surface finishing

1. LASER
POLISHING
GUIDED BY SUBMITTED BY
JOHN PHILIPOSE VINEETH H R
ASST. PROFESSOR S7 ME
ME DEPARTMENT ROLL NO 58
LMCST LMCST

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

7. 1.MACRO POLISHING
 Macro polishing is carried out with continuous
wave laser radiation.

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

9. 2.MICRO POLISHING
 For micro laser polishing pulsed laser radiation is
used

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.

12. EXPERIMENTAL SET UP
 Material selected : Glass
 Laser selected : co2 laser

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.

19. SAMPLES

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

22. THANK YOU