Injection machine are also known as injection molding machine. It is main molding equipment for making thermoplastics or thermosetting plastics into plastic products of various shapes using plastic moulding dies.
There are many types and specifications of injection machine, and their classification methods are not uniformly defined. General classification methods are as follows.

Sorting injection machine according to their processing capacity is the most commonly used method in classification of injection machine. Processing capacity of an injection machine refers to clamping force of injection machine and amount of raw materials injected at one time. According to processing capacity, injection machine can be divided into following types:
(1) Ultra-small injection machine. Clamping force is less than 160kN, and theoretical injection melt volume is less than 16cm3.
(2) Clamping force of small injection machine is between 160-2000kN, and theoretical melt volume of one injection is between 16-630cm3.
(3) Clamping force of medium-sized injection machine is between 2000-4000 kN, and theoretical melt volume of one injection is between 800 and 3150 cm3.
(4) Clamping force of large injection machine is between 4000-12500kN, and theoretical melt volume of one injection is between 4000-1000cm3.
(5) Clamping force of super-large injection machine is greater than 12500kN, and theoretical theoretical melt volume is greater than 16000cm3.

Plunger injection machine uses plunger to sequentially push plastic falling into barrel into plasticizing chamber at the front of barrel. In plasticizing room, plastic is plasticized into a molten state by heat provided by peripheral heater of barrel, then molten material is injected into mold cavity through plunger's rapid forward movement and cooled to form. FIG. 1 is a schematic structural diagram of a plunger injection machine.

 

Description: 1-nozzle; 2-heater; 3-dividing shuttle; 4-metering device; 5-hopper; 6-plunger; 7-injection hydraulic cylinder; 8-injection piston.

Figure 1 Schematic diagram of plunger injection machine

In screw injection machine, plastic is softened and melted under combined effect of frictional heat generated by external heating of barrel and extrusion, shearing of plastic when screw rotates, thereby achieving purpose of plasticizing. Then it reciprocates axially through screw, injects plasticized material into mold cavity like a plunger and cools it down. Structure of reciprocating screw injection machine is shown in Figure 2. At present, this type of structure has the most applications for injection machines.

 

Description: 1-nozzle; 2-barrel; 3-screw; 4-hopper; 5-gearbox; 6-motor; 7-hydraulic cylinder

Figure 2 Schematic diagram of structure of reciprocating screw injection machine

Mold clamping device and injection device of vertical injection machine are on same vertical center line, and mold is opened in a vertical direction, as shown in FIG. 3. Advantage is that floor space is small, it is easy to place inserts, mold is convenient to load and unload, and material falling from hopper can be uniformly plasticized. Disadvantage is that product is not easy to fall automatically after being ejected, and must be removed by hand, which is not easy to achieve automatic operation. Most vertical injection machine are small injection machines, large and medium-sized machines should not be used. It is mainly used to produce multi-insert products with injection volume below 60cm3.

 

Description: 1-injection system; 2-clamping system; 3-body.

Figure 3 Vertical injection machine

Mold clamping device and injection device of horizontal injection machine are on same horizontal centerline, mold is opened in horizontal direction, as shown in FIG. 4. Its characteristics are: low body, easy to operate and maintain; low center of gravity of machine, relatively stable installation; after product is ejected, it can be automatically dropped by gravity, which is easy to achieve full automatic operation. At present, most injection machines on the market use this form.

 

Description: 1-injection system; 2-clamping system; 3-body.

Figure 4 Horizontal injection machine

Axis of injection device of angle injection machine and mold clamping device are arranged perpendicular to each other. During injection, melt enters cavity from mold parting surface, as shown in FIG. This type of injection machine is particularly suitable for flat products where gate marks are not allowed on machining center. It occupies a smaller area than a horizontal injection machine, but insert placed in mold is easy to fall down. This type of injection machine is mostly a small injection machine, large and medium-sized injection machines generally do not use this form.

 

Description: 1-injection system; 2-clamping system; 3-body.

Figure 5 Angle injection machine

Multi-mode injection machine is a special injection machine with multi-station operation. Characteristic is that mold clamping device adopts a turntable structure, and mold rotates around rotation axis, as shown in FIG. 6. This type of injection machine fully utilizes plasticizing ability of injection device, which can shorten production cycle and improve production capacity of machine. Therefore, it is especially suitable for production of large quantities of plastic products with long cooling and setting time, or requiring more auxiliary time due to placement of inserts. However, due to large and complex clamping system, clamping force of clamping device is often small, so this injection machine is mostly used for production of plastic soles and other products.

 

Description: 1-injection system; 2-clamping system; 3-another combination mold system; 4-five-combination mold system position allocation; 5- fuselage.

Figure 6 Multi-mode injection machine

According to characteristics of injection mold clamping system, it can be divided into three types: mechanical, hydraulic and hydraulic-mechanical.

Injection machine can be divided into automatic operation, semi-automatic operation and manual operation according to operation mode.

With continuous development of new plastic products, new injection processes continue to emerge, scope of application of injection machines is also expanding. At present, there are mainly thermoplastic general-purpose injection machines, thermosetting plastic injection machines, exhaust injection machines, plastic shoe injection machines, multi-color injection machines, precision injection machines, high-speed injection machines, and foam injection machines.