@misc{9231616,
  abstract     = {{Material variability in grey cast iron is usually discussed in terms of metallurgy or machinability, while its consequences for production-flow behaviour and per-part economics are less systematically characterised. This thesis investigates how compositional variability in grey cast iron propagates through machining response into production-system behaviour, and quantifies the resulting per-part economic consequences as a basis for supply-chain decision-making.
A reduced-order modelling framework with four layers is developed. The first layer translates representative compositional scenarios (baseline S0, CE/matrix drift S1, local heterogeneity S2, residual hardening S3 and combined adverse S4) into material-response descriptors. The second layer translates these descriptors into operation-specific machining multipliers for processing time, tool-life consumption and incident intensity. The third layer propagates these multipliers through a SimPy-based discrete-event production-flow model representing a serial machining line of OP10 face milling, OP20 drilling and OP30 heavy turning, connected by finite buffers. The fourth layer aggregates the production-flow outputs into a per-part unit-cost indicator through a transparent cost layer covering machine-hour cost, tool-change cost, raw-material cost and probabilistic scrap cost.
Three simulation configurations are studied. Case A characterises the production-flow response under nominal cutting parameters. Case B introduces the OP30 cutting speed as a decision variable through a normalised speed ratio coupled to tool life via Taylor's equation, and identifies the production-optimal cutting speed for each scenario. Case C extends the cutting-speed sweep with the cost layer and identifies the cost-optimal cutting speed and the unavoidable cost penalty for each scenario, defined as the per-part cost increase that persists after per-scenario re-optimization of the cutting speed.
The principal finding is that material variability produces a scenario-dependent unavoidable unit-cost penalty whose magnitude differs substantially across mechanisms. At a baseline unit cost of €80.76 per part, residual hardening produces an unavoidable penalty of +10.46% (€8.45 per part), combined adverse conditions +11.98% (€9.68 per part), CE/matrix drift +5.27% (€4.26 per part) and local heterogeneity +1.28% (€1.03 per part). The approximately eight-fold ratio between the most and least severe single mechanisms is robust to wide variation in cost-parameter assumptions, as confirmed by a 27-combination sensitivity sweep that places the residual-hardening penalty consistently in the range +9.05% to +12.42%. The unit-cost decomposition further shows that machine-hour cost and raw-material cost together account for more than 90% of unit cost, indicating that material variability reaches the cost objective primarily through machine-time amplification at the bottleneck operation rather than through direct tool consumption or quality loss. These per-part values establish quantitative ceilings for the economic justification of incoming-material quality improvements targeting each material mechanism, and provide a structured supply-chain decision framework that links material mechanisms to recommended process-side and supply-chain responses.}},
  author       = {{Qian, Chenghan}},
  language     = {{eng}},
  note         = {{Student Paper}},
  title        = {{From Composition to Cost_Modelling Material Variability in Grey Cast Iron Machining}},
  year         = {{2026}},
}