Recent Developments in Rapid Prototyping

To All:
    Some excerpts from a Rapid Prototyping article in Manufacturing Engineering Magazine.
April 2009 Vol. 142 No. 4
Art to part with no machining
Robert B. Aronson, Senior Editor
"Rapid prototyping" is no longer a suitable catch-all term that defines an entire industry. It is just one of many applications for a field more properly called additive-fabrication (AF) technology. (Machining operations are subtractive in that a product is created by cutting away material. With AF, products are made by adding material.) In addition to prototypes, this technology's applications include short-run production, replacement parts, tooling, and casting patterns. Other terms used for this type of work are rapid manufacturing (RM) and additive manufacturing (AM).
Whatever the title, this industry is no longer dominated by service bureaus. Lower costs and greater ease of use has made much AF equipment both more attractive and affordable. Printers that make products in 3-D are now available for $15,000, and there are hints that $10,000 units are in the works.
In units that can make metal parts, a laser or electron beam focused on a steel preform creates a molten-metal pool. Then a stream of powdered metal or polymer is injected into the melted metal. The stream of powdered material, under computer control, traces out the desired shape and solidifies into a thin layer. The layers build up to form a part.
Currently metal parts are made using a process offered by EOS, a German company with offices in Novi, MI. According to company Vice President Jim Fendrick, "EOS systems work with two stainless steels, cobalt-chromium, maraging steel, and titanium, and efforts are under way to include the Inconel family of metals as well as aluminum. AF technology has advanced to the point where it is a viable option to more traditional manufacturing processes."
The unit now available from EOS has a work envelope of 10 x 10 x 12"
The EOS direct-metal process produces parts with properties said to be superior to those made by conventional casting, chiefly because of better grain structure.
Electron-beam melting (EBM) is the process used by the metal-part making units from Arcam (Gothenburg, Sweden). This process is similar to that employed by units based on a laser-heating system, but instead Arcam units use an electron beam. The Arcam A2, the larger of the two units the company builds, uses a 4000-W electron beam to heat metal powder to 1100C. The molten stream is used to form the part under computer control.
The Selective Laser Melting (SLM) process used by MTT Technologies Group (Staffordshire, UK) produces fully dense metal parts direct from a 3-D CAD program using a high-powered laser. Parts are built layer-by-layer in thicknesses ranging from 30 to 100 m. The process uses a range of atomized powder metals including stainless steel 316L and 17-4PH, H13 tool steel, aluminum alloys such as Al-Si-12Mg and Al-Si-10Mg, titanium alloys including Ti-6Al-4V and Ti-6Al-7Nb, commercially pure titanium, and (ASTM75).
"Build speed and surface finish are both material dependent. Tool steels take longest to make a part and titanium and aluminum parts are made faster. For fully dense parts, build speed reportedly ranges from 5 to 20 cm3/hr. Surface finish is in the range of 1530m for horizontal surfaces and 1325m for vertical sides. Laser scanning strategies can control surface finish," Weston concludes.
Here's What's Happening One misconception is that additive fabrication (AF) materials are not strong. This stems from the early days when stereolithography resins were very brittle. There's still a great need and opportunity to produce materials for a broader range of applications, but the materials available today are meeting many needs.
Another misconception is that AF machine technology is not affordable. In January 2009, Stratasys introduced the uPrint machine for $14,900. Z Corp. offers a machine for $19,900. It is true that you can spend $1 million or more on equipment, but sub-$50,000 systems are available.
Two fields that are developing notably are dental copings for crowns and bridges, and orthopedic implants. Companies are using metal-based systems from Arcam, EOS, and MTT. The materials for these two applications are mostly cobalt-chrome and titanium alloys.
AF is becoming an alternative to machining and even injection molding, in some instances. ===============================================================
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
On Fri, 17 Apr 2009 17:21:52 -0700, BottleBob

<snip> ----------- Anyone got one up and running in their garage off a RPC yet?
Unka' George [George McDuffee] ------------------------------------------- He that will not apply new remedies, must expect new evils: for Time is the greatest innovator: and if Time, of course, alter things to the worse, and wisdom and counsel shall not alter them to the better, what shall be the end?
Francis Bacon (1561-1626), English philosopher, essayist, statesman. Essays, "Of Innovations" (1597-1625).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.