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Building Complex Metal Parts Layer by Layer
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type of filler material. In the diffusion bonding process,
high temperature and pressure are applied to similar or dissimilar metals in a hot press, causing the atoms on solid metallic surfaces to intersperse and bond. Unlike traditional brazing techniques,
the resulting bond
exhibits the strength and tempera- ture-resistance of the base metals.
Joining Dissimilar Materials According to Walt Roloson, R&D
engineering manager at PVA TePla, one of the most appealing aspects of the process is its ability to not only create the internal structures, but also to join layers of dissimilar metals. In this regard, there is no restriction on materials since all tooling steels are available in bulk sheets.
August, 2019
PVA TePla offers large-format diffusion bonding for a variety of materials.
For the atoms of two solid, Our services:
75,000+ articles in stock in Munich, Germany 500,000+ additional articles readily available Delivery promise: Same day shipping for all orders received by 6pm
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buerklin.com Industry-focus line cards of well-known and reliable manufacturers eProcurement solutions: OCI, API, electronic catalogs, EDI Sales representatives in Italy, France, United Kingdom, Ireland, Scandinavia, Eastern Europe, Brazil and the Middle East
metallic surfaces to intersperse they typically must be at approximately 50 to 70 percent of the absolute melt- ing temperature of the materials. To achieve these temperatures, the sur- faces are heated either in a furnace or by electrical resistance to temper- atures as high as 2,552°F (1,400°C). For many years, this technique
has been used to join high-strength and refractory metals that are either difficult or impossible to weld by other means. However, it was only through recent improvements in dif- fusion bonding presses that this new process has become even more attractive. This includes improvements to
single-cylinder hydraulic presses that required fixtures to apply a con- sistent, measurable amount of force — a key factor in the process. Today, leading manufacturers,
www.buerklin.com YEARS
such as PVA TePla of Corona, California, offer multi-cylinder sys- tems with large pressing plates that can accommodate a variety of parts. The largest, the company’s MOV 853 HP can process parts as large as 35.43 x 49.21 in. (900 x 1,250 mm) at a pressing force of 4,000 kN. By controlling each cylinder
independently, companies like PVA TePla can provide a press that pro- vides extremely consistent pressure across the entire surface. The MOV 853 comes with built-in pressure transducers along the bottom of the pressing plate that allow individual hydraulic cylinders to be adjusted to achieve superior pressure uniformity over large areas. In addition to selling the equip-
ment, PVA TePla can create diffusion bonded parts using this technique through toll processing services offered by its parent company in Germany.
“Customers often come to us
with requests to bond aluminum to molybdenum or stainless steel,” says Roloson. “We are able to do that with diffusion bonding.” The multi-layer design also improves conformal cool- ing of plastic injection molds made in two-layer designs of tool steel and material, such as stainless steel (STAVAX). “For the most efficient perform-
ance, conformal cooling channels should be adapted as precisely as possible to the outer shape of the mold,” says Roloson. “The higher the number of layers bonded together, the more precisely it can match the outer shape.” By improving cooling perform-
ance, melted resins can be injected at higher pressures to significantly increases cycle times as much as 40 percent, while enhancing product quality. Once the layers are bonded together by diffusion bonding, Roloson says that traditional machin- ing techniques can then be used to create the final external shape. “Due to the molecular bonding
of the layers, the final part often shows no interface lines or striations. The interface of one material is actu- ally blended into the other one, and vice versa, even with dissimilar materials,” says Roloson. Although this additive manu-
facturing approach with diffusion bonding is for specialized applica- tions, it may be a perfect complement for precision machine shops that already have in-house laser-cutting and machining capabilities and are looking to diversify their offerings. Contact: PVA TePla America,
Inc., 251 Corporate Terrace, Corona, CA 92879 % 951-371-2500 fax: 951-371-9792 Web:
www.pvateplaamerica.com r
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