Plastic Mold Technology and Hot Runner Principles: What Are They? (Part 1)

A cup holds stories, and life carries warmth. Hello everyone, "Dong Dong's Cup Talk" is here! Most of my followers already know which industry I’m in—that’s right, I’ve been working in the water cup industry for many years. http://www.zhanyict.com/en/ProductsDetail-VB-10424.htmlBut what you might not know is that my factory doesn’t just produce stainless steel cups and insulated tumblers; we also manufacture all kinds of plastic cups and sports bottles. Naturally, this means our factory is also capable of producing various plastic molds.

Today, I’ve invited Mr. Feng, a specialist with over 20 years of experience in plastic mold development at our factory, http://www.zhanyict.com/en/ProductsDetail-VB-10424.htmlto share insights on plastic mold technologies and the principles of hot runner systems. Since there’s a lot to cover, I’ll break this into four parts.

I. Core Processes and Key Stages in Plastic Mold Manufacturing

Design Phase

- Product Analysis: For components like insulated cup lids or shells, key structural features (threads, snap-fits, sealing surfaces), wall thickness uniformity, and draft angles (recommended ≥1°) must be defined.

- Parting Line Design: Threaded areas in cup lids require side-core pulling mechanisms, http://www.zhanyict.com/en/ProductsDetail-VB-10424.htmlwhile parting lines on shells should avoid visible surfaces (e.g., logo areas).

- Mold Flow Analysis: Software like Moldflow simulates resin flow to predict shrinkage and weld line locations (Failure case: A cup lid leaked due to weak sealing from unanalyzed weld lines).

Manufacturing & Machining

- Material Selection: High-gloss shells require S136 mirror-polish steel (HRC 48-52), while standard parts can use P20 steel.

- Precision Machining: Threaded cores need slow wire-cutting (±0.005mm accuracy), http://www.zhanyict.com/en/ProductsDetail-VB-10424.htmland cavities require mirror polishing (Ra ≤ 0.02μm).

- Cooling System: Conformal cooling channels in lid molds cut cycle times (Success case: A project boosted cooling efficiency by 30%, reducing cycle time from 25s to 18s).

Trial & Adjustment

- First Trial (T1): Focus on verifying smooth lid ejection and checking shell surfaces for shrinkage.

- Parameter Tuning: http://www.zhanyict.com/en/ProductsDetail-VB-10424.htmlAdjust holding pressure/time for PP/PC materials (Failure case: 2,000 PC shells were scrapped due to sink marks from insufficient holding pressure).

(To be continued in Parts 2–4...)