Is it possible to unparent an object on a specific keyframe? I have tried to make an animation to test my skills so far (have only used blender in about 3 months). But I got a problem when the "robot arm" should take the letter and put it on the wall and then the arm would disappear from the camera(it will be a lot easier to understand if you look at the  .blend file ;). I am using parenting to make the animation easier to make but when the letter is on the wall I want it to stick there and not follow the arm but I don't know how to do it. Is it any way you can unparent an object on a specific keyframe? Or is it any other solution? Would appreciate an answer :).
I'm sorry I'm on mobile so I can't check your file. Did you try to :


Select your object (child)
In Properties go to Object constraints
On the last frame of constraint: Right clic on Influence and insert keyframe and change it to 1
On the next frame: change it to 0
You might click on set inverse if the object move