According to reports on the latest technologies, post-processing is still a significant obstacle to the popularization of 3D printing in the industry. It is no surprise that companies from the 3D printing industry are intensively looking for solutions that will optimize the process of finishing finished parts. One of them is ExOne, a company that is the most important supplier of equipment working in Binder Jetting technology.

Their proposed Washout Tooling application facilitates standard post-processing of elements that must remain empty in funds, and in addition to low weight, they must be of adequate mechanical strength. Their 3D printing method of water-soluble cores facilitates the formation of components from composite materials (such as carbon fiber or glass). So far, the process of cleaning printouts from residual materials has been time consuming and required a variety of measures – from solvents and chemically aggressive detergents to standard tools for mechanical removal of unbonded material.

The ExOne research and development team has been able to find an alternative to standard post-processing methods used for their proprietary, incremental powder technology. Their Washout Tooling application allows the 3D printed core to dissolve under running water, without the need for chemically aggressive agents. The solution is currently used to create carbon and glass fiber-enriched structures by Lockheed Martin.

Washout Tooling

ExOne engineers have developed a method of creating 3D prints from sand using a binder different from the classic sand prints, which can be successfully cleaned under running water. What does the process look like for the Washout Tooling application?

The finished core model is 3D printed and cleaned of some unbound powder. The core is wrapped with a layer of Teflon tape, and then plastic composite material is applied to it. Teflon tape is used to prevent penetration into the 3D print of the resin, which is the matrix for carbon or glass fiber. Then, the whole is placed in an autoclave to give the composite material the right shape. At a further stage from the inside of the element, a stream of running water is thoroughly rinsed the sand residue from the inside of the detail. Below is a video illustrating the whole process:

In the classic approach, such cores are either fired (e.g., plastic or foam cores) or are flushed with aggressive chemistry, which in both cases causes a weakening of the composite geometry. In extreme cases, when the agent does not have to be empty, simply leave them permanently, while agreeing to increase the weight of the finished element.

The solution proposed by ExOne allows not only the creation of composite details with better mechanical properties, but also gives the possibility of creating closed geometries of very complex and irregular shapes.

Source: Manufacturing Engineering, December 2019 via

Paweł Ślusarczyk
CEO of 3D Printing Center. Has over 15 years' experience in buisiness, gained in IT, advertising and polygraphy. Part of 3D printing industry since 2013.

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