Radial Base Ribs Stiffen Cup Without Adding Wall Thickness

A single plastic thin-wall paint bucket cup mould is a dedicated tool that forms a light, straight-sided vessel ready to hold coatings, adhesives, or DIY small-batch mixes. The design task is simple in outline yet demanding in detail: remove every unnecessary gram while keeping the rim round enough to accept a snap-on lid and the base strong enough to survive a waist-high drop when full. Engineers start by setting the capacity, usually one or two litres, then taper the side wall at barely one degree so the cup releases easily from the core. A shallow rolling ring is added near the top; this stiffens the open edge and gives the user a secure finger grip during pouring.

Wall thickness is targeted close to half a millimetre. At this gauge, the part cools quickly, but 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 the drop test.

Gate position is chosen early through flow simulation. A single pinpoint gate placed at the cup 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 channels 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 cup 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 cup 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 cup 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 cups nest securely without wedging.

Single plastic thin-wall paint bucket cup mould is a general-purpose polypropylene with medium melt flow. The grade gives good chemical resistance to water-based paints and enough clarity for the user to see the remaining volume. A small amount of slip additive is included so dried paint flakes can be peeled away before the next mix.