I don't know what is in your CD player, but it sounds like you are asking in general how to create linear mechanical motion that is electrically controlled.
The most obvious answer is a solenoid. Look around and you will see many different types. These are basically a magnetic plunger moved by the magnetism of a coil.
There are also devices known as voice coils, which are the same concept as a solenoid except that the coil is intended to move. They are called voice coils because this is the mechanism used to make loud speaker cones move.
There are also such things as linear motors. These are like rotary motors with the magnetic poles sortof unwrapped in a line.
Of course rotary motion, such as produced by a electric motor, can be turned into linear motion mechanically. A rack and pinion arrangement is one way. There can also be lever-arm driven mechanisms, which are in turn driven by geared down motors.
Getting accuracy is a separate issue. A basic solenoid is generally intended to be on or off. Voice coils can position quite accurately as a function of current when working against a known mechanical spring force. If a stepper motor is used, then the rotary motion is known open loop, and this can be turned into known linear movement. Otherwise, you will need some kind of mechanical position sensing and closed loop feedback to control the actuator. There are again many types of that, but that's getting too far afield of your question.
Whoever downvoted this answer, please explain what you think is wrong. Phantom downvotes don't benefit anyone since nobody knows what you object to. It also doesn't give anyone a chance to decide whether you might be wrong.
Look here2011-04-02 15:52:02 by technerd
The applications for linear motors and linear actuators overlap, so maybe you can use a linear actuator
The latest issue of the catalog from American Science and Surplus, also found at , has a few linear actuators, but they are 12 volt, and cheap.
Similar, more expensive, units are found at the surplus giant Herbach and Rademan who have an online catalog
Personally, I would order by mail, rather than drive anywhere in S.F.
McMaster2008-11-04 12:38:40 by iamlucky13
Sorry, they're order only. No brick-and-mortar store.
They sell DC solenoids as well as screw drive linear actuators. Things like door locks are typically solenoids, but relatively low force (~1 pound) ones. It's hard to find a solenoid that generates more than a few pounds, and they often have limited duty cycles, meaning you need to shut them off within a given time to prevent overheating. Also, force is reduced the further a solenoid is extended.
Screw drive linear motors can typically hold a load with no power and have consistent force throughout their stroke, but if you cycle them too fast, they may also exceed their duty cycle
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