Figure 1: Ablation with a traditional laser causes thermal damage, heating peripheral areas.

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Catherine McGee
5 years ago
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The ability to machine precision parts without heat has dramatic implications for micro manufacturing.

Manufacturers can now create finished parts in a single, stress-free step by eliminating the costly and time-consuming

This paper explains the technology behind heatless laser micromachining.

around the world make superior parts, faster and at a lower cost than conventional machining methods.

1 The ability to machine precision parts without heat has dramatic implications for micro manufacturing. No heat means zero damage to the material or the part during the fabrication process. Manufacturers can now create finished parts in a single, stress-free step by eliminating the costly and time-consuming post processing steps typically required to address the thermal effects that result from other laser or mechanical tools. This paper explains the technology behind heatless laser micromachining. Femtosecond laser-based technology, delivered as an all-laser precision manufacturing solution, is helping companies around the world make superior parts, faster and at a lower cost than conventional machining methods Raydiance, Inc. All Rights Reserved.Raydiance, Inc., the Raydiance logos, and all other Raydiance products or service names are trademarks of Raydiance, Inc. Raydiance products are covered by U.S. Patents ( Rev

Manufacturers are accelerating time to market for smaller, more cost-efficient parts and devices, taking design concept to final product at a rate faster than ever before.

challenges for traditional machining methods.

Post processing to remove thermal damage or achieve tolerances at these dimensions is painstakingly slow and expensive.

Femtosecond technology enables effective athermal ablation the ability to create precision features without introducing heat to the target.

2 Manufacturers are accelerating time to market for smaller, more cost-efficient parts and devices, taking design concept to final product at a rate faster than ever before. The materials involved in precision manufacturing bioabsorbable polymers, shape-memory metals, hard and brittle materials like glass, laminates and multi-layer composites create significant challenges for traditional machining methods. With increasingly complex designs and micron scale requirements, there is little tolerance for the side effects that are common with traditional laser and mechanical machining methods. Post processing to remove thermal damage or achieve tolerances at these dimensions is painstakingly slow and expensive. Industrial grade femtosecond lasers are the solution to today s micromachining challenges. Femtosecond technology enables effective athermal ablation the ability to create precision features without introducing heat to the target. Traditional laser ablation is fundamentally a thermodynamic event. For example, a continuous wave (CW) laser emits a steady stream of photons that are linearly absorbed by the target. The energy and its associated electric field create oscillations in the lattice electrons, but they are not intense enough to immediately break the atomic bonds and liberate the electrons from the target atoms. Instead, the oscillations impart heat to the target, which, in turn, leads to classic thermodynamic phase changes: solid to liquid to vapor. While the target atoms and/or molecules might be liberated, considerable heat transfers to the material surrounding the target causing unwanted collateral damage (Figures 1 and 2). Figure 1: Ablation with a traditional laser causes thermal damage, heating peripheral areas. Figure 2: This comparison of picosecond and femtosecond laser pulse widths illustrates the difference in energy delivery times during material ablation. The longer picoseconds pulses allow for thermal diffusion that causes collateral heat damage. In contrast to picosecond, nanosecond and CW lasers, femtosecond lasers can ablate material using an exclusively nonlinear process called optical breakdown. This is a highly confined ionization event rather than a diffuse thermally driven one. Precision Machining Without Heat pg 2

Figure 3: This comparison of laser sources demonstrates the potential thermal damage that can be imparted to

Light pulsed in the femtosecond regime less than one trillionth of a second causes the material to react quite

The brevity of the pulses generates a very intense electric field capable of stripping the target atoms of

The extremely high plasma pressure forces the condensed volume of ionized material to be ejected.

The result is that precision shapes and features can be machined without ever introducing heat to the target

The ablation process occurs through optical breakdown.

3 Figure 3: This comparison of laser sources demonstrates the potential thermal damage that can be imparted to metal material during laser drilling of micro holes. Light pulsed in the femtosecond regime less than one trillionth of a second causes the material to react quite differently. The brevity of the pulses generates a very intense electric field capable of stripping the target atoms of their electrons and creating a transient condensed volume of charged particles, i.e. a plasma. The extremely high plasma pressure forces the condensed volume of ionized material to be ejected. This plasma formation process happens much faster than thermal diffusion. The result is that precision shapes and features can be machined without ever introducing heat to the target (Figures 3 and 4). Figure 4: At left is an illustration of a femtosecond laser impinging on a titanium target. The ablation process occurs through optical breakdown. The time duration of the pulse is shorter than the thermal diffusion time, which means the part does not absorb heat and there is no thermal damage to the area surrounding the target. At right is an SEM image of a 92 µm hole machined in 830 µm thick stainless steel (400) with Raydiance s femtosecond laser solution. A human hair is in the foreground to provide scale. Precision Machining Without Heat pg 3

While the ablation process includes optical breakdown when using lasers in the picosecond and nanosecond regime, the longer pulse widths and durations exceed typical thermal diffusion times to add a

Figure 5: The vascular nitinol stent above was machined with a nanosecond laser. It exhibits thermal damage in the form of burrs and significant heat affected zone (HAZ) damage.

4 While the ablation process includes optical breakdown when using lasers in the picosecond and nanosecond regime, the longer pulse widths and durations exceed typical thermal diffusion times to add a thermal component to the ablation process. This results in substantial heating of the sample and subsequent damage as evidenced by the nitinol stent image (Figure 5) below. Figure 5: The vascular nitinol stent above was machined with a nanosecond laser. It exhibits thermal damage in the form of burrs and significant heat affected zone (HAZ) damage. This requires re-work and several post processing steps to clean up. Figure 6: A nitinol stent created with Raydiance s femtosecond all-laser solution was taken from machining direct to polishing, bypassing multiple honing and etching steps required in traditional processing. In contrast, a nitinol stent (Figure 6) machined with Raydiance s femtosecond solution demonstrates the precision achievable. Nitinol stents machined with femtosecond lasers can be taken directly to the final electro-polishing stage; bypassing multiple honing and chemical etch steps. Not only does the femtosecond all-laser solution dramatically reduce manufacturing costs, it ensures that there is no thermal damage to compromise the structural integrity of the part. Precision Machining Without Heat pg 4

Raydiance has developed the world s first industrial grade all-laser precision manufacturing solution a turnkey femtosecond-laser based system that can be programmed to machine any material or

Deployed on factory floors of Fortune 500 companies worldwide, manufacturers in the medical device, industrial, automotive and consumer electronics industries are rapidly adopting Raydiance s

Increasing yield to nearly 100 percent and reducing cost per part by more than 50 percent, femtosecond all-laser precision manufacturing solutions are quickly displacing conventional lasers, electric

5 Raydiance has developed the world s first industrial grade all-laser precision manufacturing solution a turnkey femtosecond-laser based system that can be programmed to machine any material or geometry with proven reliability and repeatability. Deployed on factory floors of Fortune 500 companies worldwide, manufacturers in the medical device, industrial, automotive and consumer electronics industries are rapidly adopting Raydiance s all-laser precision solutions to create finished parts in a single step with superior part-to-part consistency and production yields. Increasing yield to nearly 100 percent and reducing cost per part by more than 50 percent, femtosecond all-laser precision manufacturing solutions are quickly displacing conventional lasers, electric discharge machining (EDM), computer numerical control (CNC) and other mechanical equipment that cannot achieve specifications, part consistency or target geometries without expensive, time-consuming post processing steps. Figure 7: Finished edge quality and strut-to-strut consistency in nitinol stent (left) demonstrates Raydiance s one-step all-laser precision processing. A Gasoline Direct Injection (GDi) fuel injector nozzle (center) is one of 6.8 million parts produced by a leading automotive manufacturer using Raydiance s R-Drill to create precision holes with unmatched speed and accuracy. The intricate pattern cut in heat-sensitive PLLA polymer stent (right) illustrates Raydiance s ability to expand materials selection and capacity for manufacturers using athermal ablation Raydiance, Inc. All Rights Reserved.Raydiance, Inc., the Raydiance logos, and all other Raydiance products or service names are trademarks of Raydiance, Inc. Raydiance products are covered by U.S. Patents ( Rev Precision Machining Without Heat pg 5

Applications Catheters. Polymer Tube Processing Catheter Hole Drilling

Applications Catheters. Polymer Tube Processing Catheter Hole Drilling Applications Catheters Polymer Tube Processing Catheter Hole Drilling Stainless Steel Tube Processing Laser Light Technologies can achieve virtually burr-free cuts in stainless steel tubing of various