Technology news
Ultrafine Powders Yield High-Strength Implants
Subjecting a material to extreme stress and pressure may significantly enhance its strength and durability. The process, called severe plastic deformation, is the first practical method for making high-strength biomechanical and industrial components from useful amounts of ultrafine metal, ceramic, or composite powders, according to Emil Strumban, general manager of Synmatix Corp. (Southfield, MI, USA). Synmatix is collaborating with researchers at US and Russian laboratories to develop and commercialize the technique.
In severe plastic deformation, materials and alloys are subjected to loads exceeding 400 tn/sq in. These high loads, combined with torsion straining and other pressing methods currently being refined at the State Scientific Research Institute for Chemistry in Moscow, produce extremely small grains devoid of the impurities that are a common by-product of other processes. "Parts made with this process exhibit significantly improved performance and durability," says Strumban. "Aluminium components formed from ultrafine powders will be far stronger than conventional large-grained aluminium parts, and steel cutting tools with ultrafine grains will last several times longer [than conventional tools]," he adds. Under certain conditions, Strumban says, pore-free malleable ceramics can be formed from these nanopowders. The first products that Synmatix plans to commercialize, however, are titanium implants for repairing broken or malformed bones, as well as other orthopaedic devices. While titanium is chemically inert, large-grained pure titanium lacks the strength needed for implants, according to Strumban. The new process, he adds, allows consolidation of ultrafine pure titanium powder into high-strength implants without requiring potentially toxic alloying elements.
The powders are formed into orthopaedic com-ponents at the State Aviation Technical University (Ufa, Russia), and calcium oxide coatings are applied to the implants at the Powder Metallurgy Institute in Minsk, Belarus. Then the prototype components are shipped to Los Alamos National Laboratory (Los Alamos, NM, USA) for structural characterization and performance testing.
Other potential applications for the nanopowders include new types of filter membranes and materials for joining ceramics. Synmatix is currently enlisting potential product development partners and identifying manufacturers to license the technology.
Plasma-Based Detector Outperforms Conventional Leak Testers
Medical containers that had been passed as "good" using conventional leak-testing methods were found to have several faulty mouldings when they were evaluated using the Plasma leak detector. The tester is manufactured by Blow Moulding Controls Ltd. (Toddington, Glos, UK).
Unlike conventional test methods that rely on air flowing through a hole, the system developed by Blow Moulding Controls functions by sending a high-voltage charge into the device being tested. "In effect," says managing director Robin Enderby, "a faulty container is like an imperfect capacitor. The inner surface of the moulding acts as one plate of a capacitor: if a hole exists, the charge is rapidly dissipated through the opening." Micron-sized holes produced in test samples with a UV laser were easily detected by the Plasma unit, according to Enderby.
During the test, a segmented conductive shield is placed around the device to determine the location of the holes. This has the advantage of highlighting the process defect that caused the holes in the first place, adds Enderby, and allows the operator to set different levels of testing sensitivity for discrete areas of the device.
Practically all types of plastic devices can be tested, with the exception of those containing moulded-in conductive components. The Plasma can be supplied as a stand-alone device or as part of a fully automated handling system.
CAE Programme Eliminates Need for Finite Element Analysis Meshing
Desktop plastics CAE software developed by C-Mold Europe (Enschede, Netherlands) reportedly is the first to accept solid geometry models generated from any CAD package. No finite element analysis (FEA) meshing is required, and 3D QuickFill displays injection moulding simulations directly on the designer's solid model in an average of 15 minutes or less.
"FEA meshing is a specialized skill that is often viewed as an impediment to a designer's productivity," says C-Mold chief operating officer Peter Medina. "Though simulation provides valuable design insight, it is very hard for designers to justify the added time and skill development."
3D QuickFill also incorporates a material data system composed of the 20 most commonly used material classifications, each of which can be customized with melt-flow index information. "We researched which materials are most important to today's designer and built a system that allows the user to develop a custom database. It can include thousands of candidate materials without testing or delays," says technical marketing manager LeRay Dandy.
Dispensing with the need to model a runner system or mould features also represents a significant advantage for designers, notes Medina. "Most part designers do not feel comfortable modelling a polymer melt delivery system and they often do not have the background to model a mould cavity," he says. "We have built into the software intelligence that allows the user to assign gate locations directly on the solid model by pointing and clicking the mouse. The software takes care of everything else."
When the simulation reveals a potential design or manufacturing problem, 3D QuickFill provides immediate advice and solutions. The programme can suggest where the plastic should be injected, the size of moulding machine that will be required, what to do if the mould does not fill completely, and so forth. No specialized training is required to operate the programme.
