2. CONTENTS
Introduction
What is “ laser polishing”
Working principle
Methods of operation
Factors affecting roughness
Experimental set-up
Advantages
Disadvantages
Applications
Conclusion
3. INTRODUCTION
The surface roughness of a part or product
strongly
influences its properties and functions including
abrasion and corrosion resistance, optical
properties
as well as the visual impression the customer
desires.
The laser-polishing has already been one
important branch of research in material
surface processing as a new surface polishing
technology
4. WHAT IS “ LASER
POLISHING “
Laser polishing is a non contact
surface finishing process that uses
laser irradiation to achieve subsequent
surface smoothening
5. WORKING PRINCIPLE
Laser beam is used to melting the surface of the work piece
Due to the surface tension of the molten material the surface roughness is
smoothed during the re-melting process.
The resulting surface solidifies without cracks, pores or hidden defects out of the
molten material.
Nearly no material removal
High shape retention
Solid state laser source: continuous wave / pulsed, laser power 40-
500W
6. METHODS OF OPERATION
There are two different methods of operations used in laser
polishing
1. Macro polishing
2. Micro polishing
8. Using continuous wave laser radiation the macro
laser polishing process creates a continuous re-
melted surface layer which is between 10μm – 80μm
can be polished.
The re-melting depth have to be chosen according
to the material and the initial surface roughness.
Normally, fiber-coupled lasers are used with laser
powers of 70–300W.
The processing time is between 10 and 200 s/cm2
depending on the initial surface roughness, the
material and the desired roughness
10. In contrast to macro laser polishing, micro laser polishing is a
discrete rather than a continuous re-melting process
The re-melting depth is in the range of 0.5–5μm.
The pulse duration is normally in the range of 20-1000
nanoseconds and the molten material is already re-solidified
when the next laser pulse hits the surface and creates a new
melt pool.
Fiber-coupled lasers are used.
Processing time is less than 3 s/cm2 can be achieved.
11. FACTORS AFFECTING
ROUGHNESS
Initial surface roughness and especially the
lateral dimensions of the surface structures.
Thermo-physical material properties, e.g.,
heat conductivity , viscosity, surface tension,
and melting and evaporation temperature.
Homogeneity of the material: segregations
and inclusions especially downgrade the
surface quality.
13. With the laser radiation the surface of the glass
is heated.
Evaporation has to be avoided, because
otherwise material would be removed.
But the temperature must also be high enough
to reduce the viscosity of the glass
The most important process parameters are
the interaction time and the intensity.
14. The longer the interaction time and intensity,
the lower the roughness .
Usually, the laser power is between 30 and
4000W, the intensity on the work piece
between 70 and 500W/cm2 and the feed
rate between 2 and 80 mm/s .
Typical processing times are 1–10 s/cm2
15. Examples for polishing results
are shown in Table
Glass type Initial
Roughness
Roughness
after
polisihng
Lead glass Rf = 13.3μm Rf = 2.5μm
Fused silica Rf = 2μm Rf = 50 nm
TRC-33 Rf= 500 nm Rf = 1nm
16. ADVANTAGES
Automated machining
Polishing results are independent of the operator
High processing speeds, especially compared to
manual polishing
Selective polishing of specific areas
Polishing of milled, turned, ground, and eroded
surfaces
Non-contact processing, resulting in low
mechanical stress for the components
No grinding or polishing waste
17. DISADVANTAGES
Deviation in the form are not to be
corrected
The temperature rise below the
surface may be high, causing
unacceptable heating of the
substrate or distortion of the work
piece.
18. APPLICATIONS
Selective laser polishing of matt
surfaces
Selective laser polishing of photo
chemical etched surfaces
Glass polishing
Medical fields
Designing surfaces by creating
glosive effects.
20. CONCLUSION
In comparison to conventional polishing
processes like electro polishing, electro-
chemical polishing or slide grinding, laser
polishing opens up the possibility of
processing of small areas (< 0.1 mm²).
Laser polishing enhances the
appearance of design surfaces by
glossive effects, which cannot be
achieved with conventional machining
methods without a high demand in
human resources and time.
21. REFERENCES
Willenborg, E., "Laserpolieren von Werkzeugstählen,"
Dissertation RWTH Aachen University, Shaker,
Aachen, (2005).
Kiedrowski T., Willenborg E., Hack, S.,, K., "Generation of
design structures by selectiveWissenbach
polishing of metals with laser radiation," Proceedings of the
3rd Int. WLT-Conference on Lasers in
Manufacturing 2005, 297-300 (2005).
Willenborg, E., Wissenbach K., Poprawe R., "Polishing by
laser radiation," Proceedings of the 2nd Int.
WLTConference
on Lasers in Manufacturing 2003, 451-456 (2003).
Temmler, A., Willenborg, E., Wissenbach, K., "Structuring by
Remelting," Proceedings of the 5th Int. WLTConference
