WATER-ASSISTED INJECTION MOLDING
A new method for producing hollow parts: a water-hydraulic system generates high-pressure water injected into a partially filled mold cavity, acting like a plunger to push the melt forward and core out the part. Already commercialized, with clear advantages in handles, automotive cooling pipes, storage tanks and more.
Water-assisted injection molding is similar to gas-assisted: the water-hydraulic system generates high-pressure water and injects it into a partially filled mold cavity, using water pressure to push the melt forward and fill the cavity. The water front acts like a plunger on the molten core of the part; from the water front to the melt, a very thin plastic film solidifies, acting like a high-viscosity core that further pushes the melt forward, thus coring out the part.
This technology has years of practical application history; its process and application continue to evolve, producing uniform wall sections and parts with fewer sink marks and less warpage. Applications have expanded from handles and automotive cooling pipes to transport crates, toys and large storage tanks — typical uses include handles, roof racks, rocker covers, door modules, shovels, brackets, chairs and office furniture.
High-pressure water cools the part interior directly, acting uniformly from inside out. Water's thermal conductivity is 40× that of gas and its specific heat 4×, reducing cooling time to about 25% of gas-assisted — productivity up roughly 4×.
Achieves thinner walls than gas-assisted, saving material and weight. The working medium is water — easy to obtain and recyclable — whereas gas-assisted nitrogen is hard to obtain, costly and non-recyclable.
Uniform wall thickness, good repeatability, smooth inner surface of hollow parts — without the fingering effect and foamy inner surface common in gas-assisted.
For large-diameter parts, gas-assisted yields thicker walls and severe foamy inner surfaces; water-assisted fully overcomes the difficulties gas-assisted faces with large-diameter, longer parts.
The system consists of three main parts: high-pressure water source generator, water pressure controller and automated water pin.
Adopts advanced continuous high-pressure water feeding, wide application range and process adjustment range, full Chinese touch-screen operation system.
Full PLC control, full closed-loop servo pressure control, automatic/manual operation, high-precision industrial PLC module, 10-inch true-color LCD, Simplified-Chinese HMI, 100 process programs stored, intelligent full-Chinese menu with password protection.
Suitable for various water-pin processes, selectively fast open/close via an integrated control unit; adjustable drain-hole position, efficient cleaning, easy installation and removal, compact structure, customizable control pipes.
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