Some knowledge about injection molding


Injection molding is a method of molding industrial products. Products usually use rubber injection molding and plastic injection molding. Injection molding can also be divided into injection molding molding and die casting. Injection molding machine (referred to as injection machine or injection molding machine) is the thermoplastic plastic or thermosetting materials using plastic molding mold into plastic products of various shapes of the main molding equipment, injection molding is achieved by injection molding machine and mold.

1.Main types of

1.Rubber injection molding: Rubber injection molding is a production method of vulcanizing the rubber material directly into the model from the barrel. The advantages of rubber injection molding are: although it is an intermittent operation, but the molding cycle is short, the production efficiency is high, the preparation process of the embryo material is cancelled, the labor intensity is small, and the product quality is excellent.

2.Plastic injection molding: Plastic injection molding is a method of plastic products. The molten plastic is injected into the plastic products mold by pressure, and the cooling molding is used to get all kinds of plastic parts. There are special mechanical injection molding machines for injection molding. At present the most commonly used plastics are polyethylene, polypropylene, ABS, PA, polystyrene and so on.

3.Molding and injection molding: the resulting shape is often the final product and no other processing is required before installation or use as the final product. Many details, such as bumps, ribs, and threads, can be molded in one step by injection molding.

2.Technology foundation

● Purpose, operation and results of temperature, pressure, speed and cooling control
● How does the adjustment of injection molding machine Settings affect the process and quality
● Optimize screw control Settings
● Multi-stage filling and multi-stage pressure holding control; Effects of crystallization, non-crystallization and molecular/fiber alignment on process and quality
● Internal stress, cooling rate, plastic shrinkage on the quality of plastic parts
● Plastic rheological mechanics: how do plastics flow, row and change viscosity, shear and molecular/fiber row relationship
● The relationship between pouring system, cooling system, mold structure and injection molding process

3.Problem analysis and solution

● Injection molding parts around the lack of glue, the reason analysis and solution
● The reason analysis and solution of batch front (rough edge)
● Cause analysis and solution of surface shrinkage and shrinkage hole (vacuum bubble) of injection parts
● silver grain (material flower, spray), burnt, gas grain cause analysis and solutions
● Injection molding parts surface water ripple, flow (flow marks) cause analysis and solutions
● Injection molding parts surface clamp water lines (weld marks), spray lines (snake lines) cause analysis and solutions
● Cause analysis and solution of surface crack (crack) and top white (top explosion) of injection parts
● Injection molding parts surface color difference, poor luster, mixed color, black bar, black spot reason analysis and solutions
● Cause analysis and solution of warping deformation and internal stress cracking of injection parts
● Cause analysis and solution of size deviation of injection parts
● Reason analysis and solution of injection parts sticking mold, drag flower (strain), drag white
● Injection molding parts lack of transparency, lack of strength (brittle) reason analysis and solutions
● Cause analysis and solution of cold material spots and peeling (stratification) on injection parts surface
● Cause analysis and solution of defective metal inserts of injection parts
● Nozzle salivation (runny nose), glue leakage, nozzle drawing, nozzle blockage, mold opening difficulties cause analysis and improvement measures
The use of CAE mold flow analysis technology quickly and effectively solve injection molding field problems

The optimization design
● Injection mold structure, composition, classification and function;
● Gating system (gate, runner, cold well, etc.) optimization design
● Optimized design of cooling system (waterway, water separator, beryllium cylinder, etc.)
● shrinkage rate setting and adjustment
● The relationship between pouring system, cooling system, mold structure and injection molding process
● Mold installation, debugging and maintenance work
● The use of chiller and mold temperature machine to control the process
The use of CAE mold flow analysis technology for mold optimization design

4.Related introduction

Injection molding machine
An injection molding machine (injection molding machine) has two basic parts: an injection device for melting and feeding the plastic into the mold and a mold closing device. The function of the mold closing device is:

1.Make the mold close under the condition of bearing the injection pressure;

2.Take out the product and melt it before the plastic is injected into the mold, and then control the pressure and speed to inject the melt into the mold. There are two types of injection devices in use today: screw preplasticizers or two-stage devices, and reciprocating screws. The screw preplasticizer uses a preplasticized screw (first stage) to inject molten plastic into the feed rod (second stage).

The ADVANTAGES OF screw preplasticiZERS ARE CONSTANT MASS OF MOLTEN MATERIAL, HIGH PRESSURE and HIGH speed, and PRECISE INJECTION volume CONTROL (using mechanical thrust devices at both ends of the piston stroke). These advantages are required for transparent, thin-walled products and high production rates. Disadvantages include uneven residence times (leading to material degradation), higher equipment costs and maintenance costs.
The most commonly used reciprocating screw injection devices do not require a plunger to melt the plastic and inject it.
The types of injection molding machine are: vertical, horizontal and all-electric, but no matter what type of injection molding machine, its basic functions have two:

(1) Heat the plastic until it reaches a melting state;
(2) Apply high pressure to the molten plastic, so that it is injected and filled with the mold cavity.
Ultra-low cost injection molding
① Efficient material engineering:
1, no heat regeneration dehumidification and drying: power saving more than 50%, environmental protection (no renewable gas emissions);
2, screw power cleaning, black spot bad prevention
3, material recycling, foreign matter mixing prevention
② High efficiency and energy saving project:
1, injection molding machine power saving:
2, cylinder electromagnetic heating: power saving 50%+
3, adiabatic coating: coating 3mm, used in any place, power saving 30%+
③ Ultra-short cycle engineering:

Shorten the storage cycle: finished products, semi-finished products, raw materials, defective products, etc
2, forming cycle shortening, pulse cooling molding
④The latest pulse cooling technology and equipment, reduce the mold cooling cycle;
1, molding technology improvement, reduce the molding cycle. Including: mold defect/mold defect improvement, molding process optimization, new mold test and defect improvement, reduce the defect rate in the project;
2, the operation time is shortened, the mold is quickly switched
3, molding engineering improvement, shorten the operation time. Including: automatic/semi-automatic operation, mold rapid switch, manipulator operation, manipulator rapid switch operation, one machine one operation, multiple machine one operation
Copper nut
General situation of
Injection molded copper nuts can also be understood as inlaid copper nuts or embedded copper nuts, in today's market there are different injection molded copper nuts, the purpose is also different.
The principle of
The main use of copper inserts is to inject products into plastic parts, which can be installed to form an effective internal thread. The way of operation is to heat the product and embed it into the plastic parts or directly use the mold injection. Because brass has better thermal conductivity, after heating the copper insert pressed into the plastic matrix can make the product quickly become hot to speed up the work efficiency, heated copper insert can also quickly conduct heat to plastic parts, so that the plastic hole surrounding soft, thus quickly press the product into the hole. If the use of mold injection, the copper insert is hot injection into the plastic parts after the outer diameter of the embossing process, forming and copper insert to form a certain friction and bite force, can make it fixed in the inside so that it can not fall off.
Products are widely used in: mobile phones, portable computers, a variety of plastic shell, communications, micromotors, computers, electrical appliances, electronics, toys, clocks, lighting, locomotives and other industries.
At present, the main types are: CNC computer parts, mobile phone nuts, embossed nuts, hot melt nuts, hot pressing nuts, embedded nuts, ultrasonic nuts, injection nuts, insert nuts, copper shaft, copper column, copper sleeve, copper cup, precision shaft and non-standard screw nuts and other 20 categories, tens of thousands of specifications.
The raw material
Main: environmental copper, H3604 copper, Japan 303 stainless steel, 24C easy car iron, aluminum alloy, Sai steel.