A methodology for near net shape process feasibility assessment

Figures & data

Figure 1. A generic methodology for assessing the feasibility of adopting an NNS process.

Figure 2. Basic control valve showing the cage used for the case study.

Figure 3. Schematic of the existing manufacturing process chain (top) and the proposed NNS manufacturing process chain (bottom).

Figure 4. True centrifugal casting and semi-centrifugal casting (Swift & Booker, 2013).

Figure 5. Schematic of the two process chains and the associated differential cost analysis (i.e. cost models comparison).

Figure 6. Centrifugal casting blank (left), semi-finished valve cage (right).

Figure 7. Schematic of the centrifugal casting cost model.

Figure 8. Cost comparison of the NNS process chain (a) and existing chain (b). Cost details for different cages sizes: 100 mm (c), 250 mm (d) and 400 (e). Component cost comparison of component evaluated costs for the NNS process chain (i.e. centrifugal casting and finish machining) and the existing process chain (i.e. machining from solid blank) (f).

Figure 9. Step diagram for selecting the outer diameter of centrifugal casting’s mould given the outer diameter of the final component.

Table

Cost Models Nomenclature	, inner diameter of the centrifugal casting part (blank) (mm)
CTM, total cost of machining from a solid blank (£)	, thickness of the centrifugal casting part (blank) (mm)
CTCC, total cost of machining from a centrifugal casting blank (£)
CSB, cost of solid blank (£)	Centrifugal Casting Model Nomenclature
CCCB, cost of centrifugal casting blank (£)
CM, machining total cost (£)	, outer diameter of the centrifugal casting mould (mm)
CI, indirect costs (£)	, inner diameter of the component after centrifugal casting (mm)
CTu, turning costs (£)	, length of the centrifugal casting mould (standard case) (mm)
TTu, turning total time (£)	, length of the centrifugal casting mould (special case) (mm)
Vf, final volume of the part (mm^3)	, minimum internal diameter (standard case) (mm)
VSB, volume of the solid blank (mm^3)	, minimum internal diameter (special case) (mm)
VCCB, volume of the centrifugal casting blank (mm^3)	, total cost of a centrifugal casting component
MRRT, material removal rate (mm^3/min)	, melting cost
cM, machining cost	, auxiliary cost (excluding mould cost) (£)
TOP, turning machine working time (min)	, energy cost (£)
TId, turning idle time (set-up, tool change …) (min)	, centrifugal casting operation cost (including labour and direct costs) (£)
CSB, cost of the solid blank (£)	, proof machining cost (£)
VSB, volume of the solid blank (mm^3)	, mass of the molten material (kg)
, material density (kg/mm^3)	, mass of the centrifugal casting part after proof machining (kg)
cMAT, material cost (£/kg)	, material melting cost coefficient (£/kg)
ODSB, external diameter of the solid blank (mm)	, machining chips re-melting cost coefficient (£/kg)
LSB, length of the solid blank (mm)	, auxiliary cost coefficient (£/kg)
tSB, thickness of the solid blank (mm)	, energy cost coefficient (£/kg)
ODF, maximum outer diameter of the final semi-finished component (mm)	, centrifugal casting operation cost coefficient (£/kg)
, minimum outer diameter of the final semi-finished component (mm)	, proof machining cost coefficient (£/kg)
, inner diameter of the final semi-finished component (mm)	, material density before the centrifugal casting operation (kg/mm^3)
, total length of the final semi-finished component (mm)
, length of the final semi-finished component in contact with fluid (mm)

Swift, K. G., & Booker, J. D. (2013). Manufacturing process selection handbook. Oxford: Butterworth-Heinemann. doi:10.1016/B978-0-08-099360-7.00005-7

 Google Scholar