Several assembly techniques that compete with machining are used to make components with metal powders. These are on the rise, partly to fill the automotive industry's growing need for lightweight, low-cost, high-volume parts.Other industries like industrial tooling and biomedical devices are taking advantage of these highly automated processes that offer low part-to-part variability, less material waste, and fewer steps. New processes and more materials choices are expanding these techniques, making them increasingly attractive for some of the structural components used in commercial aerospace.
The automotive industry is the largest consumer of powder metal (PM) parts, followed by industrial motors and controls. An automotive transmission might contain as many as 55 parts made with PM, according to Jim Dale, vice president of the Metal Powder Industries Federation.
"We're seeing the amount of PM used in vehicles increasing each year," Chris Franks, vice president of sales and marketing for the Americas at GKN Sinter Metals, told us. "We're modifying materials to develop processes more tailored to a specific application."
Manufacturing processes for creating near-net-shape structural components with PM form parts with either heat or pressure. Press-and-sinter PM shapes metal powders with custom dies under high pressure, then heats parts by sintering. Another process, hot isostatic pressing (HIP), is used for larger parts. "There's a limit on PM part size of around 42 pounds," Dale said. "Most PM parts weigh less than five pounds. Right now, individual parts are getting bigger and heavier as both presses and applications get bigger."
Powder injection molding (PIM) combines the ability of conventional injection molding machines to make complex geometries with the precision and materials flexibility of PM. PIM can produce medium to high volumes of consistent components with complex shapes, multiple textured surfaces, and intricate details. Components can combine several parts, eliminating process steps and reducing cycle times.
The biggest users of PIM are the medical, consumer electronics, mechanical devices, aerospace, automotive, and general consumer goods industries, said Scott Justus, BASF's business manager for Catamold products, North America. BASF is getting more inquiries about PIM across all industries, and growth rates are rising, he said. "More companies are looking to do lean manufacturing and continuous improvement, so they're taking a harder look at PIM since it provides good overall value."