DE102018108484A1 - Method for coating a construction space in a 3D printing process by means of a coater unit and such a coater unit - Google Patents

Abstract

The invention relates to a method for coating a construction space in a 3D printing process by means of a coater unit (10) and such a coater unit (10).
It is envisaged that a method for coating a construction space in a 3D printing process is provided. The method comprises the following steps: providing a starting material (22) in at least one storage container (14) from a coater unit (10), setting a first opening (24) in the storage container (14) by means of a first adjustable closing element (26) , Moving the coater unit (10) in a first direction of movement over the space of the component to be manufactured (36) and discharging the starting material (22) from the reservoir (14). At the same time, at least one first transport device (12) is provided, which is provided below the storage container (14), wherein the first transport device (12) is adapted to receive the discharged starting material (22) at the first opening (24) and to a first region , which is spaced from the first opening (24) to transport, so that at the end of the first transport device (12) the starting material (22) is coated contactlessly in the installation space.

Description

The invention relates to a method for coating a construction space in a 3D printing process by means of a coater unit and such a coater unit.

In 3D printing processes, for example, the 3D printing of sand cores, among other things the goal is to produce even layers. This is particularly important when a high number of layers, such as up to 1,000 layers, to be superimposed. In this context, the surface roughness plays an essential role for the subsequent printing result. Many 3D printing processes use a squeegee directly on the powder bed or sand bed to smooth out the layers. This can lead to the component, which was generated directly below the last layer, being able to be pulled along. In addition, the traversing speed can be limited by the resulting transverse forces during the coating process. Another problem associated with the coating step is the following. In a 3D printing process, provision may be made, for example, for sand to be applied in a construction space in a first step and then then consolidated in a second step by means of a printing unit, which subsequently travels over this construction space. This printing step can be accomplished by means of a liquid adhesive. The downside to such a process is that two steps are needed. It therefore can not be coated continuously. Accordingly, a coater traverses the plane to be manufactured in a first step to generate a layer and then travels back without a coating step. Only then can the printing unit be activated to perform the printing step. The two aspects mentioned above each influence the efficiency of such processes individually and are therefore reflected in the cost structure.

From the prior art a variety of approaches are already known to take.

Thus, the document discloses DE 10 2014 112 447 A1 such as a 3D printer, a 3D printer assembly, and a generative manufacturing process. In this case, components are printed in two adjacent areas, parallel by means of two suitable devices. A coater arrangement is also designed to supply the two areas, with a separate coater being provided for each area. The coaters are each in direct contact with the respective installation space. A contactless coating is therefore not provided. The coaters can be used bidirectionally.

WO 2016/030 391 A1 discloses a coater arrangement for a 3D printer as known. Again, a coating is made directly on the construction level. A closing device is provided at the opening, whereby the dispensing of the particulate building material is made selectively closable. In addition, a coating element is provided to level the amount to be stacked directly on the building level. Also, a printhead may be provided simultaneously to solidify the applied layer. A contactless job on the building level is not provided.

WO 2017/152 897 A1 discloses a method and a device for producing 3D molded parts as known. Several construction tools are arranged movable. In addition, at least one layer unit is arranged to be movable. A contactless job on the construction level is not provided here.

The invention is based on the object of providing a method for coating a construction space in a 3D printing process by means of a coater unit and such a coater unit, which support improved efficiency and thus cost-effective production.

In a preferred embodiment of the invention, it is provided that a method for coating a construction space in a 3D printing process is provided. The method comprises the following steps: providing a starting material in at least one storage container of a coater unit, setting a first opening in the storage container by means of a first adjustable closing element, moving the coater unit in a first direction of movement over the installation space of the component to be manufactured and discharging the starting material from the reservoir, wherein at least one first transport device provided below the reservoir is simultaneously started, the first transport device being configured to receive the discharged starting material at the first port and to a first region which is spaced from the first port, to transport, so that at the end of the first transport device, the starting material is coated without contact in the space.

Thus, it is possible to apply the starting material uniformly to the installation space, without requiring a contact of the installation space, for example, by the closing element is necessary. It is thus a non-contact, uniform Coating and thus an increase in the coating speed possible. This is applicable for all powder / sand-based 3D printing processes. For example, sand is stored in the reservoir or in the container and applied evenly by the transport device to the space. Here, the layer height and roughness is already ensured by the adjustable closing element. With this concept, smoothing can be achieved indirectly via the integrated closing element at the reservoir outlet, ie at the opening. An exact amount of starting material can thus be removed via the transport device. The adjustable closing element thus acts indirectly on the surface quality, so that a contactless coating or scattering of the starting material is made possible on the space. The adjustability may relate to a height adjustment. The closing element can be guided, for example, in two guide rails and can be screwed, clamped or fixed in a desired height, for example. This can be provided for example via slots on the reservoir. The closing element thus transfers no forces, unlike other 3D printing methods, to a construction bed and a component located therein. The closing element, unlike other previously known concepts, does not act directly on the component. The component can not be removed or moved. It is thus possible a particularly efficient method due to the higher process speed or travel speed. The fact that without a direct closing element, as in conventional systems, driven, the component to be generated can not be destroyed by a direct contact or by a direct contact. Thus, process reliability and speed can be increased.

It is also essential that the transport of the layer of the starting material via the movement of the conveyor belt and the omission of the layer over the space, in parallel crossing and opposite direction of movement of the coater unit to the conveyor belt. The directions of movement are reversed, the speed is the same. This is of essential importance since the relative speed of the starting material on the conveyor belt thereby corresponds to zero and thus drops from the conveyor belt to the installation space with v = 0.

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

In a further preferred embodiment of the invention it is provided that the coater unit is designed to comprise at least one printing unit, wherein additionally a printing step is provided. Thus, different process steps can be performed by means of only one unit, so that an efficient method is made possible.

Furthermore, in a further preferred embodiment of the invention, it is provided that a second opening, which is arranged in the at least one storage container relative to the first opening, is adjusted by means of a second adjustable closing element, the coater unit in a second direction of movement over a construction space of the component to be manufactured Starting material is discharged from the reservoir from the second opening, at the same time at least one second transport device, which is provided below the reservoir on the opposite side of the first transport device, is started, wherein the second transport device is adapted to the discharged starting material at the receive second opening and to a second region, which is spaced from the second opening to transport, so that at the end of the second transport device, the starting material without contact in the space is coated. In this way, a continuous printing and coating can take place from both sides left and right. Thus, a time saving and thus a particularly efficient method can be achieved. It can therefore be coated from both sides. The printing unit is located, for example in the middle and left and right of each one a transport device. When the printing unit moves to the left and prints, the right side of the coater unit runs and applies a layer, the left side of the coater unit in the form of the transport device stops until the printing unit completes a direction change and prints to the right. Thus, it is continuously coated and printed. The coater unit is thus basically two-part and could also be considered as a unit of two coater units. Instead of a coating process, continuous coating and printing is thus possible. This allows non-contact, uniform, continuous coating without waiting time. For example, 3D printing in the field of powder printing is thus much faster and safer. The fact that is driven without a direct closing element as in conventional systems, the component to be generated can not be destroyed by a direct contact or by a direct contact. Thus, process reliability and speed can be increased.

It is also provided in a further preferred embodiment of the invention that only one function of the respective direction of movement Transport device is activated and that at the same time for the respective coating by means of the activated transport device, the at least one printing device is activated or activated so that at the same time a printing step and spaced from a coating step can be performed, which is performed in the direction of movement behind the printing step. In this way, a particularly efficient method is possible.

It is also provided in a further preferred embodiment of the invention that a speed of the respective transport device is set as a function of a speed of a respective direction of movement of the coater unit. Thus, uniform coating can be realized particularly well and thus a particularly efficient process can be provided.

In a further preferred embodiment of the invention, it is provided that a respective opening, which is located on one side of an inactive transport device, is closed with a sealing element. Thus, unwanted discharge of the raw material is effectively prevented.

It is also provided in a further preferred embodiment of the invention that the respective closing elements are provided in the form of doctor blades and that the respective transport devices are conveyor belt systems. Layer height and roughness can thus be ensured reliably by the doctor blades, so that a particularly efficient method is provided. The doctor blades may for example have the shape of a straight sheet.

It is also provided in a further preferred embodiment of the invention that the starting material is selected from: plastic powder, metal powder or sand, depending on the starting material optionally a suitable pressure medium is selected and wherein excess starting material is collected in the space by means of a collecting device, wherein the collecting device at least one perforated screen, at least one scraping element and at least one collecting container, wherein due to a relative to the at least one perforated screen movement of the at least one Abstreichelements excess starting material is collected by the at least one perforated screen in the at least one collecting container. The method can therefore be used flexibly in a wide variety of 3D printing concepts. By means of the collecting device, excess starting material can be collected and subsequently reused. This can also increase the efficiency of the process. Due to the contactless coating uniform use of such a collecting device is particularly well possible.

It is further provided in a further preferred embodiment of the invention that a coater unit for coating a construction space in a 3D printing process according to the method of claims 1 to 8 is provided. The coater unit comprises at least one storage container for holding a starting material having at least one opening and at least one adjustable closing element, wherein the opening and the closing element are designed to discharge the starting material from the storage container, and at least one transport device which is arranged below the at least one storage container and is configured to receive discharged starting material from the at least one first opening and to transport to a first area spaced from the first opening first area, so that in the first area a coating step by means of the first transport device is executable. The aforementioned advantages can also be realized with this coater unit.

Furthermore, in another preferred embodiment of the invention, the coater unit further comprises at least one second transport device, which is arranged below the at least one storage container and is adapted to receive discharged starting material from at least one second opening and to one from the second opening so that a coating step in the second area can be carried out by means of the second transport device, wherein at least one of the first and second movement directions of the coater unit, which is opposite to the first movement direction of the coater unit Transport devices or one of the at least second transport devices can be activated.

The aforementioned advantages can also be realized with this coater unit.

It is also provided in a further preferred embodiment of the invention that the coater unit additionally comprises a printing unit which is designed to perform a printing step during a respective coating step by means of the respective transport device. The aforementioned advantages can also be realized with this coater unit.

Finally, it is provided in a further preferred embodiment of the invention, in that the coater unit additionally comprises a microwave unit. This microwave unit can thus be integrated in such a way that an optional drying step can be performed during the process, so that the method becomes even more efficient.

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

• 1 eine perspektivische Ansicht einer Beschichtereinheit mit einer Transportvorrichtung;
• 2 eine Seitenansicht eines Details einer Beschichtereinheit;
• 3 eine perspektivische Ansicht einer weiteren Beschichtereinheit mit zwei Transportvorrichtungen;
• 4 eine schematische Seitenansicht einer weiteren Beschichtereinheit mit zwei Transportvorrichtungen;
• 5 eine weitere schematische Seitenansicht der Beschichtereinheit mit zwei Transportvorrichtungen aus 4 in einer gegenläufigen Bewegungsrichtung; und
• 6 eine Draufsicht auf eine Auffangvorrichtung.

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

• 1 a perspective view of a coater unit with a transport device;
• 2 a side view of a detail of a coater unit;
• 3 a perspective view of another coater unit with two transport devices;
• 4 a schematic side view of another coater unit with two transport devices;
• 5 a further schematic side view of the coater unit with two transport devices 4 in an opposite direction of movement; and
• 6 a plan view of a collecting device.

1 shows a perspective view of a coater unit 10 with a transport device 12 , The transport device 12 is below a storage container 14 arranged. In the case of the reservoir 14 filled with sand, so can the reservoir 14 Also referred to as a sand container. The storage tank 14 has in the example shown a substantially cuboid shape and is above the transport device 12 arranged, wherein a longitudinal width 16 of the storage container 14 equal to a width 18 the transport device 12 is. The storage tank 14 is vertically aligned so that a height 20 longer than its longitudinal width 16 is. The perspective view relative to the reservoir 14 is shown cut, so partially in the figure, the interior of the reservoir 14 can be seen. In the reservoir 14 is the starting material 22 which could be sand, for example. According to the principle of gravity, the starting material falls 22 in the reservoir 14 vertically downwards relative to the image plane, so that it opens at an opening 24 of the storage container 14 can be left out. This opening 24 is located on the image plane bottom left of the reservoir 14 and is thus above the transport device 12 arranged. In this way, the starting material 22 So the reservoir 14 leave and on the transport device 12 be left out. At the opening 24 is an adjustable closing element 26 to recognize. This closing element 26 For example, it can be a squeegee. The closing element 26 is over the entire longitudinal width 16 of the storage container 14 arranged and thus also has the same width 18 like the transport device 12 on. A height of the closing element 26 or the doctor blades can be adjusted so that thus an output of the opening 24 can be influenced. It is therefore possible via the height-adjustable closing element 26 to determine what amount of starting material 22 from the reservoir 14 on the transport device 12 is omitted. In addition, the closing element 26 affect how the starting material 22 or in which form the starting material 22 the reservoir 14 leaves. The closing element 26 Thus, during the Auslassvorgangs the starting material 22 in a predetermined manner, so that the starting material 22 with a predefined layer thickness the reservoir 14 leaves. The squeegee is therefore not directly arranged on a construction bed, as in other 3D printing processes, but indirectly. Thus, no forces are transmitted to an object to be manufactured at this point. On the opposite side of the opening 24 is also a sealing element 28 to recognize, which related to the image plane bottom right of the reservoir 14 located and over the entire longitudinal width 16 of the storage container 14 is arranged. The sealing element 28 may for example be formed as a felt or a rubber lip. The transport device 12 is a conveyor belt in this figure. Out of the opening 24 leaves source material 22 the reservoir and is placed on the conveyor belt. The conveyor belt has a circumferential bearing surface 30 on, which on two in each case on the left and right edge of the conveyor belt internal rollers 32 can be driven. The starting material 22 So it's placed in a predefined way on this support surface, so it's from the opening 24 can be moved away. The drive is not shown and is not significantly limited at this point. For example, this could be an electric drive. Relative to the image plane, the support surface moves 30 from right to left. The feed rate may be, for example, 1 m / s. A small block arrow indicates this movement of the conveyor belt. The coater arrangement 10 moves to the right, what with a large block arrow to the right of the reservoir 14 is hinted at. The feed rate of the coater arrangement 10 may for example be 1 m / s. At the left end of the conveyor belt falls starting material 22 down, leaving an underlying level 34 with a component located there 36 , which is to be manufactured, can be uniformly coated. The coating proceeds without contact.

2 shows a side view of a detail of a coater unit 10 , More precisely, a closing element 26 at the opening 24 of the storage container 14 shown in a side view. This closing element 26 may be a squeegee, with it being vertically aligned. A double-sided arrow indicates the height adjustment. Below the squeegee or the closing element 26 is the opening 24 from the closing element 26 to recognize. The height adjustment of the closing element 26 So defines the output size of the opening 24 , from which starting material 22 leave the reservoir to a transport device 12 which may be a conveyor belt, for example, to arrive. An arrow below the transporter 12 indicates a direction of movement of the transport device 12 so that the even layer of the starting material 22 which are on the transport device 12 located, from the opening 24 is transported away. In the reservoir 14 can according to the gravity principle starting material 22 replenish until the reservoir 14 is empty and can be reloaded over a Auffüllöffnung not shown in detail.

3 shows a perspective view of another coater unit 10 with two transporters 12 . 12 ' , which is above a building level 34 located. The coater unit 10 has a reservoir 14 on which with a starting material 22 is filled. The storage tank 14 is shown cut, so the starting material 22 inside is recognizable. The storage tank 14 has at its upper end two filling marks 37 for example, which indicate a filling maximum at the top and a filling minimum at the bottom. The locations of these two filling marks shown here 37 on the storage tank 14 are to be understood as exemplary only and could be located differently in another variant. The two transporters 12 . 12 ' are each, based on the image plane, left and right below the reservoir 14 arranged and are each as a conveyor belt with corresponding bearing surfaces 30 and rolling 32 shown. The principle is essentially identical to the one in 1 illustrated and previously described principle. In 3 are indeed respective openings 24 and closing elements 26 not shown, but are mutatis mutandis to the said principle according to an omission of the starting material 22 from the reservoir 14 to enable. The left transport device 12 moves applied starting material 22 to the left, so this starting material 22 on the left edge of the transport device 12 evenly and non-contact on the underlying building level 34 can be applied or coated. The right transport device 12 ' moves applied starting material 22 to the right, so this starting material 22 at the right edge of the transport device 12 ' evenly and non-contact on the underlying building level 34 can be applied or coated. Between the two transport devices 12 . 12 ' is in a bulge 38 of the storage container 14 a printing unit 40 to recognize. This printing unit 40 is shown schematically essentially as a rectangular body and can be vertically down the underlying building level 34 imprint, which is indicated schematically in the figure. The printing unit 40 is with a squeegee 42 pictured, which on both sides of the printing unit 40 vertically down towards the construction level 34 shows. This extra squeegee 42 is only optional and can be omitted in a variant, not shown. Directly above the printing unit 40 points the reservoir 14 in its interior a pointed upwards delimiting element 44 on. About the boundary element 44 can the starting material 22 inside the storage tank 14 in each case to openings, not shown, of the reservoir 14 reach. In other words, the bulge 38 in the reservoir 14 designed such that the limiting element 44 which has a substantially triangular shape, the printing unit 40 can record.

4 shows a schematic side view of another coater unit 10 with two transporters 12 . 12 ' , The principle is essentially identical to the principles already shown and described above. In this figure, the coater unit moves 10 from left to right, this direction of movement being indicated by a large block arrow to the right of a storage bin 14 is indicated. The feed rate may be, for example, 1 m / s. The transport device 12 ' , which are right in the direction of movement of the coater unit 10 is inactive and thus has a feed rate of 0. One on this transport device 12 ' arranged opening 24 ' leaves no source material 22 on this transport device 12 out. On the opposite side is the local transport device 12 activated and it passes through a local opening there 24 starting material 22 on this transport device 12 , The feed rate of this transport device 12 may for example be 1 m / s. Although a closing element is in each case not shown in detail, but is provided in accordance with the principle in each case with. At the end of the activated transport device 12 leaves the starting material 22 the transport device 12 so that a coating of starting material 22 from one below the coater unit 10 located building level 34 with a component to be manufactured there 36 can be performed without contact. Midway between the two transport devices 12 . 12 ' is a printing unit 40 to recognize. If the coater unit 10 from left to right across the construction level 34 is moved, it is thus possible, a printing step by means of the printing unit 40 to realize and during the same sequence of movements to perform a subsequent to the printing step coating step. The coater unit 10 and the printing unit 40 form an integrated unit. Such a unit can also be named as a printer / coater unit. A delimiter 44 has in this variant on a substantially flattened top.

5 shows a further schematic side view of the coater unit 10 with two transporters 12 . 12 ' out 4 in an opposite direction of movement. The principle remains the same. In this figure, the coater unit moves 10 from right to left, this direction of movement being indicated by a large block arrow to the left of a storage bin 14 is indicated. The feed rate may be, for example, 1 m / s. The transport device 12 , which are left in the direction of movement of the coater unit 10 is inactive and thus has a feed rate of 0. One on this transport device 12 arranged opening 24 leaves no source material 22 on this transport device 12 out. On the opposite side is the local transport device 12 ' activated and it passes through a local opening there 24 ' starting material 22 on this transport device 12 , The feed rate of this transport device 12 ' may for example be 1 m / s. Although a closing element 26 'is in each case not shown in greater detail, it is provided with the principle according to the principle in each case. At the end of the activated transport device 12 leaves the starting material 22 the transport device 12 ' so that a coating of starting material 22 from one below the coater unit 10 located building level 34 with a component to be manufactured there 36 can be performed without contact. Midway between the two transport devices 12 . 12 ' is a printing unit 40 to recognize. If the coater unit 10 from right to left across the construction level 34 is moved, it is thus possible, a printing step by means of the printing unit 40 to realize and during the same sequence of movements to perform a subsequent to the printing step coating step. The coater unit 10 and the printing unit 40 form an integrated unit. Such a unit can also be named as a printer / coater unit. A delimiter 44 has in this variant on a substantially flattened top.

6 shows a plan view of a collecting device 46 , A coater unit 10 is doing from, based on the image plane, right to left on this collection device 46 emotional. This coater unit 10 can also a not shown in detail printing unit 40 and be referred to as a printer / coater unit. The collecting device 46 is in a building level 34 arranged and is made up of individual collection containers 48 educated. A collection container 48 can also be called a box. The individual collection containers 48 For example, they may be arranged loosely next to one another or be coupled to one another by means of a coupling mechanism not further shown. In a variant not shown could also only a very large container 48 be provided. An amalgamation of individual collection containers 48 can be called XXL box. The to the collecting device 46 associated perforated screen 50 and scraping element 52 are not shown in this figure and are discussed in detail in 7 shown.

7 shows a detail of a catcher 46 , Exactly shows 7 a perforated screen 50 and a doctoring element 52 in the form of a sheet, which over the collecting containers 48 can be arranged. The scraping element 52 or this sheet partially covers the perforated screen 50 , On this scraping element 52 can be a component to be manufactured 36 and excess starting material 22 are arranged, which is not shown in detail in the figure. When the scraping element 52 is moved, remains to be manufactured component 36 on the perforated screen 50 and the excess starting material 22 can through the holes of the perforated screen 50 into the collecting containers underneath 48 arrive or expire. The component 36 remains in the installation space 34 and can be taken afterwards.

LIST OF REFERENCE NUMBERS

10

coater

12

first transport device

12 '

second transport device

14

reservoir

16

longitudinal width

18

width

20

height

22

starting material

24

first opening

24 '

second opening

26

first closing element

26 '

second closing element

28

sealing element

30

bearing surface

32

roller

34

building plane

36

component

37

filling mark

38

bulge

40

printing unit

42

doctor

44

limiting element

46

catcher

48

receptacle

50

strainer

52

scraping

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

• DE 102014112447 A1 [0004]

Claims (12)

A method for coating a construction space in a 3D printing process, comprising the steps of: providing a starting material (22) in at least one storage container (14) from a coater unit (10), setting a first opening (24) in the storage container (14) a first adjustable closure element (26), moving the coater unit (10) in a first direction of movement over the space of the component to be manufactured (36) and discharging the starting material (22) from the reservoir (14), characterized in that at least one first Transport device (12), which is provided below the storage container (14) is started, wherein the first transport device (12) is adapted to receive the discharged starting material (22) at the first opening (24) and to a first region, which of the first opening (24) is spaced to transport, so that at the end of the first transport device (12) d the starting material (22) is coated without contact in the installation space. Method according to Claim 1 wherein the coater unit (10) is adapted to comprise at least one printing unit (40), wherein additionally a printing step is provided. Method according to one of the preceding claims, wherein a second opening (24 ') which is arranged in the at least one storage container (14) with respect to the first opening (24) is adjusted by means of a second adjustable closing element (26'), the coater unit ( 10) in a second direction of movement over a space of the component to be manufactured (36) is moved, starting material (22) from the reservoir (14) from the second opening (24 ') is omitted, wherein at least one second transport device (12') which is provided below the storage container (14) on the opposite side of the first transport device (12) is started, wherein the second transport device (12 ') is adapted to receive the discharged starting material (22) at the second opening (24') and to transport to a second area, which is spaced from the second opening (24 '), so that at the end of the second transport device ung (12 ') the starting material (22) is coated without contact in the space. Method according to one of the preceding claims, wherein depending on the respective direction of movement, only one transport device (12, 12 ') is activated and at the same time for the respective coating by means of the activated transport device (12, 12'), the at least one printing unit (40) is activated or is activatable, so that at the same time a printing step and spaced from a coating step can be performed, which is carried out in the direction of movement after the printing step. Method according to one of the preceding claims, wherein a speed of the respective transport device (12, 12 ') in dependence of a speed of a respective direction of movement of the coater unit (10) is adjusted. Method according to one of the preceding claims, wherein a respective opening (24, 24 '), which is located on one side of an inactive transport device (12, 12'), with a sealing element (28) is closed. Method according to one of the preceding claims, wherein the respective closing elements (26) in the form of doctor blades (42) are provided and that the respective transport devices (12, 12 ') are conveyor belt systems. Method according to one of the preceding claims, wherein the starting material (22) is selected from: plastic powder, metal powder or sand, wherein depending on the starting material (22) optionally a suitable pressure medium is selected and wherein excess starting material (22) in the space by means of a collecting device (46 ), wherein the collecting device (46) at least one perforated screen (50), at least one Abstreichelement (52) and at least one collecting container (48), wherein due to a relative to the at least one perforated screen (50) completed movement of the at least one Abstreichelements (52) excess starting material (22) through the at least one perforated screen (50) in the at least one collecting container (48) is collected. Coating unit (10) for coating a construction space in a 3D printing process according to the method according to Claims 1 to 8th comprising at least one storage container (14) for holding a starting material (22) with at least one opening (24, 24 ') and at least one adjustable closing element (26, 26'), the opening (24, 24 ') and the closing element (22) 26, 26 ') are designed to discharge the starting material (22) from the storage container (14), at least one transport device (12, 12') which is arranged below the at least one storage container (14) and is designed to discharge discharged starting material (22 ) from the at least one first opening (24) and to transport to a first opening (24) spaced from the first area, so that in the first area Coating step by means of the first transport device (12) is executable. Coater unit (10) according to Claim 9 comprising at least one second transport device (12 ') disposed below said at least one reservoir (14) and adapted to receive discharged source material (22) from at least one second port (24') and to one from said second port (24 ), so that in the second region a coating step by means of the second transport device (12 ') is executable, wherein in dependence on a first direction of movement of the coater unit (10) or a second direction of movement of the coater unit (10), which in opposite to the first movement direction of the coater unit (10) is that at least one of the first transport devices (12) or one of the at least second transport devices (12 ') can be activated. Coater unit (10) according to Claim 9 or 10 in that the coater unit (10) additionally comprises a printing unit (40) which is designed to execute a printing step during a respective coating step by means of the respective transport device (12, 12 '). Coater unit (10) according to Claims 9 to 11 wherein the coater unit (10) additionally comprises a microwave unit.

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