Originally Published November/December 2000
Technology news
MATERIALS
High-Nitrogen Implantable Steel Is Produced Using Single-Melt Method
Stainless steel with a high nitrogen content is the most recent addition to a range of stainless steels suited for orthopaedic implants, fracture management systems, coronary stents, and related applications. Developed by AB Sandvik Steel in conjunction with Sandvik Metinox (Sheffield, UK), Bioline High-N surpasses the mechanical properties and corrosion resistance of widely used 316LVM, according to UK technical sales manager Stephen Cowen.
To comply with the cleanliness requirements of ISO 5832-1 (316LVM) and ISO 5832-9, materials are traditionally refined by means of vacuum arc remelting or electro slag remelting. Although ISO 5832-9 only recommends remelting the material, the practice is so ingrained that many implant manufacturers consider it to be mandatory. Sandvik has adapted the argon oxygen decarburization process generally used to melt bulk stainless steel to the processing of Bioline High-N. By using this method, Sandvik is able to produce material on a large scale that meets all the requirements of ISO 5832-9 without the need for further refining.
"Sandvik is able to eliminate the secondary remelting stage of manufacture thanks to very tight inclusion control during melting, valuable expertise gained from over a century of bulk stainless-steel production combined with extensive investments in R&D," says Cowen. "The material's inclusion content fully conforms to ISO 5832-9," adds Cowen, "and this is achieved in a single melt." In fact, Bioline High-N is comparable to the best remelted material when evaluated against the ISO standard, which measures the largest inclusion of each type, and Swedish standard SS 11 11 16, which measures both the frequency and type of inclusion.
Bioline High-N
stainless steel, fabricated by means of a bulk processing method, is suited
for use in coronary stents and other implantable products.
Bioline High-N is available in wire, strip, bar, and tube form and in different tensile strengths. Implant-grade materials are manufactured at Sandvik Steel mills located around the world and are housed in the Sheffield customer service and technical center. In addition to stocking a range of semifinished products for rapid delivery, the firm can draw on its global R&D and manufacturing resources to supply bespoke materials. "A major factor in our success with device OEMs," says Cowen, "has been the ability to solve their problems. We are not merely a supplier of stainless implantable steel, . . . we like to build a relationship and get involved in a product's development." That has been a winning formula for the company. Since the purpose-built facility was inaugurated in 1997, Sandvik Metinox has seen volume sales of medical application material increase by more than 50%, according to Cowen.
—Norbert Sparrow
SOFTWARE
New Surface Design Technology Improves MCAD Capabilities
New free-form surfacing technology has been developed to complement existing parametric surface design tools in Pro/Engineer. PTC GmbH (Unterschleissheim, Germany), a provider of mechanical computer-aided design (MCAD) and collaborative product commerce, has revealed plans to make the new technology available to the public later this year.
Pro/Engineer
enabled Carroll Design Inc. (Lowell, MA, USA) to view small details and quickly
create prototypes of its haemostatic eraser.
Part of PTC's Pro/Engineer suite of integrated MCAD solutions, the software will provide a natural, more mainstream alternative to PTC's CDRS product line, according to the firm. "The interactive surface design technology will be the next step in PTC's all-in-one platform strategy, which will deliver the ultimate enterprise process integration between industrial design and engineering," says Jon Stevenson, general manager and senior vice president, MCAD, at PTC's US headquarters.
The all-in-one platform integrates industrial design and engineering processes.
The technology will enable users to work directly with curves, surfaces, and facets, allowing for quick design realization and modification. PTC's integrated free-form surfacing design capabilities, along with its Pro/Engineer parametric surface design tools, are said to provide a completely collaborative environment for product designers. Projects can be transferred between engineering and designing software and worked on concurrently. Changes are communicated to all groups and suppliers that are involved in the product development process. The new program uses soft-point technology that results in lighter, more-flexible curves, and quick, intuitive, dynamic interaction with models.
—Katherine Sweeny
INJECTION MOULDING
Stack Moulding Technology Streamlines Multicomponent Production
A new stack mould for multicomponent injection moulding has been created by Wilden Engineering- und Vertriebsgesellschaft mbH (Regensburg, Germany).
Originally stemming from a consumer project undertaken for Siemens, the technology promises to benefit medical manufacturers. While conventional injection moulding employs a single mould with an injection side and an ejection side, stack moulding makes use of a vertically turning central block with cavities on all four sides. After each process step, the block rotates 90°. The first step is the production of the moulded base part, which remains in the cavity. In the second step, the mould rotates 90° and the cavity with the moulded part is available to accept insert parts. In the third step, the 90° rotation makes this cavity available for the second screw to complete the moulding operation. With the last rotation, the finished part can be removed by a handling system.
According to company spokesmen, this moulding technique offers many advantages. "By using all four sides of the mould, the number of cavities is doubled at a lower clamping force," says Norbert Kaspers, sales director for medical plastic components at Wilden. Moreover, since two sides of the mould are accessible at all times, he points out, there are more opportunities for the automated insertion or removal of parts during the injection moulding process, resulting in significant cycle time reductions.
Stack moulding is expected to be effective for high-volume components incorporating combinations of soft and hard materials, such as syringes or vials. Wilden produces parts, complete subassemblies, and custom-packaged products for the medical, pharmaceutical, and diagnostic industries.
At the Medica show in Düsseldorf, Germany, the company plans to display a new skin-pricking aid, Softclix, which was developed for Roche Diagnostics GmbH (Mannheim, Germany). Wilden was involved not only in the engineering of the product, but also in its moulding, assembly, and packaging.
—Benjamin Lichtman
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