Email: keenhu@lztooling.com | Whatsapp/Wechat/Phone: +86 134 1694 6882
Email: keenhu@lztooling.com | Whatsapp/Wechat/Phone: +86 134 1694 6882
Custom general plastics injection molding with LTC Plastic, with design and engineering support, DFM, OEM, ODM, mold making, post-finishing and shipment support
Introduction to General Plastics Injection Molding
Injection molding is one of the most essential manufacturing methods in the plastics industry. Among all materials, general plastics—also known as commodity plastics—are widely used for producing molded plastic parts for both consumer and industrial products. These materials are cost-effective, versatile, and ideal for high-volume production, making them a perfect fit for plastic injection molding processes.
This guide covers plastic injection molding techniques, including thermoplastic injection molding, custom plastic molding, and key considerations for mold design, injection molding machines, and processing parameters. It provides insights for engineers, manufacturers, and businesses seeking to manufacture durable, precise, and efficient plastic components.
By understanding material properties, tooling requirements, and production best practices, professionals can optimize plastic injection molding to achieve consistent quality, reduce defects, and expand applications of general plastics across multiple industries.
General plastics injection molding is the process of producing components from widely used, low-cost thermoplastics using injection molding machines. The process involves melting plastic pellets and injecting the molten material into a tool or mold cavity. Once cooled, the injection-molded component solidifies and is ejected for further assembly or finishing.
Common general plastics include:
Polypropylene (PP)
Polyethylene (PE)
Polystyrene (PS)
Acrylonitrile Butadiene Styrene (ABS)
Polyvinyl Chloride (PVC)
Certain polycarbonate blends or polyurethane compounds for commodity grades
These materials are valued for their low cost, ease of processing, and versatility across multiple applications and industries, from consumer goods to industrial products. While they lack the high mechanical or thermal performance of engineering plastics, general plastics are sufficient for everyday general plastics manufacturing tasks.
This molding process can also be combined with custom designs or thermoforming for added flexibility, making it an essential method for producing cost-effective, reliable plastic parts for mass production.
Understanding the properties of general plastics is essential for optimizing polymer processing and preventing plastic molding defects during production. These materials share several common characteristics:
Moderate tensile strength suitable for everyday use
Adequate impact resistance, varying by type
Lightweight yet durable enough for precision plastic components
Not recommended for high-load structural applications
Ideal for molded plastic assemblies across multiple industries
Relatively low melting and glass transition temperatures
Heat-resistant up to approximately 80–120°C
Limited thermal stability compared to engineering plastics
Sufficient for molded plastics for consumer goods and molded plastics for electronics
Resistant to water, mild acids, and bases
Limited resistance to strong solvents, oils, and high-temperature chemicals
Good insulating properties for most electrical applications
Commonly used for housings, plugs, switches, and molded plastics for automotive applications
Highly cost-effective
Widely available globally
Compatible with high-volume production and routine mold maintenance
Works efficiently with a variety of thermoplastic resins for injection-molded products
These properties make general plastics ideal for injection molding, delivering versatile, cost-effective, and reliable solutions across consumer, automotive, and electronics applications.
Here’s an overview of widely used general plastics in injection molding:
Polypropylene (PP)
Lightweight, chemical-resistant, and fatigue-resistant, PP is ideal for low-cost plastic parts such as packaging, containers, and automotive components. Its low density reduces material costs, while its plastic part durability makes it suitable for everyday applications.
Polyethylene (PE)
Available as HDPE (high-density) and LDPE (low-density), PE offers flexibility, impact resistance, and moisture resistance. Common applications include bottles, packaging films, and containers. PE works well with plastic overmolding and multi-material molding due to its versatility.
Polystyrene (PS)
Rigid and available in transparent (crystal) or opaque grades, PS provides excellent dimensional stability. It is widely used in disposable cups, packaging, and consumer electronics. PS can also be enhanced with reinforced plastics or color matching for aesthetic and functional requirements.
Acrylonitrile Butadiene Styrene (ABS)
ABS combines toughness, rigidity, and good surface finish. It is easy to process and paint, making it popular for automotive interiors, appliance housings, and toys. ABS is compatible with automated plastic molding systems and benefits from precise injection molding process parameters.
Polyvinyl Chloride (PVC)
PVC is available in rigid or flexible grades, offering chemical resistance and durability. It is commonly used for pipes, window frames, and fittings. Manufacturers value PVC for its high-temperature plastics applications, mold flow analysis compatibility, and recycle potential, enhancing production capability for sustainable plastic parts.
These general plastics provide cost-effective, versatile solutions for a wide range of industries, enabling high-volume and reliable injection molded products.
The injection molding process for general plastics follows a standard sequence designed for high-volume plastic production and consistent quality.
Material Preparation
Plastic pellets, including PP or regrind material, are prepared for processing. Drying is usually minimal except for hygroscopic grades like ABS. Proper handling ensures uniform resin quality and reduces defects in the injection-molded part.
Melting
Pellets are fed into the screw of the injection molding machine, where they are heated to a plastic melt temperature typically ranging from 180–250°C, depending on the material. This step ensures the polymer is fully molten for smooth flow into the mold cavity.
Injection
Molten plastic is injected into a pre-designed cavity within the mold tooling under controlled pressure, forming and speed. Adjusting part tolerances and injection parameters is critical for achieving precise dimensions and high-quality plastic prototypes or production parts.
Cooling
The mold cools the injection molded part, solidifying the material. Production cycle time is influenced by wall thickness, material type, and mold design. Efficient cooling helps maintain dimensional stability and reduces warping.
Ejection
Once solidified, the part is ejected using pins or mechanical systems. Proper mold design, including draft angles of 1–3°, ensures smooth release and protects the part from damage during plastic fabrication.
This process allows manufacturers to produce cost-effective, durable, and precise plastic components for consumer products, automotive applications, and industrial uses.
Cost-Effectiveness
General plastics are highly affordable, with low-cost raw materials and mold requirements. This makes them ideal for mass production and keeps the injection molding cost per part competitive, benefiting both manufacturers and end-users.
High Production Efficiency
These materials support fast processing cycles and are compatible with automated injection molding machines, enabling rapid product development and high-volume output. Efficient processing also reduces labor and energy costs while maintaining the consistent quality of plastic components.
Design Flexibility
General plastics can be molded into complex shapes and customized with high-clarity plastic molding, various colors, or different textures. This versatility allows designers and manufacturers to meet aesthetic and functional requirements across multiple industries.
Recyclability
Many general plastics grades can be reprocessed and reused, supporting sustainable plastic injection molding practices. Recycling reduces production waste and contributes to environmentally responsible manufacturing without compromising part quality.
Wide Range of Applications
Thanks to their balance of performance, cost, and processability, general plastics are suitable for consumer goods, packaging, automotive, electronics, and industrial components. Combined with the manufacturer’s expertise in plastic resin selection and mold design, these materials provide reliable, durable, and versatile solutions for a variety of plastic components in modern manufacturing.
General plastics are widely used across industries due to their cost-effective, versatile, and high-quality characteristics.
Consumer Products
Includes household containers, toys, kitchenware, and appliances. These parts benefit from dimensional consistency and the ability to meet tight specifications.
Packaging
Used for bottles, caps, trays, and disposable packaging. Materials like rigid and flexible polyurethane foam can also be incorporated for added functionality and durability.
Automotive
Interior panels, trims, clips, and housings are manufactured from general plastics to produce production parts that are lightweight yet durable, ensuring consistent thickness and performance.
Electronics
Housings, switches, connectors, and enclosures rely on general plastics for precision, insulation, and reliable products and services in consumer and industrial electronics.
Construction
Used for pipes, fittings, panels, and window frames. The materials maintain dimensional stability and long-term durability under varied environmental conditions.
Industrial
Components for machinery, tools, and lightweight enclosures are produced efficiently, providing high-quality and cost-effective solutions across multiple applications, including PC parts and other polymer-based assemblies.
These applications demonstrate the versatility and reliability of general plastics in creating functional, durable, and economically manufactured products.
General plastics are cost-effective and suitable for high-volume, everyday applications, while engineering plastics offer superior mechanical, thermal, and chemical performance for demanding, precision-critical parts.
| Feature | General Plastics | Engineering Plastics |
|---|---|---|
| Cost | Low | High |
| Mechanical Strength | Moderate | High |
| Thermal Resistance | Low to Medium | High |
| Application | Consumer, packaging | Industrial, automotive, electronics |
| Ease of Processing | Easy | Moderate to Difficult |
| Common Examples | PP, PE, PS, ABS, PVC | PC, PA, POM, PBT, LCP |
General plastics are ideal for non-structural, high-volume applications where cost efficiency is more important than extreme performance.
The general plastics injection molding industry is evolving rapidly, driven by efficiency, sustainability, and product performance.
Sustainable and Recycled Materials
Manufacturers increasingly produce parts from recycled PP, PE, and ABS, meeting demand for eco-friendly products while maintaining consistent physical properties.
Automation and Smart Factories
Robotics and automated systems enhance the handling of parts and assemblies, enabling high-volume production of single parts or composite parts with consistent quality. Real-time monitoring of processing temperatures, injection pressure, and cooling time improves efficiency and reduces defects.
Lightweighting
Optimizing wall thickness and mold design reduces material usage without compromising strength, improving production efficiency and part performance.
Advanced Coloring and Surface Finishing
Innovations in runner systems, gate design, and surface textures allow multi-color injection, matte or glossy finishes, and enhanced surface finish of molded components.
3D Printed Inserts
The use of additive manufacturing for hybrid molds shortens lead times for prototyping and enables customized plastic shrinkage compensation, precise wall thickness, and improved quantity control in production.
These trends highlight how the industry balances cost, performance, and sustainability to meet modern manufacturing demands.
General plastics injection molding remains a cornerstone of modern manufacturing due to its cost-effectiveness, versatility, and high production efficiency. By selecting appropriate materials and optimizing cavity design, manufacturers can ensure consistent polymer viscosity, precise melt flow index, and reliable plastic cycle optimization.
Effective use of hot runner systems or cold runner molds, along with proper mold release agents, helps achieve efficient part ejection and high-quality cosmetic plastic finishing. Controlling process parameters enables both thin-wall molding and thick-wall molding while maintaining dimensional accuracy and structural integrity.
This process supports the production of a wide range of products, from household items and consumer electronics to automotive components, packaging, and industrial parts. Integration with plastic welding techniques and careful consideration of plastic part assembly further enhances functionality and durability.
With attention to injection molding troubleshooting, process optimization, and ongoing innovations in thermoplastic elastomers and other materials, general plastics injection molding continues to deliver efficient, scalable, and high-quality solutions. It remains an indispensable method for manufacturers seeking affordability, consistency, and adaptability in modern production.
