Derek Vanek discusses why selective plating warrants a wider appreciation in the aerospace industry and potential applications that could vastly increase cost efficiencies and improve durability and safety of components
Aerospace is an industry which places high demands on the quality, performance, accuracy and traceability of surface coatings.
Surfaces must be finished to a high standard to ensure the components meet their design and performance requirements to withstand the demands of rigorous and regular in-flight service.
Components must endure friction, extreme temperatures and corrosive environments; and any specification driven manufacturing process must pass stringent health and safety requirements.
The two most common aerospace coating applications are for corrosion protection on landing gear and for improved brazeability of turbine engine components.
For corrosion protection, electroplated coatings such as zinc-nickel or cadmium are commonly applied on structural components, while nickel is applied as a pre-braze material to increase the wettability on components such as turbine segments.
While both coatings can be applied using the traditional tank plating method, they can also be applied using a specialised process called selective plating.
Selective plating is a well-established and reliable process which has already been written into multiple aerospace specifications. It not only exceeds the fundamental requirements of aerospace manufacturing, repair and maintenance process, it also provides a full circle of benefits, including quality, durability, cost saving, portability and time saving.
Unlike traditional tank plating, which involves the use of large tanks of preparatory and plating solutions and often requires extensive masking, selective plating uses small volumes of solutions to apply coatings onto localised area of components with minimal masking and waste.
Combining selectiveness with repeatability
While selective plating is safe, effective and provides proven results; it is operator intensive. The operator, even with proper protective equipment is close to the work area and handles the chemical and tooling, and the plating technique can vary from operator to operator. Fortunately, the SIFCO Process of selective plating can be mechanised or fully-automated.
Mechanising the process minimises the direct contact the operator has with the tooling and chemicals by using a computer program to control the rectifier voltage and time for pre-treatment and plating steps, allowing the operator to be in control the process. While, fully-automating the process removes the operator -and the variability- from the entire operation.
In the surface finishing industry, it is the innovation of SIFCO ASC that is leading the way into the automation of selective plating.
In April 2016, SIFCO ASC unveiled its new automated plating system at the MACH exhibition to showcase the benefits to industry.
SIFCO ASC designs customised, fully-automated systems that require minimal need for operator intervention. Various pumps, flow systems, and cleaning agents, work together to change, catch, and circulate solution; while a robotic arm holds, oscillates, and changes the anodes needed throughout an entire plating operation.
By automating the selective plating process using a programmable logic controller, operators can review data captured through the human-machine interface to determine if the operation was completed correctly.
If any errors do occur, or quality standards are not met, operators can review the data and trace the error to its source and assign the appropriate corrective action, preventing the errors from being repeated – effectively improving traceability and repeatability within the process.
Additionally, automation reduces the ergonomic risk to the operator, and also increases the available capacity by allowing skilled operators to focus on the core business processes.
These benefits can clearly be seen in the aerospace industry with SIFCO ASC’s recent, and highly regarded, work with leading manufacturers of aircraft engine and landing gear components in the UK and USA.
In the UK, for the leading manufacturer of landing gear systems, while demanding aerospace operating conditions present continual surface finishing challenges; one particular challenge came in the form of a landing gear bogie beam design.
Landing gear designs include a stop-pad between the bogie beam and vertical part of the component to prevent wear as it is retracted into the fuselage.
However, this impact results in potential wear at the interface with a further risk of atmospheric corrosion. A design modification was agreed involving the application of a nickel chrome electrolytic protective treatment.
SIFCO ASC’s UK team consulted its French specialist engineering R&D department. Following a full situation analysis, the team recommended the SIFCO Process should be automated using a collaborative robot.
The robot, now fully operational at the company’s Gloucester facility, provides the company with a precise and highly traceable, repeatable and accurate process, well-suited to the hi-tech facility it sits within.
The integrated computer logs all of the relevant information including: the parameters plated; the batch numbers for the solution; current densities and solution levels.
The fully-automated system also adheres to the company’s health and safety policy as it minimises human contact with harmful chemicals. It currently processes 30 bogie beams per month and the team is looking to expand its use into other areas of the company.
In the USA, a leader in aircraft engine manufacturing also called upon SIFCO ASC to assist in their prebraze application.
Because of the irregular shaped face of its turbine castings, the manual plating process method was still being used - increasing ergonomic strain on each technician.
Following the preparatory plating steps, a layer of AeroNikl 250 was plated on each turbine casting for improved wettability. With each component taking 7.5 minutes to plate, a technician could expect to spend 6 working hours a day at the plating station.
So SIFCO ASC developed a turnkey robotic plating system to perform the functions of the technician. A robotic arm holds the turbine casting, carefully bringing it to the solution and anode, oscillating at the optimum anode-to-cathode speed, rinsing and then continuing the SIFCO Process until the part is complete.
So, while selective plating may not have been perceived as an automated or robotic technology, innovation and collaborative thinking allows SIFCO ASC to work with leading aerospace manufacturers to develop start-of-the-art solutions.
With their renowned repeatability, improved process control and accuracy, robots can be the tools of choice for many aerospace manufacturing operations.
Essentially, they are helping to shape the aerospace factories of the future. Now the established benefits of selective plating will play a fundamental role in achieving the high levels of quality, performance, accuracy and traceability that the aerospace manufacturing process demands.
Derek Vanek is Technical Manager at SIFCO Applied Surface Concepts (ASC).