A three-dimensional (3-D) printer includes build and support material development stations positioned to transfer layers of build and support materials to an intermediate transfer surface. The intermediate transfer surface transfers a layer of the build and support materials to a platen each time the platen contacts the intermediate transfer surface. A sensor detects the thickness of the layer on the platen, and a mechanical planer is positioned to contact and level the layer on the platen as the platen moves past the mechanical planer. Additionally, a feedback loop is electrically connected to the sensor and the mechanical planer. The mechanical planer adjusts the amount of the build material and the support material removed from the layer based on the thickness of the layer on the platen, as determined by the sensor.