Mark Dustrude/Portfolio Manager Medical Laser Technologies/TE Connectivity – Interventional Medical
Laser machining for minimally invasive devices calls for the most demanding of design and engineering solutions. Minimally invasive devices are synonymous with low profile sizes, often a fraction of a human hair in width; tight tolerance specifications, down to +/- 0.0005 in. ( ±0.0127mm) and high-performance materials that are challenging to process, such as shape-memory metals, precious metals, dissimilar materials and thermoplastic polymers. There are a number of considerations for successful laser machining within these design parameters:
- The primary objective when laser machining should be to minimize the heat-affected zone around the laser site. Advanced laser welding allows for precision joining of components with little heat input into the part. This creates less distortion than most conventional welding processes, resulting in higher accuracy and quality. Contact-free laser welding also helps prevent stress on materials.
- Femtosecond lasers are ideal in micromachining applications for drilling and cutting high-precision holes and shapes free from thermal damage. Femtosecond lasers are ultra-fast laser systems that essentially vaporize matter without a heat-affected zone. This capability creates new opportunities for advanced micro designs, particularly for difficult-to-process metals and composite materials not feasible for laser machining with conventional systems. There are significant cost benefits to femtosecond laser processing, as little or no post-processing or cleaning is required.
- Make a good start – always begin with the cleanest possible materials. When laser-cutting a material or if using a previously machined component, all foreign material must be removed in advance of processing. When joining two or more previously laser-processed components, laser-recast and heat-affected zones (HAZ), also referred to as laser slag, must be removed in advance. It’s also imperative to remove all machining oils from previously machined parts – even the smallest traces of oil will be detrimental to the overall quality of a laser weld. For manual handling of parts, always wear gloves to avoid getting foreign material or finger mark residue on the materials to be processed.
- Consider your design in terms of fit prior to laser processing, particularly when laser-welding components. When laser-welding two parts, they should fit together seamlessly without any gaps. A good rule of thumb is that the largest gap advised in a welded design should be half the thickness of the minimum material to be laser-processed.
- Attention to basic considerations such as drawings, tooling and measurements will assist in maintaining accuracy and quality between parts. Well-developed drawings are essential to producing quality components – weld symbols and callouts should be clearly outlined. Good laser processing begins with good tooling. Exacting tooling and fixturing will ensure that the materials to be processed are in the appropriate position prior to application of the laser, producing a part consistent with the intended design and maximizing yield. Consider how the part will be measured after laser processing, agreeing on measurement protocols in advance with all project leaders while balancing the protocol to achieve overall success in manufacturing.
- Biocompatibility – Laser processing ensures that no filler materials are added during the manufacturing process. Alternative processing methods often rely on filler materials, adding additional time and cost relating to biocompatibility issues during regulatory submissions.
Laser processing is a superior fabrication approach for a myriad of device applications. Coupled with the expertise of an experienced supplier, product designers can deliver a highly effective design, achieve excellent product quality and reduce overall processing costs for the most complex of minimally invasive devices.