Components of this seat post bracket for a bicycle (below) are fabricated in a cluster of hollow parts prior to separation and assembly. Credit: Renishaw
Most machine shops and equipment OEMs know Renishaw as a metrology specialist. But the company also supplies laser-powered additive manufacturing (AM) systems, a capability it acquired with the acquisition of the U.K.'s MTT Investments Ltd. and its subsidiary MTT Technologies in 2011.
The acquisition was the latest move by Renishaw to diversify and expand its business. The company also has a healthcare division whose products include dental prostheses, as well as a fixturing unit for workpieces.
"Renishaw is first and foremost a technology company," said Dave Bozich, the company's business manager for machine tool and additive manufacturing. "Metrology is our claim to fame and at the heart of what we do. But in recent years there has been a subtle departure from our business framework."
Renishaw, with U.S. operations in Hoffman Estates, Ill., and headquarters in Gloucestershire, England, has diversified operations by adding synergistic businesses that provide growth potential. The AM systems the company now supplies can, for example, fabricate hundreds of metallic dental copings for Renishaw at a time. And the fixturing unit allows the company to develop fixtures for its own use and for the commercial market.
In AM, Renishaw believes it is positioned to capitalize on growing demand. Bozich said he expects the technology to become more efficient, lower in cost, and suitable for diverse, high-volume operations. Ongoing developments that encourage his view include higher-power lasers, multiple lasers operating simultaneously, and more hybrid manufacturing platforms that build parts via additive manufacturing and finish them with machining in one setup.
The system Renishaw offers is the AM250. The model number refers to part size capability: length and width of 250 mm (9.8 in) and height to 360 mm (about 14.2 in). The unit works with a variety of metal powders: cobalt chrome, stainless steel, Inconel, titanium, and aluminum, among them. "Anything that can be welded," Bozich noted.
The AM250 is also an open architecture system, which means a user can set it up to fabricate and control almost any type of shape or material.
Bozich said it may be the only system on the market that uses a sealed vacuum casting platform for fabrication. This is important because with a tightly sealed work area, there is low consumption of the argon gas used in the laser fabrication process and minimal chance that the gas or metal powders will bleed into shop air. Other AM suppliers provide vacuum systems for the same reason, but Bozich claimed they are not as powerful as the AM250 sealed vacuum area.
The system uses a 250- or 400-watt fiber-optic laser. Buildup rates are 12 to 15 cu-cm (0.73 to 0.92 cu-in)/hr with the 250-watt version and 15 to 30 cu-cm (0.92 to 1.83 cu-in)/hr with the 450-watt laser.
Renishaw and Empire Cycles achieved significant weight savings by redesigning this mountain bike for additive manufacturing production.
One feature with the Renishaw laser that Bozich cited is modulation. Rather than remaining on during layer buildup, both versions of the AM250 laser modulate at high frequency. By turning the laser on and off at millisecond intervals, there is greater control of the energy it emits. The key benefit to this is no buildup of material around the area where the laser is directed, and thus no straggler particles.
Modulating the laser also achieves thin-wall details and crisp exterior surfaces, since excess material doesn't collect around the path of the laser, according to Bozich.
Another feature of the system is a flexible recoater, which applies the right force to keep the metal powder properly packed and its surface clean.
Bozich said that laser tolerances vary by application and material, but generally the system can build wall thicknesses of 200 microns (0.008 in).
Renishaw highlighted the AM250 at the International Manufacturing Technology Show in September, along with a trial application - a mountain bike from Empire Cycles in the U.K. that has a frame and seat post bracket fabricated of titanium alloy. The hollow frame and bracket were redesigned with topological optimization software and built in sections that were later bonded together.
Among the results were a 44 percent weight reduction in the seat post bracket and a 33 percent weight savings in the frame versus the original aluminum alloy designs. Since no tooling was used to make the parts, and component cost is based on material volume and not complexity, continuous design improvements can be made at minimal cost, according to Renishaw.
The Empire bicycle was a development exercise, Bozich said, and not a commercial product. "We did it to prove we could do it." Indeed, work continues to optimize the bicycle design and the results. The cost and time involved in producing the components, however, would not be viable for commercial production -- at least not now.
This will change in the future. "As additive manufacturing systems fabricate products more quickly, and as the cost of materials comes down, commercial products like the bicycle will be feasible," Bozich said.