USP is a reference to the length of light pulses, when they have a duration lower the 10-9 second also known as Nano seconds. Pulse lengths above that are commonly referred to as Short-Pulse (SP) and the distinguish between the two, become relevant when you look at the advantages the shorter pulse lengths (USP) offers when laser processing.
USP is a reference to the length of light pulses when they have a duration below 10-9 seconds, also known as nanoseconds. Pulse lengths above this are commonly referred to as Short-Pulse (SP), and the difference between the two becomes relevant when looking at the benefits that the shorter pulse lengths (USP) bring to laser processing.
USP, with Femto (10-15 seconds) as the currently shortest pulse length commercially available, do in no way replace or render longer pulse lasers obsolete, but offers some unique additional features to those of SP lasers. But for many tasks SP lasers remain the preferred solution, with its often faster and more cost efficient capabilities, while offering precision and quality, close to that of USP. This combined with postprocessing, can counter some of the advantages USP offer.
1. So what's the hype about...
In layman's terms, USP takes over where SP lasers leave off, pushing the boundaries of what can be achieved with laser machining. And much more than SP, it elevates laser machining as a superior technology for high-precision manufacturing in cases where punching, EMD, etching or other technologies might otherwise seem like alternatives.
In short, the main difference is that the shorter pulse length ensures material evaporation rather than melting.
This is in contrast to the SP cutting process, where only a percentage of the material in the cut is vaporized and the rest must be removed with high-pressure gas.
But this seemingly small difference leads to a number of benefits:
1.1.1 Machinability on a wider range of materials
While SP-based technologies can be used to process a range of materials, they typically become very material-limited when in a specific setup/machine. USP/Femto on the other hand, with its short pulses and high energy intensity, not only processes a wider range of materials, but becomes far less limited by a specific setup. A USP Femto-based machine therefore typically processes a wide range of materials well - such as metals, elastomers, glass, ceramics, sapphire or even diamonds - in the same setup. This provides a high degree of flexibility to meet specific needs and the ability to process multiple or layered materials in the same process.
1.1.2 Minimal heat-affected zone (HAZ)
While high-precision, small spot, low-energy SP lasers add very little heat and minimal HAZ to a metal, USP lasers take this a step further. The absence of a traditional melt zone reduces heat build-up even further, which is why the technology is also referred to as cold working. As a result, the technology limits the traditional need to cool the material using high-pressure gas, which from a machining standpoint is the "evil" that creates many of the challenges SP cutting faces. So, in addition to the ability to process even thinner or heat-sensitive materials, the lack of high-pressure gas and heat build-up contributes to the precision and capabilities of USP lasers.
1.1.3 Burr-free cutting edges
It is the melt zone in SP cutting that leads to the risk of solidified slag/burrs along the cut. The absence of this in USP cutting means that the cut is closer to the actual spot size and metal spatter on surfaces under or around a cut is reduced. While SP cutting can counteract this through finishing, USP offers a particular advantage in places where slag/spatter finishing is limited. For example, tight spaces along the cut, holes or inside a pipe.
1.1.4 Higher accuracy
Precision and quality in a laser process is defined by many factors other than just pulse length, but because USP delivers its energy in far more pulses per second, the energy needed to penetrate a material can be transferred in a much smaller spot size. Combined with the above features, USP lasers offer precision and quality that is superior to SP lasers.
On Covis solutions, depending on the job, this can mean cuts measured in single-digit micrometers.
1.1.5 Surface texturing
With USP lasers, different properties can be built into a material surface, adding features such as changing friction, changing roughness, introducing hydrophobic properties and creating diffractive optical properties. Femtosecond laser enables this restructuring of surfaces through its high precision with minimal impact on HAZ.
1.1.6 Micro machining
The USP's ability to perform ablation means it can perform micromachining. For example, a groove, recess or slot in a pipe that would otherwise require Swiss Turning or milling can now be laser cut using only the laser - without cutting tools.
1.1.7 Laser-generated cutting edges/cutting edges
By combining and utilizing the strengths of Femto laser machining, the technology makes it possible to generate cutting eggs directly in the cutting process, where SP technology would require a subsequent grinding process. This is particularly useful when machining tubes or needles where there is a need to penetrate skin or collect tissue or fluids for biopsy samples.
Talk to Covi Precision about how this or other technologies can benefit your needs, or explore the possibilities further on our website.
Disclaimer: This article only addresses pulse length or USP/Femto as a term, which is only a fraction of the factors that make up a "laser processing solution".
