PROCESS EQUIPMENT UPDATE
fabricated from their machines raises questions about quality assurance, reproducibility of properties in 3D printed parts, reliability of the 3D printing process and of course on the existence of measurable parameters for bench-marking 3D printed part integrity. In the past five years there has been an interest
within the field of additive manufacturing to explore the processability of materials used in safety-critical applications. Fibre-reinforced polymeric materials, composites materials containing nano-materials such as carbon nanotubes, advanced materials such as shape memory alloys and materials used in human implant applications such as titanium-6-Al-4-V (Ti6Al4V) and PEEK are key amongst such materials. For a relatively
Fig.3. 3D printed PEEK parts: (a) seal/gasket, (b) flange, (c) drive gear system, (d) heat exchanger
new manufacturing technology such as 3D printing, the threshold for acceptance is understandably set high because there is suspicion, caution and a general sense of uncertainty towards new habits, methods or processes in a rather conservative industry such as the manufacturing sector. That said, experimentally generated data that allows for the interpretation of the performance of 3D printed part needs to be published. In vacuum technology, where chemical inertness,
high strength and outgassing are critical issues, PEEK has found application in the areas of: sealing, gaskets, material for low load bearing structural components and as substrate for active agents. In one study, when baked for 12 hours at 150°C prior to testing in vacuum condition, a 3D printed PEEK part exhibited outgassing rate of 4.1x10-11
mbar l/cm-2 s-1 ; a value falling well
within the ultrahigh to extremely high vacuum range. A residual gas analyser (RGA) scan on PEEK samples to determine the kind of molecules being outgassed revealed the main gas species observed were hydrogen water and carbon dioxide; most likely from the hot filament in the RGA. There is a place for 3D printing/additive
a b
manufacturing within the chemical process industry; we need to work at identifying this niche. In the medical sector 3D printing tools are already being used for patient-specific implant production, applying data from MRI or CT scans of the patient as input to the 3D printer. Can computer-aided models of process plants be re-sized and 3D printed? Can we enhance our digital workflows with design features and attributes that will make it possible to 3D print models of plants and test run the plants? Can 3D printers be used for spare-part fabrication to keep our ageing plants running or for fabricating newly developed component designs fitted to improve on plant performance? The authors believe there is a practicable opportunity to do new things in plant design, operation and optimisation using 3D printing technologies. n
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Fig.4. Impeller system 3D printed from PEEK, housing is 3D printed from polyamide (PA6)
c
d
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