Elsevier

CIRP Annals

Volume 60, Issue 1, 2011, Pages 363-366
CIRP Annals

A study on laser touch dressing of electroplated diamond wheels using pulsed picosecond laser sources

https://doi.org/10.1016/j.cirp.2011.03.117Get rights and content

Abstract

An investigation to explore the possibility of touch dressing of electroplated diamond wheels using a pulsed picosecond laser (ps-laser) beam (Yb:YAG) is presented. The laser beam is irradiated on the wheel to cut the diamond grains within a defined grain protrusion without any thermal damage on the nickel bond. The laser parameters were systematically varied to achieve a reliable touch dressing process. The microscopic investigations prove thermal damages neither on the diamond grain nor on the bond. Series of SiC wheel dressing experiments were carried out to compare mechanical touch dressing of the electroplated diamond wheel with laser dressed wheels.

Introduction

Touch dressing of superabrasive wheels is usually applied to electroplated bond material, where an accurate profile and defined grain protrusion is necessary. Touch dressing of diamond or CBN wheels can be conventionally done using a diamond roll or wheel as truer and/or dresser. In the case of touch dressing, both the wheel and truer are diamond plated, and have almost the same hardness resulting in a time consuming and relatively expensive process. That is why an alternative method to reduce process time as well as cost is a matter of high interest in industry.

Upon discovering the benefit of lasers in the machining industry, laser conditioning has always been an interesting alternative to conventional mechanical dressing. However, due to certain drawbacks and technological problems, its use in industrial applications was limited. In the case of touch dressing of electroplated diamond wheels, it is much more difficult to reach the realized target because the laser beam must cut the diamond grains with high accuracy, without any kind of thermal damage either to the diamond grain (graphitization, residual stress, etc.) or to the nickel bond material. This research is an important step forward to the realized target using a pulsed ps-laser. This paper presents a successful attempt on touch dressing of an electroplated diamond wheel using a ps-laser source.

Section snippets

Laser dressing, state of the art

Laser technology for conditioning of superabrasives was first proposed by Westkaemper [1] for dressing and truing of resin bonded CBN grinding wheels. The results show a topography with sufficient chip clearance compared with conventional dressing methods. It also illustrated approximately the same values for grinding force and roughness after grinding. Timmer [2] utilized a Nd:YAG laser to differently bonded diamond and CBN grinding wheels both radially and tangentially to the wheel surface.

Laser system

The experimental setup (Fig. 1) consists of the laser system (1) producing laser pulses with a pulse width tP < 10 ps and a maximum pulse energy of eP = 125 μJ at a maximum repetition rate of fP = 400 kHz. The experimental wavelength is λ = 1030 nm in the near infrared. The setup consists of multiple mirrors, a beam expansion unit (4.5) and a two-dimensional scanning system (8). The beam expansion unit itself consists of a concave and a convex lens.

This increases the beam diameter dB = 5 mm to dB = 8.5 mm prior

Experimental results

Evaluation of multiple validation samples in terms of raman-spectroscopy (Fig. 3) reveals that within the cut kerf, there is no presence of a graphite layer. Even after irradiation with ten repetitions and multiple pulses per area, the measured peak position value is 1332.49 cm−1 compared to the expected value which is 1332.5 cm−1. This is in good agreement to the quality of natural or High-Pressure High-Temperature (HPHT) synthetic diamond [10]. There is no evidence of a second peak around the

Conclusions and next steps

Using ps-laser sources, a great potential for high precision and a highly reliable method for touch dressing of the diamond grinding wheels is observed. Diamond grains can be cut without remarkable graphitization effects. Comparison of wheel topography before and after mechanical and laser touch dressing shows a very similar form within Abbott-Firestone-Curves as conventional roughness values (Ra and Rz). The lower dressing forces after dressing of SiC grinding wheels with diamond toch dressed

Acknowledgments

The authors wish to gratefully acknowledge the financial support which was granted by the Swiss Innovation Promotion Agency as well as the technical support provided by Faessler AG, Dubendorf and Trumpf Laser AG, Baar, both located in Switzerland.

References (10)

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