Injection Molding Principles and Practical Analysis of Multi-Color Water Cup Accessory Production (Injection Molding Principles Chapter)

There’s a story in every cup, warmth in every life. Hello everyone, "Dong Dong's Cup Talk" is here. In previous shares, we mentioned that our factory not only produces water cups but also specializes in plastic mold manufacturing. http://www.zhanyict.com/en/ProductsDetail-VB-10504.htmlThe production of water cups relies heavily on plastic accessories, which is why our factory boasts a professional and well-equipped injection molding department.

Today, based on years of hands-on experience and real-world cases, we’ll share a practical analysis of injection molding principles and the production of multi-color water cup accessories. http://www.zhanyict.com/en/ProductsDetail-VB-10504.htmlGiven the extensive content, we’ll break it down into multiple chapters.

I. Injection Molding Principles and Equipment Basics

1. Injection Molding Production Process

- Plasticizing Stage: The screw rotates to heat pelletized material into a molten state (PP: ~200–230°C; PC: 280–320°C).

- Injection Stage: The screw pushes forward, injecting the melt into the mold cavity under high pressure (typically 60–150 MPa).

- Holding & Cooling: http://www.zhanyict.com/en/ProductsDetail-VB-10504.htmlCompensates for shrinkage to prevent sink marks while cooling and solidifying the part (accounts for over 60% of the cycle time).

- Ejection & Removal: The ejector system releases the finished product, completing the cycle (cycle times range from 15 seconds to 3 minutes).

2. Core Parameters of Injection Molding Machines

- Clamping Force (Tonnage): Determines the projected molding area (e.g., a 180-ton machine suits cup lids ≤300 cm²).

- Screw L/D Ratio: http://www.zhanyict.com/en/ProductsDetail-VB-10504.htmlHigh-viscosity materials like PC require ≥22:1 to prevent uneven plasticization.

- Shot Weight (g): Should be 1.5–2 times the part weight (e.g., a 350g cup body needs ≥500g shot weight).

Case Study: A dual-color sports cup lid (ABS+TPU) suffered severe flash at the parting line due to insufficient clamping force (originally used a 450-ton machine). http://www.zhanyict.com/en/ProductsDetail-VB-10504.htmlUpgrading to a 680-ton machine resolved the issue.