Some form of post-processing is inevitable when using additive manufacturing (AM) technologies, but particularly for serial production applications. Joseph Crabtree considers the importance of post-processing in the production process chain and highlights an emerging solution.

There are undoubtedly many benefits associated with the use of AM as a production technology. Manufacturers can not only build complex parts in one piece that 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 been well documented during the last 10-20 years as AM has emerged as a truly disruptive technology for prototyping and production, invariably seen as enabled by the additive hardware that builds the parts. In reality, however, this is a partial picture, particularly for serial production applications. AM 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 post-processing once the part is out of the AM machine. Manufacturers using (or considering) AM for serial production applications need to first identify the appropriate process for their targeted application. From there the post-processing requirements must be identified and evaluated – otherwise the use of AM as a viable alternative to traditional manufacturing processes may end up being negated completely.

Post-processing for AM

Post-processing is actually an umbrella term for a number of stages that parts may need to go through after they come out of the AM system and before they are fit for purpose. Post-processing can include any of the following: excess material removal; curing/heat treatment; support removal; machining; surface finish processes (such as bead blasting); colouring; and inspection.

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, representing anything up to 60% of total cost. Support removal and other post-processing activities are often labour-intensive, and therefore costly and time-consuming. In addition, there is often a necessity for post-processing to enhance final part characteristics, in terms of functionality or aesthetics.

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-based approach to each 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 cauterised 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 system they are using; how to orientate the parts in the machine; 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 this is slowing the whole process chain down for production applications of AM.

An innovative approach to AM post-processing

The fundamental mission of my company, Additive Manufacturing Technologies Ltd, is to confront this problem head on through the development 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 consistently meeting industrial requirements for exacting prototyping, tooling, and some production applications.

However, the critical mass of production applications remains lower than they otherwise might be due to the 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, this is also applied in 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.

This is exactly the solution that we envisaged, developed, and commercialised with our 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 BLAST 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 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 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, as they have been designed to be connected through an Industrial Internet of Things (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.

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 was 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 – Additive Manufacturing Technologies Ltd has been proactive in this area, working with Mitsubishi Electric and several other companies.

Automated turnkey hardware for post-processing — such as the 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, customised, end-to-end digital manufacturing systems.

Joseph Crabtree is the founder and has been the CEO of Additive Manufacturing Technologies.