Method for bonding metal parts

Abstract

The present disclosure relates to a method of adhering a first metal part to another part, the method comprising: (a) providing a first metal part, such as a steel part, and another part, such as a second metal part; (b) treating a surface portion of the first metal part intended to be adhered to the other part with laser pulses to remove a surface layer across the surface portion of the first metal part, preferably by ablation; (c) applying pressurized air or a gas stream to the surface portion while applying laser pulses to the surface portion of the first metal part; (d) applying an adhesive to at least the surface portion of the first metal part and / or the surface of the other part; and (e) adhering the first metal part and the other part together.

Description

Technical Field

[0001] The present disclosure relates to a method of adhering a first metal part to another part such as a second metal part, in which at least a surface portion of the first metal part is treated with laser pulses to activate the outer metal surface before applying an adhesive.

Background Art

[0002] It is known to prepare a surface portion of a first metal part intended to be adhered to another part with laser pulses to remove contaminants on the surface of the metal surface and activate the metal surface so that an adhesive adheres better to the metal surface. European Patent No. 3792323 (A1) generally describes such an adhesion method.

[0003] Generally, it is desired to improve adhesion methods including treatment of metal surfaces with laser pulses, specifically to improve such adhesion methods with respect to the purity obtained as a result of the activated metal surface, and to improve the durability of the adhesive bond.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Means for Solving the Problems

[0005] According to at least one aspect, a method of adhering a first metal part to another part, the method comprising: (a) providing a first metal part, such as a steel part, and another part, such as a second metal part; (b) treating a surface portion of the first metal part intended to be adhered to the other part with laser pulses to remove a surface layer of the first metal part over the surface portion, preferably by ablation; (c) applying a pressurized air or gas flow to the surface portion while applying laser pulses to the surface portion of the first metal part; (d) applying an adhesive to at least the surface portion of the first metal part and / or the surface of the other part; and (e) adhering the first metal part and the other part together.

[0006] According to at least one aspect, a method of manufacturing a personal care device comprising adhering a steel shaft to a metal cap, the method comprising: (a) providing a steel shaft and a metal cap sized to receive at least a tip region of the steel shaft; (b) treating a surface portion of the steel shaft intended to be adhered to the metal cap with laser pulses to remove a surface layer from the steel shaft over the surface portion, preferably by ablation; (c) applying a pressurized air or gas flow to the surface portion while treating the surface portion of the steel shaft with laser pulses; (d) treating at least a portion of the inner surface of the metal cap intended to be adhered to the surface portion of the steel shaft with laser pulses; (e) applying an adhesive to the surface portion of the steel shaft and / or a portion of the inner surface of the metal cap; and (f) fitting the metal cap onto the steel shaft and curing the adhesive. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The present disclosure will be made more apparent by the detailed description of the exemplary embodiments and the reference to the drawings.

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Figure 5A

Figure 5B

Figure 6A

Figure 6B

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Figure 8A

Figure 8B

DETAILED DESCRIPTION OF THE INVENTION

[0008] Laser pulse treatment of a metal surface is carried out under an extraction hood or a more locally provided exhaust system to remove metal vapor, i.e., small metal particles generated in the laser pulse induced ablation process, and it has been attempted to avoid the environmental pollution by the air containing the metal vapor. However, it has been found that even a powerful exhaust system cannot reliably remove the metal vapor or particulate metal material from the treatment volume. Here, the treatment volume means at least the volume around the surface portion of the first metal part that has been treated with laser pulses and is typically contaminated with metal vapor. Therefore, the metal particles and / or metal ions of the metal vapor may finally redeposit on the freshly ablated metal surface, which results in a decrease in the purity of the ablated metal surface and thus a decrease in the adhesiveness of the adhesive to the redeposited metal surface. Such redeposition is basically related to all metal surfaces, but it has been found to be particularly problematic on steel surfaces, which is considered to be due to the chromium component contained in the steel.

[0009] According to the present disclosure, a pressurized air or gas flow is directed towards a surface portion of a first metal part being treated with laser pulses, for example, a surface portion where the surface area is ablated by the laser pulses. The pressurized air or gas flow tends to carry away from the treated surface portion, to the surroundings, i.e., into the processing volume, the metal vapor and particulate metal substances released due to the effect of ablation laser pulses that can be considered to cause sublimation and melting of the surface layer depending on the pulse length and additional energy. Due to the rapid sublimation and melting, atoms and particulate substances in the micrometer and sub-micrometer ranges are released into the processing volume around the surface portion being treated. The gas component and the particulate component may generate a plasma that shields the surface portion being treated by the laser pulses, and a part of the laser energy may be absorbed by the plasma, thus the ablation process may be reduced. Furthermore, the particulate substances may collide again onto the ablated surface, and then may cause recontamination of the activated metal surface. It has been found that common recontamination, and in the case of the first metal part made of steel, particularly chromium-containing recontamination, generates loosely adhering recontamination regions that can cause a breaking point in the adhesive applied to the ablated surface. The addition of a pressurized air or gas flow to the treated surface portion can significantly improve the resulting purity of the ablated surface portion, and since the metal particles are carried away by the pressurized air or gas flow, it has been confirmed that the probability of metal particles depositing on the ablated metal surface is reduced. Parts adhered to each other can withstand much higher stresses than parts adhered to each other to which no pressurized air or gas flow is applied, which will be described later.

[0010] The "air flow or gas flow" according to the present disclosure means a flow of normal air, or a flow of an inert gas such as nitrogen and / or argon, and a mixture of air and a purified inert gas can also be considered similarly.

[0011] In the present disclosure, the term "adhesive" shall mean all adhesives suitable for adhering a first metal part to another part, in particular a second metal part. As an example of an adhesive, DELO DUPOPOX CR8016 available from DELO Industrie Klebstoffe GmbH & Co. KGaA (Windach, Germany) may be mentioned.

[0012] As a result, it may seem obvious to apply a pressurized air or gas flow to the metal surface currently being laser ablated. However, it was a rather long process to understand that without applying a pressurized air or gas flow, the expected adhesiveness between the parts ultimately adhered to each other could not be obtained. Specifically, this was the case where such a lack of expected adhesiveness appeared only in a small part of the adhered metal parts in the actual examples further shown below in FIGS. 8A and 8B as examples. First, it was a common general idea that an exhaust system operating under pressure to remove the air present in the processing volume around the processing area, and thus any evaporation material and / or small particles, provides sufficient performance to clean the processing volume from the metal vapor. Second, the pressurized air or gas flow applied to the surface currently being laser ablated was not previously considered by those skilled in the art.

[0013] Various parameters regarding the air or gas flow were investigated with respect to the quality of the ability of the air flow to carry away the metal vapor and / or particulate matter from the processing volume around the surface portion being processed, thereby reducing the recontamination of the freshly activated metal surface. The investigated air or gas flow parameters are the velocity of the air or gas at the surface portion being processed, the velocity of the air or gas at the outlet of the pressure nozzle, the distance of the pressure nozzle to the surface portion being processed, the amount of air or gas delivered by the pressure nozzle (also known as the air fluid volume), the shape of the pressure nozzle, and the orientation and / or position of the pressure nozzle with respect to the surface portion being processed. These air or gas flow parameters are described in more detail below.

[0014] Metal particles generated in a laser pulse-induced ablation process tend to have velocities that can spread into the sonic and supersonic ranges, and it is understood that the speed of sound is 343 m / s in air at 20°C.

[0015] It has been found that the velocity of the pressurized air or gas flow at the surface portion being laser-treated, which is within the range of the velocity of the particulate matter in the processing volume, can result in a more significant reduction in recontamination than higher or much lower velocities. It has been found that a range of 80 m / s to 400 m / s for the velocity of the pressurized air or gas flow at the surface portion being treated is effective.

[0016] Pressurized air or gas flow or jet is typically delivered by a pressurized air or gas delivery system, such as a compressed air or gas reservoir. The pressurized air or gas flow typically exits the pressurized air or gas delivery system via a pressure nozzle. It has also been found that the velocity of the pressurized air or gas delivery system at the pressure nozzle can be in the range of 100 m / s to 700 m / s. The pressurized air or gas may have a compression in the range of 1 bar to 6 bar (these values mean compression above atmospheric pressure), and the compression may preferably be in the range of 2 bar to 5 bar. The pressurized air or gas flow may be directed towards the surface portion of the first metal part being treated with laser pulses. A pressure nozzle having an outlet shape, i.e., the shape of the air or gas outlet, such that the pressurized air or gas flow acting on the surface portion to be treated has a substantially cross-sectional shape following the shape of the surface portion, has been found to tend to result in improved adhesion. This is thought to be because the static pressure of the pressurized air or gas flow on the surface portion to be treated can be made more uniform. Specifically, the static pressure of the pressurized air or gas flow over at least 50% of the surface portion does not deviate by more than about ±20%, preferably more than about ±15%, from the average static pressure value at at least 50% of the surface portion. The surface portion to be treated can specifically be related to the length of the laser pulse line. It can be assumed that the surface portion to be treated has an area that can be covered by laser pulses that are in contact or slightly overlapping. For example, a single laser pulse may be circular and may have a diameter of 50 μm and a pulse length in the range of nanoseconds to femtoseconds. The pulses may be applied at a frequency of 400 kHz. The pulses along the laser line of the pulses may have a center-to-center distance of 20 μm. Thus, a line of pulses having a length of 10 mm may be applied in 1 / 800 s. This means that an area of 1.6 mm2 can be treated within 1 s (ignoring any time required to rotate the laser beam, typically done by a mirror). This means that the surface area to be treated has an extension in length defined by the length of the laser line. As described above, it seems beneficial to use a pressurized air or gas flow that covers the entire length of the laser line.The pressurized air or gas flow can cover the entire width of the surface portion to be treated, but in order to limit the need for pressurized air or gas, the width of the pressurized air or gas flow can also be limited, and then the pressurized air or gas flow can be arranged to follow the laser in the width direction, or the first metal part can be moved to hold the currently treated surface portion within the cross-section of the pressurized air or gas flow. When the first metal part has a total surface portion to be treated that extends circumferentially around the first metal part, the first metal part may rotate so that the currently treated surface portion remains within the cross-section of the pressurized air or gas flow. Then, the width of the pressurized air or gas flow may be selected to be larger than the width of the rotating first metal part so that the pressurized air or gas flow can carry the metal vapor and particulate matter around the first metal part, and the pressurized air or gas flow, together with the carried metal vapor and particulate matter, is finally exhausted by the exhaust system.

[0017] It has been found advisable to arrange a pressure nozzle having an air or gas outlet at a distance in the range of 4 mm to 20 mm, preferably in the range of 8 mm to 16 mm, relative to the surface portion to be treated. Here, the distance is measured between the center point of the air or gas outlet and the center point of the surface portion. Since the speed of the pressurized air or gas flow decreases as the distance increases, it may be advisable to try to arrange the pressure nozzle as close as possible to the first metal part. The pressure nozzle cannot be arranged within the laser path, but can be arranged on either side of the surface portion to be treated, and may preferably be arranged below or above the surface portion to be treated, where "below" or "above" is meant with respect to the line of the laser pulses applied on the surface portion.

[0018] If the entire surface area to be treated with laser pulses is curved, for example, if the entire surface area is the surface of a metal shaft extending circumferentially around a shaft, the laser may be moved around the first metal part, or the first metal part may be moved, for example rotated. This implies that the pressurized air or gas flow need not completely cover the entire surface area intended to be treated with laser pulses, but is sufficient to act on the surface portion currently being treated. This means that if the surface portion currently being treated is longer in one direction than in the vertical direction, the nozzle can essentially have an elliptical or substantially elongated shape, and the major axis of the elliptical or substantially elongated shape can coincide with the longer extension of the surface portion currently being treated.

[0019] An exhaust system, for example, a double-horn exhaust system surrounding the treatment area, may have a suction force in the range of 500 l / min to 3000 l / min, i.e., higher than the air flow provided by the pressurized air or gas flow, and even significantly higher suction force may be acceptable.

[0020] In a practical example, the first metal part is the steel shaft of a personal care device, and the other part is a second metal part, namely a metal cap. The steel shaft may be processed by laser pulses over the entire surface area that can extend circumferentially around the steel shaft. In addition to the laser pre-treatment, generally, the first metal part may first be pre-treated by another method such as plasma pre-treatment to fix the volatile organic compound on the surface of the metal part. Specifically, a turned and polished metal shaft may still contain volatile organic compounds on its surface, and their immobilization before the activation of the metal surface by laser ablation helps to keep the activated surface portion free from contamination. This naturally applies to all first metal parts, regardless of their implementation as a steel shaft. The steel shaft may be made from standard stainless steel and thus may contain a specific proportion, for example, more than 10.5 wt% chromium. Similarly, the metal cap can be made from standard stainless steel, specifically by a deep drawing process as generally known in the art. The inner surface portion of the metal cap may be pre-treated, for example, by plasma pre-treatment and / or laser pre-treatment before bonding, but this should not be considered essential. As illustrated in the description regarding FIG. 8B, the metal cap is bonded onto the tip of the steel shaft, and the metal cap may accommodate further components, such as a permanent magnet.

[0021] For details of the metal bonding process generally including femtosecond laser pulse pre-treatment and optional plasma pre-treatment, reference is made to European Patent No. 3792323 (A1), which is incorporated herein by reference.

[0022] Table 1 below lists relevant values for ultra-fast laser pulse pre-treatment as an example, and the following table provides some ranges that are considered reasonable, even if they do not exclude values outside the proposed range that are also used. Overall, the values may vary to some extent if the optical fluence remains within the proposed range. It is repeatedly emphasized that the addition of pressurized air or gas flow proposed herein is also reasonable for longer or even shorter laser pulse lengths.

[0023] [Table 1]

[0024] The qualitative test method was developed to investigate the strength of the adhesive bond between a first metal part and other parts, and specifically was used to test the strength of the adhesive bond between a steel shaft and a metal cap. In this test method, a hammer was pivotally attached to the end of the shaft, the hammer was deflected until it reached a predetermined stopper, then the hammer was released and accelerated by gravity and applied to the metal cap / steel shaft element. Between each stroke, the metal cap / steel shaft element was rotated approximately 20 to 30 degrees around its longitudinal axis. Metal cap / steel shaft elements manufactured by the above method but additionally without applying pressurized air or gas flow resisted up to approximately 110 hammer strokes from a sample size of 30, and metal cap / steel shaft elements manufactured with the addition of pressurized air or gas flow resisted at least approximately 200 hammer strokes from a sample size of 30. In these hammering tests, in metal cap / steel shaft elements made without pressurized air or gas flow, failure typically occurred at the interface between the adhesive and the steel, that is, it was also found that when the metal cap could be manually separated from the steel shaft, essentially no adhesive residue adhered to the steel shaft. In contrast, in metal cap / steel shaft elements made using pressurized air or gas flow, failure typically occurred within the adhesive, that is, when the metal cap could be separated from the steel shaft using manual force, adhesive residue remained on the steel shaft. This indicated that the surface adhesion between the adhesive and the steel surface was significantly improved when pressurized air or gas flow was added in the manufacturing method.

[0025] Figure 1 is a diagram of a first exemplary configuration 1 for the pretreatment of a surface portion 110 of a first metal part 100 by a laser pulse, preferably a laser pulse having a pulse length in the nanosecond, picosecond, or femtosecond range. The arrow indicates the path 10 of the laser beam applied to the surface portion 110 during operation. An exhaust system 200 with a double - horn structure having a first suction horn 210 and a second suction horn 220 is arranged to exhaust air and / or gas and / or any vapor or particulate matter from the processing volume 190 around the first metal part 100. The first metal part 100 is here in the shape of a shaft and may be a steel shaft. Although not relevant to the description of Figure 1, the first metal part 100 is here intended to extend from a complete inner motor chassis that, after another part, namely a metal cap, is adhered to the steel shaft, is inserted onto the housing of a personal care device. The pressure nozzle part 301 of a pressurized air or gas delivery system 300 is provided outside the path 10 of the laser pulse and directs a pressurized air or gas stream (see Figure 3) onto the surface portion 110 of the first metal part 100 being processed by the laser pulse during operation via a pressure nozzle 310 having an air or gas outlet 311. The air or gas outlet 311 is provided so that the pressurized air or gas stream is directed onto the surface portion 110 being processed. More precisely, in the illustrated example, since the entire surface area processed by the laser pulse extends circumferentially around the first metal part 100, the pressurized air or gas stream is directed onto the surface portion 110 currently being processed by the laser pulse, i.e., the surface portion 110 from which metal vapor and particulate matter are being released into the processing volume 190. The first metal part 100 may be arranged to be movable, for example, rotatable about its longitudinal axis during processing, so that the laser can process all regions of the entire surface portion to be processed. The laser beam may also be arranged to have a moving laser beam, and the laser point on the first metal part 100 may be moved up and down, whereby the rotation of the first metal part 100 is compensated and the laser point may trace an hourglass - shaped path on the surface portion so that the laser moves along parallel lines along the first metal part 100.Instead of rotating, or in addition to rotating, the first metal part 100 may be linearly moved.

[0026] FIG. 2 is a cross-sectional view of another exemplary configuration 1A for the pretreatment of the surface portion 110A of the first metal part 100A by a laser pulse. An exhaust system 200A having a double-horn structure with a first suction horn 210A and a second suction horn 220A is arranged to exhaust air and / or gas and / or any vapor or particulate matter from the processing volume 190A around the first metal part 100A. A pressurized air or gas delivery system 300A is integrated into the exhaust system 200A, specifically, integrated into the first suction horn 210A. A pressure nozzle 310A having an air or gas outlet 311A is arranged to provide a pressurized air or gas stream directed onto the surface portion 110A of the first metal part 100A. A notch 211A is provided in the first suction horn 210A to provide a free path region for the laser beam to irradiate the surface portion 110A. The pressurized air or gas delivery system 300A (here only the nozzle portion is shown) may be at least partially integral with the first suction horn 210A, or may be a separate component that can fit, for example, into the first suction horn 210A.

[0027] FIG. 3 is a depiction of a simulation adding a pressurized air or gas stream 320B discharged from a pressure nozzle 310B, where the dot density indicates the velocity of the air or gas particles. FIG. 3 represents a two-dimensional cross-section of the simulated velocity profile of the pressurized air or gas stream 320B, which here acts centrally on a rotationally symmetric first metal part 100B, and the first metal part 100B may here be a steel shaft that is rotationally symmetric about the longitudinal axis L. FIG. 3 is here shown as an example of a simulation showing promising results regarding the quality of the pressurized air and gas stream.

[0028] FIG. 4 shows the static pressure P on the surface of the first metal part as shown in FIG. 3 SDescriptions of two graphs 401 and 402 are shown. Referring to FIG. 3, the static pressure was simulated along a line from the bottom to the tip of the surface portion of the first metal part. Graphs 401 and 402 show the static pressure along the described line of the cross-sectional view shown in FIG. 3. For graph 401, in FIG. 4, when the outlet opening of the pressure nozzle is elongated or elliptical, the cross-sectional shape of the pressurized air or gas flow is substantially the same as the shape of the surface portion currently being processed by the laser pulse, specifically the length extension, so that the static pressure P S can be made relatively uniform over a larger portion of the surface portion being processed. This serves, on the one hand, to direct the pressurized air or gas flow only to the processed surface portion instead of directing it to the side regions where the energy would be lost without causing an effect. On the other hand, this helps to avoid recontamination due to the flow of air or gas from regions of high static pressure to regions of low static pressure. Graph 420 relates to a circular pressure nozzle sized such that the pressurized air or gas flow does not extend beyond the first metal part in a direction perpendicular to the line along which the static pressure was simulated. The hammering test as described above shows that, as shown by graph 410, when the pressurized air or gas flow causes a static pressure P S the adhesive bond can withstand more hammer strokes.

[0029] FIG. 5A is an SEM photograph of the surface of a metal part, specifically a steel shaft surface, processed with a femtosecond laser to ablate the upper layer without the application of pressurized air or gas flow. SEM represents a scanning electron microscope. A scale indicating 500 nm is shown. Various structures can be seen that are thought to be related to recontamination by particulate matter generated during the ablation process. As described above, such recontamination, especially by metal particles that do not strongly adhere to the surface of an activated metal part such as chromium, is thought to result in a failure point for the adhesive bond.

[0030] Figure 5B is again an SEM photograph of a similar metal part surface of the same scale of 500 nm from a steel shaft processed with a femtosecond laser to ablate the upper layer, and pressurized air or a gas flow was applied during the application of the laser pulse. The metal surface shows fewer structures related to the recontamination of the metal surface by particulate matter and evaporated surface material, as seen in Figure 5A. As previously explained, the addition of pressurized air or a gas flow caused a surprising effect by what seems to be a reduction in the recontamination of the ablated metal surface. The effect on the adhesiveness of the adhesive resulted in an improvement as described above, namely, much better adhesiveness to the metal surface bonding.

[0031] The effect of the pressurized air or gas flow is thought to exist for other laser pulse lengths beyond femtosecond laser pulses, such as picosecond or nanosecond laser pulses and attosecond laser pulses.

[0032] Figure 6A is a photograph of a steel metal shaft processed with femtosecond laser pulses without adding pressurized air or a gas flow and adhered to a metal cap, and the adhesive joint was tested by the above-described hammering method. It can be seen that essentially no macroscopic adhesive residue remains on the metal surface. In contrast, Figure 6B shows a photograph of a steel shaft that is basically the same as that shown in Figure 6A. This steel shaft was also processed with a femtosecond laser, and at the same time, pressurized air or a gas flow as proposed herein was applied. The steel shaft was adhered to the metal cap, and then the adhesive joint was tested by the hammering method. Many adhesive residues remained on the steel shaft. The latter is evidence that the presence of fracture points on the steel shaft surface due to recontamination was effectively reduced, and although the hammering method broke the adhesive, it did not cause loosening of the adhesive joint between the adhesive and the metal surface.

[0033] FIG. 7 shows a perspective view of an exemplary nozzle portion 301C of a pressurized air or gas delivery system. The line of sight is from approximately the center point on the surface portion being processed on the first metal part in a pretreatment configuration as exemplarily shown in FIGS. 1 and 2. The nozzle portion 301C includes a pressure nozzle 310C having an elongated air or gas outlet 311C. The pressure nozzle 310C is also connected to an essentially circular delivery hole 312C, and it can be seen that the pressure nozzle 311C provides a transition from this circular cross-section to the elongated cross-section at the front of the pressure nozzle 310C, where the cross-section widens in the length direction and narrows somewhat in the width direction. The cross-sectional shape at the front of the pressure nozzle 310C can here be described as a rhombus (i.e., a rectangle having two semi-circles at the small ends of the rectangle). The air or gas outlet 311C is shaped such that the pressurized air or gas flow covers the entire length of the surface portion to be treated by the laser pulse.

[0034] FIG. 8A is a view of an exemplary personal care device 50 implemented as an electric toothbrush having a handle portion 51 and a treatment head 52 implemented here as an interchangeable brush head. The treatment head 52, in the example shown, includes a functional head 53 that can be driven in a vibratory-rotary motion relative to the housing of the treatment head 52.

[0035] FIG. 8B is an enlarged view of a part of the personal care device 50 shown in FIG. 8A, and the enlarged part is shown in a partially cut-away state so that the connection between the drive shaft 510 of the handle part 51 and the motion transmission part 520 of the treatment head 52 can be seen. The drive shaft 510 is driven in a linear reciprocating motion V during operation, and this linear reciprocating motion V is transmitted to the functional head 53 of the treatment head 52 via the motion transmission device 520, where the linear reciprocating motion is transmitted to the oscillatory rotation of the functional head 53. The drive shaft 510 may be a steel shaft adhered to the metal cap 511. According to the present disclosure, at least a part of the outer surface of the steel shaft is treated with laser pulses under the simultaneous application of pressurized air or gas flow. At least a part of the inner surface of the metal cap is optionally treated with laser pulses. In the example shown in particular, a permanent magnet 512 is arranged in the metal cap 511 and the internal cavity of the metal cap 511 is filled with an adhesive 513. The permanent magnet 512 is coupled to, for example, a magnetizable steel element 521 arranged at the opposite end of the motion transmission device 520. The adhesive joint created by the above-described adhesive method durably joins the steel shaft 510 and the metal cap 511 even under the periodic load acting on the metal cap by the linear reciprocating motion V and also under the aggressive environment formed by toothpaste and saliva. It will be understood that the examples shown in FIGS. 8A and 8B do not limit the scope of the present disclosure.

[0036] The dimensions and values disclosed in this specification are not to be understood as being strictly limited to the exact numerical values recited. Instead, unless otherwise specified, each such dimension is intended to mean both the recited value and the functionally equivalent range surrounding that value. For example, a dimension disclosed as "40 mm" is intended to mean "about 40 mm".

Claims

1. A method for adhering a first metal part to another part, comprising: providing a first metal part, such as a steel shaft, and another part, such as a second metal part; treating a surface portion of the first metal part intended to be adhered to the other part with laser pulses to remove a surface layer of the first metal part over the surface portion, preferably by ablation; applying pressurized air or a gas flow to the surface portion while applying laser pulses to the surface portion of the first metal part; applying an adhesive to at least the surface portion of the first metal part and / or the surface of the other part; adhering the first metal part and the other part to each other.

2. The method according to claim 1, wherein the pressurized air or gas flow has a velocity in the range of 80 m / s to 400 m / s at the surface portion.

3. The method according to claim 1 or 2, wherein the air flow rate or gas flow rate of the pressurized air or gas flow is in the range of 50 l / min to 400 l / min.

4. The method according to any one of claims 1 to 3, wherein the angle between the center line of the pressurized air or gas flow and the center line of the laser pulses is in the range of 10 degrees to 35 degrees.

5. The method according to any one of claims 1 to 4, wherein the static pressure of the pressurized air or gas flow over at least 50% of the surface portion does not deviate by more than about ±20% from the average static pressure value at at least 50% of the surface portion.

6. The method according to any one of claims 1 to 5, wherein the pressurized air or gas flow is provided by a pressure nozzle having an outlet for air or gas with a distance to the surface portion in the range of 4 mm to 20 mm, preferably in the range of 8 mm to 16 mm, the distance being measured between the center point of the outlet of the air or gas and the center point of the surface portion.

7. The method according to claim 6, wherein the pressure nozzle has a shape such that the cross-sectional shape of the pressurized air or gas flow acting on the surface portion of the first metal part substantially follows the shape of the surface portion.

8. The method according to claim 6 or 7, wherein the velocity of the pressurized air or gas flow at the outlet of the air or gas of the pressure nozzle is in the range of 100 m / s to 700 m / s.

9. The method according to any one of claims 6 to 8, wherein the pressurized air or gas flow is delivered from a compressed air or gas reservoir or an air or gas compressor, and the air or gas is compressed in the range of 1 bar to 6 bar, preferably in the range of 2 bar to 5 bar.

10. The method according to any one of claims 1 to 9, comprising the step of exhausting air and / or gas from the processing volume at an exhaust rate of 500 l / min to 3000 l / min.

11. The method according to any one of claims 1 to 10, comprising the step of rotating the first metal part about a longitudinally extending axis, wherein all surface portions intended to be adhered to the other part extend circumferentially around the first metal part.

12. The method according to any one of claims 1 to 11, wherein the laser pulse has a pulse length in the range from nanoseconds to femtoseconds.

13. A method of manufacturing a personal care device comprising the step of adhering a steel shaft to a metal cap, providing the steel shaft and the metal cap sized to receive at least the tip region of the steel shaft, processing a surface portion of the steel shaft intended to be adhered to the metal cap with a laser pulse to remove a surface layer extending over the surface portion from the steel shaft, preferably by ablation, while processing the surface portion of the steel shaft with the laser pulse, also applying a pressurized air or gas flow to the surface portion, processing at least a part of the inner surface of the metal cap intended to be adhered to the surface portion of the steel shaft with a laser pulse, applying an adhesive to the surface portion of the steel shaft and / or the portion of the inner surface of the metal cap, fitting the metal cap onto the steel shaft and curing the adhesive.

14. The method according to claim 13, wherein the pressurized air or gas flow has a velocity in the range of 80 m / s to 400 m / s at the surface portion.

15. The method according to claim 13 or 14, wherein the pressure nozzle for delivering the pressurized air or gas flow has a shape such that the cross-sectional shape of the pressurized air or gas flow acting on the surface portion of the first metal part substantially follows the shape of the surface portion.

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