Originally Published MPMN June 2002

EQUIPMENT NEWS: Laser Processing and Marking

Laser Equipment Makes Its Mark

Systems gain in efficiency and precision

Katherine Sweeny

Once a staple of science fiction, lasers are now a well-established part of medical device manufacturing. Laser marking of plastics and metals is essential for identifying, labeling, and bar coding parts. In addition, laser systems can also precisely cut and shape thin materials such as wire and stencils. Below are descriptions of several laser systems including diode-pumped laser markers, linear stages for laser positioning, and polymer stencil manufacturing systems.

Diode-pumped laser markers use less power than lamp-pumped systems

A pulsed-laser marker measures 6 x 6 x 21 in., making it one of the smallest 50-W marking lasers available. Using cost-effective Nd:YAG diode-pumped technology, the LM50 from Unitek Miyachi Corp. consumes 1.32 kW of power as compared with typical lamp-pumped systems that require 6.63 kW. Its laser diode array typically lasts more than 10,000 hours under normal operation, greatly reducing the maintenance costs and system downtime required for replacing flash lamps in lamp-pumped systems. In addition, it has a built-in chiller, eliminating the need for an external chilled water source to cool the laser.

A swiveling head design enables the laser to be rotated 180° in either direction, allowing great flexibility in system integration. The LM50 can be used to mark a variety of materials including superalloys; all metals, including whether ferrous or nonferrous; plastic; and rubber. It is also suitable for removing paint, ink, anodized coatings, and titanium nitrate. Applications include marking on implantable devices such as pacemakers, insulin pumps, catheters, cauterizing tools, and hearing-aid components. The laser can also be used for fine-wire cutting.

"The laser marker was developed to provide a solution to the ever-growing need for permanent part identification," says laser marker product development manager Gary Sheriff. "A medical company can efficiently identify and trace parts, as well as protect itself, by creating a proprietary mark."

Laservall North America LLC offers fiber-coupled diode-pumped solid-state laser sources and OEM marking systems in compact 5-, 10-, and 20-W models at 1064 nm. An 8-W model at 532 nm is also available. The Violino laser system is suitable for marking and other high-precision applications. Its high output efficiency and beam quality enable high-speed precision marking, engraving, and machining on virtually any material. The beam quality results in a small spot size and high power density in the spot, enhancing processing capability. The Violino is air cooled up to 20 W, requiring no water or external chiller. Diode pump life averages 10,000–15,000 working hours. It is available as an OEM laser source or as an OEM marker package complete with scanning head, DSP controller, and Windows 9X-, 2000-, ME-, and NT-compatible laser marking software.

UV lasers are suitable for high-volume marking

A series of UV lasers can mark white plastic medical components with designations such as part numbers, bar codes, and brand names. Offered by Coherent Laser Division Inc., the UV light output of the AVIA 355 lasers reacts with the titanium dioxide in a photochemical process within the plastic itself to mark parts without causing any surface composition change.

"In the medical industry where plastics marking has traditionally been done with ink-jet equipment, AVIA lasers offer an environmentally friendly marking method that doesn't rely on potentially toxic dyes," says business development manager Sri Venkat. "They are also easy to automate, even in high-volume manufacturing situations."

The AVIA 355 series systems are solid-state 355–nm laser sources ranging in average output power levels from 250 mW to 7 W. In most models, the pulse repetition rate can be adjusted on the fly from single shot to 100 kHz, and performance and beam quality can be optimized at each rate. Two field-replaceable, aluminum-free active-area diode modules pump the lasers. The diodes have demonstrated long lifetimes under extreme conditions, and contribute to the lasers' total life expectancy of more than 15,000 hours. The AVIA 355 lasers are manufactured in a cleanroom using the Permalign manufacturing technique, which involves aligning every component within the laser head with precision external tooling and then soldering them into place. The process ensures the permanent alignment of the laser head, improving laser efficiency and increasing its lifetime.

Laser system marks flat, rigid materials

A laser marker enables the transport and marking of flat workpieces with heights of up to 3 mm and type-plate sizes up to 100 x 50 mm. Supplied by Cab Technology Inc., the PI-5523500 Laser Typeplate marker is suitable for marking materials such as aluminum, steel, copper, glass, and plastic. The workpiece is automatically conveyed from an input magazine. After being marked, it is moved to a separate output device that can handle magazine speeds up to 100 mm/sec. The handling system is controlled by an integrated Siemens S7 PLC. Functions may be controlled by a digital operation panel and are shown on an LCD. The system requires a compressed-air supply with an air pressure of 5 bar. A fume extractor is recommended if materials cause an elevated emission of particles and contaminants.

Direct-drive linear stage has an ironless design

A direct-drive linear stage offers a low height profile, cable management, velocity control, low vibration, and accuracy, making it a suitable positioning system for laser processing and marking equipment used by medical device manufacturers. The ALS25000 stage from Aerotech Inc. has linear bearings that are supported by the maximum possible cross section while maintaining an overall low profile. Unlike other linear motor stages that use an iron-core flat motor design, the ALS25000 is driven by a high-power ironless forcer and U-channel magnet track to provide high throughput. Since the forcer does not contain iron parts, it is cog-free, which enables tight velocity control and contour motion profiles without sacrificing speed or acceleration. The magnetic field of the linear motor is self-contained within the U-channel design.

The U-channel track is made of opposing rows of high-power magnets that help to generate high output forces. An optimized cable management system attains millions of cycles of maintenance-free operation. Designed as a turnkey unit for both single- and multiaxis laser systems, the ALS25000 incorporates upper-axis cabling. Custom configurations are also available.

"The ALS25000 provides a small–cross section, medium payload capacity, environmentally protected, cost-effective alternative to the larger traditional linear motor stages," says applications engineer Steve Mallone. "Its smaller size and high-power linear motor make it suitable for high-performance x-y configurations."

Laser creates efficient polymer stencils

A laser system enables the production of stencils in polymer foil. This eliminates the need for chemical electroforming of metal-sheet stencils with a large amount of apertures.

The beam characteristics of the polymer laser from LPKF Laser & Electronics USA, in combination with the polymer material used for the stencils, results in good sidewall quality. Using these stencils reduces printing defects because they provide good paste release. The printing speed can also be three times faster than with regular metal stencils, and the average life span of a polymer stencil is much longer.

Printer setup with transparent polymer stencils is easier and about 50% quicker, according to the company. The stencils are mounted to the printing frame before cutting. This avoids any displacement errors caused by stretching, particularly on very thin stencils. Since no mesh is necessary to glue the stencil into the printing frame, the usable area is significantly larger with the same frame size than it would be using alternative methods.

The company's TurboCut II technology enables fast cuts of round apertures from 3 to 31 mm with a performance of up to 30,000 holes per hour and with a shape accuracy of 96%. The high performance makes the polymer laser suitable for stencils with more than 120,000 apertures.

Copyright ©2002 Medical Product Manufacturing News