MATERIALS IN DESIGN & PROTOTYPING FEATURE


Components specified for use within the food and beverage industry need to offer


A GUIDE TO... material selection


W


hether during manufacture, storage or preparation, hygiene is essential for


standard parts and machine accessories. The material composition of these parts – ranging from conveyor components to castors and wheels, and even door handles – therefore needs to be resistant to bacteria and easy to clean. Resistance to corrosion is also vital, especially


where high acidity or salinity is common, in order to ensure a long component life while maintaining its resistance to pitting and blemishes, which will make it more difficult to clean. Anti-corrosion properties are also key for the cleaning process. Being robust, resistant to corrosion and with


an attractive appearance which is a clear marker of visible hygiene, stainless steel is often used. Capable of withstanding a thorough washdown, an applied finish can also remove surface imperfections, such as microscopic blemishes, which could otherwise retain bacteria.


MATERIAL CHOICES Stainless steel Type 304 is the most common type. This has a higher level of carbon (04% to 0.10%) so can withstand temperatures up to around 870˚C, exceeding the tolerance required for food production. Containing up to 10.5% nickel and up to 20% chromium, this is widely


resistant to corrosion and free from rust. While it can be used in direct contact with food substances, it’s preferable to use it for applications with less frequent contact to corrosive substances including saline and chloride. Frequently used for door handles, fittings and hinges, it is most suited to areas which require only a mild washdown. Type 303 stainless steel has properties similar


to Type 304 although it has a marginally lower durability. Its improved machinability, however, is a benefit when very low tolerances are involved, such as machining a thread. The durability and corrosion protection


provided by Type 316 means it is suited to applications which have direct contact to food and beverages, including machinery. Adding molybdenum makes it highly resistant to corrosion – especially to pitting – and it can withstand intensive and frequent washdown. As a result, this is a ‘food grade’ material, with


OEMs specifying it throughout the food and beverage industry for such products as gas struts, such as those used on serving hatches of mobile kitchens, or for ventilation grills. Applications can often be located outside, open to the elements, or in hostile environments such as a cooking area where hot oil or corrosive ingredients are present.


3D PRINTER ENABLES ULTRA-REALISTIC PROTOTYPING


The concept behind Italdesign’s 2019 concept car, the Italdesign DaVinci, was to revive the best of Italian elegance. So, the team wanted to produce a number of key internal parts in marble – the central console, air conditioning diffusers and door inlays – but realised that producing such parts in time for the Geneva Motor Show using the traditional stonemasonry process was not possible. Having tested several possibilities, the team turned to its Stratasys J750 full colour, multi-material


3D printer, which has the capability to 3D print marble effects and textures directly onto parts. To achieve this, the team designed each part via CAD and using a render software, the marble texture was then overlaid onto the part to deliver the desired aesthetic style ‘digitally’. Once the design was validated, the final file was uploaded to GrabCAD Print, enabling the team to best position each part ready for printing. Using the J750, high quality marble-effect parts were rapidly printed. Daniel Agulló, general manager, Italdesign Giugiaro Barcelona, said: “Instead of several weeks of


work, in just over a weekend we were able to produce four air conditioning diffusers, two door inlays and the central console. Everyone was taken aback by the results, both in terms of the resolution accuracy and material quality – so much so that no design iterations were required.” He added: “The J750 has opened our eyes to the


possibilities of ultra-realistic prototyping. The marble case is the perfect example – before we could not have imagined producing parts that look and feel like marble so quickly. With this technology, there is no reason why we can’t continue to push the boundaries of textured design by 3D printing and fitting parts featuring fake animal skins, wood or many other effects. The possibilities are endless.”


Stratasys / DESIGNSOLUTIONS www.stratasys.com hygiene and anti-corrosion


properties. But with materials ranging from steels to


plastics, which should you choose? John Marshall, technical manager at WDS Components Parts, comments


For peripheral, non-food contact items such as


handles, aluminium can also be used. Anodising gives some protection and is ideal if various colour finishes are required, but it can attract an oxide coating which can flake off over time. Plastics are commonly used for castor wheels,


where the softer structure reduces noise and increases grip. Phenolic plastic offers a hygiene level comparable to stainless steel and can be used in temperatures from -40˚C to 280˚C. Plastic can also be used for base pads of stainless steel levelling feet. Anti-microbial additives can be added to polypropylene, which can be offered in a wide variety of colours.


MEETING FOOD & BEVERAGE DEMANDS When procuring standard parts, it’s important to ensure manufacturing quality. The manufacturer should therefore meet the BS EN ISO 9001:2015 standard, which helps ensure quality management and demonstrates a robust planning and testing process. Its relationship with the food and beverage


industry means WDS is able to implement designs to meet specific requirements – such as hinges with rounded edges to decrease build-up of bacteria. The company also understands the need to ensure a precise finish to optimise resistance to corrosion, improving hygiene. As with many industries, components are often


needed quickly, so WDS (which has a catalogue of over 20,000 parts) has a stock holding which enables next day delivery in the UK.


WDS Component Parts www.wdscomponents.com/en-gb


DESIGN SOLUTIONS | MARCH 2020 25


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