Plastic Injection Molding: A Complete Guide of Workflow, Cost, and FAQ

All You Need to Know About Plastic Injection Molding: Process, Tooling, Cost & FAQs

Plastic injection molding is a highly efficient and widely used manufacturing method for mass production of plastic parts, from automotive components to outdoor buckles and consumer products. In this guide, we’ll walk you through the entire process—from mold design to production—along with key topics like mold flow analysis, low-volume tooling, and common defects.

What is Plastic Injection Molding?

Plastic injection molding involves melting plastic pellets and injecting them into a mold cavity to form parts. It allows:

• High repeatability and precision
• Cost-effective mass production
• Compatibility with various materials (ABS, PP, PA, TPU, etc.)
• Complex shapes and tight tolerances

Injection Molding Process Flow

1. Design for Manufacturability (DFM)
   Ensuring draft angles, wall thickness, and material flow are suitable for molding.
2. Mold Flow Analysis
   CAE simulation to predict filling, cooling, and warpage. Helps reduce trial-and-error and cost.
3. Mold Fabrication
   Steel or aluminum molds are built with cooling systems, ejection pins, and gating structures.
4. Mass Production
   Molten plastic is injected, cooled, and ejected in cycles as short as a few seconds.
   

Types of Injection Molds

Low-Volume Tooling Strategy

• Aluminum mold for fast, low-cost prototyping (5,000–10,000 shots), also known as "Sample mold"
• Modular mold inserts for flexibility (mold core replacing)
• Shared mold base to reduce setup cost (family mold)

Plastic Mold Cost Breakdown

The cost of mold depends on:

• Cavity count
• Product complexity (undercuts, threads, sliders)
• Mold material
• Projected mold life

Typical cost range: USD $1,000 to $10,000+

Common Injection Defects & Solutions

FAQ – Frequently Asked Questions

Q1: Is injection molding suitable for low-volume production? I don't require high volume at the moment.

Yes. With the right tooling approach like sample mold, mold core replacing, or shared mold base, you can achieve cost-effective runs of 1,000–5,000 pcs.

Q2: Can I request a specific resin brand or grade?

Absolutely. We support branded materials like BASF, Dupont, or RoHS/REACH compliant resins; if you have special requirement, such as UV resistance, cold resistance, FR (flame retardant), we are pleased to offer solutions.

Q3: How long does injection mold making take?

Typically 20–45 working days depending on complexity of mold.

Q4: Do I need mold flow analysis?

Mold flow analysis is unnecessary for injection molding, but it is highly recommended for complex parts or high-volume tools—it saves time and cost.

Mold flow analysis software — Moldex3D is currently used by Ji-Horng Plastic Co., Ltd., which is used to simulate the forming process of plastic products in molds to diagnose, verify, and then optimize the product design. The application of moldflow simulation help saving a lot of time as traditional ways to build models for injection simulation takes a lot of time, it can predict possible product defects in advance, avoiding repeated modifications to product design after the mold is completed.

Final Thoughts

Injection molding is a powerful tool—when paired with the right design, team, and planning, it can turn your idea into scalable success. Whether you’re looking to prototype or launch a global product line, we’re here to support you from mold design to production.

Need a quote or mold flow consultation? Contact us with your 3D/2D file or physical sample today!

E-mail: service@ji-horng.com.tw