An assembly method for an injection or infusion device comprising: Providing a first housing part including a cartridge closed by a plunger. Providing a second housing part connectable to the first housing part comprising: a drive mechanism for advancing a piston rod, a dose setting mechanism and a dose limiting mechanism configured to count and accumulate the set dose units and limit dose setting. Measuring the position of the cartridge plunger and the position of the piston rod and calculating a distance (d) between the piston rod and the plunger if the first and second housing parts were connected with each other. Selecting a dose and advance the piston rod using the dose setting and drive mechanism if the calculated distance (d) is between a minimum distance and a maximum distance thereby operating the dose limiting mechanism. Connecting the first housing part comprising the cartridge and the second housing part to form the injection or infusion device.
