Introducing laser welding into medical device production is more than a technical upgrade: it’s a design, validation, and scalability journey. This article offers a roadmap for implementing the technology effectively and unlocking its full potential.

The Promise of Laser Plastic Welding

Laser plastic welding has matured from a niche research technique into a mainstream manufacturing technology for medical devices. It enables precise, particle-free seams that can handle complex geometries and maintain high biocompatibility. The process directs laser energy into the components with exceptional precision in both energy delivery and positioning, made possible by the inherent accuracy of laser technology. The absorbed energy melts the joint area, and the clamping pressure consolidates the parts. Because heat is localized, there is minimal thermal distortion and no particle generation, making it well-suited for devices such as microfluidic components, sensors, and housing assemblies. When properly implemented, laser welding can produce sealed, aesthetically clean seams and eliminate the need for adhesives or solvents.

That said, experience teaches us that adopting this technology involves more than simply purchasing a machine. Each project, part design, or device comes with its own specific challenges. While an initial feasibility test can quickly show whether the application is viable, getting the process running reliably in production requires a broader strategy. This includes thoughtful design, process development, automation planning, and quality control. To bridge the gap between concept and production line, medical device manufacturers can collaborate with experienced partners who understand this development process.

Starting with Design: The Foundation of Success

The project begins long before a laser ever fires. Designers and manufacturing engineers must collaborate to ensure the product is laser-weldable and determine the optical configuration to be used. Many polymers can be laser-welded, but success depends on matching materials with compatible melt temperatures and optical properties. Selecting polymers with overlapping melt ranges enlarges the process window and makes the production process more robust. Material suppliers can provide absorption and transmission data for candidate resins; however, real-world testing remains essential.

The Optical Strategy: Choosing the Right Laser Wavelength

Before jumping into joint design, one of the first critical decisions is the optical approach—choosing the most suitable laser wavelength to deliver energy to the weld seam. In some cases, the answer is straightforward. For example, laser through-transmission welding using a laser of approximately 1-µm wavelength is often a solid choice. This method works well when one part is transparent to the laser, and the other is highly absorbent. However, in certain applications, such as clear-to-clear welding, using a 2-µm wavelength laser may be necessary, since both materials allow a specific range of laser transmission and require a different absorption profile.

Beyond wavelength, the beam delivery configuration must also be considered. Factors such as the shape and size of the weld rib, the required precision, accessibility to the welding area, and the visual or mechanical requirements of the final part all influence this decision. For instance, a galvo system may be ideal for quasi-simultaneous welding when having a controlled welding collapse, while a fixed optic setup might be better for contour welding, where following a welding path that might not be accessible with a galvo.

Ultimately, the optical strategy chosen will directly influence how the joint should be designed.

Designing the Joint

Joint geometry plays a critical role in the success of a laser plastic welding project. The design must enable proper interaction between the laser and the materials, which varies depending on the optical configuration and the laser wavelength used. In most cases, the laser beam must pass through a transparent upper layer and be absorbed by the lower component. However, in other applications, such as when using lasers with a 2-µm wavelength, both materials may absorb the laser energy, allowing a clear-to-clear welding. Each approach influences the joint design strategy and must be considered early in development.

In addition to optical considerations, the design must support the selected welding strategy, whether it involves controlled collapse welding, contour welding, or radial welding. Features like the welding ribs are commonly used to guide controlled melting and deformation under clamping force. Their placement must not only allow proper laser access but also align with the areas where the tooling applies pressure. These contact surfaces should provide stable support, prevent unintended deformation, and ensure uniform force distribution across the joint.

Involving laser welding experts and equipment suppliers early in the design phase helps prevent issues that may compromise weld quality or production efficiency. Early collaboration allows for optimizing wall thicknesses, rib geometry, clamping contact surfaces, and material selection. Experts can also run optical simulations to validate laser transmission and support the creation of prototypes for early-stage feasibility testing.

DfM for Automation

Design for manufacturing (DfM) extends beyond the joint itself. Automated loading and unloading require fixturing features that permit pick-and-place robots or linear tracks to handle parts reliably. Assemblies with symmetrical shapes may need orientation features to prevent incorrect placement. These considerations should be incorporated into the design specification early to avoid expensive redesigns later.

Process Development and Control: Navigating the Process Window

Maintaining a stable process requires precise control of laser power, clamping force, and joint collapse. Without feedback, variations in part dimensions, laser absorption, or ambient conditions can cause under-welds (weak joints) or over-welds (burn marks, flash). Modern systems employ multiple sensors to monitor and adjust the process in real time.

Collapse and Force Control

In collapse control, the clamping fixture measures how far the rib collapses during welding. The laser remains on until a specified collapse distance is reached or until a maximum time elapses. This method compensates for some of the variations and ensures a consistent weld line. Sensors capture the collapse profile for each weld, providing traceability. Some advanced systems go further, monitoring the speed of collapse, identifying different phases of the weld, and comparing each weld in real time against reference patterns for dynamic validation.

Power Control Based on Temperature

In addition to closed-loop control for collapse and clamping force, laser power can also be dynamically adjusted in real time based on temperature feedback from a pyrometer. By setting a target temperature and an acceptable tolerance range, the system continuously regulates laser energy to maintain optimal melt conditions. In case the temperature drifts beyond the defined safe range, despite these adjustments, the system can flag a potential defect.

All these closed-loop controls for collapse, force, and temperature contribute to a highly stable process with low scrap rates and minimal variation, ensuring consistent quality in production.

Quality Control: Rejecting Defective Parts Early

Even with closed-loop control, unexpected issues can occur. A piece of dust may prevent proper contact, or a supplier may deliver parts with slightly different absorption characteristics. Inline, closed-loop quality control identifies problems before further value is added in downstream production processes.

Thermal Imaging and Vision

With thermal imaging, the weld quality can be verified by analyzing the heat distribution along the weld path immediately after welding. Inline systems like Lasentum’s Advanced Thermal Analysis (ATA) perform inspections using this thermal data to detect inconsistencies and ensure process reliability. These systems compare thermal profiles to reference patterns using vision-based algorithms, measure weld width and uniformity, and detect anomalies such as uneven pressure distribution or the presence of burrs. Because this method is non-destructive, it can be applied to every part on the line, enabling full-process validation. The system not only makes a pass/fail decision but also generates traceable data that can be analyzed statistically to monitor long-term process stability and identify early signs of deviation.

Vision systems, using cameras and image processing algorithms, inspect the weld seam when material properties allow. They can identify issues such as missing weld areas, inconsistent weld width, or overheating marks. 

Data Capture and Traceability

Industry regulations require traceability and process data logging. This is achieved by assigning unique part identifiers and recording key welding parameters like laser power, force, collapse, scan speed, and thermal data profiles. For example, Lasentum’s LaseWeld suite captures this data, compares it to spec limits, and exports it for analysis, helping identify root causes if failures occur.

Factory integration in environments like manufacturing execution systems (MES) also enables automatic recipe loading based on QR codes or RFID tags, ensuring correct settings for each part. Advanced systems support Industry 4.0 for full traceability and centralized process control.

Automation: From Cells to Automated and Scalable Lines

For scaling to be effective, the validated process must remain consistent across different setups. Whether integrated into linear production lines or stand-alone cells, using the same validated modules ensures process integrity. Centralized control systems should support both single and multi-unit configurations, enabling reliable and efficient scaling as production grows. 

The Route to Successful Laser Plastic Welding

Success depends on early consideration of feasibility, careful design of joints, and implementation of robust process control. Automation and modularity enable a smooth transition from prototypes to pilot lines to full-scale production. Advanced sensors and quality control systems identify defects in real time and ensure traceability for regulatory compliance. Partnering with experienced laser welding providers is essential to navigate the path and deliver a high-yield production process.

David Bosom brings over 23 years of experience in the laser industry, having worked in roles in R&D, marketing, and global product management. In recent years, he has focused on expanding his expertise within the medical devices sector during his time at Coherent Corp. Currently, David holds the CEO position at Lasentum LLC, a company specializing in industrial laser systems based in Houston, Texas.