Additive manufacturing’s so-called “dirty little secret” was laid bare at an event at The Manufacturing Technology Centre (MTC) in Coventry last month as the results of the two-year FlexiFinish project were unveiled.
Busting the well-worn myth that 3D printing is a case of; send file, click print and voila (surely, we can stop pre-fixing presentations with statements like this by now?), the stats show that current post-processing methods count for a chunky 30% of the manufacturing process and in some cases, that figure can be as high as 60%. It’s a significant hurdle which can often make AM a non-competitive technology. To tackle the problem, a consortium of partners across robotics, inspection, and engineering, with funding from Innovate UK, have developed a solution which aims to reduce post-processing costs and time and increase repeatability.
Led by CAD/CAM and CNC machining leader TTL, FlexiFinish is designed to deliver an automated solution for post-processing metal 3D printed parts, particularly beneficial as AM moves into series production. The project combines multiple post-processing methods, in-process measurement and robotic delivery in a single system. Parts can be finished using a range of abrasive linishing tools or laser polishing in one flexible cell, whilst shot peening is also being tested in a separate setup.
How does it work?
An “as-built” metal component (from electron beam melting EBM) is fixed to the cell where it is picked up by a robotic arm and a scanner measures its surface. Post-processing options including force-feedback driven linishing with a range of tool change operations or laser polishing, provided by surface engineering solutions company, Sandwell UK, are selected and performed before the finished component is either sent back to the scanner to be checked or is removed from the fixture.
The solution also benefits from the FlexiFinish post-processing database, described as a go-to finishing information catalogue, which gives users the ability to process a wide range of materials, geometries and initial surface roughness in order to deliver the optimal finishing process and repeatability.
Putting FlexiFinish to the test
The solution has been designed to initially target the aerospace and medical sectors, two industries which require the utmost reliability and repeatability. During the event, Sarah Heaven, Lead Engineer at GE Power, one of the project partners, explained that though the baseline for AM has reduced over the years, the costs and timelines for post-processing have remained pretty much the same. As the final step of the value stream, if AM is to reach the scale the industry hopes it will, part finishing at volume will need to catch up and become a “lights out” process so that parts can be processed more efficiently.
Scott Lathrope from Meggitt, an engineering group which specialises in extreme environment components for aerospace, defence and energy markets and also an end-user in the project, raised the somewhat overlooked point that there are lots of things you can print but you can’t finish – complexity isn’t as free as it sounds. In order to be truly efficient, some of those post-processing considerations need to be made in the design process such as where to place supports and how you intend to finish internal channels.
British orthopaedic solutions manufacturer, JRI is also providing parts as end-user components to demonstrate the cell’s potential for the medical market.
The were a number of sample aerospace parts on show built with metal AM and finished in the cell. With no particularly complex geometries or lattice structures evident, the parts were not specifically optimised for additive but the consortium believes the same approach would apply to a more complex component. Still, the results were promising, showing a polished mirrored surface finish with clear markings engraved. The combination of in-line inspection techniques meant sample parts achieved reductions in surface roughness up to 99.7% and abrasive finishing speeds at speeds of 40mm2 per second (20mm2 for laser polishing). The consortium believes processing times can be further improved with targeted finishing which focusses only on surfaces that require treatment.
Automation and robotics
One of the most interesting viewpoints of the day came from Mike Wilson at ABB, who was flying the flag for robotics in the UK manufacturing industry. As the ‘smart factory’ becomes a reality for industry, the fear of “robots taking our jobs” heightens but Wilson believes we shouldn’t be so hasty to dismiss our artificially intelligent co-workers.
A recent report showed that in the last five years, the cost of labour has doubled while the cost of robotics has halved but that doesn’t mean robotics should be seen as a cheap alternative to human labour. In fact, Wilson says we need to be embracing automation to enable people to be more productive, getting robots to do the “boring and dirty jobs” we shouldn’t be employing people to do today. This, on the same day I heard a caller on a lunch time radio show audibly upset about self service points potentially replacing cashiers in the supermarket and “Amazon drones” flying over their house, was a welcome dose of reality.
For AM to be competitive, post-processing also needs to embrace that automation element and Wilson gave examples of how Rolls Royce are using standard finishing systems but equipping them with robotics to make them more efficient. In FlexiFinish, ABB is supplying the integral robotics which enable the cell to function as an automated entity.
It is estimated that by 2021, as the AM market (and therefore, part complexity) increases, up to 50% of the final cost of an AM part could be from manual finishing alone.
Katy Milne, Chief Engineer at the MTC, spoke about the current and future propositions for post-processing technologies. Most of the process chain happens after the build and it is not limited to just one step. Additionally, most post-processing techniques for metal AM are highly manual – the image of a hammer and chisel doesn’t exactly shout “future factory”. There are, of course, already widely used methods on the market such as mass finishing using a tumbler or blasting but none of those are suitable for the types of fully enclosed cavities and complex structures that make AM attractive.
However, the post processing market is growing. More machines are being launched to eliminate contact with powder and bring some form of automation to the process – the number of companies focussed on post-processing at this year’s TCT Show exemplifies that finishing is slowly shedding its image as the overlooked part of the AM value chain. Researchers are even exploring techniques such as dissolvable metal supports and simulation systems that cover the entire AM chain including post-build material and quality processes.
The MTC says it’s role is to “bridge the valley of death between academia and industry” and to manufacture on an industrially relevant scale, according to Chief Engineer, Ross Trepleton. FlexiFinish is a good example of this as a project that brings together all of the relevant pieces of industry and research and turns them into a comprehensive solution for a very real industry problem. Paired with the MTC’s current focus on the aerospace sector in its recently announced DRAMA project, the potential to exploit the benefits of AM for high value industries such as this, is becoming an increasingly clear.