PRESENTED BY

GAUTAM KUMAR

MTECH 1ST YEAR (14RT60R07)

RUBBER TECHNOLOGY

INTRODUCTION

INJECTION MOLDING MATERIALS

INJECTION MOLDING SYSTEM

WORKING OF INJECTION MOLDING

SCREW AND MOLD DESIGN

THE MOLDING CYCLE

ADVANTAGE & LIMITATION OF INJECTION

MOLDING

REFERENCES

Injection molding is a manufacturing process for

forming objects as of plastic, metals, rubbers by

heating the molding material to a fluid state and

injecting it into a mold.

Polymers that are capable of being brought to a state

of fluidity can be injection molded.

Injection molding is suitable processing method for

following materials:

Thermoplastics

Elastomers

Rubbers

Thermosets

Composites

Components of injection molding system:

1. injection unit

2. clamp unit

3. mold

The injection unit has two functions:

1. to melt pellets or powder

2. to inject the melt into a mold.

Most widely used types of injection units:

1. conventional units: consists of a cylinder and a plunger.

2. reciprocating screw units: a barrel and a screw that rotates to melt & pump the plastic mix from hopper to end of screw and then moves forward to push the melt into mold.

Clamp unit has three functions:

1. open and close mold halves

2. eject the part

3. After closing hold mold with sufficient force to resist melt pressure inside mold as it is filled

Magnitude of initial opening force required depends on:

1. packing pressure

2. Material

3. part geometry (depth and draft)

Functions of a mold:

1. impart the desired shape to the plasticized

polymer

2. cool the molded part

A mold is made up of:

1. the cavities and cores

2. The material used for making mold is either

steel or aluminium

Mold basically consists of two parts:

1. a stationary half (cavity plate)

2. a moving half (core plate)

Parting line: separating line between the two

mold halves

The injected material is transferred through a

central feed channel, called the sprue.

Order data: Part design,quantity,molding material,

tolerance etc.

Molding machine ---number of cavities

Type of mold ----selection of parting surface

Incorporation of feed system (sprue, runner, gate)

Incorporation of ejection system

Alignment of mold

Arrangement for mold lifting & clamping

Shrinkage factor

Stages of injection molding:

1. injection or filling

2. cooling

3. ejection and resetting

Parts can be produced at high production rates.

Parts require little or no finishing.

Close dimensional tolerances can be maintained.

Parts can be molded with metallic and non metallic

inserts.

The inherent properties of the material give many

advantages such as high strength-weight rates,corrosion

resistance.

Mold costs are high.

Molding machinery and auxiliary equipment

costs are high.

Lack of knowledge about the fundamentals of

the process causes problems.

Injection Molding Technology & fundamental-by

James L.white,4th edition,2009,ISBN-978-3446-4185-7

Technical manual on Plastics Processing-by

CIPET,Chennai,1st edition,2007

Technical manual on Plastics Mold design-by

CIPET,Chennai,1st edition,2007