Injection molding is use to prepare the materials like plastics or rubbers particles. Here injecting of plastics articles into mold with high Temperature.

Injection molding

Operation sequence: 

1. Mold closes :As the screw begins to forward for injecting.
2. Cavity fills: Screw moves forwards.
3. Cavity is packed :As the screw moves continuously forward.
4. Cavity,s cools : AS to screw begins to retract.
5. Mold open’s : for ejection.
6. Mold closes : Next cycle begins.
7. Feed section : Transports material from hopper to heated portion of barrel.
8. Compression section : Plastic granules are compressed to Homogeneous melts.
9. Metering section :The final mix and heating of material into homogeneous melt carried  out in metering section.

Parts of mold:

Two cavity injection mold:

• CAVITY INSERTS : External form of component is made on the cavity
• CORE INSERT : Internal form of component made on the core.
• GUIDE BUSH AND PILLAR:Used for Align two halves and guide pillar are fitted on cavity plate.

• Guide bush are fitted on the  core plate.
• Used as a 4 sets in a mold.

• CAVITY PLATE : Stationary part of mold .

• Holds cavity inserts guide pillar and Sprue bush.

• CORE PLATE :

• Part of movable  part of mold.
•  Holds core insert,Guide bush and supports ejector pins sprue puller and return pins.

• SPRUE BUSH :

• Transports the material form machine nozzle to cavity through runner and Gate.
• Has a tapered conical shaped hole.

• REGISTER RING: 

• Fitted on the top plate and its purpose is to align machine nozzle and spur bush.

• TOP PLATE :

• Plate holds all stationary parts of mold to the fixed pattern of machine.
• It holds directly or In directly cavity plate,Register ring,Guide pillar and Cavity insert.

• BOTTOM PLATE :

• It holds a movable parts of mold to the movable patten of the machine.
• Holds directly or in directly all the movable part of the mold.

• SUPPORT PLATE :

• Mounted behind the core plate to keep this plate from bending under high pressure during injection.

• SUPPORT BLOCK:

• Sandwiched between support plate and bottom plate  to form a space.
• Which allows ejection system to function for the ejection of molded.

Few more parts of mold:

• EJECTOR RETAINER PLATE :  

• Holds the return pins,ejector pins and Sprue puller.
• Clamped together with ejector back plate to form a unit.

• EJECTOR BACK PLATE:

• Clamped together with ejector retainer plate to form a unit.
• To act as a backup  plate  for the pins mounted in ejector retainer plate.

• EJECTOR ROD :

• Mounted with Threads on the ejector back plate and is guided in ejector rod bush.
• Trans’mitts the knockout of the ejector assembly to function.

• ROD BUSH :

• Mounted on bottom plate and act’s  guide to ejector rod.

• PUSH BACK  PINS :

• Push the ejector assembly to its rear position as the mold is closed.
• mold used in injection molding.
• Machine having Hydraulic actuating system do no require this.

• SPRUE PULLER :

• When the molds open its positively pulls the sprue from sprue bush.
• Common pulling method is an a undercut recess situated directly opposite to bush.