High Power Density Laser Build-Up Welding with CNC Precision

Laser treatment has become a popular method for resolving peri-implantitis, but the full range of its effects on implant surfaces is unknown. The purpose of the present investigation was to analyze the influence of different clinically applicable erbium:yttrium-aluminum-garnet (Er:YAG), carbon dioxide (CO2), and diode laser parameters on titanium surfaces that were either polished or sandblasted, large-grit, acid-etched (SLA). Six polished and six SLA titanium disks were irradiated at nine different power settings (n = 54 polished, 54 SLA) with Er:YAG, CO2, or diode lasers. The CO2 and diode lasers were used in continuous wave mode, and the Er:YAG laser was used in a pulsed manner. The surface of each disk was analyzed by scanning electron microscopy and confocal white light microscopy. Each disk was irradiated on six circular areas of 5 mm in diameter with the same specific laser setting for 10 seconds. Within the chosen parameters, the CO2 and diode laser did not cause any visible surface alterations on either the polished or SLA disks. In contrast, both polished and SLA disks showed surface alterations when irradiated with the pulsed Er:YAG laser. The SLA surfaces showed alteration after 10 seconds of irradiation with Er:YAG laser at 300 mJ/10 Hz. The surfaces of the polished disks did not show alteration with the Er:YAG laser until they were irradiated at the higher energy of 500 mJ/10 Hz for 10 seconds. The results of confocal white light microscopy were in agreement with scanning electron micrographs. In contrast to continuous-wave diode and CO2 laser irradiation, pulsed Er:YAG laser irradiation caused distinct alterations with power settings beyond 300 mJ/10 Hz on the SLA surface and 500 mJ/10 Hz on the polished surface. Thus, it is only safe to use the Er:YAG laser for implant surface irradiation with settings no higher than 300 or 500 mJ/10 Hz.

High power lasers, including CO2 laser, Nd:YAG laser, Excimer laser, Diode laser, LD pumped YAG laser, LD pumped Disk laser, LD pumped Fiber laser and Femto second laser, are now used as a modern tool for industries as well as a computer alike in the 4th wave of modernization. Lasers are currently used for welding, cutting, drilling, cladding, direct fabrication, marking, cleaning, micro-machining peening and forming of materials in modernized factories. The joining speed (= product of welding speed and penetration depth) of 45,000mm2/min for steel sheet can be obtained by a 10kW Yb: fiber laser and is that of 50kW electron beam welding, which require the vacuum chamber. As a result of large numbers of research and developments the Advanced Laser Integrated Manufacturing System (ALIMS) using high power diode lasers has been developed and used for modernization in many industrialized countries. The laser materials processing is now penetrated as a machining tool into many industries. In the present paper, an advanced laser integrated manufacturing systems and its applications to industries such as automotive, electronics, ship building and steel making industry are introduced. In addition, development of an advanced laser integrated manufacturing system using a 2kW fiber laser for welding a car panel and “Laser Roll Welding” system for dissimilar metal joints such as mild steel/high strength steel to aluminium alloys, titanium to aluminium and steel to titanium, is described for modernization of industries. It will be a magnificent for the industries. And the 4th wave of modernization and opto-mechatronics will be promoted more by laser/photon technology in the future.

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The use of laser energy to weld biological tissues and produce sutureless anasto mosis has its advantages over conventional silk-sutured anastomosis since it was reported in small vessels[1] and fallopian tubes[2], in the late 1970s. Since then, more investigators have welded a larger variety of tissues[3-13] and have expanded its application to welding trials of ent ertomies of rabbit and rat small intestine[14-17]. Sauer et al[18] reported results from Nd: YAG laser in reconstruction of end-to-end wel ding in rabbit small intestine. Recently, controlled temperature during YAG and argon laser-assisted welding of entertomies of rabbit and rat was implemented to eliminate exponential increases in the rate of denaturation associated with rapidly increasing temperature[19,20]. Yet there was no report of sutureless end-to-end bowel anastomosis using low-power CO2 laser. This is a repor t of a circumferential end-to-end laser welding bowel anastomosis in rabbit by using 3 different CO2 laser powers to explore the feasibility of CO2 laser welding of a circumferential intestinal tissue and to determine the optimal la ser-welding parameter. Then the appropriate CO2 laser power was chosen to weld bowels in rabbit and its long-term healing effect was evaluated.

Melting characteristics, porosity formation tendency and presence of AIN film in aluminum alloy as well as N content, microstructural characteristics and cracking tendency in austenitic stainless steel were investigated and compared by bead-on-plate welding A5083 alloy and Type 304 steel with CO2 and YAG lasers in nitrogen shielding gas. Melting characteristics and porosity formation tendency of these materials were not so much different at about 3 to 4 kW between CO2 and YAG lasers. AIN films were formed in CO2 laser weld beads of A5083 alloy but were not present in YAG laser weld metals. The N contents absorbed in Type 304 weld fusion zones were larger under any welding conditions with CO2 laser than with YAG laser. Consequently, in the case of some CO2 laser weld metals in Type 304 steel, solidification process varied from primary delta-ferrite to primary austenite, segregation of P and S increased along grain boundaries, and accordingly solidification cracks occurred along the boundaries of fully austenitic microstructural grains. It was concluded that a great effect of nitrogen on weldability of aluminum alloy and stainless steel was noted more remarkably in CO2 laser weld fusion zones than in YAG laser ones. It may be attributed to the N plasma formation leading to active N generation during CO2 laser welding.Melting characteristics, porosity formation tendency and presence of AIN film in aluminum alloy as well as N content, microstructural characteristics and cracking tendency in austenitic stainless steel were investigated and compared by bead-on-plate welding A5083 alloy and Type 304 steel with CO2 and YAG lasers in nitrogen shielding gas. Melting characteristics and porosity formation tendency of these materials were not so much different at about 3 to 4 kW between CO2 and YAG lasers. AIN films were formed in CO2 laser weld beads of A5083 alloy but were not present in YAG laser weld metals. The N contents absorbed in Type 304 weld fusion zones were larger under any welding conditions with CO2 laser than with YAG laser. Consequently, in the case of some CO2 laser weld metals in Type 304 steel, solidification process varied from primary delta-ferrite to primary austenite, segregation of P and S increased along grain boundaries, and accordingly solidification cracks occurred along the boundaries of fully aust...

This study aims to contribute to a better understanding of the cut surface quality difference between a laser with 1 µm wavelength (fiber or disc laser) and a 10.6 µm CO2 laser for laser fusion cutting of thick steel plates. Laser cutting of SUS304 stainless steel with thicknesses of 3, 5 and 8 mm was performed with a multimode fiber laser and a CO2 laser with the same power and comparative beam focusing characteristics. As already reported in the literature, the fiber laser exhibits worse surface quality for thicknesses with 5 and 8 mm. The result shows that the degradation of the surface roughness occurs when the cutting velocity becomes smaller than 1.5 m/min. We measured also the inclination angle α of the kerf front and it is shown that this range of cutting velocity corresponds to α < 3 degrees. This supports results of our analyses that stronger disturbance of melt flow or less absorption on kerf sides, which are induced by the small angle α, can be the reason for the laser wavelength dependence of the cut surface quality.

Background and objective: The objective of this studywas to evaluate the bond strength between a composite resin anddental hard tissues, which have been previously irradiated with anEr:YAG (2.94 μm) or CO2 (9.6 μm) laser. Materials andmethods: A total of 156 bovine teeth were divided into 6 groups:Group 1 – Enamel control: acid etched enamel (Single Bond); Group2 – Dentin control: acid etched dentin (Single Bond); Group 3 –Irradiated enamel (CO2 laser – 3 W) followed by acid etching;Group 4 – Irradiated dentin (CO2 laser – 3 W) followed byacid etching; Group 5 – Irradiated enamel (Er:YAG laser –0.16 W) followed by acid etching; Group 6 – Irradiated dentin(Er:YAG laser – 0.16 W) followed by acid etching. Results:Treatment only with acid etching and also the Er:YAG laserirradiation followed by acid etching showed the highest bondstrength value while the CO2 laser irradiation followed by acidetching treatment produces the lowest bond strength values in bothtissues. Conclusion: Acid etching of non-irradiated and Erbium YAGlaser irradiated tissues produces better adhesion than acidetching of CO2 laser irradiated surfaces.

Objective: This in vitro study evaluated the effectiveness of three laser systems—diode, CO2, and Er:YAG—for debonding composite attachments used in aligner orthodontic therapy. Materials and Methods: Fifty extracted human premolars with composite attachments were divided into five groups (n = 10): control, RT (rotary tools), diode laser (980 nm, irradiance was 4811 W/cm2), CO2 laser (10.6 µm, irradiance 1531 W/cm2), and Er:YAG laser (2940 nm, irradiance 471.7 W/cm2). Shear bond strength (SBS) testing measured debonding forces. Enamel surface changes were evaluated using micro-CT, optical profilometry, and stereomicroscopy. The Adhesive Remnant Index (ARI) assessed residual bonding material. Results: Laser treatment increased enamel roughness (p < 0.05). Er:YAG laser caused the highest roughness (Sa = 2.03 µm) and up to 0.17 mm enamel loss but left minimal adhesive remnants and no fractures. Diode laser preserved surface smoothness with moderate bond weakening. CO2 laser had intermediate effects. RT showed the highest SBS but resulted in greater enamel alteration. SBS was significantly reduced in the laser groups, lowest for Er:YAG (81.7 ± 45.5 MPa vs. control 196.2 ± 75.3 MPa). ARI indicated better adhesive removal in the laser-treated groups, with Er:YAG showing the highest percentage of clean enamel surfaces (67% vs. 25%). Conclusions: Er:YAG demonstrated the best balance between effective debonding and enamel preservation. Diode and CO2 lasers also offer viable alternatives to rotary tools. Further clinical studies are recommended.

Lasers have been in use for material processing for decades as a flexible tool for different processes i.e. welding, cutting, drilling, surface modifications etc. Laser material processing offers a number of advantages over other processing technologies, i.e. high processing speeds, low heat input (minimal disruption to the parent material and coatings), low distortion of the parts, better cosmetic appearance and high flexibility. In the past, lamp pumped Nd: YAG lasers have been widely been used for a number micro and macro applications. Today, however, the parameter range of solid state lasers has increased significantly, especially after the emerging of fiber and disk lasers.The choice of a laser source for a specific application is no longer straightforward and obvious. Laser users are now faced with additional questions of laser beam quality and brightness. The main advantage of high beam quality is that the laser beam can be transported via a small diameter optical fiber, which translates to a small spot size at the workpiece.Laser sources with better beam quality are being made available at increasing power levels. However, choosing the optimum laser for an application may not be simply the selection of the highest beam quality at the required power level. This paper addresses this important issue — how the laser beam quality of solid state lasers affects the laser material processing performances by comparing welding and cutting data for thin and thick section of materials.

Laser material processing demonstrated its significance in many areas such as microelectronics, data storage, photonics and nanotechnology, since versatile laser sources provide flexible and unique energy source for precise control of material processing. With current laser technology, a short wavelength down to X-ray range and a short pulse duration down to femtosecond range can be achieved. The extreme conditions created by laser irradiation have provided strong impact on material research. To achieve nanoscale laser material machining and processing, we need to overcome the diffraction limit of the laser wavelengths. Recently, different approaches have been explored to overcome the diffraction limit and to achieve feature sizes down to 10 nm order, way beyond the diffraction limits. This paper will provide an overview in the areas of laser-based nanoscale machining and processing, including the authorís own research experience on laser-assisted scanning probe microscope, superfocusing by optical resonance in spherical particles, laser nanoimprinting, laser synthesis of quantum dots, laser annealing of ultrashow pn junctions, nanometer-order film thickness detection using rotational Raman spectroscopy, and laser cleaning of nanoparticles.

Investigation on disk and CO2 laser beam fusion cutting differences based on power balance equation

Experimental and Numerical Investigations of Laser Beam Welding with an Ultra-high Brightness Direct-diode Laser

Fiber lasers combine the advantages of solid-state lasers and diode lasers, such as high beam quality and high efficiency. Examinations concerning the micro-welding process were carried out with a 9 Watt CW fiber laser. The wavelength of 1100 nanometers is similar to Nd:YAG radiation, which is established in material processing. Due to the core diameter of only 8 microns and a numerical aperture of 0.08 of the collimated beam, focussing to less than 8 microns is possible. Therefore, power densities of more than 107 W/cm2 are obtainable, which make processes like marking, cutting, welding or soldering of metals possible [2, 3],Investigations concentrated on the welding process of metal foils with a thickness of 25 to 50 microns. Stainless steel and mild steel were overlap-welded with argon and nitrogen as shielding gas. Foils with a thickness of 25μm, for example, were successfully welded at a speed of about 250 millimeters per minute. The stability of the process is extremely influenced by the welding speed and the shielding gas flow which affects the thermal conditions in the welding zone. In particular, slight alterations of the gas flow have much higher effects on the process than it is known from high power welding.Fiber lasers combine the advantages of solid-state lasers and diode lasers, such as high beam quality and high efficiency. Examinations concerning the micro-welding process were carried out with a 9 Watt CW fiber laser. The wavelength of 1100 nanometers is similar to Nd:YAG radiation, which is established in material processing. Due to the core diameter of only 8 microns and a numerical aperture of 0.08 of the collimated beam, focussing to less than 8 microns is possible. Therefore, power densities of more than 107 W/cm2 are obtainable, which make processes like marking, cutting, welding or soldering of metals possible [2, 3],Investigations concentrated on the welding process of metal foils with a thickness of 25 to 50 microns. Stainless steel and mild steel were overlap-welded with argon and nitrogen as shielding gas. Foils with a thickness of 25μm, for example, were successfully welded at a speed of about 250 millimeters per minute. The stability of the process is extremely influenced by the welding spe...

The outcome of root canal treatment is based on efficient disinfection of the root canal system and prevention of reinfection. Current chemomechanical cleaning methods do not always achieve these goals, and insufficient root canal disinfection is the main reason for endodontic failure. Due to high energy content and specific characteristics of laser light, laser treatment has been proposed for cleaning and disinfecting the root canal system. This paper reviews the literature covering the effect of Er:YAG, Er,Cr:YSGG, Nd:YAG and diode laser on the root canal wall in the removal of smear layer and against intracanal bacteria. Recently, the use of laser energy to induce cavitation and acoustic streaming of intracanal irrigants has been investigated. Based on recent literature, it can be concluded that lasers have bactericidal effects. However, they still cannot replace sodium hypochlorite and should be considered as an adjunct to the current chemical root canal disinfection protocols. Certain lasers can help in removing the smear layer and debris and can modify the morphology of the root canal wall. Unfortunately, there have not been enough randomized clinical studies evaluating endodontic treatment outcome following the use of laser.

The complexity of laser material processing can be greatly reduced using computer-generated phase reflection holographic scanners. These scanners direct and focus the beam of a carbon dioxide laser into a spot on the workpiece and then translate this spot over some general 2-D pattern as the scanner undergoes a simple 1-D motion. Procedures for constructing these scanners are presented, and the first-order aberrations introduced by them are analyzed. The primary aberrations cause the diffracted beam to focus to an astigmatic spot on the work surface. The severity of the astigmatism is proportional to the scan rate, scan angle, and f/number. A technique is presented in which the design of the scanner is adjusted so that the astigmatic image is aligned with the scan direction. The resolution perpendicular to the scan direction is the same as that of a scanner without aberrations of the same f/number. Materials processed using these scanners are presented to show their capabilities for carbon dioxide laser material processing. Power densities on the order of 10(6)/cm(2) can be readily obtained using the proposed technique.