Hitsaustoiminnan käynnistäminen pk-alihankintakonepajassa

Tämä diplomityö on tehty HT Laser Oy:n Vieremän tehtaan hitsaustoiminnan käynnistämisen yhteydessä. Diplomityön tavoitteena oli hitsaustoiminnan käynnistämisen kustannusten minimointi ja hitsattavien tuotteiden myynti- ja valmistusprosessin luominen. Työn teoriaosassa on esitelty hitsauslaitteistolle asetettavia vaatimuksia, hitsauskustannuksiin vaikuttavia tekijöitä, tuotantojärjestelmiä, tuotannon ohjausmenetelmiä, laadunhallintaa, henkilöstöasioita, osavalmistusta, hitsauksen hinnoittelua ja tilauskäsittelyä. Ensisijaisesti työssä on tavoiteltu sujuvan ja tuloksellisen tilaus/tarjouskäsittelyprosessin luomista. Tämä on nähty edellytyksenä ongelmattomalle tuotannolle ja hyvälle toimitusvarmuudelle. Työssä on luotu malli tarjousvaiheessa läpikäytävälle esikatselmukselle, jota on esitelty kahden case -esimerkin avulla. Case -esimerkeissä on käsitelty myös tuotteiden valmistukseen ja hinnoitteluun liittyviä asioita ja ongelmia sekä näiden ratkaisuja.

Control methods for arc welding power supplies

Welding is one of the most important process of modern industry. Welding technology is used in the manufacture and repair a wide variety of products from different metals and alloys. In this thesis the different aspects of arc welding were discussed, such as stability and control of welding arc, power supplies for arc welding (especially the welding inverters because it is the most modern welding power source). All parameters of power source have influence on the arc parameters and its by-turn influence on quality. The ways of control for arc welding inverter power sources have been considered. Calculations and modeling in Matlab/Simulink were done for PI control method. All parameters of power source have influence on the arc parameters and its by-turn influence on quality.

Superconducting properties and their enhancement in ReBa2Cu3O7-delta (RE = Y and Gd) films prepared by pulsed laser deposition

Due to font problem on the tilte field the titlte of the thesis is corrected here. The title of the thesis is: Superconducting properties and their enhancement in ReBa₂Cu₃O₇-delta (RE = Y and Gd) films prepared by pulsed laser deposition

Performance of high power fibre laser cutting of thick-section steel and mediumsection aluminium

Cutting of thick section stainless steel and mild steel, and medium section aluminium using the high power ytterbium fibre laser has been experimentally investigated in this study. Theoretical models of the laser power requirement for cutting of a metal workpiece and the melt removal rate were also developed. The calculated laser power requirement was correlated to the laser power used for the cutting of 10 mm stainless steel workpiece and 15 mm mild steel workpiece using the ytterbium fibre laser and the CO2 laser. Nitrogen assist gas was used for cutting of stainless steel and oxygen was used for mild steel cutting. It was found that the incident laser power required for cutting at a given cutting speed was lower for fibre laser cutting than for CO2 laser cutting indicating a higher absorptivity of the fibre laser beam by the workpiece and higher melting efficiency for the fibre laser beam than for the CO2 laser beam. The difficulty in achieving an efficient melt removal during high speed cutting of the 15 mmmild steel workpiece with oxygen assist gas using the ytterbium fibre laser can be attributed to the high melting efficiency of the ytterbium fibre laser. The calculated melt flow velocity and melt film thickness correlated well with the location of the boundary layer separation point on the 10 mm stainless steel cut edges. An increase in the melt film thickness caused by deceleration of the melt particles in the boundary layer by the viscous shear forces results in the flow separation. The melt flow velocity increases with an increase in assist gas pressure and cut kerf width resulting in a reduction in the melt film thickness and the boundary layer separation point moves closer to the bottom cut edge. The cut edge quality was examined by visual inspection of the cut samples and measurement of the cut kerf width, boundary layer separation point, cut edge squareness (perpendicularity) deviation, and cut edge surface roughness as output quality factors. Different regions of cut edge quality in 10 mm stainless steel and 4 mm aluminium workpieces were defined for different combinations of cutting speed and laserpower.Optimization of processing parameters for a high cut edge quality in 10 mmstainless steel was demonstrated

Investigation of Oxygen Cutting Process in Solid-State Welding

The oxygen cutting is a thermal cutting process, in which metal is heated locally up to its ignition temperature and burnt off by oxygen blast. Oxygen cutting can be used to remove upset metal of a hollow bar occurred due to solid-state welding process. The main goal of this research was to establish a connection between oxygen blasts and mass of metal removed and relate findings to production to suggest improvements to the current process. This master´s thesis describes the designing and building of a test rig for oxygen blowing measurements. It also contains all executed tests and test results, which were carried out. There are different cutting parameters which were studied as well as their effect on cutting process. The oxygen cutting process, used in solid-state welding process, can be improved by the test results.

Suunnittelun mahdollisuudet alumiiniveneen rungon valmistuskustannusten optimointiin mitoitusdirektiivi huomioiden

Tässä diplomityössä tutkittiin valmistuksellisia ja rakenteellisia mahdollisuuksia alumiiniveneen rungon valmistuskustannusten optimointiin vallitseva runkomitoitusdirektiivi huomioiden. Varsinaista kustannussäästötavoitetta työlle ei määritetty, mutta tavoitteena oli selvittää runkokonstruktion kustannusten painopisteiden mukaisesti kehityskohteet ja uusi kehitetty runkokonstruktio, joka täyttää mitoitusdirektiivin vaatimukset. Nykyistä ja kehitettyä runkokonstruktiota verrataan kustannusten sekä valmistettavuuden kannalta ja tehdään johtopäätökset. Kehityskohteiden löytämisessä sovellettiin valmistus- ja kokoonpanoystävällisen suunnittelun DFM(A)-periaatteita ja teoriaa, jotka esiteltiin työn teoriaosuudessa. Valmistuskustannusten määrittämisen tueksi teoriaosuudessa esiteltiin hitsauksen ja osavalmistuksen (laserleikkaus, särmäys) kustannusmallit, joita hyödynnettiin soveltuvin osin kustannuslaskennassa. Merkittävänä osana selvitystyötä oli myös SFS-EN ISO 12215-5-(6) runkomitoitusstandardin tulkitseminen ja referointi työn kannalta merkittäviin osa - alueisiin. Nykyisen runkokonstruktion kustannusanalyysin ja valmistettavuusarvion pohjalta päädyttiin rakenteellisiin ja valmistuksellisiin kehitystoimenpiteisiin, jotka täyttävät runkomitoitusdirektiivin rakenteelliset vaatimukset. Rakenteelliset toimenpiteet käsittivät mm. materiaalivahvuuksien, jäykisterakenteen ja osamäärän optimointia. Valmistukselliset toimenpiteet liittyivät mm. hitsauksen tuottavuuden tehostamiseen ja sen kustannusvaikutuksiin. Rakenteellisilla kehitystoimenpiteillä olisi mahdollista saavuttaa noin 6 % säästö ja valmistusmenetelmien kehittämisellä noin 17 % säästö valmistuskustannuksista.

The Productivity, Economy and Quality of Welding in the Different Geographical Areas of China - Today and in the Future

This master’s thesis gives out the real situation of the China welding industry and factories nowadays in different geographical areas, in order to inform the Finnish companies who have the willing to find a Chinese welding subcontractor a proper and correct selection concept by analyzing and supplying the information of different scale and form welding factories in different Chinese areas. The first section of this thesis gives out the general situation about the co-operation between China and Finland in the welding industry, also includes the general introduction of the Chinese welding industry. The second section gives out the geographical compartmentalization result of Chinese welding industry, which is where and how many areas will be studied in this thesis. The main body of this thesis is the real information of welding productivity, welding cost, and welding quality in China. All the information was collected from real factories in China by the author. The last section of this thesis is the improvements to the Chinese welding factories that have the willing to become a subcontractor, and the suggestions to the Finnish companies who may find a Chinese welding factory as their subcontractor in future.

Spectrometrical Monitoring of Laser Sintering Process of Ceramic Material

This thesis is done as a part of project called FuncMama that is a project between Technical Research Centre of Finland (VTT), Oulu University (OY), Lappeenranta University of Technology (LUT) and Finnish industrial partners. Main goal of the project is to manufacture electric and mechanical components from mixed materials using laser sintering. Aim of this study was to create laser sintered pieces from ceramic material and monitor the sintering event by using spectrometer. Spectrometer is a device which is capable to record intensity of different wavelengths in relation with time. In this study the monitoring of laser sintering was captured with the equipment which consists of Ocean Optics spectrometer, optical fiber and optical lens (detector head). Light from the sintering process hit first to the lens system which guides the light in to the optical fibre. Optical fibre transmits the light from the sintering process to the spectrometer where wavelengths intensity level information is detected. The optical lens of the spectrometer was rigidly set and did not move along with the laser beam. Data which was collected with spectrometer from the laser sintering process was converted with Excel spreadsheet program for result’s evaluation. Laser equipment used was IPG Photonics pulse fibre laser. Laser parameters were kept mainly constant during experimental part and only sintering speed was changed. That way it was possible to find differences in the monitoring results without fear of too many parameters mixing together and affecting to the conclusions. Parts which were sintered had one layer and size of 5 x 5 mm. Material was CT2000 – tape manufactured by Heraeus which was later on post processed to powder. Monitoring of different sintering speeds was tested by using CT2000 reference powder. Moreover tests how different materials effect to the process monitoring were done by adding foreign powder Du Pont 951 which had suffered in re-grinding and which was more reactive than CT2000. By adding foreign material it simulates situation where two materials are accidently mixed together and it was studied if that can be seen with the spectrometer. It was concluded in this study that with the spectrometer it is possible to detect changes between different laser sintering speeds. When the sintering speed is lowered the intensity level of light is higher from the process. This is a result of higher temperature at the sintering spot and that can be noticed with the spectrometer. That indicates it could be possible to use spectrometer as a tool for process observation and support the idea of having system that can help setting up the process parameter window. Also important conclusion was how well the adding of foreign material could be seen with the spectrometer. When second material was added a significant intensity level raise could be noticed in that part where foreign material was mixed. That indicates it is possible to see if there are any variations in the material or if there are more materials mixed together. Spectrometric monitoring of laser sintering could be useful tool for process window observation and temperature controlling of the sintering process. For example if the process window for specific material is experimentally determined to get wanted properties and satisfying sintering speed. It is possible if the data is constantly recorded that the results can show faults in the part texture between layers. Changes between the monitoring data and the experimentally determined values can then indicate changes in the material being generated by material faults or by wrong process parameters. The results of this study show that spectrometer could be one possible tool for monitoring. But to get in that point where this all can be made possible much more researching is needed.

Feasibility study of metal to polymer hybrid joining

The increasing demand for lightweight components has led to a huge exploitation of non-metallic materials such as polymers, fibers and elastomers in industrial and manufacturing processes. Recent trends towards cost effectiveness, weight reduction and production flexibility in industrial production and manufacturing processes has led to a growing interest in hybrid components where two or more dissimilar materials coexist to achieving specifically optimized characteristics. The importance of this research is to serve as a bridge to understanding the theories behind various joining techniques and the adaptation of the process for metal to polymer hybrid joints. Moreso, it helps companies to select the most productive and yet economical joining process for realization of lightweight metal to polymer hybrid components. This thesis is a literature review analyzing various materials that has been published on various joining methods for metal to polymer hybrid joints on the feasibility and eventual realization of the joint between these dissimilar materials. This study is aimed at theoretically evaluating the feasibility of joining processes between metal and plastic components by exploiting exhaustively joining and welding sources.

Investigation of the two-photon induced fluorescence in Rb vapour excited by Ti:Sapphire femtosecond laser pulses

In this work we report the observation of the blue visible fluorescence at 420 nm in rubidium vapour as a result of two-photon absorption excited by femtosecond laser pulses 790 nm. After experimental investigation of the spa-tial and spectral characteristics of the obtained emission we can claim that mechanism of this coherent fluorescence at 420 nm was not caused by ampli-fied spontaneous emission, but represents the nondegenerate four-wave mixing. As a probable outcome of this investigation an opportunity of creation an ultrafast all-optical switcher might appear.

Welding development of crane main girder

Konecranes Corporation manufactures huge steel structures in 16 factories worldwide, in which the environment and quality varies. The company has a desire to achieve the same weld quality in each factory, regardless of the manufacturing place. The main subject of this master’s thesis was to develop the present box girder crane welding process, submerged arc welding and especially the fillet welding. Throughput time and manufacturing costs can be decreased by welding the full penetration fillet weld without a bevel, changing present groove types for more appropriate ones and by achieving the desired weld quality on the first time. Welding experiments of longitudinal fillet welding were made according to the present challenges, which the manufacturing process is facing. In longitudinal fillet welding tests the main focus was to achieve full penetration fillet weld for 6, 8 and 10 millimeters thick web plates with single and twin wire submerged arc welding. Full penetration was achieved with all the material thicknesses, both with single and twin wire submerged arc welding processes. The main problem concerning the weld was undercutting and shape of the weld bead. The question about insufficiency of presently used power sources with twin wire was risen up during testing, due to the thicknesses that require high welding current. Bigger power source is required when box girders are welded nonstop, if twin wire is used. For single wire process the penetration was achieved with significantly less amperage than with twin wire.