Device and method for treating workpieces by means of a vacuum

Abstract

The invention relates to a device (1) for treating workpieces, comprising: a process chamber (PK1, PK2, PK3) into which a workpiece to be treated can be introduced and which can be or is at least partially filled with a treatment liquid (BF); and a vacuum pump (VP) which can be brought into fluidic connection with the process chamber in order to evacuate the process chamber (PK1, PK2, PK3). A branching region (VB) is arranged in the fluidic connection between the vacuum pump (VP) and the process chamber (PK1, PK2, PK3), into which branching region a first channel section (K1), a second channel section (K2) and a third channel section (K3) open. The first channel section (K1) is in fluidic connection with the process chamber (PK1, PK2, PK3) and has a channel constriction (KE1). The second channel section (K2) can be brought into fluidic connection with the vacuum pump (VP). The third channel section (K3) can be brought into fluidic connection with a purge gas source (AT). In the branching region (VB), a basin-like sink (BS) is provided between the channel constriction (KE1) and the second channel section (K2), the fluid outlet of which sink is formed by the channel constriction (KE1) or for which sink the channel constriction (KE1) forms a fluid outlet.

Description

[0001] Device and method for treating workpieces using a vacuum

[0002] The invention relates to a device and a method for treating workpieces using a vacuum, in particular for cleaning or passivating the surfaces of workpieces with delicate or porous structures, including capillary structures, as well as for removing loose particles during the post-treatment of additively manufactured workpieces or removing fine burrs from workpieces of any type. Treating workpieces is particularly challenging when the workpieces have blind holes, especially capillary blind holes.

[0003] Known devices for treating workpieces include a process chamber (PK1, PK2, PK3) into which a workpiece to be treated can be placed and which can be at least partially filled or is filled with a treatment fluid (BF), as well as a vacuum pump (VP) which can be brought into fluid contact with the process chamber (PK1, PK2, PK3) for evacuating the process chamber.

[0004] Known methods for treating workpieces use an interplay of pressure drops and pressure increases of the treatment fluid in the process chamber. One such method is described in WO2022 / 106886A1.

[0005] When treating the workpiece with treatment fluid and vacuum, the aim is to bring the treatment fluid to the entire surface of the workpiece and to expose the entire surface of the workpiece to pressure fluctuations (alternating build-up and release of the vacuum).

[0006] When evacuating a process chamber containing the workpiece surrounded by treatment fluid, foam, droplets, or splashes of treatment fluid can form during the evacuation of the free volume within the chamber. These droplets or splashes could enter the fluid connection between the vacuum pump and the process chamber. If treatment fluid enters this connection, the vapor pressure of the treatment fluid makes evacuation more difficult, thus slowing down and impairing the process.

[0007] The invention is based on the objective of providing a device and a method for treating workpieces using a vacuum, which reduces or completely eliminates the described impairment of the method.

[0008] The invention provides a device and a method for treating workpieces using a vacuum according to claim 1 and claim 20, respectively. Advantageous embodiments are described in the dependent claims.

[0009] According to a first aspect, the invention provides a device for treating workpieces, wherein the device comprises:

[0010] - a process chamber (PK1, PK2, PK3) into which a workpiece (W) to be treated can be placed and which can be at least partially filled or is filled with a treatment fluid (BF); and

[0011] - a vacuum pump (VP) used to evacuate the process chamber

[0012] (PK1 ,PK2,PK3) can be brought into fluid communication with the process chamber, characterized in that a branching area (VB) is arranged in the fluid connection between the vacuum pump (VP) and the process chamber (PK1 ,PK2,PK3), into which a first channel section (K1 ), a second channel section (K2) and a third channel section (K3) open; wherein

[0013] - the first channel section (K1 ) is in fluid connection with the process chamber (PK1 ,PK2,PK3) or can be brought into fluid connection and has a first channel constriction (KE1 );

[0014] - the second channel section (K2) can be brought into fluid contact with the vacuum pump (VP); and

[0015] - the third channel section (K3) can be brought into fluid contact with a purge gas source (AT). According to the invention, a basin-like depression (BS) is provided in the branching area (VB) between the channel constriction (KE1) and the second channel section (K2), the fluid outlet of which is formed by the channel constriction (KE1) or for which the channel constriction (KE1) forms a fluid outlet.

[0016] Thus, treatment fluid BF can accumulate in the basin-like depression BS of the first channel constriction KE1, which can pass through the first channel constriction KE1 into the branching area VB when the process chamber PK1, PK2, PK3 is evacuated (as described on page 1, last paragraph and page 2, first paragraph).

[0017] Preferably, a vacuum pump valve (VV2) is arranged in the second channel section (K2), with which the fluid connection between the branching area (VB) and the vacuum pump (VP) can be established or interrupted.

[0018] Thus, the vacuum pump valve can be opened to begin a step of evacuating the process chamber and closed to end that step. During evacuation, in addition to air, vapor from the treatment fluid and treatment fluid not captured by the channel constriction, particularly water vapor or liquid water, can pass through the channel constriction. This can occur due to bursting vapor bubbles, resulting in liquid splashes and / or liquid foam. Due to the effect of gravity, a large portion of the transported treatment fluid can collect in the basin-like depression to avoid reaching the vacuum pump.

[0019] Preferably, an atmospheric valve (AV) is arranged in the third channel section, with which the fluid connection between the branching area (VB) and the purge gas source (AT) can be established or interrupted.

[0020] The vacuum pump valve can then be closed to complete the evacuation of the process chamber. The atmospheric valve can now be opened ("breaking the vacuum") to begin a step of rinsing, or returning, or blowing back the treatment fluid collected in the basin-like sink into the process chamber using a purge gas, e.g., atmospheric air and / or inert gas. It can then be closed to complete the rinsing step, i.e., returning the treatment fluid to the process chamber(s).

[0021] Preferably, the channel constriction (KE1) on the side of the branching region (VB) has a widening region (AB) which widens from a region with a minimum flow cross-section to a region with a maximum flow cross-section. This widening can be funnel-shaped.

[0022] Preferably, the widening area (AB) forms part of the basin-like depression (BS) or forms a transition from the area with minimal flow cross-section to the basin-like depression (BS).

[0023] This allows for the most complete possible rinsing, recirculation, or blowing of the treatment fluid accumulated in the basin-like depression by means of rinsing gas (atmospheric air and / or inert gas) penetrating the branching area, if necessary even against gravity and towards the area with minimal flow cross-section (fluid outlet).

[0024] Preferably, the widening area (AB) has a funnel-shaped form or is designed in a funnel shape.

[0025] The inner surface of the widening area (AB) can have a) a conical or b) a concave or c) a convex shape.

[0026] The expansion area can have a rotationally symmetrical inner surface formed by a generating element rotating about an axis (geometry axis of the expansion area AB or generating axis of rotation) that is a) rectilinear, b) concave, or c) convex, resulting in a) conical, b) tulip, or c) chanterelle shape. The expansion area can also have a shape that deviates from rotational symmetry.

[0027] Preferably the first channel constriction (KE1 ) is arranged at a funnel outlet area or at the tapered end of the funnel-shaped form, wherein the funnel-shaped form opens into the first channel section (K1 ) with its tapered end.

[0028] Preferably a first vacuum valve (VV1) is arranged at the funnel outlet area or at the tapered end of the funnel-shaped form.

[0029] Preferably, a second channel constriction KE2 is arranged at a funnel inlet area or at a flared end of the funnel-shaped form, wherein the funnel-shaped form opens into the second channel section (K2) at its flared end.

[0030] Preferably a second vacuum valve (VV2) is arranged at the funnel inlet area or at the widened end of the funnel-shaped form.

[0031] Preferably an atmosphere valve (AV) is arranged at a funnel inlet area or at a flared end of the funnel-shaped form, wherein the funnel-shaped form opens into the third channel section (K3) at its flared end.

[0032] Preferably, the third channel section (K3) opens into the funnel-shaped chamber of the branching region (VB) along a channel opening direction of the channel section (K3), which is offset with respect to the round or rounded inner shape of the funnel-shaped chamber, in particular with respect to the rotational symmetry axis of the funnel-shaped chamber, and has a tangential component as well as a radial component with respect to the round or rounded inner shape.

[0033] Preferably, the tangential component of the channel outlet direction is greater than the radial component, with the radial component being particularly zero. Preferably, the channel outlet direction of the channel section (K3) is inclined downwards with respect to the funnel-shaped chamber towards the funnel outlet or towards the tapered end of the funnel, or has an axial component with respect to the rounded inner shape, which is directed towards the first channel section (K1).

[0034] When the branching section VB is flushed with air or an inert gas, less turbulence is generated, thus preventing splashing and / or foaming of the treatment fluid BF when emptying the connection section VB. The flushing gas flowing from the flushing gas source AT into the funnel-shaped chamber through the third channel section K3 expands and flows along the inner walls of the funnel-shaped chamber to blow the droplets of condensed treatment fluid adhering to the inner walls towards the funnel outlet or the tapered end of the funnel-shaped chamber.

[0035] Preferably, the second channel section (K2), which can be brought into fluid contact with the vacuum pump (VP), has a further or second channel constriction (KE2).

[0036] The second channel constriction, similar to the first, can capture a further portion of the treatment fluid carried during evacuation, which then flows, due to gravity, into a second basin-like depression associated with this second channel constriction. Through the action of gravity, a portion of the treatment fluid transported during evacuation that does not evaporate can collect in this second basin-like depression, preventing it from reaching the vacuum pump.

[0037] Preferably, a further or second vacuum pump valve (VV2) is arranged in the second channel section (K2) between the branching area (VB) and the further or second channel constriction (KE2). Preferably, a further or third vacuum pump valve (VV3) is arranged in the second channel section (K2) between the further or second channel constriction (KE2) and the vacuum pump (VP).

[0038] Preferably, at least a part of the inner wall of the branching area (VB) is thermally connected to a coolant.

[0039] Even more treatment fluid can condense on the coolable part of the inner wall.

[0040] According to a second aspect, the invention provides a method for treating workpieces using a device according to one of the preceding paragraphs, wherein the method comprises: a) introducing a workpiece (W) into a process chamber (PK1, PK2, PK3); b) establishing a fluid connection between the branching region (VB) and the vacuum pump (VP) or between the process chamber (PK1, PK2, PK3) and the vacuum pump (VP); c) interrupting the fluid connection between the branching region (VB) or the process chamber (PK1, PK2, PK3) and the vacuum pump (VP); d) establishing a fluid connection between the branching region (VB) and a purge gas source (AT); e) interrupting the fluid connection between the branching region (VB) and the purge gas source (AT).

[0041] Preferably, the sequence of steps b), c), d) and e) is repeated several times.

[0042] The purge gas source (AT) can consist of air, especially atmospheric air. Purging the connection area (VB) with atmospheric air is cost-effective.

[0043] The purge gas source (AT) can comprise an inert gas, in particular nitrogen or argon, preferably pure nitrogen or a nitrogen / argon mixture, preferably with less than 1 vol% oxygen. Thus, the purge of the connection area (VB) can be carried out with such an inert gas.

[0044] Preferably, a first purge gas source contains air and a second purge gas source contains an inert gas, in particular nitrogen or argon.

[0045] Therefore, the connection area (VB) can be flushed with air or with inert gas.

[0046] Preferably, when performing steps d) and e), the first purge gas source is used first, and when performing steps d) and e) last, the second purge gas source is used.

[0047] Thus, the bonding area (VB) is initially purged with air, whereby the oxygen contained therein is tolerated. In contrast, the bonding area (VB) is purged with inert gas at the end, i.e., before the workpiece dries, whereby oxygen is either not tolerated or only tolerated in very small quantities.

[0048] Preferably, the method according to steps b), c), d) and e) includes as a further step f) drying the workpiece (W).

[0049] Preferably, step f) is carried out in an inert gas environment.

[0050] This prevents oxidation of the workpiece surface.

[0051] Preferably, the device according to the invention includes at least one ultrasound source by means of which a workpiece contained in a process chamber and a treatment fluid surrounding it can be exposed to ultrasound.

[0052] Preferably, the inventive method comprises at least one step in which a workpiece contained in a process chamber and a treatment fluid surrounding it are exposed to ultrasound. Further advantages, features, and application possibilities of the invention will become apparent from the following description of exemplary embodiments of the inventive device, which are not to be considered limiting, with reference to the drawing, wherein:

[0053] Fig. 1 is a schematic view of a first embodiment of the device according to the invention;

[0054] Fig. 2 (with VV2 and without VV3) is a schematic view of a second embodiment of the device according to the invention;

[0055] Fig. 2 (without VV2 and with VV3) is a schematic view of a third embodiment of the device according to the invention;

[0056] Fig. 3 is a schematic sectional view of an exemplary embodiment of a channel constriction of the device according to the invention;

[0057] Fig. 4 is a schematic sectional view of a further exemplary embodiment of a channel constriction of the device according to the invention; and

[0058] Fig. 5 shows a particularly preferred embodiment of the device according to the invention.

[0059] Fig. 1 is a schematic view of a first embodiment of the device according to the invention.

[0060] The first version has only one initial channel narrowing KE1.

[0061] The second vacuum valve VV2 is located here in a second channel section K2 between the branching area VB and the vacuum pump VP, or between the channel constriction KE1 and the vacuum pump VP. The vacuum pump VP is in fluid communication with a vacuum tank (not shown).

[0062] The first vacuum valve VV1 shown in channel section K1 is optional and can therefore be omitted. Fig. 2 (with VV2 and without VV3) is a schematic view of a second embodiment of the device according to the invention.

[0063] The second version has a first channel constriction KE1 in a first container B1 and a second channel constriction KE2 in a second container B2.

[0064] The second vacuum valve VV2 is located here in the second channel section K2 between the branching area VB and the second channel constriction KE2, or between the first channel constriction KE1 and the second channel constriction KE2. The vacuum pump VP is in fluid communication with a vacuum tank (not shown).

[0065] The third vacuum valve VV3 shown in channel section K2 is optional and can therefore be omitted.

[0066] Fig. 2 (without VV2 and with VV3) is a schematic view of a third embodiment of the device according to the invention.

[0067] The third version also has a first channel narrowing KE1 and a second channel narrowing KE2.

[0068] The third vacuum valve VV3 is located here in the second channel section K2 between the second channel constriction KE2 and the vacuum pump VP.

[0069] The second vacuum valve VV2 shown in the second channel section K2 is optional and can therefore be omitted. In this case, the first container B1 and the second container B2 form a common container (see Fig. 4) in which the first channel constriction KE1 and the second channel constriction KE2 are arranged side by side. The vacuum pump VP is in fluid communication with a vacuum tank (not shown).

[0070] Fig. 3 shows a schematic sectional view of an exemplary embodiment of the first channel constriction KE1 along a channel axis according to the invention.

[0071] One can see an area of ​​widening AB as well as a pelvic-like depression BS, in which accumulated treatment fluid BF is shown.

[0072] The first channel constriction KE1 serves as an overflow for treatment fluid BF in the basin-like depression BS. Fig. 4 shows a schematic sectional view of a further exemplary embodiment of a channel constriction or first channel constriction KE1 along a channel axis according to the invention.

[0073] The widening area AB and the pelvic depression BS, in which accumulated treatment fluid BF is shown, can again be seen.

[0074] The first channel constriction KE1 serves as an overflow for the basin-like depression BS. A further channel constriction, or second channel constriction KE2, is arranged offset from the first channel constriction KE1 along the channel axis.

[0075] The second channel constriction KE2 also serves as an overflow for treatment fluid BF to the basin-like depression BS.

[0076] Fig. 5 shows a particularly preferred embodiment of the branching area VB. The first channel section K1, the second channel section K2, and the third channel section K3, all of which flow into the branching area VB, can be seen.

[0077] The branching region VB is a funnel-shaped chamber with a conical outer surface, as shown in Fig. 5. The branching region VB is shown in a state partially filled with treatment fluid BF.

[0078] According to a first alternative, the funnel-shaped chamber can have a concave outer surface, which roughly corresponds to a tulip-like chamber shape. According to a second alternative, the funnel-shaped chamber can have a convex outer surface, which roughly corresponds to a chanterelle-like chamber shape. Regardless of the aforementioned chamber shapes (conical, concave, convex), the round or rounded inner shape, and especially the rotational symmetry, of the funnel-shaped chamber is particularly advantageous.

[0079] The first channel section K1 is in fluid communication with, or can be brought into fluid communication with, the process chambers PK1, PK2, and PK3, for which the first vacuum valve VV1 is provided. This fluid connection has a first channel constriction KE1. The first vacuum valve VV1 is a spool valve with a spool SVV1. This first vacuum valve VV1, or spool valve with spool SVV1, can also be omitted from the fluid connection. The second channel section K2 is in fluid communication with, or can be brought into fluid communication with, the vacuum pump VP, for which the second vacuum valve VV2 is provided. This fluid connection has a second channel constriction KE2. The second vacuum valve VV2 is also a spool valve (spool not shown).

[0080] The third channel section K3 is in fluid contact with the atmosphere AT or with a purge gas source (not shown), or can be brought into fluid contact with it, for which purpose the atmosphere valve AV is provided. The atmosphere valve AV is a diaphragm valve with a diaphragm MAV. An inert gas or an inert gas mixture, in particular argon or nitrogen, can be used as the purge gas.

[0081] The third channel section K3, which is intended for purging the branching region VB with air or an inert gas, opens into the funnel-shaped chamber of the branching region VB along a channel outlet direction of the third channel section K3, which is offset with respect to the round or rounded inner shape of the funnel-shaped chamber, in particular with respect to the rotational symmetry axis of the funnel-shaped chamber and has a tangential component as well as a radial component with respect to the rounded inner shape.

[0082] It is particularly advantageous if, in the direction of the channel mouth, the tangential component is larger than the radial component, or if the radial component is even zero.

[0083] Furthermore, it is advantageous if the channel outlet direction of the third channel section K3 is inclined with respect to the funnel-shaped chamber towards the funnel outlet or towards the tapered end of the funnel, in particular downwards, or has an axial component with respect to the rounded inner shape that is directed towards the funnel outlet or towards the tapered end of the funnel.

[0084] All of this contributes to minimal turbulence when purging the branching section VB or the expansion section AB with air or an inert gas, thus preventing splashing and / or foaming of the treatment fluid BF when emptying the connection section VB. Any vapors, especially water vapor, in the branching section VB are cooled during expansion, resulting in at least partial condensation on the inner wall of the branching section VB. The resulting condensate, especially water, is returned to the process chambers PK1, PK2, and PK3 when the atmosphere valve AV is opened. This ensures that only a small amount of liquid enters the vacuum tank (not shown).

[0085] Reference symbol list

[0086] 1 Device

[0087] PK1 first trial chamber

[0088] PK2 second trial chamber

[0089] PK3 third trial chamber

[0090] W workpiece

[0091] BF treatment fluid

[0092] VP vacuum pump

[0093] VB branching area

[0094] K1 first canal section

[0095] K2 second canal section

[0096] K3 third canal section

[0097] VV1 first vacuum valve (in version 1 according to Figure 1)

[0098] VV2 second vacuum valve (in version 2 according to figure 2)

[0099] VV3 third vacuum valve (in version 3 according to Figure 2)

[0100] KE1 first channel narrowing

[0101] KE2 second channel narrowing

[0102] B1 first container

[0103] B2 second container

[0104] AT Purge gas source (atmosphere and / or inert gas source)

[0105] AV atmospheric valve

[0106] AB expansion area

[0107] BS pelvic depression

[0108] SVV1 slider of VV1

[0109] MAV Membrane from AV

Claims

Claims 1. Device (1) for treating workpieces, wherein the device comprises: - a process chamber (PK1, PK2, PK3) into which a workpiece (W) to be treated can be placed and which can be at least partially filled or is filled with a treatment fluid (BF); and - a vacuum pump (VP) used to evacuate the process chamber (PK1 ,PK2,PK3) can be brought into fluid communication with the process chamber, characterized in that a branching area (VB) is arranged in the fluid connection between the vacuum pump (VP) and the process chamber (PK1 ,PK2,PK3), into which a first channel section (K1 ), a second channel section (K2) and a third channel section (K3) open; wherein - the first channel section (K1 ) is in fluid connection with the process chamber (PK1 ,PK2,PK3) or can be brought into fluid connection and has a first channel constriction (KE1 ); - the second channel section (K2) can be brought into fluid contact with the vacuum pump (VP); and - the third channel section (K3) can be brought into fluid contact with a purge gas source (AT); wherein a basin-like depression (BS) is provided in the branching area (VB) between the channel constriction (KE1) and the second channel section (K2), the fluid outlet of which is formed by the channel constriction (KE1) or for which the channel constriction (KE1) forms a fluid outlet.

2. Device according to claim 1, characterized in that a vacuum pump valve (VV2) is arranged in the second channel section (K2), with which the fluid connection between the branching area (VB) and the vacuum pump (VP) can be established or interrupted.

3. Device according to claim 1 or 2, characterized in that an atmospheric valve (AV) is arranged in the third channel section, with which the fluid connection between the branching area (VB) and the purge gas source (AT) can be established or interrupted.

4. Device according to one of claims 1 to 3, characterized in that the channel constriction (KE1 ) on the side of the branching area (VB) has a widening area (AB) which widens from an area with a minimum flow cross-section to an area with a maximum flow cross-section (e.g. funnel-shaped).

5. Device according to claim 4, characterized in that the widening area (AB) forms a part of the basin-like depression (BS) or forms a transition from the area with minimal flow cross-section to the basin-like depression (BS).

6. Device according to claim 5, characterized in that the expansion area (AB) has a funnel-shaped form or is designed in a funnel-like manner.

7. Device according to claim 6, characterized in that the inner surface of the expansion area (AB) has a) conically or b) concavely or c) convexly shaped area.

8. Device according to claim 6 or 7, characterized in that the first channel constriction KE1 is arranged at a funnel outlet area or at the tapered end of the funnel-shaped form, wherein the funnel-shaped form opens into the first channel section (K1) with its tapered end.

9. Device according to claim 8, characterized in that a first vacuum valve (VV1 ) is arranged at the funnel outlet area or at the tapered end of the funnel-shaped form.

10. Device according to one of claims 6 to 9, characterized in that a second channel constriction KE2 is arranged at a funnel inlet area or at a flared end of the funnel-shaped form, wherein the funnel-shaped form opens into the second channel section (K2) at its flared end. 1 1 . Device according to claim 10, characterized in that a second vacuum valve (VV2) is arranged at the funnel inlet area or at the flared end of the funnel-shaped form.

12. Device according to one of claims 6 to 1 1 , characterized in that an atmosphere valve (AV) is arranged at a funnel inlet area or at a flared end of the funnel-shaped form, wherein the funnel-shaped form opens into the third channel section (K3) at its flared end.

13. Device according to claim 12, characterized in that the third channel section (K3) opens into the funnel-shaped chamber of the branching region VB along a channel outlet direction of the channel section (K3), which is offset with respect to the round or rounded inner shape of the funnel-shaped chamber, in particular with respect to the rotational symmetry axis of the funnel-shaped chamber and has a tangential component as well as a radial component with respect to the round or rounded inner shape.

14. Device according to claim 13, characterized in that, in the channel outlet direction, the tangential component is greater than the radial component, wherein the radial component is in particular zero.

15. Device according to claim 12 or 13, characterized in that the channel outlet direction of the channel section (K3) is inclined downwards with respect to the funnel-shaped chamber towards the funnel outlet or towards the tapered end of the funnel or has an axial component with respect to the rounded inner shape which is directed towards the first channel section (K1 ).

16. Device according to one of claims 1 to 15, characterized in that the second channel section (K2), which is connected to the vacuum pump (VP) in Fluid connection can be brought, has a further or second channel constriction (KE2).

17. Device according to one of claims 2 to 16, characterized in that a further or second vacuum pump valve (VV2) arranged in the second channel section (K2) is arranged between the branching area (VB) and the further or second channel constriction (KE2).

18. Device according to one of claims 2 to 17, characterized in that a further or third vacuum pump valve (VV3) arranged in the second channel section (K2) is arranged between the further or second channel constriction (KE2) and the vacuum pump (VP).

19. Device according to one of claims 1 to 18, characterized in that at least a partial area of ​​the inner wall of the branching region (VB) is thermally connected to a coolant.

20. Method for treating workpieces using a device according to any one of claims 1 to 19, the method comprising: a) introducing a workpiece (W) into a process chamber (PK1, PK2, PK3); b) establishing a fluid connection between the branching region (VB) and the vacuum pump (VP) or between the process chamber (PK1, PK2, PK3) and the vacuum pump (VP); c) interrupting the fluid connection between the branching region (VB) or the process chamber (PK1, PK2, PK3) and the vacuum pump (VP); d) establishing a fluid connection between the branching region (VB) and a purge gas source (AT); e) interrupting the fluid connection between the branching region (VB) and the purge gas source (AT).

21. Method according to claim 20, characterized in that the sequence of steps b), c), d) and e) is repeated several times.

22. Method according to claim 20 or 21, characterized in that the purge gas source (AT) comprises air, in particular atmospheric air.

23. Method according to one of claims 20 to 22, characterized in that the purge gas source (AT) comprises an inert gas, in particular nitrogen or argon.

24. Method according to one of claims 20 to 23, characterized in that a first purge gas source comprises air and a second purge gas source comprises an inert gas, in particular nitrogen or argon.

25. Method according to claim 24, characterized in that when performing steps d) and e), the first purge gas source is used first and when performing steps d) and e) last, the second purge gas source is used.

26. Method according to one of claims 20 to 25, characterized in that the method after steps b), c), d) and e) comprises as a further step: f) drying the workpiece (W).

27. Method according to claim 26, characterized in that step f) is carried out in an inert gas environment.

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