Joseph Crabtree, CEO, Additive Manufacturing Technologies Ltd
The concept of sustainability and safety in the use of additive manufacturing (AM) has been an area of discussion for a few years now. However, with the shift to post-processing when using additive manufacturing technologies, the time is right to look at sustainability and safety in AM more forensically.
Additive manufacturing and sustainability
AM enables more cost-and resource-efficient small to medium scale production and is forcing manufacturers to reassess their approach to manufacturing. As a disruptive and enabling technology it opens up the ability to manufacture parts and products with almost unlimited complexity and atypical geometries and features.
From a 6-mile high view of the world, the AM process is less wasteful than conventional subtractive manufacturing processes, and enables:
1. Better resource efficiency (manufacturing processes can be redesigned for AM)
2. Extended product life (through approaches to repair, remanufacture, and refurbishment)
3. Reconfigured value chains (which are shorter, smaller, more localized, and more collaborative)
Much of the emphasis on AM’s effect on sustainability has focused on reduced energy and material consumption. But a true understanding of AM’s effect on sustainability needs to be more comprehensive, and assess how AM enables more sustainable models of production and consumption.
Looking at ways in which AM can enable more sustainable methods of production and consumption from a product lifecycle perspective, there are four key areas in which AM enables environmental sustainability benefits:
1. Product and process redesign
2. Material input processing
3. Make-to-order component and product manufacturing
4. Closing the loop (basically recovering and reusing AM materials, promoting the manufacture of parts when needed thereby reducing need for wasteful inventories etc)
AM has a role to play as companies move to more environmentally sustainable industrial systems with its effect on consumption and production. But it also promotes the opportunity for manufacturers to assess alternative business models. A move to direct digital manufacturing, for example, will mean that digital designs will be kept on file, and can be reproduced as spare parts for repair and remanufacturing, which will mean product life extension and incentivize product-service business models. Such shifts would affect the distribution of manufacturing and begin to reconfigure value chains. AM’s ability to reduce the need for sub-components and assemblies also simplifies supply chains.
AM post processing
It is important when looking at the use of AM as a production technology to analyze all the steps involved from product design to final end-use product or component, including the post-processing stage for AM.
Many manufacturers underestimate the post-processing requirements when using AM, so it is often the Achilles heel of the process and can be a barrier to the use of AM as a production tool. What many manufacturers are unaware of is that when using AM production applications, post-processing can be up to 60% of the total cost per finished part; surface finishing and other post-processing activities are often labor intensive, and cost and time consuming.
The post-processing puzzle needs to be addressed with an ecosystem approach to each individual AM production application — from end to end. Some post-processing issues can be reduced through diligent focus on design for AM (DfAM), but however good the design, it cannot negate the need for post-processing for all AM processes. Here at AMT we are only too aware of the irony that AM can require almost pre-historic levels of manual intervention at the post processing stage, slowing the entire process chain down for production, and potentially affecting the geometric and functional integrity of finished parts.
There are 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.
A number of thermoplastic materials are available for use on a variety of AM platforms, but powder-bed processes require powder handling and removal post build, and also usually require infiltration operations, as well as finishing and coloring processes, particularly if aesthetics are important alongside the strength advantages that the powder bed fusion technologies offer.
Filament thermoplastic material processes typically produce a stepping effect on built parts, which can be costly and time-consuming to eliminate in post-processing processes.
There are automated post-processing solutions for smoothing high volumes of thermoplastic polymer parts, delivering an injection moulded surface quality. One example is the PostPro3D hardware, which integrates systems, software, and virtual services to efficiently remove the AM produced part from the machine, load it onto a rack, and place it 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.
The technology behind this post-processing method is a physiochemical process that involves converting a proprietary solvent into vapour under precisely controlled vacuum and temperature conditions. This refines the surface of each part to ensure a perfectly smooth finish, equivalent to that of an injection moulded part. The chemicals used are a proprietary mix of organic solvents developed by the University of Sheffield that are non-flammable and non-explosive. The chemicals have been carefully developed to be precursors and metabolites of those already used in the medical industry in FDA approved medical grade medicines, minimising any potential issues with regard to human contact and environmental issues.
The chemicals are inserted into the PostPro3D machine by way of a cartridge, and are used in a completely closed system, which means there is no chance of contact directly with the user. After post processing, the parts are free from chemical residues, and certified and biocompatible for medical device use under ISO 10993. Parts finished in this way have been tested to show they have no cytotoxic effect.
As the PostPro3D is a closed loop system, there is no waste stream for operators to dispose of. The machines require periodic maintenance by qualified technicians, during which recycled consumables and carbon filters are collected and changed. The equipment does not have any waste streams and does not require the use of water.
Additive Manufacturing Technologies
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.