Abstract: A three-dimensional (3D) metal object manufacturing apparatus has a build platform heater that is configured with a plurality of temperature sensors and heating elements distributed throughout the heater. The signals generated by the temperature sensors are monitored by a controller and when one of the signals is outside of a temperature range around a temperature setpoint for the heater, the controller adjusts a PWM signal operating a switch that connects the heating element corresponding to the temperature sensor that generated the signal outside of the temperature range. The temperature sensors and heating elements are distributed in a plurality of cells that border one another in a contiguous pattern.