Laser Plastic Welding
Laser Plastic Welding as an Industrial Joining Technology
Definition and process principle
Laser plastic welding is a precise joining process for thermoplastic components. Laser energy is introduced into the joining zone to create a controlled melt layer and a strong material bond under pressure. The process is used when clean weld seams, repeatable quality, reliable sealing and automation-ready production are required.
For project managers and buyers, laser plastic welding is especially relevant when a joining process must avoid particles, adhesives and mechanical fasteners while remaining suitable for series production.
Laser transmission welding
In laser transmission welding, the upper joining partner is transparent to the laser wavelength while the lower joining partner absorbs the energy. The absorbing part heats up and melts at the interface. Heat transfer and joining pressure create the weld seam between both components.
For a deeper process explanation, see laser transmission welding.
Overview of the Process
Joining parts: Precise laser welding of transparent and absorbing componentsrnrnIn laser plastic welding, two different joining parts are combined: a transparent joining part (LT) and an absorbing joining part (LA). The transparent part allows the laser energy to pass through, while the absorbing part takes up the energy in a controlled way. The components are pre-assembled and fixed in the required assembly condition.rnrnIn an overlap weld, the joining parts are pressed together with defined force. The laser beam passes through the LT part and hits the welding rib on the LA part. The rib is directly melted by the laser. Due to heat transfer, the LT part also melts in the contact zone, creating a strong, tight and durable material bond between the two joining parts.rnrnThis principle is suitable for all standard applications – from small to large parts, complex welding geometries and microfluidic components to radial shapes – and offers a precise and reliable joining solution for plastic assemblies.
Transparent joining parts: Precise laser welding without absorbing additivesrnrnIn this laser plastic welding process, two transparent joining parts (LT1 and LT2) are combined without the use of absorbing additives. The components are pre-assembled and positioned in the defined assembly condition.rnrnIn an overlap weld, the transparent joining parts are pressed together with a defined force. The laser energy passes through both parts, a controlled portion of the energy is absorbed in the material and melts both joining partners in the contact zone. The molten material combines and forms a homogeneous, strong weld seam.rnrnThis principle is particularly suitable for applications where absorbing additives are not permitted, for example in sensitive, highly regulated or purity-critical plastic assemblies.
Absorbing joining parts: Flexible laser welding for non-transparent materialsrnrnIn this process, two absorbing joining parts (LA1 and LA2), each equipped with a welding rib, are positioned in separate nests. The laser energy is applied directly to the welding ribs and melts both ribs in a controlled manner. Once the defined melt state is achieved, the laser is switched off and the joining parts are pressed together with a specified force. In the contact zone, the molten material combines and forms a strong, durable weld.rnrnThis principle is particularly suitable for applications where transparent materials cannot be used, for example carbon-fibre-reinforced plastics, as well as for large components, complex welding geometries and the implementation of new material combinations.
Process Variants, Systems and Inspection
Contour, quasi-simultaneous and simultaneous welding
In contour welding, the laser follows the weld path. In quasi-simultaneous welding, the contour is scanned repeatedly at high speed so the seam heats almost simultaneously. Simultaneous welding heats the complete seam in one step. The best variant depends on geometry, cycle time, weld requirements and investment target.
EVOSYS designs the laser process, optics, clamping concept and automation around the application.
Industrial systems, modules and inspection
Industrial laser plastic welding combines laser source, optics, clamping, motion, control system and process monitoring. Depending on the production target, EVOSYS provides process modules, standard systems, special systems, software and inspection systems.
Color selection has a direct impact on the feasibility and process window of laser plastic welding. Dark and absorbing color combinations such as unfilled + black or black + black are comparatively easy to weld, as they absorb the laser energy efficiently and create a stable melt layer. With colored parts (colour + black, colour 1 + colour 2 or colour 1 + colour 1), the interaction between pigmentation and laser wavelength becomes more complex and requires adapted process parameters and material selection.
At the upper end of the difficulty scale are transparent + transparent and especially white + white combinations, where absorption is very low and the laser beam largely passes through the material. With its specialized process know-how, suitable laser sources and optimized additives, Evosys reliably realizes all these challenging color combinations in industrial laser plastic welding.
Materials, Absorbers and Part Requirements
Materials and absorbers
Many engineering thermoplastics can be laser welded if transmission, absorption, melting behavior and part design are suitable. Key factors include optical properties, additives, color, wall thickness, joint geometry, low gaps, stable clamping and a repeatable joining surface.
EVOSYS evaluates these factors early with material tests, welding trials and process window studies.
Transparent and absorbing joining partners
Standard applications often combine a laser-transparent upper part with an absorbing lower part. For more demanding tasks, EVOSYS offers additional technologies: EvoClear for transparent joining tasks and Evo2Step for applications with two absorbing joining partners.
The right approach depends on material, optical behavior, seam requirements, tolerances and production targets.
Guideline Laserwelding
Download documentApplications, Feasibility and FAQ
Typical applications include housings, sensors, actuators, medical cartridges, microfluidic structures, electronic assemblies and consumer product components. Laser plastic welding is often selected when particles, vibration, adhesives or mechanical fasteners would create technical or quality risks.
EVOSYS supports application design, trials, prototypes, feasibility studies and production system concepts.
Many thermoplastics are suitable. Transmission, absorption, additives, melting behavior and joint design determine feasibility.
Laser welding is often preferred for sensitive components, low-vibration joining, clean seams and controlled automation.
Yes, under suitable material and process conditions, for example with EvoClear.
EVOSYS reviews parts and materials, defines test objectives, performs welding trials and evaluates weld strength, sealing performance, visual quality and production readiness.
Would you like a personalized consultation?
