Engineering teams at Nottingham-based Advanex Europe have been working in collaboration with some of the world’s leading medical device manufacturers to develop techniques for reducing ‘particulate’ – the minute, separate particles of organic and non-organic matter that can contaminate components.
With management systems approved to ISO 9001 and 140001, Advanex Europe produces metal and plastic components for various medical devices. These currently include coil springs, anti-tangling coil springs, metal pressings and wire shapes, which are used in a variety of medical devices such as metered dose inhalers, auto injection systems and nasal sprays.
The company is actively growing its customer base in the medical device market and is committed to being at the forefront of reducing particulate. Such particles can be generated during the coiling and forming process by friction between the raw material and the tooling, and from foreign bodies, such as lubricants, that are picked up by contact during manufacturing. Components can also be contaminated by airborne particulate present in the atmosphere surrounding the process and contact with operators, equipment, packaging materials etc., during manufacturing.
Traditional spring coilers form springs by continuously pushing wire against an inclined tool that forces the wire to bend and form a coil. This generates high levels of friction, requires lubrication (usually in the form of soap-coated wire) and greatly restricts the rate at which the coil can be formed. Usually, this coiling soap, which is a potential contaminant, is removed by secondary processes.
Prevention by design
In some circumstances particulate can be reduced by prevention. For some applications, Advanex Europe has designed bespoke processes and tooling to reduce frictional effects as far as possible that do not require soap-coated wire.
Designing and building bespoke manufacturing equipment can provide an advantage for customers as the process can be optimised for the product. Most spring manufacturers use ‘off-the shelf’ machinery that is very versatile and can make a huge variety of products. In many cases, Advanex can form coil springs by wrapping the wire around a rotating mandrel which generates much lower levels of friction, does not require soap-coated wire and can produce springs at much higher production rates.
Mandrel coiling is not as versatile as traditional coiling methods and bespoke-sized tooling will be required for each product, but if the required quantities are high enough this method can be very economical.
The versatility associated with traditional coilers requires a relatively large amount of equipment and tooling, some of which is redundant for manufacture of any individual product. All the machine components provide opportunities for generation of particulate. Advanex designs manufacturing equipment to fit the product so that all components used in the machine construction are critical to the manufacturing process, and there is no redundant equipment.
The design of each machine component and its potential for generating particulate is carefully considered. Sharp edges and situations where high levels of friction can occur are generally avoided. Using materials that reduce friction and have high wear resistance, such as carbide, polished stainless steel, hard eloxated/hard anodised aluminium and other FDA-approved materials, can be employed. Locations where particulate could collect such as internal corners are avoided wherever possible.
Vibratory deburring: This is the process of removing small pieces of material from components to smooth surfaces and edges. During manufacturing processes, operations such as cutting can leave raised edges or burrs that can become detached from the parent component. These can be removed using centrifugal, vibratory bowls and high density ceramic or synthetic media.
Laser deburring: Cutting round section wire can often leave burrs where the wire has been cut. For some components, Advanex Europe offers laser deburring which, by firing a high powered laser beam directly onto the end of the wire, provides a dome-shaped end.
Sieving: The company can also offer inline and offline sieving. Sieving is a vibratory process that removes particulate by gentle abrasion while supported on a mesh or gauze. The particulate is separated from the components by dropping through the mesh. The size of the mesh is critical to the success of the sieving operation.
Solvent and aqueous cleaning: These dedicated washing processes are suitable for most metallic materials. Both require the component to be immersed in a heated liquid media, either solvent- or water-based, for a period of time. The components are usually tumbled within the media or the media agitated during the process. Particulate is washed from the components and removed by filtration of the media. Aqueous cleaning is generally more environmentally friendly than solvent-based cleaning processes.
Ultrasonic cleaning: This is carried out in conjunction with either solvent- or aqueous-based cleaning processes. It involves using an ultrasound generating transducer immersed within the media that creates bubbles using high frequency (20–400kHz) sound waves to agitate the media. This ‘cavitation’ process removes contaminants that are adhered to, or embedded into the surfaces of materials such as metals, plastics and ceramics.
Pickling: Usually performed in citric or hydrochloric acid solution, this technique removes a thin, surface layer of the material taking the embedded particulate and other contaminants with it. It is often performed as a pre-treatment prior to passivation of stainless steels.
Clean areas
Some spring-making processes, such as traditional coiling methods that require soap-coated wire, generate large amounts of particulate. Other methods, such as mandrel coiling with bright wire, are inherently cleaner but still generate particulate to a lesser degree.
The amount of residual particulate that is acceptable to the customer will depend upon the application of the product. Advanex Europe has several clean manufacturing areas dedicated to the customer’s product and isolated from other processes. These are designed to match the process and the product specification, with the aim of reducing foreign matter introduced by operators and the surrounding environment contaminating the product.
Depending on the process and customer requirements, some clean areas will only require the operators to wear protective clothing, while others have interlocking doors and maintain a positive air pressure etc. Manufacturing within these areas can keep particulate at levels where the cleaning burden on the component can be dramatically reduced without the high costs and limitations imposed by cleanroom manufacture.
Pharmaceutical manufacturing area at the Advanex Southwell plant
Where springs are ultimately to be assembled into devices within cleanrooms, customers will need the component parts to be free from biological contamination, as well as particulate. Advanex Europe has installed two Class 10,000 (ISO 7) cleanrooms – up to 10,000 particles per cubic foot of air – so that parts can be cleaned in-house.
The latest facility allows product to be passed into the cleanroom via an airlock ‘pass-through’ directly from the clean manufacturing area. Once inside the cleanroom, the parts are ultrasonically cleaned to remove any contamination, double-bagged within the cleanroom, and passed out through a further airlock to await despatch. The parts can then go into the customer’s cleanroom, with the outer bag removed, so that no contamination is taken in via the outer packaging.
Control of the efficacy of the cleanroom can be achieved by performing regular bioburden tests on cleaned parts. This will give assurance that the parts meet the prescribed microbial limit for the number of bacteria present.
As new methods to reduce particulate evolve, the company remains committed to taking these on board and delivering first class solutions to device producers.
