Combining Laser Technologies to Address Battery Yield Challenges

Many manufacturers still rely on traditional laser weld monitoring (LWM) tools to ensure quality. But these systems often don’t measure the weld directly or even accurately. This introduces uncertainty into the quality assurance process that leads to higher scrap rates while still inevitably failing to prevent bad products from going out the door.

To address this problem and continually advance the world’s battery manufacturing capabilities, IPG Photonics has combined on-the-fly (OTF) welding with our own, patented, real-time, inline laser weld measurement system. Used together, these technologies deliver the speed required for cost-effective, high-throughput battery production, as well as the measurement capabilities needed for accurate weld validation. This integrated approach enables higher yield, lower scrap, and greater confidence in weld integrity without slowing down the process.

LDD uses a low power, near infrared measurement beam directed through the same optics as the welding beam. Because the LDD beam is coaxial with the welding beam, the measurement and process beams hit the workpiece in proximity. Acting like a mirror, the metal work piece reflects some of the LDD light back into the optics. This returned light is used to accurately measure the distance to the reflecting surface through interferometry.

During keyhole LBW, the LDD beam is directed into that cavity and reflects off its bottom. This permits direct measurement of the keyhole depth, typically to an accuracy of within a few microns. Importantly, LDD is even capable of measuring the narrow, high aspect ratio keyholes produced by single mode lasers. All this distinguishes LDD from other weld monitoring methods that utilize a proxy signal – like heat, welding plume, or sound – and then attempt to approximate what is actually happening in the weld zone.

The LDD optics themselves also contain a galvo scanner which can rapidly move the measurement beam independent of the process beam. For typical inline weld measuring applications, the LDD beam is set to slightly trail the process beam and continuously monitor keyhole depth. But it may also be directed to the top surface of the work piece to maintain a depth reference.

Scanning the LDD measurement beam allows it to measure other important weld parameters besides keyhole depth. These include material height, seam position, finished (longitudinal) weld seam height, and transverse weld profile.

As a result, LDD enables manufacturers to transition from statistical monitoring to direct measurement. It provides the ability to validate every single weld individually, in real time.

This can have a huge cost and quality impact as has been demonstrated by many battery manufacturers already using LDD technology. Underpenetrated welds are identified as soon as they occur and can be flagged for immediate or subsequent rework. Welds with overpenetration can be noted. Thus, the problem of false scrap is virtually eliminated. It allows the manufacturer to decide if the part should be passed or scrapped right away – before further value is built into it.

IPG was uniquely positioned to engineer this solution because we design and manufacture the full tech stack for this system in house. We produce fiber lasers, of course, but also scanning heads, motion systems, control software, and the LDD system itself. We also build and integrate these components and technologies into many of our turnkey and custom sub-systems, full systems, and production lines.

This vertical integration gives us two key advantages when developing unique laser solutions. First, we have the experience required to completely understand and characterize problems before we identify solutions. Second, we have the development resources and engineering control over all the system components necessary to effectively implement them.

With these capabilities, IPG designers were able to develop a solution which acquires high-quality LDD data at production speeds, and which synchronizes beam steering at the level of precision required for OTF + LDD to function reliably on the line. We also developed the calibration routines, correction algorithms, and support tools necessary to maintain that precision over time despite heat, vibration, contamination, and wear.

Getting Started with a Laser Solution

IPG technologies like on-the-fly welding and real-time laser weld measurement are key components used in high productivity laser welding solutions. Interested in learning more about an IPG laser solution can benefit your operation?

Getting started is easy – send us some sample parts, visit one of our global application labs, or just tell us about your application.