Injection Molding Machine Shooting Cylinder

Dock. Hold. Inject.
Retract. Repeat.

After forges, furnaces, filter presses, and cement mills — a different world. The injection molding machine is clean, fast, and precise. The shooting cylinder slides the entire injection unit forward on its guide rails, docking the nozzle tip against the mold sprue. It holds the nozzle-to-mold contact force during the 1–30 second injection phase, preventing molten plastic from leaking at the junction. Then it retracts. Every cycle. Every 10–60 seconds. Thousands of times per shift.

When the injection screw pushes molten plastic through the nozzle, the plastic pressure at the nozzle tip can reach 50–200 MPa. This pressure tries to push the nozzle away from the mold sprue. If the nozzle separates — even by 0.1 mm — molten plastic squeezes through the gap, creating a "nozzle drool" or a "flash ring" around the sprue that must be trimmed from every part. Repeated nozzle separation causes sprue bushing erosion, requiring expensive mold repair.

The shooting cylinder's contact force must exceed the injection pressure's separating force by a comfortable margin — ensuring the nozzle stays sealed throughout the injection and packing phases. But the contact force cannot be arbitrarily high: excessive force compresses the nozzle tip against the sprue bushing, accelerating wear on both surfaces and potentially cracking the sprue bushing (especially on small moulds with thin sprue inserts).

This touch-off force is set by the shooting cylinder's hydraulic pressure — the machine operator adjusts the cylinder pressure to match the injection pressure and the mould's sprue geometry. Korea Ever-Power designs the shooting cylinder bore diameter to produce the required force range at the machine's system pressure, providing a proportional control window from minimum contact (for small moulds with delicate sprue inserts) to maximum contact (for large moulds with robust sprue bushings).

A Different World — Clean, Fast, Precise

The previous 23 products in this catalogue operate in forges (1,200 °C, scale, splash), steel mills (1,800 °C, fume, molten metal), cement plants (extreme dust, continuous vibration), and filter presses (corrosive slurry). The injection molding shooting cylinder operates in a clean factory environment — indoor, climate-controlled, with filtered ambient air and stable temperatures between 15–35 °C.

The shooting cylinder operates in a kinder environment than the forge or cement plant — but the cycle count is demanding. At one extend-retract cycle every 15–60 seconds, the cylinder accumulates 500,000–2,000,000 cycles per year. This is fewer than the cement cooler feeding cylinder (#23) but far more than the grinding or roll over cylinders (#20–22).

The bore is honed to Ra 0.2–0.4 µm — the Korea Ever-Power standard. The rod is chrome plated at 30–50 µm (lighter than the 80–100 µm used for forge and cement cylinders, because the clean environment does not attack the chrome). Seals are standard NBR or polyurethane — selected for low friction and high cycle life rather than extreme temperature or chemical resistance.

The end-of-stroke cushion on the extend side is critical — it decelerates the injection unit just before the nozzle contacts the sprue bushing. Without the cushion, the nozzle impacts the sprue at travel speed, which damages the nozzle tip seat over repeated cycles. Korea Ever-Power calibrates the cushion for the specific injection unit mass and maximum advance speed during factory testing.