# US 2014/0150953 A1 · Device and method for performing and monitoring a plastic laser transmission welding process

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- Number: US 2014/0150953 A1
- Document ID: US20140150953A1
- Status: Published application
- Kind: A1
- Application number: 14/235,145
- Filed: 2012-07-20
- Published: 2014-06-05
- Earliest claimed: 2011-07-25
- Assignees: Lpkf Laser & Electronics AG
- Inventors: Manuel Sieben; Dominik Hertle
- Web page: https://patentgrep.com/patent/US20140150953A1

## CPC

- B29C 65/8253: {by the use of waves or particle radiation, e.g. visual examination, scanning electron microscopy, or X-rays (B29C65/8292 takes precedence)}
- B29C 65/16: Laser beams
- B29C 65/1638: {focusing the laser beam on the interface}
- B29C 65/1674: {making use of laser diodes (B29C65/167 takes precedence)}
- B29C 66/1122: {Single lap to lap joints, i.e. overlap joints (B29C66/45, B29C66/472, B29C66/52272 take precedence)}
- B29C 66/41: {Joining substantially flat articles (B29C66/47 and subgroups take precedence); Making flat seams in tubular or hollow articles (B29C66/51 and subgroups take precedence)}
- B29C 66/952: {by measuring or controlling the wavelength}
- B23K 26/0648: {comprising lenses}
- B23K 31/125: {Weld quality monitoring}
- B29C 65/00: Joining {or sealing} of preformed parts {, e.g. welding of plastics materials}; Apparatus therefor {(general aspects of processes or apparatus for joining preformed parts B29C66/00; using porous material formed by internal pressure generated therein for joining preformed parts B29C44/1228, B29C44/326)}
- B29C 65/1635: {at least passing through one of the parts to be joined, i.e. laser transmission welding}
- B29C 65/1654: {scanning at least one of the parts to be joined}
- B29C 66/836: {Moving relative to and tangentially to the parts to be joined, e.g. transversely to the displacement of the parts to be joined, e.g. using a X-Y table (B29C66/65 takes precedence)}
- B29C 66/91216: {enabling contactless temperature measurements, e.g. using a pyrometer}
- B29C 66/91411: {of the parts to be joined, e.g. the joining process taking the temperature of the parts to be joined into account}
- B29C 66/9161: {by controlling or regulating the heat or the thermal flux, i.e. the heat flux}
- B29C 66/961: {involving a feedback loop mechanism, e.g. comparison with a desired value}
- G01J 5/0014: {for sensing the radiation from gases, flames}
- G01J 5/48: Thermography; Techniques using wholly visual means
- B29C: SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING (making preforms B29B11/00; making laminated products by combining previously unconnected layers which become one product whose layers will remain together B32B37/00 - B32B41/00)
- B23K: SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)

## Abstract

A device and a method for performing and monitoring a plastic laser transmission welding process includes a processing beam source for emitting a processing radiation into a joining zone between two joining members so that a weld seam is formed, a measuring beam source for irradiating a measuring zone with a measuring radiation, a detection unit for detecting the measuring radiation reflected by an interface between the weld seam and its surroundings in the joining members, and an evaluation unit connected to the detection unit for determining the depth position of the interface in the joining members from the detected reflected measuring radiation.

## Claims

### Claim 1

A device for performing and monitoring a plastic laser transmission welding process, the device comprising:
a processing beam source (27) for emitting a processing radiation (26) into a joining zone (1) between two joining members (2, 3) so that a weld seam (4) is formed;
a measuring beam source (6) for irradiating a measuring zone (12) with a measuring radiation (7);
a detection unit (13) for detecting the measuring radiation (7) reflected by an interface (5) between the weld seam (4) and its surroundings in the joining members (2, 3); and
an evaluation unit (15) which is connected to the detection unit (13) for determining a depth position of the interface (5) in the joining members (2, 3) from the measuring radiation (7) which is reflected and detected by the detection unit (13).

### Claim 2 (depends on 1)

The device according to claim 1, wherein the measuring beam source (6) is a point light source which is variably focusable onto the measuring zone (12) by means of a focusing optical system (11) arranged in a beam path of the measuring beam (7), wherein a photo detector (18) serving as detection unit detects an intensity of the reflected measuring beam (7) as a function of the position of a focus (20) relative to the interface (5).

### Claim 3 (depends on 2)

The device according to claim 2, the focusing optical system (11) is arranged so as to be displaceable in a direction of the optical axis for intensity-controlled adjustment of the focus (20) of the measuring beam relative to the interface (5), wherein the depth position of the interface (5) is determinable from a position of the focusing optical system (11).

### Claim 4 (depends on 1)

The device according to claim 1, wherein the measuring beam source (6) is a polychromatic point light source which is focusable, by means of a high-dispersion focusing optical system arranged in beam path of the measuring beam (7), onto the measuring zone (12) so as to be distance-coded depending on a respective wavelength, wherein a spectral-sensitive photo detector (18) serving as detection unit detects the reflected partial measuring beam (7) with the highest intensity depending on the position of the focus (20) relative to the interface (5) so as to determine the depth position of the interface (5).

### Claim 5 (depends on 4)

The device according to claim 4, wherein the focusing optical system (11) has a focusing lens (16) and a distance coding lens (17).

### Claim 6 (depends on 5)

The device according to claim 5, the spectral-sensitive photo detector (18) is formed by a spectrometer with an aperture (9) arranged in front thereof.

### Claim 7 (depends on 5)

The device according to claim 5, wherein the measuring beam (7) is guided to the focusing optical system (11) and the reflected measuring beam (7) is guided to the detection unit (13) by in each case one optical waveguide (25) which are combined by a fiber coupler (23) to form a common beam path in the focusing optical system (11) and the measuring zone (12).

### Claim 8 (depends on 1)

The device according to claim 1, wherein the measuring beam source (6) and the detection unit (13) are arranged relative to each other in a triangulation arrangement.

### Claim 9 (depends on 1)

The device according to claim 1, further comprising a light section sensor (30) comprising the measuring beam source (6) and the detection unit (13), the measuring beam source (6) configured in such a way that the measuring beam source projects a measuring light line (33) onto the measuring zone (12), and
an imaging optical system (24) for imaging a reflected image of the measuring light line (33) onto an image sensor serving as detection unit (13).

### Claim 10 (depends on 1)

The device according to claim 1, wherein the measuring beam source (6) is a secondary beam source of a device for laser beam hybrid welding.

### Claim 11

A method for performing and monitoring a plastic laser transmission welding process, comprising the following steps:
arranging a transmissive (2) and an absorptive joining member (3) in a joining position;
irradiating the joining members (2, 3) in a joining zone (1) with a processing radiation (27) so that a weld seam (4) is formed and in a measuring zone (12) comprising the weld seam (4) with a measuring radiation (7);
detecting the measuring radiation (7) reflected by an interface (5) between the weld seam (4) and its surroundings by means of a detection unit (13); and
evaluating of the detected measuring radiation (7) by means of an evaluation unit (15) connected to the detection unit (13) so as to determine a depth position of the detected interface (5) in the joining members (2, 3).

### Claim 12 (depends on 12)

The method according to claim 12, wherein the measuring radiation (7) is generated by a point light source (6) which is variably focusable by means of a focusing optical system (11), wherein the depth position of the interface (5) is determined by means of a position (P1, P2, P3) of the focusing optical system (11) that is correlated with an intensity of the reflected measuring radiation (7).

### Claim 13 (depends on 12)

The method according to claim 12, wherein the measuring radiation (7) is generated by a polychromatic point light source (6) and emitted into the measuring zone (12) with a focus that is a function of the respective wavelength, wherein the measuring radiation (7), which is reflected as a function of the depth position of the interface, is spectrally detected, and the depth position of the interface (5) is determined by evaluation of a spectral intensity maximum of the reflected measuring radiation (7).

### Claim 14 (depends on 12)

The method according to claim 12, wherein the measuring radiation (7) is formed by a triangulation laser beam which is emitted into the measuring zone (12), wherein the measuring radiation (7) thereof, which is reflected as a function of the depth position of the interface (5), is detected by an image sensor (29) serving as detection unit and the depth position of the interface (5) is determined according to the principles of laser triangulation.

### Claim 15 (depends on 12)

A method according to claim 12, wherein the measuring radiation (7) is formed in such a way that the measuring radiation (7) generates a measuring light line (33) that is projected onto the interface (5), wherein the reflected measuring image thereof is detected as reflected measuring radiation (7) by a light section sensor (30) serving as detection unit, and the depth position of the interface (5) is determined from said reflected measuring radiation (7) according to the principles of the light section method.

### Claim 16 (depends on 12)

The method according to claim 12, wherein the measuring zone (12) is irradiated with a secondary radiation generated during laser beam hybrid welding.

### Claim 17 (depends on 5)

The device according to claim 5, wherein the distance coding lens (17) is configured as a Fresnel lens.