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Plastic Injection Molds: The Most Complete Guide to 2025

Dec23, 2024

What is an injection mold

List of Contents

  1. What Is an Injection Mold?

  2. Why We Need Injection Molds

  3. How Does an Injection Mold Work?

  4. Components of an Injection Mold

  5. What Are the Types of Injection Molds?

  6. How Are Injection Molds Made?

  7. What Materials Are Used for Injection Molds?

  8. What Are the Industries Where Injection Molds Are Used?

  9. What Is the Cost of Injection Mold?

  10. Common Injection Molding Defects​

  11. The Most Common Materials for Injection Molding

  12. Who Are the Key Players in the Plastic Injection Mold Market?

  13. FAQs About Injection Mold

  14. Your Reliable Injection Mold Expert

 

Injection molds are an important part of plastic part molding. They are used to make everything from simple household items to complex electronic components. Here's everything you need to know about injection molds.

What Is an Injection Mold?

In industrial production, plastic materials are made into parts or products of the desired shape by applying pressure. This special tool is collectively called an injection mold.

An injection mold is a tool for producing plastic products. Injection molds can be made with single or multiple cavities. Multi-cavity molds can have identical parts in each cavity or unique parts to create different geometries.

Why We Need Injection Molds

  1. Mass Production: Injection molding allows for the mass production of plastic parts and products. Using molds, we can quickly replicate the geometric shapes of parts thousands or even millions of times. This significantly improves production efficiency and reduces the likelihood of errors.

  2. Complex Geometries: Injection molds can create parts with complex geometries, including undercuts, threads, and very fine details.

  3. Strict Tolerances: Properly designed and manufactured molds can produce parts with very tight tolerances.

  4. Material Versatility: Different mold materials, such as steel and aluminum, can accommodate various plastic resins with different temperature and viscosity requirements.

  5. Economic Feasibility: Although the initial production cost of molds is high, the per-piece cost of injection molding becomes very low in large-volume production, making it economically viable for high-volume manufacturing.

How Does an Injection Mold Work?

Plastic is first heated and melted in the heating barrel at the bottom of the injection machine. It is then pushed by the screw or plunger of the injection machine into the mold cavity through the machine's nozzle and the mold's gating system. The plastic is cooled and hardened to form the product, which is then demolded.

Working principle of injection mold

Components of an Injection Mold

An injection mold is composed of several key components that work together to produce high-quality plastic parts. Here are the main components:

  1. Mold Base: The main structure that holds all the components of the mold together.

  2. Cavity and Core: These are the two halves of the mold that shape the plastic. The cavity forms the outside shape, while the core forms the inside features.

  3. Sprue Bushing: Channels the molten plastic from the injection machine nozzle into the mold.

  4. Runner System: Distributes the molten plastic from the sprue to various cavities in the mold.

  5. Gates: Small openings that control the entry of plastic into the mold cavities.

  6. Ejector Pins: Push the finished part out of the mold after it has solidified.

  7. Cooling System: Consists of channels that circulate cooling fluid to regulate the mold temperature.

  8. Venting System: Allows trapped air and gases to escape from the mold cavity during the injection process.

  9. Guide Pins and Bushings: Ensure precise alignment of the mold halves during the closing process.

  10. Inserts: Replaceable components that allow for the creation of specific features within the mold, such as threads or textured surfaces.

  11. Ejector Plate and Backing Plate: Work with ejector pins to facilitate the removal of the part from the mold.

  12. Return Pins/Springs: Ensure the ejector system returns to its original position after ejection.

  13. Locating Ring: Helps align the mold halves in the injection molding machine.

What Are the Types of Injection Molds?

According to the classification of the production process, injection molds can be divided into five types:

  1. Plastic Injection Mold: The most commonly used molding mold for producing thermoplastic parts, corresponding to plastic injection molding machines.

  2. Plastic Compression Mold: Includes compression molding and transfer molding types. These molds are mainly used for thermosetting plastics and work with pressure molding machines.

  3. Plastic Extrusion Mold: Used to form plastic products with continuous shapes, widely used in processing pipes, rods, monofilaments, plates, films, wire and cable coatings, and profiled materials.

  4. Plastic Blow Mold: Used to form hollow plastic container products, such as beverage bottles and packaging containers. The structure of the blow mold is relatively simple.

  5. Plastic Blister Mold: Uses plastic plates and sheets as raw materials to form simple plastic products, mainly for daily necessities, food, and toy packaging products.

How Are Injection Molds Made?

How Are Injection Molds Made?

A qualified injection mold manufacturing process includes mold design, mold manufacturing, mold processing, mold inspection, and mold testing. This results in the final injection mold product.

What Materials Are Used for Injection Molds?

Injection molds are usually made of steel or aluminum. Steel molds are more durable and can withstand high production volumes but are also more expensive to manufacture. Aluminum molds are less expensive but less durable and suitable for lower volumes.

What Are the Industries Where Injection Molds Are Used?

Injection molds are common in various industries, including construction, food and beverage, and consumer goods.

Aerospace

  • Aerospace: Bezels, chassis components, housings, panels

  • Automotive: Housings, cup holders, dashboard components

  • Consumer Electronics: Battery cases, electronic device cases, electrical switches

  • Medical Technology: Collection tubes, syringes

  • Household Items: Plastic stools, plastic boxes, plastic tables

What Is the Cost of Injection Mold?

The cost of an injection mold can vary depending on the complexity and quantity. A small, simple injection mold typically costs between $500 and $2000. Very large or complex molds can cost $7,000 or more. Buying multiple molds at once can lower the cost per mold. The final price should be negotiated with the manufacturer.

Common Injection Molding Defects​

Injection molding is a complex technique, and many issues can potentially arise. Below I list some problems that can occur due to defects in the mold. Remember that it is much easier to avoid these problems during the mold design stage rather than trying to change things later.

Issue Cause Solution
Flash Excess material leaks out along parting lines due to high injection pressure or worn mold components Adjust injection pressure, improve mold clamping force, ensure proper alignment, replace worn components
Short Shots Incomplete mold cavity filling due to low injection pressure, low melt temperature, or obstructions in runner system Increase injection pressure, raise melt temperature, clear blockages in mold
Sink Marks and Shrinkage Uneven cooling and shrinkage of material, especially in thicker sections Optimize cooling rates, use lower shrinkage materials, adjust mold design for uniform cooling
Warpage Uneven shrinkage rates causing internal stresses and part distortion Modify wall thickness, adjust gate locations, increase clamping pressure, use post-molding stress relief techniques
Burn Marks Material degradation from excessive heat exposure during molding process Follow resin temperature recommendations, monitor material condition, avoid overheating during processing
Flow Lines Visible streaks from flow front progression caused by low injection speed, low melt temperature, or inadequate venting Increase fill speed, raise melt temperature, improve venting, and modify mold design to guide flow more effectively

The Most Common Materials for Injection Molding

Materials

  • Acrylic

  • ABS

  • Nylon (Polyamide or PA)

  • Polyethylene (PE)

  • Polycarbonate (PC)

  • Polypropylene (PP)

  • Polystyrene (PS)

Who Are the Key Players in the Plastic Injection Mold Market?

Some of the notable plastic injection mold manufacturing companies include:

Company Name Location Services
Hingtung Inc Shenzhen,China custom mold, injection molding services
Plastek Industries, Inc. Erie, USA custom mold, injection molding services
LexaMar Corp. Boyne City, USA custom mold, injection molding services
Jones Plastic & Engineering Co., LLC Louisville, USA custom mold, injection molding services
Hi-Tech Mold & Engineering, Inc. Rochester Hills, USA custom mold, injection molding services
MMI Engineered Solutions Saline, USA custom mold, injection molding services
American Tool & Mold, Inc. Clearwater, USA custom mold, injection molding services
Ironwood Plastics, Inc. Ironwood, USA custom mold, injection molding services
Seaway Plastics Engineering, LLC Port Richey, USA custom mold, injection molding services
Alwin Inc. Clintonville, USA custom mold, injection molding services
Decatur Mold, Tool & Engineering, Inc. North Vernon, USA custom mold, injection molding services

FAQs About Injection Mold

faq

Q1: What types of products can be manufactured using injection molds?

A: Injection molds are used to manufacture a wide range of plastic products, including automotive parts, toys, medical devices, and consumer goods such as bottles and containers.

Q2: How long can an injection mold usually be used for?

A: The service life of an injection mold can vary based on a number of factors, including the type of material being molded, the complexity of the part, and the number of cycles used. Generally speaking, injection molds can be used for 10 years with proper maintenance and care.

Q3: How long is the general lead time for injection mold manufacturing?

A: The general mold manufacturing cycle is about 20-45 days. If the product is more complicated and has higher requirements, the delivery time will be longer.

Your Reliable Injection Mold Expert

plastic bucket mold factory

Hingtung is a leading plastic mold manufacturer in China, we focuse on the development and production of precision injection molds for mid-to-high-end brands. We provide a complete set of solutions from product design/precision mold manufacturing/injection molding and assembly/after-sales service, which are widely used in home appliance shell fittings, medical and medical equipment injection molding parts, cosmetic packaging injection molding parts and other fields.

We have obtained ISO9000, ISO14000 certification, BSCI certification, 3C, and other certifications. Our customers are located in more than 100 countries worldwide.

If you need custom Injection Molding Services from China, then you can contact us directly. We can help you with anything.

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