Injection Molding Machine Process and Injection Molding Production Line

Injection molding is a vital process for producing plastic products. It involves preparing plastic materials, melting them, injecting the melt into molds, cooling and solidifying, and then ejecting the finished products. Injection molding machines need to meet specific technical requirements, such as having a screw-barrel type, maintaining an injection speed of 110-120 mm/s, and using B-type nitrided screws. The production line construction includes factory design, equipment selection, automation control, and process optimization. Proper layout, efficient equipment, and optimized processes are essential for high-quality production and sustainability.

Injection Molding Machine Process and Injection Molding Production Line Construction

I. Injection Molding Machine Process

Injection molding is a crucial process in the production of plastic products, involving several key steps:

1. Material Preparation:

• Select suitable plastic materials, such as polypropylene (PP), polyethylene (PE), or polycarbonate (PC). Additives like colorants, toughening agents, or anti-static agents may be added based on product requirements.
• Raw materials must undergo strict drying to remove moisture from the granules, preventing bubbles or defects during injection molding.

1. Plasticizing and Injection:

• Plastic granules are fed into the hopper of the injection molding machine via an automatic feeding device and then conveyed into the heating zone of the screw. The granules are gradually melted into a uniform melt by the rotation and heating action of the screw.
• The plastic melt is pushed by the screw and injected into the mold cavity at high pressure and high speed. The injection speed, pressure, and time must be precisely controlled to ensure the mold cavity is completely filled.

1. Pressure Holding Stage:

• After the mold cavity is filled, the machine continues to apply pressure to the melt to prevent shrinkage cavities or dimensional deviations during cooling.

1. Cooling and Solidification:

• The plastic gradually cools and solidifies within the mold cavity. Molds typically use cooling water channels to achieve rapid cooling, with cooling time depending on the thickness of the product and the type of plastic.

1. Mold Opening and Ejection:

• Once cooling is complete, the injection molding machine opens the mold, and the ejection mechanism (such as ejector pins or plates) pushes the product out of the mold cavity.

1. Post-processing:

• Products removed from the mold may require further processing, such as grinding, trimming, drilling, or painting. Some products may undergo annealing after demolding to enhance their strength and toughness.

1. Recycling and Reuse:

• One significant advantage of injection molding is the efficient recycling of scrap and defective products. These waste materials can be ground and reprocessed, reducing production costs.

II. Technical Requirements for Injection Molding Machines

1. Basic Technical Conditions:

• The injection molding machine should be of the screw-barrel type.

1. Injection Speed:

• The injection speed is typically set between 110-120 mm/s.

1. Screw Type:

• B-type nitrided screws are commonly used.

1. Mold Installation and Mold Change:

• The injection molding machine should be equipped with a dedicated magnetic mold base (quick mold change system) for fast and convenient mold changes.

1. Product Surface Quality:

• The product surface should be free from obvious injection molding defects such as burrs, short shots, shrinkage, or weld lines. The color should be uniform, and the appearance should be good.

III. Construction of Injection Molding Production Line

1. Factory Design:

• Injection molding production lines require sufficient space to accommodate various equipment and materials while ensuring safe movement of personnel and emergency exits.
• Injection molding machines should be positioned with adequate safety clearance from surrounding equipment to ensure smooth operation and personnel safety.
• Design sufficient storage space and material handling channels for efficient material management.

1. Equipment Selection and Configuration:

• Choose the appropriate injection molding machine model and specifications based on product requirements, considering factors such as product size, material properties, and production efficiency.
• Select suitable peripheral equipment, such as dryers, hoppers, additive feeders, and hot runner systems, to enhance production efficiency and product quality.
• Based on product processes, choose appropriate auxiliary equipment, such as robotic arms for injection molding, palletizing robots, and vision inspection systems, to achieve automated operations and quality control.

1. Automation Control System:

• Injection molding production lines require a comprehensive automation control system to enable automated machine operation and data collection.
• The control system should include the injection molding machine’s operating interface, PLC controllers, servo drives, and sensors to achieve automated parameter adjustment and real-time monitoring.

1. Process Optimization:

• Optimize the injection molding process to ensure production efficiency and product quality. Adjust parameters such as injection speed, pressure, holding time, and cooling time to reduce production cycle times.

By designing a rational process and constructing an efficient production line, injection molding can achieve high-efficiency and high-quality plastic product manufacturing while meeting environmental and sustainable development requirements.