Abstract: An automated device for plasma surface preparation of a thermoplastic part including a first support mechanism for a thermoplastic part and a second support mechanism for a plasma torch including a rotating cylindrical tip, the first and/or second support mechanism being movable so that the torch and the part have a relative movement enabling the torch to travel over a treatment zone of the part. The device further includes, on the plasma torch, a controller controlling a distance between the tip of the torch and the part. The controller includes a measuring rod positioned axially on the tip of the plasma torch. The device further includes a carriage that can be moved in the direction of the axis of the torch interposed between the movable torch and the second support mechanism. The movable carriage counteracts a displacement about an equilibrium or stop position.