Sung-Joon Park

A simple pulsed CO2 laser with long milliseconds pulse duration

We demonstrate a simple pulsed CO2 laser with long pulse duration of millisecond order in a tube at a low pressure of less than 30 Torr. The power supply for our laser system switches the voltage of the ac power line (60 Hz) directly. The power supply does not need elements such as a rectifier bridge, energy-storage capacitors, or a current-limiting resistor in the discharge circuit. In order to control the laser output power, the pulse repetition rate is adjusted up to 60 Hz and the firing angle of the silicon controlled rectifier (SCR) gate is varied from 30° to 150°. The maximum laser output of 35 W is obtained at a total pressure of 18 Torr, a pulse repetition rate of 60 Hz, and a SCR gate firing angle of 90°. In addition, the resulting laser pulse width is approximately 3 ms (full width at half maximum). This is a relatively long pulse width, compared with other repetitively pulsed CO2 lasers.

Simplified power supply for long pulse CO2 laser using zero cross switching technique

Abstract We propose a simple power supply for a longitudinally pulsed CO2 laser with long pulse duration by the switching control of AC line ( 60 Hz ) on HV leakage transformer primary, which can generate long pulse of about 3 ms compared to a typical pulsed power supply. In this power supply, a low voltage open loop control for high voltage discharge circuit is employed to avoid the HV sampling or switching, and AC line voltage switched directly by a SCR is applied to the leakage transformer primary. Thus, there is no need of a rectified bridge and an energy-storage capacitor in the discharge circuit, and the leakage transformer allows one to omit a current-limiting resistor. In order to control the laser output power, the pulse repetition rate is adjusted up to 60 Hz . A ZCS circuit and a PIC one-chip microprocessor are used to control the gate signal of SCR precisely.

Laser Welding Parameter Variations and its Application for Plastic Adhesion

a parametric investigation was conducted to evaluate the effect of the laser beam for plastic adhesion. To determine the best condition for plastic adhesion, the co₂ (wavelength 10.6㎛) and nd:yag (wavelength 1.06 ㎛) laser were experimented with. From the experiment results obtained, the nd:yag laser was revealed to be the most suitable for plastic adhesion. In this study, three adhesion parameters such as input power level, working time of laser beam and pps (pulse per second) were systematically adjusted for suitable adhesion. From these experiments, it was observed that the target plastic melted and was evaporated by the nd:yag laser. Furthermore, the relationships between adhesive surface by laser beam and above three parameters were discovered.

Deduction of Optimal Conditions for Acrylic Etching Technique by using CO 2 Laser

Laser cutting with the micro-control technique has great potential to be employed for acrylic machining. In this paper, the optimal conditions of acrylic etching have been investigated. The three parameters such as laser power, moving velocity, and thickness of acrylic are experimented to find out optimal conditions. From these experimental results, we have known that it is very important to control accurate power by the TRIAC switching technique. The best condition of acrylic etching is performed 10 Wand 72 ㎜/sec at the plastic thickness of 1.33 ㎜. The other case is performed 10W and 48 ㎜/sec, and 12 Wand 56 ㎜/sec at the acrylic thickness of 2.00㎜, respectively.