Injection Molding (Part-1)
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Injection Molding: It is a major
processing technique used to convert
thermoplastic polymeric material into
product by means of cyclic process,
where heated molten polymer injected
into close mold, gives the desired
shape. Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Injection Molding: Broadly injecting
molding machine divided into two half;
1. Injection Unit
2. Clamping Unit
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Parts of Injection Molding Machine
Clamping motor
drive Tie Bar
Barrel
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Hopper: A large container into which raw
polymers is poured , through its open bottom
which allows material to feed into the barrel.
Barrel: Long metallic cylinder which contains
reciprocating screw, helps the mechanism for
heating by shearing and injecting the material
into mold. Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Heater
Heaters are placed around the outside
circumference of the heating barrel used to
heated raw polymer into melt for plasticization.
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Types of heater used in injection molding
Band Heater Automatic Band Heater
Generally used at cylindrical parts.
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
There are three main types of band heaters:
Mica: mica, any of a group of hydrous potassium, aluminum
layered silicate minerals. Mostly used
Ceramic is any of the various hard, brittle, heat-resistant
and corrosion-resistant materials made by shaping and then
firing an inorganic, nonmetallic material, such as clay, at a
high temperature. Common examples
are earthenware, porcelain, and brick. (earlier used)
Mineral Based
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
cartridge heater
(immersion heaters)
Used to heat mold and their platen
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Coil heater (tubular heater)
Prepared By: Rikarani R Choudhury, CIPET,
Provide heats to nozzles, so called as nozzle heater.
BBSR
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Strip heaters
Prepared By: Rikarani R Choudhury, CIPET,
BBSR Also used at cylindrical area.
Cloth heating jackets
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Barrel / screw: band heater, strip heater and cloth heating jackets.
Nozzle: Coil heater
Mold: Catridge heater
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Screw
It is a mechanical device (helical flighted shaft)
which convey the heat melted material.
or
A helical flighted, metal shaft which rotates
within the heating cylinder of a molding
machine for shearing, blending and advancing
Prepared By: Rikarani R Choudhury, CIPET,
the plastic materials. BBSR
The screw which is used in injection molding is
known as reciprocating screw because
eccentric distance increases from rear end to
front end.
Center line
Screw
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Flight
The helical blades which are attached with shaft is
known as flight.
flight flight flight
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Pitch
The distance between two flight is known as pitch.
pitch pitch
pitch
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Land
Height between flight and shaft is known as land.
Land
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Helix Angle (θ)
The angle at which flight is fixed to a shaft is known as
helix angle (the angle between the flight and the
direction perpendicular to the screw axis).
θ θ θ
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
Spline bearing
Shank Length Flight Length (nominal length)
Overall Length
Flight length is also known as nominal length.
Prepared By: Rikarani R Choudhury, CIPET,
BBSR
