Real-time liquid metal droplet analyzer with spatial modulation in additive manufacturing

A method of controlling jetted droplets in a 3D printer, the method comprising:

• providing a build platform for receiving molten droplets from an ejector movable at various distances from the build platform;
• ejecting the molten droplets along a jetting path from the ejector onto a solid of a material same as the molten droplets formed on the build platform;
• sensing light emanating from the molten droplets to generate an electrical signal corresponding to the light, wherein the light comprises an infrared light from the molten droplets;
• encoding information in the light using an optical mask positioned adjacent to the jetting path, wherein the optical mask comprises a plurality of regions comprising light-blocking regions and light-passing regions configured to modulate the electrical signal as the molten droplets travel along the jetting path, wherein the light-passing regions comprise a first window transmissive to infrared light and a second window transmissive to infrared light, wherein the first window and second window exhibit different levels of infrared light transmission for a given range of infrared frequencies;
• and
• determining a temperature of the molten droplets based on a ratio of a first signal amplitude corresponding to the first window and a second signal amplitude corresponding to the second window, and adjusting a voltage profile of voltage pulses provided from a power source to control the ejector based on the electrical signal.

An additive production system comprising:

• a build platform;
• a controller in control of a jetting path;
• an ejector moveable at various distances from the build platform and configured to deposit molten droplets along the jetting path from the ejector to the build platform on a solid of a material same as the molten droplets formed on the build platform;
• a sensor positioned adjacent to the jetting path;
• an optical mask positioned adjacent to the jetting path and between the molten droplets and the sensor, the optical mask comprising a plurality of regions comprising light-blocking regions and light-passing regions, wherein the light-passing regions comprise a first window transmissive to infrared light and a second window transmissive to infrared light, wherein the first window and second window exhibit different levels of infrared light transmission for a given range of infrared frequencies, and wherein the optical mask is configured to modulate a signal of the molten droplets to be detected at the sensor, wherein the signal measures an infrared light from the molten droplets;
• and wherein the controller is configured to determine a temperature of the molten droplets based on a ratio of a first signal amplitude corresponding to the first window and a second signal amplitude corresponding to the second window, and adjusts a voltage profile of voltage pulses provided from a power source to control the ejector and the molten droplets based on the signal.