Micro processes poised to come online

Manufacturing is a rapidly changing industry and, to remain competitive, manufacturers must stay on top of many different technologies. Here, we examine several processes manufacturers of microparts may be hearing more about in the near term. Not all are new and some are currently being applied, but all will likely make an important impact on micromanufacturing in the coming years.

Ultrasonic atomization. Effectively delivering mist coolant to the microtool/workpiece interface is an emerging technology that should soon be available. The idea is to use high-pressure nozzles to atomize and deliver fine droplets of coolant that lubricate and remove heat without deflecting the tool. It is a challenge because droplet size, delivery velocity, coolant viscosity, surface tension of the coolant, temperature in the cut and chip size all interact to affect cooling.

Rotary ultrasonic machining. Manufacturers can produce microholes with fine finishes in hard materials by applying an abrasive-coated drill that is ultrasonically vibrated during application. Micro rotary ultrasonic machining can produce pockets or microholes as small as 0.010" in diameter in titanium alloys, ceramics and glass. Rotary ultrasonic machining reportedly promotes better debris removal, deeper cavities and leaves work surfaces cleaner than conventional ultrasonic machining.

Magnetic abrasive finishing. Magnetic abrasive finishing uses iron particles 150µm to 300µm in diameter coated with aluminum oxide to remove burrs from either internal or external features while imparting fine finishes. In the process, the abrasive fills the part and a magnet rotating around the part moves the abrasive. The process can remove laser- machined recast in 1mm, flexible, slotted capillary tubes. It is also effective for finishing the IDs of much smaller tubes.

Electrospinning. A growing number of medical applications involve making scaffolds with large pores that allow human cells to grow into and around the scaffolds. Polymers are squirted (spun) out of a syringe into a high-voltage field, which charges the polymer. The jet forms a spiral, and, as it dries in flight, is elongated by a whipping process until it is finally deposited on a grounded collector plate. The fibers pile up layer by layer to create the scaffolds.

Laser-induced chemical cutting. Laser radiation, surrounded by a coaxial expanding liquid jet stream, creates a thermochemical etching reaction, which provides high-resolution cutting. The laser-induced temperatures break down the passivation film that normally inhibits chemical action. By assuring an electrical field is also produced in the cutting zone, etch rates of 80,000 µm3/sec. can be achieved. One of the first applications has been to produce 200µm-thick nickel-titanium foils.

Laser-assisted microsheet forming. The Fraunhofer Institute for Laser Technology has embossed a magnesium alloy via conventional stamping by laser-warming the magnesium to produce channels 100µm deep and wide. The channels have excellent form. Initially intended for microfluidic applications, the process also works well for stamping complex parts.

Laser cleaning. Lasers have been used to clean large parts, but they can also remove residues left by microassembly processes or incurred when salvaging microcomponents. Lasers can remove nuclear contamination, small surface particles, passivating films, glue, coatings and corrosion. Lasers can remove particles as small as 0.1µm, which other processes typically cannot.

Abrasive waterjet micromachining (AWJMM). Microblasting is one of the least-expensive micromachining processes. Features down to 50µm and depths greater than 1mm can be produced in glass, and the process creates no heat-affected zone. Research in the Netherlands is focused on producing feature sizes smaller than 10µm. µ

About the author: Dr. LaRoux K. Gillespie spent 40 years producing precision parts to stringent QA and regulatory standards. Telephone: (816) 942-5497. E-mail: laroux1@earthlink.net.