Making a reality out of rapid cast prototypes.

Inside This Story:

* Now with an office outside of Detroit., ACTech is bringing its rapid prototype casting to the U.S. market while maintaining a foundry in Germany.

* Discussed within this article is how the firm can deliver high-quality, fully-finished prototypes to its customers within two weeks.

There really is no substitute for the real thing.

While rapid prototyping has changed the face of manufacturing and the ability to quickly produce component models to test for form fit and function, it is not without its problems when used in metalcasting. Most notably, these models often lack one quality--they are not real cast components. The cost of delivering cast metal prototypes often is seen as too high with too long of a leadtime. This, however, is not the case for ACTech, a firm based in Freiberg, Germany, that specializes in delivering low-volume prototype parts to customers with leadtimes of two weeks (and sometimes less).

What makes these parts unique is that they are real castings. The firm uses rapid prototyping technology to create chemically-bonded sand molds or cores using only CAD data and delivers a finished, fully machined component to its OEM customers.

Many OEMs require prototype parts for component field testing, specifically in the automotive and aerospace industries. Other times, designers may just want to try out a new component design. "In the automotive industry, OEMs usually need one or two cylinder heads for road tests," said Thomas Becket, sales manager at ACTech. "The traditional way is to produce a pattern for the component and use that equipment to make a mold. For the automotive industry, an Inline 4 cylinder head could cost up to $250,000 with a leadtime of 16 weeks. We can make a single 14 cylinder head without any pattern equipment at a cost of $25,000 with a lead time of three weeks.

He continued, "if a customer has an idea that they would like to try, they would traditionally need months before they would know if the casting could work. We can build this stuff in weeks and it would be much less expensive then putting a component into production."

Coming to America

ACTech emerged in the European market in 1995 and now has 300 customers in 20 countries. In 2002, approximately 10% of the firm's revenue came from North America with the rest coming from Europe. Today, approximately 80% of the revenue comes from Europe and the other 20% is in North America. After looking at the rising numbers, ACTech decided to set up a sales and engineering office in Belleville, Mich., in January 2003 to further serve the U.S. market.

"We first started jobs for U.S. customers in 1997, but it was a small part of our overall business," said Becket. "However, every' year we would add one or two more. The U.S. market is just as big as the European market. Why wouldn't we find as much work in the U.S. as we do in Europe?"

During its eight years of existence, the firm has worked on approximately 3600 projects while only making 30,000 castings, averaging eight castings/project. "The extra time we give our customers allows them to put their products to market earlier or retain them for tests and product development," said Becker. "We're not really dealing with castings--we're dealing with time."

Leadtimes and prototype prices depend upon the size, material, geometry and quality needed (prototypes for the aerospace industry are typically required to be of a higher quality because of the unique characteristics desired). Many of the parts ACTech produces can be done in less than two weeks. For customers in the U.S., that includes two or three days to allow for shipping from Germany.

"Once we create enough business, we are hoping to set up our own rapid prototyping foundry here," said Becket, who admits that the timing of the expansion is currently up-in-the-air. "It could happen next year or it could happen three years from now. It depends on the market's requirement, but we are halfway there."

The goal for ACTech is to make its U.S. division an independent business entity. "After the expansion, we will have the exact same technologies and operations in the U.S. as we do in Germany," said Becket. "And we strongly believe that the American market can entertain at least the same size as we have in Germany."

One of the reasons for ACTech's success is its unique business structure. The firm is not in competition with foundries, but rather a helpful friend.

"We don't try to be a production foundry," Becker said. "This gives them the chance to work with us without losing jobs to us, One of the advantages of what ACTech is giving to the foundry industry is we are a tool for engineers to develop complex castings, meaning more work for foundries by wining back market share for the industry. And we make no secret about our technology."

The Foundry

The current foundry in Freiberg is a 45,000 sq ft facility that employs approximately 150 people, including fulltime workers and trainees. Since 1998, ACTech has operated a facility that melts 735 kg/hr, utilizing six furnaces with 950 kg total melting capacity. The multiple furnaces allow the firm the flexibility to change casting alloys to process several different projects at the same time.

"We are not only pouring aluminum alloys, but we have the capacity for iron, steel and magnesium alloys. We can do everything you can do in sand." said Becker. "If you want it in gold, we will do it." ACTech also machines the prototype castings before delivery.

Outside of the rapid prototyping process used to create the mold, Becker stresses that fine castings are poured the same way as at any chemically bonded sand operation.

Manufacturing the Molds

In order to rapidly manufacture the casting molds, a mix of technologies is used to tours and sophisticated cores using laser sintered loose parts and core packages. These designs are based upon 3D CAD data of the casting's design.

First, a solid model is generated from the CAD files. Gating and feeding systems are added, as are machining stock and bosses for subsequent machining. The mold is split, the cores am separated from the mold and core prints are added. After the mold segments and cores are located with interlocks, the mold assembly is checked for fit and interference.

Based on the CAD design, into different processes can be used for the creation of the mold--laser or direct mold milling. These can be used as either a single process or used together to achieve the best results. They also can be used in conjunction with conventional patternmaking.

Laser Sintering--The laser sintering process utilizes chemically bonded sand to build up mold segments and cores. Initially, a thin layer of loose molding sand is applied to the building platform (base of 720 x 380 mm; maximum height of 380 mm). The sand is then exposed to two separate laser beams simultaneously.

Since each grain of sand is coated in a phenolic rosin, wherever the lasers meet, it fuses the grains together, bonding them to the layer below. Once the layer is complete, the platform is lowered and another layer of sand is added. The process continues layer by layer until the segments are complete. Afterwards, the segments and cores are post-cured in a furnace. Finally, they are ready for mold assembly and pouring.

Very fine contours, which normally cannot be manufactured in conventional sand casting configuration, can be replicated layer by layer. It also is possible to generate undercuts without problems. The process itself miles on CAD data for the mold segments and cores. From this data, the outline of the layers is automatically generated. Machine speeds range from 6 mm/hr for complex jobs to 40 mm/hr for easier segments.

"The laser sintering process gives the opportunity to build something that you can't easily create with pattern equipment," said Becket. "We can make complicated molds in one piece without worrying about undercuts or drops. It's possible to create similar molds with a pattern but you'd have to make several cores and assemble them."

Direct Mold Milling--While the laser sintering process is used for very, complex cotes and molds, direct mold milling was developed for simple, large geometries. For this process, a large block of sand is milled in the cope or drag halt" of the mold just as a pattern would be. The benefit is that the approximating speed is much faster then

milling into the pattern material.

"If you have a large part with a simple geometry, the process is nearly unlimited," said Becker. When used with the laser sintering process for cores, not only large, but a/so complicated castings can be produced as prototypes or in small batches in a short time.

One example of direct mold milling is the exhaust turbo charger for a marine diesel engine shown in Fig. 1. The 800 x 620 x 240 mm casting is too simple to be cost-effectively produced using laser sintering. The core and outer mold halves were each produced by direct mold milling and no additional parting lines were necessary.

[FIGURE 1 OMITTED]

In the End

ACTech is currently testing the U.S. waters before deciding to set up a full operation. The firm has been successful because it has combined the need for short leadtimes with the ability to deliver a machined, fully-finished cast component. The firm is thriving because it knows that, much like foundries, it is only as good as its end product.

"We make a casting the same as you would in a normal foundry," said Becker. "Tire chemistry and processes are the same as in a foundry. The only differences are how you create the mold and cores, so the result is the same as a foundry--it's as good or bad as the casting is."

For More Information

"Castings Fortify Ruger's Firearms," A.T. Spada, Engineered Casting Solutions, Winter 2002, p.20-24.