Stripper Ring plus Air Pop-Eject Protects Light Wall

An injection thin-wall plastic round bowl barrel mould is a dedicated tool that forms light, straight-sided containers suitable for food service, retail display, or small-item storage. The aim is to remove excess mass while keeping the rim strong enough to accept a snap-on lid and the base flat enough to stack ten high without leaning. Designers start by fixing the volume then set the draft angle at barely half a degree so the bowl releases smoothly from the core. A shallow rolling ring is added just below the rim; this stiffens the open edge and gives the fingers a secure grip during lifting.

Wall thickness is targeted near 0.4 millimetres. At this gauge the part cools quickly, yet it can also warp if shrinkage is uneven. To counter the risk, the base is given a gentle crown that springs back flat after ejection, and short radial ribs are placed under the floor. These ribs act like miniature beams, carrying impact load to the outer wall without thickening the plastic. The corner where base meets side is radiused at three millimetres; a tighter bend would create a hot spot in the melt and a weak line in drop tests.

Gate position is chosen early through flow simulation. A single pinpoint gate placed at the bowl centre allows the melt to travel outward in a balanced disk, reaching the rim at the same instant. Because the wall is thin, hesitation for even a few milliseconds shows as a visible ring, so valve-pin opening time is controlled within five hundredths of a second. Pack pressure is held low enough to avoid flash, yet long enough to eliminate sink opposite the ribs under the base.

Cooling circuits follow a simple loop: one circuit circles the core just below the rolling ring, another sweeps the cavity near the base. Water speed is kept above one metre per second to maintain turbulent flow, and the temperature gap between inlet and outlet is held under two degrees Celsius. When the delta is wider, the bowl tends to oval, making it hard for the lid to snap on. Interchangeable bubbler inserts are added under the floor so that the centre of the base cools at the same rate as the wall.

Ejection uses a stripper ring that contacts the bowl just under the rolling ring. Air is introduced one to break the vacuum, then the ring lifts the part in one smooth motion. Because the wall is light, static electricity can make the bowl cling to the core; an ionised air knife neutralises the charge and lets the robot place the part on a stacking post. The post is slightly tapered so the bowls nest securely without wedging.

Material is a food-grade polypropylene with medium melt flow. The grade gives good clarity for content visibility and enough toughness to survive a one-metre drop when filled. A small amount of slip additive is included so that nested bowls separate easily during dispensing. By combining balanced fill, even cooling, and gentle ejection, the injection thin-wall plastic round bowl barrel mould delivers a light, reusable vessel that meets food-service demands at modest cost.