PlayStation 3 often doesn't take in the disk in

Hello Maria! Great question! You may have to replace the whole drive, but before you go and do all that, try the procedure outlined in this thread first:

How to realign blu-ray dirve

Also, depending on the generation of PS3, you may just need to push the disk in further in order to get it to take the disk. On some models, there is a small IR sensor that senses when a disk has been inserted, and it starts the disk uptake process. This often fails. However, there is also a mechanical trigger for the disk uptake that starts when the uptake wheels get spread far enough apart. This only occurs when the disk is pushed in most of the way.

Good luck, and let us know how it works out.