Quality Control In Welding: Ensuring Consistency and Accuracy with 2D/3D Laser Profilers
Welding is one of the most important and common fabrication processes, and it uses heat to melt and fuse two parts (typically metals) together. Metal welding involves melting the metal and adding a filler to form a pool of molten material, which then cools to form a joint.
However, welding isn’t as simple as just pushing filler material into a pool of molten metal at the joint itself. It’s a controlled process affected by numerous factors, and failure to maintain adequate control over the process usually results in sub-par joints, which pose their own risks.
Most notably, poorly formed joints can contain cracks and fractures which compromise the structural integrity of the welded component. This can lead to a catastrophic failure when the weld is placed under stress or load, potentially causing accidents or injuries.
These reasons underscore the need to ensure the reliability, durability, and safety of welded structures and components. In this article, we’ll discuss the importance of quality control (or QC) in welding and how the consistency and accuracy of these processes can be improved by using 2D/3D profilers.
Understanding Welding Quality Control
Unlike quality assurance — a proactive process that focuses on preventing defects or issues in welding — quality control is a reactive process that focuses on identifying defects in welded joints. It’s a critical process that ensures all welds meet the specifications and standards required by the product or structure.
As such, welding QC relies on inspection and testing to ensure that the welded joints meet specifications. Tests for tensile strength, bend, hardness and impact are rare, but weld inspections are quite common.
To elaborate, weld inspections involve looking for surface defects on the weld beads, such as cracks, incomplete fusion, undercutting, porosity, or excessive spatter. In most cases, these inspections are manual and typically involve dye penetrant testing, magnetic particle testing, ultrasonic testing, or radiographic testing.
Ultimately, weld inspection is a process that identifies defective welds so they can get reworked, with the end goal of maintaining a part’s structural integrity.
The Importance of Welding Quality Control
As stated, QC in welding plays an important role in ensuring the production of reliable welds. Most jobs typically come with certain welding standards and compliance requirements. More often than not, customers specify more stringent quality control requirements than those dictated by welding standards… therefore making the QC processes mandatory. This is particularly true when welding pressure vessels, structural steelwork, lifting equipment, or any kind of equipment whose use would imply safety precautions.
More critically, failure to adhere to QC requirements could have dire safety and legal consequences, leading to contractual issues and legal penalties. Therein lies the importance of QC: it ensures adherence to specific standards and requirements and offers protection against legal liability in case of disasters.
As such, proper quality control is a good way to show due diligence during the fabrication process. Recording and documenting the state of a product at its completion is incredibly important to counter any claims of defective products.
To summarize, welding quality control is important because it:
Maintains Consistency and Precision – Weld inspection systems (such as 2D/3D laser profilers) offer efficient and highly accurate ways to identify defects.
Ensures Compliance with Standards – QC ensures that the welds meet standards set by the regulatory bodies, industry-specific guidelines, or customer requirements.
Quality Control Methodology
The inspection methods used during QC mostly depend on the specifics of the job or manufacturing process, e.g., welding compliance standard, class of weld, and other specifics. This is important because testing is usually categorized as:
- Destructive Testing (DT)
- Non-Destructive Testing (NDT)
Destructive Testing
Destructive testing, as its name implies, requires the physical destruction of a part to test the welded joint. In most cases, it involves sectioning the part and/or breaking the weld, and it’s most commonly used for Welding Procedure Specifications and welder qualifications. Some of the most common destructive tests are:
Macro-testing – Sections of the weld are polished, etched, and then inspected for any lack of weld penetration, porosity, lack of sidewall fusion, poor weld profiles or other potential defects.
Break testing – This type of mechanical testing examines root penetration on one-sided fillet welded joints. The broken surfaces are examined for any discontinuities.
Tension testing – A weld sample of specified dimensions is placed under increasing tension until the point of failure, ensuring that the weld is at least as strong as the base metal.
Bend testing – A reliable testing method for determining the ductility and strength of welded connections up to the point of fracture or failure.
Non-Destructive Testing (NDT)
Non-destructive testing implies testing methods that don’t physically damage or interact with the weld and are thus only carried out on the finished fabrication. Some of the most common NDT tests are:
Visual Scanning – Visual checks confirm that the welds, their location, and type are produced as per the project blueprint.
Visual Examination – Visual weld inspections check for visible weld defects.
Dye Penetrant Testing – Dye is applied to the weld and then physically removed to reveal cracks and other defects on the weld surface.
Magnetic Particle Testing – Magnetic particles are used to detect shallow subsurface discontinuities or other flaws in ferromagnetic materials.
Ultrasonic Testing – Sending high-frequency sound waves through a material and measuring the reflections. Great for detecting porosity, lack of fusion, and inclusions.
Radiographic Testing – Most commonly performed in pipeline constructions, this testing uses X-rays to examine the internal structure of the weld and identify flaws or defects.
2D/3D Laser Profiling – Laser profilers use laser light to scan weld beads for cracks and other defects. Due to their precision and accuracy, they’re often used in automated welding and welding QC.
The Role of 2D/3D Laser Profilers in Welding Quality Control
In order to understand how laser profilers can improve welding QC, you must understand what these sensors are and how they work.
2D/3D laser profilers are laser displacement sensors designed to measure the distance between the sensor and the target surface. They’re mostly used for height measurement and surface profiling in manufacturing and production lines, where they take continuous 2D scan lines and compile them into 3D surface profiles.
During the scan, the emitter in the laser profiler projects a laser beam onto the target surface and reflects the emitted light onto the photosensitive element inside the profiler. Depending on the type of the profiler, it will calculate the distance by either measuring the angle of reflection or the time of flight—the amount of time it takes for the light to reflect on the surface back to the sensor.
2D/3D laser profilers, like KEYENCE’s LJ-X8000 Series, are exceptionally accurate, down to the single-digit µm range, which allows them to detect cracks and surface imperfections that might otherwise be invisible to the naked eye.
The integrated, high-precision CMOS element captures 3,200 data points per profile, allowing accurate measurements and inspection of surface defects and detecting splatter, burn-throughs, etc. All of this data is processed and stored simultaneously, enabling subsequent, detailed analysis.
But their use isn’t tied to QC alone; laser profilers are also commonly used to guide welding robots, as they’re great for seam detection, course corrections, and subsequent inspection.
Thus, it’s safe to assume that laser profilers ensure enhanced welding quality control and quality assurance by facilitating welding precision and control. This level of QA and QC leads to consistent, high-quality, and high-strength joints that are crucial to the structural and operational integrity of a particular structure, part, or even part assembly.
Summary
Quality control in welding is crucial to the manufacturing and production process, as it ensures that the welds produced meet all the industry requirements and standards compliance, resulting in a higher-quality product.
2D/3D laser profilers, such as KEYENCE’s LJ-X8000 Series laser profiler, provide enhanced flaw detection, which significantly enhances inspection quality and, subsequently, the quality of the manufactured part.
For more information: www.keyence.com
