What is Plastic Injection Molding & How Does It Work 2025?

Plastic components are essential in countless industries — from automotive and medical devices to consumer electronics and household appliances. Across these sectors, injection molding of plastics plays a vital role in delivering durable, precise parts that protect, enhance, and support product performance.

Among modern manufacturing methods, injection molding stands out as one of the most relied-upon processes for producing high-quality, repeatable plastic components. The global plastics injection molding market is forecast to grow at a CAGR of 4.6% through 2028, fueled by its efficiency and scalability.

However, while plastic mold injection enables rapid high-volume production, the process must be carefully managed to ensure consistent quality. In this guide, we’ll explore:

• What is injection molding?

• How the plastic injection moulding process works

• How Huazhiheng delivers industry-leading results

What is plastic injection molding?

At its core, plastic injection moulding is the process of melting thermoplastics and feeding them under pressure into precision-engineered plastic injection molds. Using advanced electric or hydraulic machinery, this molten material is shaped within a mold tool, then cooled into a finished part.

Key advantages of the injected molded plastic process include:

• Design flexibility – With the right plastic injection mould and thermoplastic choice, manufacturers can create simple or highly complex geometries.

• Production efficiency – Once set up, production runs can yield thousands of identical parts quickly.

• Cost-effectiveness – Although the mold is a major upfront investment, high-volume runs reduce per-part costs significantly.

• Consistency – Tight process controls ensure uniformity across large quantities.

• Quality – The process delivers exceptional detail, strength, and surface finish.

How does the plastic injection molding process work?

A series of carefully controlled stages define the injection molding cycle. Let’s look at them more closely.

Step 1: Selecting the right thermoplastic and mold

Choosing the correct thermoplastic material and plastic injection molds is the foundation of success. Mold tools consist of a fixed cavity and a moving core, typically crafted in steel or aluminum to withstand high pressures and temperatures.

Before producing the final plastic injection mould, prototypes are often built using CAD design and 3D printing to test how the selected thermoplastic behaves with the chosen mold design.

Step 2: Feeding and melting the thermoplastic

In an injection molding machine — either electric or hydraulic — raw thermoplastic pellets are poured into a hopper, transported by a rotating screw through a heated barrel, and melted into a homogeneous molten state.

Step 3: Injecting the plastic into the mold

Once molten, the plastic collects ahead of the screw. Meanwhile, the mold halves close tightly under clamp pressure. When the set injection pressure is reached, the molten plastic is driven through the gate into the cavity, filling the plastic injection mould instantly.

Step 4: Holding and cooling time

In the holding phase, pressure is maintained to pack and shape the part fully. Cooling immediately follows, allowing the injection-molded plastic to solidify to its final geometry without warping.

Step 5: Ejection and finishing processes

Once cooled, the mold opens, and ejector pins push out the part. Post-processing, such as trimming excess material, polishing, or adding finishes, can be carried out before packaging and shipment.

Injection molding at Huazhiheng

Huazhiheng has made plastic injection moulding a cornerstone of its production capabilities. As part of our ESG goals, we’re transitioning from older hydraulic systems to efficient electric-powered machines, meaning lower energy consumption and consistent, high-quality injected molded plastic output.

Our UK-based Centre of Excellence allows us to test innovative materials and develop more sustainable solutions for customers worldwide. With over 45,000 molds available and custom tooling options, we support projects of all scales and specifications.