This document provides an overview of injection molding. It discusses the injection molding process, materials used, system components including the injection unit, clamp unit and mold. It describes the working of injection molding including the molding cycle of injection, cooling and ejection. It outlines the advantages of high production rates and dimensional tolerances but also limitations of high equipment costs. It concludes with references for further reading on injection molding technology fundamentals and plastics processing.

1. PRESENTED BY
GAUTAM KUMAR
MTECH 1ST YEAR (14RT60R07)
RUBBER TECHNOLOGY

2.  INTRODUCTION
 INJECTION MOLDING MATERIALS
 INJECTION MOLDING SYSTEM
 WORKING OF INJECTION MOLDING
 SCREW AND MOLD DESIGN
 THE MOLDING CYCLE
 ADVANTAGE & LIMITATION OF INJECTION
MOLDING
 REFERENCES

3.  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.

4.  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

6. Components of injection molding system:
1. injection unit
2. clamp unit
3. mold

7.  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.

8.  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)

9. 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

12. 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.

13.  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

14.  Stages of injection molding:
1. injection or filling
2. cooling
3. ejection and resetting

16.  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.

17.  Mold costs are high.
 Molding machinery and auxiliary equipment
costs are high.
 Lack of knowledge about the fundamentals of
the process causes problems.

18.  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