Technical Insights

Injection molding & material know-how from our workshop

PEI (Polyetherimide): A 170°C, V-0 Flame-Retardant, Drinking-Water-Safe Engineering Plastic — When Should You Choose It?

Ningbo Ruijing Mold & Plastic Co., Ltd., Sam Qian

PEI (Polyetherimide): A 170°C, V-0 Flame-Retardant, Drinking-Water-Safe Engineering Plastic — When Should You Choose It?

A deep-amber, translucent plastic part that sits in hot water for the long term, must be safe for drinking-water contact, and has to withstand high temperature — that is a key component inside a therm...

Oct 7, 2026

What Is Self-Skinning PU Foam Insulation?

Ningbo Ruijing Mold & Plastic Co., Ltd., Sam Qian

What Is Self-Skinning PU Foam Insulation?

1. Six Functions in One Part Self-skinning (integral-skin) polyurethane foam insulation jackets are molded in a single cycle — a dense, smooth outer skin forms over a closed-cell foam core. One part d...

Oct 5, 2026

How to Use Our Free Injection Molding Cost Estimator — 3D Preview, Auto-Measure & Material Assistant

Ningbo Ruijing Mold & Plastic Co., Ltd., Sam Qian

How to Use Our Free Injection Molding Cost Estimator — 3D Preview, Auto-Measure & Material Assistant

Getting a price for an injection-molded part usually means emailing a drawing, waiting days for a quote, and hoping the number doesn't surprise you. We built a free online estimator to change that — a...

Sep 20, 2026

How Much Do Injection Molds and Molded Parts Cost in China? Get an Instant Estimate in 30 Seconds

Ningbo Ruijing Mold & Plastic Co., Ltd., Sam Qian

How Much Do Injection Molds and Molded Parts Cost in China? Get an Instant Estimate in 30 Seconds

Every injection molding buyer asks the same first question: how much will it cost? Here's the straight answer — a production-grade mold made in China ranges from about $1,500 for a simple single-cavit...

Sep 20, 2026

The Real Cost of Low-Volume Injection Molding (and Why MOQ Is Often a Myth)

Ningbo Ruijing Mold & Plastic Co., Ltd., Sam Qian

The Real Cost of Low-Volume Injection Molding (and Why MOQ Is Often a Myth)

The short answer: small-batch injection molding is not expensive because the parts are expensive — it is expensive because you are paying off the mold over fewer pieces. Find a low-MOQ manufacturer, a...

Sep 13, 2026

PEI vs PSU vs PEEK vs PPS: How to Choose a High-Temp Plastic

Ningbo Ruijing Mold & Plastic Co., Ltd., Sam Qian

PEI vs PSU vs PEEK vs PPS: How to Choose a High-Temp Plastic

The short answer: choose PEEK when nothing else survives the heat, chemicals and load; PPS for chemical resistance at a lower price; PSU for medical and sterilisation; PEI for strong, flame-retardant ...

Sep 13, 2026

Metal-to-Plastic Conversion: When to Replace Machined Metal Parts

Ningbo Ruijing Mold & Plastic Co., Ltd., Sam Qian

Metal-to-Plastic Conversion: When to Replace Machined Metal Parts

The short answer: if your metal part is a structural housing, bracket, cover, or fitting that doesn't carry extreme loads or sit above 250°C, you can usually replace it with an engineering plastic — a...

Sep 13, 2026

Pre-Deformation of Glass-Fiber-Filled Injection Molded Parts

Ningbo Ruijing Mold & Plastic Co., Ltd., Sam Qian

Pre-Deformation of Glass-Fiber-Filled Injection Molded Parts

How to predict warpage before cutting steel — and get a good part on the first trial shot. The misread common sense Warpage in injection molded parts has always been a headache — especially for engine...

Sep 12, 2026

How Much Does Nylon Grow When It Absorbs Moisture?

Ningbo Ruijing Mold & Plastic Co., Ltd., Sam Qian

How Much Does Nylon Grow When It Absorbs Moisture?

If you mold nylon parts, you have almost certainly hit this "mystery": right out of the mold, the dimensions pass inspection. Yet a few months later, the customer reports the parts no longer fit. The ...

Sep 8, 2026