Laser plastic welding: measuring your laser is the key to quality assurance
Monday, March 09, 2020
Laser welding is fast becoming the preferred technique for joining various materials together, and plastics are no exception.
Superior weld quality, higher quality control, and the ability to join complex shapes are just some of the features that make laser plastic welding a standout option for numerous industries.
However, while this method offers numerous benefits over other joining techniques, it is essential to ensure that your equipment is well-maintained and properly calibrated for optimal performance.
The weld seam between adjoining plastics is dependent on the quality of your laser’s output. Due to the sensitive operation of some plastic welding techniques, your beam’s properties must be within the right operating parameters to guarantee a successful weld.
During through-transmission welding, for example, your laser’s wavelength should be within the appropriate range to ensure that it can freely pass through the upper transmissive layer while being absorbed by the lower layer.
Appropriate power readings must also be maintained during welding. Power levels ranging from 1W to 100W are typically needed depending on the type of material, its thickness, and the desired weld speed. For a given application, if your power outputs are too low, weak fusion and cold cracks can be formed.
Another crucial laser property that you need to consider during plastic welding is power distribution. This is especially critical during simultaneous welding procedures. During this method, the entire weld seam is heated at the same time, thus requiring even distribution of power across the joint.
One of the most common issues that can affect plastic welding quality is the reduction of your beam’s intensity.
As the laser passes through the polymer, beam scattering can occur due to the presence of crystalline zones and glass fibers. Pigments, coloring agents, and other compounds also absorb some of the beam’s energy as it travels to the weld seam.
As such, your welding laser needs to be calibrated to account for these losses to ensure that there is enough intensity at the joining horizon.
Similar to metal welding, dirty optics can also harm your laser’s power output. Over time, laser optics can accumulate dust and other contaminants. This can result in thermal distortion, which can affect the quality of the laser’s focus and penetration power.
By measuring your laser’s output characteristics, you can determine if your equipment possesses the required power or if calibration and maintenance are needed.
Efficient laser plastic welding depends heavily on the quality of your laser’s output power. Routine calibration should, therefore, be carried out using the appropriate power sensor for your application.
These sensors can help you determine if your laser can deliver sufficient heat to the weld seam between the adjoining plastics.
For higher powered lasers, such as those used in clear joining technology, measuring your beam’s intensity ensures that they do not cause undue damage to your optics and other components.
Additionally, for high-precision applications, where small spot sizes are crucial (some as little as 2 microns), a beam profiler can be used to measure the spatial distribution of the power across the beam. This ensures that the required resolution and precision are obtained.
Laser quality plays a crucial role in the success of your plastic welding operation. It is, therefore, essential that your equipment is frequently measured to ensure optimal performance. Avoid costly weld failures by investing the right power detectors and beam profilers today.