Electron beam layer manufacturing using scanning electron monitored closed loop control

A process for layer manufacturing a three-dimensional work piece comprising the steps of:

• (a) feeding raw material in a solid state to a first predetermined location;
• (b) exposing the raw material to an electron beam to liquefy the raw material;
• (c) depositing the raw material onto a substrate as a molten pool deposit, the deposit having a forward edge region and a trailing edge region, under at least one first processing condition;
• (d) monitoring the molten pool deposit for at least one preselected condition using detecting of scatter from a scanning electron beam contemporaneously with the depositing step, optionally using a detector that is in a housing configured so that the detector detects electrons of a preselected characteristic;
• (e) consecutively switching the scanning electron beam back and forth between the electron beam for melting and the scanning electron beam at a rate of at least 5 times per second;
• (f) solidifying the molten pool deposit;
• (g) automatically altering the first processing condition to a different processing condition based upon information obtained from the monitoring step (d);
• and
• (h) repeating steps (a) through (g) at one or more second locations for building up layer by layer, generally along a z-axis that is orthogonal to an x-y plane, a three-dimensional work piece;
• wherein the electron beam is employed for both exposing and monitoring so that the scanning electron beam is a beam emitted from an electron beam generating device that also emits the electron beam to liquefy the raw material.