The Finish Line: Post-Processing for AM

2017-10-25

Aya Bentur  

10XL additive and subtractive manufacturing in one hybrid system 3D prints object up to 20 meters

Our new series on the needs of the Additive Manufacturing ecosystem, #AMneeds, aims to shine a spotlight on what has been done, and what remains to be done in the process of industrializing additive manufacturing. To begin the series, we will start from the end – finishes and post-processing. When choosing additive manufacturing as your production method it’s important to examine the process from beginning to end, and that includes post-processing.

Finishing and post-processing are an integral part of any manufacturing process. Almost all forms of manufacturing require some sort of post-production. When it comes to additive manufacturing (AM) we expect the automated process to extend up to the finished part, yet AM isn’t that different from other manufacturing technology in that there are a number of steps required after the build process. Those steps vary depending on the sought-after result – industrial parts might need less post-processing while parts made for end users might call for more. Let’s take a closer look at what post-processing for additive manufacturing entails, how it differs from traditional post-processing, and it affects the AM process.

Not Just Good Looking

Touch and color are the first finishes that usually come to mind, yet post-processing isn’t limited to the aesthetics of the part alone. It includes steps that are fundamental to the form and function. The first need when it comes to post-processing for industrial AM starts with disconnecting the part from the build platform and removing support structures, which is done using CNC machining or wire electrical discharge machining. Of course, there is also cleaning and removing powder – all initial steps of post-processing (below an engineer at Airbus removes excess powder from a part). The faster and efficient these steps are the more cost worthy AM production will be.

An Engineer at Airbus removes excess powder from a part made by Additive Layer Manufacturing

Although surface finishes might sound like an aesthetic decision they have an impact on the functionality of the part. This includes creating a friction-free part or achieving geometrical accuracy. A smooth surface also relates to inspection methods, where a smooth surface is required in order to conduct contact ultrasonic testing (inspection for additive manufacturing is a need in itself – we will return to it in a future post). Heat treatment is another example of a finish for functional reasons, used to relieve stress caused by the printing process, and to avoid warping before removing from the printing platform. 

What’s the Difference?

3D printed interlocking metal rings before support removal - Photo via 3D Printing and Additive Manufacturing Journal

ic Berlin 3D printed polyamide frame finished with DyeMansion blasting and dyeing systems

Woodwork requires sanding, primer and painting. Casting begins with disconnecting the part, leading to vibratory polishing and deburring, plating/electroplating/anodizing, heat treatment, and even etching and engraving. Why is it that AM is considered more time consuming when it comes to post-processing? First, the time and cost of post-processing isn’t only related to the processing, but also to the number of processes and the ease of moving between them. Second, different materials and manufacturing methods call for different treatments, the additive technology and its materials lead to a need for new post-processing methods adapted to additive manufacturing. There are numerous examples, such as dissolvable support structures developed by researchers at Pennsylvania State University and Arizona State University (above), or the coloring system by DyeMansion (video below) used on ic!Berlin 3D printed frame (above).

Third, as a relatively new technology AM post-processing is not fully industrialized as in traditional manufacturing. This might lead to more manual post-processing. Ideally, a company strives to minimize manual post-processing phases, especially when it comes to industrial scale production. After automating manufacturing with AM, the next obvious need to be met is the automation of post-processing. Not only automating the post-processing itself but also the transition between steps, making the manufacturing process a fluid sequence.

Automated from Start to Finish

Producing with AM requires taking into consideration the process as a whole – from material to finish. After all, it’s important to note that after the build process, all actions are considered post-processing even assembly. AM can simplify the production of the form yet the finish and post-processing that follows have a significant impact as well. Sometimes it requires material removal which can influence the geometry and accuracy of the part necessary for its function. It’s important to consider that the material removed in post-processing should be calculated in the build geometry, especially when it comes to edges and critical dimensions. Automation starts with software being able to predict the process as a whole and simulate the result not only after the build process but at the very end of the process, minimizing iterations of trial and errors.

Better Together

2016 The Year in 3D Printing - HP Multi Jet Fusion 3D Printed Example

Service providers are also working on combining printing and post-processing in the machines as well as using automated robotic hands between phases. When it comes to machines, companies such as HP are incorporating more and more phases in the machines. HP’s Multi Jet Fusion process (above) incorporates steps such as detailing agents and heat treatment in the same machine, as a continuous print process instead of separate post-processing actions.

Dutch company 10XL developed a 3D printer that can 3D print objects up to 20 meters, combining additive and subtractive manufacturing in one hybrid system (below boat additively manufactured by 10XL, up top the hybrid machine). In their process they use synthetic polymers and bio-based materials, to these base materials they add materials such as glass, carbon, bamboo or stone as fillers in order to strengthen the end result, or additives which improve chemical, heat or UV resistance, flame retardants etc, instead of applying chemical treatments as post-processing.

Boat Additively Manufactured by 10XL

Different parts require different technologies, printers, and materials. The same goes for post-processing. Each part is different in terms of aesthetic and functional requirements, and will therefore require different post-processing techniques or a combination of post-processing techniques. The strength of the AM process is its ability to include and examine all phases of production, still, there are numerous post-processing needs that are not integrated and solved within the AM process. Jeff Mize, Chief Executive Officer of PostProcess Technologie spoke about the need: ”We continue to hear from our customers that the post-processing of parts is becoming the bottleneck in their additive operation”. PostProcess and other companies are already providing a number of solutions to address this need and are continuously working towards a smoother, faster, more accurate and automated process – from beginning to end.

Curious about other needs in the additive manufacturing ecosystem? Follow our #AMneeds series. For more inspiration and information follow us on Pinterest or subscribe to our newsletter for weekly updates.

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