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Pocorni, Jetro KennethORCID iD iconorcid.org/0000-0001-6261-2019
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Publikasjoner (10 av 14) Visa alla publikasjoner
Cheng, W., Zhang, Y., Gao, X., Pocorni, J. K. & Jiang, X. (2024). A Low-Cost Laser Welding Monitoring Framework Based on Depth-Wise Separable Convolution with Photoelectric Signals. International Journal of Precision Engineering and Manufacturing (IJPEM)
Åpne denne publikasjonen i ny fane eller vindu >>A Low-Cost Laser Welding Monitoring Framework Based on Depth-Wise Separable Convolution with Photoelectric Signals
Vise andre…
2024 (engelsk)Inngår i: International Journal of Precision Engineering and Manufacturing (IJPEM), ISSN 2234-7593, E-ISSN 2005-4602Artikkel i tidsskrift (Fagfellevurdert) Epub ahead of print
Abstract [en]

In recent years, the process monitoring based on optical radiation detection widely applied in laser welding monitoring process, such as visual cameras, spectrometers and photoelectric sensors. This study proposes a low-cost monitoring model based on a CNN module with the combination of convolution and depth-wise separable convolution (DSC) applying the industrial photoelectric sensors. This model aims to generate more effective features from the primitive signals captured by the visible light photoelectric sensor and the reflective laser photoelectric sensor, without pre-processing in advance. The DSC is applied to generate features to reveal the inherent features of welding statuses, and especially reduce the computing costs during monitoring process. The proposed model in this study acquired high accuracy with low space complexity and time complexity compared with the traditional model. The model also performs well under the limited and unbalanced welding data, indicating its good robustness. This study provides a low-cost method for real-time monitoring of laser welding process.

sted, utgiver, år, opplag, sider
Springer, 2024
Emneord
Laser welding, Depth-wise separable convolution, Photoelectric signal, Welding defect monitoring
HSV kategori
Forskningsprogram
Teknik, Maskinteknik
Identifikatorer
urn:nbn:se:lnu:diva-131852 (URN)10.1007/s12541-024-01076-7 (DOI)001268447100001 ()2-s2.0-85198112428 (Scopus ID)
Tilgjengelig fra: 2024-08-15 Laget: 2024-08-15 Sist oppdatert: 2024-09-13
Ziada, O., Schauerte, T., Pocorni, J. K., Algabroun, H., Bolmsjö, G. & Håkansson, L. (2022). Robotic Window Assembly: A Simulation Study and a Proposed Self-Adaptive Software Architecture. In: Proceedings of the 10th Swedish Production Symposium: . Paper presented at SPS2022 - The 10th Swedish Production Symposium (pp. 111-121). IOS Press
Åpne denne publikasjonen i ny fane eller vindu >>Robotic Window Assembly: A Simulation Study and a Proposed Self-Adaptive Software Architecture
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2022 (engelsk)Inngår i: Proceedings of the 10th Swedish Production Symposium, IOS Press, 2022, s. 111-121Konferansepaper, Publicerat paper (Fagfellevurdert)
Abstract [en]

The key driving factors in using humans and robots in collaborativeapplications for assembly processes are to reduce assembly time, cost and toimprove the human working environment from an ergonomic viewpoint. Currently,there are limited automated procedures in assembly operations in house constructionbecause the traditional type of assembly process depends entirely on manpower.This is common in the assembly process in different industries since assembly isone of the most demanding and intense manufacturing processes, and it is difficultto automate. This paper presents a case study on the implementation of human-robotcollaboration for window assembly by way of an offline robot programmingsimulation. A self-adaptive software architecture that runs on a real-time targetmachine is also proposed for robotic window assembly. The window assemblymethod that will be used in this study is called “Click-In” and is manufactured byFixture System Sweden AB. Apart from robot simulations, detailed suggestions aregiven for building a pilot cell for robot window assembly. The case study presentedin this paper has both economical and ergonomic goals. The economic goal is toreduce the assembly time which will lead to an increase in window production. Byintroducing human-robot collaboration, operators do not need to performuncomfortable assembly operations—rather the robot will perform these unergonomic operations. The feasibility of both goals is verified with offline robotprogramming simulation. 

sted, utgiver, år, opplag, sider
IOS Press, 2022
Serie
Advances in Transdisciplinary Engineering, ISSN 2352-751X, E-ISSN 2352-7528 ; 21
HSV kategori
Forskningsprogram
Teknik, Maskinteknik
Identifikatorer
urn:nbn:se:lnu:diva-112740 (URN)10.3233/ATDE220131 (DOI)2-s2.0-85132793937 (Scopus ID)9781643682709 (ISBN)9781643682716 (ISBN)
Konferanse
SPS2022 - The 10th Swedish Production Symposium
Tilgjengelig fra: 2022-05-05 Laget: 2022-05-05 Sist oppdatert: 2023-04-06bibliografisk kontrollert
Pocorni, J. K., Powell, J., Frostevarg, J. & Kaplan, A. F. .. (2018). Dynamic laser piercing of thick section metals. Optics and lasers in engineering, 100, 82-89
Åpne denne publikasjonen i ny fane eller vindu >>Dynamic laser piercing of thick section metals
2018 (engelsk)Inngår i: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 100, s. 82-89Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Before a contour can be laser cut the laser first needs to pierce the material. The time taken to achieve piercing should be minimised to optimise productivity. One important aspect of laser piercing is the reliability of the process because industrial laser cutting machines are programmed for the minimum reliable pierce time. In this work piercing experiments were carried out in 15 mm thick stainless steel sheets, comparing a stationary laser and a laser which moves along a circular trajectory with varying processing speeds. Results show that circular piercing can decrease the pierce duration by almost half compared to stationary piercing. High speed imaging (HSI) was employed during the piercing process to understand melt behaviour inside the pierce hole. HSI videos show that circular rotation of the laser beam forces melt to eject in opposite direction of the beam movement, while in stationary piercing the melt ejects less efficiently in random directions out of the hole.

sted, utgiver, år, opplag, sider
Elsevier, 2018
HSV kategori
Forskningsprogram
Teknik, Maskinteknik
Identifikatorer
urn:nbn:se:lnu:diva-111351 (URN)10.1016/j.optlaseng.2017.07.012 (DOI)2-s2.0-85026484330 (Scopus ID)
Forskningsfinansiär
EU, FP7, Seventh Framework ProgrammeEU, FP7, Seventh Framework Programme, 314410
Tilgjengelig fra: 2022-04-15 Laget: 2022-04-15 Sist oppdatert: 2022-04-25bibliografisk kontrollert
Pocorni, J. K., Powell, J., Frostevarg, J. & Kaplan, A. F. .. (2018). The geometry of the cutting front created by Fibre and CO2 lasers when profiling stainless steel under standard commercial conditions. Optics and Laser Technology, 103, 318-326
Åpne denne publikasjonen i ny fane eller vindu >>The geometry of the cutting front created by Fibre and CO2 lasers when profiling stainless steel under standard commercial conditions
2018 (engelsk)Inngår i: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 103, s. 318-326Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Cutting fronts created by CO2 and fibre lasers in stainless steel at thicknesses between 2 mm and 10 mm have been ‘frozen’ and their geometry has been measured. Standard commercial cutting parameters were used to generate the cuts for both types of laser. The resulting three-dimensional cutting front shapes have been curve fitted as polynomials and semicircles. Various features of the cutting front geometry are discussed including the lack of correlation of the cut front inclination with either the relevant Brewster angle or the inclination of the striations on the cut edge.

sted, utgiver, år, opplag, sider
Elsevier, 2018
HSV kategori
Forskningsprogram
Teknik, Maskinteknik
Identifikatorer
urn:nbn:se:lnu:diva-111352 (URN)10.1016/j.optlastec.2018.01.055 (DOI)2-s2.0-85041470309 (Scopus ID)
Tilgjengelig fra: 2022-04-15 Laget: 2022-04-15 Sist oppdatert: 2022-04-25bibliografisk kontrollert
Pocorni, J. K., Powell, J., Deichsel, E., Frostevarg, J. & Kaplan, A. F. .. (2017). Fibre laser cutting stainless steel: Fluid dynamics and cut front morphology. Optics and Laser Technology, 87, 87-93
Åpne denne publikasjonen i ny fane eller vindu >>Fibre laser cutting stainless steel: Fluid dynamics and cut front morphology
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2017 (engelsk)Inngår i: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 87, s. 87-93Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

In this paper the morphology of the laser cut front generated by fibre lasers was investigated by observation of the ‘frozen’ cut front, additionally high speed imaging (HSI) was employed to study the fluid dynamics on the cut front while cutting. During laser cutting the morphology and flow properties of the melt film on the cut front affect cut quality parameters such as cut edge roughness and dross (residual melt attached to the bottom of the cut edge). HSI observation of melt flow down a laser cutting front using standard cutting parameters is experimentally problematic because the cut front is narrow and surrounded by the kerf walls. To compensate for this, artificial parameters are usually chosen to obtain wide cut fronts which are unrepresentative of the actual industrial process. This paper presents a new experimental cutting geometry which permits HSI of the laser cut front using standard, commercial parameters. These results suggest that the cut front produced when cutting medium section (10 mm thick) stainless steel with a fibre laser and a nitrogen assist gas is covered in humps which themselves are covered by a thin layer of liquid. HSI observation and theoretical analysis reveal that under these conditions the humps move down the cut front at an average speed of approximately 0.4 m/s while the covering liquid flows at an average speed of approximately 1.1 m/s, with an average melt depth at the bottom of the cut zone of approximately 0.17 mm.

sted, utgiver, år, opplag, sider
Elsevier, 2017
HSV kategori
Forskningsprogram
Teknik, Maskinteknik
Identifikatorer
urn:nbn:se:lnu:diva-111353 (URN)10.1016/j.optlastec.2016.08.002 (DOI)2-s2.0-84982085472 (Scopus ID)
Tilgjengelig fra: 2022-04-15 Laget: 2022-04-15 Sist oppdatert: 2022-04-25bibliografisk kontrollert
Pocorni, J. K., Powell, J., Frostevarg, J. & Kaplan, A. F. H. (2017). Investigation of the piercing process in laser cutting of stainless steel. Journal of laser applications, 29(2), Article ID 022201.
Åpne denne publikasjonen i ny fane eller vindu >>Investigation of the piercing process in laser cutting of stainless steel
2017 (engelsk)Inngår i: Journal of laser applications, ISSN 1042-346X, E-ISSN 1938-1387, Vol. 29, nr 2, artikkel-id 022201Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This paper investigates the laser piercing process which precedes nearly every laser cutting operation. The two most important aspects of the piercing process are: (a) How long does it take to pierce the material? and (b) How wide is the pierced hole? If the hole is no wider than the cut line, the material can be pierced on the line to be cut. In this paper, 10 mm thick stainless steel was pierced by a multikilowatt fiber laser to compare efficiency and quality when piercing with a continuous wave output and a selected range of power modulation parameters. The different processes were observed by high speed imaging and subsequently examined by visual observation. High speed imaging is used to time the penetration event and to study the laser-material interactions involved in drilling the pierced holes. The results show that appropriate laser power modulation settings can considerably reduce both the piercing time and the required energy to generate any piercing hole required for the subsequent cutting process. This pulse-pierce technique and the differences between piercing with a continuous and a power modulated laser beam are further explained and discussed. Also, the effect on the size of the entrance to the pierced hole depending on power modulation regimes was investigated in this paper.

sted, utgiver, år, opplag, sider
American Institute of Physics (AIP), 2017
HSV kategori
Forskningsprogram
Teknik, Maskinteknik
Identifikatorer
urn:nbn:se:lnu:diva-111349 (URN)10.2351/1.4983260 (DOI)
Tilgjengelig fra: 2022-04-15 Laget: 2022-04-15 Sist oppdatert: 2022-04-25bibliografisk kontrollert
Pocorni, J. K. (2017). Laser cutting and piercing: Experimental and theoretical investigation. (Doctoral dissertation). Luleå University of Technology
Åpne denne publikasjonen i ny fane eller vindu >>Laser cutting and piercing: Experimental and theoretical investigation
2017 (engelsk)Doktoravhandling, med artikler (Annet vitenskapelig)
Abstract [en]

This thesis concerns experimental investigations of laser cutting and piercing, with theoretical and practical discussions of the results. The thesis is made up of an introduction to laser cutting and six scientific Papers. These Papers are linked in such a way that each of them studies a different aspect of laser cutting: process efficiency in Paper I, morphology and melt flow on the laser cut front in Papers II, III and IV and laser piercing in Papers V and VI.

Paper I investigates the effect of material type, material thickness, laser wavelength, and laser power on the efficiency of the cutting process for industrial state-of-the-art CO2 and fibre laser cutting machines. Here the cutting efficiency is defined in its most fundamental terms: as the area of cut edge created per Joule of laser energy.

In Paper II a new experimental technique is presented which has been developed to enable high speed imaging of laser cut fronts produced using standard, commercial parameters. The results presented here suggest that the cut front produced when cutting 10 mm thick medium section stainless steel with a fibre laser and a nitrogen assist gas is covered in humps which themselves are covered in a thin layer of liquid. Paper III presents numerical simulations of the melt flow on a fibre laser ablation-driven processing front during remote fusion cutting, RFC. The simulations were validated with high speed imaging observations of the processing front. The simulation results provide explanations of the main liquid transport mechanisms on the processing front, based on information on the temperature, velocity and pressure fields involved. The results are of fundamental relevance for any process governed by a laser ablation induced front. In Paper IV cutting fronts created by CO2 and fibre lasers in stainless steel at thicknesses between 2 mm and 10 mm have been ‘frozen’ and their geometry has been measured. The resulting three-dimensional shapes have been curve fitted as ninth order polynomials. Various features of the cutting front geometry are discussed, including the lack of correlation of the cut front inclination with either the relevant Brewster angle or the inclination of the striations on the cut edge. In this paper, mathematical descriptions of the cutting fronts are obtained, which can be used as input parameters by any researcher in the field of laser cutting simulations.

Paper V investigates the subject of laser piercing. Before any cut is started the laser needs to pierce the material. In this paper the laser piercing process is investigated using a wide range of laser pulse parameters, for stainless steel using a fibre laser. The results reveal the influence of pulse parameters on pierce time and pierced hole diameter. A high speed imaging camera was used to time the penetration event and to study the laser-material interactions involved in drilling the pierced holes. In Paper VI a ‘dynamic’ or ‘moving beam’, laser piercing technique is introduced for processing 15 mm thick stainless steel. One important aspect of laser piercing is the reliability of the process because industrial laser cutting machines are programmed for the minimum reliable pierce time. In this work a comparison was made between a stationary laser and a laser which moves along a circular trajectory with varying processing speeds. High speed imaging was employed during the piercing process to understand melt behavior inside the pierce hole.

Throughout this work experimental techniques, including advanced high speed imaging, have been used in conjunction with simulations and theoretical analysis, to provide new knowledge for understanding and improving laser beam cutting and its associated piercing process.

sted, utgiver, år, opplag, sider
Luleå University of Technology, 2017. s. 163
Serie
Doctoral thesis / Luleå University of Technology, ISSN 1402-1544
HSV kategori
Forskningsprogram
Teknik, Maskinteknik
Identifikatorer
urn:nbn:se:lnu:diva-111359 (URN)9789175839165 (ISBN)9789175839172 (ISBN)
Opponent
Veileder
Tilgjengelig fra: 2022-04-15 Laget: 2022-04-15 Sist oppdatert: 2022-04-27bibliografisk kontrollert
Pocorni, J. K., Han, S.-W., Cheon, J., Na, S.-J., Kaplan, A. F. .. & Bang, H.-S. (2017). Numerical simulation of laser ablation driven melt waves. Journal of Manufacturing Processes, 30, 303-312
Åpne denne publikasjonen i ny fane eller vindu >>Numerical simulation of laser ablation driven melt waves
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2017 (engelsk)Inngår i: Journal of Manufacturing Processes, ISSN 1526-6125, Vol. 30, s. 303-312Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Numerical simulations on the melt flow down the keyhole front during fibre laser welding are presented here. The calculations confirm the existence of melt waves previously observed by high speed imaging, with velocities ranging between 4 and 10 m/s. The simulations provide spatial and temporal information on the temperature and flow fields, particularly within the melt film volume, which cannot be observed by high speed imaging. The ablation pressure achieves high values around wave-peaks and at the bottom of the front, just before droplets are sheared off. The simulation results provide explanations on the main liquid transport mechanisms within the keyhole based on information on the temperature, velocity and pressure field and on the geometrical front conditions.

sted, utgiver, år, opplag, sider
Elsevier, 2017
HSV kategori
Forskningsprogram
Teknik, Maskinteknik
Identifikatorer
urn:nbn:se:lnu:diva-111350 (URN)10.1016/j.jmapro.2017.09.032 (DOI)2-s2.0-85030668908 (Scopus ID)
Tilgjengelig fra: 2022-04-15 Laget: 2022-04-15 Sist oppdatert: 2022-04-25bibliografisk kontrollert
Powell, J., Petring, D., Pocorni, J. K. & Kaplan, A. F. .. (2016). LIA Guide to High Power Laser Cutting (1ed.). Laser Institute of America (LIA)
Åpne denne publikasjonen i ny fane eller vindu >>LIA Guide to High Power Laser Cutting
2016 (engelsk)Bok (Annet vitenskapelig)
sted, utgiver, år, opplag, sider
Laser Institute of America (LIA), 2016 Opplag: 1
HSV kategori
Forskningsprogram
Teknik, Maskinteknik
Identifikatorer
urn:nbn:se:lnu:diva-111358 (URN)9781940168111 (ISBN)
Tilgjengelig fra: 2022-04-15 Laget: 2022-04-15 Sist oppdatert: 2022-04-25bibliografisk kontrollert
Pocorni, J. K., Petring, D., Powell, J., Deichsel, E. & Kaplan, A. F. H. (2016). The Effect of Laser Type and Power on the Efficiency of Industrial Cutting of Mild and Stainless Steels. Journal of manufacturing science and engineering, 138(3), Article ID 031012.
Åpne denne publikasjonen i ny fane eller vindu >>The Effect of Laser Type and Power on the Efficiency of Industrial Cutting of Mild and Stainless Steels
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2016 (engelsk)Inngår i: Journal of manufacturing science and engineering, ISSN 1087-1357, E-ISSN 1528-8935, Vol. 138, nr 3, artikkel-id 031012Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

This paper investigates the effect of material type, material thickness, laser wavelength, and laser power on the efficiency of the cutting process for industrial state-of-the-art cutting machines. The cutting efficiency is defined in its most basic terms: as the area of cut edge created per Joule of laser energy. This fundamental measure is useful in producing a direct comparison between the efficiency of fiber and CO2 lasers when cutting any material. It is well known that the efficiency of the laser cutting process generally reduces as the material thickness increases, because conductive losses from the cut zone are higher at the lower speeds associated with thicker section material. However, there is an efficiency dip at the thinnest sections. This paper explains this dip in terms of a change in laser–material interaction at high cutting speeds. Fiber lasers have a higher cutting efficiency at thin sections than their CO2 counterparts, but the efficiency of fiber laser cutting falls faster than that of CO2 lasers as the material thickness increases. This is the result of a number of factors including changes in cut zone absorptivity and kerf width. This paper presents phenomenological explanations for the relative cutting efficiencies of fiber lasers and CO2 lasers and the mechanisms affecting these efficiencies for stainless steels (cut with nitrogen) and mild steel (cut with oxygen or nitrogen) over a range of thicknesses. The paper involves a discussion of both theoretical and practical engineering issues.

sted, utgiver, år, opplag, sider
ASME Press, 2016
HSV kategori
Forskningsprogram
Teknik, Maskinteknik
Identifikatorer
urn:nbn:se:lnu:diva-111348 (URN)10.1115/1.4031190 (DOI)2-s2.0-84942927258 (Scopus ID)2015 (Lokal ID)2015 (Arkivnummer)2015 (OAI)
Tilgjengelig fra: 2022-04-15 Laget: 2022-04-15 Sist oppdatert: 2022-04-25bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0001-6261-2019