Laser Machining – Taper Angle

Machining (drilling, cutting, milling) of a material with a pulsed laser using ‘standard’ focussing optics usually results in a small taper angle in the machined feature. This is due to a combination of the optical properties of the beam and the dynamics of material ablation.

The sketch below shows the cross-section for a hole showing the taper (exaggerated to show the features). The laser entrance side is larger than the laser exit side.

In most cases the taper angle is a few degrees. There is always some rounding at the entrance side though this can be made to be very small (few microns) depending on the material and the process used. In many applications the taper is not a problem in terms of functionality and often the slope angle is so small that the entrance and ext sizes are within the design tolerances anyway.

Applications where the hole’s limiting aperture is critical (e.g. filters or flow orifices), the hole exit size is made to the desired size, this being on the laser exit side.

With special optics the taper angle can be made to be zero or negative, but most commonly a small positive taper angle as shown above is produced in the vast majority of laser-machined parts.

For more information on Laser Machining – Taper Angle talk to Laser Micromachining Ltd