We are using a PC power supply to power our project, which is a Robotic arm. Since our power supply has a 12V output voltage, can anyone please advise how to step down the voltage (12V) to 6V.

The L7806 regulator is also an option, but it drops the maximum achievable current. How to avoid this problem, where the current drops along with the voltage?

NOTE: We are using 5 servos, and looking for the simplest possible solution to step down the voltage to 6V and still deliver 7.5A.

Can someone please suggest any voltage regulator which has output current of 7.5Amps.

You need a switching regulator.
Look at the StepDown regulators here for examples

Your duplicate post elsewhere was deleted. Post once, have a little patience.

Use the 5V output from the power supply. Most stock DC-DC converters are 5V out anyway, 6V is rare and not cheap.