Selective Laser Sintering (SLS) is ideal for producing intricate, functional parts straight off the printer.
However, post-processing can enhance the functionality, appearance, and durability of parts to meet specific application requirements. This article explores the best post-processing techniques for SLS 3D printed parts, focusing on finishes like:
- Colouring
- Painting
- Adding inserts
- Shot peening
- Vibro-polishing
- Metal plating
All of these finishing techniques are available through the facilities at Prototal UK in Berkshire.
The Different Post-Processing Techniques for SLS Parts
1. Colouring (Dyeing the Plastic)
Dyeing is a cost-effective and versatile way to colour 3D printed parts. It’s particularly beneficial for industries looking for vibrant, uniform finishes. It’s one of the more common post-processing techniques as parts printed from the same material can be quickly identified using this post-processing method.
Colouring SLS parts involves submerging the part in a dye bath, allowing the colour to permeate the material. This is done after any other post-processing techniques (sanding, for example) to ensure a uniform colour.
Colouring is a great option for parts that require differentiation or branding. It doesn’t add thickness or interfere with part dimensions. It also penetrates about half a millimetre into the surface of the part, so it’s a much more robust finish than paint, for example.
2. Painting
We have a fully equipped paint shop at Prototal and offer just about any colour imaginable. We can also offer matte, gloss and textured finishes, something that isn’t possible with the dyeing process. This sophisticated post-processing technique produces stunning finishes for prototypes and concept pieces but also final parts.
The high-quality paints we use also add a layer of UV and environmental protection. This makes painting ideal for parts exposed to outdoor or high-wear environments. It’s also excellent for visualising a final production part or adding the final touches to production parts.
3. Welding
When SLS parts exceed the build chamber size or require multiple sections, we can use welding to join them seamlessly. Welding techniques specific to polymer parts, fuse components without compromising the material’s strength. This process allows us to create large and complex structures while preserving structural integrity and dimensional accuracy.
In the past, we’ve used this technique to build entire F1 car body panels, but the limits are endless. No matter the size of your parts, we can print and assemble them.
4. Bonding
Bonding involves using adhesives to join SLS parts or to attach components made from different materials. With appropriate adhesives, bonding can produce robust joints that are just as strong as the base material.
This method is particularly effective for complex assemblies that mix materials or require specific sealing, such as enclosures or high-strength housings. We’ve used bonding to build full-size engine block models, as well as scale oil rig models in the past, but it can be used for critical production parts too.
5. Adding Inserts
Threaded inserts and bushings are often embedded into SLS parts as a way of joining components or strengthening areas that are subjected to high stress or wear. Insert installation during post-processing adds durability and functionality to the part, allowing it to withstand torque, impact, or mechanical loads.
This approach is especially useful for applications requiring secure fastening or connection points and is a very common post-processing technique for parts made using selective laser sintering here at Prototal.
6. Shot Peening
Shot peening compresses the outer surface of polymer parts and creates a more uniform finish. It’s a particularly useful post-processing technique for parts we are colouring as it provides a more uniform surface finish.
The surface finish of shot peening isn’t as smooth as vibro or vapour treatments but it still offers a lot of improvements over the surface finish straight off the printer. Shot peening also creates compressive residual stress that enhances surface durability and fatigue resistance. This technique is critical for parts used in high-stress environments, as it helps prevent cracking and increases the lifespan of a part.
7. Vibro-Polishing
Vibro-polishing, or vibratory finishing, is a common post-process for SLS parts where parts are placed in a vibrating container with polishing media. This smooths the surface, removing layer lines and minor imperfections. Vibro-polishing builds a very professional finish making it ideal for applications where aesthetics are key.
As SLS parts do not have support material or support structures, thanks to the printing process, they can often go straight from the print bed to the vibro-polishing machine, as can parts printed on fused deposition modelling machines. For parts printed on other machines, we have other post-processing systems in place to ensure that we can achieve high-quality finishes on any parts we produce.
8. Metal Plating
Metal plating adds a thin layer of metal, such as copper or nickel, to the surface of an SLS part. Plating can improve wear resistance, provide a conductive surface, and offer a high-end metallic finish. This process is great for parts requiring durability, electrical conductivity, or electromagnetic shielding, such as those in the aerospace or energy sectors.
We currently offer metal coating/plating for nylon 12 and glass-filled nylon 12 parts and the process can greatly improve the functionality and strength of 3D printed parts.
A Quick Look at Finish Thicknesses
Our finishing capabilities at Prototal UK are second to none. However, many of the finishes mentioned above add additional thickness to the final part. If your part mates with another, or needs to hit a critical dimension for other reasons, make sure you take this additional thickness into account when designing your part.
Our team of additive manufacturing engineers are more than happy to discuss layer thickness with you throughout the design process and recommend the best finishing technique for your prototype or final part. We’ve also cover 3D printing tolerances more in another blog post.
Maximise SLS Part Potential with Tailored Post-Processing
Each technique we’ve talked about – whether for aesthetic, functional, or durability enhancement – can significantly impact the performance and quality of the final part. Our post-processing options are the best in the world. So, get in touch to discuss your parts today and our team can offer advice on the best post-processing techniques for your needs.