Rapid Manufacturing with 3D Printed Casting Patterns

The casting process in one form or another has been around for centuries as it fundamentally has remained unchanged; molten metal is poured into a mold and left to cool, creating a metal part. The process today involves several steps and is designed to produce high volumes of casted parts. First a pattern must be created to make the mold that the metal will eventually be poured into. Making this pattern requires another mold which is created in a similar way that an injection mold tool is created. An aluminum or steel block of metal is machined into the shape of the pattern and then wax, or plastic, is injected into the mold to create the pattern. The pattern is then covered with layers of ceramic liquids that harden to form a shell. The plastic or wax pattern is then melted out of the shell and metal is poured in and left to cool.

This process, known as lost-wax casting or investment casting, is frequently utilized to fabricate casted parts. There are several advantages and disadvantages this process as well as new technologies available that make the casting process more efficient in certain scenarios. 3D printing being one of them, can offer some unique capabilities to both cut costs and shorten lead times for 3D printed casting patterns.

Traditional Casting Process

The traditional casting process, like injection molding, requires a special tool for each product that it makes. The tool can be used to create thousands of identical patterns, but fabricating it adds cost and lead time to the casting process. This can be unfavorable if the requirement is not to make thousands of identical units, but rather customized units or low volumes.

Advantages of the Traditional Casting Process

The advantage of the traditional casting process is that it can create mass quantities of parts for a low unit cost. Once the tooling has been invested in, the mold can create large quantities of patterns very cost effectively.

Disadvantages of the Traditional Casting Process

The disadvantage of the traditional casting process is that there is a large amount of setup and tooling time required to create a product. Two molds must be created, one to create the pattern, and one created off the pattern to make the metal part. For this reason, like injection molding, this process is not able to efficiently produce low volumes, products with high customization or complex designs, or multiple design iterations in the new product development process. For each new product iteration or prototype, a new pattern mold must be fabricated, dramatically increasing cost.

3D Printed Casted Patterns

3D printing can produce the patterns required to create a casting shell without the use of a mold tool. Rather than machining a mold tool, the 3D printer simply prints a pattern.

Advantages of 3D printed Casting Patterns

Because 3D printed casting patterns do not require tooling, low volumes of casted parts can be manufactured economically. Prototypes and small batches of casted parts can quickly and cheaply be built. Unlike the traditional casting method, 3D printing can create highly complex parts with fine details and individualized customizations on each unit. Almost half of the original process is eliminated by 3D printing foundry patterns which lowers the fixed costs and dramatically reduces manufacturing lead time. Rather than having to spend money on a pattern mold that will take weeks to make, a 3D printed pattern can be created on-demand in a fraction of the time and at a fraction of the cost.

Disadvantages of 3D Printed Casting Patterns

The only major disadvantage of 3D printed casting patterns is that there are not large economies of scale. The unit costs start much lower, but do not decrease significantly as the volumes increase as do the costs of many conventional fabrication methods.

3D Printing and Casting

When high volumes of identical units are needed, 3D printing will not be able to compete on cost with traditional lost-wax casting methods. However, investment casting with 3D printing is great for producing low volumes and products with high geometric complexity, fine details or customized features.

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