Preparing 3D Printed Composite Tools

Manufacturing

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With the power of FDM technology, 3D printing composite tools have never been more accessible. In this piece, we want to cover different post-processing techniques for your 3D printed composite tooling parts. Traditional metal and FRP (fiber reinforced polymer) tooling typically require post-processing after the initial forming or milling processes. These steps include the assembly of support structures, the addition of inserts & bushings, and polishing to achieve the desired surface finish. Like traditional tooling technologies, FDM composite tooling, typically requires a level of post-processing depending on the size, application, and complexity of the tool. The most common post-processing operation for FDM composite tooling is sealing.

As-built FDM composite tools have an inherent porosity (see Figure 1) and surface finish that is unacceptable for most composite part applications. Therefore, a post-processing operation is needed to achieve the desired tool performance.

Illustration of the porosity resulting from the FDM build process.

Surface Finishing

There are a number of different techniques that are used to improve the surface roughness of the FDM tool surface including manual abrasion, media blasting, tumbling, and skim-coat machining. Currently, best practice to meet surface-finish requirements (<64 µin Ra) and vacuum integrity is manual abrasion followed by an application of epoxy sealer. To maximize adhesion, the process consists of two thin coats of a high-temperature epoxy sealer with light sanding before each coat. After the second coat of epoxy, a progressively finer grit sandpaper (120-800) is used to achieve the desired surface roughness. It is important to note that the goal of this process is not to smooth out layer lines but rather to fill the low points in the surface and remove any large peaks. The result should be a net zero dimensional change in the surface geometry while providing a smooth surface finish with vacuum integrity.

Views the epoxy sealer application (left) and manual abrasion (right) post-processing operations for FDM composite tooling.

Sealing

Like surface finishing, the inherent porosity in an FDM composite tool can be approached with the application of an epoxy sealer.

Additional methods for addressing surface preparation and sealing include the application of adhesive-backed FEP films. However, they can be difficult to apply to compound contours and are typically less robust than epoxy sealers- requiring replacement after just a few cycles. The unique properties of FEP films make them well suited to repair tooling and other situations, where few parts will be needed. Similar to conventional tooling, FDM composite tooling also requires some level of post-processing. Stratasys continually evaluates alternative post-processing methods and sealers to enhance performance and to simplify the finishing process.