1. Flash (Burrs)
Description
Thin metal protrusions form on casting edges due to molten metal leaking into gaps:
    Mold parting lines
    Slide fits
    Core clearances
    Ejector pin holes

Root Causes
    Poor machining precision (mold/slides/ejector holes)
    Thermal deformation of mold
    Improper process parameters:
        Melt/mold temperature
        Injection speed
        Casting pressure
        Projected area

Solutions
✔ Improve mold machining accuracy (≤0.05mm clearance)
✔ Increase mold hardness (HRC 48-52 for Al alloys)
✔ Optimize clamping force (calculate based on projected area)
✔ Adjust casting parameters (validate via DOE)
2. Heat Checking (Network Cracks)
Description

Fine crack patterns on mold surfaces transfer to castings as visible blemishes.
Root Causes
    Thermal stress from heating/cooling cycles
    Improper:
        Casting conditions
        Mold material/heat treatment
        Cooling design (external vs. internal)

Solutions
✔ Reduce thermal shock (ΔT between melt & mold <150°C)
✔ Preheat molds to 180°C (Al) / 120°C (Zn)
✔ Prioritize internal cooling channels over external sprays
✔ Use premium hot-work steel (H13 with 44-48 HRC)
✔ Polish cavities to Ra ≤0.2μm
3. Surface Exudation ("Sweat")
Description

Metal beads form on edges/corners due to inverse segregation (enriched solute content).
Root Causes
    Local overheating in sharp features
    Slow solidification of surface layers
    High intensification pressure

Solutions
✔ Add corner-specific cooling (point chillers)
✔ Lower melt temperature (Al: 660-680°C)
✔ Optimize intensification pressure/time
✔ Select alloys with narrow solidification range (e.g., A380 vs. A360)
4. Blisters
Description
Surface bulges caused by trapped gas expanding during ejection or heat treatment (T6).
Root Causes
    Entrapped air/gas near surfaces
    Weak alloy strength during heat treatment
Solutions
✔ Apply porosity countermeasures (vacuum assist, overflow design)
✔ Optimize venting/gating systems
✔ Control lubricant amount (≤2mg/cm² per shot)
✔ Adjust mold opening time (>15s for Al)
✔ Implement conformal cooling