Post-Processing Enabling Additive Manufacturing

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Post processing, in one form or another, is an inevitability when using additive manufacturing (AM) technologies, but is particularly critical for serial production applications of AM — both in terms of the financial costs and the time it takes between a part leaving the AM system and being fit for purpose as an end-use product. In this article, Joseph Crabtree, the CEO at Additive Manufacturing Technologies Ltd, considers the importance of post-processing in the entire production process chain and highlights an emerging solution.

Undoubtedly there are many benefits associated with the use of additive manufacturing (AM) as a production technology. On a pan-industrial basis, manufacturers exploit the fact that through the use of AM they can not only build complex parts, in one piece, which were previously impossible, but they can also build stronger, lighter weight parts, reduce material consumption, and benefit from assembly component consolidation across a range of applications. These advantages have all been well documented during the last 10-20 years as AM has emerged as a truly disruptive technology for prototyping and production, and are invariably seen as being enabled by the additive hardware that builds the parts. In reality, however, this is a partial picture, particularly for serial production applications of AM. AM hardware systems are actually just one part — albeit a vital part — of an extensive ecosystem of technologies that enable AM, both pre- and post-build.

By focusing just on the AM build process, a fundamental part of the production process chain is often overlooked, namely the post-processing steps once the part is out of the AM machine. Manufacturers using (or considering using) AM for serial production applications need to first identify the appropriate additive process for their targeted application. From there the post-processing requirements must be identified and focused on, otherwise the use of AM as a viable alternative to traditional manufacturing processes may end up being negated completely.

The PostPro3D BLAST process can achieve a consistent surface finish on non-line of sight organic lattice structures.

Post-Processing for AM

Post-processing is actually an umbrella term for a number of stages that AM parts may need to go through after they come out of the AM system and before they are fit for purpose. The term “post-processing” is often used interchangeably with “finishing”, which is somewhat confusing. With many processes, there are a series of essential post-processing steps that must be undertaken prior to the AM-produced part finishing stages. Thus “finishing” is actually a subset of post-processing, not a term that should be used interchangeably with post-processing.

Post-processing can include any or all of the following:

• Excess Material Removal

• Curing / Heat Treatment

• Support Removal

• Machining

• Surface Finish Processes (such as bead blasting)

• Colouring

• Inspection

So saying, post-processing is often the elephant in the room when it comes to the uptake of AM as a production tool. For AM production applications, post-processing is a considerable element of the overall cost-per-part, and can be anything up to 60% of total cost depending on application. Support removal and other post-processing activities are often labour intensive, and therefore cost- and time-consuming. In addition, there is often a necessity for post-processing to enhance final part characteristics, in terms of functionality or aesthetics.

EOS PA2200 material smoothed and coloured in one step. Engineering valve application, where sealed surfaces are critical to prevent fluid ingress.

This is why the issue of post-processing is so important when looking at the viability of AM for serial production, because it is often the area where the technology falls down as a competitive manufacturing technology. The post-processing conundrum needs to be confronted head on with an ecosystem approach to each individual application — from end to end. This means joining the dots from product conception through to final product.

To a certain extent, post-processing can be cauterized by a focus on design for AM  (DfAM) to reduce the necessary post-processing steps. Success here will depend on how well the designer understands the intricacies of the AM process and the specific capabilities of the AM system they are using, how to orientate the parts in the machine(s), and how to generate optimal support structures for build and removal. In general, post-processing requirements for a given application depend on the geometry of the component and how well it is designed for manufacturability using AM.

However, regardless of how well a product is designed for AM it cannot negate the need for post-processing for all AM processes. The problem is that for an industry that calls itself disruptive, manufacturers are still largely post-processing parts the same way they did 100 years ago, with the requirement of significant manual intervention. And it is this that is slowing the whole process chain down for production applications of AM.

An Innovative Approach to AM Post-Processing

The fundamental mission of Additive Manufacturing Technologies (AMT) Ltd is to confront this problem head on through the development of a series of innovative digital and automated post-processing solutions that increase efficiency and reduce the overall time and costs of production with AM, specifically with polymer AM processes and thermoplastic materials.

There can be no argument about the increased number and improved nature of the thermoplastic materials palette available for AM processes in recent years. Alongside these material developments, the AM systems that produce thermoplastic parts have also significantly improved in resolution, accuracy, repeatability and overall quality, and they are therefore consistently meeting industrial requirements for exacting prototyping, tooling, and some production applications.

However, the critical mass of production applications remain lower than they otherwise might be due to previously mentioned limitations placed on the overall process chain by the post-processing phase. This is because powder-bed processes — which require significant powder handling and removal post build — also invariably require infiltration operations, as well as finishing processes, particularly if aesthetics are important alongside the strength advantages that laser sintering offers. If coloured parts are required, then this is also applied at the finishing stages of post-processing.

With filament thermoplastic material processes, the very nature of the AM process (no matter how refined) results in a stepping effect. The traditional post-processing steps required to eliminate these process-specific results are considerable, costly, and time consuming. However, an automated post-processing solution for smoothing high volumes of thermoplastic polymer parts to an injection moulded surface quality would remove one of the biggest hurdles to the serial production process chain. Here, I am talking about parts 3D printed using the Laser Sintering , Multi Jet Fusion, High Speed Sintering, and Fused Deposition Modelling processes for specific material types including Polyamide/Nylon, flame retardant Nylon, glass filled Nylon, ULTEM, PMMA, TPU, and TPEs.

The PostPro3D machine from Additive Manufacturing Technologies.

This is exactly the solution that AMT envisaged, developed, and commercialised with its PostPro3D® range of hardware, which integrates new systems, software and virtual services. The simplicity and speed experienced by the user belies the intelligent and complex capabilities of the system, which is built on the proprietary BLASTTM process.

Simplicity is the key. Post-build, the 3D printed parts can be removed from the machine, loaded onto a rack, and placed into the PostPro3D® post-processing chamber. The user then selects the appropriate program and the process starts and runs for 90-120 minutes, after which the parts can be removed, inspected, and are fit for purpose.

For anyone that is wondering what happens to the parts during those 90 to 120 minutes, they are subject to a physiochemical process that involves converting a proprietary but wholly safe solvent into vapour under precisely controlled vacuum and temperature conditions. In turn, this precisely refines the surface of each part to ensure a perfectly smooth finish, equivalent to that of an injection moulded part. Moreover, the process also seals and strengthens parts, essentially improving their mechanical properties— such as elongation at break — compared with how parts were when they came out of the 3D printer.

The intelligence of the PostPro3D® systems goes beyond their physical process capabilities however, as they have been designed to be connected through an IIoT network, where vital data is analysed in real-time. This allows for new insights on process performance, which can subsequently be shared amongst the global fleet of PostPro3D® machines, and made available via software updates to continually upgrade performance, all while protecting individual IP. Moreover, this connectivity capability also allows for integration with other intelligent devices and workflow automation software across the production process chain.

Summary

What all of this points to, I believe, is the continued need to work towards developing whole process chains that will help to convince AM users, and potential AM users, that the transition to AM for an increasing number of production applications is worthwhile and not nearly as complex as it may have been, even a few years ago. This demands a unified approach — across the AM sector itself — to develop more capable and connected systems, while simplifying the overall process to provide economically viable, automated solutions. This can be achieved through partnerships and collaboration, and AMT is proactive in this area working in partnership with Mitsubishi Electric with its current commercial activities, and other companies that we will be able to talk about in more detail in the future as new solutions are commercialised.

Automated turnkey hardware for post-processing — such as the commercially available PostPro3D® range — is certainly a huge step forward for the post-processing stage of the production process chain with AM. However, there are still more steps to take, in terms of wholly connected, customized, end-to-end digital manufacturing systems. That is the area in which AMT is operating in order to bring practical industrial solutions to OEMs using AM as a production technology.

Joseph Crabtree, CEO, Additive Manufacturing Technologies Ltd

Joseph Crabtree is the founder and has been the CEO of Additive Manufacturing Technologies since 2017. AMT is based in the UK, with global reach through facilities in the US and mainland Europe, as well as collaborative partnerships across the world. The company is currently emerging out of semi-stealth mode and into full production. AMT’s technology is developed at the intersection of material science, chemistry, hardware engineering, robotics and machine learning. The vision is to deliver safe, sustainable and economically favourable industrialised additive manufacturing solutions that offer a real and viable alternative to traditional manufacturing. 

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