Location of Printheads and Ink Cartridges 32 Ink Cartridges and Printheads The frequency with which you need to change ink cartridges depends on the workload of your HP DesignJet printer. Printheads should not need replacing so often, only when problems of image quality occur. If you find problems with the image quality, follow the procedure on page 16 in The Problem Is...Image Quality in this Pocket Guide .