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Corrugated board converting industry usually uses high-capacity machines but nowadays customers may want even smaller and smaller series. Small series is not anymore economical with punching knifes, because tool cost is quite high compared to cost of one piece. Conventionally cutting of corrugated board is done by mechanical cutting. Making of these punching knifes is time consuming and they also wear out after large number of punches. Laser could be the solution for cutting small series production and also for fast delivery needs. Laser cutting of corrugated board is possible and cut quality is very good. The most important advantage of laser technology is the flexibility: the batch size can be, ten pieces or ten thousand pieces or even one piece. Changing of the cutting geometry is only a question of programming. In this study two different corrugated boards were cut with laser in Lappeenranta Laser Processing Centre (LLPC). The laser equipment used in these studies was 2.7 kW CO2-laser. The cutting speed 100 m/min was achieved with laser power of 700 W when 1 mm thick corrugated board was cut straight with laser. Laser cutting of corrugated boards was possible and laser power was linearly dependent on cutting speed. Smoke formation was fairly abundant. Cut parts smell quite badly right after cutting but odour disappears within few days in open air. Despite of this the quality of cut of corrugated boards with thickness of 1 and 3 mm was good. In this paper is also one small series production batch of 10 pieces was cut with laser and calculations of the economics of cutting were made. Economics are compared to punching knifes and it seems that with this kind of product laser has the advantage.

The spatial and temporal dependence of the electric field amplitude of a terahertz (THz) pulse of several oscillations in the far field near the focal plane of a parabolic mirror was experimentally obtained. During experimentation a spacetime anomaly was discovered in the diffraction patterns. In the wave front of the field the amplitude decreases to zero, and going through this spatial plane, the phase of oscillations changes, while in the integrated intensity, there is a dip in the curve. The results can be applied in pulsed terahertz optics and spectroscopy.

A thermodynamic model was developed to describe the quasi-steady thermal process of a wide thin steel workpiece irradiated by a moving Gaussian laser beam. In this study, an experiment was done on six steels to verify this model. The calculated Ac1 and Ac3 depths and temperature cycles were compared with the measured results. For AISI 4340 steel, correction coefficients were applied to produce an empirical equation for temperature cycles above 488.4°C.

An edge joint 2+2 mm thickness of ordinary austenitic stainless steel sheets was studied in all-position laser welding; flat (PA), vertical-up (PF), vertical-down (PG) and overhead (PE) positions. The penetration depth of the weld was aimed to be at minimum 3.0 mm. The optimal width of the weld was around 2 mm to guarantee adequate tolerances for the weld, but to avoid excessive melting of the edges of the sheets. In addition, the tolerance for the misalignment of the laser beam was tested. The welding procedure was tested with three laser welding methods, including de-focused laser beam, laser beam scanning and twin-spot laser beam welding in order to develop and find means to deploy laser welding robustly and reliably in practical applications. According to the results of welding test trials, the used configuration of twin-spot process seemed to be the most appropriate one among the tested welding methods to guarantee all position welding capability with constant suitable width and depth of weld penetration.

This study investigated the microhardness and microstructure of different steels hardened by a fibre laser. These samples included rolled steel, quenched and tempered steel, annealed alloyed steel and conventionally through-hardened steel. Microhardness (HV0.01) was measured in martensite, pearlite, ferrite and cementite structures at different depths below the laser-irradiated surface. The microhardness test results were compared with the conventional macrohardness (HV5) results. Increase of carbon content caused higher microhardness of martensite, although this influence was weaker than the effect on macrohardness. The grain size of rolled ferritic-pearlitic steels had distinct effect on surface microhardness. The macrohardness of quenched and tempered steel might be markedly influenced by the homogeneity of alloy contents. In-grain indentation showed that cementite is around 150 HV harder than pearlite. High Cr content may increase the microhardness on the surface and up to a depth of about 0.6 mm. Soft annealed alloyed steels achieved high surface hardness but poor hardened depth despite high alloy content. Dispersed granular pearlite did not affect the microhardness of soft annealed steel. The macrohardness of the base material was close to the microhardness of the softer phase structure. The measured microhardness was about 100-250 HV higher than the macrohardness.

Laser welding of polymeric products has been manufactured for more than 20 years. During that time polymer welding has developed a lot. In spite of that, there are still some limitations in applying the process to the industry. Typically welding has been made in lap joint configuration with black and clear parts because of optical properties of polymers. When using ~1 µm lasers, the absorbing and transparent partners are needed. Previously visually transparent materials have been welded in lap joint configuration using infrared absorbers with ~1 µm lasers. Recently new fiber lasers have introduced wavelengths which can have interesting optical properties for polymers. For example, 1.94 µm laser has volume absorption through the whole material thickness on selected polyamide 11 (PA11) polymer material. This makes it possible to use butt joint for welding of polymeric components. When butt joint can be introduced, it will enable more possibilities in using polymer welding in the industry. A joint between two clear components without any additional absorbers can also be introduced with these new wavelengths and it will also decrease the costs and enable new applications when no infrared absorbing additives are needed or accepted. This paper presents results of butt welding of transparent PA11 using TWIST method with 1.94 µm fiber laser. Weld quality is evaluated visually and by comparing weld tensile strength to base material tensile strength.

Laser cutting with multibeam diffraction pattern using an adaptive optics is studied. IR continuous single-mode fiber laser with maximum power of 200 W is applied, with liquid crystal on silicon spatial light modulator (Lcos-SLM), for laser cutting of thin metal sheets. SLM can be used as the adaptive diffractive optical element to modify laser beam profile almost arbitrary. In this paper it is shown that even simple intensity profiles of the cutting beam are enough to enhance the cutting. It was seen that by the spatially intensity modulating the single laser cutting spot into various spots it is possible to enhance the cutting quality and also decrease pressure of the needed assist gas. It was seen that amount of the burr can be decreased and burr free cuts can be made with less protection gas compared to single beam laser cutting.

This study developed a thermodynamic model to investigate the quasi-steady thermal process of a wide thin steel workpiece irradiated with a moving Gaussian laser beam. Equations were established for the temperature distribution and the Ac1 and Ac3 boundaries. The temperature distributions for diverse thicknesses were compared with that for infinite thickness at different laser traverse speed. The lag of the peak temperature relative to the center of laser beam is found to be limited.

Raportissa kuvataan ruostumattoman teräksen jatkojalostamisen tarvetta ja haasteita Suomessa. Lisäksi annetaan ehdotuksia siitä miten koulutuksessa, tiedotuksessa ja ruostumattoman teräksen eri jatkojalostusvaiheissa toimivissa yrityksissä voitaisiin huomioida paremmin ruostumattoman teräksen tarjoamat mahdollisuudet. Raportti perustuu selvityshankkeen Pk-yritysten jaloterästen jatkojalostusmahdollisuudet Kemi-Tornio -alueella ja Suomessa tuloksiin. Vuonna 2010 Suomessa valmistettiin 840 000 tonnia ruostumatonta terästä Outokumpu Stainless Oy:n tehtailla Torniossa. Tehtaan tuotannosta suurin osa meni suoraan vientiin raaka-aineena, levyinä ja rullina 790 000 tonnia. Hankkeen tavoitteena oli etsiä keinoja miten kotimaisen jatkojalostuksen määrää voitaisiin lisätä. Erityisesti tarkastelun kohteena oli ruostumattoman teräksen jatkojalostuksen lisääminen pk-yrityksissä. Selvityksessä tunnistettiin, että Suomessa on hiukan yli kaksisataa pk-yritystä, jotka käyttävät pääsääntöisesti ruostumatonta terästä raaka-aineenaan. Nämä yritykset ovat jakaantuneet ympäri Suomea suurimpien keskittymien sijaitessa Uudellamaalla, Pirkanmaalla ja Varsinais-Suomessa. Maantieteellisesti ja asiakassegmenttien mukaan edustavan joukon haastattelun avulla (31 pk-yritystä) selvitettiin ruostumattoman teräksen jatkojalostukseen liittyviä haasteita ja mahdollisuuksia. Lisäksi neljän päähankkijayrityksen haastattelun avulla tunnistettiin valmistusverkostoon kohdistuvia vaatimuksia. Selvityksen mukaan oli hankalaa löytää suuria kasvunäkymiä ruostumattoman teräksen jatkojalostuksessa. Ruostumattoman teräksen käyttö lisääntyy voimakkaasti erityisesti kehittyvillä markkinoilla, jotka sijaitsevat kaukana Suomesta. Euroopan ruostumattoman teräksen kulutuskohteissa kuten uudisrakentamisessa ja uusissa teollisuuslaitoksissa markkinat eivät juuri kasva. Kuluttajatuotteiden osalta ruostumattoman teräksen hintakilpailu on voimakasta.

This paper investigates the effects of laser power density of a fiber laser on surface transformation hardening of two types of medium-carbon steels. An out-of-focus laser beam produced by a fiber laser system is used to produce an irradiated track on the surface of the samples. The tests use two types of medium-carbon steels with different initial microstructures, including XI5 containing ferrit and pearlite and AC16 composed of tempered martensite. The tests on X 15 show that for each laser power there is an optimum power density that produces the maximum hardness. With increased laser power, the optimal power density for both surface hardness and hardened depth is lowered. For ACI6 tests, the maximum hardness value is not found to be dependent on laser power density. Alloying elements may increase the hardened depth. Slight surface melting may facilitate the hardening process and increase the surface hardness. The hardened depth is generally increased with higher laser power and/or laser power density. Compared with other types of lasers, fiber laser is a competitive tool in hardening of medium-carbon steels.