DE102017003662A1 - Coating device with slide and method for the production of three-dimensional components - Google Patents

Abstract

The invention relates to a coater device suitable for a 3D printing machine, which is characterized in that the device comprises a coating roller and a slider and a method which uses this coater.

Description

The invention is a coater system for the layered production of three-dimensional articles with coating roller and a slide for the presentation of the particulate material and a method for producing three-dimensional components.

In the European patent specification EP 0 431 924 B1 A method of manufacturing three-dimensional objects from computer data will be described. In this case, a particulate material is applied in a thin layer on a platform and this selectively printed by means of a print head with a binder material. The particle area printed with the binder sticks and solidifies under the influence of the binder and optionally an additional hardener. Subsequently, the platform is lowered by one layer thickness into a structural cylinder and provided with a new layer of particulate material, which is also printed as described above. These steps are repeated until a certain desired height of the object is reached. The printed and solidified areas create a three-dimensional object.

This object made of solidified particulate material is embedded after its completion in loose particulate material and is subsequently freed from it. This is done for example by means of a nipple. Thereafter, the desired objects remain, which are then affected by powder deposits, e.g. be freed by manual brushing or sandblasting.

The components are usually present after printing in a building container. This construction container usually represents a cuboid volume. This volume is loaded with a variety of geometries in order to use the machine well.

3D printing based on powdered materials and the incorporation of liquid binders is the fastest method among the layering techniques.

This process can process various particulate materials including, but not limited to, natural biological raw materials, polymeric plastics, metals, ceramics and sands.

As a binding system, e.g. serve a solid in the particulate material. This is dissolved by a solvent ejected from the ink jet printhead. After volatilization of the solvent, the particles stick together at the desired locations. The component can be removed from the remaining loose powder after a certain waiting time from the building container. This waiting time is generally long because the solvent is only slowly released from the dissolved material. The components are often weak after unpacking and can be plastically deformed. The volatilization of the solvent creates a certain adhesion to the component, which must be removed after unpacking by hand. The solvent may additionally attack the printhead. In addition, the dissolution process with subsequent reconsolidation causes shrinkage in the component and thus geometry deviations.

A solvent can also be loaded with molecules or particles and used. This can reduce the shrinkage. Similarly, the aggressiveness of the solvent can be reduced with the same component strength. However, the solvent must be completely removed before unpacking, and the problem with adhesions is also given here.

Another possibility is the use of a system which chemically leads to a solidification of the imprinted liquid and thereby realizes the binding of the particles. The components of the system are kept separate in the system if possible. Only during the printing process does the desired solidification reaction occur. An example of such a system may be a method known as the cold resin process. In this case, an acid-coated sand is brought into contact with furfuryl alcohol. This leads to a chemical reaction that causes the formerly liquid components to become a cross-linked plastic.

Prior art printers sometimes include building trays that are removable from the equipment. These serve as a limitation for the powder and thus stabilize the building process. By changing the construction container, process steps can be parallelized and the plant can thus be utilized well. Likewise, there are systems that print on a platform that can be removed from the system like the construction containers. Also, methods are known in which is printed on a continuous conveyor belt at a certain angle.

Various mechanisms are known for the coating process.

The font US 5,387,380 discloses a device in which the particulate material is smoothed by a roller over the construction field. For this purpose, a defined amount of powder is raised in the direction of movement in front of the coater via a mechanism which corresponds to the technology of the actual construction platform, so that the coater grasps the particle material as it travels and pushes it in front of him. By a rotation of the roller is the particulate material is conveyed out of the gap between the roller and the construction field so that uncontrolled compressions are prevented. The powder delivery mechanism is a complex construction and must be arranged in front of the actual construction field of the printer. This severely limits the freedom of design of the printer and makes the design unnecessarily large.

Likewise, devices are known in which the coater carries the powder with him. In this case, an amount is stored, which is much larger than the volume of a layer. During the coating process, the powder is released for coating. The dosage is often switched by vibration. Typical of arrangements is the use of a standing blade which smoothes the layer on the construction field. The font DE 10117875 C1 discloses such an arrangement.

The claimed invention is neither disclosed nor suggested in the above cited prior art documents.

A disadvantage of such a construction is a strong dependence of the reliability of the powder flow properties. There are no restrictions on free-flowing powders. Strongly cohesive powders, however, are less effective to dose and react with very restricted flow to vibrations. A disadvantage may also be a too low or too large amount of overfeed, as this can reduce the quality of the coating process, which can have a negative effect on the quality of the end products.

An object of the present invention was therefore to provide a coater unit and / or metering unit suitable for 3D printing, which makes it possible to be able to meter the particulate material with little deviation.

An object of the present invention was to be able to set the overfeed in relation to the layer to be applied in a defined manner.

An object of the present invention was to be able to apply the metered amount of particles over the entire printing process substantially constant or with tolerable deviations.

An object of the present invention was to reduce or substantially avoid the disadvantages of the prior art.

Brief summary of the disclosure

In one aspect, the disclosure relates to a coater having a roller and a slider mechanism.

In one aspect, the disclosure relates to an apparatus for use in a device for the layered production of three-dimensional articles (components). This device is used to produce smooth layers. The device comprises a coating roller and a slide mechanism carried along, which is designed such that at the beginning of a coating run a defined amount of particulate material can be given in front of the roller.

In one aspect, the disclosure relates to a method of 3D printing using a coater with slider and meterable dispensing of particulate matter.

list of figures

• 1 : Representation of a conventional 3D printing process according to the prior art. Presentation cut in oblique view.
• 2 : Schematic representation of the process steps of 3D printing.
• 3 : Schematic representation of a coating process according to the invention
• 4 : Schematic representation of the process when using the inventive device
• 5 : Sectional view of an exemplary embodiment of the invention

Detailed description

In the following some terms are defined in more detail. Otherwise, for the terms used, the meanings known to those skilled in the art are to be understood.

For the purposes of the invention, "layer-building method" or "3D-printing method" are all known from the prior art methods that allow the construction of components in three-dimensional shapes and are compatible with the described process components and devices.

"Shaped body" or "component" in the sense of the invention are all three-dimensional objects produced by the method according to the invention and / or the device according to the invention, which have a dimensional stability.

"Construction field" is the plane or, more broadly, the locus on which or in which the particulate material bed grows during the construction process by repeated coating with particulate matter. Often, the construction site is limited by a floor, the "building platform", by walls and an open deck area, the building level.

The process "printing" refers to the summary of the processes coating, printing and working height adjust and takes place according to the invention in an open or closed process space.

In a device according to the invention, "travel axis" is an axis which carries device elements, is arranged above the construction field tools and has a travel distance which is wide in relation to the other axes in the system.

"Spreading" in accordance with the present invention means spreading and smoothing of the particulate material. In this case, a defined amount of powder is presented at the start position of a coating travel and distributed or streaked by a rotating roller in the layer volume.

As "particulate material" or "powder" may be used all known for 3D printing, flowable materials, in particular in powder form, as slag or as a liquid. These may be, for example, sands, ceramic powders, glass powders, and other powders of inorganic materials, metal powders, plastics, wood particles, fiber materials, celluloses and / or lactose powders, as well as other types of organic, powdered materials. The particulate material is preferably a dry, free-flowing powder, but a cohesive, cut-resistant powder may also be used. This cohesiveness can also result from the addition of a binder material or an auxiliary material.

The "excess amount" or "overfeed" is the amount of particulate material that is pushed in the coating travel at the end of the construction field in front of the coater.

"Coater" or "recoater" is the unit by which the particulate material is applied to the construction field. According to the invention, this coater is designed as a rotating roller, which is guided in an opposite movement over the construction field.

The "construction container" is a device permanently installed or removable in the device, which receives the construction material discharged during the building process and prevents it from flowing out into the production device. In the simplest case, the construction container does not have to have any walls and the powder runs out on a plate.

The "printhead" is usually composed of various components. Among other things, these are the printing modules. These are aligned relative to the printhead. The printhead is aligned relative to the machine. Thus, the position of a nozzle can be assigned to the machine coordinate system.

"Box volume" of a component is the volume of the smallest cuboid, in which the component can be brought without a surface of the cuboid is penetrated by the component.

"Binder jetting - layer construction method" is to be understood that layer by layer powder is applied to a construction platform, in each case the cross sections of the component are printed on this powder layer with a liquid binder, the position of the build platform is changed by a layer thickness to the last position and this Repeat steps until the component is ready.

"Slider mechanism" or "slider" in the sense of the disclosure is e.g. a flat plate on which the defined amount of particulate material is deposited and then the defined amount of particulate material is moved before the coating roller before each coating operation.

In the sense of the disclosure is a "defined amount of particulate material", which is presented by means of slide and refill and is then stored in front of the coater roller; this quantity includes the volume of the applied layer and the overfeed. A defined quantity of particulate material can be obtained in its constancy and defined amount by traversing a refill (a particle reservoir with closure) at a defined distance from the slide and the distance between the lower edge of the refiller and the upper edge of the slide and the diameter or surface of the refiller defines the volume of particulate matter to be dispensed. Since the distance is only very small, the angle of repose of the particulate material at the edges will only lead to a very small deviation or variance. The defined amount of particulate material will thus be very constant. The amount required for a particle layer and the desired overfeed can also be calculated easily over the mass of the machine, which is familiar to any person skilled in the art. He then only has to determine how much overfeed should be applied to determine the total amount of dosage and to define and adjust the distance of the refill to the slide accordingly.

"Overfeed" in the sense of the disclosure is the proportion of the particulate material that is not required for the creation of the particle layer and is moved into a designated area or container at the end of each coating run of the coater. The overfeed is important for a high quality coating. Too little overfeed causes the particle layer to be incomplete at the end of the coating run is executed and it comes in the next step of selective solidification inaccuracies because particulate material to solidify is missing. If the overfeed is chosen too large, one obtains too large a powder roller, which does not roll satisfactorily in front of the coater roller and thus leads to a faulty coating and, for example, unevenness and inaccuracies of the particle layer. An overfeed of 10 to 40% in addition to the layer volume or 10 to 30% or 10 to 20% is advantageous.

• 1 gibt einen 3D-Drucker gemäß dem Stand der Technik wieder. Der 3D-Drucker weist die Vorrichtungsteile Druckkopf (100), Beschichter (101) und eine Bauplattform (102) zur Zustellung einzelner Schichten (107) auf. Der Pulverkuchen wächst in einem Baubehälter (104) während des Prozesses. Das Ergebnis ist ein dreidimensionales Bauteil (113), das aus dem losen, das Bauteil umgebenden Pulver entpackt werden kann.

Various aspects of the invention are described below:

• 1 is a 3D printer according to the prior art again. The 3D printer shows the device parts printhead ( 100 ), Coater ( 101 ) and a build platform ( 102 ) for the delivery of individual layers ( 107 ) on. The powder cake grows in a construction container ( 104 ) during the process. The result is a three-dimensional component ( 113 ), which can be unpacked from the loose powder surrounding the component.

The device according to the invention has a powder coater ( 101 ) on. With this particulate material on a building platform ( 102 ) and smoothed ( 2 (a) ). The applied particulate material can consist of various materials. For example, sand, ceramic powder, metal powder, plastic, wood particles, fiber material, celluloses, lactose powder, etc. may be used. The flow properties of these materials can vary greatly. Various coating techniques allow the layer formation of dry, free-flowing powders over cohesive, cut-resistant powders to liquid-based dispersions. The height of the powder layers ( 107 ) is determined by the build platform ( 102 ) certainly. It is lowered after applying a coat. During the next coating process, the resulting volume is filled and the supernatant smoothed. The result is a nearly perfectly parallel and smooth layer of defined height.

After a coating process, the layer is dried by means of an inkjet printhead ( 100 ) is printed with a liquid ( 1 ( 105 ) 2 B) ). The printed image corresponds to the section through the component in the current height of the device. The drops of liquid ( 109 ) impinge on the particulate matter and the liquid diffuses slowly into the powder.

The new layer thus produced is then lowered by one layer thickness. Then the process of layer production starts from the beginning and it is repeated until the desired height is reached and thus the desired parts are completed.

After the construction process, the component is embedded in the powder. Depending on the device, the construction container in which the component is located, an integral part of the printing system, or it is removable.

A removable container has the advantage that the unpacking of the component does not have to take place in the printing system. Thus, with a number of construction containers adapted to the production process, a very good utilization of the printing system can be achieved.

The aim of the coating process is a smooth homogeneous layer as possible, which can be printed by the printhead in the subsequent step and allows homogeneous component properties.

The result of the coating process depends decisively on the powder used. In this case, the flow properties, the particle size, the density, the tendency to charge or agglomerate and the compressibility are of importance for the process.

Free-flowing powders, comparable to granulated sugar, are easy to apply in thin layers when choosing suitable parameters. Since the forces between the particles are low, volumes can be easily divided and new surfaces created without much energy. Such powders can be smoothed out well with a squeegee, even with the assistance of vibrations.

Most such powders have a large grain size. That's why very thin layers are not possible.

Smaller grains in a powder have the disadvantage that between the individual, compared to coarse powders much more numerous particles, forces occur that make the powder summed up the poorly flowing and make shearing possible only with increased force. The poor flow characteristic is particularly evident in simple pouring. Flour-type particulate materials have significantly lower bulk densities than those that flow well.

The aim of the layered construction of three-dimensional models is to store the particle material process reliable and move through all parts of the device to then apply it in a geometrically clean layer with the highest possible density while generating the lowest possible shear forces on the construction field.

Concerning. The storage process means that the powder does not change its properties as far as possible and that it passes through the storage unit attached conveyor element can be detected safely.

The elements should influence the powder as little as possible. Such an influence could be compressions that cause agglomerates in the powder. Such agglomerates are much stronger than loose powder and form scratches on the construction field during the coating process.

Such influence can be triggered by massive compression or vibration. The particles come into so intimate contact that they almost interlock with each other and form a connection.

The strength of the powder is heavily dependent on such influences in the history. Positive acts such as sifting or loosening of the powder. Particles are separated and air is introduced into the powder, which promotes flow. Negative effect vibrations in parts of the device in which the powder can not drain and massive compressions, for example by moving parts of the device.

Each powder has a certain history, and a ground state of the flow properties and agglomeration tendency can not actually be defined. Rather, the powder properties occur in a range that every part of the device must cope with.

According to the invention, the coating process can be divided into two basic functions: presentation of a quantity of powder in front of the roller and distribution of the powder on the construction field.

The distribution of powder on the construction field with an opposing roll is state of the art and described in detail in the patent literature. It is advantageous for the distribution to move the smallest possible amount of powder. Larger amounts act due to gravity and due to strong movements on already generated layers and can, for example, favor shear forces that adversely affect the geometry of the three-dimensional moldings.

According to the invention, a slide mechanism for the defined metering of the particulate material is advantageously used.

In one aspect, the disclosure relates to a coater apparatus suitable for a 3D printing machine, characterized in that the apparatus comprises a coating roller and a slider.

In a further aspect, the disclosure relates to a method for producing 3D molded parts, comprising the steps of: all steps required for a 3D printing method, wherein at the beginning of a coating run a defined amount of particulate material is brought before the roller and possibly further particulate material during a Passage is brought to the coating in front of the roller.

One advantage of the invention is that particulate material can be stored in a defined amount gently before the roll (coater roll) without substantially affecting it. It can be achieved according to the invention that the structure is compact and does not unnecessarily affect the size of the system. Reproducible ratios are also achieved because the amount of feed from dosage to dosage is substantially the same.

According to the invention, a slider mechanism is used for this purpose. By a filling device while a quantity of powder (particulate material) is metered onto a slider. The amount of dosage is limited by the fact that the powder from the openings of the filling device spreads on the slider only limited perpendicular to the direction of gravity.

The coater with the slide mechanism is brought to the start of the construction field after the filling process. Now the slider is moved. The powder is prevented by a wall perpendicular to the direction of movement of the slider to follow the movement of the slider, and the powder falls into the opening gap which the slider releases. Guide plates can thereby guide the powder in front of the roller and slow the movement.

The movement space of the slider and the height of the powder through the filling process define the amount of powder reaching the roller.

The device makes it possible to bring the powder without vibrations or strong compressions in front of the roller. The submitted quantity can be defined exactly. The structure is compact and can be carried along with the coater.

Other aspects that may be combined with the apparatus described above or with the method described above will be described below.

The device may further be characterized in that
the slider height adjustable and / or his movement is adjustable, and / or
the slide can be done by pneumatic means, or / and
a defined amount of particulate material can be metered and dispensed before the coater roll, preferably with Dosierschwankungen of less than 20%, preferably less than 10%, or / and
the device comprises a rotating coater roll which can be guided in an opposite movement over the building field, or / and
the device comprises at least one wiper plate, a guide plate, a seal, preferably a rubber seal or brush seal, and / or a material brake plate, and / or
the stripper plate, guide plate and / or the brake plate material are adjustable in position, and / or
the device has a particulate material supply, and / or
the particulate matter supply comprises a reservoir.

The method may be further characterized in that the roller is guided in an opposite movement over the construction field, and / or
the applied particulate material is smoothed, and / or
Excess particulate material is spent after each crossing of the coater in a surplus container, and / or
an overfeed of 10 - 40%, preferably 10 - 30%, more preferably 10 - 20%, is used in addition to the layer volume.

embodiment

The following is the sequence of a construction process when using a coater according to the invention ( 101 ):

In the printing machine, a construction container ( 104 ) brought in. The build platform ( 102 ) can be mechanically connected by a clamping device with the vertical axis of the machine. Following the connection, the build platform ( 102 ) brought to the top position.

The still empty building platform ( 102 ) is now filled with powder by the coater until a smooth plane in the plane of movement of the coater ( 101 ) has arisen. For this purpose, several coating operations are performed.

Each coating process is started with a filling process. A uniformly filled with powder container ( 401 ) is opened, the slide of the coater ( 500 ) in the direction of gravity directly under the refill container ( 401 ) is located.

The refill container ( 401 ) is opened via an opening mechanism ( 402 ) and powder runs on the slide ( 500 ). In the case of poorly flowable powders, the outflow can be promoted by vibrations or other fluidization of the powder.

On the slider, the powder spreads under the openings of the refill container ( 401 ) out. The spreading stops at a certain distance to the refill opening. This distance from the opening depends essentially on the flow characteristics of the powder and the distance between the refill container opening (FIG. 401 ) and the slider ( 500 ). Usual distances range from 1 to 10 mm. The spread in extremely poorly flowable material is around 3 mm (10 mm distance). With good flowable material can occur here 20 mm.

The spread determines the dosed amount ( 403 ). Limitations in the area below the refill can more accurately restrict the amount. Dosing fluctuations of less than 20% are preferably achieved. Particularly preferably, fluctuations of less than 5% are achieved.

The filled coater ( 101 ) is now moved over the construction field to the start position. For this, the construction field ( 102 ) to prevent damage to already printed layers.

When the starting position is reached, the filling of the coater ( 101 ) in front of the roller ( 300 ). For this purpose, a pneumatic drive ( 502 ) the slider in the direction of a vertical wall ( 504 ) drawn. This opposite to the direction of movement of the slide ( 500 ) vertical wall has a seal against the slider.

In one embodiment, the wall ( 504 ) only a gap seal on. The "sealing effect" is only achieved in that the distance between the slide and the wall is low. In this case, distances of less than 2 mm are suitable. Even more preferably less than 1 mm.

Another embodiment has here a rubber seal. This touches the slider and seals securely against the powder as it moves. Likewise, this seal may be designed as a brush or executed from other materials known for such purposes.

The powder ( 505 ) now falls below the slide level on guide plates ( 503 ). These brake the downward movement of the powder, lead the powder directly in front of the roller ( 404 ) and prevent too much dust.

The position of the coater ( 101 ) is selected so that the ejection operation takes place in an area of the construction field in which there are no components. This can cause damage to already created layers ( 107 ) be avoided.

Now the coating process begins. The opposite rotation of the roller ( 300 ) is turned on first. In addition, the coater is set in motion in the direction of the construction field.

Due to the opposite rotation, the powder material rolls in front of the roller ( 300 ). The volume of the layer is filled in ( 301 ).

The smoothing of the layer is in theory defined by the contact line of the powder with the roller. Depending on the bearing clearance and geometry, however, a certain function, in the sense of the envelope of the movement, is displayed on the construction field.

When the coater reaches the end of the construction field, no more powder is withdrawn for filling the layer from the amount in front of the roller. The surplus remaining, the overfeed ( 303 ), falls into a waste chute at the end of the movement ( 302 ).

• • Beschichter mit einem Schieber und einer Walze
• • Schieber, dessen Bewegungsweg einstellbar ist
• • Schieber, der höhenverstellbar ist, um die Menge des dosierten Materials zu variieren
• • Beschichter mit einem Abstreifblech
• • Beschichter mit einem Abstreifblech mit einer Dichtung
• • Beschichter mit einem Abstreifblech mit einer Filz-Dichtung
• • Beschichter mit einem Abstreifblech mit einer Gummi-Dichtung
• • Beschichter mit einem Abstreifblech mit einer Bürsten-Dichtung
• • Abstreifblech, dessen Lage verstellbar ist um die dosierte Menge zu variieren
• • Beschichter mit einem Blech zum Abbremsen des fallenden Partikelmaterials

In other aspects, the device or method according to the disclosure has individual features as follows or a combination thereof:

• • Coater with a slider and a roller
• • Slider whose travel is adjustable
• • Slider that is adjustable in height to vary the amount of dosed material
• • Coater with a scraping plate
• • Coater with a scraper plate with a gasket
• • Coater with a scraper plate with a felt seal
• • Coater with a scraper plate with a rubber seal
• • Coater with a scraper plate with a brush seal
• • Scraper plate whose position is adjustable to vary the dosed quantity
• • Coater with a metal sheet for braking the falling particulate matter

LIST OF REFERENCE NUMBERS

100

printhead

101

coaters

102

building platform

103

component

104

Building container / Jobbox

105

Printhead Bahn

106

Beschichterbahn

107

layers

108

Path of the build platform ( 102 )

109

binder drops

110

Powder for filling the layer

111

Baufeld

112

Gap in the coater for powder discharge

113

Powder supply in the coater

200

infrared Heaters

300

Beschichterwalze

301

Layer volume to be filled

302

Overfeed receiving shaft

303

overfeed

400

pusher

401

Refill

402

Opener of the refill

403

Dosed amount of powder

404

Material in front of the roller

500

pusher

501

frame

502

pneumatic drive

503

sheet guide

504

Vertical scraper wall

505

Falling powder

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

• EP 0431924 B1 [0002]
• US 5387380 [0012]
• DE 10117875 C1 [0013]

Claims (10)

Coater device suitable for a 3D printing machine, characterized in that the device comprises a coating roller and a slider. Device after Claim 1 , characterized in that the slide height adjustable and / or its movement path is adjustable. Device after Claim 2 , characterized in that the slide can be made by pneumatic means. Device after Claim 1 . 2 or 3 Characterized in that a defined amount of particulate matter can be dosed and released before the Beschichterwalze, preferably with metering fluctuations of less than 20%, preferably less than 10%. Device after Claim 1 - 4 , characterized in that the device comprises a rotating coating roller which can be guided in an opposite movement over the construction field. Device after Claim 1 - 5 , characterized in that the device comprises at least one Abstreifblech, a guide plate, a seal, preferably a rubber seal or brush seal, and / or a material brake plate, preferably characterized in that the Abstreifblech, guide plate and / or the material brake plate are adjustable in position. Device after Claim 1 - 6 , characterized in that the device comprises a particulate material supply. Device after Claim 1 - 7 , characterized in that the particulate matter supply comprises a reservoir. A method for producing 3D molded parts, comprising the steps of: all the steps required for a 3D printing process, wherein at the beginning of a coating run a defined amount of particulate material is brought in front of the roller and if necessary further particulate material is brought during a crossing for coating in front of the roller , Method according to Claim 9 wherein the roller is guided in an opposite movement over the construction field or / and wherein the applied particulate material is smoothed, and / or wherein excess particulate material is transferred to a surplus container after each passage of the coater, and / or wherein an overfeed of 10 - 40%, preferably from 10 to 30%, more preferably from 10 to 20%, in addition to the layer volume is used.

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