An additive manufacturing apparatus

Abstract

Described and claimed is an additive manufacturing apparatus for manufacturing three-dimensional workpieces comprising a process chamber with a process chamber bottom and a build cylinder with a build cylinder wall surrounding a carrier. The carrier receives raw material powder. The build cylinder is mechanically decoupled from the process chamber bottom such that a force transmitted from the build cylinder wall to the process chamber bottom during docking of the build cylinder to the process chamber bottom remains below a threshold and / or such that changes in the force exerted on the process chamber bottom by the build cylinder wall during the manufacturing of three-dimensional workpieces are reduced.

Description

[0001] Applicant: Nikon SLM Solutions AG

[0002] Title: An additive manufacturing apparatus

[0003] Our Ref.: SLMP 3809 WO

[0004] Description

[0005]

[0001] The present invention is directed to an additive manufacturing apparatus for manufacturing three-dimensional workpieces. The apparatus comprises a process chamber with a process chamber bottom and a build cylinder.

[0006] 5

[0002] Additive manufacturing of three-dimensional objects if often referred to as 3D-printing. A specific form of additive manufacturing is La- ser-Powder-Bed-Fusion (LPBF). Additive manufacturing apparatuses used for manufacturing three-dimensional workpieces using LPBF generally comprise a process chamber and a build cylinder. The process chamber

[0007] 10 will at least comprise a process chamber bottom that commonly extends generally horizontally, i.e., perpendicular to a vertical axis. The process chamber bottom defines a plane in which the manufacturing of the three-dimensional workpieces from a raw material powder takes place.

[0008]

[0003] The process chamber bottom comprises an opening where a so- called build cylinder is attached to the process chamber during manufacturing of three-dimensional workpieces. The build cylinder comprises a build cylinder wall extending generally in a vertical direction. An inner cross-sectional area of the build cylinder in a horizontal plane is commonly rectangular but could also have other shapes such as a circular

[0009] 20 shape or an oval shape. The build cylinder wall surrounds a carrier. The carrier and the build cylinder wall can be moved relative to each other in the vertical direction.

[0010] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025

[0004] When the layer-building process for creating three-dimensional workpieces commences, the build cylinder wall is in contact with a lower, downward facing surface of the process chamber bottom. The carrier will commonly be in an uppermost position where it is directly ad¬

[0011] 5 jacent to or placed in the opening in the process chamber bottom. First, a layer of raw material powder is deposited on the carrier commonly using a recoater. The raw material which may, for example, be a metal powder, a metal alloy powder or a plastic powder. Subsequently, selected particles of the raw material powder layer are exposed to a high- energy beam. The high-energy beam may be of electromagnetic radiation such as, for example, a laser beam, or may also be a particle beam such as, for example, an electron beam. The high-energy beam selectively sinters and / or melts particles of the raw material powder.

[0012]

[0005] When the first layer has been completed, the carrier is moved

[0013] 15 downwards in the vertical direction allowing the deposition and selective solidifying of a subsequent layer of raw material powder. The three-dimensional objects are manufactured by sequentially repeating the steps of lowering the carrier in the build cylinder, depositing a further layer of raw material powder and selectively sintering and / or melting the parti¬

[0014] 20 cles of the raw material powder.

[0015]

[0006] In order to maintain a high process quality, it is essential that the position of the uppermost layer of the raw material powder is exactly defined so that the location where the radiation beam impinges on the raw material powder matches the intended position which is oftentimes achieved by a recoater moving across the process chamber bottom. Therefore, in the vertical direction the position of the build area is defined by the process chamber bottom. Any change in the deformation of the process chamber bottom along the vertical axis may result in the upper most layer of the raw material powder being either closer or further away

[0016] 30 along the vertical axis from the source of the high-energy beam.

[0017] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025

[0007] In view of the above, it can be considered an object of the present invention to provide an additive manufacturing apparatus for manufacturing three-dimensional workpieces comprising a process chamber with a process chamber bottom and a build cylinder where the odds of

[0018] 5 an unintended deformation of the process chamber bottom are reduced.

[0019]

[0008] The problem is solved by an additive manufacturing apparatus according to claim 1 . Preferred embodiments of the additive manufacturing apparatus are the subject matter of the dependent claims.

[0020]

[0009] According to the present disclosure, an additive manufacturing apparatus for manufacturing three-dimensional workpieces comprising a process chamber with a process chamber bottom and a build cylinder is provided. The build cylinder comprises a build cylinder wall surrounding a carrier for receiving raw material powder. The build cylinder wall ex¬

[0021] 15 tends in a vertical direction. The build cylinder wall and the carrier are configured to be movable relative to each other substantially parallel to a vertical axis. The build cylinder is positioned along the vertical axis in an operating position where the build cylinder wall is in contact with a corresponding contact surface formed on the process chamber bottom. The build cylinder is mechanically decoupled from the process chamber bottom such that a force transmitted from the build cylinder wall to the process chamber bottom during docking of the build cylinder to the process chamber bottom remains below a threshold and / or such that changes in the force exerted on the process chamber bottom by the

[0022] 25 build cylinder wall during the manufacturing of three-dimensional workpieces are reduced.

[0023]

[0010] In other words, the additive manufacturing apparatus is generally made up from a process chamber and a build cylinder that can be

[0024] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 docked to a process chamber bottom of the process chamber. The additive manufacturing apparatus is preferably used for LPBF. The process chamber defines a volume where the three-dimensional workpieces are manufactured.

[0025] 5

[0011] The process chamber at least comprises a process chamber bottom forming a lower or bottom end of the process chamber. Unless specifically defined to the contrary, the terms “up” and “down" as well as corresponding naming of structural parts are defined in reference to the direction of gravity, i.e., parallel to the vertical axis. The process chamber

[0026] 10 may further comprise side walls extending generally in a vertical direction as well as a process chamber top delimiting the process chamber in an opposite direction relative to the process chamber bottom. The process chamber top may, for example, be formed by an irradiation unit providing the high-energy beam in form of a laser beam. In another embodiment, the radiation unit may be placed inside the process chamber, i.e., below the process chamber top or be placed outside of the process chamber, i.e., above the process chamber top.

[0027]

[0012] It is understood that the process chamber may comprise further features such as doors allowing access to the volume defined by the

[0028] 20 process chamber. Further, the process chamber may or may not be sealed from the environment surrounding the additive manufacturing apparatus during manufacturing of three-dimensional workpieces. Further, a recoater may be arranged in the process chamber which is configured to travel perpendicular to the vertical axis across the process

[0029] 25 chamber bottom for depositing a layer of raw material powder.

[0030]

[0013] The process chamber bottom preferably includes an opening defining a build area where the process chamber is open towards a build cylinder that is attached to the process chamber during manufacturing.

[0031] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 The build cylinder itself comprises at least a build cylinder wall which surrounds a carrier. The carrier may, for example, have a rectangular shape in a horizontal plane, i.e., in a plane extending perpendicular to the vertical axis. However, the carrier may also have different shapes in the hor¬

[0032] 5 izontal plane, such as, a circular shape, an oval shape or other regular or irregular shapes depending on the purpose of the apparatus. Since the carrier has to be movable relative to the vertical axis inside the build cylinder wall, an inner surface of the build cylinder wall tightly conforms to the outer shape of the carrier perpendicular to the vertical axis. In other words, in case the carrier has a generally rectangular cross-section perpendicular to the vertical axis, the inner cross section of the build cylinder wall perpendicular to the vertical axis is also rectangular.

[0033]

[0014] The build cylinder wall and the carrier are movable relative to each other, preferably parallel to the vertical axis. The relative move¬

[0034] 15 ment at least allows the distance of the carrier from the process chamber bottom along the vertical axis to be modified during manufacturing of three-dimensional workpieces. Depending on the concrete implementation, the movement can be affected by moving the carrier while the build cylinder wall remains stationary or by moving the build cylinder wall

[0035] 20 and the process chamber while the carrier remains stationary.

[0036]

[0015] During manufacturing of three-dimensional workpieces, the build cylinder is positioned in an operating position. In the operating position, an upper surface of the build cylinder wall touches a contact surface formed on a lower or downward facing surface of the process chamber bottom. The contact surface may be formed by the process chamber bottom itself. Alternatively, additional parts or elements may be mounted to the process chamber bottom. For example, sealing elements or dedicated contact receptacle with mating counterparts on the build cylinder wall may be provided on the process chamber bot¬

[0037] 30 tom.

[0038] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025

[0016] The build cylinder wall may likewise directly engage the contact surface or may comprise additional components attached to the build cylinder wall that improve the contact between the build cylinder wall and the process chamber bottom. Such components may, for example,

[0039] 5 comprise sealing elements such as sealing rings that improve a sealing between the build cylinder wall and the build cylinder.

[0040]

[0017] The build cylinder is not permanently attached to the process chamber bottom but can be detached therefrom, for example, for cleaning or to remove excess powder material and manufactured work¬

[0041] 10 pieces. In some embodiments it is also possible to exchange one build cylinder through another build cylinder. In any case, the build cylinder will generally be moved in a vertical direction upwards until it reaches an operating position where the top of the build cylinder wall is in contact with the contact surface on the process chamber bottom.

[0042] 15

[0018] In the present embodiment, the additive manufacturing apparatus is configured in such way, that the build cylinder is mechanically decoupled from the process chamber bottom when the build cylinder is in the operating position. Mechanically decoupling the process chamber bottom from the build cylinder and, in particular, the build cylinder

[0043] 20 wall requires that during docking of the build cylinder to the process chamber bottom, i.e., when the build cylinder is moved to the operating position, the forces transmitted from the build cylinder wall to the process chamber bottom do not exceed a predetermined threshold. The threshold will be set in a way that the process chamber bottom does not de¬

[0044] 25 form or at least not deform in a substantive manner that would affect the position of the build area where the raw powder material will be deposited. The definition of the threshold will depend on the actual embodiment of the apparatus.

[0045] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025

[0019] Alternatively or additionally, decoupling the build cylinder mechanically from the process chamber bottom requires reducing and, preferably, limiting the change of the forces that are exerted by the build cylinder wall on the process chamber bottom during manufacturing of

[0046] 5 workpieces. Thereby, it is ensured that during manufacturing of workpieces that force changes on the process chamber bottom are mitigated. Preferably, the forces that act on the process chamber bottom due to the contact with the build cylinder wall do not increase beyond an upper threshold beyond which the process chamber bottom could be deformed or damaged. Furthermore, this preferably also requires that the forces do not decrease below a lower threshold which could degrade the contact between the build cylinder wall and the process chamber bottom. Mechanical deformations of the process chamber bottom may, in particular, effect the amount of raw material deposited

[0047] 15 by the recoater on the carrier.

[0048]

[0020] In a preferred embodiment, the contact between the build cylinder wall and the corresponding contact surface formed on the process chamber bottom is established using sealing means providing a sealing function between the build cylinder wall and the corresponding contact

[0049] 20 surface. Using sealing means between the build cylinder wall and the contact surface on the process chamber bottom is, particularly, advantageous, for example, to prevent process gases from leaking out of the volume defined by the process chamber and also to prevent raw material powder from escaping the volume defined by the process chamber and the build cylinder. In case sealing means are used between the build cylinder wall and the contact surface, the mechanic decoupling of the build cylinder wall from the process chamber bottom may, in particular, ensure that sealing force holding the build cylinder wall against the process chamber bottom during manufacturing of workpieces is kept within

[0050] 30 a narrow tolerance or that the changes in the sealing forces caused during the manufacturing process are at least mitigated. The sealing means

[0051] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 can be fastened or attached to either of the build cylinder wall and the contact surface so that it is brought into contact with the other of the build cylinder wall and the contact surface when the build cylinder is brought into the operating position.

[0052] 5

[0021] Within the scope of the present invention, manufacturing of three- dimensional workpieces comprises the layer-building process including at least depositing the raw material powder on the carrier, subjecting the raw material powder to a high-energy beam as well as moving the carrier in the vertical direction but also any parts of the manufacturing pro¬

[0053] 10 cess that precede the layer-building process and any process steps that follow the layer building process. In other words, manufacturing includes essential all process steps between the initial docking of the build cylin- derto the process chamberand the undocking of the build cylinder from the process chamber. This includes, in particular, a heating phase preceding the layer-building process as well as a potential cooling phase when the layer-building process is completed.

[0054]

[0022] In another preferred embodiment, the additive manufacturing apparatus comprises an automated force compensation system for mechanically decoupling the build cylinder from the process chamber bot¬

[0055] 20 tom. The automated force compensation system is configured to reduce during manufacture of the three-dimensional workpieces changes in the forces exerted by the build cylinder wall on the process chamber bottom and / or to limit during docking of the build cylinder of the process chamber bottom changes the forces exerted by the build cylinder wall on the

[0056] 25 process chamber bottom below the threshold.

[0057]

[0023] Hence, in the preferred embodiment a designated force compensation system is foreseen that is a part of the additive manufacturing apparatus. The automated force compensation system provides the

[0058] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 function of mechanically decoupling the process chamber bottom from the build cylinder wall.

[0059]

[0024] Preferably, the force compensation system is configured for limiting the changes in the forces acting on the sealing means providing the

[0060] 5 sealing function between the build cylinder wall and the corresponding contact surface during the manufacturing of three-dimensional workpieces. The force compensation system thus may ensure that a sufficiently high sealing force is maintained between the build cylinder wall and the contact surface. At the same time, the forced compensation

[0061] 10 system may also preferably prevent that the sealing forces do not increase beyond a predetermined threshold which could lead to a deformation of the process chamber bottom.

[0062]

[0025] In a preferred embodiment, the forced compensation system is configured to compensate changes in the forces exerted by the build

[0063] 15 cylinder wall on the process chamber bottom caused by thermally induced changes of the extension of the build cylinder wall in a vertical direction. Thermally induced changes of the extension of the build cylinder wall in a vertical direction occur, for example, during at least one of a plurality phases of manufacturing of three-dimensional workpieces. For

[0064] 20 example, the additive manufacturing apparatus may be configured so that the build cylinder wall heats up in an earlier phase of the manufacturing of three-dimensional workpieces and / or the build cylinder wall cools down in a later phase of manufacturing of three-dimensional workpieces.

[0065] 25

[0026] Hence, in the preferred embodiment the force compensation system aims at compensating or reducing changes in the forces acting on the process chamber bottom that are caused by changes of the length of the build cylinder wall in the vertical direction. These changes in the

[0066] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 lengths may be caused by temperature changes of the additive manufacturing apparatus. For example, before the actual layer-building process begins, the manufacturing apparatus may be heated up to a process temperature. During the heat-up phase the length of the build cyl¬

[0067] 5 inder wall may increase. Consequently, the force acting on the sealing means and also on the process chamber bottom would increase. The force compensation system is configured so that this increase in the force acting on the process chamber bottom remains within predetermined limits. A further increase of the temperature may be observed during the layer-building process due to the high-energy beam heating up the raw material powder. Similarly, when the layer-building process is completed and no additional heat is added to the raw material powder, the additive manufacturing apparatus cools down. During the cooling-down of the manufacturing apparatus, the build cylinder wall may shrink, i.e., its

[0068] 15 extension in the vertical direction is reduced. Consequently, the force exerted by the build cylinder wall on the process chamber bottom also drops. In this case, the force compensation system advantageously reduces a drop in the forces exerted by the build cylinder wall on the process chamber bottom and prevents a drop below a threshold avoiding

[0069] 20 a loss of the sealing contact between the process chamber bottom and the top of the build cylinder wall.

[0070]

[0027] In a further preferred embodiment, the force compensation system is configured to reduce this displacement of the build cylinder wall parallel to the vertical axis caused by friction between the carrier and the build cylinder wall during movement of the build cylinder wall and the carrier relative to each other. Thereby, the force compensation system is configured to reduce changes in the forces exerted by the build cylinder wall on the process chamber bottom.

[0071]

[0028] In other words, in the preferred embodiment, the force compen¬

[0072] 30 sation system mitigates the effect of the relative movement between the

[0073] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 build cylinder wall and the carrier during the manufacturing process. As previously mentioned, after the completion the selected irradiation of the raw powder material in each layer, a relative movement between the build cylinder wall and the carrier is performed so that an additional

[0074] 5 layer of raw material can be deposited on the carrier. Friction between the carrier and the build cylinder wall causes a displacement of the build cylinder wall in the vertical direction. In case the build cylinder wall moves upwards, i.e., towards the process chamber bottom, the displacement would cause an increase of the force acting on the process chamber bottom. Correspondingly, in case the build cylinder wall moves in the downward direction, i.e., away from the process chamber bottom, the displacement of the process chamber bottom would cause a reduction in the force acting on the process chamber bottom. The force compensation system is configured to reduce the changes in the force act¬

[0075] 15 ing on the process chamber bottom by at least limiting or even preventing a displacement of the build cylinder wall due to a relative movement of the carrier.

[0076]

[0029] In a further preferred embodiment, the force compensation system is configured so that the forces exerted by the build cylinder wall on

[0077] 20 the process chamber bottom can be adjusted. Thus, the force compensation system preferably allows to modify the threshold to which the forces are limited that are exerted on the process chamber bottom while the build cylinder is docked to the process chamber. Additionally or alternatively, the force compensation system may allow to adjust the force that acts during the manufacturing process on the process chamber bottom. Further preferably, also the corridor in which these forces change may be adjustable by adapting the compensation means of the force compensation system. This advantageously allows to adjust, for example, a sealing force that acts on the process chamber bottom and

[0078] 30 also to adapt a margin or corridor within which the sealing force changes during manufacturing of the workpieces.

[0079] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025

[0030] In a preferred embodiment, the force compensation system is part of or mounted to a lifting system. The lifting system is configured to lift the releasably attached build cylinder to the operating position and hold the build cylinder in the operating position during manufacturing of

[0080] 5 the three-dimensional workpieces. Thus, in the preferred embodiment a dedicated lifting system is provided that moves the build cylinder upwards to the operating position and keeps the build cylinder in the operating position. The forced compensation system is part of the lifting system. The build cylinder is during manufacturing of the workpieces permanently supported on the force compensation system. This facilitates limiting the forces exerted on the process chamber bottom when the build cylinder is docked to the process chamber bottom.

[0081]

[0031] In an alternative preferred embodiment, the force compensation system is part of or mounted to a cylinder docking station. The cylinder

[0082] 15 docking station is configured to hold the build cylinder in the operating position during the manufacturing of three-dimensional workpieces. Hence, in the preferred embodiment, the additive manufacturing apparatus comprises a dedicated docking station which is provided for holding the build cylinder adjacent to the process chamber. The cylinder

[0083] 20 docking station does preferably precisely defines the operating position. The force compensation system in this embodiment particularly serves to mitigate any changes in the forces exerted on the process chamber bottom during manufacturing of the workpieces. However, the force compensation system may also limit the forces exerted on the process chamber bottom when the build cylinder is attached to the docking system and thereby docked to the process chamber bottom.

[0084]

[0032] Preferably, the additive manufacturing apparatus comprises a carrier positioning means for moving the carrier parallel to the vertical axis. The carrier positioning means is further configured for lifting the build

[0085] 30 cylinder to a docking station with the carrier, docking the build cylinder

[0086] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 to the docking station and detaching the build cylinder wall from the carrier positioning means when the build cylinder has been docked to the docking station.

[0087]

[0033] In other words, in the preferred embodiment, no dedicated lifting

[0088] 5 system for the build cylinder wall is provided. Instead, the build cylinder wall is lifted to the operating position together with the carrier by a carrier positioning means. The carrier positioning means may, for example, be formed by a linear drive such as a spindle and drive. For moving the build cylinder to the operating position, the build cylinder wall is coupled to the carrier so that relative movement between the carrier and the build cylinder wall is prevented. The build cylinder wall is moved upwards towards the cylinder docking station. Once it has being docked or attached to the docking station, the build cylinder wall is decoupled from the carrier. This allows the carrier positioning means to move the carrier

[0089] 15 independently of the build cylinder wall. During manufacturing of three- dimensional workpieces, the carrier remains detached from the build cylinder wall and is, thus, moved relative to thereto. When manufacturing of the workpieces has been completed and the build cylinder shall be undocked from the docking station, the carrier is again attached to the

[0090] 20 build cylinder wall such that the build cylinder wall can be decoupled from the cylinder docking station and moved downwards in the vertical direction away from the process chamber bottom.

[0091]

[0034] In another preferred embodiment, the force compensation system comprises a plurality of length-adjustable connection means supporting the build cylinder wall in the operating position. The length-ad- justable connection means are configured to automatically change their extension in the vertical direction when the forces exerted by the cylinder wall on the process chamber bottom change to at least partially compensate the change in the forces exerted by the build cylinder wall

[0092] 30 on the process chamber bottom.

[0093] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025

[0035] Hence, in the preferred embodiment, the build cylinder is mechanically decoupled from the process chamber bottom using a plurality of length-adjustable connection means. For example, the force compensation system may comprise four length-adjustable connection

[0094] 5 means. The length-adjustable connection means may be part of the lifting system orthe cylinder docking station and hold the build cylinderwall in the operating position. In order to enable the mechanical decoupling of the build cylinder wall from the process chamber bottom, the length- adjustable connection means automatically change their length or extension in the vertical direction to compensate changes in the force that the build cylinder wall exerts on the process chamber bottom. Automatically in these contacts excludes any user input that would be necessary to change the length of the length-adjustable connection means. It is rather understood, that the length-adjustable connection means inher¬

[0095] 15 ently respond to changes in the forces that are generated by the build cylinder wall. This could require either an active control or a passive response.

[0096]

[0036] By changing their length, the length-adjustable connection means advantageously compensate changes in the extension of the

[0097] 20 build cylinder wall that are caused by temperature changes as well as changes in the position of the build cylinder wall caused, for example, by a movement of the carrier or during the docking of the build cylinder to the process chamber. Preferably, the length-adjustable connection means are configured to reduce their extension in the vertical direction when the forces exerted by the build cylinder wall on the process chamber increase. Such a length-adjustable connection means would necessarily be configured to extend its extension in the vertical direction when the forces exerted by the build cylinder wall on the process chamber bottom decrease. In the present embodiment, the build cylinder wall

[0098] 30 rests on the length-adjustable connection means. Thus, gravitational

[0099] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 forces caused by the build cylinder wall cause the length-adjustable connection means to be reduced in size.

[0100]

[0037] In an alternative preferred embodiment, the length-adjustable connection means are configured to automatically increase their exten¬

[0101] 5 sion in the vertical direction when the forces exerted by the build cylinder wall on the process chamber bottom increases. Consequently, the length-adjustable connection means are configured to automatically decrease their extension in the vertical direction when the forces exerted by the build cylinder wall on the process chamber bottom decrease. In

[0102] 10 the preferred embodiment, the build cylinder wall does not rest on the length-adjustable connection means but is rather suspended by the length-adjustable connection means. The length-adjustable connection means thus enable an increase in the distance of the position where the connection means is supported on the length-adjustable connection means from the process chamber bottom.

[0103]

[0038] In a preferred embodiment, a change in extension of the length- adjustable connection means in a vertical direction is limited to prevent the contact between the build cylinder wall and the process chamber bottom from breaking. In the exemplary embodiment, the length-adjust-

[0104] 20 able connection means allows the connection means to only increase or decrease its lengths within predetermined limits. These limits serve to ensure that in any case the build cylinder wall always remains in contact with the process chamber bottom.

[0105]

[0039] For example, in case the length-adjustable connection means in¬

[0106] 25 creases its lengths with increasing forces acting on the process chamber bottom, this could result in the build cylinder wall from losing the contact to the process chamber bottom if, for example, a downward force pulls the build cylinder wall away from the process chamber bottom. While in

[0107] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 such a case the length-adjustable connection means will aim to decrease its extension and thereby compensate this downward force, the downward force may exceed the ability of the connection means to adjust its length. In such a case, a travel-stop or limited reduction in the

[0108] 5 extension of the length-adjustable connection means ensures there is at least a minimum contact remaining.

[0109]

[0040] Similarly, in case the length-adjustable connection means is configured to reduce its extension in the vertical direction when the forces exerted by the build cylinder wall on the process chamber bottom in¬

[0110] 10 crease, this reduction needs to be limited if the downward force acting on the build cylinder wall cannot be compensated by the length-adjust- able connection means. For example, a length-adjustable connection means which is configured to reduce its extension in the vertical direction when the forces on the process chamber bottom increase may only be able to compensate forces to a certain value. If that value is exceeded, the contact between the process chamber bottom and the build cylinder wall could break. It may then be preferable to let the forces on the process chamber bottom increase instead of risking that the contact between the build cylinder wall and the process chamber bottom is lost.

[0111] 20

[0041] In a preferred embodiment, a maximum and / or minimum extension of the length-adjustable connection means in the vertical direction can be adjusted and / or when the change of length extension of the length-adjustable connection means in the vertical direction per unit force can be adjusted. Adjusting either the limits within which the length-

[0112] 25 adjustable connection means can change its extension in the vertical direction or the response in length-change caused by the length-adjust- able connection means allows the additive manufacturing apparatus to be adjusted to different loads acting on the build cylinder wall, the use of differently dimensioned build cylinders in the same additive manufac-

[0113] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 tuning apparatus or other changes in the setup of the apparatus. Depending on the kind of length-adjustable connection means that is used, such changes can be realized either mechanically or by the use of control means in case an actively controlled system is used.

[0114] 5

[0042] Preferably, the at least one of the length-adjustable connection means is formed by a biasing means. The biasing means is configured for biasing the cylinder wall against the process chamber bottom. The biasing means is preferably formed as a helical-spring, a disc-spring, a magnetic-spring, a cushion-damper, or a pneumatic cylinder. A biasing

[0115] 10 means which is a passively acting length-adjustable connection means preferably responds inherently to the changes in the force acting on the process chamber bottom. The biasing means hold the build cylinder wall in a predetermined position and respond to any changes in that position with a counter force that both reduce the forces exerted on the process chamber bottom when the build cylinder wall is docked to the process chamber bottom as well as when temperature-induced changes in the extension of the build cylinder wall in the vertical direction occur.

[0116]

[0043] In another preferred embodiment, at least one of the length-ad- justable connection means is configured so that the change in extension

[0117] 20 of the length-adjustable connection means can be actively controlled. The at least one of the length-adjustable connection means is preferably formed as a linear drive such as a hydraulic cylinder, a pneumatic cylinder, or a lifting cushion.

[0118]

[0044] Hence, in the preferred embodiment, the length-adjustable con¬

[0119] 25 nection means is not or not only a passively responding device but comprises an active component that allows to control the change of the extension of the length-adjustable connection means using any kind of preferred control means. In this embodiment, the length-adjustable connection means is preferably a linear drive which allows to actively

[0120] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 change the distance of the point where the build cylinder wall is supported on the length-adjustable connection means from the process chamber bottom. Examples of linear drives that can be used are hydronic cylinders, pneumatic cylinders, or lifting cushions. In particular,

[0121] 5 pneumatic cylinders and lifting cushions may have the advantage of allowing both a passive and an active response to changes in the force exerted by the build cylinder wall on the process chamber bottom as they rely on a compressible medium for changing the extension of the connection means in the vertical direction.

[0122]

[0045] For the sake of completeness, it is noted that the previously described embodiments for docking a build cylinder to a process chamber so that the build cylinder is mechanically decoupled from the process chamber can also be used for docking other elements to a process chamber of an additive manufacturing apparatus. For example, a con¬

[0123] 15 tainer with raw material powder could be docked to the process chamber using an embodiment of a force compensation system as previously described.

[0124]

[0046] Subsequently, the invention will be described in more detail with reference to the drawing wherein

[0125] 20 Fig. 1 shows a sectional schematic drawing of part of a first exemplary embodiment of an additive manufacturing apparatus with a build cylinder not positioned in an operating position,

[0126] Fig. 2 shows a sectional schematic drawing of the first exemplary embodiment with the build cylinder in the operating position,

[0127] Fig. 3 shows a sectional schematic drawing of part of a second exemplary embodiment of an additive manufacturing apparatus with the build cylinder not positioned in the operat¬

[0128] 30 ing position,

[0129] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 Fig. 4 shows a sectional schematic drawing of the exemplary embodiment of figure 3 with the build cylinder in the operating position and

[0130] Fig. 5 shows a sectional schematic drawing of a third exemplary

[0131] 5 embodiment of an additive manufacturing apparatus with the build cylinder in the operating position.

[0132]

[0047] Fig. 1 and 2 show a first exemplary embodiment of an additive manufacturing apparatus 1 for manufacturing three-dimensional workpieces using LPBF. The additive manufacturing apparatus comprises a process chamber 3 and a build cylinder 5. The process chamber 5 is only shown partially in the figures. It comprises a process chamber bottom 7 extending generally perpendicular to a vertical axis 9, i.e., parallel to a horizontal plane. The process chamber further comprises side walls 1 l a, 1 1 b which are only shown partially in the figures. The process chamber

[0133] 15 bottom 7 surrounds a central opening 13 defining a build area 15 for manufacturing three-dimensional workpieces. The process chamber 3 further comprises an irradiation unit providing a high-energy laser-beam which is, however, not shown in the figures. Further, the process chamber comprises a recoater 17 which is moveable in a horizontal direction 19 across an upper surface 21 of the process chamber bottom.

[0134]

[0048] The build cylinder 5 comprises a build cylinder wall 23 which extends generally in a vertical direction. In the exemplary embodiment shown in figures 1 and 2, the build cylinder wall 23 extends parallel to the vertical axis 9. The build cylinder wall 23 surrounds a carrier 25 which ex¬

[0135] 25 tends perpendicular to the vertical axis 9, i.e., parallel to the horizontal plane. The carrier 25 is supported by a carrier positioning means 27 which is configures to move the carrier 25 parallel to the vertical axis 9. The carrier is off generally rectangular cross section in the horizontal plane.

[0136] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025

[0049] As an inner surface 29 of the build cylinder wall 23 tightly conforms to the shape of the carrier 25, an inner cross section of the build cylinder wall 23 is also rectangular. The build cylinder wall 23 further comprises sealing means 31 which are located on an upper surface 33 of the build

[0137] 5 cylinder wall 33. The upper surface 33 faces towards a lower surface 35 of the process chamber bottom 7. The sealing means 31 is provided for sealing contact with a corresponding contact surface 37 formed on the lower surface 35 of the process chamber bottom 7.

[0138]

[0050] For manufacturing workpieces with the additive manufacturing apparatus 1 shown in figures 1 and 2, the build cylinder 5 needs to be positioned in an operating position which is shown in figure 2. In figure 1 , the build cylinder 5 is not in the operating position and needs to be moved upwards in the vertical direction until the build cylinder wall 23 and, to be more concretely, the sealing means 31 provided on the upper

[0139] 15 surface 33 of the build cylinder wall 23 are in sealing contact with the contact surface 37 provided on the lower surface 35 of the process chamber bottom 7. For moving the build cylinder 5 in the vertical direction 9, the build cylinder wall 23 can be locked to the carrier 25. In the figures, the corresponding locking means or locking mechanism is not shown. When the build cylinder wall 23 is locked to the carrier, the build cylinder wall 23 can be moved in the vertical direction both upwards und downwards with the carrier 25 using the carrier positioning means 27.

[0140]

[0051] In the exemplary embodiments shown in figures 1 and 2, the additive manufacturing apparatus 1 further comprises a cylinder docking

[0141] 25 station 39. The cylinder docking station 39 comprises a plurality of clamping systems 41 . In total, the exemplary embodiment shown in the figures comprises four clamping systems 41. However, in the sectional view shown in figures 1 and 2, only two clamping systems 41 are shown. The

[0142] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 clamping systems 41 comprise a receptacle 43 forming a socket for receiving a mating pin 45. The pins 45 are attached at an attachment position 47 to the cylinder wall 23.

[0143]

[0052] For docking the build cylinder 5 to the process chamber 3, the

[0144] 5 carrier 25 is locked to the build cylinder wall 23. The combination of the carrier 25 and the build cylinder wall 23 is then moved upwards in the vertical direction 9 until the pins 45 engage corresponding receptacles 43 of the four clamping systems 41 . The clamping systems 41 are configured to lock the pins 45 and with the pins 45 the build cylinder wall 23 in

[0145] 10 the operating position as shown in figure 2.

[0146]

[0053] Once the build cylinder wall 23 has been coupled to the cylinder docking station 39, the carrier 25 is detached from the build cylinder wall 23 and can be moved relative to the build cylinder wall 23 in the vertical direction 9 both upwards and downwards. The position of the cylinder

[0147] 15 docking station 39 and, to be more precise, the clamping systems 41 is chosen so that once the pins 45 have been locked in the receptacles 43, the attachment position 47 of the build cylinder walls 43 is at a well- defined distance from the lower surface 35 of the process chamber bottom 7 during regular operating conditions. This corresponds to a well-

[0148] 20 known and predetermined distance of the upper surface 33 of the build cylinder wall 23 from the contact surface 37 and, therefore, also to a predefined sealing force acting via the sealing means 31 on the contact surface 37.

[0149]

[0054] However, during manufacturing of three-dimensional workpieces

[0150] 25 using the additive manufacturing apparatus 1 , the distance between the attachment position 47 and the lower surface 35 of the process chamber bottom 7 may change forvarious reasons. For example, before the layer-building process commences, the process chamber 3 is heated up. However, with the process chamber 3 also the build cylinder walls 23

[0151] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 heats up which causes a change in the length of the build cylinder wall 23 along the vertical axis 6. As can be readily understood from the figures, any change in the length of the build cylinder wall 23 between the attachment position 47 and the upper surface 33 of the build cylinder

[0152] 5 wall 23 will cause the distance of the upper surface 33 of the build cylinder wall 23 to shrink provided that a further compression of the sealing means 31 is possible. Further, an extension of the length of the build cylinder wall between the attachment position 47 and the upper surface 33 could even result in an upwards deformation of the process chamber bottom 7.

[0153]

[0055] Such a deformation is detrimental for the quality of the manufactured workpieces, as the recoater 17 moves across the upper surface 21 of the process chamber bottom 7 whenever a new layer of raw material powder has to be applied. In case, the process chamber bottom 7 has

[0154] 15 been deformed out of its intended position, the recoater 17 does not apply the new layer of raw material powder in the intended position but rather closer to the source of the high-energy laser-beam than intended. Any deviation from the intended position of the upper layer of the raw material powder from its intended position is likely detrimental for the

[0155] 20 quality of the manufactured workpieces.

[0156]

[0056] A similar problem occurs also during the layer-building process. Due to the continued application of the high-energy laser-beam to the raw material powder, the process chamber 3 and, in particular, the raw material powder continues to heat up. This causes in turn a further extension of the lengths of the build cylinder wall 23 between the attachment position 47 and the upper surface 33 of the build cylinder wall 23. Again, any extension of the length of the build cylinder wall 23 may negatively affect the sealing force acting on the contact surface 37 of the process chamber bottom 7 and could even lead to a deformation of the process

[0157] 30 chamber bottom 7.

[0158] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025

[0057] When the layer-building process has been completed, the process chamber bottom 3 needs to cool down. During this cool-down- phase, the length of the build cylinder wall 23 in the vertical direction 9 is reduced. However, when the gap between the upper surface 33 of the

[0159] 5 build cylinder wall 23 and the contact surface 37 of the process chamber bottom increases, the sealing force acting via the sealing means 31 on the contact surface 37 decreases which may have a detrimental effect on the sealing of the process chamber 3 from the environment surrounding the process chamber 3.

[0160]

[0058] Also, any movement of the carrier 25 relative to the build cylinder wall 23 could also negatively affect the forces exerted by the build cylinderwall 23 on the process chamber bottom 7. In particular, in case the carrier 25 moves upwards after the build cylinder wall 23 has been docked to the cylinder dicking station 39, friction between the carrier 25

[0161] 15 and the inner walls 29 of the build cylinder wall 23 causes forces acting on the build cylinder wall 23 in the upwards vertical direction 9, i.e., towards the process chamber bottom 7. This may cause the build cylinder wall 23 to move upwards in the vertical direction with the already discusses consequences. Likewise, whenever the carrier 25 is moved down¬

[0162] 20 wards in the vertical direction 9, i.e., away from the process chamber bottom 7, the friction causes the build cylinder wall 23 to move away from the process chamber bottom 7 which leads to a reduction in the force inserted by the build cylinder wall 23 on the process chamber bottom 7.

[0163]

[0059] To overcome the above-mentioned issues, the cylinder docking station 39 comprises an automated force compensations system 49 which mechanically decouples the build cylinder 5 from the process chamber bottom 7. In the exemplary embodiment shown in figures 1 and 2, the force compensation system 49 is embodied by four length-adjust-

[0164] 30 able connection means 51 . The force compensation system is thus not a

[0165] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 single entity but rather a system 49 split in multiple parts. Each of the length-adjustable connection means 51 is formed by a helical spring 53 which support the weight of the build cylinder wall 23 and the clamping systems 41 on an outer support structure 55.

[0166] 5

[0060] The force compensation system 49 has multiple purposes. For example, when the build cylinder 5 is docked to the cylinder docking station 39, the pins 45 need to be pushed into the mating receptacles 43. In this instant, excess forces may be generated that could act via the sealing means 31 onto the lower surface 35 of the process chamber bottom

[0167] 10 7. However, since the forces act against the biasing means 57 in form of the helical spring 53 at least part of the forces are absorbed when the spring 53 is extended. Thereby, the force compensation system 49 reduces the forces that act on the process chamber bottom 7 when the build cylinder s is docked to the build cylinder docking station 39.

[0168] 15

[0061] Similarly, when the length of the build cylinder wall 23 between the attachment position 47 and the upper surface 33 of the build cylinder wall 23 changes, the helical springs 43 are compressed due to the additional forces acting on the process chamber bottom 7. The compression thereby limits the change in the sealing force that acts via the sealing

[0169] 20 element 31 on the contact surface 37. Also, when the build cylinder wall shrinks during cool-down of the process chamber 3 when the layer-building process has been completed, the reduced sealing force is compensated as the helical springs 53 expand when the force acting on the lower surface 35 of the process chamber bottom 7 is less.

[0170] 25

[0062] Additionally, the force compensation system 49 also mitigates potential unintended changes in the force acting on the process chamber bottom 7 when the carrier 25 is moved. For example, in case the carrier 25 is moved upwards relative to the build cylinder wall 23, dragging the build cylinder 23 along due to the friction between the carrier 25 and the

[0171] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 inner surface 29 of the build cylinder wall 23, the upward movement is slowed down by the helical springs 54 as they take up at least some of the forces when their length in the vertical direction 9 is extended. Thus, also in this case the helical springs 53 serve to reduce the change of the

[0172] 5 forces as exerted on the process chamber bottom 7. Also, when the carrier 25 moves in the opposite downward vertical direction 9 dragging the build cylinder wall 23 along, the additional compression of the spring takes up at least some of the force acting on the build cylinder wall 23 and therefor limits the distance the build cylinder wall 23 and, to be more precise, the upper surface 33 of the build cylinder wall travels away from the contact surface 37. This limits the change and, in particular, reduction in the sealing force between the build cylinder wall 23 and the process chamber bottom 7.

[0173]

[0063] To prevent excessive forces acting on the process chamber bot¬

[0174] 15 tom 7 during coupling of the build cylinder 5 to the process chamber 3, the maximum length extension of the biasing means 57 is limited. In the exemplary embodiment shown in figures 1 and 2, the limitation is achieved using a bolt 59 with two union nuts 61 which limit the maximum distance the clamping system 41 can travel away in the vertical direction

[0175] 20 9 from the support structure 55. In the opposite direction, the loss of a sealing between the upper surface 33 of the build cylinder wall 23 and the contact surface 37 is prevented by limiting the maximum compression of the helical springs 53. The maximum compression of the helical springs 53 limited by a stopping point that is reached when the clamping systems 41 come to rest on the support structure 55.

[0176]

[0064] For adjusting the compression of the biasing means 57 in response to a change of the force exerted by the build cylinder wall 23 on the process chamber bottom 7, the compression of the springs can be modified by tightening or loosing the union nuts 61 which are supported on

[0177] 30 the bolt 59. When the union nuts 61 are tightened, the precompression

[0178] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 of the spring 53 is increased. Likewise, when the union nuts 61 are loosened, the precompression of the spring 53 is reduced. Loosening and tightening the union nuts 61 also serves to modify the maximum travel distance which the clamping systems 41 and, thereby, the attachment

[0179] 5 position 47 of the build cylinder wall 23 can travel along the vertical axis 9 to compensate the force exerted on the process chamber bottom 7.

[0180]

[0065] Figures 3 and 4 show a second exemplary embodiment of an additive manufacturing apparatus 1 for manufacturing three-dimensional workpieces. The additive manufacturing apparatus 1 is in many aspects

[0181] 10 similar to the additive manufacturing apparatus previously discussed with reference to figures 1 and 2. For the sake of brevity, subsequently we will only discuss those aspects in more detail that differ from the exemplary embodiment shown in figures 1 and 2. In all other aspects, reference is made to the preceding description of the first exemplary embodiment.

[0182]

[0066] The main difference between the first exemplary embodiment and the second exemplary embodiment is that the second exemplary embodiment does not comprise a cylinder docking station and that the build cylinder wall 23 is not repositioned using the carrier positioning

[0183] 20 means 27. Instead, a dedicated cylinder lifting system 63 is provided which can move the build cylinder 5 into the operating position and away from the operating position in the vertical direction 9. In total, the cylinder lifting system 63 comprises four linear actuators 65 for moving the support structure 55 and the build cylinder 5 supported on the support

[0184] 25 structure via in the force compensation system 49 in the vertical direction 9.

[0185]

[0067] Thus, in the second exemplary embodiment, the carrier 25 can always be moved independently of the build cylinder 5 and, in particular, the build cylinder wall 23. The build cylinder wall 23 is connected via the

[0186] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 force compensation system 49 to the support structure 55 of the lifting system 63. The lifting system 63 is only used to move the build cylinder s into the operating position as seen in figure 4. In figure 3, the build cylinder 5 is not in the operating position.

[0187] 5

[0068] In all other aspects, the additive manufacturing apparatus 1 shown in figures 3 and 4 correspond to that of the first exemplary embodiment. In particular, the fore compensation system 49 is made up from functionally similar parts and provides the same functions and advantages. In particular, it also serves to reduce the forces acting on the

[0188] 10 process chamber bottom 7 when the build cylinder 5 is docked to the process chamber 3.

[0189]

[0069] Finally, figure 5 shows a third exemplary embodiment of an additive manufacturing apparatus 1. The third exemplary embodiment is based on the second exemplary embodiment shown in figures 3 and 4. Thus, for the sake of brevity, only the differences between the second exemplary embodiment and the third exemplary embodiment will be discussed in more detail. In all other aspects, reference is made to the preceding description of the first and second exemplary embodiment.

[0190]

[0070] As compared to the first two exemplary embodiments, the third

[0191] 20 exemplary embodiment implements a different force compensation system 49. The helical spring has been replaced by a linear drive 67 in form of a pneumatic cylinder 69. The system 49 further comprises a control unit 71 which is connected to the pneumatic cylinder 69. The control unit 71 allows an active control of the pneumatic cylinder 60.

[0192] 25

[0071] The force compensation system 49 in form of the pneumatic cylinder 69 combines the advantages of the automatic passive response of the biasing means 57 in form of the helical spring 53 used in the first exemplary embodiment with the additional benefits of an active control of

[0193] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 the length of the pneumatic cylinder 69. The compressible medium in the pneumatic cylinder advantageously allows the pneumatic cylinder essentially to work as a pneumatic spring and thus in a similar manner as the helical spring. In other words, the gas medium pneumatic cylinder is

[0194] 5 compressed if forces exerted by the build cylinder walls 23 on the process chamber bottom 7 increase and inflates automatically when the forces on the process chamber bottom 7 are decreased. Thus, the same function and advantages as discussed with regard to the first two exemplary embodiments are also realized using the pneumatic cylinder 69.

[0195]

[0072] Additionally, using the control unit, the pneumatic cylinder further allows an active modification of the configuration of the pneumatic cylinder 69. For example, the distance between the upper surface 33 of the build cylinder wall 23 and the lower surface 35 of the process chamber bottom 7 can be varied to adapt the sealing force. Likewise, by increas¬

[0196] 15 ing the pressure in the pneumatic cylinder 69, the responds of the pneumatic cylinder 69 can be adapted to a change in the forces acting on the process chamber bottom 7. Further, the control unit 71 even allows an active response to changes in the forces acting on the process chamber bottom 7. Thus, contrary to the first two exemplary embodiments, the embodiment shown in figure 5 is not solely restricted to a passive response to changes in the forces exerted to the process chamber bottom 7. Instead, the system is capable of actively moving build cylinder wall 23 in case the forces on the process chamber bottom 7 should change.

[0197]

[0073] For the sake of completeness it is noted that the pneumatic cylin¬

[0198] 25 der 69 could also be replaced with a hydraulic cylinder. However, in that case, a fully active control of the position and response to force changes would need to be implemented.

[0199] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025 List of reference numerals

[0200] 1 additive manufacturing apparatus

[0201] 3 process chamber

[0202] 5 build cylinder

[0203] 5 7 process chamber bottom

[0204] 9 vertical axis, vertical direction

[0205] I l a, 1 1 b sidewalls of the process chamber bottom

[0206] 13 opening

[0207] 15 build area

[0208] 10 17 recounter

[0209] 19 horizontal direction

[0210] 21 upper surface of the process chamber bottom

[0211] 23 build cylinder wall

[0212] 25 carrier

[0213] 15 27 carrier positioning means

[0214] 29 innerwall

[0215] 31 sealing means

[0216] 33 upper surface of the build cylinder wall

[0217] 35 lower surface of the process chamber bottom

[0218] 20 37 contact surface

[0219] 39 cylinder docking station

[0220] 41 clamping system

[0221] 43 receptacle

[0222] 45 pin

[0223] 25 47 attachment position

[0224] 49 force compensation system

[0225] 51 length-adjustable connection means

[0226] 53 helical spring

[0227] 55 support structure

[0228] 30 57 biasing means

[0229] 59 bolt

[0230] 61 union nut

[0231] 63 cylinder lifting system

[0232] 65 actuator

[0233] 35 67 linear drive

[0234] 69 pneumatic cylinder

[0235] 71 control unit

[0236] Patentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025

Claims

Claims1 . An additive manufacturing apparatus ( 1 ) for manufacturing three- dimensional workpieces comprising a process chamber (3) with a process chamber bottom (7) and a build cylinder (5),5 wherein the build cylinder (5) comprises a build cylinder wall (23) surrounding a carrier (25) for receiving raw material powder, wherein the build cylinder wall (23) extends in a vertical direction (9) and wherein the build cylinder wall (23) and the carrier (25) are configured to be movable relative to each other substantially parallel to a vertical axis (9), wherein the build cylinder (5) is positioned along the vertical axis (9) in an operating position where the build cylinder wall (23) is in contact with a corresponding contact surface (37) formed on the process chamber bottom (7), and15 wherein the build cylinder (5) is mechanically decoupled from the process chamber bottom (7) such that a force transmitted from the build cylinder wall (23) to the process chamber bottom (7) during docking of the build cylinder (5) to the process chamber bottom (7) remains below a threshold and / orsuch that changes in the force exerted on the process chamber bottom (7) by the build cylinder wall (23) during the manufacturing of three-dimensional workpieces are reduced.

2. Additive manufacturing apparatus (1 ) according to claim 1 , wherein the contact between the build cylinder wall (23) and the25 corresponding contact surface (37) formed on the process chamber bottom (7) is established using sealing means (31 ) providing a sealing function between the build cylinder wall (23) and the corresponding contact surface (37). atentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 20253. Additive manufacturing apparatus (1 ) according to claim 1 or 2, wherein the additive manufacturing apparatus (1 ) comprises an automated force compensation system (49) for mechanically decoupling the build cylinder (5) from the process chamber bottom5 (7), wherein the automated force compensation system (49) is configured to reduce during manufacturing of three-dimensional workpieces changes in the force exerted by the build cylinder wall (23) on the process chamber bottom (7) and / or to limit during docking of the build cylinder (5) to the process chamber bottom (7) the10 force exerted by the build cylinder wall (23) on the process chamber bottom (7) below the threshold.

4. Additive manufacturing apparatus ( 1 ) according to claims 2 and 3, wherein the force compensation system (49) is configured for limiting the changes in the force acting on the sealing means (31 ) providing the sealing function between the build cylinder wall (23) and the corresponding contact surface (37) during the manufacturing of three-dimensional workpieces.

5. Additive manufacturing apparatus (1 ) according to claim 3 or 4, wherein the force compensation system (49) is configured to com¬20 pensate changes in the forces exerted by the build cylinder wall (23) on the process chamber bottom (7) caused by thermally induced changes of the extension of the build cylinder wall (23) in the vertical direction (9), wherein the thermally induced changes of the extension of the25 build cylinder wall (23) in the vertical direction (9) occur preferably during at least one of a plurality of phases of manufacturing of three-dimensional workpieces, wherein further preferably the additive manufacturing apparatus ( 1 ) may be configured so that the build cylinder wall (23) heats atentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025up in an earlier phase of manufacturing of three-dimensional workpieces and / or the build cylinder wall (23) cools down in a later phase of manufacturing of three-dimensional workpieces.

6. Additive manufacturing apparatus ( 1 ) according to claim 3, 4, or 5,5 wherein the force compensation system (49) is configured to reduce displacement of the build cylinder wall (23) parallel to the vertical axis (9) caused by friction between the carrier (25) and the build cylinder wall (23) during movement of the build cylinder wall (23) and the carrier (25) relative to each other, and thereby config¬10 ured to reduce changes in the forces exerted by the build cylinder wall (23) on the process chamber bottom (7).

7. Additive manufacturing apparatus ( 1 ) according to any of claims 3 to 6, wherein the force compensation system (49) is configured so that the forces exerted by the build cylinder wall (23) on the process chamber bottom (7) can be adjusted.

8. Additive manufacturing apparatus ( 1 ) according to any of claim 3 to 7, wherein the force compensation system (49) is part of or mounted to a lifting system (63), wherein the lifting system (63) is configured to lift the releasably attached build cylinder (5) to the20 operating position and hold the build cylinder (5) in the operating position during the manufacturing of three-dimensional workpieces.

9. Additive manufacturing apparatus ( 1 ) according to any of claim 3 to 7, wherein the force compensation system (49) is part of or mounted to a cylinder docking station (39), wherein the cylinder25 docking station (39) is configured to hold the build cylinder (5) in the operating position during the manufacturing of three-dimensional workpieces. atentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 202510. Additive manufacturing apparatus (1 ) according to claim 9, wherein the additive manufacturing apparatus (1 ) comprises a carrier positioning means (27) for moving the carrier (25) parallel to the vertical axis (9),5 wherein the carrier positioning means (27) is further configured for lifting the build cylinder (5) to the docking station (39) with the carrier (25), docking the build cylinder (5) to the docking station (39), and detaching the build cylinder wall (23) from the carrier positioning means (27) when the build cylinder (5) has been docked10 to the docking station (39).1 1 . Additive manufacturing apparatus (1 ) according to any claims 3 to 10, wherein the force compensation system (49) comprises a plurality of length-adjustable connection means (51 ) supporting the build cylinder wall (23) in the operating position,15 wherein the length adjustable connection means are configured to automatically change their extension in the vertical direction (9) when the forces exerted by the build cylinder wall (23) on the process chamber bottom (7) change to at least partially compensate the change in the forces exerted by the build cylinder wall20 (23) on the process chamber bottom (7).

12. Additive manufacturing apparatus (1 ) according to claim 1 1 , wherein the length-adjustable connection means (51 ) are configured to reduce their extension in the vertical direction (9) when the forces exerted by the build cylinder wall (23) on the process cham¬25 ber bottom (7) increase.

13. Additive manufacturing apparatus (1 ) according to claim 1 1 , wherein the length-adjustable connection means (51 ) are config- atentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025ured to automatically increase their extension in the vertical direction (9) when the forces exerted by the build cylinder wall (23) on the process chamber bottom (7) increases.

14. Additive manufacturing apparatus (1 ) according to claim 1 1 , 12, or5 13, wherein a change in extension of the length-adjustable connection means (51 ) in the vertical direction (9) is limited to prevent the contact between the build cylinder wall (23) and the process chamber bottom (7) from breaking.

15. Additive manufacturing apparatus (1 ) according to any of claims10 1 1 to 14, wherein a maximum and / or minimum extension of the length-adjustable connection means (51 ) in the vertical direction (9) can be adjusted and / or wherein the change of length extension of the length-adjustable connection means (51 ) in the vertical direction (9) per unit force can be adjusted.15 16. Additive manufacturing apparatus (1 ) according to any of claims 1 1 to 15, wherein at least one of the length-adjustable connection means (51 ) is formed by a biasing means (57), wherein the biasing means (57) is configured for biasing the build cylinder wall (23) against the process chamber bottom (7), wherein the biasing20 means (57) is preferably formed as a helical spring (53), a disc spring, a magnetic spring, a cushion damper, or a pneumatic cylinder (69).

17. Additive manufacturing apparatus ( 1 ) according to claims 1 1 to 16, wherein at least one of the length-adjustable connection means25 (51 ) is configured so that the change in extension of the length-ad- justable connection means (51 ) can be actively controlled, wherein the at least one of the length-adjustable connection means (51 ) is atentanwdlte Hemmer Lmdfeld Frese SLMP 3809 WO, 04 / 08 / 2025preferably formed as linear drive such as a hydraulic cylinder, a pneumatic cylinder (69), or a lifting cushion.Patentanwdlte Hemmer Lindfeld Frese SLMP 3809 WO, 04 / 08 / 2025

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