Introduction
Post-processing is a critical stage in the HP Multi Jet Fusion (MJF) 3D printing process, significantly impacting the final part’s appearance and mechanical properties. Understanding the primary and secondary post-processing stages and their best practices is essential for achieving optimal results.
Primary Post-Processing – Cleaning:
The primary post-processing stage involves removing excess unfused material from the printed part’s surface, crucial for preserving the part’s look, feel, and dimensional accuracy.
Techniques for Primary Post-Processing:
- Bead Blasting: This involves propelling glass beads at high pressure against the part’s surface. Bead blasting provides a uniform “satin” finish and does not affect the part’s dimensional stability. Both manual and automatic bead blasting systems are used, with the latter allowing for simultaneous processing of multiple parts.
- Air Blasting: Often used in combination with bead blasting, air blasting involves propelling a stream of compressed air onto the part’s surface. It helps remove any remaining powder material and blast media dust.
- Water Jet Blasting: This technique uses a fluid mixture of compressed air and water to remove powder. It is especially effective for cleaning complex geometries or ducts and can slightly reduce surface roughness.
Considerations for Bead Blasting:
- Blast Media: Glass beads (70–110 µm diameter) are recommended for MJF parts. They ensure no dimensional accuracy alteration and provide a more uniform surface.
- Air Pressure: Adjust air pressure based on the blasting system (manual or automatic) and the part’s fragility.
- Nozzle Diameter and Distance: The nozzle diameter and distance to the part significantly impact the cleaning effectiveness.
Water Jet Blasting Advantages:
- Complex Geometries Cleaning: Ideal for intricate parts due to different nozzle orientations.
- Reduced Surface Roughness: Can achieve smoother finishes compared to traditional vibratory systems.
- Dust-Free Environment: Eliminates the need for subsequent processing to remove blast media dust.
Secondary Post-Processing: Cosmetic and Surface Roughness Reduction:
Secondary post-processing includes techniques that provide cosmetic attributes or reduce surface roughness. These include dyeing, painting, vibratory tumbling, and chemical polishing.
Key Factors in Secondary Post-Processing:
- Dyeing and Painting: These methods can enhance the part’s visual appeal but may impact dimensional accuracy.
- Surface Roughness Reduction: Techniques like vibratory tumbling or chemical polishing improve the part’s tactile feel and appearance.
Conclusion
Effective post-processing in HP Multi Jet Fusion printing requires a strategic approach, considering the part’s application, material, and desired properties. By meticulously applying primary and secondary post-processing techniques, manufacturers can significantly enhance the quality of their 3D printed parts, ensuring they meet both functional and aesthetic requirements.
