Systems, methods, and apparatus to control welding electrode preheating

1. A consumable electrode-fed welding-type system, comprising:

a welding-type current source configured to provide welding-type current to a welding-type circuit, the welding-type circuit comprising a welding-type electrode and a first contact tip of a welding torch;

an electrode preheating circuit configured to provide preheating current through a first portion of the welding-type electrode via a second contact tip of the welding torch;

current interpreter circuitry configured to determine a change in a contact-tip-to-work-distance between the first contact tip and a workpiece based on at least one of the welding-type current or the preheating current; and

an electrode preheating control circuit configured to adjust at least one of the preheating current or an electrode feed speed based on the change in the contact-tip-to-work-distance.

2. The system as defined in claim 1 , wherein the current interpreter circuitry is configured to detect the change in the contact-tip-to-work-distance by:

measuring the preheating current;

determining the contact-tip-to-work-distance based on the measurement of the preheating current;

identifying a change in the at least one of the welding-type current or the preheating current; and

determining the change in the contact-tip-to-work-distance based on the change in the at least one of the welding-type current or the preheating current.

3. The system as defined in claim 2 , wherein the current interpreter circuitry is configured to measure the preheating current by measuring a first average preheating current over a first time period.

4. The system as defined in claim 3 , wherein the current interpreter circuitry is configured to identify the change in the preheating current by identifying a difference between 1) a second average preheating current over a second time period and 2) the first average preheating current.

5. The system as defined in claim 2 , wherein the current interpreter circuitry is configured to determine the contact-tip-to-work-distance based on the preheating current by looking up the preheating current in a table associating preheating current values with contact-tip-to-work-distances.

6. The system as defined in claim 5 , wherein the current interpreter circuitry is configured to determine the contact-tip-to-work-distance based on the preheating current by looking up at least one of a welding setpoint voltage, the welding-type current, a heat input, or a resistance in the welding-type circuit.

7. The system as defined in claim 1 , wherein the current interpreter circuitry comprises a current sensor, the system further comprising a memory device configured to store a plurality of preheating current measurement values associated with corresponding contact-tip-to-work-distances.

8. The system as defined in claim 1 , wherein the welding-type current source is configured to execute a voltage-controlled control loop to provide the welding-type current.

9. The system as defined in claim 8 , wherein the electrode preheating control circuit is configured to control the preheating current to maintain the welding-type current within a current range and to maintain a heat input within a heat input range.

10. The system as defined in claim 1 , wherein the electrode preheating control circuit is configured to adjust the preheating current to maintain a constant heat input into a workpiece.

11. The system as defined in claim 1 , wherein the first contact tip is configured to conduct the preheating current, the first portion of the welding-type electrode being between the first and second contact tips of the welding torch.

12. A method, comprising:

providing welding-type current using a welding-type current source to a welding-type circuit, the welding-type circuit comprising a welding-type electrode and a first contact tip of a welding torch;

providing preheating current through a first portion of the welding-type electrode via a second contact tip of the welding torch; and

adjusting at least one of the preheating current or an electrode feed speed based on a change in a contact-tip-to-work-distance between the first contact tip and a workpiece.

13. The method as defined in claim 12 , wherein the determining of the change comprises:

measuring the preheating current;

determining the at least one of the contact-tip-to-work-distance or the stickout length based on the measurement of the preheating current;

identifying a change in the at least one of the welding-type current or the preheating current; and

determining a change in the at least one of the contact-tip-to-work-distance of the welding torch based on the change in the at least one of the welding-type current or the preheating current.

14. The method as defined in claim 12 , wherein the adjusting of the at least one of the preheating current or the electrode feed speed comprises maintaining a substantially constant heat input into a workpiece.

15. The method as defined in claim 12 , wherein the determining of the change comprises looking up a change in the preheating current in a lookup table stored in a memory device.

16. The method as defined in claim 12 , further comprising determining the change in at least one of the contact-tip-to-work-distance of the welding torch.

17. The method as defined in claim 16 , wherein the determining of the change in at least one of the contact-tip-to-work-distance of the welding torch or the stickout length comprises looking up at least one of the preheating current or the welding-type current in a lookup table.

18. The method as defined in claim 16 , wherein the determining of the change in at least one of the contact-tip-to-work-distance of the welding torch or the stickout length comprises looking up at least one of a resistance of the welding-type circuit, an enthalpy, a heat input, or a welding-type voltage setpoint in a lookup table.

19. The method as defined in claim 12 , wherein the adjusting of the preheating current or the electrode feed speed comprises controlling the preheating current or the electrode feed speed to maintain a target arc length.

20. A consumable electrode-fed welding-type system, comprising:

a welding-type current source configured to provide welding-type current to a welding-type circuit, the welding-type circuit comprising a welding-type electrode and a first contact tip of a welding torch;

an electrode preheating circuit configured to provide preheating current through a first portion of the welding-type electrode via a second contact tip of the welding torch;

sensors configured to monitor the preheating current and the welding-type current; and

a control circuit configured to maintain a constant heat input into a weld by adjusting at least one of the preheating current or an electrode feed speed based on a combination of the preheating current and the welding-type current as a proxy for contact-tip-to-work-distance between the first contact tip and a workpiece.