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Virtual Mold Design

July 10, 2006
As the expectations rise, fettling systems get more productive, flexible, and precise in the task of cleaning high volumes of castings.

Fast and easy. For years, metalcasting engineers have been hoping to hear those two words in connection to design services. It took a while, but now those words are not only hoped for when talking about designing a mold, they are expected.

Since the advent of solidification software in the 1980s, foundries have been able to use such programs to help design casting models with an eye toward optimizing riser design, while studying such issues as shrinkage, microstructures, and stresses — all of which help ensure that quality castings are made. And, the success of using such software has been impressive, to the point where more and more suppliers are offering their design expertise to foundries. A one-stop-shopping approach to metalcasting.

Like metal solidification software, mold or sand-core modeling software is a 3-D computer program. Such programs offer an economical and quicker way for metalcasters to detect and solve mold and coremaking problems quickly, or in some cases, before they even occur.

In late 2004, Ashland Casting Solutions opened its Design Services Center at its headquarters in Dublin, OH, with the specific purpose of providing design-to-manufacture support from engineered drawings through casting, and testing. To that end, the Design Services Center is staffed with engineers dedicated to addressing the concerns of the diverse foundry industry. In addition, customers can avail themselves of the latest technologies and technical support not only to improve their casting designs and processes, but also to increase production and profitability.

One such technology, Arena-flow, has been key to Ashland’s success in providing its customers with the necessary tools for mold design.

Developed by Arena, LLC, Albuquerque, NM, in conjunction with General Motors, NASA, the Dept. of Energy, as well as Ashland Casting Solutions, it delivers a complete picture of the entire coremaking process. It includes the blowing, gassing and purging cycles, as well as the capability to analyze the virtual cores before investing significant time, money, and material. The software also allows tooling manufacturers to validate optimum designs in virtual space to ensure that cold box tooling is optimized the first time. Although the technology can be accessed by software license agreements, Ashland is seeing success with contract engineering projects conducted on the premises of the Design Services Center.

"Our biggest issue is merging design and foundries," explains Ruben Bake, global marketing manager for ACS, a business unit of Ashland Specialty Chemical, a division of Ashland Inc. "It takes a long time to design a part and then make it usable and be able to produce it; we try to merge these two things, concept to manufacturing."

Recent enhancements to Arena-flow software has made it even more user friendly. The 6.0 version includes a new installation wizard and graphical user interface (GUI) redesign, both improvements help the software deliver a complete picture of the entire coremaking process including blowing, gassing gassing and purging cycles, as well as allowing metalcasters the ability to analyze virtual cores before investing significant time, money, and material in the coremaking process.

"From a user’s perspective it (Version 6.0) is easier to interface. It also adds gassing to it and can show how efficient the gassing is," declares Bake.

In addition to Arena-flow, Ashland also recently obtained the licenses for MAGMAsoft, ProCast, and QuikCast software. Although more geared toward analyzing castings, all three software packages can be used evaluate molds. ProCast software, developed by ESI Group, provides a complete finite element solution that allows for in-depth predictive valuations of the entire casting process, including mold filling. QuickCast, also from ESI, also simulates the entire casting process from filling to solidification, including defects prediction using efficient finite difference technology. MagmaSoft software, by Magma GmbH, is a comprehensive simulation tool with capabilities that show mold filling, solidification, mechanical properties, thermal stresses and distortions.

Bake points out the advantage of the ACS’s Casting Design Services. "When it comes to molding, often foundries come to us with an issue of quality or productivity- — core breakage for example — and look to us to use our expertise and software to help fix it. Arena-flow is a simulation software. The foundry gives us the current parameters, and our software and expertise we’ll tell them where the issue is. That isn’t to say that we don’t take requests from foundries where they are looking for assistance with a brand new mold. We do. The length of time for that new mold development depends on the project.

Patternless castings

A comparatively recent development in rapid prototyping is giving metalcasters more options when faced with "problem" castings. Rapid Casting Technology (RCT) from was developed in Germany and has been commercially available in the U.S. for the past two years.

What is different about the technology is that it has the ability to make the molds directly from the design stage. It enables metalcasters to produce casting molds and cores directly from CAD files. By eliminating the patternmaking step, RCT can reduce production time by nearly 70%. Basically, it "slices" a 3D model, electronically, and then "prints" the mold or core in sand. "The base materials that we use match what foundries use exactly," explains Jeffrey

McDaniel, Prometal engineering and project manager. "We use silica sand and furan binding systems. All we’re really doing is changing the way a mold is tooled up. We’re doing it virtually."

The ability to virtually tool up the mold is what makes RCT so flexible. It allows foundries to work with castings with problem geometries or lower volume production runs to take calculated risks without committing to tooling. "If you want to create several different variants with different cores, we can do that. We can change the entire characteristics," enthuses McDaniel.

For example, RCT can look at changes in the path of the molten metal before it touches the casting Other issues such as gating designs and venting systems can also be evaluated. According to McDaniel, "some people are looking at this as an alternative to investment casting, where the concern is that the metal get to all the thin walls."

Although Prometal provides contract services-supplying molds, cores, assistance in building the CAD — the company also sells the machines-the S15 and SR2 system, as well. "The cost is not as prohibitive as you might think," states McDaniel. That is particularly true when you consider the reduction in production time. Since both machines also uses standard foundry sands and binders it allows for the on-demand casting of aluminum alloys, copper alloys, gray iron, ductile iron, and magnesium. A foundry can print a CAD model one day and cast the next. Furthermore, since a pattern is no longer needed, last minute design changes are no problem.

"At the moment, we have more customers coming to us for our contract services," explains McDaniel. Customers can provide the CAD designs, but the company also has the ability to scan a part and develop a mold from that point. We can also develop a mold from something two dimensional by converting it to three-dimensional and then scanning that."

However, Prometal’s ultimate goal is to strike a balance between the number of machines it sells and its contract services as foundries become more comfortable with the technology. "It is just a different way to look at tooling. We’re doing it virtually and that makes it quicker and more flexible for foundries."