Experimental study of fabricating a microball tip on an optical fibre

Many side walls of microholes and grooves are not easily measured by current optical or non-contact measuring instruments. Microcontact probes are increasingly demanded in the market. A good ball tip is the basic element for the construction of a contact probe. This paper proposes a low-cost and in-process system to fabricate a microspherical tip on an optical fibre using a commercial fibre fusion splicer. Based on the principles of arc discharging energy absorption and the surface tension phenomenon, a microsphere is formed at the tip of the optical fibre. Experimental results showed that with the selection of proper process parameters, such as the arc power, cleaning arc power offset, and cleaning time, a spherical tip about 300 mu m in diameter and with 6 mu m roundness error could be produced using a 125 mu m diameter single-mode optical fibre. The offset distance between the ball centre and the fibre stylus central line due to the gravity effect could be suppressed to less than 3 mu m by rotating the fibre between the discharging cycles. By forming the sphere probe tip directly on an optical fibre, this approach demonstrates an easy and in-process dimensional controlled method to shorten the manufacturing lead-time for making a 3D microprobe. The microprobe can be used for microscale/ nanoscale coordinate measuring machines (CMMs) to enhance the measurement resolution and extend the capability for meso- to micro-objects.