NL2025693B1

NL2025693B1 - Apparatus and method for producing an object by means of additive manufacturing

Info

Publication number: NL2025693B1
Application number: NL2025693A
Authority: NL
Inventors: Herman Else Vaes Mark; Petrus Wilhelmus Van Der Loo Jacobus
Original assignee: Additive Ind Bv
Priority date: 2020-05-27
Filing date: 2020-05-27
Publication date: 2022-01-13

Abstract

The invention provides an apparatus and method for producing an object by means of additive manufacturing, said apparatus comprising a process chamber arranged to be limited for receiving by a bath of powdered material at a lower side thereof, wherein a surface level of said bath of powdered material defines an object working area, wherein a surface of a first virtual cross-section of said process chamber at said surface level is larger than a surface of a second virtual cross-section of said process chamber, wherein said second virtual cross-section is substantially parallel to said first virtual cross-section; a solidifying device arranged for emitting electromagnetic radiation and arranged for solidifying a selective layer-part of said bath of powdered material on said surface level by said electromagnetic radiation; a support for positioning said object in relation to said surface level of said bath of powdered material.

Description

Title: Apparatus and method for producing an object by means of additive manufacturing Description According to a first aspect, the present disclosure relates to an apparatus for producing an object by means of additive manufacturing. According to a second aspect, the present disclosure relates to a method for producing an object by means of additive manufacturing.

3D printing or additive manufacturing refers to any of various processes for manufacturing a three-dimensional object in which material is joined or solidified under computer control to create a three-dimensional object, with material being added together, typically layer by layer.

The present disclosure relates to an apparatus to print a three- dimensional object comprising: - a process chamber arranged to be limited by a bath of powdered material at a lower side thereof; - a solidifying device arranged for emitting electromagnetic radiation and arranged for solidifying a selective layer-part of said bath of powdered material on said surface level by said electromagnetic radiation; - a support for positioning said object in relation to said surface level of said bath of powdered material.

One of the challenges in the manufacturing of three dimensional objects, in particular in additive manufacturing of metal objects, is how to realize relative low manufacturing costs while allowing to realize a relative high product quality.

It is an object to provide an apparatus and a method that allows to realize relative low manufacturing costs while allowing to realize a relative high product quality.

This object is achieved by the apparatus according to the present disclosure, wherein a surface of a first virtual cross-section, i.e. the area of a first virtual cross-section, of said process chamber at said surface level is larger than a surface of a second virtual cross-section of said process chamber, wherein said second virtual cross-section is at least substantially parallel to said first virtual cross- section. By providing a process chamber, wherein the surface of the first virtual cross-section is larger than the surface of the second virtual cross-section, the process chamber of the apparatus according to the present disclosure may have a relative small volume in combination with a relative large surface of the bath of powdered material for allowing manufacturing of a relative large object. A relative small volume of the process chamber is beneficial for reducing the amount of energy needed for realising a required condition in the process chamber.

A process chamber having a surface of a first virtual cross-section of said process chamber at said surface level which is larger than a surface of a second virtual cross-section, which second virtual cross-section is thus located higher in the process chamber than the first virtual cross-section, thus decreases in size with an increasing upward distance from the surface level, and may thus have a trapezium- shaped, inverted funnel-like shaped geometry, such as a truncated pyramid shape, seen in a vertical cross-section through the process chamber. In a higher zone of the process chamber, its volume will thus be smaller compared to the volume in a lower zone such as at the surface level.

The present disclosure relies at least partly on the insight that a relative large amount of energy may be dissipated for realizing a required condition inside the process chamber, such as an inert atmosphere, a predetermined temperature and/or a predetermined pressure, when manufacturing a relative large object. The present disclosure further relies at least partly on the insight that a process chamber, wherein the surface of the first virtual cross-section is larger than the surface of the second virtual cross-section, allows for a relative efficient flushing of the process chamber with gas. A relative efficient flushing of the process chamber is beneficial for removing waste particles originating from the solidification of the bath of powdered material during manufacturing of the object. Preferably, said first virtual cross-section is at least substantially horizontal, preferably horizontal. It is beneficial, if a ratio of said surface of said second virtual cross- section and said surface of said first virtual cross section reduces as a function of a distance between said first virtual cross section and said second virtual cross-section. That means, with an increasing distance of the second virtual cross section from the first virtual cross-section, the surface of the second virtual cross section becomes smaller.

Preferably, said ratio varies linearly as a function of said distance between said first virtual cross section and said second virtual cross-section. A ratio that varies linearly is attractive for realizing a relative small process chamber while allowing a beam of electromagnetic radiation that, during use enters the process chamber from an upper side of the process chamber opposite the surface level of the bath of powdered material, to solidify selective layer-parts of the bath of powdered material along substantially the entire surface level. This is attractive for realizing relative low manufacturing costs while allowing manufacturing of relative large objects.

In an embodiment of the apparatus according to the first aspect of the present disclosure, said apparatus comprises a positioning arrangement that is arranged for adjusting said surface of said first virtual cross-section of said process chamber, preferably while maintaining said surface of said second virtual cross- section of said process chamber substantially constant, or comprises a positioning arrangement that is arranged for adjusting said surface of said second virtual cross- section of said process chamber, preferably while maintaining said surface of said first virtual cross-section of said process chamber substantially constant.

Providing a positioning arrangement that is arranged for adjusting said surface of said first virtual cross-section of said process chamber, preferably while maintaining said surface of said second virtual cross-section of said process chamber substantially constant, is beneficial for reducing the volume of the process chamber in combination with a relative small surface of the bath of powdered material for allowing manufacturing of a relative small object at a relative low cost. This is attractive for providing a relative versatile apparatus that may be used for manufacturing relative large objects as well as relative small objects at relative low cost. Providing a positioning arrangement that is arranged for adjusting said surface of said second virtual cross-section of said process chamber, preferably while maintaining said surface of said first virtual cross-section of said process chamber substantially constant, may be beneficial for removal of the object via the process chamber. Before removal of the object, the second virtual cross-section may be enlarged relative to the first virtual cross-section. Before starting manufacturing of the object, the second virtual cross-section may initially be increased for allowing positioning in a relative practical manner of a build plate on the support, wherein the build plate comprises a build surface that is arranged for receiving the bath of powdered material. After placement of the build plate on the support, the second virtual cross-section may be reduced for realizing the relative small process chamber.

Preferably, said process chamber comprises an upper wall and a side wall, wherein said upper wall bounds said process chamber at an upper side thereof and wherein said side wall bounds said process chamber such that said surface of said first virtual cross-section of said process chamber at said surface level is larger than said surface of said second virtual cross-section of said process chamber.

In this regard, it is beneficial if said process chamber comprises a further side wall. Preferably said further side wall is opposite said side wall. Preferably, said further side wall bounds said process chamber such that said surface of said first virtual cross-section is larger than said surface of said second virtual cross-section.

In this regard, it is beneficial if said further side wall is inclined towards said side wall such that a distance between said side wall and said further side wall reduces as a function of an increasing distance to said first virtual cross section for reducing the surface of said second virtual cross-section as a function of a distance between said first virtual cross-section and said second virtual cross-section. Preferably, both the side wall and the further side wall are inclined towards each other, preferably wherein the side wall and the further side wall are both at least substantially planar, thereby realizing an above-mentioned truncated pyramid shape seen in vertical 5 cross-section.

Preferably, said positioning arrangement is arranged for adjusting an angle enclosed between said side wall and/or said further side wall and said upper wall and/or said surface level by moving said side wall and/or said further side wall relative to said upper wall and/or said surface level.

When the surface of the second virtual cross-section is smaller than the surface of the first virtual cross-section and both the side wall and the further side wall are inclined towards each other, the angle enclosed between the side wall and the upper wall as well as the angle enclosed by the further side wall and the upper wall are both larger than 90 degrees, as perceived from the inside of the process chamber. The angle enclosed between the side wall and the surface level as well the angle enclosed between the further side wall and the surface level are both smaller than 90 degrees, as perceived from the inside of the process chamber.

When further decreasing the surface of the second virtual cross- section while maintaining the surface of the first virtual cross-section substantially constant by moving the side wall, the angle enclosed between the side wall and the upper wall increases while the angle enclosed between the side wall and the surface level decreases, perceiving the angles from the inside of the process chamber.

When further decreasing the surface of the second virtual cross- section while maintaining the surface of the first virtual cross-section substantially constant by moving the further side wall, the angle enclosed between the further side wall and the upper wall increases while the angle enclosed between the further side wall and the surface level decreases, perceiving the angles from the inside of the process chamber.

When the side wall and/or the further side wall are curved, the angles enclosed by the side wall and/or further side wall and the upper wall and/or surface level are defined by the angle enclosed by the tangent of the cross section of the side wall and/or further side wall and the upper wall and/or surface level at the intersection point of the tangent of the cross section of the side wall and/or further side wall with the upper wall and/or surface level.

The remaining two side walls, provided opposite each other and perpendicular to the side wall and to the further side wall, may extend vertically so as to provide for a closed process chamber, the remaining side walls being configured to maintain a closed process chamber also in the embodiment of the apparatus in which said positioning arrangement is arranged for adjusting an angle enclosed between said side wall and/or said further side wall and said upper wall and/or said surface level by moving said side wall and/or said further side wall relative to said upper wall and/or said surface level.

To that end the side wall and/or further side wall may slide along an inner surface, facing the process chamber, of one or both of said remaining to side walls.

In a practical embodiment of the apparatus according to the first aspect of the present disclosure, said side wall and/or said further side wall are removable from said apparatus for removing said object from said process chamber.

Preferably, said apparatus comprises an extraction device, connected for fluid communication to said process chamber, arranged for extracting gas and/or waste particles originating from solidifying of said bath of powdered material from said process chamber.

Providing an extraction device is beneficial for realising a required condition in the process chamber.

It is advantageous, if said apparatus comprises a conditioning device, connected for fluid communication to said process chamber, arranged for introducing a gas into said process chamber.

In this regard, it is beneficial if said conditioning device is further arranged for introducing said gas into said process chamber at a predetermined a temperature and/or a predetermined pressure.

Preferably, said side wall and/or said further side wall are provided with an opening arranged for providing a gas into said process chamber and/or removing a gas from said process chamber.

It is beneficial if said upper wall is arranged for allowing said electromagnetic radiation to enter said process chamber through said upper wall for said solidifying.

In an embodiment of the apparatus according to the first aspect, a distance between said upper wall and said surface level is substantially constant, preferably constant.

Preferably, said apparatus comprises an inflatable organ arranged for, in an inflated condition thereof, realizing that said surface of said first virtual cross- section is larger than said surface of said second virtual cross-section. Preferably, the inflatable organ is provided as a part of the side wall and/or further side wall.

According to the second aspect, the present disclosure relates to a method for producing an object by means of additive manufacturing, wherein said method comprises the steps of: - providing an apparatus according to the first aspect of the present disclosure; - receiving, by said apparatus, said bath of powdered material, wherein said surface level of said bath of powdered material defines said object working area; - solidifying, by said solidifying device, said selective layer-part of said bath of powdered material on said surface level.

Embodiments of the method according to the second aspect correspond to embodiments of the apparatus according to the first aspect of the present disclosure. The advantages of the method according to the second aspect correspond to advantages of the apparatus according to first aspect of the present disclosure presented previously.

Preferably, said second virtual cross-section is substantially parallel to said first virtual cross-section.

Preferably, before starting or after finishing manufacturing of the object, said method further comprises the step of: - moving a side wall of said process chamber such that said surface of said first virtual cross-section is substantially equal to said surface of said second virtual cross-section.

This allows in a relative practical manner positioning of the build plate on the support before starting manufacturing of the object and removing the build plate and the object from the process chamber after manufacturing of the object.

In an embodiment of the method according the second aspect, it is beneficial if said method further comprises the step of: - moving a side wall of said process chamber such that said surface of first virtual cross-section is larger than said surface of said second virtual cross- section.

Embodiments of the method and apparatus according to the present disclosure will next be explained by means of the accompanying schematic figures, wherein: Fig. 1 — shows a vertical cross section of an apparatus for producing an object by means of additive manufacturing; Fig. 2 — shows a vertical cross section of an embodiment of an apparatus according to the first aspect of the present disclosure; Fig. 3 — shows a vertical cross section of a further embodiment of an apparatus according to the first aspect of the present disclosure; Fig. 4 — shows a vertical cross section of a still further embodiment of an apparatus according to the first aspect of the present disclosure;

Fig. 5 — shows a schematic overview of an embodiment of a method according to the second aspect of the present disclosure; Fig. 6 — shows a schematic overview of another embodiment of a method according to the second aspect of the present disclosure; Fig. 7 — shows a schematic overview of a still other embodiment method according to the second aspect of the present disclosure.

Figure 1 shows an overview of an apparatus 1 for producing an object 2 by means of additive manufacturing. The purpose of the description of figure 1 is for explaining the general operating principle of an apparatus for producing an object 2 by means of additive manufacturing. The apparatus 1 is built from several frame parts 11, 12, 13. The apparatus 1 comprises a process chamber 3 for receiving a bath of powdered material 4 which can be solidified. The process chamber 3 is substantially air tight and is bounded at an upper side by an upper wall 33 which is arranged for allowing electromagnetic radiation to enter the process chamber 3 through the upper wall 33. The process chamber 3 is bounded at the four sides by side walls, of which only opposite side wall 31 and side wall 32 are shown. The bath of powdered material 4 is provided from a supply container 23. In a lower frame part 11, a shaft is provided, wherein a support 5 is provided for positioning the object 2 (or even objects), or at least the object(s) to be produced, in relation to the surface level L1 of the bath of powdered material 4. The distance between the upper wall 33 and the surface level L1 is constant. The support 5 is movably provided on the shaft, such that after solidifying a layer of the object to be produced, the support 5 may be lowered, and a further layer-part of the bath of powdered material may be solidified on top of the part of the object 2 already formed.

In a top part 13 of the apparatus 1, a solidifying device 7 is provided for solidifying a selective layer-part of the bath of powdered material 4. In the embodiment shown, the solidifying device 7 is a laser device, which is arranged for producing electromagnetic radiation in the form of laser light, in order to melt the bath of powdered material 4 provided on the support 5, which then, after cooling forms a solidified part of the object 2 to be produced. However, the invention is not limited to the type of solidifying device. As can be seen, the electromagnetic radiation 9 emitted by the laser device 7 is deflected by means of a deflector unit 15, which uses a rotatable optical element 17 to direct the emitted radiation 9 towards the surface L1 of the layer-part of the bath of powdered material 4. Depending on the position of the deflector unit 15, radiation may be emitted, as an example, according to rays 19, 21. Apparatus 1 is provided with an opening 6 arranged for providing or flushing an inert gas such as argon or nitrogen into or through the process chamber 3.

An embodiment of an apparatus 101 according to the present disclosure is shown in Fig. 2. Elements of apparatus 101 that are similar to elements of apparatus 1 are provided with a reference number equal to the reference number of the element in apparatus 1 raised by 100. Apparatus 101 comprises upper wall 133 that bounds the process chamber 3 at an upper side thereof. Frame parts 112 comprise side walls 131 and 132 for bounding the process chamber 103. Side walls 131 and 132 are placed so that the virtual cross-section of first surface L1 of the layer- part of the bath of powdered material is larger than a surface of a second virtual cross- section of the process chamber 103 which second virtual cross-section is located higher in the process chamber than the first virtual cross-section. As an example of such a surface, surface L2 of a second virtual cross-section is indicated by a dashed line at a height of approximately 2/3 of the height of process chamber 103.

The first virtual cross-section L1 and second virtual cross-section L2 are horizontal. The side walls 131 and 132 are in such a position that the ratio of the virtual cross-section of second surface L2 and virtual cross-section of first surface L1 varies linearly as a function of the distance between first virtual cross-section L1 and second virtual cross section L2. By this process chamber 103 is tapered towards the top, or, widens towards the first surface L1, thereby reducing the volume of the process chamber 103 to a minimum in a higher zone of the process chamber while preserving a relative large surface L1 of the bath of powdered material 4 and without blocking the light path of the laser. For example, the second virtual cross-section when located at the height of the upper wall may be about 50% of the first virtual cross-section. Other ratios may be possible as well, such as lower than 95%, for example about 20%, or lower than 85%, or lower than 75%, and while higher than 30% or 40% or 50%, for example. Reducing the volume of the process chamber 103 optimizes, or at least improves, the flushing process during production of object 102 by means of additive manufacturing. Flushing is done by supplying gas into and removing gas from the process chamber 3 via the opening 106 in order to keep the optics of the apparatus 101 clean. By reducing the volume of the process chamber 103 less gas needs to be supplied in order to require an inert atmosphere inside the process chamber 103. Reducing the volume of the process chamber 103 furthermore results in less power consumption and less generated heat.

In order to move the build plate with the produced object 102 above the surface level L1 and from there removing the produced object 102 from the process chamber 103, the side walls 131 and 132 may in an embodiment be removable from the process chamber 103. Furthermore, side walls 131 and 132 may be removable for providing extra space to handle the build plate.

A further embodiment of an apparatus 201 according to the present disclosure is shown in Fig. 3. Elements of apparatus 201 that are similar to elements of apparatus 1, 101 are provided with a reference number equal to the reference number of the element in apparatus 1 raised by 200. Reference numbers for radiation rays 19, 119 and 21, 121 are not shown in Fig. 3. In this figure, the surface of the upper wall 233 is indicated as the surface of the second virtual cross-section L2.

The apparatus 201 comprises a positioning arrangement 241, 242. Alternatively the apparatus 201 may comprise a positioning arrangement 241’, 242’ (shown dashed in figure 3). With the positioning arrangement 241, 242 positioned at the bottom side of the process chamber 203, the side wall 231 and side wall 232 respectively can be pivoted around an axis (perpendicular to the plane of the paper in the view of figure 3) at the position of 241 and 242 respectively for adjusting the surface of the second virtual cross-section L2 while maintaining the surface of the first virtual cross-section L1 substantially constant. With the positioning arrangement 241’, 242’ positioned at the upper side of the process chamber 203, the side wall 231 and side wall 232 respectively can be pivoted around an axis (perpendicular to the plane of the paper in the view of figure 3)at the position of 241’ and 242’ respectively for adjusting the surface of the first virtual cross-section L1 while maintaining the surface of the second virtual cross-section L2 substantially constant. To ensure the process chamber 203 is maintained closed and air tight when side wall 231, 232 is pivoted around the axis at 241, 242 respectively, wall part 235 and wall part 234 at an upper end of the side walls 231, 232, in the upper side of the process chamber 203 are slightly curved. In case of pivoting about axes at 241’ and 242’ respectively, a similar provision may be made at a lower end of the side walls 231 and 232.

Side walls 231 and 232 can be pivoted to the outside in order to move the build plate with the produced object 2 fully above the surface level L1 and to then remove the produced object 202 from the process chamber 203. Side walls 231 and 232 can furthermore be pivoted to the outside in order to provide extra space to handle the build plate itself. By pivoting side walls 231 and 232 to the inside of the process chamber 203, the volume of the process chamber 203 can be reduced even further. This can be beneficial during the forming of relatively small objects, during flushing of the process chamber 203 and/or during extraction of powder from the process chamber 203.

The side wall 231 and/or further side wall 232 are formed as non- structural movable plate-shaped wall parts between the bottom side and upper side of the process chamber. The remaining two side walls, not shown in the figures, perpendicular to side walls 231 and 232 may extend vertically so as to provide for a closed process chamber. Also, side walls 231 and 232 may slide along the inner surface of said further side walls while pivoted as described above.

A yet another embodiment of an apparatus 301 according to the present disclosure is shown in Fig. 4. Elements of apparatus 301 that are similar to elements of apparatus 1, 101, 201 are provided with a reference number equal to the reference number of the element in apparatus 1 raised by 300. Reference numbers for radiation rays 19, 119 and 21, 121 are not shown in Fig. 4.

Apparatus 301 comprises an inflatable organ 351, 352 integrated in frame part 312 and located at a back side of side wall 331, 332. By inflating the inflatable organ 351, 352, side wall 331, 332 is pivoted about the axis at the position of positioning arrangement 341 and 342 with respect to the frame part 312 thereby realizing that the surface of the cross-section of the second virtual cross-section L2 reduces while maintaining the surface of the first virtual cross-section L1 substantially constant.

In this example, the inflatable organ 351, 352 is implemented as a pair of flexible bellows, however hydraulic or pneumatic cylinders or electro- mechanical spindles other known arrangements can also be used for either pivoting the side wall 331, 332 around axis 341, 342 or for translating the side wall 331, 332 (perpendicular to the plane of the paper in the view of figure 4). Fig. 5 shows an overview of a method 401 for producing an object 102, 202, 302 by means of additive manufacturing.

Method 401 comprises a step of providing an apparatus 101, 201, 301 for producing an object by means of additive manufacturing.

A subsequent step 405 of method 401 is receiving, in the process chamber 103, 203, 303, a bath of powdered material 104, 204, 304, wherein a surface level L1 of the bath of powdered material 104, 204, 304 defines an object working area.

During a subsequent solidifying step 407 of method 401 a selective layer-part of said bath of powdered material 104, 204, 304 is solidified on said surface level L1 by the solidifying device 107, 207, 307. Fig. 6 shows an overview of a method 501 for producing an object 102, 202, 302 by means of additive manufacturing.

Method 501 differs mainly from method 401 in that method 501 comprises a subsequent step 509 of moving the side wall 131, 231, 331, 132, 232, 332 of said process chamber 103, 203, 303 such that the surface of the first virtual cross-section L1 is substantially equal to the surface of the second virtual cross-section L2. With the surface of the first virtual cross-section L1 substantially equal to the surface of the second virtual cross-section L2, the build plate with the produced object 102, 202, 302 can be moved above the surface level L1 and from there the produced object 102, 202, 302 can be removed from the process chamber 103, 203, 303. Fig. 7 shows an overview of a method 801 for producing an object 102, 202, 302 by means of additive manufacturing.

Method 601 differs mainly from method 401 in that method 601 comprises a subsequent step 609 of moving the side wall 131, 231, 331 and/or further side wall 132, 232, 332 of said process chamber 103, 203, 303 such that the surface of the first virtual cross-section L1 is larger than the surface of the second virtual cross-section L2. With the surface of the first virtual cross- section L1 larger than the surface of the second virtual cross-section L2, the volume of the process chamber 103, 203, 303 can be minimized.

During production of the object 102, 202, 203, the side wall 131, 231, 331 and/or further side wall 132, 232, 332 can be set to fixed positions.

However, as the object 102, 202, 302 is produced layer-by-layer, the side wall 131, 231, 331 and/or further side wall 132, 232, 332 can furthermore be adapted dynamically to the dimensions of the object 102, 202, 302 during the production process.

Claims

CONCLUSIONS

Apparatus (101, 201, 301) for producing an object (102, 202, 302) by means of additive manufacturing, the apparatus (101, 201, 301) comprising: - a process chamber (103, 203, 303 ) arranged to be bounded by a bath of powder material (104, 204, 304) on a lower side thereof, wherein a surface level of the bath of powder material (104, 204, 304) defines an object working area, wherein an area of a first virtual cross-section (L1 ) of the process chamber (103, 203, 303) at the surface level is greater than an area of a second virtual cross-section (L2) of the process chamber (103, 203, 303), the second virtual cross-section (L2) being substantially parallel at the first virtual cross-section (L1); - a solidifying device (107, 207, 307) arranged to emit electromagnetic radiation (109, 209, 309) and arranged to solidify a selective layer portion of the bath of powder material (104, 204, 304) at the surface level through the electromagnetic radiation (109, 209, 309); - a support (105, 205, 305) for positioning the object (102, 202, 302) relative to the surface level of the bath of powder material (104, 204, 304).

Apparatus (101, 201, 301) according to claim 1, wherein the first virtual cross-section (L1) is at least substantially horizontal, preferably horizontal.

An apparatus (101, 201, 301) according to claim 1 or 2, wherein a ratio between the area of the second virtual cross-section (L2} and the area of the first virtual cross-section (L1) decreases as a function of a distance between the first virtual cross-section (L1) and the second virtual cross-section (L2), preferably wherein the ratio varies linearly as a function of the distance between the first virtual cross-section (L1) and the second virtual cross-section (L2).

An apparatus (201, 301) according to any one of the preceding claims, the apparatus (201, 301) comprising:

- a positioning device (241°, 242') adapted to adjust the area of the first virtual cross-section (L1) of the process chamber, preferably while keeping the area of the second virtual cross-section (L2) of the process chamber substantially constant and/or - a positioning device (241, 242, 341, 342) adapted to adjust the area of the second virtual cross-section (L2) of the process chamber, preferably while maintaining the area of the first virtual cross-section ( L1) of the process chamber is kept substantially constant.

Apparatus (101, 201, 301) according to any preceding claim, wherein the process chamber (103, 203, 303) comprises a top wall (133, 233, 333) and a side wall (131, 231, 331), the top wall (133, 233, 333) defines the process chamber (103, 203, 303) at a top thereof and wherein the side wall (131, 231, 331) defines the process chamber (103, 203, 303) such that the area of the first virtual cross-section (L1) of the process chamber (103, 203, 303) at the surface level is greater than the area of the second virtual cross-section (L2) of the process chamber (103, 203, 303).

The apparatus (101, 201, 301) of claim 5, wherein the process chamber comprises a further side wall (132, 232, 332), the further side wall inclined toward the side wall (131, 231, 331) such that a distance between the side wall (131, 231, 331) and the further side wall (132, 232, 332) decrease as a function of increasing distance from the first virtual cross-section (L1) and for decreasing the area of the second virtual cross-section (L2) as a function of the distance between the first virtual cross-section (L1) and the second virtual cross-section (L2).

Apparatus (201, 301) according to claim 4 and according to claim 5 and/or 6, wherein the positioning device (241, 341, 242, 342) is adapted to adjust an angle enclosed between the side wall (131, 231 , 331) and/or the further side wall (132, 232, 332) and the top wall (133, 233, 333) and/or the surface level by moving the side wall (131, 231, 331) and/or the further side wall (132, 232, 332) with respect to the top wall (133, 233, 333) and/or the surface level.

Apparatus (101, 201, 301) according to claim 5 and/or 6 or any claim dependent thereon, wherein the side wall (131, 231, 331) and/or the further side wall (132, 232, 332) are removable from the process chamber (103, 203, 303) for removing the object from the process chamber (103, 203, 303).

Apparatus (101, 201, 301) according to claim 5 and/or 6 or any claim dependent thereon, wherein the side wall (131, 231, 331) and/or the further side wall (132, 232, 332) are provided with a opening {106, 206, 306) arranged to introduce a gas into the process chamber (103, 203, 303) and/or remove a gas from the process chamber (103, 203, 303).

An apparatus (101, 201, 301) according to claim 5 or a claim dependent thereon, wherein the top wall is adapted to admit the electromagnetic radiation into the process chamber through the top wall for solidification.

Apparatus (101, 201, 301) according to claim 5 or a claim dependent thereon, wherein a distance between the top wall (133, 233, 333) and the surface level is substantially constant, preferably constant.

An apparatus (301) according to any one of the preceding claims, wherein the apparatus (301) comprises an inflatable member (351, 352) adapted to realize when inflated that the area of the first virtual cross-section (L1) is greater than the area of the second virtual cross-section (L2).

A method (401, 501, 601) for producing an object (102, 202, 302) by means of additive manufacturing, the method (401, 501, 601) comprising the steps of: - providing (403, 503, 603) of an apparatus (101, 201, 301) for producing an object (102, 202, 302) by means of additive manufacturing according to any preceding claim; - receiving (405, 505, 605), by the apparatus (101, 201, 301), the bath of powder material (104, 204, 304), the surface level of the bath of powder material (104, 204, 304) being a working area of the object defines;

- solidifying (407, 507, 607), by the solidifying device (107, 207, 307), the selective layer portion of the material (104, 204, 304) at the surface level.

A method (501) according to claim 13 using an apparatus (101, 201, 301) according to claim 5 or a claim dependent thereon, wherein the method (501) further comprises the step of: - moving (509) the side wall (131, 231, 331) of the process chamber (103, 203, 303) such that the area of the first virtual cross-section (L1) is substantially equal to the area of the second virtual cross-section (L2).

A method (601) according to claim 13 using an apparatus (101, 201, 301) according to claim 5 or a claim dependent thereon, wherein the method (601) further comprises the step of: - moving (609) the side wall (131, 231, 331, 132, 232, 332) of the process chamber (103, 203, 303) such that the area of the first virtual cross-section {L1) is larger than the area of the second virtual cross-section (L2).