High end surface finishing of metal components used in aerospace manufacturing is essential and can be critical to the part's or an assembly's performance.
Depending on the part, this may manifest itself in a contribution to reducing fuel consumption and therefore CO2. It may show in reduced wear through less friction leading to lower maintenance costs, and often it will be a precursor to the application of advanced hard coatings followed by further surface finishing to remove hard droplets.
For over 25 years, AS9100-certified Fintek has been providing subcontract surface finishing expertise to aerospace precision engineers producing parts such as connectors with difficult to finish threads, turbine blades, blisks, and actuation gears.
The company has not only been using machines designed and manufactured by OTEC Präzisionsfinish; it has also been OTEC’s agent for exclusive machine supply in the UK. Subcontracting gives Fintek an insight from solving real world surface finishing problems, while its close working relationship with OTEC gives it access to world class research and development and the newest machine technology.
Following in the footsteps of the company's advanced stream finishing machines, the latest machine from OTEC - the new SF-HP - was launched in Germany at the end of 2020. It is creating something of a stir by pushing the boundaries of the size and weight of workpieces that can be precisely deburred, edge-rounded, smoothed and polished to a mirror-like finish in an automated process.
"The SF-HP includes many innovations,” begins Fintek's managing director, Jonathan Dean. “Significantly larger, workpieces up to 650mm in diameter and 650mm long, and weighing up to 200kg can now be accommodated. There are numerous process head and spindle axis settings, giving the ability to fix a highly-controlled and precise flow through the process media which also enables the accurate targeting of specific workpiece surface points. This means we can now surface finish items such as larger turbine blades where retaining close tolerances of the blade edge profile is vital to the blade's real world performance on wing."
Another significant inclusion in the SF-HP, is OTEC's patented 'Pulsfinish' as standard equipment. Until now, this has been an optional addition to its stream finishing family of machines. The pulse drive technology delivers precisely defined and repeated movement intervals between the process media and workpiece by quickly changing the direction of rotation of the heads. Along with the quick acceleration and deceleration of the heads, these rapid changes in movement increase the finishing forces exerted. Typically, this makes it possible, to deburr, edge-radius and smooth from Rpk 0.3μm to Rpk 0.1μm in a single step in just a few minutes.
The precision of minimal material removal is also enabling stream finishing to be applied to some additively manufactured components. The relatively rough finish following structure removal from AM parts means post finishing is often required to complete a commercially acceptable part. Finishing by hand can be costly and providing internal surfaces are not too complex or fine, these can be quickly transformed by stream finishing in a fraction of the time.
Also integrated into the SF-HP is automation for holding, machining and workpiece change. Where multi-step processes require different media a simple container swap system provides for rapid change-over to keep production speeding along. Operation and programming is via a large and clear 15 inch multi-touch colour display. This makes it easy to store repeatable process steps for quick recall and to ensure consistent accuracy, and it also makes training new users much easier.
“As machines with the capacity for automated surface finishing of larger components have been lacking until the introduction of the SF-HP, hand finishing may still be in use for larger parts with all its time-consuming and quality inconsistencies,” concludes Dean. “Over the last few decades hand processes have been phased out for most smaller components, as the machines don't just save time, they ensure repeatable, high quality surfaces that meet required tolerances more evenly, and with less risk of workpiece damage from powered hand tools.
“And, right now, while we are all conscious of social distancing restrictions due to coronavirus, the SF-HP and other machines can help reduce the need for the number of on-site employees that might be engaged in hand finishing at any one time.”