Lernkarten
Which 3 different kinds of interaction are possible, when laser radiation is incident o material?
- Transmission
- Absorption
- Reflection
Which effect is necessary for the thermal effect on the workpieces?
Transmission
Absorbtion
Reflection
Absorption degrees (german: Absorptionsgrade) of the lasers used for materials processing on metals are ...?
unfortunately high
fortunately low
unfortunately low
Which efficent methods concerning the workpiece surfaces are feasible to improve absorption on metals?
- Coating of the workpiece surface with good-absorbing layers, e.g. graphite-sprays.
- Treat the workpiece with an etched surface (german: gebeizt)
- Allow it to build oxide-layers during heated-up (allow contact to air-oxygen during processing, if workpiece can sustain oxides).
How is the absorbtion on plastics with an CO2" Laser?
50 %
almost 100 %
10 %
Which are the 2 measuring principles to measure the intensity-profiles of a beam?
With Explanation!
- Systems, which work with a hollow, insidemirrored copper-needle. The copper-needle guides entering laser beam power to a photoelectric detector located in the rotation-axis. Withsoftware then a 2-dim. pattern of the beampowers is calculated, showing the positions of the measures and the measured beam-powers there.
- Imaging-technology, using a CCD-Photo-Chip. For this purpose here, of course it is heavily necessary to add largely damping glasses set in the optical path before the chip in order not to overheat it.
Advantages of CCD-camera-type systems:
- pulsed-laser beams
- extreme narrow focus-diameters of down to ca. 10 µm
- more variety of wavelengths (using appropri. CCDs).
Definition of a beam-diameter:
The diameter enclosing 86% of all measured beam-power is defined as the focus-diameter.
Thus, the measuring of the intensity-distribution of a beam also delivers the diameter of the beam.
Definition of the focus-diameter df:
The smallest measured diameter in the whole measured caustic of the focussed beam is df.
