Vickers Systems Division
Process with no special dies required
Easily machined materials to be identified
Corrosion resistant a requirement
Good wear properties also required
Brass was most cost-effective material
Courtesy of Vickers Systems Division, Trinova Ltd
Notes:
Vickers Systems Division have 50 years experience in the design and manufacture of the Lang range of pneumatic products, which include cylinders, directional control valves and ancillary products. The company pride themselves on developing and manufacturing innovative and creative products at competitive prices.
To achieve this material selection is critical, selecting a material not only for its properties, but its cost effectiveness. One example of this is the 4-Way Semi-Rotary Slide Valve which is required to have a long life (20 plus years) when fitted to heavy duty products e.g. Railway Wagons, Brewery Handling Equipment and Keg Cleaning Systems, Military Vehicles, Quarrying and Mining Equipment, which operate in harsh and rugged environments. In these instances the valve needs to be manufactured from a corrosion resistant, low friction, self lubricating and easily machined material. The natural choice of material would be a free machining brass in extruded bar form, however the raw material price of brass would appear to rule it out. A possible alternative choice of material might be extruded aluminium, the raw material cost being half that of brass. (see cost analysis).
To have the same wear properties as brass in this application aluminium needs to be hard anodised after machining. This accounts for over a quarter of the cost of manufacture, whereas brass requires no finish.
Additionally brass machines faster than aluminium and the value of the scrap produced during the machining operations has a higher value, therefore resulting in further cost savings in favour of brass.