A core assembly for an injection molding-machine. The assembly includes a movable mold half and a stationary mold half clamped onto each their platen of an injection molding-machine. It also includes an actuator for advancing and retracting during operation at least one core into and from a mold cavity in a mold. The actuator is connected to a core-carrier for carrying the at least one core. The core-carrier is slidingly mounted to and partly projecting from a guidance connected to one of the mold halves. A first hole is formed in the closed mold for slidingly receiving the projecting part of the core-carrier. The core assembly allows products to be continuously molded with an extremely high degree of accuracy, and it is simple, inexpensive and easy to mount and maintain while also allowing for positioning of cores at various angles relative to the mold.