Today’s post is a visual portrayal of how to optimize peak power and pulse width during laser welding.
First let’s define the two concepts. Laser peak power is the maximum power that the laser provides either in continuously on (CW) mode or pulsed mode. It is a key welding parameter, used to control penetration. Peak power controls the maximum power of each pulse and is measured in watts (W) or kilowatts (kW).
Laser pulse width is the duration of the laser pulse, measured in millisecond (ms). Pulse width is a fine tuning parameter, used to adjust both penetration and weld width, and if needed, weld stabilization. The following figure shows the effect of increasing pulse width and peak power on weld dimensions:
Optimum peak power is defined as the peak power that creates the deepest penetration at a given energy without material expulsion. Welds made with high peak power and short pulse widths are narrow and deep, exerting a high thermal cycle on the weld material.
Note how increasing the pulse width increases the weld dimensions in both penetration and width and heat affected zone by increasing the heat conduction time. To increase weld width, reduce the thermal cycling, and minimize depth variation, operators should increase the pulse width, which will introduce a more conduction-based welding mechanism.
When optimizing the peak power and pulse width it is recommended to find the corners of the process window; high/low peak power & high/low pulse width. Too high peak power will exhibit spatter, too low will not join the parts. Too low pulse width will cause spatter or insufficient penetration, too long pulse with overheats the part and is very inefficient use of pulse energy in terms of joining.
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