What is Water-assisted injection molding?

Water-assisted injection molding is an advanced technology within the plastic injection process, designed to manufacture hollow parts or internal channels efficiently and precisely. This technique is based on the same principles as conventional injection molding but incorporates an additional stage where pressurized water is injected into the mold to push the molten plastic toward the cavity walls, creating a hollow structure inside.

This solution is particularly useful for components that require good structural rigidity with reduced weight, as found in the automotive, appliance, and industrial product sectors. By using water as an assisting agent, faster cooling and a more uniform material distribution are achieved, resulting in shorter production cycles and superior surface quality.

One of the main advantages of water-assisted injection molding is the ability to produce complex parts with hollow sections without the need for additional assemblies or post-processing. This reduces costs, minimizes material usage, and optimizes component design—something especially valued in industries where weight savings and production efficiency are key factors.

During the process, plastic is first partially injected into the mold. Then, a high-pressure water jet is introduced, displacing the still-molten plastic core toward the mold walls. This action creates internal cavities that would be very difficult or even impossible to achieve using conventional techniques. Furthermore, the contact between water and the internal mold walls accelerates the material’s cooling, contributing to greater productivity.

Water-assisted injection molding also offers benefits in terms of dimensional stability. By reducing wall thickness in internal areas, residual stress and shrinkage defects are minimized. This results in more homogeneous parts with fewer deformations—essential for technical and high-performance applications.

To successfully apply this technology, molds must be specifically designed to allow for controlled water flow and proper drainage without leaving residue. In addition, the injection machinery must be equipped with pressure and temperature control systems that ensure perfect synchronization between the injection of plastic and water.

At Plásticos Lezo, we have integrated water-assisted injection molding as part of our technological offering to meet our clients’ needs for high-quality technical parts. This technique allows us to manufacture lighter, more functional, and more sustainable products while maintaining the highest standards of precision and strength. Our engineering team works closely with each client to tailor the mold design and process parameters to the project’s specifications.

Thanks to our experience and continuous investment in innovation, we are able to offer efficient solutions that combine performance, aesthetics, and sustainability. We are committed to technologies that enhance our clients’ competitiveness and contribute to more rational resource use without compromising on quality or reliability.

Water-assisted injection molding represents a significant advancement in plastic part manufacturing, offering a versatile and cost-effective alternative for products that require lightness, precision, and strength. In a market increasingly focused on process optimization and sustainability, this technology positions itself as a strategic solution for multiple industrial sectors.