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Evaluation of non-contact methods for joint tracking in a laser beam welding application
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). (PTW)ORCID-id: 0000-0001-5734-294X
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). (PTW)ORCID-id: 0000-0001-6933-375X
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). (PTW)ORCID-id: 0000-0001-7748-0565
Högskolan Väst, Institutionen för ingenjörsvetenskap, Avdelningen för produktionssystem (PS). (PTW)ORCID-id: 0000-0002-8771-7404
Visa övriga samt affilieringar
2016 (Engelska)Ingår i: The 7th International Swedish Production Symposium, Conference Proceedings: 25th – 27th of October 2016, Lund: Swedish Production Symposium , 2016, s. 1-6Konferensbidrag, Publicerat paper (Refereegranskat)
Abstract [en]

The use of automated laser welding is a key enabler for resource efficient manufacturing in several industrial sectors. One disadvantage with laser welding is the narrow tolerance requirements in the joint fit-up. This is the main reason for the importance of joint tracking systems. This paper describes anevaluation of four non-contact measurement methods to measure the position, gap width and misalignment between superalloy plates. The evaluation was carried out for increased knowledge about the possibilities and limitations with the different methods. The methods are vision-, laser-line-,thermography- and inductive probe systems which are compared in an experimental setup representing a relevant industrial application. Vision is based on a CMOS camera, where the image information is used directly for the measurements. Laser-line is based on triangulation between a camera and a projected laserline. Thermography detects the heat increase in the gap width due to external heat excitation. Inductive probe uses two eddy current coils, and by a complex response method possibilities to narrow gap measurement is achieved. The results, evaluated by comparing the data from the different systems, clearly highlights possibilities and limitations with respective method and serves as a guide in the development of laser beam welding.

Ort, förlag, år, upplaga, sidor
Lund: Swedish Production Symposium , 2016. s. 1-6
Nyckelord [en]
Joint tracking, Gap width, Misalignment, Inductive coil, Thermography, Laser line, Vision sensor
Nationell ämneskategori
Bearbetnings-, yt- och fogningsteknik
Forskningsämne
Produktionsteknik; TEKNIK, Produktions- och materialteknik
Identifikatorer
URN: urn:nbn:se:hv:diva-10147OAI: oai:DiVA.org:hv-10147DiVA, id: diva2:1047294
Konferens
7th Swedish Production Symposium, Lund, Sweden, October 25-27, 2016
Anmärkning

Ingår i lic.uppsats

Tillgänglig från: 2016-11-17 Skapad: 2016-11-17 Senast uppdaterad: 2022-11-08Bibliografiskt granskad
Ingår i avhandling
1. Inductive measurement of narrow gaps for high precision welding of square butt joints
Öppna denna publikation i ny flik eller fönster >>Inductive measurement of narrow gaps for high precision welding of square butt joints
2016 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

A recent method in aero engine production is to fabricate components from smaller pieces, rather than machining them from large castings. This has made laser beam welding popular, offering high precision with low heat input and distortion, but also high productivity. At the same time, the demand for automation of production has increased, to ensure high quality and consistent results. In turn, the need for sensors to monitor and control the laser welding process is increasing. In laser beam welding without filler material, the gap between the parts to be joined must be narrow. Optical sensors are often used to measure the gap, but with precise machining, it may become so narrow that it is difficult to detect, with the risk of welding in the wrong position. This kind of problems can cause severe welding defects, where the parts are only partially joined without any visible indication. This thesis proposes the use of an inductive sensor with coils on either side of the gap. Inducing currents into the metal, such a sensor can detect even gaps that are not visible. The new feature of the proposal is based on using the complex response of each coil separately to measure the distance and height on both sides of the gap, rather than an imbalance from the absolute voltage of each coil related to gap position. This extra information allows measurement of gap width and misalignment as well as position, and decreases the influence from gap misalignment to the position measurement. The sensor needs to be calibrated with a certain gap width and height alignment. In real use,these will vary, causing the sensor to be less accurate. Using initial estimates ofthe gap parameters from the basic sensor, a model of the response can be used to estimate the measurement error of each coil, which in turn can be used for compensation to improve the measurement of the gap properties.The properties of the new method have been examined experimentally, using a precise traverse mechanism to record single coil responses in a working range around a variable dimension gap, and then using these responses to simulate a two coil probe. In most cases errors in the measurement of weld gap position and dimensions are within 0.1 mm.The probe is designed to be mounted close to the parts to be welded, and will work in a range of about 1 mm to each side and height above the plates. This is an improvement over previous inductive sensors, that needed to be guided to the mid of the gap by a servo mechanism.

Ort, förlag, år, upplaga, sidor
Trollhättan: University West, 2016. s. 48
Serie
Licentiate Thesis: University West ; 14
Nyckelord
Eddy current, Seam tracking, Measurement, Laser beam welding
Nationell ämneskategori
Bearbetnings-, yt- och fogningsteknik
Forskningsämne
Produktionsteknik; TEKNIK, Produktions- och materialteknik
Identifikatorer
urn:nbn:se:hv:diva-10150 (URN)978-91-87531-45-3 (ISBN)978-91-87531-44-6 (ISBN)
Presentation
2016-11-28, C118, Högskolan Väst, Trollhättan, 10:15
Handledare
Tillgänglig från: 2016-11-21 Skapad: 2016-11-17 Senast uppdaterad: 2019-12-03Bibliografiskt granskad
2. Optical detection of joint position in zero gap laser beam welding
Öppna denna publikation i ny flik eller fönster >>Optical detection of joint position in zero gap laser beam welding
2017 (Engelska)Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

This thesis presents an experimental study on how to track zero gaps between metal sheets to be joined by laser beam butt welding. Automated laser beam welding is gaining interest due to its ability to produce narrow and deep welds giving limited heat input and therefore less distortions compared to other processes, such as arc-welding. The automated laser beam welding process is however sensitive to how the high power laser is positioned with regards to the joint position. Deviations from the joint position may occur due to inaccuracies of the welding robot and fixturing, changes in joint geometry, process induced distortions, etc. Welding with an offset from the joint position can result inlack of sidewall fusion, a serious defect that is hard to detect. This work develops and evaluates three monitoring systems to be used during welding in order to be able to later control the laser beam spot position. (i) A monitoring systemis developed for three different photo diodes, one for the visual spectrum of the process emissions, one for the infrared spectrum, and one for the reflected highpower laser light. The correlation between the signals from the photodiodes and the welding position relative to the joint is analysed using a change detection algorithm. In this way an indication of a path deviation is given. (ii) A visual camera with matching illumination and optical filters is integrated into the laser beam welding tool in order to obtain images of the area in front of the melt pool. This gives a relatively clear view of the joint position even during intense spectral disturbances emitted from the process, and by applying animage processing algorithm and a model based filtering method the joint positionis estimated with an accuracy of 0.1 mm. (iii) By monitoring the spectral emissions from the laser induced plasma plume using a high speed and high resolution spectrometer, the plasma electron temperature can be estimated from the intensities of two selected spectral lines and this is correlated to the welding position and can be used for finding the joint position.

Ort, förlag, år, upplaga, sidor
Trollhättan: University West, 2017. s. 64
Serie
Licentiate Thesis: University West ; 15
Nyckelord
Laser beam welding, Optical sensors, Joint tracking
Nationell ämneskategori
Bearbetnings-, yt- och fogningsteknik
Forskningsämne
Produktionsteknik; TEKNIK, Produktions- och materialteknik
Identifikatorer
urn:nbn:se:hv:diva-10684 (URN)978-91-87531-50-7 (ISBN)978-91-87531-49-1 (ISBN)
Handledare
Tillgänglig från: 2017-02-10 Skapad: 2017-02-09 Senast uppdaterad: 2022-09-19
3. An inductive gap measurement method for square butt joints
Öppna denna publikation i ny flik eller fönster >>An inductive gap measurement method for square butt joints
2019 (Engelska)Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
Abstract [en]

A recent method in aero engine production is to fabricate components from smaller pieces, rather than machining them from large castings. This has made laser beam welding popular, offering high precision with low heat input and distortion, but also high productivity. At the same time, the demand for automation of production has increased, to ensure high quality and consistent results. In turn, the need for sensors to monitor and control the laser welding process is increasing. In laser beam welding without filler material, the gap between the parts to be joined must be narrow. Optical sensors are often used to measure the gap, but with precise machining, it may become so narrow that it is difficult to detect, with the risk of welding in the wrong position. This thesis proposes the use of an inductive sensor with coils on either side of the gap. Inducing currents into the metal, such a sensor can detect even gaps that are not visible. The new feature of the proposal is based on using the complex response of each coil separately to measure the distance and height on both sides of the gap, rather than an imbalance from the absolute voltage of each coil related to gap position. This extra information allows measurement of gap width and alignment as well as position in a working range of about 1 mm around the gap, and decreases the influence from variation in gap alignment to the position measurement. The sensor needs to be calibrated with a certain gap width and height alignment. In real use, these will vary, causing the sensor to be less accurate. Using initial estimates of the gap parameters from the basic sensor, a model ofthe response can be used to estimate the measurement error of each coil, whichin turn can be used for compensation to improve the measurement of the gap properties. The properties of the new method have been examined experimentally, using aprecise traverse mechanism to record single coil responses in a working range around a variable dimension gap, and then using these responses to simulate atwo coil probe. In most cases errors in the measurement of weld gap position and dimensions are within 0.1 mm. Different coil orientations were studied using numerical simulation, and validated in experiments using a two coil probe. The influence of scratches, chamfers and variation in plate thickness was investigated at different frequencies.

Ort, förlag, år, upplaga, sidor
Trollhättan: University West, 2019. s. 60
Serie
PhD Thesis: University West ; 30
Nyckelord
Eddy current; Seam tracking; Measurement; Laser beam welding; gap geometry
Nationell ämneskategori
Bearbetnings-, yt- och fogningsteknik
Forskningsämne
Produktionsteknik; TEKNIK, Produktions- och materialteknik
Identifikatorer
urn:nbn:se:hv:diva-13841 (URN)978-91-88847-33-1 (ISBN)978-91-88847-32-4 (ISBN)
Disputation
2019-05-28, F104 Albertssalen, Högskolan Väst, Trollhättan, 10:00 (Engelska)
Opponent
Handledare
Tillgänglig från: 2019-05-10 Skapad: 2019-05-10 Senast uppdaterad: 2019-12-10Bibliografiskt granskad

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Sikström, FredrikRunnemalm, AnnaBroberg, PatrikNilsen, MorganSvenman, Edvard

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Sikström, FredrikRunnemalm, AnnaBroberg, PatrikNilsen, MorganSvenman, Edvard
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