Electric heating – Metal heating – By arc
Reexamination Certificate
1999-07-01
2001-05-22
Shaw, Clifford C. (Department: 1725)
Electric heating
Metal heating
By arc
Reexamination Certificate
active
06236017
ABSTRACT:
FIELD OF INVENTION
The present invention relates to welding systems in general and more specifically to methods and apparatus for assessing weld quality produced by arc welding systems.
BACKGROUND OF THE INVENTION
Arc welding processes are well-known in the art and have been used for decades in production and other environments to join together two or more separate items or workpieces. Depending on the particular application, the part produced by the arc welding process may be more or less tolerant to variations in weld quality. For example, certain applications may be quite tolerant to variations in weld quality, with a wide range of weld defects still resulting in an acceptable part. Other applications, however, are very fault intolerant, with very few, if any, weld defects being tolerable in an acceptable part.
In many production welding applications, the procedures for producing a weld for a given application are usually established in advance. Accordingly, the rejection rate (i.e., the rate at which a defective weld will result in a defective part) is usually highly correlated with the established welding procedure. If a good procedure is established, then the rejection rate usually will be low. On the other hand, a fundamentally unsound welding procedure will result in a relatively high part rejection rate.
Even if a sound welding procedure is developed, the ultimate part rejection rate depends to a large extent on how closely the system operator follows the established welding procedure. Unfortunately, however, the sources of welding problems are many, and may include problems relating to poor welder maintenance (e.g., worn contact tip, dirty gas cup, poor grounding), problems with the weld fixtures (e.g., misalignment, fixture cleanliness), problems relating to the welding robot (e.g., reprogramming of welding robots without consideration of the effects on weld parameters), automation fallibility (e.g., poor fit-up), procurement of low quality consumables, such as filler wire, or the degradation of the welding equipment itself Therefore, the failure to properly follow the established welding procedure can quickly result in an increased part rejection rate.
Another problem that is often faced in a production environment is that the system operator usually does not take the time to ascertain the underlying problem causing the defective welds. Instead, the problem is often corrected by simply varying certain readily adjustable welding process parameters until the problem goes away. While such a procedure may result in a short-term fix, repeated corrections may eventually cause the welding process parameters to drift so far out of the parameter space defined by the initial procedure that weld defects become difficult to diagnose and eliminate, resulting in higher defect rates than would otherwise be encountered by adhering to sound welding practices.
SUMMARY OF THE INVENTION
Apparatus for determining a quality of a weld produced by a welding device according to the present invention includes a sensor operatively associated with the welding device. The sensor is responsive to at least one welding process parameter during a welding process and produces a welding process parameter signal relating to the at least one welding process parameter. A computer connected to the sensor is responsive to the welding process parameter signal produced by the sensor. A user interface operatively associated with the computer allows a user to select a desired welding process. The computer processes the welding process parameter signal produced by the sensor in accordance with one of a constant voltage algorithm, a short duration weld algorithm or a pulsed current analysis module depending on the desired welding process selected by the user. The computer produces output data indicative of the quality of the weld.
Also disclosed is a method for determining a quality of a weld produced by a welding devices that comprises the steps of: Determining a desired welding process by selecting from among a constant voltage welding process, a pulsed current welding process, and a spot welding process; selecting a welding process algorithm based on the desired welding process, the step of selecting a welding process algorithm comprising the steps of selecting a constant voltage algorithm if the desired welding process is determined to be the constant voltage welding process; selecting a pulsed current analysis algorithm if the desired welding process is determined to be the pulsed current welding process; and selecting a short duration weld algorithm if the desired welding process is determined to be the spot welding process; detecting the initiation of a welding process; monitoring at least one welding process parameter during the welding process; processing the at least one welding process parameter in accordance with the selected welding process algorithm to assess the quality of the weld; and producing a user-discernable indication of the quality of the weld.
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“How to Measure Success,” N. A. Technologies Company (Advertisement).
Carlson Nancy M.
Clark Denis E.
Johnson John A.
Kenney Kevin L.
Reutzel Edward W.
Bechtel BWXT Idaho LLC
Dahl & Osterloth LLP
Shaw Clifford C.
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