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Rofin-Baasel is offering a range of flexible all-in-one products for medical component manufacturing applications that require precision, quality, repeatability and traceability.

The company’s Starcut Tube Femto produces high-precision edge quality on bio-absorbable polymers.

The use of bio-absorbable polymers such as polylactic acid and polyglycolic acid has suffered owing to low melting points, making the polymers difficult to machine with traditional cutting lasers.

In addition, the heat-affected zone generated by the cutting process has resulted in unacceptable cut quality.

By comparison, machining these materials using femtosecond lasers produces excellent results on vascular stents, with high-precision edge quality.

Bio-absorbable polymer edges can be cut with high precision, despite their low melting points and poor absorption.

Manufacturing medical devices such as stents from tube stock typically relies on laser cutting with pulse widths in the ‘us’ scale.

Even with the optimum setup, the cutting process is not completely free from burrs and recast inside the tube.

This often means time-consuming post-processing using acid cleaning and electro-polishing on stainless steel and CoCr components.

The shape memory alloy nitinol can, in certain instances, also be prone to chemical and mechanical damage during these post-processing operations.

With femtosecond lasers, however, the only post-processing required is ultrasonic cleaning.

This improves post-processing efficiency, particularly with sensitive materials.

Under certain operating conditions, femtosecond lasers can process materials faster than energy can diffuse within the atomic lattice; as such, no heat is transferred to the surrounding material, eliminating any recast and burr.

The Starcut Tube Femto integrates a compact all-fibre-based laser source with reliability and long-term pulse stability – properties that are important for industrial manufacturing with femtosecond lasers but that, until now, have been hard to find in ultra-fast laser sources.

The Starcut Tube Femto mechanics have been adapted to the specific requirements for handling thin-walled, mechanically fragile, semi-finished products.

The new system complements the Starcut Tube series.

Several of these new systems are already installed and working at customer sites.

The quality of laser cutting and marking is, in the main, simple to assess.

Visual inspection using relatively low magnification will generally reveal process defects.

By contrast, for the inspection of laser welding there is no comparable optical method for determining weld volume or defects, except to identify obvious gross defects, according to the company.

Most of the metallic implantable medical devices used within the industry are welded with lamp-pumped Nd:Yag lasers, using a combination of single-shot spot welding and seam welding.

The pulsed laser operation enables rapid local heating and cooling, avoiding collateral thermal damage.

The devices produced using this process are often wires, tubes or assemblies combining both, with outside diameters of as little as 200-300um and made from stainless steels, nitinol or combinations of materials.

Validating weld quality by destructive testing can only be performed on a few assemblies; as a result, laser-welded medical device conformity requires the extremely tight monitoring and control of the laser output parameters.

It has traditionally been difficult to qualify lamp-pumped laser welding in the manufacture of medical devices because of fluctuations in the lamp output and therefore the laser output.

These variations include shot-to-shot fluctuations in laser output power, which increase as the lamp ages, and the variations in output from lamp to lamp, which are significant even when the lamps are new.

Historically, the problem was addressed by frequent user intervention, which the medical device industry prefers not to deal with because of validation regulations.

To overcome these obstacles, some form of control of the laser output is required.

The closed-loop control of electrical power and laser output pulse energy ensures consistent lamp pump output and laser energy output and eliminates the interference of back reflections from the workpiece.

The Rofin Control Unit (RCU) provides such control to pulsed Nd:Yag laser welding resonators and its use allows a pulse-to-pulse stability of less than +/-1 per cent to be achieved over the full range of laser powers.

These features provide the stable and predictable welding process required for medical device production.

Not only is it necessary to be able to control electrical power and laser output pulse energy in order to provide a stable and consistent weld, process traceability also forms a crucial part of medical device validation procedures.

The traceability required for laser-welded implantable parts is said to be far reaching because of US Food and Drug Administration (FDA) regulations.

Laser controllers should be capable of monitoring and recording the key laser parameters for each individual part that is processed and controlling the access levels to the system to avoid undocumented intervention.

Rofin-Baasel meets these criteria by recording and providing the following process information: a pulse energy log; an online measurement of pulse-to-pulse stability; a display of the energy values within a pulse train with maximum and minimum levels; and the export of all relevant pulse-related data with user-defined filter functions.

Rofin’s Select is an ergonomically designed and fully integrated laser welding system.

The system includes four high-precision axes that can be controlled manually by the use of a joystick or operated under full CNC control.

This concept provides a high degree of flexibility for welding applications on medical device components.

A flow-controlled exhaust system with Hepa filters is also incorporated and a closed-loop cooling system enables continuous operation.

Rofin Select offers users as much automation as they want, with the minimum of complexity.

All parameters are adjusted using the multi-function joystick and the large colour touch screen.

The marking and identification of medical instruments, tools and implants is subject to the same precision and repeatability demanded by the machining or welding applications performed in the previous stages of manufacture.

Lasers produce clear and durable marks by modifying the material colour and provide corrosion-free marking devoid of burrs or debris and without the need for filler materials.

There are almost no technical limits to the marking outline and content that can be produced and lasers are used to generate alphanumeric content, vector or rastered graphics, greyscale, barcodes or data-matrix codes.

Even micro marking with character heights as small as 10um is said to be possible.

The ability to individualise each component is also possible thanks to the flexible computer control of the process and on-the-fly marking can be carried out at high speed.

To meet the requirements of the marking applications that are typical of the medical device industry, Rofin has developed the Combiline Cube.

This is ideal for the integration of any one of the solid-state, fibre or diode lasers manufactured by Rofin.

Users combining this range of laser sources with the focusing optics and axes that are also available will be able to individually configure the Combiline Cube for a variety of marking applications.

The flexible configuration of the Combiline Cube also provides a number of options in the way in which the system can be used.

By adding a galvo scanning head and servo positioning axes, the system can be used to process large parts, or large trays of smaller parts, quickly and precisely.

The system also incorporates automatic rise-and-fall doors on three sides, if required, enabling the system to be automatically loaded and unloaded by a robot as part of an integrated production facility.

In addition, the system can be used as a standalone unit that can be loaded and unloaded manually by an operator via the automatic doors.

Rofin’s Visual Laser Marker (VLM) software allows the layout generation and transfer of the required marking data to be sent straight from the PC to the laser marker.

Rofin-Baasel UK Ltd is the UK sales and support subsidiary of Rofin Sinar Technologies Inc, which is one of the world’s largest manufacturers of industrial lasers and is quoted on the USA NASDAQ stock exchange. Rofin makes lasers and laser systems for marking, welding, cutting, drilling and perforating and offers sources and solutions across all the main industrial laser technologies CO2, solid state and fibre lasers. Our lasers are employed in most manufacturing markets to give customers unprecedented results in terms of quality and throughput. We have over 30,000 installations in industries such as medical device, electronics, automotive, jewellery, tool and mould, aerospace and solar power. Examples demonstrating the range of capabilities of Rofin lasers include: * In-line packaging material manufacturers use our lasers to create ‘easy open’ perforated lines in packaging. * High street jewellers buy our microwelding workstations to make and repair jewellery. * Surgical tool and implant manufacturers produce clean and permanent identification marks on their products with Rofin markers. * Photovoltaic customers rely on laser operations from scribing to drilling to make solar panels and wafers. Rofin-Baasel welcomes the opportunity to show customers what lasers can do for them.

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