Part Ejection

Clamp open is the phase of the cycle in which the two halves of the mold separate after part solidification, to allow ejection. It is the first visible mechanical motion after injection and cooling. ## How it works Once cooling time is up, the controller releases the clamp lock and moves the moving platen along a programmed velocity / position profile: - Fast open: long stretch at high speed, away from the part - Slow open: near the part, to minimize shock or tear ## Typical parameters - Total stroke: 200 – 1500 mm depending on part - Fast velocity: 300 – 600 mm/s - Slow final velocity: 50 – 100 mm/s - Total time: 0.5 – 1.5 s on modern machines - Final open position: typically 1.2 × part height ## Importance in the cycle Every tenth of a second of opening multiplies by thousands of cycles per day. Open accounts for 5 – 10 % of cycle time and is the first optimization target alongside ejection. ## Common issues Excessive over-opening that lengthens the cycle, part tearing from too-fast opening, jamming from poor robot positioning, and non-parallel motion from misaligned tie bars.

EOAT (End-Of-Arm Tooling) is the tool mounted on the wrist of an industrial robot that handles freshly molded parts: removing them from the mold, positioning them, separating the sprue, stacking or delivering them to secondary operations. It is the mechanical interface between the robot and the part. ## Role of EOAT in injection molding The EOAT enters the mold during opening, picks up the part with suction cups or grippers, removes the sprue if any, and places the part on a conveyor or work station. Its design defines the extraction time —typically 0.5 to 3 s— and therefore a significant chunk of total cycle time. ## Common components - Base plate with the robot-wrist interface - Vacuum suction cups (for flat, smooth surfaces) - Pneumatic or electric grippers (for parts without suction surfaces) - Presence sensors and vacuum switches - Sprue cutters - Pneumatic system with control valves ## Types of EOAT - Off-the-shelf for simple parts - Custom aluminum or 3D-printed for complex geometries - Modular reconfigurable (30×30 mm profile systems) - Multi-part for family or multi-cavity molds ## Design considerations and common issues Excessive weight (slows the robot), interference with the mold, vacuum loss on porous surfaces, gripper wear failures, and misalignment when returning to the mold. Mitigated with path simulation, redundant sensing and preventive maintenance.

A molded part is the finished plastic component produced by injection molding, its shape formed by the mold cavity. It is the deliverable of the whole process — one part per cavity, per shot. ## Part vs shot - Molded part: a single finished component (its mass is the part weight, see cavity weight). - shot: everything injected in one molding cycle — all parts plus runners and sprue. A 4-cavity mold yields 4 molded parts per shot. ## What defines a good part A molded part is judged against the print on several axes: - Dimensions: within tolerance, allowing for contraction (shrinkage) and dimensional stability over time. - Weight: stable shot-to-shot — the simplest health check of the process. - Appearance: free of sink, flash, short shots, splay, weld lines and burns. - Mechanical / functional: strength, fit and function as designed. A part that fails any of these becomes scrap. ## From mold to inspection After cooling, the part is freed by part ejection and removed by free-fall, robot or operator, then it may be degated, inspected and packed. ## Related terms - See also: cavity, shot, molding cycle, part ejection, dimensional stability ## What is a molded part in injection molding? It is the finished plastic component shaped by the mold cavity, produced one per cavity each shot, and judged on dimensions, weight, appearance and function. ## What is the difference between a molded part and a shot? A molded part is one finished component; a shot is everything injected in a cycle — all the parts plus the runners and sprue. ## How is molded-part quality checked? By dimensions against tolerance, stable part weight, cosmetic appearance (no sink, flash or short shots) and mechanical/functional performance; failures are scrapped.

Molding Cycle is the complete sequence of phases that produces one injection-molded part, from mold close to the next mold open. Each phase contributes its time and together they determine press productivity and part cost. ## Phases of the cycle 1. Clamp close and full tonnage applied 2. Injection: the screw forces molten material into the cavity along a velocity profile 3. Hold (packing): constant pressure to compensate for shrinkage during initial cooling 4. Cooling + plasticizing: the screw rotates to prepare the next shot while the part cools 5. Clamp open 6. Ejection and robot / EOAT motion ## How to calculate cycle time Cycle time is the sum of every phase: Cycle time = clamp close + injection + hold + cooling + mold open + ejection Plasticizing (screw recovery) runs in parallel with cooling, so it only counts when it is longer than the cooling phase. Cooling dominates and scales with the square of the thickest wall: doubling wall thickness roughly quadruples cooling time. This wall-thickness rule is the single biggest lever on overall cycle time. ## Cycle time example A representative thin-wall part on a 150-ton press: | Phase | Time | |-------|------| | Clamp close | 1.0 s | | Injection | 1.5 s | | Hold | 4.0 s | | Cooling | 8.0 s | | Mold open + eject | 2.0 s | | Total cycle | 16.5 s | ## How does material affect the cycle? Semi-crystalline resins (PP, PA, POM, HDPE) release more latent heat as they crystallize and usually need longer cooling than amorphous resins (ABS, PC, PS) at the same wall thickness. Melt temperature, mold temperature and the resin's ejection (heat-deflection) temperature all set the minimum cooling time. ## Optimization Conformal cooling channels that follow part geometry, a multi-stage injection profile, plasticizing in parallel with opening, valve gates on hot runners for clean closure, and elimination of dead time on the robot side. ## How long is an injection molding cycle? Thin-wall packaging parts cycle in 3–15 s, while thick technical or engineering parts can take 30–60 s or more. Cooling sets the floor: the thicker the wall, the longer the minimum achievable cycle. ## Which phase takes the longest? Cooling, almost always. It typically accounts for 50–70 % of the total cycle, which is why conformal cooling and wall-thickness reduction give the biggest gains. ## What is the difference between molding cycle and cycle time? "Molding cycle" describes the sequence of phases; "cycle time" is the numerical total in seconds reported on the cell's OEE. The cycle is the what, the cycle time is the how long.