Soluble Cores

3D Printing Digital Manufacturing Tooling Applications

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3D Printing for Hollow Composite Parts

Soluble cores produced with FDM Technology simplify the production of hollow composite parts. They 3D print in one piece and can be dissolved after curing, eliminating labor-intensive mold making while accelerating your composite lay-up process.

Overview of the application

Soluble CoresHollow, composite parts present a unique manufacturing challenge. Cores are used to create the hollow features in composite structures when smooth internal surface finish and seam-free construction are required. Some cores can be easily removed because of the part’s design geometry, but any configuration that traps a core or mandrel inside it requires special, often sacrificial tooling.

Typically, sacrificial cores are made from eutectic salt, ceramic or urethane. These options present several challenges:

  • Can limit part geometry
  • Requires machined tooling to make
  • Uses harsh removal procedures
  • Difficult to handle, particularly fragile components

For these reasons, composites are more commonly laid up in clamshell tooling. If there is sufficient access to the interior of a closed clamshell tool, composite material is put into the mold and pressed against the cavity walls. For more complex geometries where access is a problem, the part must be cured in two halves and bonded together. This results in a seam that weakens the part.

Soluble CoresValue of using FDM

Sacrificial cores yield several performance advantages when used in place of clamshell tooling. For example, because the composite fabric is laid up on a male core, it can be favorably oriented and overlapped to create a seam-free part with optimal mechanical properties. Using a male tool also eliminates interior wrinkles, and provides control over interior accuracy and surface finish.

FDM is an additive manufacturing process that builds plastic parts layer by layer, using data from computer-aided design (CAD) files.

Sacrificial cores made with FDM technology use the same soluble material that’s used as support structure for FDM parts. However, unlike other core materials that require harsh methods for removal from the composite, FDM soluble cores are easily washed away in a detergent solution. This reduces the risk of damaging the part during core extraction. Additionally, FDM provides a much higher level of design freedom than other types of technologies. This allows the creation of more robust, complex cores that result in composite parts with improved performance and functionality.

FDM soluble cores are strong enough to withstand the temperatures and pressures associated with composite manufacturing processes. And, because the core is produced in an automated process and the composite can be laid up directly on the soluble core, much of the tooling and labor is eliminated. This yields substantial reductions in lead time and cost.

Benefits of FDM

Average lead time savings: 50% – 85%
From design to final part
Average cost savings: 75% – 95%
From design to final part
Reduced labor: Less tooling and setup
No bonding of composite sections
Hands-free core manufacturing
Improved composite parts: Single-piece construction
More features, including integrated hardware
Control over surface finish and accuracy
Core only: part’s internal surfaces
Core and mold: part’s internal and external surfaces
Lower risk: Minimal investment
Easier to modify
Greater durability
Improved consistency
Higher part yield

FDM is a best fit

Part geometry: Complex, hollow parts
Requires multi-piece molds
Bonding that yields a seam
Replace other core/mandrel production methods
Part requirements: Quantities: 1 to 100s
Good internal surface finish and accuracy
Composite manufacturing: Initial cure temperature:
< 121 °C (250 °F)
Can post-cure to higher temperature
Consolidation pressure:
< 550 kPa (80 psi)
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