DE102018007812A1 - Coater for selective laser sintering or selective laser melting - Google Patents

Abstract

An improved coater for the SLM or SLS process is described. The coater preferably has a large powder receptacle (49) which holds material powder (6), which is preferably brought over the outer edges of the coater with the doctor blade (8) or also falls through other gaps, especially in the area of the installation space (48) . The powder overflow vessel is not required. The invention improves the possibilities for cleaning the coater, which also allows a faster change from one type of material to the next.

Description

State of the art and definition of important terms for the description

The selective laser melting process (SLM) or selective laser sintering process (SLS) is a generative manufacturing process. In the process, the material to be processed is applied in powder form in a thin layer on a substrate plate. The powdery material (also called “the powder” for short) is locally melted (with SLS) or completely remelted (with SLM) by means of electromagnetic radiation (especially laser radiation) and forms a solid material layer after solidification.
The substrate plate is then lowered by the thickness of a layer and powder is applied again. This cycle is repeated until all layers have melted or remelted. The finished molded article is cleaned of the excess powder and can then be used.

Possible powdery materials are powdery metals (copper, steel, cobalt-chrome, titanium, tungsten, aluminum, gold) and other materials (glass, ceramic, plastic).

A system for SLM or SLS (hereinafter referred to as "system") contains, as important components, a computing and evaluation unit, a radiation unit, a mirror deflection unit and a coater.

The invention is concerned exclusively with the coater.
The job of the coater is to lower the substrate plate and then to apply a new layer of powder evenly and evenly.

In a view of the coater is shown (bottom left). In this supervision there are two cutting planes ( 13a , b ). Furthermore, in to see a cross-section at the top left and top right. The cross-section at the top left relates to the cut ( 13a ) supervision. The cross-section at the top right relates to the cut ( 13b ).

The coater has a space ( 3rd ) on. The powder is applied by applying a layer of the powdery material ( 6 ) (hereinafter also referred to as "powder") in the installation space. The floor block of the installation space ( 5 ) lowered with the substrate plate.

The installation space is laterally limited by a partition, transverse walls and longitudinal walls. The dividing wall, the transverse walls and the longitudinal walls form a rigid frame, which acts as a "base frame" ( 10th ) referred to as.

The powder layer is applied using a squeegee ( 8th ). The squeegee moves over the surface of this base frame, which acts as the "construction table level" ( 27 ) referred to as. The squeegee takes in the primary direction of movement of the squeegee ( 15 ) in a powder intake zone ( 28 ) Powder, pushes it in the form of a powder accumulation ( 23 ) in front of itself and releases the powder in the installation space. After the primary movement of the squeegee, the secondary movement of the squeegee takes place, which serves to move the squeegee back into the starting position.

The doctor blade can have a linear movement (as in the example of the ) or perform a rotary movement.

The powder can reach the area of the powder receiving zone in various ways.

On the one hand, a powder quantity can be dispensed from a dosing system (e.g. dosing screw), which is located above the powder intake zone. The powder then falls on the construction table level, is picked up by the squeegee and also deposited in the installation space.

On the other hand, the coater can use a storage room filled with powder ( 2nd ) in the powder intake zone, as in shown. Then the floor block of the storage room ( 4th ) raised so that a quantity of powder can be picked up by the squeegee.

The lowering of the floor block of the installation space and, if appropriate, the lifting of the floor block of the storage space takes place with linear adjusters, which are attached below the floors of the installation space or the storage space.

In the process of squeegee, there may still be powder on the squeegee after painting over the installation space, which is excess. This powder is placed in a removable powder overflow container ( 11 ) spent. After sweeping over the powder overflow vessel, the doctor blade reverses and moves back to its cycle starting point beyond the storage space or beyond the zone from which powder falls from the metering screws.

The lower edge of the squeegee slides over parts of the surface of the coater in each cycle, which are referred to below as the "travel area" ( 18th ).

The base frame often has a powder retention level on the top ( 17th ) on. This is an increase in cross and Longitudinal walls beyond the level of the doctor blade level, which holds back the powder and limits its spread to the side.

The melting takes place in the top powder layer ( 1 ) of the installation space instead. Below this are on the substrate plate ( 12th ) one or more molded parts already built and embedded in powder ( 14 ).

After the shaped body or the shaped bodies are finished, they are removed from the installation space on the substrate plate with the shaped bodies. The size of the installation space is decisive for the maximum possible size of the shaped bodies.

The molded body is then separated from the substrate plate. The remaining loose powder is also removed from the installation space. This remaining powder is contaminated with larger particles by splashes of the previously liquid material.

The powder is usually either sent to a recycling plant, where fine powder is produced again, or it is sieved out.

In the case of sieving, the fine powder fraction falling through the sieves can be stored with the exclusion of oxygen and reused in a later construction process. Only the sieved larger powder particles are sent to the recycling plant.

As an X dimension, also as a "length" (number 24th in ), the spatial direction parallel to the feed direction of the squeegee is designated. However, the considerations are not limited to a linearly moving doctor blade. In the case of a circular squeegee, X is given the character of an (azimuthal) angle (number 24th in ). All considerations can also be transferred to a circular squeegee.

As a Y dimension, also as a "width" (number 25th in ), the horizontal dimension is called perpendicular to the feed direction. In the case of a circular movement of the squeegee, Y is the radial coordinate (number 25th in ).

As Z dimension (height) ( 26 ) is the vertical direction.

Description of the invention

The invention consists in a fundamentally different arrangement of the components of the coater. An embodiment is in shown; a coater according to the invention is shown here. The lower left part of shows a top view, above the top left the front view, top right the side view.
shows further features of the invention, in supervision of a coater.

The aim of the invention is to simplify the exchange of powder when changing from one type of powder to another, to simplify cleaning of the coater, and to save costs on components and seals.

1. a) vom einem Sammelspalt oder einer Außenkante an der bauraumfernen Querkante,
2. b) von einem Sammelspalt oder einer Außenkante an einer der Längsseiten der Bautischebene,
3. c) aus dem Spalt zwischen Grundrahmen und Bodenblock des Bauraums,
4. d) ggf. aus dem Spalt zwischen Grundrahmen und Bodenblock des Vorratsraums,
5. e) ggf. aus einem Spalt in einem Passstück des Bauraums oder des Vorratsraums,
6. f) aus dem Bauraum bei herausgefahrenem Bodenblock oder
7. g) ggf. aus dem Vorratsraum bei herausgefahrenem Bodenblock.

Point 1 the summary relates to a coater for SLM or SLS, with a powder collecting vessel that collects powder that is still on the doctor blade after the installation space has been covered
in which
the powder collecting vessel also collects powder that falls down at least in one of the following zones

1. a) from a collecting gap or an outer edge on the transverse edge remote from the installation space,
2. b) from a collecting gap or an outer edge on one of the long sides of the construction table level,
3. c) from the gap between the base frame and the floor block of the installation space,
4. d) if necessary from the gap between the base frame and the floor block of the storage room,
5. e) if necessary from a gap in a fitting piece of the installation space or the storage space,
6. f) from the installation space with the floor block extended or
7. g) if necessary from the storage room with the floor block extended.

In the invention, a removable powder collecting vessel ( 49 ) in place of the powder overflow vessel ( 11 ). The powder collecting vessel is below the construction table level ( 27 ) appropriate. It takes over the function of the powder overflow vessel and advantageously at least one further function.

We look at in supervision , and first the area of the "transverse edge near the installation space" ( 20th ). It is the edge that the squeegee reaches in its primary direction of movement after sweeping over the installation space. It is the right edge of the base frame in the and . Powder arrives in this area when the squeegee has already swept the installation space and is still pushing powder in front of it. The powder is excess and should be removed.

For example, the powder falls through a "collecting gap near the installation space" ( 34 in ) in the powder collector.

The outer edge of the base frame can also replace the collecting gap. In this case, the powder retention level must be lowered on the transverse edge near the installation space. This advantageously also facilitates cleaning of the surface of the base frame, since the powder retention step leads to an inner edge ( 16 ) which is difficult to clean (e.g. with a suction device). If an area of the inner edge is lowered, other areas of the inner edge can also be cleaned more easily because the powder can then be pushed along the edge (for example with a brush) to the lowered area.

The powder collector must be arranged and expanded so that the transverse edge near the installation space lies above the powder collector. This creates a powder trap ( 43 ).

The innovation lies in the fact that the powder collector also collects powder from other sources, according to the invention from at least one of the following zones:

from a collecting gap or an outer edge on the transverse edge remote from the installation space

The transverse edge remote from the installation space ( 21 ) is the edge that lies opposite the transverse edge near the installation space. It is located near the cycle start point, at the beginning of the primary movement of the squeegee. In and is the left edge in the top view.

The transverse edge, which is remote from the installation space, can also be designed as an outer edge in such a way that powder falls down over it into the powder collecting vessel.

For this purpose, the powder collecting vessel must first be preferably arranged and expanded such that both the transverse edge near the installation space and the transverse edge remote from the installation space lie above the powder collection vessel. This results in a relatively large powder container.

In the collecting vessel is located below the outer edges of the base frame and, in order to catch the falling powder, has a length which extends beyond the length of the base frame, whereby a powder trap ( 43 ) is formed, in which the excess powder is doctored.

Alternatively, the powder is collected by a funnel construction that forwards it into a smaller powder collection vessel.

In addition, the powder retention level should be reduced in this area. This makes the device easier to clean because internal edges ( 16 ) be avoided.

If the secondary movement of the squeegee extends beyond this edge before the direction of movement is reversed, the excess powder falls into the powder collecting vessel with each cycle.

Removing excess powder on the side away from the installation space facilitates cleaning of the coater, since it would accumulate in front of the powder retention stage. Such powder is captured in small amounts in the installation space and possibly in the storage space during the secondary movement of the doctor blade and brought to the side remote from the installation space.

If the squeegee does not move over the edge, a corresponding cleaning after the construction process is still easily possible, the powder z. B. is pushed over the edge with a brush.

A collecting gap can take over the function of the edge. It must run parallel to the edge. we refer to it as the "collecting gap away from the installation space" (section 35 in the embodiment of ).

from a collecting gap or an outer edge on at least one of the long sides of the construction table level

The outer edges on the two long sides of the construction table level can also be designed in such a way that powder falls over them into the powder collecting vessel. For this purpose, the powder collecting vessel must first be arranged and expanded such that both the transverse edge near the installation space and the respective longitudinal edge ( 22 ) over the powder collector.

In the collecting vessel is located below the outer edges of the base frame and, in order to catch the falling powder, also has a width which extends beyond the width of the base frame. This creates the powder trap here ( 43 ).

As an alternative, a funnel construction can be used as described under (a).

The powder retention level should be lowered in this area. This makes the device easier to clean because internal edges ( 16 ) be avoided.

The width of the squeegee can also be increased beyond the longitudinal edges of the construction table surface. In this case, no powder can be deposited near these longitudinal edges.

• - von oben durch eine überstehende Rakel abgedeckt ist,
• - nach unten offen für das Pulverauffanggefäß ist
• - zu den Querseiten und zu den Längsseiten hin Kanten hat, auf denen Pulver herabfällt.

Der Grundrahmen kann unter diesen Bedingungen dennoch befestigt werden. In ist dafür eine Befestigung mit schmalen Haltestegen (29) vorgesehen. Die Haltestege können auf ihrer Oberseite dachartig geformt sein, so dass sich dort kein Pulver ablagert, sondern an den Haltestegen vorbei in das Pulverauffanggefäß fällt.Now there is a problem of fixing the base frame because in the case of falling Powder from both longitudinal edges and combination with feature a)
the basic framework

• - is covered from above by a protruding squeegee,
• - is open at the bottom for the powder collector
• - Has edges on the short sides and on the long sides, on which powder falls.

The base frame can still be attached under these conditions. In is a fastening with narrow holding bars ( 29 ) intended. The holding webs can be shaped like a roof on their upper side, so that no powder is deposited there, but falls past the holding webs into the powder collecting vessel.

With such a construction in particular, the coater can be easily cleaned of powder as the base frame is accessible for cleaning.

Instead of the long edge over which the powder falls, a long edge collecting gap can also be used 1 (Digit 36 in ) or longitudinal edge collecting gap 2nd (Digit 37 in ) to serve. These columns are located near the long edge and run parallel to the long edge.

from the gap between the base frame and the floor block of the installation space

The gap between the base frame and the floor block of the installation space can have leaks. Sealing against powder would be difficult. Furthermore, in spite of the sealing, there should be no adhesive forces of the floor block on the walls of the installation space, because otherwise jerky and unpredictable movements could occur which would have an impact on the desired construction precision. According to the invention, it is accepted that powder can penetrate at this point and fall into the powder collecting vessel.

The powder collecting vessel must preferably be arranged and expanded so that both the transverse edge near the installation space and the installation space lie above the powder collection vessel. As an alternative, a funnel construction can be used as described under (a).

from the gap between the base frame and the floor block of the storage room

The corresponding considerations as for c) also apply to the gap between the base frame and the floor block of the storage room

if necessary from a gap in a fitting piece of the installation space or the storage space

With a coater, it is possible to configure the shape of the installation space or the storage space with fitting pieces and thus adapt it to the geometry of the molded parts to be built. The advantages of such a procedure lie in lower powder circulation and higher speed in construction processes with a smaller storage space.

The installation space adapter preferably has an inner cutout which corresponds to the side walls of the desired installation space.

In this context, the description of the invention filed by the same applicant on the same day the application of this invention “method and apparatus for adapting the installation space geometry in the case of selective laser melting or selective laser sintering” is considered to be contained in full in this description.

The principle is explained with the help of explained. Two different configurations are shown. shows only the basic frame in supervision ( 10th ), the installation spaces ( 3a , 3b ) and the storage rooms ( 2a , 2 B ).

The base frame has a space cutout ( 30th ) on which is greater than or equal to the section defined by the walls of the installation space. By inserting an installation space adapter, this installation space cutout is reduced.

In the illustration above, an installation space adapter A ( 31a ) shown, the inner walls of the installation space 1 ( 3a ) form, while in the illustration below an installation space adapter B ( 31b ) is shown, the inner walls of the smaller space 2nd ( 3b ) form.

In addition, an installation space adapter preferably has a form fit to the installation space cutout. The installation space adapter is fixed in the intended installation position relative to the installation space cutout, so it is not moved through the floor of the installation space. The fixation takes place e.g. by screwing down.

The floor of the installation space must not collide with reduced installation space walls during operation.
A collision can be avoided by using a sufficiently small body (which is referred to as the "installation space floor body"). Its floor area must therefore lie completely within the smallest installation space.

However, some configurations (except possibly the Configuration with the smallest installation space) Powder should escape because the installation space floor does not close tightly.

This problem can be solved by ensuring the tightness against the powder leakage not through the bottom of the installation space, but through various substrate plates, the shape of which is adapted to the associated installation space base area and can be moved with an appropriate gap dimension in the associated installation space.

Another possibility for solving the problem is that different shapes of the installation space block can be configured by installation space floor adapters, which are fixed relative to the installation space floor body in the intended installation position.
According to this embodiment, a construction space floor adapted to the construction space is formed, the construction space floor body having construction space floor fitting pieces which are each supplemented to form floor blocks of the construction space.

An additional feature is the introduction of an intentional gap ( 33 ) in a construction space adapter between the construction space and the powder collecting vessel, which extends over the entire width of the installation space, serves as a powder trap and thus replaces the powder collecting vessel in this configuration. In this case, the primary movement of the doctor blade can be reversed after the gap has been covered and not only after the powder overflow vessel has been covered to return to the cycle starting point. This reduces the driving area ( 18a respectively. 18b ) and assuming a constant travel speed the travel time of the squeegee. The travel time of the squeegee is part of the time required for the construction process, which is advantageously faster overall.

A coater, which also has various storage space base areas with storage space fitting pieces ( 38a , 38b ) can be configured to ensure an adapted powder supply.
Analogous to the procedure for the installation space, different storage space base areas can be configured in order to achieve an intended powder supply function.

The considerations for the configuration of the storage space can be transferred to the configuration of the installation space. In this way, different shapes of the storage space floor can also be configured by means of storage space floor fitting pieces attached to a storage space floor body

Even in the case of a tightly fitting floor block / installation space combination, in the case of tightly closing floor block / storage space combinations or in the case of a tightly closing substrate plate / installation space combination, there is still a problem with escaping powder, e.g. because of the manufacturing tolerances of the components involved or the tolerances when fixing the installation space fitting.

This problem is solved with the second function of the powder collecting vessel according to the invention. For this purpose, the powder collecting vessel must first be arranged and expanded such that the installation space and possibly the storage space lie above the powder collecting vessel. As an alternative, a funnel construction can be used as described under (a).

The powder collecting vessel can also receive the powder emerging from the deliberate gaps, as well as powder from gaps between fitting pieces fixed to one another, between the base frame and a fitting piece fixed to it, or between a base body and a fitting piece fixed to it.

from the installation space with the floor block extended

The coater according to the invention can advantageously have a cleaning mode in which the floor block of the installation space is preferably moved out of the base frame such that its surface is below the base frame and is accessible for cleaning. The cleaning of the floor block can then in a very simple manner, for. B. done with a brush. In this case, powder will fall out of the installation space when moving out and cleaning.
First of all, the powder collecting vessel must be arranged and expanded so that the installation space is above the powder collecting vessel.

Also in this feature, the powder collecting vessel will preferably be arranged lower than in the implementation with other features. When the system is in operation, it makes sense to carry out the cleaning with the powder collecting vessel suspended or inserted so that the powder is collected during cleaning. For this reason, one hand should preferably fit into the area between the base frame and the powder collecting vessel and no other objects should block access for cleaning or the view.

if necessary, from the storage room with the floor block extended

The same considerations apply as for the floor block of the installation space.

• - seitlich neben dem Bauraum angeordnet ist und
• - seine Bewegung mit einer Winkelkonstruktion auf den Bodenblock des Bauraums übertragen wird

Point 2nd the summary describes one
Coater by point 1 , in which
the linear adjuster, which raises and lowers the floor block of the installation space

• - Is arranged laterally next to the installation space and
• - Its movement is transmitted to the floor block of the installation space with an angular construction

According to the prior art, the linear adjuster for lifting and lowering the floor block of the installation space and possibly also the linear adjuster for lifting and lowering the floor block of the storage space are arranged under the installation space or storage space.

The linear adjusters and the associated motors (section 42 in ) for moving the floor block of the installation space are not laid below the installation space floor in this embodiment, but laterally next to the base frame. The motor forces are measured with the help of suitable angle constructions ( 40 ) transferred to the floor block of the installation space.

An embodiment is in shown.
A corresponding representation for a squeegee with rotary adjuster ( 55 ) is in shown. The considerations can also be applied analogously to a doctor blade with a rotary movement.

This advantageously creates space for the powder collecting vessel.
Furthermore, all components below the installation space floor are then advantageously insensitive to falling powder ( 48 ).
It is also advantageous that the powder cannot be deposited anywhere because motors, gears or cables are no longer present.

After all, linear adjusters and motors require less consideration of the size and no consideration of the powder tightness of these components. This can advantageously save costs.

Further comments:

1. 1) In is also the unearverer for the squeegee ( 44 ) laid next to the base frame. It is connected to the squeegee with an angular construction. This makes the base frame more accessible from above.
2. 2) It is necessary to clean a coater
   • • in the area of general machine maintenance, and
   • • to protect powders made of expensive materials, such as gold, from unauthorized access.
   • • Cleaning is of particular importance when changing from one powder material to another. The users of SLM or SLS systems just want systems that can be cleaned in a short time, to be able to change over in a short time and to be able to manufacture workpieces in different materials.
3. 3) The attachment of the powder collecting vessel should be such that the powder collecting vessel is easy to remove. In the example of there is a suspension structure ( 41 ) for easy removal of the powder container after a construction process. The powder collecting vessel is preferably placed, hung or inserted into the suspension structure. The process is even easier than with a powder overflow container ( 11 ) according to .
4. 4) A system can be delivered with several powder collecting vessels, of which however preferably only one is always active. The other powder collection vessels can e.g. serve to store powder from the previous construction process and, for example, be placed, hung or inserted in a base cabinet. For the purpose of storage, the powder collection containers can also be provided with additional airtight lids and with the possibility of sticking on labels or the like. be delivered.

attachment 1 : Summary of important steps of the considerations according to the invention

• - vom einem Sammelspalt oder einer Außenkante an der bauraumfernen Querkante,
• - von einem Sammelspalt oder einer Außenkante an einer der Längsseiten der Bautischebene,
• - aus dem Spalt zwischen Grundrahmen und Bodenblock des Bauraums,
• - ggf. aus dem Spalt zwischen Grundrahmen und Bodenblock des Vorratsraums,
• - ggf. aus einem Spalt in einem Passstück des Bauraums oder des Vorratsraums,
• - aus dem Bauraum bei herausgefahrenem Bodenblock oder
• - ggf. aus dem Vorratsraum bei herausgefahrenem Bodenblock

Coater for SLM or SLS, with a powder collector, which collects powder that is still on the squeegee after the installation space has been covered
in which
the powder collecting vessel also collects powder that falls down at least in one of the following zones

• - from a collecting gap or an outer edge on the transverse edge remote from the installation space,
• - from a collecting gap or an outer edge on one of the long sides of the construction table level,
• - from the gap between the base frame and the floor block of the installation space,
• - if necessary, from the gap between the base frame and the floor block of the storage room,
• - if necessary, from a gap in a fitting piece of the installation space or the storage space,
• - from the installation space with the floor block extended or
• - If necessary, from the storage room with the floor block extended

• - seitlich neben dem Bauraum angeordnet ist und
• - seine Bewegung mit einer Winkelkonstruktion auf den Bodenblock des Bauraums übertragen wird

2 coaters according to point 1 , in which
the linear adjuster, which raises and lowers the floor block of the installation space

• - Is arranged laterally next to the installation space and
• - Its movement is transmitted to the floor block of the installation space with an angular construction

Figure list

• : State-of-the-art coater
• : Example of an embodiment according to point 1 , with zones a, b, c, d, f and g, as well as according to point 2
• : Basic frame in one embodiment according to point 1 , with all zones
• : Basic frame in one embodiment according to point 1 , with zones a and b
• : Example of an embodiment according to point 1 , with zones a, b, c, d, f and g, as well as by point 2nd , with rotary squeegee movement

Reference list

1

top powder layer in the installation space

2nd

Pantry

3rd

Installation space

4th

Floor block of the storage room

5

Floor block of the installation space

6

Powdery material, shown hatched

8th

Squeegee

10th

Base frame

11

Powder overflow vessel

12th

Substrate plate

13

Cutting plane

14

one shaped body or several shaped bodies

15

primary direction of movement of the squeegee

16

inside edge

17th

Powder retention level

18, 18a, 18b

Driving area

20th

transverse edge close to the installation space

21

transverse edge remote from the installation space

22

Long edge

23

Powder accumulation

24th

X dimension or azimuthal angular coordinate

25th

Y dimension or radial coordinate

26

Z dimension

27

Building table level

28

Powder intake zone

29

Landing stage

30th

Installation space cutout

31, 31a, 31b

Installation space adapter

33

deliberate gap

34

Collection gap close to the installation space

35

collecting gap away from the installation space

36

Longitudinal edge collecting gap 1

37

Longitudinal edge collecting gap 2

38a, 38b

Pantry fitting

40

Angular construction

41

Suspension hook construction

42

Linear stage with motor

43

Powder trap

44

Linear adjuster for the squeegee

48

falling powder

49

Powder collector

55

Rotary adjuster for the squeegee

Claims (2)

Coater for SLM or SLS, with a powder collecting vessel that collects powder that is still on the squeegee after the installation space has been covered. The powder collecting vessel also collects powder that falls down in at least one of the following zones - from a collecting gap or an outer edge on the transverse edge remote from the installation space, - from a collecting gap or an outer edge on one of the long sides of the construction table level, - from the gap between the base frame and the floor block of the installation space, - if necessary from the gap between the base frame and the floor block of the storage room, - if necessary, from a gap in a fitting piece of the installation space or the storage space, - from the installation space with the floor block moved out or - if necessary from the storage space with the floor block moved out Coater after Claim 1 , the linear adjuster, which raises and lowers the floor block of the installation space - is arranged to the side of the installation space and - its movement is transmitted to the floor block of the installation space with an angular construction

Images