Flexishaper Increases High Speed Laser Welding by >50%
Holo/Or‘s latest innovative development is enabling a full range adjustable distribution of the power ratio between the zero order and a surrounding concentric ring. The innovation was validated in cooperation with Holo/Or’s sister companies SCANLAB and BLACKBIRD and proved to increase weld speed from 45 m/min to up to 70 m/min!
Adjustable diffractive beam shaper concept
The concept of adjustable laser beam shapers, using diffractive optical elements, was first introduced by Holo/Or in a scholarly article from Feb. 2019. Holo/Or presented a semi-dynamic beam shaper using a single passive diffractive optical element (DOE).
The concept suggests that a single DOE can be divided into sub-apertures, each designed to generate a different optical function. Thus, when rotated, mounted on a moving stage, or combined with a beam steering device, the single passive DOE can provide a robust and easy-to-integrate optical solution for systems and applications. This new solution replaces an otherwise complex and expensive laser or a dynamic beam shaper.
A typical application for this new development is high-speed laser welding. Thanks to the recent availability of affordable high powered lasers, power is practically no longer the limiting factor for welding speeds, and instead other physical phenomena which previously where a “non-issue,” such as humping and undercut, become a dominant factor in determining the speed limit of the process.
These limitations on welding speed can be bypassed by using tailored distributions, generated by a beam shaper, such as a ring with a central point, coupled with controlled, dynamically variable power ratio between the ring and the spot. While such distributions can be achieved by a dynamic beam shaper, often the laser damage threshold (LDT) of such components is unsuitable for high power applications. Therefore a high LDT, passive component such as a DOE is preferred. However, the need for tunability in process development often poses a challenge to DOE use. The Flexishaper module solves this challenge.
Flexishaper full range ring-to-spot adjustable power ratio module
The ring-spot adjustable laser beam shaper concept was further developed beyond the original concept of sub-apertures and released as the Flexishaper module in May 2021. The Flexishaper module consists of two identical beam shaper DOEs. When rotated against one another, the output power distribution transitions continuously from 100% of the power at the zero order (ZO) to ~80% of the power in a concentric surrounding ring, with ZO almost 0%. Due to being a full beam shaper, with no sub-aperture clipping effects, this device is suitable for use with both single-mode and multimode laser beams without any degradation of spot quality.
This device was used in a test setup by HOLO/OR’s sister company BLACKBIRD along with SCANLAB’s 3D scanner system. The device proved to overcome the humping and undercut issues in high-speed foil welding of fuel cells, enabling an over 50% increase in weld speed with < 1 kW single mode laser. Thus this solution provided a cost effective and robust solution to a demanding beam shaping application.
Top: Severe humping effect caused by a Gaussian spot at high-speed foil welding; Bottom: The clean weld with no humping effect created with the same power and speed after Flexishaper integration. Courtesy of BLACKBIRD.
Flexishaper is a module designed for process developers. It enables them to find the optimal working ratio of power distribution between the central spot and the surrounding ring for each specific process. Once that ratio is determined, HOLO/OR can produce a single, custom DOE that will generate that same specific optimal power ratio. This provides an even more cost effective and easy-to-integrate solution into the final system, thus requiring absolutely no moving parts and no failure points.
Flexishaper DOEs are made of pure fused silica, offering a robust solution with high LDT and high transmission efficiency. These components can be customized to accept large beams (2’’ optics) often used in multi-kW laser systems.
For more information, contact Holo/Or.