Vibratory Tumbling (Vibratory Finishing) for SLS 3D Printed Parts

Vibratory tumbling, also known as vibratory finishing, is a well-established method of improving the surface hardness and smoothness of different materials. Traditionally used on metal parts to deburr them after machining or pressing, many manufacturers now rely on vibratory tumbling as a vital post-processing step for 3D printed parts as well. 

Specifically for selective laser sintering (SLS) 3D printed parts, which can sometimes have a slightly grainy surface, vibratory finishing can help make them ready for end-use or smooth their integration into functional assemblies. 

Read this guide for an introduction to vibratory finishing for SLS 3D printed parts and watch our webinar to see the full results of our tumbler comparison, testing results, and learn more about the workflow.

A vibratory tumbler agitates small pellets of media (typically metal, ceramic, plastic, or organic material like walnut shells) and the end-use parts to create friction, which smooths the surface of the parts and improves hardness. Vibratory tumblers are widely used due to their accessible size, affordability, and the range of benefits they provide without adding extra hands-on labor to the production cycle. 

Vibratory finishing provides two key benefits to the 3D printing workflow — improved functionality and improved aesthetics. Reducing the surface roughness allows moving components to operate with a lower coefficient of friction, making vibratory tumbling an ideal post-processing technique for applications such as printed hinges, actuating components, functional clips, and any other parts that are either moving or part of a moving assembly. The improved surface texture also improves porosity, making tumbled parts more resistant to fluid absorption.

The aesthetic benefits of tumbling are primarily the improved surface texture and cleaner appearance, but tumbling also provides a more consistent substrate on which to apply additional coatings, such as acrylic paint or Cerakote.

For any 3D print that will be handled as an end-use part, is part of a functional assembly, or has high visibility in a proof-of-concept prototype, vibratory tumbling is an easy way to drastically improve the surface hardness and smoothness for a 3D printed part. 

Vibratory tumbling machines for 3D printed parts can be broken down into two main categories — industrial and consumer. Industrial machines have a larger capacity and higher power requirements, and are typically priced around $5,000 or more. Industrial tumblers are suitable for production-level volumes, such as mass customization or stopgap manufacturing.

Many smaller vibratory tumblers can deliver the same end product as industrial tumblers, but have a smaller capacity and may take longer cycles of tumbling to achieve those results — these smaller machines may have to tumble parts for closer to 72 hours, compared to industrial machines at six hours. Industrial tumblers can easily handle multiple batches of parts, even medium-to-large parts, making them ideal for businesses like service bureaus or large-scale manufacturing.

There are many different options for media pellets to use in vibratory tumbling workflows, and choosing the right one will have a major impact on the outcome of your parts. Typical media include stainless steel, porcelain or silica, polyester composites, or walnut shells. Their effects range from aggressive smoothing and elimination of surface roughness to light polishing for aesthetic benefits. 

In some vibratory workflows, called ‘wet vibratory finishing,’ water or chemical detergents are added in with the pellets. The liquid helps temper the heat generated by the high friction and can help in removing contaminants or oxides on the surface of the part. However, detergents can be expensive and generate chemical waste, which has to then be disposed of and treated properly. 

^{From left to right: walnut media, ceramic media, and steel media.}

Many 3D printing applications demand a smooth surface finish and low coefficient of friction. Adding vibratory tumbling to your workflow can improve both the functionality and appearance of parts used in a variety of industries and settings. 

Some of the most common applications where smooth, tumbled SLS parts are required are: 

• End use goods: SLS printers excel at producing low- to medium-volume production quantities, and tumbling is a low-effort way of smoothing their surfaces in batches. 

• Healthcare: Surface roughness is a major pain point for 3D printed medical devices, models, and prosthetics and orthotics. When combined with tumbling, however, SLS printers add huge value to 3D printing workflows in the healthcare industry.

• Manufacturing aids: Using vibratory tumbling can improve their coefficient of friction and increase the surface hardiness, which leads to better durability and longer usage.

Formlabs has conducted extensive testing on vibratory tumbling in-house using SLS 3D printed parts in order to recommend appropriate workflows for optimal results. We 3D printed several parts based on one standard design that has flat and curved surfaces as well as interior and exterior surfaces. 

The Nylon 12 Powder and Nylon 11 Powder parts were printed on the Fuse 1+ 30W SLS 3D printer, depowdered in the Fuse Sift according to standard post-processing guidelines, and then tumbled in the CB300 vibratory tumbler, commonly referred to as Mr.Deburr for four, six, and eight hours. The parts were each measured before and after tumbling for dimensional accuracy using calipers and for surface roughness using a laser scanning microscope by manufacturer Keyence. To see the full results of our testing, download the white paper.

Vibratory finishing is an accessible method of making SLS 3D printed parts more similar in appearance and functionality to injection molded parts. Adding this process as a step in your 3D printing workflow doesn’t have to be complicated or expensive — there are many options for tumbling equipment that are affordably priced and accessible in terms of footprint and power requirements.