Clinkenbeard & Associates, Rockford, Ill. “If the casting process cannot deliver quickly enough, there is the option to machine hog-outs from solid stock in aluminum, iron, steel—any material which is available in solid stock.” Another industry engineer views
rapid prototyping as acquiring the positive of a part. Te geometry is the same, but the material may not be. “Some processes, such as selec-
tive laser sintering will produce metal parts, but other processes, such as fused deposition modeling, can produce plastic parts that can provide some of the capabilities of the end material and show how it fits within the whole assembly,” said David Pow- eleit, who has worked as an application engineer with the American Metal- casting Consortium. With so many options available,
choosing the best one to offer your customers can seem daunting. But Poweleit said the rapid prototyp- ing method isn’t as important as the metalcasting facility’s ability to deliver a part fast using its own preferred method.
Cost Factors When you are utilizing RP or rapid
manufacturing, you are eliminating the costs associated with building and designing permanent tooling for multiple design iterations, reducing costs of production tooling for small quantities, and in most cases reducing time to market. But the faster methods come at a cost. According to Gary Burrow, president of HA Burrow Pattern Works, Joliet, Mont., a significant portion of invest- ment on a rapid manufactured part will go toward solidification modeling. “Typically, because you only have
one part, you can’t afford to lose the one pattern or mold you’ve created, so solidification software is important and adds a fair amount of cost,” he said. Material costs associated with the
RP method are also a factor when quoting a part. For instance, the stereolithography (SLA) method is usually cost effective for parts pro- duced within a 1-ft. cube, according to Poweleit. Beyond a 3-ft. cube, the
method might not be cost effective because of the size and cost of the SLA material. However, some niche organizations can produce large parts using this method. Tooling-less processes can reduce the cost and time of making a pattern, but tooling isn’t always an expensive option. CNC cutting of tooling has improved in accuracy and speed. Ren board material (a polyurethane used for patternmaking) has become more economical. “I’ve quoted parts where I thought
rapid molding would be the way to go,” Burrow said. “But I found out that with CNC, we could build the pattern fast and deliver it in the same time frame for less because the pattern is so easy to produce using the CNC process.” New methods continue to be devel-
oped—for instance, a group at Iowa State Univ., Ames, Iowa, is developing a rapid patternmaking machine that removes layers to build a pattern—but the traditional methods are improving, as well, Poweleit said. “[RP] is going bigger, faster,
cheaper,” Poweleit said. “When you are talking RP, taking minutes off is meaningful. Reducing material costs is another important improvement.” In additive manufacturing, the
“steps” between each layer, which are visible on the surface of a part or pattern, are narrowing. Usually, the steps between each layer require sec- ondary finishing to blend them into the surface. This can affect toler- ances. As the step size between lay- ers decreases, the need for secondary finishing decreases and dimensional accuracy improves.
Industries Served
According to Burrow, using an RP method to produce a part might be beneficial if: • The customer only needs one or two pieces.
• The customer is unsure of the part’s final design.
• Production tooling is expensive when amortizing against required or limited production quantities.
• The design requires intricate and complex cores needing consider- able assembly. Rapid prototyping has been widely
used for years by the defense and aero- space industries, but other industries are starting to take advantage, includ- ing the pump, medical and automotive aftermarket industries. “Te defense industry uses it often when tooling is lost and two, four or six pieces are needed,” Burrow said. “Tey can provide a 2-D drawing, it can generally be converted into a CAD model quickly and the additive manufacturing method best suited for that particular part is chosen. Tat’s cost savings for not having to buy tooling, plus it’s a fast turnaround.” The pump market has utilized
rapid methods for similar reasons, particularly to repair parts. The medical industry often uses rapid methods for implants, such as knee and hip joints. In some cases, an individual’s original joint will be scanned to create a CAD model so the part is an exact fit to the indi- vidual. Many experimental medical equipment components also are prototyped to prove out a design.
This urethane pattern was CNC-machined from a CAD file.
Only three pieces were required for this defense industry replacement part made with an SLA pattern.
May 2012 MODERN CASTING | 41
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76