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Green Sand Metalcasting Foundry News

3D Printing As an Alternative to Pattern Making

Posted by Hill and Griffith Company on Jan 26, 2021 9:16:21 PM

3D printing has eliminated much of the tedium of the 3,000-year-old sand casting process

Excerpt from the January 2014 Additive Manufacturing article by Peter Zelinski.

Hoosier Pattern has changed its business in a way that dramatically expands the design freedom available to its customers. Historically, the company has machined foundry patterns. Today, it uses 3D printing to create molds and cores directly from sand.

That's sand casting in a nutshell, although journeyman pattern maker Dave Rittmeyer will tell you there's far more to it than that. Rittmeyer, the customer care and additive manufacturing manager at Hoosier Pattern Inc., Decatur, Ind., also will tell you the industry has undergone a dramatic shift over the past decade or so, thanks in part to AM.

Inspecting a Green Sand 3D Printed Core

Steve Murray says the problem with being a pattern supplier is that you often play the role of killjoy.

The salesperson with Hoosier Pattern of Decatur, Ind., is a journeyman pattern maker himself. He talks to customers about the parts they want to produce through casting. In the vast majority of cases, he says, there is some design compromise the customer has to make to accommodate casting's traditional requirements. An undercut might need to be eliminated, for example. Or, the internal geometry of the part might be too complex, resulting in an overly expensive core. Or, the part might need to be given a greater draft angle to allow the pattern to pull away from the sand mold cleanly. Because of considerations such as these, a customer usually has to cast a part that is at least slightly different from the design that this customer originally envisioned.

Until now. 

Green Sand 3D Printed Core

Mr. Murray's message to customers has now changed. That's because Hoosier Pattern has changed. In many cases, the company can now let customers cast precisely the parts they want to make. Rather than counseling customers to compromise, Mr. Murray now urges them to try to design the part that is optimal for the application. He often encourages them to look for ways that added complexity might remove unnecessary weight or improve the performance of the cast component. It is almost as if he is now able to say, Don’t worry about the manufacturability

The reason for this new freedom is 3D printing. Hoosier Pattern recently expanded its capabilities—actually transformed its capabilities—by adding an ExOne S-Max sand printing system. This is a machine that 3D-prints mold components in sand without any need for a pattern or core box. The machine essentially makes sand molds without the middleman.

To established professionals in the foundry industry, this can seem weird. Pattern shops supply patterns and foundries pack sand around them to make the mold—that's the way the industry works. For the pattern shop to skip the pattern and instead supply the sand mold is a change that Hoosier Pattern's customers sometimes have had to pause to wrap their heads around. 

However, this change both simplifies the casting process and overcomes many of its previous limitations. 3D printing of sand potentially makes casting both more efficient and more effective at the same time.

A pattern shop is a machine shop. Hoosier Pattern has around 30 CNC machine tools. For this reason, this company's introduction of 3D printing is interesting not just because of its implications for casting, but also because of what it illustrates about 3D printing. As Hoosier Pattern's example shows, 3D printing, or additive manufacturing, does not fit neatly into established manufacturing categories. That is, it does not directly take the place of processes such as CNC machining or conventional pattern making, largely because its successes come from enabling parts that these conventional processes could not have produced. Rather than competing with any one existing process, additive manufacturing does something larger: It collapses the overall sequence of processes, and it rewrites many of the established manufacturing rules. 

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