Collectors of rare cars, planes, boats, and this case, fire engines, are all too familiar with the challenge of finding replacement parts for worn out or damaged parts. Even if one is lucky enough to track down a replacement, there’s a good chance the part will be in poor condition.
Many collectors will spend weeks, months or even years trying to find rare parts – that’s because producing a replacement with traditional manufacturing can cost thousands of dollars in the development phase alone. What’s more is that few manufacturers are willing to spend time and resources to manufacture only one part.
3D technology and digital design software allow rare part seekers to explore a viable and cost-effective solution. 3D printing eliminates the need to develop expensive tooling that typically takes weeks or months to produce. If a worn out or damaged part is available, an experienced 3D designer can either 3D scan the original part to capture the digital data or use the part’s dimensions to draw up a new one with CAD. The latter was the case for Raise3D forum user Caxton3D, who needed to replace the water manifold on a 1913 Dennis Fire Engine.
Caxton3D says, “I hope that there will be more interest in the future for printing for ‘real world’ tasks. Pattern making is one of the most obvious applications. Most patterns today are still hand produced from wood.”
Due to the old age of the aluminum, welding would be too difficult and unreliable, which meant casting a new part was the best solution. However, when casting a part in metal, there are many variables that must be considered, such as the contraction of metal during cooling and the need for sand cores for hollow castings.
Different methods are available to cast large metal replacement parts using 3D technology. The most accessible process is Caxton3D’s approach – draw up a digital model with CAD, create a prototype on a 3D printer, test the fit and use the prototype as a pattern to create a sand mold. Another option, once the design has been finalized, is to directly 3D print a sand mold and core using a binder jetting process. However, large sand printers are very expensive to own and are usually not available to the public. In recent years, a number of pattern shops in the United States, including Humtown Products and Hoosier Pattern, have been directly 3D printing sand molds and cores for complex or low volume parts. Lost wax casting is also an effective method for casting replacement parts, but it’s usually not cost-effective for large parts like the water manifold.
The prototype was installed onto the original hardware to test the fit and identify alterations for the next revision. The final model needed to be printed slightly larger than the finished part due to the small amount of shrinkage that the metal will experience during cooling.
With the manifold design completed, the prototype was used to create a positive and a negative that can be molded from. Since the finished part needed to be hollow, a core was required, which will prevent the metal from flowing throughout the entire mold cavity and create a hollow part.
The manifold face and the core were incorporated into the design of the modified model. The extrusions from the core were used to secure the separately-molded sand core within the main mold box.
To create the sand core, a negative version of the model was 3D printed as a two-part mold. Due to the size of the part, which exceeds the N2 Plus’s build volume, each half was split into two parts and joined together to create the mirrored halves. To ensure alignment, Caxton3d added registration marks for bolts that will create a continuous core box.
To make the sand mold, the modified positive was pressed into two halves of sand to create the initial impression. One of the two halves received a gate for the metal to be poured into. The molded sand core was then placed inside the two sand halves. Molten aluminum was poured through the gate and once the part cooled, the sand was removed to reveal the final part. Some light machining was then required to remove excess metal from the gate area.
An additional benefit of using 3D technology for replacement parts is once a digital model is created, it can be shared with or sold to other collectors that need the same part. Eventually, many rare parts will be available online in the form of digital files, and then all that’s needed is access to a 3D printer.
What do you think of this application? Let us know your thoughts; join the discussion of this and other 3D printing topics at 3DPrintBoard.com.[Source/Images: Raise 3D]
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