Method and apparatus for monitoring electro-magnetic radiation power in solid freeform fabrication systems
Embodiments of the present invention are directed to a system and method for controlling fabrication of three-dimensional objects, layer by layer, the system comprising a printing assembly, including an irradiation unit and a printing head, the printing assembly is movable between a printing area and a service area. A light sensor positioned at the service area to measure output radiation power of the irradiation unit at a printing plane and a controller to receive information from the sensor and to automatically adjust electrical power supplied to the irradiation unit based on the information.
1. A method for forming three-dimensional objects, layer by layer, on a fabrication platform, the method comprising:
printing layers of a three-dimensional object by selectively dispensing a building material, layer by layer, from a printing head and curing deposited layers using an irradiation unit;
moving the irradiation unit to a service area;
measuring an output radiation power of the irradiation unit by a first light sensor positioned at the service area, wherein a vertical distance between the first light sensor and the irradiation unit at a time of measuring is the same as a vertical distance, at a time of printing, between the irradiation unit and a top deposited layer of the three-dimensional object being formed; and
automatically adjusting an electrical power supplied to the irradiation unit based on information received from the first light sensor.
2. The method of claim 1 , wherein the building material has a first curing efficiency within a first range of wavelengths which is higher than a second curing efficiency within a second range of wavelengths and the first light sensor is substantially responsive to radiation at the first range of wavelengths and non-responsive to radiation at the second range of wavelengths.
3. The method of claim 1 , wherein the irradiation unit comprises a radiation source positioned within a housing and the method further comprising:
directly measuring an output radiation power of the radiation source by a second sensor located in proximity to the radiation source; and
automatically adjusting the electrical power supplied to the irradiation unit based on information received from both the first light sensor and the second sensor.
4. The method of claim 1 , wherein the irradiation unit comprises a radiation source positioned within a housing having a transparent window and a reflecting surface and the method further comprising:
directly measuring an output radiation power of the radiation source by a second sensor;
automatically comparing between information received from the first light sensor and information received from the second sensor to determine a status of the transparent window and the reflecting surface; and
sending an alert to a system operator if the status of the reflecting surface and the window indicates that human intervention is required.
5. The method of claim 1 , wherein the first light sensor is an ultraviolet (UV) sensor responsive in at least part of the range between about 280 nanometers and about 320 nanometers.
6. The method of claim 1 , wherein the first light sensor is an ultraviolet (UV) sensor responsive in at least part of the range between 280 nanometers and 400 nanometers.