Dosing Operation In A Medical Device

This invention relates to a method of controlling a dosing operation where a piston in a medical device is moved to a desired position, the dosing operation applies a motor to provide a force from the piston to expel a dose of a liquid medicament, said method comprising the steps of: moving the piston, at a first fixed speed, to a first position of the movement, moving the piston, at a decreasing speed, from said first position to a second position of the movement, and moving the piston, at a second fixed speed, from said second position to the desired position of the movement. The method further comprises the step of letting a fixed waiting time pass, when the piston has reached the desired position. This enables for a precise movement and stop of the piston leading to a precise dose, minimized post dripping and to that only a fixed and short waiting time need to go before a user can withdraw an injection needle of the medical device from his skin.