Patent EP-2324949-A1 (EP)
Inventor: POEHLER MANFRED DR
IPC: B23K26/06
Filed: 2010-11-19
Abstract: The laser material processing device for engraving of printing rolls with coating made of an elastomeric material such as rubber, comprises laser beam emitting carbon dioxide laser radiation source, which has a beam ratio K of 0.8-1 and a maximum beam diameter of 2 W m a x, an infrared-radiation modulator (5), where 95-100% of the radiation power of the incident laser beam is modulated and/or deflected on the infrared-radiation modulator through the infrared-radiation modulator, a telescope (3) arranged between the laser radiation source and the infrared-radiation modulator. The laser material processing device for engraving of printing rolls with coating made of an elastomeric material such as rubber, comprises laser beam emitting carbon dioxide laser radiation source, which has a beam ratio K of 0.8-1 and a maximum beam diameter of 2 W m a x, an infrared-radiation modulator (5), where 95-100% of the radiation power of the incident laser beam is modulated and/or deflected on the infrared-radiation modulator through the infrared-radiation modulator, a telescope (3) arranged between the laser radiation source and the infrared-radiation modulator, where the telescope has the maximum beam diameter of 2 W m a xaround a factor x >= 1, and a beam forming absorber (4) arranged between the telescope and the infrared-radiation modulator. A central region of the laser beam radiation, whose shape and size correspond to the usable opening of the infrared-radiation modulator passes through the beam forming absorber to the infrared-radiation modulator, and marginal areas of the laser beam radiation lying external to the central region are absorbed by means of reflective surface of the central region. The telescope has the maximum beam diameter of 2 W m a xaround a factor x, where x is present in the region of 1.5-2. The distance between the beam forming absorber and the infrared-radiation modulator is 10-500 mm. The beam forming absorber is formed in rotationally symmetrical and coaxial with the laser beam propagation direction. A circular inlet opening is arranged with a diameter of dE 2 W m a x+- 5%. A coaxial outlet is provided with a diameter dA in an axial distance A, which is greater than the diameter d E. The diameter dA is provided in coordination with the distance A with the standard, where a beam width alpha defines through arctan [(dA-dE)/2A] in 3-30[deg] C. A sharp-edged circular inlet opening of the beam-forming absorbent polymers correlates in the contour of line equal intensity of the laser beam radiation. An intensity distribution of laser radiation beam is formed with the telescope by the circular shape, and the counter of the sharp-edged opening of the beam forming absorber forms a line equal intensity that passes through 70-97% of the laser radiation power and the generated laser beam images on the infrared-radiation modulator in a rotation symmetrical reflection area of infrared part of 3-30% arranged in beam propagation direction. An absorption element is coaxially arranged with water cooling to the reflection area so that the reflective portions of the laser radiation beam are absorbed. A beam splitter and further beam splitter are arranged between the 5-100% of adjustable direct current-excited carbon dioxide laser radiation source and the telescope. A beam power attenuator is optionally arranged between all sub-beams of the telescope.