DE102017206815A1 - Process for cleaning a generatively manufactured part - Google Patents

Abstract

The invention relates to a method for cleaning a part (10) which is produced in a generative manufacturing method and to which flowable material (12) has remained adhering from the production process. To remove the adhering material, mechanical energy (30) is applied to the part (10) to release the adherent residues (20). The entry of the mechanical energy (30) into the part (10) is carried out using a cleaning tool (22). It is provided that for controlling the energy input into the part (10) via the cleaning tool (22) CAD data ( 40) of the part (10) are evaluated and control data (42) extracted. The entry of the mechanical energy (30) can be flexibly adapted to a specific present contour (38) of the part (10) to be cleaned.

Description

The invention relates to a method for cleaning a generatively manufactured part according to the preamble of patent claim 1.

The cleaning of generatively manufactured parts after their production plays a particularly important role in generatively produced parts, which are often made of a particulate, for example, granular or powdery material. Such parts may be, for example, sand cores. In foundries sand cores are often required in a mass production for the production of castings in large quantities. Typical industries for such castings include aerospace, medical or mechanical engineering.

The generative production of sand cores often uses a powder bed based process. The component is produced by the application of powder layers and their cohesive connection. An applied powder layer can, for example, be linked with binders at certain points by a print head and, if appropriate, solidified while supplying energy. The process is repeated iteratively. This creates a hard sand core in the powder bed, the contour of which is formed by the individual layers. Loose sand remains around the sand core, which can form residues adhering to the sand core. To remove the sand core, the solid sand core must be freed from loose sand. It has to be taken care that the sand core is not damaged. The cleaning must therefore be carried out quickly and precisely, especially in mass production.

This is conventionally often achieved through the use of industrial vacuum cleaners or compressed air stations. Also, the use of grid elements, which serve as a sieve, is used in industry.

The US 2005/0161146 A1 discloses a method in which a multi-layered part is made by thermally bonding the layers.

Furthermore, the describes US 2016/0228975 A1 a method for the additive production of a product from a powder bed. In this case, a tool used to connect different areas of the powder is moved to a further working position after the generative production in order to process the resulting product again.

The DE 10 2013 215 748 A1 describes a system in which loose powder material is sucked out of a powder bed. Here, a height-adjustable sucker is used.

In the DE 34 24 000 A1 A method and apparatus for removing sand from castings is presented. In this case, a vibrating conveyor is used, which is coupled with a Abklopfelement.

The WO 2014/009376 A1 shows another method for separating a generatively produced part from loose, unconsolidated particulate material. The loose particulate material is discharged downwardly from a space containing the manufactured part.

In the published patent application WO 2007/139938 A2 a use of perforated plates is proposed by the material particles are discharged.

In CN 205816336 U A device for removing powder residues following a 3D printing process is described. The manufactured part can be turned for this purpose with a rotatable workpiece carrier. Further, a vibration unit is provided to additionally vibrate the part.

However, the known solutions are not suitable for use in mass production. The processes require a lot of time and are hardly suitable for a diligent production. The cost of the cleaning is high, due to high energy and personnel, and thus presents a problem for mass production. Furthermore, a reworking with finer tools is often required to completely rid the sand core of the remaining loose sand. These reworks lead to further increases in production time and production costs.

The invention is based on the object to provide a method for cleaning a generatively manufactured part, with which the cleaning can be done quickly, safely and with little effort.

The object is solved by the subject matter of independent patent claim 1.

• - generative Herstellung des Teils aus einem rieselfähigen Material;
• - Entfernung von Rückständen des rieselfähigen Materials unter Verwendung eines Reinigungswerkzeug zur Zuführung von mechanischer Energie in das Teil.

A first aspect of the invention relates to a method for cleaning a generatively manufactured part, comprising the steps:

• - Generative production of the part from a free-flowing material;
• - Removal of residues of the flowable material using a cleaning tool for supplying mechanical energy in the part.

According to the invention, control data are derived from CAD data of the part and the mechanical energy is introduced into the part using the control data along a contour of the part with the cleaning tool.

The mechanical energy supplied to the part causes a separation of the flowable material still adhering to the part from the part. The mechanical energy can be supplied directly or indirectly to the part. A direct supply of mechanical energy by the cleaning tool can be done, for example, under contact of the part with the cleaning tool. This can be done for example by contacting the part with an adhesive surface or a flexible cleaning section of the cleaning tool. An indirect transfer of mechanical energy to the part can be done for example by transmission of mechanical energy through the air, for example by sound waves. A stream of air or rigid bodies accelerated in the direction of the part can also serve for the indirect transmission of the mechanical energy. Further, mechanical energy may first be transferred from the cleaning tool to a structure upstream of the part, for example a support structure holding the part, and then to the part.

The CAD data of the part may contain geometric as well as material technical information about the part. The core idea of the present invention is to use this CAD data for the targeted and effective introduction of the mechanical energy into the part along its contour. The control data, which are derived from the CAD data for this purpose, may include, for example, target specifications for a direction of action or also an intensity of the mechanical energy to be introduced. The skilled person will readily understand that the control data must be processed in a corresponding control device, which optionally accesses geometric and procedural information about a surrounding production facility. The control data are used to control the cleaning tool and possibly other resources. By using the control data, it is then ensured that the mechanical energy always acts on the contour of the part in such a way that optimum detachment of the still adhering, free-flowing material is achieved.

If the mechanical energy is applied, for example in the form of mechanical vibrations, to the contour of the part, the control data may include an amplitude and frequency of the mechanical vibrations and possibly an emission direction when the cleaning tool emits the vibrations, for example sound waves. Using the geometric and additional material information from the CAD data, the vibrations can be controlled so that effective transmission to the part is achieved. If, in another example, the mechanical energy is applied to the part by means of an air flow or also accelerated rigid bodies, then, for example, a volume flow, pressure or negative pressure, jet velocity and effective direction of the air flow or direction of flight of the rigid bodies can be contained in the control data. using the CAD data to be adapted specifically to the present part and its contour.

The method of the invention offers the advantage that the mechanical energy can always be optimally introduced into the part adapted to the present part to be cleaned. In other words, the cleaning is done while performing mechanical work on the part from the outside or along its contour. Especially in mass production, the method of the invention has the advantage that even different parts with different contours can be cleaned quickly in succession, in the form of the control data, which are derived from the respective CAD data, always adapted to the respective part mechanical energy transfer he follows. This means that even angled parts, which can also have undercuts, can be effectively and completely cleaned. The method is also particularly easy to automate. All of this was also done with very little effort, since the control data required for a particular contour of a part need only be derived once from the CAD data and then used again and again. It should be noted that, in principle, any cleaning tool known to the person skilled in the art is suitable as a cleaning tool by utilizing a cleaning principle based on mechanical energy transfer for the method according to the invention. Further embodiments will be described in more detail below.

In a preferred embodiment of the invention it is provided that the part and the cleaning tool are aligned at least once relative to each other, while the mechanical energy is introduced into the part. In other words, a relative position or orientation of the cleaning tool and the part is changed so that the entry of the mechanical energy follows the contour.

Thus, the mechanical energy can be applied by the relative orientation of a complex and changing contour of the part following the part. This leads to a significantly increased effectiveness of the cleaning of the part and correspondingly increases the flexibility of the method according to the invention.

In a further preferred embodiment of the invention it is provided that the part is at least temporarily moved in at least one translational and / or rotational degree of freedom, while the mechanical energy is introduced into the part. In other words, the part can thus be moved transversely with respect to the cleaning tool or can also be rotated about one or more spatial axes in order to make its contours accessible to the cleaning tool from different directions.

This has the advantage that the plant technical effort for implementing the method is reduced, since the cleaning tool does not have to be moved translationally itself. In this way, the method can also integrate particularly well in a series production, in which the part to be cleaned is usually moved anyway. Preferably, the part is translationally relative to the cleaning tool method and thereby additionally rotates about an axis corresponding to the translational travel direction. In this way, for the cleaning tool, the entire surface of the part can be reached without the cleaning tool itself must be moved.

In order to further increase the flexibility and effectiveness of the cleaning process, the cleaning tool can be additionally displaced or pivoted in terms of its distance from the contour of the part to be cleaned. Thus, an effective direction in which the mechanical energy is applied to the part, be adjusted in relation to the contour to be cleaned.

This can in particular offer advantages if the cleaning tool for transmitting the mechanical energy to the part provides an accelerated medium, accelerated solids or even an adhesive surface or a flexible cleaning section, with which the part is contacted directly mechanically.

In a further preferred embodiment of the invention, it is provided that a sensor for detecting the contour of the part is used relative to the cleaning tool and the measurement data of the sensor are integrated into a control circuit for tracking the contour. The sensor may be, for example, a proximity sensor or an optical sensor. By way of example only, when the cleaning tool applies the mechanical energy to the contour of the part by means of an air flow, an optical distance sensor for controlling a correct distance, for example a nozzle, from the contour can be used.

In a further preferred embodiment of the invention it is provided that the mechanical energy is introduced at least partially in the form of sound waves in the part. The sound waves can be transmitted, for example as structure-borne noise or as airborne sound on the part. The cleaning tool can for this purpose have a corresponding sound source. For example, the cleaning tool may contact a portion of a conveyor belt or workpiece carrier of the part. Depending on which portion of the contour of the part just passes a contact area of the cleaning tool with the conveyor belt or the workpiece carrier, then a sound signal adapted to the contour portion of the part is generated. The adaptation can be made for example with regard to the amplitude and frequency of the sound signal. The sound source may also include a membrane which is positioned relative to the contour and transmits sound waves over the air to the contour of the part in a targeted manner.

Advantageously, the cleaning can be done so without direct mechanical contact between the cleaning tool and the part itself, so the signs of wear can be avoided.

In a further preferred embodiment of the invention it is provided that the mechanical energy is introduced at least partially by means of an air flow in the part. The air flow can be caused both by an overpressure generated by the cleaning tool, as well as a negative pressure. In other words, the air flow can take over a fan function or a suction function.

This offers the advantage that the mechanical energy can act locally concentrated on an area of the contour. The cleaning performance can be increased accordingly. Furthermore, loose free-flowing material can be sucked off or blown away in the same work step.

In a further preferred embodiment of the invention it is provided that the mechanical energy is at least partially introduced by means of accelerated rigid body in the part. For example, the part can be irradiated with the cleaning tool with balls.

This offers the advantage that, for example, in boundary regions of a joining zone in which the generatively produced part meets the free-flowing material adhering as residues and present in the surrounding powder bed, solidified areas which can form a kind of burr are removed cleanly. In addition, the mechanical vibrations introduced by the balls into the part cause the other adhering flowable material to detach.

In a further preferred embodiment of the invention, it is provided that the mechanical energy is introduced into the part at least partially in the form of a contact force via an adhesive surface of the cleaning tool. The adhesive surface can be formed, for example, by an adhesive tape guided through the cleaning tool, which decreases the adhering flowable material from the contours of the part.

In this way, the removed free-flowing material is bound in place and can not get into the environment. The disposal of the removed free-flowing material is simplified.

In a further preferred embodiment of the invention, it is provided that the mechanical energy is introduced into the part at least partially in the form of sliding friction via a flexible cleaning section of the cleaning tool. The flexible cleaning section may be, for example, a brush or a brush.

This offers the advantage, for example, of sensitive contours that a gentle removal of the still adhering flowable material can take place. A brush or brush also gets into very fine surface structures of the part

In a further preferred embodiment of the invention, it is provided that the generatively manufactured part cleaned in the method is a generatively produced sand core. The free-flowing material in this case is sand.

Since sand cores are used in particular in foundry processes in series and are thus required in large numbers, the process according to the invention offers particular potential here. Of course, the inventive method can also be implemented with other parts made of free-flowing materials.

In the following, different variants in which mechanical energy can be applied to the contours of the part will be described in other words in addition to the above. It is further disclosed that the different variants in which mechanical energy can be applied to the contours of the part can also be used without the use of control data derived from the part's CAD data. The advantages according to the invention, according to which the mechanical energy can be introduced quickly, flexibly and safely along different contours into different parts, however, can not be achieved in this way. Nevertheless, the variants described below for the design of the cleaning tool and the manner of applying the mechanical energy can be used in the method according to the invention described above.

Thus, in a first variant, a conveyor belt can be sonicated with ultrasound. Due to small shear stresses that occur in solids due to ultrasound, the loose sand is separated from the sand core. Gravity ensures that the loose sand particles are accelerated downwards. Thus, the loose sand falls down into a collecting container. In an extension of the first variant, a sonotrode is used. The sonotrode creates a sound bridge from the ultrasonic generator to the workpiece and can optionally adjust the intensity of the ultrasonic vibration. The sonotrode is brought into contact with a carrier of the sand core. Consequently, the excess loose sand separates from the solid sand core. Through gaps in the conveyor belt, the falling sand can be collected and reused.

In a second variant, an air flow, for example via a curtain of air is used. The air curtain ensures that the sand core is ventilated. The circulation of the air ensures that the loose sand falls down and thus detaches itself from the sand core. An extension of the second variant is the attachment of a movable air nozzle that generates, for example, an air curtain. The air nozzle is attached to an outer ring. By this arrangement, each surface position on the component can be acted upon with compressed air. By manipulating the position of the sand core, undercuts and geometric overhangs can be freed from loose sand.

In a third variant, the sand core is bombarded with small balls. The speed and material composition of the balls is determined according to the properties of the sand core. The bombardment is carried out from different directions, so that the surface and any undercuts are completely freed from loose sand.

In a fourth variant, the sand is set in vibration by airborne sound. By this vibration causes the loose sand to fall off the sand core. Here, all grains of sand, which are not received in fixed connections, set in motion. In order to extract the sand from sewer pipes in the sand core or the like, the core must be turned. Here, the sand bed can be placed on a thin metal plate to reflect the sound waves on the sand core.

In a fifth variant, the contours of the sand core are traversed with a sucker. As an embodiment of the fifth variant, the sucker can be linked to a light barrier and thus depart the surface of the sand cores. The light barrier can also be used with the use of air locks through which the sand core is moved.

As the sixth variant, an adhesive tape is attached to the sand core, which removes the loose sand from the sand core. The composition of the adhesive may be determined depending on the properties of the sand core and the binder present with which the sand grains are bonded.

The seventh variant is the use of a brush that is linked to a sensor. This shuts off the surface of the sand core. The sensor helps to distinguish the surface of the sand core from the loose sand.

In all variants, the sand core is preferably changeable in its position by a rotation in order to be able to free existing undercuts or structures extending into the sand core from the loose sand.

In conclusion, in other words, the present invention relates to a method for the purification of a part which is produced in an additive manufacturing process and to which free-flowing material remains adhering from the production process. To remove the adhering material, mechanical energy is applied to the part to release the adhering residue. The entry of the mechanical energy into the part is done using a cleaning tool. To control the energy input into the part via the cleaning tool, CAD data of the part are evaluated and control variables extracted. The mechanical energy input can thus be flexibly adapted to a specific present contour of the part to be cleaned.

Further preferred embodiments of the invention will become apparent from the remaining, mentioned in the dependent claims characteristics.

The various embodiments of the invention mentioned in this application are, unless otherwise stated in the individual case, advantageously combinable with each other.

• 1 ein Ablaufschema des erfindungsgemäßen Verfahrens und
• 2 unterschiedliche Varianten zum Eintrag mechanischer Energie in das Teil zur Anwendung in dem erfindungsgemäßen Verfahren.

The invention will be explained below in embodiments with reference to the accompanying drawings. Show it:

• 1 a flow chart of the method according to the invention and
• 2 different variants for the entry of mechanical energy in the part for use in the method according to the invention.

1 1 shows a flowchart of the method according to the invention, a first method step being shown in the upper part of FIG. 1, a second method step in the middle part of FIG. 1 and a third method step in the lower part of FIG.

In the first process step becomes a part 10 from a free-flowing material 12 manufactured in a known generative manufacturing process. In the free-flowing material 12 These are grains of sand which are first pressed into shape and then provided with a binder in a region which is the shape of the part to be produced 10 equivalent. The binder is then cured with the application of thermal energy. After completion of these steps, not shown here is the part 10 in front. The part 10 here is a sand core 52 , If only an example for a part 10 shown, in the present embodiment of the method according to the invention, a plurality of sand cores 52 produced in a serial process.

The part 10 is in the second step with a conveyor belt 14 in a translatory degree of freedom 16 emotional. The part 10 is with a holding device 18 on the conveyor belt 14 stored and on the holding device 18 in another rotational degree of freedom 21 rotatable.

As can also be seen in the first method step, it can also be seen in the second method step that there is still free-flowing material 12 on an outer surface of the part 10 adheres. To remove these residues 20 of free-flowing material 12 is a cleaning tool 22 intended. The cleaning tool 22 is along a first axis 24 height adjustable and about a second axis 26 rotatable around.

Thus, the part 10 and the cleaning tool 22 Alignable relative to each other. Movements of the part 10bzw. conveyor belt 14 and the cleaning tool 22 are from a controller 28 controlled.

To remove the residues 20 leads the cleaning tool 22 the part 10mechanical energy 30 to. In the present example, the cleaning tool is 22 as a sucker 32 educated. The mechanical energy 30 becomes the part 10 therefore by means of an air flow 34 fed. The airflow 34 is due to a through the nipple 32 produced generated negative pressure, said hot air 36 the part 10 flows around and thus transfers frictional forces to the part 10. Thus, mechanical energy 30 on the part 10 transfer. The air flowing around the part 10 36 sucks the residues 20 of free-flowing material 12dabei of the part 10 from.

How out 1 can be seen, the part 10 in the present example has a triangular contour 38 , The control device 28 has CAD data 40 of the part 10 , The CAD data 40 include geometric data about the contour 38 of the part 10 , but also material technical data of the part 10 , From this CAD data 40 directs the controller 28 control data 42 from. This control data 42 be to the cleaning tool 22 and also to the conveyor belt 14 as well as the holding device 18 delivered. Based on the control data 42 The just mentioned components are moved in such a way that the mechanical energy 30 along the contour 38 of the part 10 with the cleaning tool 22 in the part 10 is introduced. For example, the nipple 32 in terms of its movement along the first axis 24 and around the second axis 26 controlled and also controlled in terms of its suction power. Thus, on the one hand always an optimal position and orientation of a nozzle 44 of the teat 32 relative to the contour 38 of the part 10 guaranteed. This is done in coordination with a rotary motion in the rotational degree of freedom 21 around a rotation axis 46 the holding device 18 , in combination with the movement of the conveyor belt 14 in the translatory degree of freedom 16 , On the other hand, from the material-technical data, which also comes from the CAD data 40 to create the control data 40 are derived, based on a specific adhesion of the flowable material 12an part 10, the suction power of the clean 32 and its optimum distance from the surface or the contour 38 Part 10 controlled.

In the present example, the cleaning tool has 22 additionally a sensor 48 , At the sensor 48 this example is an ultrasound-based proximity sensor. This is formed, the contour 38 Part 10 relative to the cleaning tool 22 capture. measurement data 50 of the sensor 48 are sent to the controller 28 sent and can, for example, to implement a control loop for safe tracking of the contour 38 be used.

In a third process step, that of the residues 20 of free-flowing material 12 completely liberated part 10 fed to a downstream production process. In the present example, the part 10 is purely exemplified by a generatively produced sand core 52 , This can now be used, for example, as an insert core in a casting process.

2 shows different variants for the use of mechanical energy 30 to the part 10 out 1 to clean. In the 2 variants shown in the process step two off 1 shown variant with the sucker 32 replace or supplement. In the 2 shown cleaning tools 22 can be analogous to the cleaning tool 22 out 1 be movable in different axes. The other components, such as the conveyor belt 14 and the holding device 18 correspond to those from the 1 and will be in 2 therefore not explained again in detail.

2A shows a variant in which the cleaning tool 22 is formed, sound waves 54 to create. The sound waves 54 be over the holding device 18 or via the conveyor belt 14 from the cleaning tool 22 as mechanical energy 30 on the part 10 transfer. Depending on the contour 38 of the part 10 can in the case of sound waves 54 with the control data 42 For example, an amplitude and a frequency are adjusted specifically. For this example, the natural frequency of the part 10 based on the CAD data 40 be determined.

2 B shows a further variant in which the cleaning tool 22 is also formed, sound waves 54 to create. In the in 2 B However, the sound waves are not directly in the form of structure-borne noise, but over air on the part 10 transfer. The control data 42 Here too, for example, an amplitude and a frequency can be adapted specifically. This also applies to a distance of the cleaning tool 22 from the contour 38

In 2C a variant is shown in which the cleaning tool 22 is formed, the mechanical energy 30 by means of accelerated rigid body 56 in the part 10 contribute. The rigid bodies 56 For example, can be small balls for shot peening.

In the in 2D variant shown would be the mechanical energy 30 proportionately in the form of a contact force F _P on the part 10 transfer. To transfer the pressing force F _P leads the cleaning tool 22 an adhesive surface 58 , in the present example in the form of an adhesive tape 60 , about the part 10 ,

Finally, in 2E a variant shown in which the mechanical energy 30 proportionately in the form of sliding friction R via a flexible cleaning section 62 of the cleaning tool 22 in the part 10 is introduced. The flexible cleaning section 62 For example, a brush 64 be.

LIST OF REFERENCE NUMBERS

10

part

12

free-flowing material

14

conveyor belt

16

translatory degree of freedom

18

holder

20

arrears

21

rotational degree of freedom

22

cleaning tool

24

first axis

26

second axis

28

control device

30

mechanical energy

32

sucker

34

airflow

36

sucked air

38

triangular contour

40

CAD data

42

control data

44

jet

46

axis of rotation

48

sensor

50

measurement data

52

sand core

54

sound waves

56

rigid body

58

adhesive surface

60

duct tape

62

cleaning section

64

brush

R

escort friction

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 2005/0161146 A1 [0005]
• US 2016/0228975 A1 [0006]
• DE 102013215748 A1 [0007]
• DE 3424000 A1 [0008]
• WO 2014/009376 A1 [0009]
• WO 2007/139938 A2 [0010]
• CN 205816336 U [0011]

Claims (10)

A method of cleaning a generatively manufactured part (10), comprising the steps of: - generatively producing the part (10) from a flowable material (12); - removal of residues (20) of the flowable material (12) using a cleaning tool (22) for supplying mechanical energy (30) in the part (10); characterized in that control data (42) are derived from CAD data (40) of the part (10) and the mechanical energy (30) using the control data (42) along a contour (38) of the part (10) with the cleaning tool (22) is introduced into the part (10). Method according to Claim 1 , characterized in that the part (10) and the cleaning tool (12) are aligned at least once relative to each other while the mechanical energy is introduced into the part (10). Method according to one of the preceding claims, characterized in that the part (10) at least temporarily in at least one translational (16) and / or rotational degree of freedom (21) is moved, while the mechanical energy is introduced into the part (10). Method according to one of the preceding claims, characterized in that a sensor (48) for detecting the contour (38) of the part (10) relative to the cleaning tool (22) is used and the measurement data (50) of the sensor (48) in a control loop to track the contour (38) are involved. Method according to one of the preceding claims, characterized in that the mechanical energy (30) is at least partially introduced in the form of sound waves (54) in the part (10). Method according to one of the preceding claims, characterized in that the mechanical energy (30) is at least partially introduced by means of an air flow (34) in the part (10). Method according to one of the preceding claims, characterized in that the mechanical energy (30) is at least partially introduced by means of accelerated rigid body (56) in the part (10). Method according to one of the preceding claims, characterized in that the mechanical energy (30) at least partially in the form of a contact force (F _P ) via an adhesive surface (58) of the cleaning tool (22) in the part (10) is introduced. Method according to one of the preceding claims, characterized in that the mechanical energy (30) is at least partially introduced in the form of sliding friction via a flexible cleaning section (62) of the cleaning tool (22) in the part (10). Method according to one of the preceding claims, characterized in that in the method purified generatively manufactured part (10) is a generatively produced sand core (52).

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