Conductance based control system for additive manufacturing

A process for maintaining process stability of an additive manufacturing apparatus, wherein the apparatus comprises:

• a nozzle for output of a metal strip, the nozzle configured to be arranged at a distance from a substrate and configured to move relative the substrate in XYZ-axes,
• a heat source configured to melt the metal strip into a weld pool on the substrate, and
• an electrical power source configured to supply a current via the metal strip to the substrate;
• wherein the process comprises:
• depositing, by the nozzle, a layer of metal including the metal strip;
• determining an electrical conductance between the metal strip and the substrate by measuring at least one electrical property of the supplied current;
• determining a difference between the electrical conductance between the metal strip and the substrate and a desired electrical conductance;
• and
• adjusting, based on the difference between the electrical conductance between the metal strip and the substrate and the desired electrical conductance, at least one of:
• a substrate to nozzle distance, a speed of movement of the nozzle relative the substrate, an amount of supplied current, a heat provided by the heat source, and a rate of output of the metal strip.

An additive manufacturing apparatus for adding metal to a substrate by means of metal deposition, wherein the apparatus comprises:

• a nozzle for output of a metal strip, the nozzle configured to be arranged at a distance from the substrate, and configured to move relative the substrate in XYZ-axes,
• a heat source configured to melt the metal strip into a weld pool on the substrate, and
• an electrical power source configured to supply current via the metal strip to the substrate;
• and,
• wherein the additive manufacturing apparatus comprises a control system configured to:
• determine an electrical conductance between the metal strip and the substrate by measuring at least one electrical property of the supplied current;
• determine a difference between the electrical conductance between the metal strip and the substrate and a desired electrical conductance;
• and
• adjust, based on the difference between the electrical conductance between the metal strip and the substrate and the desired electrical conductance, at least one of:
• a substrate to nozzle distance, a speed of movement of the nozzle relative the substrate, an amount of supplied current, a heat provided by the heat source, and a rate of output of the metal strip.