Polymer Technology

The main parts in Injection molding machine are:

1. INJECTION UNIT
2. CLAMPING UNIT
3. MOLD SYSTEM
4. CONTROL SYSTEM
5. HYDRAULIC SYSTEM

I. INJECTION UNIT

Parts which are belonging to injection unit are:

• Screw
• Check valve
• Cylinder (barrel)
• Heating Zones
• Nozzle

Tasks of the injection units are:

• Feeding of materials
• Transport of material
• Melting and plastification of granulates
• Homogenization of melted material
• Injection of melted material
• Compacting of injected material

Screw

• Task of screw:
• Feeding of granule
• Transport of material
• Plastification of granule
• Homogenization of melted material

Construction of a standard screw:

• Material of screw: nitride steel
• Roughness of screw surface Rt < 1 um
• L/D ratio -20
• 3 zones (feeding-, compression- and metering zone)

Check valve:
Function of check valve: to prevent the melting materials in front of barrel go back into feeding zone during injection

Heating zone

• Melting of plastic material
• Control of mass temperature
• Max. temperature < 500 C
• 4 heating zones ( 3 cylinder zones, 1 nozzle zone)

Nozzle
Type of nozzle:

• Open nozzle
• Shut-off nozzle (needle shut off nozzle, moved by spring, moved by hydraulic, slide shut off nozzle)

II   CLAMPING UNIT

Task of clamping unit:

• Fixing and guiding the mold
• Keeping the clamping force
• Ejecting the molded part

III MOLD SYSTEM

Mold system consist of:

• Runner system
• Cavity (forming the molded part)
• Cooling system
• Demolding of part for complex geometry
• Ejector system

Runner system
Types of runner system are:

• Cold runner: Bar sprue, pin gate, film gate
• Hot runner
• Insulating runner

Cavity
Task of cavity are:

• Forms geometry of plastic part
• Responsible for surface quality
• Equalizes the material shrinkage

Cooling systems
The significant parameter for cooling system are:

• Cooling channel (geometry and location)
• Cooling media
• Cooling time
• Cooling rate

Ejector systems
Ejector system consists of:

• Ejector pin
• Ejector plates