Bending and Warping Defects

A combination of design flaws and operational inconsistencies.

1. Design corrections:
   • Reduce tolerance allowance for tool construction: Allocate more tolerance to accommodate process variations rather than tool manufacturing variations.
   • Refine shrinkage estimates: Avoid using a single shrinkage value for all dimensions; instead, use more accurate values for each dimension.
   • Accurately assess process capabilities: Realistically evaluate the limitations of the casting process to ensure consistent results.
2. Operational corrections:
   • Maintain consistent ejection temperature: Ensure that both the casting and the die are at the same temperature before each ejection.
   • Control hold time using a thermocouple: Replace timers with thermocouples for more precise hold time control.
   • Enforce process consistency: Standardize variables such as die spray, cycle time, and cooling water flow rates to maintain consistent temperatures.
   • Address uneven ejection forces:
     • Evaluate ejector system design and ejector guide mechanism: Check for wear or design flaws that could cause uneven forces.
     • Ensure uniform bumper pin lengths: Replace or adjust bumper pins to maintain consistent lengths.
     • Verify ejector pin placement: Correct any misplacement of ejector pins that could create uneven forces.
     • Eliminate drags: Address drags caused by worn or heat-checked dies, undercuts in the die, or stress on the casting during die opening.
     • Check machine linkage: Inspect machine linkage for wear that could affect ejection forces.
     • Inspect tie bar bushings, platen shoes, and guide pins: Replace or repair worn components to maintain consistent operation.
   • Increase draft allowance: Provide adequate draft, especially for short walls and internal cores, to facilitate easier ejection.
   • Optimize ejection timing: Avoid premature ejection that could lead to distortion.
   • Modify die dimensions if necessary: If all other factors are controlled and the casting shape remains unstable, adjust die dimensions to achieve desired specifications.