Another choice for 3D printing in metal laser sintering: Renishaw
Directed Manufacturing, Inc. (DMI), Pflugerville, TX, is a leading 3D printing, rapid manufacturing company that produces plastic and metal parts, components, and assemblies. It recently purchased a Renishaw AM 250. Noted Alex, Fima, president of DMI, this purchase comes in direct response to design engineers demand for the production of metal parts.
“We needed to purchase another piece of equipment and today, we have a number of equipment options for selective laser melting than we are used to. We invested all the options (SLM Solutions, EOS, Concept Laser and so on). We liked the horsepower of the Renishaw system, as well as the system engineering improvement, integration, and service. An SLM machine is only valuable to us if it is building parts. Normally we benchmark 500 billable hours a month.”
The Renishaw AM 250 increases the service bureau’s capacity to supply metal parts in aluminum Al-Si-12, cobalt-chrome (ASTM75), H13 tool steel, Inconel 718, Inconel 625, stainless steel 316L, stainless steel 17-4PH, titanium CP, Ti-6Al-4V and Ti-6Al-7Nb through additive manufacturing. The system specifically addresses special processing requirements for 3D printing Titanium due to its high-quality atmosphere for building reactive materials where oxygen content must be minimized. In tests, the system’s running vacuum dropped oxygen levels to less than 100 parts per million. It also has the capacity to run non-reactive materials under nitrogen gas.
With the acquisition of the selective laser-melting (SLM) portion of MTT Technologies Ltd., in April of 2011, Renishaw entered the additive manufacturing market, adding its name to the list of manufacturers that offer 3D printing, prototyping, or additive manufacturing of metal parts. MTT’s CEO, Simon Scott, noted at the time of the acquisition, “the business fit between the two companies is perfect. We’re confident that Renishaw will be able to provide us with the ability to fully unlock the potential of SLM allowing us to compete with our peers and aim for a market leadership position.”
As in other 3D printing, additive-manufacturing systems, SLM parts from the two Renishaw systems, the AM125 and the AM250, are built layer by layer. The machines produce 100% fully dense parts in thicknesses that range from 20 to 100 microns using a range of fine metal powders that are fully melted in a tightly controlled atmosphere.
The machines use a third-generation design the company says represents state-of-the-art manufacturing technology. Key features include variable powder delivery, ultra low oxygen content in the build atmosphere, and an unparalleled safe-change filter system to minimize user contact with materials.
The two machines feature vacuum technology and low gas consumption. Both use “machine tool” engineering in design, operation, and serviceability, emphasizing ruggedness and ease of operation. The touch-screen operator interface includes menu options for machine preparation and clean down.
Consumable costs are kept low through features such as the soft re-coater blade that can be rotated several times before replacement, use of low-cost filter elements, and low gas consumption – all of which improve system reliability and cost of ownership.
Both systems are designed for rapid material changeover, with the AM125 using a cassette type materials delivery system and the AM250 a removable hopper. To enhance productivity, a valve interlock on the AM250 allows the addition of extra powder while the process is running. Safe processing of reactive materials, such as titanium and aluminum, is ensured with features such as a gas knife that clears away reactive, sooty emissions, and a heated build plate.
The AM125 has a part-build volume of 125 mm (4.92 in.) x 125 mm (4.92 in.) x 125 mm (4.92 in.) (X-Y-Z), and the AM250 has 250 mm (9.84 in.) x 250 mm (9.84 in.) x 300 mm (11.81 in.) (X-Y-Z) with Z axis extendable to 360 mm (14.17 in.). Both have build rates of 5 to 20 cm3 per hour, dependent on the material, part density and geometry. The AM125 offers a choice of 100 or 200 W laser, and the AM250 a 200 or 400 W laser.
Both machines have a fully welded vacuum chamber, enabling low-pressure evacuation followed by a recharge with high purity argon gas. Gas consumption after the initial chamber flood is low, and allows operation at oxygen concentrations below 50 parts per million – crucial when processing reactive materials, and contributing significantly to material integrity and mechanical performance.
DMI works with another SLM machine, and the engineers there have had a chance to examine the differences and similarities of parts made by each of them. According to DMI engineers, SLM systems produce nearly equivalent parts. Said Fima, “Having two machines from two manufacturers, you want to see how similar a part is if you put it in each platform, and we’re too the point where except for the really trained eye, you wouldn’t know what machine it came from.”
Even so, 3D printing metals is not necessarily easy. Fima advises that engineers be experienced in CAD programming, and it is also helpful to have a background in other machining and manufacturing methods.
Directed Manufacturing, Inc.