I have disassembled an old hard disk and I making the voice coil move by applying a voltage between the terminals of the coil. I plan to use this to raise or lower a flag attached to the actuator arm.
The problem is that if I use a voltage of 5V the actuator can't generate enough torque to lift the flag. If I give it 12V, then it works. The current across the coil is around 600mA.
However at 12V when the actuator is powered the coil will start to heat very quickly, enough to be painful to touch. I have tried to keep it powered up for around half an hour and I didn't see any damage, just a lot of energy being converted into heat.
However I am worried that on the long run the heat might damage the coil. In my application the coil might remain powered for around 3 to 5 hours, in an environment that can get to 40°C ambient temperature.
Am I being paranoid or is there actually a risk of melting the the coils or otherwise damaging them ?
To clarify, after reading some of the answers below: I appreciate the fact that I am using the device well beyond its designed operation parameters for a function it was never intended for. What I would like to know is if this can cause enough stress to destroy it, or if there are no other likely side effects beyond the extra heat that is generated. For example I know that a DC motor that is operated at a too high RPM can destroy itself in a various ways. But I have no idea about a voice coil actuator.