What 3D printing technology can revolutionize a 2,700-year-old technology, open new doors in modern architecture, and rejuvenate critical infrastructure? That would be a sand 3D printer. Find out all about it!
As the name states, a sand 3D printer uses a working medium of sand-like materials, including actual silica sand, ceramics, or even metal particles. The technology is binder jetting, which uses a binder polymer to bind the particles together into a physical 3D model. This can be used to produce finished products or molds for an alternative material to be poured into.
The history of sand 3D printing begins in the late 1990s with a German company, Generis, and with MIT (Massachusetts Institute of Technology) in the United States. Generis focused on sand 3D printing for metal casting molds while MIT developed and patented the 3DP metal binder jet technology. Their work led to the first commercially-available printers offered in the mid-2000s. Licensing arrangements and the division of Generis lead to today’s two main champions of the technology, VoxelJet and ExOne.
A sand 3D printer shares many of the functional attributes of other 3D printing methods. It uses a layer-by-layer printing process that allows the creation of parts with complex internal and external geometries. These layers are defined by slicing the computer part models into thin sections. The sand particles are bound together by a binder “glue” that solidifies the particles into the 3D shape. The average particle size is 140–200 micrometers.
Most 3D printing technologies use heat to process working material into final parts. This may be laser energy that melts or sinters the material or just electrical heaters that melt plastic so it can be dispensed in a thin molten stream. In contrast, a sand 3D printer does not use heat. It works like an inkjet printer, but instead of ink onto a piece of paper, it prints binder onto a sand layer. The binding agent can also include pigment to print in color.
The “no heat required” design of the sand 3D printer leads to a very important advantage over other 3D printer technologies: it can be easily built to form very large parts. 3D printers that use heat in their process require added energy and insulation, which limit their size. However, build volumes up to 13.1 x 6.6 x 3.3 ft (4 x 2 x 1 m) are commercially available in sand 3D printers. Even with these large build volumes, resolutions of 600 DPI (dots per inch) and layer thicknesses of 0.3 mm are printable.
Sand 3D printing begins by leveling the first thin layer of sand onto the build platform. The printer head traverses the sand layer while it extrudes the binder in the pattern needed for that layer. The sequence of dispensing, leveling, and binder extruding continues until part completion. The additional sand in the build platform remains as the support material for coming layers, meaning no additional supports are needed.
When the part is finished, any loose sand is carefully removed. Post-processing may include further cleaning, impregnating the part for increased strength, or sintering and binder removal for metal powder parts.
Sand 3D printers are very versatile. They can be useful for creating intermediates for construction or for parts that need a higher strength or different material than sand 3D printing can offer. It also can be used with materials other than sand.
Below are a few different ways sand 3D printers are being used today.
Metal Sand Casting
Metal sand casting is an ancient metalworking technology that originated in China in 700 BC, and it continues to be a major aspect of metalworking today. So how did 3D printing revolutionize such an old technology?
The first step in sand casting is to make an exact model (pattern) of the final part. Typically this is made of wood, wax, or clay. This is a time-consuming process that requires a very skilled craftsman to create each part of the pattern perfectly while also understanding how the molten metal will react, flow, shrink, and solidify in a mold.
Casting sand is then packed around the patterns inside a holding box (cope and drag) to create a mold. If the model was made of wax, it can be left in the mold to be burned out when the molten metal is poured in. However, the mold has to be constructed in parts if a wooden or clay pattern is used to allow the pattern to be removed before casting the metal.
Sand 3D printing turns the traditional sand casting process on its head by creating a mold directly with all of its complexity and multiple parts in one. It also has reproducibility and is easily adjusted if the finished mold isn’t quite right. In addition, the large print bed volume allows bigger molds to be made. Revolutionary!
Sand 3D Printing of Concrete Forms
An exciting new application for sand 3D printing is to print complex shapes for architectural design. Researchers at ETH Zurich have been researching how to use a sand 3D printer to create molds for concrete.
Concrete can make up as much as 80% of commercial structures today. With this much material demand architects and engineers are constantly looking for a way to reduce material consumption while maintaining the strength. This is not an easy task with conventional flat concrete forms, but by 3D printing forms on a sand 3D printer, the concrete can be sculpted to just the right shape and thickness.
With a sand 3D printer the architect is free to design the shapes and artistic elements that enhance the design. 3D printing concrete forms opens new doors in designing structures with new shapes, sizes, and features that are impossible to achieve with other construction methods.
Direct Printing of Metal Parts
My replacing the sand for metal powder, a sand 3D printer can be used to 3D print metal parts directly. Metal 3D printing is especially intriguing for industries, where there is often a need for replacing large metal parts that are no longer manufactured.
Instead of making an expensive replacement design, a large metal part can be 3D scanned and computer modeled. That model can then be directly printed on a sand 3D printer with metal particles instead of sand. It’s important to note, however, that the finished part will not be strong enough straight off the printer since the metal particles are just glued together. Post processing is required to achieve the desired strength. This can include impregnating the part with a molten metal or pressing and sintering the part.
Through this method of using a sand 3D printer, a completely usable replacement metal component can be made directly. This process saves time and money, and the large print volume of a sand 3D printer makes larger parts buildable in one piece.
Sand 3D printers have already made their mark in several industries. What attributes and limitations will guide the future of sand 3D printers?
Feature image source: Hoosier Pattern Inc.
License: The text of "Sand 3D Printer – What Exactly Is It?" by All3DP is licensed under a Creative Commons Attribution 4.0 International License.
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