Good welds are critical for the safety and integrity of a structure and affect the crashworthiness of a vehicle, so welds must be inspected upon completion. New welders are trained to inspect their welds after they have completed a job; however, it is challenging and time-consuming for welders to inspect all of their completed work for defects.
Weld defects can be defined as the irregularities in a given weld due to incorrect welding techniques or incorrect welding patterns. Many different defects can arise during the welding process. Some of the most common external welding defects are cracks, undercuts, burn-through, porosity, spatter, and overlap.
Defects can be present at the surface of the weld material or the affected heat zones on the joined materials.
Even brand-new cars are not immune to weld defects. In another recall case that affected over 110,000 vehicles, the improperly welded bushing housings and joints could lead to lower control-arm separation. This error could lead to catastrophic consequences for the drivers and vehicles involved.
In another very high-profile recall that involves a multi-billion-dollar streetcar contract, one of the biggest cities in North America had to send more than half of their new streetcar orders back to the manufacturer after discovering more than 20% of the body structures suffered from weld defects.
The above three examples are just some of the weld defects that have been missed in the initial quality control process and were passed downstream, resulting in costly recalls and safety hazards. These oversights make 100% in-line weld inspections even more critical to ensure high-quality, defect-free deliveries.
Quality assurance weld inspectors use different methods for inspecting the weld, including visually inspecting the weld, and a variety of tools, including magnifying glasses, flashlights, handheld gauges, tape measures, and calipers. The tools to be used by the weld inspector depends on the weld in question and the type of defect. These tests are only as reliable as the workers performing them. If the worker fails to complete a test or completed a test improperly, the reliability of the weld can be called into question, causing a big headache for the company. Weld inspection is often a tedious process that calls for a keen eye for detail and patience; inspectors can be responsible for inspecting hundreds to thousands of welds per shift.
Individual inspection is subjective to each inspector, making it very hard for manufacturers to ensure that each defect is caught. With an automated inspection solution, defect detection is based on measurements and mathematical formulas, ensuring that all defects that fit a certain set of criteria are caught before they can be passed downstream in the production line.
New methods have been developed that make weld inspection much easier for manufacturers who produce large numbers of products. Bluewrist Inc. offers a 100% in-line weld inspection solution. This solution uses a 3D profiler or 3D snapshot sensor to capture detailed surface characteristics of the weld. The weld can be inspected fully or broken down into individual sections for analysis and comparison against fabrication blueprints to guarantee the weld conforms to the specifications.