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Tech Focus: Surface Treatment & Repair Perfect surface finishes for 3D-printed components

Editor: Steffen Donath

Walther Trowal developed the ‘AM post process machines’, model range AM, especially for refining the surface of components produced with additive manufacturing.

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The “multivibrators” of the model range AM were specifically developed for finishing the surface of 3D-printed components.
The “multivibrators” of the model range AM were specifically developed for finishing the surface of 3D-printed components.
(Source: Walther Trowal)

Most 3D-printed components are produced by placing material layers on top of each other, creating a “staircasing” effect on their surface with, generally, a very high initial surface roughness. For this reason, many of these components must undergo a surface smoothing or polishing operation. Also, most of the time the markings of removed support structures and sintered-on powder residue must be removed, before the components can be further processed or utilised.

Walther Trowal explains, mass finishing has proven to be the ideal surface finishing method for 3D-printed components: These are completely embedded in the moving grinding media so that the process is very gentle and produces absolutely homogeneous and repeatable surface finishes. Moreover, the media also reaches internal passages and undercuts in the components.

The AM post process

Depending on the size of the processing bowl, up to 100 small work pieces or single components with a size of 900 x 500 mm can be treated in the model range AM of the new ‘multivib’ vibrators. The work pieces are mounted on a carrier plate, which in turn is clamped to the bottom of the processing bowl by mechanical or electromagnetic means. Once the work pieces are in place, the media is filled into the processing bowl. During the process compound and water are continuously added. Three vibratory motors induce an intensive vibration into the processing bowl. Since the vibratory movement generated by the motors is overlapping, the component surface becomes smoother, while the edges are left intact. After a pre-determined cycle time the process is completed, and the finished work pieces can be removed.

Maximilian Beien, sales manager at Walther Trowal, considers additive manufacturing and mass finishing as a perfect match: “Additive manufacturing and mass finishing are an ideal combination because most 3D-printed components must have an excellent surface finish to fulfill their function. For example, turbine blades require an airflow with minimal friction loss. Components with stringent specifications for hardness and strength benefit from the homogeneous peening effect induced by mass finishing. This finishing method is especially advantageous for 3D-printed components with bionic shapes.”

Small footprint

It should be noted that the Walther Trowal grinding media and other consumables are already approved for many materials and safety-relevant components and processes, the company states. Beien especially points out the high cost efficiency of the “trowalising” process in conjunction with additive manufacturing: “Compared to electro-chemical finishing methods mass finishing achieves the desired surface smoothness and luster in one single operation. Another advantage is that the mass finishing equipment is very compact with a small footprint. The result: An excellent surface finish, surprisingly short cycle times and an overall high cost-efficiency, the company concludes.

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