Welding Procedures
Welding Procedures tests how a robotic welding operation is documented, qualified, and controlled. It is the paperwork domain that keeps the arc legal: what a WPS must contain, how it is supported, and what change forces a return to the test shop.
What a WPS contains
- Process and variant, base metal specification and grade, thickness range qualified.
- Joint design and details, including root gap and groove angle.
- Positions qualified, and progression for vertical work.
- Preheat and interpass temperature ranges.
- Filler metal classification and size, shielding gas composition and flow.
- Current type and polarity, amperage and voltage ranges, wire feed speed, travel speed, heat input range.
- Cleaning, back gouging, and technique: stringer or weave, weave width, torch angles, CTWD. For robotic work the WPS should also state work angle and travel angle tolerances, because those drive fusion.
Qualification path
A proposed procedure is written, a test coupon is welded and tested to the code, results are recorded on a PQR, and the WPS is issued from that record. Prequalified joints and procedures skip testing only where the code explicitly allows it.
Essential variables and change control
Changing process, filler classification, polarity, position, or preheat beyond the qualified range requires requalification. Changing a nonessential variable, such as gas flow within a stated band, does not.
Worked example
A WPS qualified on 3/8 in plate at 26 V and 210 A is asked to cover a 1/4 in production part at 24 V. Thickness qualification is a range tied to the coupon, and thinner material usually falls inside it, but voltage is controlled by the procedure. If the WPS states a voltage range that includes 24 V, the change is an adjustment within the procedure; if it states 26 V with a narrow tolerance, a revision with supporting data is required. The answer depends on the stated range, not on operator experience.
Traps
Treating the WPS as guidance; forgetting that travel speed and heat input are linked and both must be in range; ignoring interpass temperature on multipass robotic work; assuming a procedure qualified in one position covers all positions.