A system uses microwave energy to remove support material from a three-dimensional printed object with reduced risk of damage to the object. The system includes a microwave source, a three port device, a susceptor, a temperature sensor, and a controller. The controller operates the microwave source to direct microwave energy into a first port of the three port device, which emits the microwave at a second port of the three port device to irradiate the three-dimensional object and melt the support material. Reflected microwave increases as the amount of support material contacting the object is reduced and enters the second port of the three port device, which directs the reflected energy to the susceptor coupled to a third port of the three port device. The controller monitors the signal generated by the temperature sensor and deactivates the microwave source in response to a predetermined condition being reached.