structures. With flexible linear tools, such as chains or belts, the movement occurs from above onto the component, i.e., in a vertical direction. The kinetic energy of the linear tools acting according to the invention is then based on their weight. With one-dimensional movable chains, several of these chains are preferably arranged in a holder, rotated by 90°. Advantageously, these chains allow the sliding movement of the chains down the component to be directed.

[0023] Lances or nails are preferably used as rigid structures, the linear movement of which is guided in a holder. The lances or nails are particularly preferably pressurized with compressed air, so that they perform a hammering movement on the components, similar to the operating principle of a jackhammer. Linear tools designed as rigid structures can also perform a vertical movement; the previously mentioned lances or nails pressurized with compressed air are particularly suitable for vertical application. This also advantageously allows the lateral areas of the components to be cleaned. It is understood that rigid linear tools cannot perform a scraping or sliding movement on the component surface; rather, the cleaning effect of rigid tools is based solely on the impulse energy when they hit the component.

[0024] When linear tools are designed as belts, textile and / or plastic belts can be used. The properties of the belts depend on the components to be treated and their geometry.

[0025] In a further preferred embodiment, the linear tools have a structured surface, by means of which the sliding past or scratching on the component surface can be advantageously intensified.

[0026] Furthermore, the linear tools preferably have a pointed lower end with which they impact the component. This can advantageously improve the cleaning effect upon impact with the component.

[0027] In a further preferred embodiment, the linear tools are combined in one or more holders. Different linear tools can also be arranged in a single holder. Furthermore, the holders are preferably designed to be movable in and across the conveyor belt direction in order to treat surface areas of the components to be cleaned that are aligned laterally or to the front or rear in the conveyor belt direction. Particularly preferably, a device for implementing the method can also comprise a plurality of holders with different linear tools, which it automatically selects and activates depending on the components to be cleaned.

[0028] Furthermore, at least one linear tool preferably has one or more areas with a significantly increased weight. In a simple case, weights are attached to the linear tools. This also advantageously allows the effect of the linear tools to be specifically influenced and, for example, linear tools to be created that are particularly suitable for breaking up webs for separating components.

[0029] In a further preferred embodiment of the method, the linear tools exhibit high elasticity, for example, they are designed as a spiral spring or rubber band. This elasticity can advantageously be used to "bounce" the linear tools on the components, thereby achieving a high degree of cleaning. Particularly preferably, the elastic linear tools are additionally weighted and possibly excited in the range of their natural frequency.

[0030] In a particularly preferred embodiment of the method, the position of the components relative to the linear tool(s) is changed during a method step or between two method steps. This can be achieved by moving the components and / or a movement of the linear tools and / or their holders. In a simple form, the components are turned over on the conveyor belt so that the underside and top side can be treated with the linear tools. This advantageously makes it easy to clean the entire component. The position of the components can be changed, for example, by a robot or by prior art reversing devices on the conveyor belt. Particularly preferably, the position change of the components on the conveyor belt is combined with a position change of the linear tools and / or the holders above the component.This advantageously allows for very targeted cleaning and also very rapid access to the areas to be cleaned, thus optimising the time required for the process.

[0031] In a further preferred embodiment of the method, at least one further method step comprises the application of compressed air, blasting media, or local post-treatment. These method steps preferably take place after the linear tools have been applied. The compressed air can be supplied to the entire component using a plurality of lances. Particularly preferably, the lances are adjustable in their distance from the component surface and can thus adapt to the component contour. The component contour was determined using the aforementioned sensors.

[0032] The same applies to treatment with blasting grit. However, it should be noted that blasting grit falls through the belt along with the loosened powder material and must first be separated before reuse.

[0033] With the method according to the invention, any blasting material can be used, the selection being made with regard to the properties of the component to be cleaned.

[0034] Local post-treatment is preferably performed as the final step of the cleaning process. The component to be cleaned is held by a robot and targeted at specific areas, for example, with compressed air or blasting media. However, post-treatment is disadvantageous because the significant time required slows down the continuous overall process. Therefore, it is highly desirable that the cleaning is already complete through the previous process steps.

[0035] This makes it particularly advantageous to implement a fully automated process for cleaning components from a powder bed. Sensors can be used to track the cleaning progress, and the design of the individual cleaning steps can be adjusted. Sensors for determining the weight and / or size of the components are particularly preferably installed after each process step for process control purposes. The collected information is forwarded to a control unit, which evaluates it and optimizes the cleaning process. This can be achieved, for example, by activating additional holders with linear tools. Such a system is advantageously very flexible and capable of adapting to the cleaning of different components.

[0036] The device according to the invention for implementing the method according to the invention has at least one conveyor belt for transporting the components to be cleaned. This conveyor belt is preferably permeable to the adhering powder that is to be removed during the cleaning process. A collection device for the removed powder is advantageously provided below the conveyor belt. A reprocessing device for the collected powder is arranged downstream of the collection device, which then preferably makes the reprocessed powder available again for the manufacturing process.

[0037] In addition, the device according to the invention comprises a cleaning device with linear tools that are moved alternately in the direction of their linear extension toward components on the conveyor belt. The impact of the linear tools on the component surface, possibly in conjunction with the alternating movement of the linear tools on the component surface, achieves a very effective cleaning effect without damaging the component.

[0038] In a preferred embodiment of the device, a plurality of linear tools are arranged in a grid pattern in a holder. Particularly preferably, the device has several of these holders, which can be activated and deactivated by the system control system. This advantageously achieves a high degree of flexibility of the device, as it can clean a large number of component areas simultaneously and in a targeted manner with linear tools.

[0039] Furthermore, the linear tools and / or the holders are preferably arranged so as to be movable in and against the conveyor belt direction as well as laterally thereto. The holders and / or linear tools are thus freely positionable in an area above the component. This advantageously makes it possible to specifically clean certain component areas using the linear tools. When using several linear tools and / or several holders, each linear tool and / or each holder is preferably freely positionable above the component and can thus be assigned to an area of ​​the component surface to be cleaned. For this purpose, the holders and / or the linear tool are positioned and activated above the area to be cleaned.In addition, the movement of the linear tools and / or holders can also be advantageously used to improve the cleaning performance, for example by alternately performing a movement transverse to the conveyor belt direction and the associated scratching of the linear tools on the component surface additionally cleaning it.

[0040] Furthermore, the device preferably comprises a cleaning device directly after the components are transferred from the powder bed to the conveyor belt, which periodically lowers and raises linear tools onto the components, thus separating them. Particularly preferably, the linear tools are rigid, for example, lances or nails.

[0041] In a further preferred embodiment, a rough cleaning device is arranged downstream of the separation cleaning device, in which linear tools also act on the components alternately. The linear tools in the rough cleaning station are preferably chains.

[0042] Furthermore, additional cleaning stations are preferably arranged downstream of the rough cleaning station. These can act on the components pneumatically and / or subject them to blasting media.

[0043] A post-treatment station is preferably provided as an additional cleaning station, where targeted local treatment of areas still containing a large amount of powder is carried out. This post-treatment station can be implemented, for example, by a robot that subjects the areas to be cleaned to pneumatic treatment or blasting with abrasive material.

[0044] In a particularly preferred embodiment, the device has a sensor system for scanning the component geometry and / or determining the component weight. Based on this data, the cleaning progress can advantageously be determined. Such a sensor system is particularly preferably arranged at multiple positions, for example, after each cleaning station.

[0045] In a further preferred embodiment, the device comprises devices for changing the position of the components on the conveyor belt. In a simple embodiment, these devices are turners that simply turn the components on the conveyor belt. Alternatively, robots can also be provided that turn the components or move them in such a way that areas still to be cleaned are accessible to the cleaning tools.

[0046] Particularly preferably, the devices for changing the position are arranged in such a way that each cleaning step acts on as much of the component surface as possible.

[0047] The device preferably also includes a control unit. The control unit receives the data determined by the sensors. Based on this data, the control unit can monitor the cleaning process and optimize the overall process by activating or deactivating additional cleaning stations.

[0048] Further preferred embodiments of the invention emerge from the remaining features mentioned in the subclaims.

[0049] The various embodiments of the invention mentioned in this application can be advantageously combined with one another, unless otherwise stated in the individual case.

[0050] The invention is explained in more detail below in exemplary embodiments with reference to the accompanying drawing, which shows a schematic diagram of an apparatus for carrying out the method according to the invention.

[0051] Fig. Figure 1 shows a schematic diagram of an embodiment of the method according to the invention. Components 1 are manufactured by selective laser melting in a powder bed. The components 1 are then transferred directly from the powder bed (not shown in the figure) onto a conveyor belt 2. The conveyor belt 2 is designed as a metal grid through which powder that comes loose during cleaning falls and collects in a residual powder collection container 3 located below. The residual powder collection container 3 is regularly emptied fully automatically, and the powder is fed into a recycling system that separates any powder that sticks together. The powder is then reused in the manufacturing process.

[0052] In a first process step, the separation V1 of the components 1 takes place by means of lances 11 moving up and down. These act on the components 1 by means of their weight and separate adhering components 1. The lances 11 are additionally pressurized with compressed air, whereby a hammering movement of the lances 11 is achieved.

[0053] In a second process step, the rough cleaning V2 of the components 1 takes place. Here, chains 21 are lowered from above onto the components 1 and raised again so that the chains 21 knock off adhering powder when they hit the components 1 and remove even more powder by scratching along the surface of the components 1.

[0054] In a third process step, a first fine cleaning step V3 is performed using compressed air. This is applied to the components 1 via compressed air lances 31 arranged in a grid. The geometry of the components 1 was scanned in advance by sensors, so that the compressed air lances 31 are aligned so that each compressed air lance 31 is positioned close to the component 1. This improves the effectiveness of the compressed air.

[0055] In a fourth process step, the second fine cleaning step V4 is carried out using abrasive blasting media. For this purpose, compressed air lances with blasting media 41 are brought to the components 1 in a similar manner to the third process step. From this process step onward, a different collection container is located beneath the conveyor belt 2, as a mixture of blasting media and material powder now falls through the conveyor belt 2.

[0056] In a final process step, local post-treatment V5 is performed. During this process, the components are held by a robot 51 and positioned opposite a single lance with blasting media 52. The position of the areas of components 1 to be reworked was previously determined using sensors.

[0057] After completing these five process steps, the components 1 are cleaned so that they are suitable for further processing. List of reference symbols 1 component 2 conveyor belt 3 residual powder 11 lances 21 chains 31 compressed air lances 41 compressed air lances with blasting media 51 robots 52 single lance with blasting media V1 separation V2 rough cleaning V3 first fine cleaning V4 second fine cleaning V5 local rework

Claims

[1] Method for cleaning components (1) produced in a powder bed, wherein at least one method step (V1, V2) comprises the action of kinetic energy of linear tools (11, 21), and the movement of the linear tools (11, 21) takes place in a vertical direction on the components (1) and a plurality of linear tools (11, 21) are moved alternately on a component surface of the components (1), characterized by in that in a first process step (V1) the components (1) are separated by means of lances (11) moving up and down, in a second process step (V2) the components (1) are roughly cleaned by means of chains (21) which can be lowered onto the components (1) from above and raised again, and in a third process step (V3) the components (1) are finely cleaned by means of compressed air lances (31) arranged in a grid. [2] Method according to claim 1, characterized bythat the linear tools (11, 21) are chains, belts or rigid structures. [3] Method according to one of the preceding claims, characterized by that at least one linear tool (11, 21) has one or more areas which have a significantly increased weight. [4] Method according to one of the preceding claims, characterized by that the components (1) are arranged on a conveyor belt (2). [5] Method according to claim 4, characterized by that the conveyor belt (2) has recesses. [6] Method according to one of the preceding claims, characterized by that during a process step (V1, V2, V3) the position of the components (1) relative to the linear tool (11, 21) is changed. [7] Method according to one of the preceding claims, characterized by that at least one further process step (V4, V5) comprises the action of compressed air, blasting material or local post-treatment. [8] Method according to one of the preceding claims, characterized by that data of the components (1) such as weight and / or geometry are recorded during the process. [9] Method according to claim 8, characterized by that the determined data of the components (1) are transmitted to a control unit and the control unit controls the cleaning process by taking into account the data of the components (1). [10] Device for carrying out a method according to one of the preceding claims, characterized by that the device has at least one cleaning station in which linear tools (11, 21) act on the components (1) to be cleaned.

Images