Tsuyoshi Tokunaga

Forming characteristics of thin metal plate with diode laser beam

Diode laser beam of 20 W is applied to bend forming of thin metal plates. Bending characteristics are discussed on the basis of the experimental results for various bending conditions such as laser power, beam diameter, plate thickness, position of laser irradiation and so forth; furthermore, several kinds of metals are adopted as targets, i.e., AISI 304, iron, copper, molybdenum, nickel and aluminum. The bending angles strongly depend on the kind of materials; in particular, materials with low thermal conductivity bends with large angles. This seems to be caused by the high temperature rise due to low thermal diffusion. AISI 304 plates bend both away from and toward the beam under the same experimental conditions. The beam diameter has a strong effect on the bending direction; in case of forming of AISI 304 plate of 0.1 mm thickness, it bends away from the beam with higher possibility with larger diameter beam.Diode laser beam of 20 W is applied to bend forming of thin metal plates. Bending characteristics are discussed on the basis of the experimental results for various bending conditions such as laser power, beam diameter, plate thickness, position of laser irradiation and so forth; furthermore, several kinds of metals are adopted as targets, i.e., AISI 304, iron, copper, molybdenum, nickel and aluminum. The bending angles strongly depend on the kind of materials; in particular, materials with low thermal conductivity bends with large angles. This seems to be caused by the high temperature rise due to low thermal diffusion. AISI 304 plates bend both away from and toward the beam under the same experimental conditions. The beam diameter has a strong effect on the bending direction; in case of forming of AISI 304 plate of 0.1 mm thickness, it bends away from the beam with higher possibility with larger diameter beam.

Liquid pressure varifocus lens for YAG laser processing

A varifocus lens by liquid pressure has been developed to change the focal length from a concave to a convex shape by adjusting the liquid pressure. It consists of a polymer film, an acrylic plate, and liquid and it is filled up with the liquid in its cavity. The deformation of the refraction surface of the lens is analyzed theoretically. An experiment by He-Ne laser is performed with a plano-convex type lens. The dynamic range of the focal length of the convex lens is from 50 mm to 250mm. The application for a YAG laser with 1.06μm of wavelength is demonstrated experimentally. The focus was adjusted along the material surface without moving the optical element. As a result, the control of the beam spot diameter is succeeded. Finally, the laser processing is demonstrated to manufacture Fe compressed powder sheets. Its melting marks along a focus change are formed with a minimum width of 100μm.

Forming of thin plate with diode laser

Diode laser is applied to bend forming of thin stainless steel plate (AISI 304); the power is 10 W with the spot size of about 1 mm and the plate thickness is 0.1 mm. The bending characteristics depend on the conditions of the plate material, scanning speed of the beam, pre-bending and so forth. At low speed, there is possibility of bending both toward and away from the beam. The occurrence probability of bending away from the beam is about 0.1 to 0.3. As to a plate with pre-bending, the irradiation direction of the beam on the plate does not affect the bending direction; the plate always bends toward the same direction of the prebending even if the beam is supplied on the opposite surface. Furthermore, this is effective within some deviation distance from the ridge of the bent plane; the distance depends on the beam spot size. The characteristics are very useful for making complicated structure of thin plate; various shapes are formed and some of them are demonstrated.Diode laser is applied to bend forming of thin stainless steel plate (AISI 304); the power is 10 W with the spot size of about 1 mm and the plate thickness is 0.1 mm. The bending characteristics depend on the conditions of the plate material, scanning speed of the beam, pre-bending and so forth. At low speed, there is possibility of bending both toward and away from the beam. The occurrence probability of bending away from the beam is about 0.1 to 0.3. As to a plate with pre-bending, the irradiation direction of the beam on the plate does not affect the bending direction; the plate always bends toward the same direction of the prebending even if the beam is supplied on the opposite surface. Furthermore, this is effective within some deviation distance from the ridge of the bent plane; the distance depends on the beam spot size. The characteristics are very useful for making complicated structure of thin plate; various shapes are formed and some of them are demonstrated.

Liquid pressure varifocus lens using a fibrous actuator

A liquid pressure varifocus lens has been developed that employs a fibrous actuator which contracts on application of a current or on heating. The focal length of the convex lens can be varied continuously between 90 mm to 300 mm. The shape of the lens changes smoothly and the construction of the lens is extremely simply. It requires a low electric power to drive it. In this study, the optical characteristics and the response time of the liquid pressure varifocus lens were measured. The time constant of the fibrous actuator was 1.0 s for the rise time when electric power was initially supplied. A fibrous actuator having a length of 370 mm was used, and a voltage of 9.5 V was applied.

Laser bending of thin metal plate: Effects of two beams and single line beam on bending characteristics based on buckling mode

Two diode laser beams are applied to laser forming of stainless steel of about 0.1 mm in thickness. Beam diameter is about 1 mm so that bending is due to buckling mechanism. In this mechanism, the bending direction is not fixed so that the target is bent toward or away the laser beam. In the present study, two spot beams or a line beam are used to control the bending direction for the buckling mode bending; the laser beams are focused into two spots on the surface of a target plate, or the laser beam is focused in a line shape on the target. The experimental results show that the bending direction can be controlled under some conditions even in the buckling mode bending of thin plates with large diameter beams.Two diode laser beams are applied to laser forming of stainless steel of about 0.1 mm in thickness. Beam diameter is about 1 mm so that bending is due to buckling mechanism. In this mechanism, the bending direction is not fixed so that the target is bent toward or away the laser beam. In the present study, two spot beams or a line beam are used to control the bending direction for the buckling mode bending; the laser beams are focused into two spots on the surface of a target plate, or the laser beam is focused in a line shape on the target. The experimental results show that the bending direction can be controlled under some conditions even in the buckling mode bending of thin plates with large diameter beams.

Three - dimensional prototyping from metallic powder: Melting by cw/pulsed Nd:YAG laser with electric heater

The present paper deals with a new method of RP from metal powders. The process is divided into two steps. First, metal powders are sintered by CW laser with the aid of an electric heater. This can reduce the warp generation in the sintered plate. Next, the sintered objects are united into one by pulsed laser melting and welding. Examples of formed objects are exhibited.The present paper deals with a new method of RP from metal powders. The process is divided into two steps. First, metal powders are sintered by CW laser with the aid of an electric heater. This can reduce the warp generation in the sintered plate. Next, the sintered objects are united into one by pulsed laser melting and welding. Examples of formed objects are exhibited.

Spinning of thin metal plate with diode laser

Spinning of stainless steel (AISI 304), magnesium alloy (ASTM AZ31B) and titanium alloy (Ti-6Al-4V) plates is tried with diode laser. The sizes of the plate are 0.3, 0.4 and 0.5 mm in thickness and 70 and 100 mm in diameter. The laser beams of maximum power of 140 W are irradiated on the portions of 1, 2, 3 mm away from the periphery of disk plates. AISI 304 plate of 0.3 mm thick can be formed into a head plate of a diameter of 67 mm with a height 2.0 mm; the bending angle is about 90 degrees. It is difficult to form titanium alloy plates. Magnesium alloy plates are easily formed; however, the surface layer is melted. The spinning characteristics are discussed for AISI 304.Spinning of stainless steel (AISI 304), magnesium alloy (ASTM AZ31B) and titanium alloy (Ti-6Al-4V) plates is tried with diode laser. The sizes of the plate are 0.3, 0.4 and 0.5 mm in thickness and 70 and 100 mm in diameter. The laser beams of maximum power of 140 W are irradiated on the portions of 1, 2, 3 mm away from the periphery of disk plates. AISI 304 plate of 0.3 mm thick can be formed into a head plate of a diameter of 67 mm with a height 2.0 mm; the bending angle is about 90 degrees. It is difficult to form titanium alloy plates. Magnesium alloy plates are easily formed; however, the surface layer is melted. The spinning characteristics are discussed for AISI 304.

Beam shaping optics for YAG laser by using a CNC lathe

A method for a beam shaping optics is proposed to convert a laser beam profile into required intensity distribution. A beam shaper with aspherical surface is calculated by Snells law converted from measured irradiate beam profile to required profile. An acrylic resin is cut by a ball type grinding wheel consisted on diamond powder and polished by a cone type felt buff with alumina ceramics powder. A CNC lathe is used to control these tools position. A shaper with 4mm of thickness works to convert multi-mode beam profile with 13mm of diameter into a flat top cylinder with 1mm of diameter. Its working distance is 60mm. Its transmittance is over 98%.It suceed to generate uniform melting mark of 0.6mm diameter on the steel target by YAG laser process.

Fringe Order Determination in Grating Projection Method and its Application to Shape Measurement of Lens Materials.

位相シフト法を導入した格子パターン投影法に正弦格子を適用するとともに0次のしまの決定を行う方式によって, 実際にレンズ素材の形状計測を行った.正弦格子を利用することによって位相シフトによって, 位相を求める際に生じる検出された位相の倍周期の周期的誤差を低減することが可能になった.さらに, 変形格子像の0次は薄膜色フィルタの補色の関係から決定することが可能になった.以上によって, レンズ素材の測定に有用な測定精度が得られた.さらに, 白色パウダの利用によって透明なレンズ素材に投影された格子パターンの観察を可能とした.これらを用いて, レンズ素材の形状の測定を試み, 実際に「ヒケ」の計測が可能であることを示した.さらに, 本手法は自動計測することも可能である.今後, ここで求まった「ヒケ」のデータを金型の設計にフィードバックし, 役立てていく予定である.

Blackening and its disappearance of stabilized zirconia ceramics in pulsed Nd:YAG laser drilling

Drilling characteristics of stabilized zirconia ceramics by pulsed Nd:YAG laser beams are experimentally discussed, whose power density is about 5×103 W/mm2. Effects of blowing gases of nitrogen, oxygen and air on drilling capability are also discussed. A hole deeper than 15 mm is easily drilled. Aspect ratio of the hole is 17. In this process, blackening of the material around the drilled hole is observed except for the drilling with the oxygen gas. The blackening disappears when the laser beam is bombarded on the blackened area with the oxygen gas. The cause is discussed on the basis of decrease and increase in oxygen content in zirconia.Drilling characteristics of stabilized zirconia ceramics by pulsed Nd:YAG laser beams are experimentally discussed, whose power density is about 5×103 W/mm2. Effects of blowing gases of nitrogen, oxygen and air on drilling capability are also discussed. A hole deeper than 15 mm is easily drilled. Aspect ratio of the hole is 17. In this process, blackening of the material around the drilled hole is observed except for the drilling with the oxygen gas. The blackening disappears when the laser beam is bombarded on the blackened area with the oxygen gas. The cause is discussed on the basis of decrease and increase in oxygen content in zirconia.