How 3D Printing Works

3-D printing works much like a 2-D printer in a home or office. However, instead of paper, this process uses paper- thin layers of a special foundry grade sand and a specifically engineered binder to create foundry mold components. The process has only a few steps that are repeated until the desired shape is produced. The sand is spread and the binder is selectively dispensed, guided by computer aided design (CAD) data.

The build platform is then lowered by a set increment and a new layer of sand is spread. The binder is then applied again to this new configuration using the CAD data. The process is repeated until the part is built to completion. At that time, the part can be extracted from the surrounding sand and used in foundry applications.

What Is It & How Does the sand 3D Printer Works?

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. 

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.

What are the advantages of sand 3D Printeing ?

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.

Application:Pump Component Molds

The sand, hardened with the specifically engineered bonding agent, can be used to make cope and drag mold halves and cores. These are the basics of foundry components. The printed sand can also be used as a representation of the part for form of mock ups or as an engineering model. It provides a tactile representation of the part that can be used for fit and even fixture setup in the machine shop. Painted, it looks like a sand casting and weighs about 0.06 pounds per cubic inch.

This sand can be used to make a core for any of the conventional molding techniques in a foundry and is safe for use with any alloy. This core could be complex and would not need any assembly because the 3-D printing process eliminates the need for conventional tooling, such as core boxes. One advantage of having no core assembly is that the internal cored passages of the casting are cleaner with no fins at the core assembly joints and no casting defects from poor core assembly or missed mudding at those joints.

This 3-D printing process results in less post foundry cleaning of the internal passages, which produces better internal pump passages. This internal core could also be made with no draft, which may provide better pump performance or efficiency.

Flexibility

Another benefit of this printed core is the ability to change it whenever needed. No tooling charge is assessed to make a change. If the pump housing pattern is of sufficient design and all an end user needs is to upgrade the internal passages, then print them with no tooling and no fuss. This can be a great advantage for one-offs or samples.
 

Many people like to try something before investing heavily in permanent tooling or to prove an engineering idea. The 3-D printing process allows for sampling without being penalized by the high cost of foundry tooling and the associated long-build cycle time for that tooling.

The printed sand could also be made into foundry molds. These molds can be printed to mimic any molding process so the foundry can gather valuable information as to mold fill, solidification and yield. This helps foundries refine, prove out and optimize the process before tooling is ordered, which eliminates tooling changes at the startup of production. For speed to market, 3-D printing can help when castings are required immediately and tooling is still weeks or months away from completion. One of the mantras of additive manufacturing is to make just what end users want when they want it.

Additional Benefits

For legacy products, 3-D printing has great promise. Damaged foundry tools would not have to be replaced or repaired for those jobs that only run occasionally. Lost tooling would not need to be replaced. A company can print the solution and use whatever tooling is available.

Again, this is not an all-or-nothing technology. Mix and match to keep cost low and only make what is needed when it is needed. In the future, patterns may be stored on a server or flash drive and not in a warehouse.

The more complicated the casting and the more difficult the core is to manufacture, the more manufacturers and end users should experiment with 3-D printing as a solution.

This change in how pump components are manufactured can save money and time and get parts and products to market faster. Engineers can also test multiple solutions simultaneously before committing to expensive permanent tooling. They do not need to compromise design efficiency for the quick ability to manufacture the product.

Starting the Process

End users should investigate and try this technology. To start the process, they should communicate with a 3-D printing technology provider. Good communication and coordination with the 3-D provider is important. Users should have an honest discussion of the risks involved and what is most important to them-such as cost, quality and time. They should use their time with the provider to have the technology explained, and they should ask the provider what it can and cannot provide.

Users must understand that not everything can be manufactured using 3-D printing, nor should it be. Bad experiences with any new technology are costly for everyone. Solution providers, manufacturers and end users should avoid using a good solution on the wrong problem.

By finding the right match of vendor capabilities and processes for the application, end users should be able to make their component faster and for less money. This technology can save money on prototypes and production work. Manufacturers and end users should research to determine if 3-D printing is an option for them.