Weld Inspection of Electron Beam and Laser Welds

EB Industries performs all weld inspection in-house utilizing the latest inspection technology operated by AWS certified weld inspectors. This is an essential final step in the making of a part.

There are many process variables involved in electron beam and laser beam welding. Weld location, width, and depth can be adjusted to within the 0.001” range, the amount of energy or heat that is applied to the weld area is precisely controlled, feed rates and the weld environment must be controlled and monitored, and if this is all done correctly, the resulting weld is remarkably strong and durable.

However, the complexity and variability involved means that ensuring a high level of weld quality requires a stringent inspection process, which is what we have in place at EB Industries.

Weld Inspection Process

Weld inspection of laser and electron beam welded parts generally follows three distinct paths: visual inspection; destructive testing; and non-destructive testing (NDT).

Visual Inspection involves looking at a weld with the naked eye and/or with some level of magnification. Typically, our inspectors are checking for cracks, pits, surface pores, undercut, underfill, missed joints, and other aspects of the weld.

Visual inspection is limited to the surface area of the weld that is visible to the inspector, which means something like depth of penetration cannot be determined unless the weld is a full penetration weld and you can view it from inside the assembly. Hence, destructive testing is often required to further examine the quality of the weld.

Destructive Testing involves physically cutting and sectioning the part to determine the internal characteristics of the weld. Typically, either a production part is cut or a representative sample is made that embodies the exact characteristics of the joint. Destructive samples are usually taken at the beginning of the job to make sure the weld parameters are correct for the lot. Samples can also be taken at intervals during the production process or at the end of the run.

Destructive testing samples are precisely cut, machined, ground, and polished to a mirror-like finish. An acid etch is then applied to visually bring out the weld, and the sample is then inspected under a microscope. This inspection can determine depth of penetration, width of weld, as well as reveal cracks, pores, and other anomalies inside the weld bead.

Non-Destructive Testing as the name implies, does not destroy the part, so theoretically every part could be examined in this manner, and this is usually the case if NDT is required by the specification.

NDT generally consists of dye penetrant inspection and/or x-ray inspection.

In dye penetrant inspection, a special dye is applied to the part to identify cracks and other surface anomalies. This method is limited in it can only identify problems on the surface of the weld.

An X-ray inspection results in the most comprehensive view of what is going on inside the weld. Porosity in particular can be clearly seen in an x-rayed part.

Every assembly has different requirements, and it’s important to understand the nuances of each type of inspection to develop an inspection regimen that will consistently lead to high quality parts within the bounds of the requirement. For example, a low risk of failure part may simply need visual inspection, while a part destined for space – where failure of could be catastrophic – demands a much higher level of inspection.

Microscope Technology: Stereoscopic or Better

Quality microscopes are at the heart of any inspection. While some weld issues can be seen with the naked eye, the majority require magnification to see. Our shop is laid out with dozens of stereoscopic microscopes located in key areas that allow strategic inspection of parts as they’re processed. Typically, every EB welding and laser welding station is equipped with microscopes adjacent to the welder.

Stereoscopic microscopes not only magnify but also render depth. The ability to view parts with depth — seeing the weld bead three dimensionally — can make a big difference in determining and diagnosing weld issues: what might appear as a surface scratch in 2D could actually be a crack when viewed in 3D, as an example.

All inspection scopes at EB Industries have a minimum magnification of 20x , even though most specifications only require 10x, because we’ve found higher levels of magnification result in better inspections and consistently better parts – you can’t find a problem if you can’t see a problem.

Digital Microscopy

Digital microscopes are a world beyond traditional stereoscopic microscopes and allow our inspectors to better examine parts, take detailed pictures and measurements and provide our customers with timely, detailed documentation.

Our Keyence VHX-900F Microscope takes inspection into an incredible level of detail and precision. In addition to all the basics one expects from a digital microscope — high magnification, auto lighting, auto focus, photography, dimensional annotation on the photo, and the ability to import images into an inspection report, the Keyence also has autofocus stitching and adaptive lighting. These features make the Keyence a game changer.

Autofocus and Image Stitching

At high levels of magnification a microscope has a very limited focal plane, which makes it difficult to see the entire weld in continuous focus. The Keyence autofocuses across the various focal planes, shooting a series of high resolution digital snapshots that are then stitched together at pixel level into a composite 3D image of the part or the weld. The final composited image can be digitally rotated, enlarged, sectioned and otherwise thoroughly manipulated and examined across 3 axes. Additionally, as the Keyence focuses across the various planes of the workpiece, it stores depth information that is precisely correlated to points on the image. The result is that not only can our inspectors find microscopic anomalies on a weld or part, they can accurately measure those anomalies down to microns. Is it a scratch or a crack? The Keyence allows us to answer that question with a number.

Adaptive Lighting

Often a weld sample, especially one sectioned for destructive testing, is highly machined and reflective, resulting in glare, which washes out details and complicates the inspection. Further, the visibility of surface textures is highly dependent on the angle of incidence of the light illuminating the part or weld. The Keyence solves these issues with a very effective glare reduction algorithm and precise control of light direction in terms of intensity, direction and color temperature. The weld inspector can adjust the lighting as the part is initially fixtured for the inspection, and, amazingly, the lighting can be further adjusted AFTER the digital image is captured. So, not only can the image be moved and rotated, the angle, intensity and color of the light can be fully controlled after the fact to further reveal details and textures. The result is the most comprehensive inspection of precision welded parts in the industry.

This new system provides such high quality magnified images of our welds, I don’t know if we can ever go back to the old way of viewing welds. The system easily provides views and data about the most minute details of a weld, which ultimately helps us identify and avoid potential problems later in production.

– Ray Bzibziak, engineer Cobham Mission Systems in Orchard Park NY

Sectioning Lab

EB Industries is unique in that we have a fully equipped sectioning lab on-site, in close proximity to our shop, operators and inspectors. Hence, our inspection process is tightly integrated into our manufacturing process.

Our sectioning lab has an array of different equipment in order to make high quality cross sections in an efficient manner, including molds, potting compounds, saws, grinders, wet sanding disks, and polishing wheels. The lab also contains a full complement of acids and chemicals appropriate to etching a wide range of specific materials. Regardless of the metallurgy involved, we can treat any part such that details, such as the heat effected zone, clearly stand out for inspection and analysis.

The capability to create high quality cross sections in-house provides many benefits to our customers in terms of quality, processing speed and cost effectiveness. During weld development we can perform inspections synchronously with weld development iterations, which speeds up the refining of the part and the weld. During production runs we can monitor parts according to whatever schedule is specified without compromising the efficiency of the production run.

Inspector Qualifications

EB Industries’ inspectors are certified to AWS QC1, which is the specification published by the American Welding Society for certification of welding inspectors. Additionally, all our inspectors go through significant internal training and constant testing — again, we endeavor to operate over and above the specifications.

Finally, the inspection processes we follow are all documented in a quality a comprehensive management system certified to AS9100D / ISO 9001:2015. These same processes are audited regularly as per our NADCAP accreditation for welding.