Blow Moulded Bottle Weight Trimmed until the Drop Test Fails
Trimming blow moulded bottle weight reduces unit resin costs but narrows drop test safety margins along bottom pinch seams and heel radii.
Heel Transition Radius
Meaning
Geometric curvature connecting the vertical container sidewall to the bottom standing chime defines a critical structural junction on blow moulded articles. Engineering of the heel transition radius dictates localized stress concentrations, material thinning dynamics and container stability during conveying and drop impacts. The feature is an essential design element of extrusion blow moulded, injection blow moulded and stretch blow moulded plastic containers, stopping where flat bottom plates or completely spherical pressure vessels eliminate corner transitions.
Stress Concentration
Sharp corner transitions generate severe localized notch sensitivity that amplifies mechanical shock during handling. When a filled bottle drops onto a rigid floor, dynamic hydraulic fluid pressure surges downward and outward, concentrating flexural hoop stresses along the heel transition radius. A generous radius distributes impact energy across a wider surface area, enabling plastic deformation without catastrophic crack propagation.
Process engineers ensure that mold cavity design avoids acute transitions, maintaining smooth curvature that facilitates uniform resin flow during the blowing phase.
Material Distribution
Parison expansion reaches its highest blow-up ratio at the extreme lower corners of the mould cavity. During inflation, molten plastic contacts the central container base and sidewalls first, rapidly chilling and leaving minimal compliant melt to stretch into the remaining heel void. If the heel transition radius is designed too tight, localized wall thinning occurs, creating a fragile zone susceptible to environmental stress cracking.
Proper parison programming deposits additional resin mass at the lower parison segment to ensure adequate heel wall thickness without extending overall cooling time.
Mould Tooling
Tooling manufacturers machine bottom corner transitions with high-precision computer numeric control milling and polishing routines. Rough surface finishes or improper transition blending in the heel cavity promote micro-cracks and impede smooth parison stretching. Sourcing teams review bottle engineering drawings to ensure specified corner radii balance aesthetic shelf appeal with structural impact requirements.
Quality audits measure corner wall thickness using magnetic target gauges to confirm that production containers meet minimum specified thickness targets. Generous corner geometry prevents production jamming on automated high-speed conveyor lines.