A coffee machine including a controller, an infusion cylinder that can be loaded with a ground coffee dose, an ejection piston slidably supported inside the infusion cylinder, a closing piston engageable in the infusion cylinder to create a closed infusion chamber for the ground coffee dose, delimited between a lateral wall of the infusion cylinder, the ejection piston and the closing piston. Electrical actuation moves the infusion cylinder between a lower travel limit stop, where the ground coffee dose is loaded, and an upper travel limit stop where the infusion process occurs, an adjuster for positioning the upper travel limit stop based on the size of the loaded ground coffee dose, so that in the position of the upper travel limit stop, the infusion chamber has a volume sufficient to contain the ground coffee dose without compressing it.