Hotwire deposition material processing system and method
A material processing system includes a power supply and a wire feeder to feed a wire electrode for a material processing operation. The enthalpy and/or temperature of a region of the tip of the electrode is maintained substantially constant via closed loop control. The control may be based upon regulation of current applied to the electrode. The control of the current may be based upon an electrode extension error. Wire feed speed may also be controlled to assist in maintaining a substantially constant enthalpy and/or temperature near the electrode tip.
1 . A material processing method, comprising:
determining a desired change of enthalpy in an extension of a consumable electrode;
advancing the electrode toward a workpiece to initiate a material processing operation;
measuring enthalpy of the electrode;
determining an actual change of enthalpy of the electrode; and
regulating the enthalpy of an end of the extension of the electrode during the material processing operation to maintain a desired enthalpy change in the extension of the electrode using a linear relationship between a temperature of the electrode and the enthalpy above a fusion transition temperature of the electrode, wherein the enthalpy is regulated by regulating hotwire current applied to the electrode.
2 . The method of claim 1 , wherein the current is regulated based upon a determined electrode extension error.
3 . The method of claim 2 , wherein the current is regulated based upon a proportional gain value.
4 . The method of claim 1 , wherein the enthalpy is controlled to maintain a generally constant temperature of a region of the extension of the electrode.
5 . The method of claim 1 , wherein the enthalpy is controlled based upon known characteristics of the electrode selected for the material processing operation.
6 . The method of claim 5 , wherein the characteristics are determined based upon an operator input of the selected electrode into a system power supply or wire feeder.
7 . The method of claim 1 , wherein the enthalpy is controlled based at least in part upon the relationship:
E
E
*
λ
*
I
2
=
[
π
D
w
2
4
τ
ρ
w
]
[
H
f
-
H
o
]
where EE is electrode extension, I is material processing current, D w is the diameter of the electrode, τ is linear flow rate of the electrode, ρ w the density of the electrode at a known temperature, H f is a desired enthalpy of the electrode and H o is an initial enthalpy of the electrode.
8 . The method of claim 1 , wherein for the purposes of control, the enthalpy is assumed to be generally proportional to temperature.
9 . The method of claim 1 , wherein:
the linear relationship between the temperature of the electrode and the enthalpy above the fusion transition temperature of the electrode is a first linear relationship; and
the regulating of the enthalpy further uses a second linear relationship between the temperature of the electrode and the enthalpy below the fusion transition temperature of the electrode.
10 . A material processing method, comprising:
determining a desired change of enthalpy of a consumable electrode in an extension of the electrode;
advancing the electrode toward a workpiece to initiate a material processing operation;
measuring enthalpy of the electrode;
determining a change of enthalpy in the extension of the electrode; and
regulating the enthalpy of the tip of the electrode by regulating a wire feed speed of the electrode to maintain the desired enthalpy change in the extension of the electrode using a linear relationship between a temperature of the electrode and the enthalpy above the fusion transition temperature of the electrode.
11 . The method of claim 10 , wherein the wire feed speed is regulated based upon a determined electrode extension error.
12 . The method of claim 10 , wherein the enthalpy or temperature is controlled to maintain a generally constant enthalpy or temperature of a region of an end of an electrode extension of the electrode.
13 . The method of claim 10 , wherein the enthalpy or temperature is controlled based upon known characteristics of the electrode selected for the material processing operation.
14 . The method of claim 13 , wherein the characteristics are determined based upon an operator input of the selected electrode into a system power supply or a wire feeder.
15 . The method of claim 10 , wherein:
the linear relationship between the temperature of the electrode and the enthalpy above the fusion transition temperature of the electrode is a first linear relationship; and
the regulating of the enthalpy further uses a second linear relationship between the temperature of the electrode and the enthalpy below the fusion transition temperature of the electrode.
16 . A material processing system comprising:
a power supply configured to provide power for a material processing operation;
a wire electrode feeder configured to advance a consumable electrode during the material processing operation; and
a control system configured to:
determining a desired change of enthalpy in an extension of the electrode;
measure enthalpy of the electrode;
determining a change of enthalpy of the electrode; and
regulate enthalpy of a tip of the electrode by regulating wire feed speed of the electrode to maintain the desired enthalpy change in the extension of the electrode using a linear relationship between the temperature of the electrode and the enthalpy, wherein the desired enthalpy change is configured to heat a portion of the electrode to a first temperature less than or equal to a melting temperature of a material of the electrode.
17 . The system of claim 16 , comprising a current sensor connected to detect current applied to the electrode, wherein the control system is configured to regulate enthalpy by regulating current applied to the electrode based upon feedback from the sensor.
18 . The system of claim 17 , wherein the control system is configured to regulate current based upon a determined electrode extension error.
19 . The system of claim 18 , wherein the current is regulated based upon a proportional gain value.
20 . The system of claim 16 , further comprising a secondary heat source, wherein the secondary heat source is configured to heat a region of an electrode extension of the electrode from the first temperature to a second temperature greater than or equal to the melting temperature of the material of the electrode.