Finecast has produced an extraordinary stabilised antenna platform as a lightweight cast component – converting the part from a fabrication has reduced weight and increased strength.

Component

  • Lightweight stabilised antenna platform main frame, 80kg (casting), 63kg (finish machined) for use in the naval surveillance market
  • Dimensions 1415mm (length) x 1055mm (width) x 965mm (height)
  • Nominal wall thickness of 5mm

Alloy: Aluminium BSL169 (A357 T6)
Casting Process: Gravity poured precision sand casting
Previous Part: Fabrication

Customer Requirements

  • The creation of a smaller, lighter, stiffer and stronger radar self – stabilising main frame Improve quality
  • Reduce lead time to market to meet quality ISIR requirements
  • Reduce costs
  • Reduce weight of component

Outcome

  • From the original concept meeting, delivery of the tooling and first main frame cast was achieved in four months. Thus lead time was greatly reduce compared the fabrication methods.
  • The initial main frame and other castings were right first time, and successfully completed the first assembly and static simulation tests without problems.
  • The total project assembly weight targets were as designed, and lighter than fabrications for carrying the same antenna payload. Only minor machining adjustments have been made to the project.
  • The casting option has proven to maintain dimensional repeatability.
  • The lighter weight frame has achieved increased stiffness and strength, compared to heavier fabrications.
  • The achievement of thin wall casting dimensions, that are not traditionally considered able to be cast in sand, can now be produced in a precision sand foundry process.

Challenges

  • Low wall thickness for the size of the casting, with no draft allowances
  • The calculated modulus was 2.9mm, on a par with casting a 5mm plate (2160 x 2160mm with holes)
  • Fill distances, T section rules, solidification times, non turbulent flow and mould space were significant factors
  • Because of the physical size of the tooling, cope and drag 2.2 x 2.2m moulds, restrictions of taper, a total of 33, multi loose piece core boxes had to be manufactured in a short lead time.
  • Being a multi core assembly, it is essential that the foundation (drag) is maintained as flat as possible.
  • The main frame and roll frame required in line boring together.

Method

To complete delivery in time, the project utilised two patternshops working from one CAD reference model. Additional hand ladle capacity was added to complete the required quantity of 450kg of metal. For reduction of quench distortion after solution, the casting was heat treated with the running system still attached minus risers. The final finished casting was anodised/anocromed, painted and delivered to the customer for assembly.