Machined Enclosure Materials & Applications
Factors to consider that affect the choice of enclosure material are:
- Indoor or exterior environment
- Mechanical loading
- Risk of collision
- Gas, chemical or dust contaminants
- Marine and salt water exposure
- WEEE Directive and regulations on waste management and recycling
Used where cleanliness and corrosion resistance is important due to cleaning regimes or harsh environmental factors. 304 (1.4301 and 1.4307) stainless is often specified for indoor clean room environments. Enclosures can tarnish and pit in environments open to the elements, salt water and where aggressive cleaning is performed. In such situations 316 stainless is a better choice. It takes 2 to 2.5 times the machining time to process stainless steel compared to aluminium, therefore making stainless steel an expensive and rare choice of material for bespoke machined enclosures for mechanically demanding applications.
Where the enclosure needs to be more robust to cope with bumps and knocks then aluminium is worth considering. Aluminium is a common choice of material for bespoke and custom machined enclosures. Aluminium is often considered to tackle the issue of “noisy electronics and assist with EMC protection. Applications where corrosion resistance is an issue, aluminium should also be considered. Where applications have high mechanical demands stainless steel is naturally the more robust option. However designers do consider and choose to manufacture in aluminium with uprated wall thicknesses to meet the mechanical requirements being dictated.
Where volumes are higher, firstly consider off the shelf standard die cast enclosures which could be modified to suit the requirements of the applications. If volumes are high then investment in specific die cast tooling may be an option to achieve the lowest unit costs.
Plastic is also a common cost effective choice for lightweight applications to enclose instrumentation, electronics, control gear and display screens. Plastic grade selection requires careful consideration to meet the needs of the application. Factors for consideration are:
- UV rating
- EMC protection
- Ambient environment characteristics
- Presence of chemicals
ABS and polycarbonate are the common grades for standard moulded enclosure manufacture.
Again, firstly consider off the shelf moulded options that could be modified by machining. The as moulded outside finish can be aesthetically acceptable and remove costly finishing processes.
We often perform secondary machining operations to “off the shelf” and bespoke plastic moulded enclosures, which due to restrictions in moulding cannot be formed to the finish size geometry and require additional machining to complete. These higher value enclosures typically need processing with great care as the outside finish is complete and aesthetically critical.