Mookuthi is an artisanal nose ornament brand based in Madras.
Manufacturing Piano BallPoint Pen Using Injection Molding
1. Production Engineering Project Report
Manufacturing of Piano BallPoint pen (with Clutch) by using Injection Molding
Class
-
Mechanical (S.E)
Section
-
B
Batch
-
2011-2012
Group members
1- Syed Wajahat Hasan
(ME-075)
2- Danial Sohail
(ME-089)
3- Syed Osaid Ul Haq
(ME-102)
4- Ranjeet Kumar
(ME-104)
5- Owais Ali
(ME-105)
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2. Index
S No.
Contents
Page Number
1
Injection Molding
03
2
Formation of Pen by Injection Molding
05
3
Cleaning and Finishing Process
06
4
Pen Assembly
07
5
Quality Control
07
6
Recommendation of Process
08
7
Materials Used
08
8
Overall Cost
10
9
Bill of Material (BOM)
12
10
Mold Views
13
11
Pen Image
15
12
Pen Views
16
13
Clutch Views
18
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3. INJECTION MOLDING
Injection molding is a common process used for high volume production of
thermo plastic resin parts. A wide variety of products are manufactured using
injection molding, which vary greatly in their size, complexity, and application.
The injection molding process requires the use of an injection molding machine,
raw plastic material, and a mold. It is a manufacturing process for producing parts
by injecting material into a mold. Material for the part is fed into a heated barrel,
mixed, and forced into a mold cavity where it cools and hardens to the
configuration of the cavity. Its typical cycle time ranges between 1 and 60 sec. A
single mold may contain multiple cavities (when the parts produced are smaller in
size) so that multiple parts are produced during each cycle. The mold is expensive
and it is mostly used for mass production.
Injection molding machine
An injection molding machine has two parts. They are:
1) Injection unit
2) Clamping unit
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4. 1. Injection unit:
The injection unit consists of a hopper used for feeding plastic granules into the
barrel. The barrel has heaters or heating jackets on the outside to melt the
material as it flows from one end of the screw to the other. The heating jackets
maintain a temperature of about 400-600 Fahrenheit or 200-300 centigrade. If
the material being used is thermo plastic instead of thermo setting then plastic
pellets must be preheated because once they solidify, their molecular property
changes. On the inside of barrel there is screw which has threads on its outer
surface. This screw is connected to a motor which rotates the screw. It is used for
mixing the melted material and it also acts as a plunger which moves forward to
inject the material into the plastic mold. There is a non-returning valve at the
forward end of the screw which prevents the molten material from returning
during the injecting process. It is also known as reciprocating screw. This screw
also maintains a pressure of ranging from 35Mpa to 140Mpa.
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5. 2. Clamping unit:
The clamping unit consists of 4 plates. These plates are usually made up of metal
and their melting point is higher than the melting point of plastic . One plate is
fixed and the others are movable so that the mold can be closed or opened. It
holds the segments of the mold in proper alignment. The mold is kept closed
during injecting process and opened when the part is cooled. The clamping unit is
attached to a mechanism of hydraulics which close the plates with a certain
pressure so the plates do not open during injection of the material with high
pressure. Cooling channels are provided so that material is cooled and cycle time
is reduced.
Formation of pen by Injection molding process
Initially the mold of piano pen is closed and raw material is fed by means of
hopper. It then enters the barrel and reciprocating screw pushes the material
forward and it is heated by means of heating jackets. The material is superheated
and mixed together to make sure that the plastic is fluid enough to fill each cavity
of the mold. When the material is brought to the right temperature, it is pushed
through the nozzle into the mold by means of sprue or gates. Sprue directs the
molten material into the mold. Trapped air in the mold can escape through air
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6. vents that are grounded into the parting line of the mold. If the air is not allowed
to escape the molten material will not completely fill the mold. The mold contains
a core which also acts as the ejector pin. Continuous pressure is applied by the
plunger to compensate for the contraction of material during solidification. After
filling the mold completely the material begins to cool down as it comes in
contact with cold surface of the mold. When the part is solidified, the plates are
opened and the ejector pin (core) is retracted and the finished material is
separated from the core. Meanwhile the Non returning valve is retracted and
fresh charge is introduced into forward end of the barrel. After the part is
removed from the mold, the plates are closed again and the whole process is
repeated.
Cleaning and finishing process
After the mold cavity is expended and the pen drops down from the mold, a
worker collects it from there and then cleaning and finishing process begins
Initial Cleaning:
As the part is removed from the mold by means of an automatic system(i.e part
falls of the mold) and is then collected in container where workers gather them
and sprue and runner are cleaned off from the part by means of profile cutters or
small saws. The extra plastic present on the surface of the body is completely
undesirable and it has to be purged.
The extra part is then further removed by means of a hand file, but since it is time
consuming so it is less desirable, and the manufacturers usually rely on cutting
just by profile cutters.
And as we can predict from the surface of specifically piano ball pen, that they are
not hand filled.
The workers also select random pieces from the pile of pens to find out if any part
has been over filled during injection of material by an error or accident, which
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7. may have caused the refill nib hole to get jammed. In this case, the hole has to be
cleared by using small nails or in some cases small drills.
In some cases injection point also gives of unwanted rough patch, the injection
point of piano pen is located at the back of the pen holder on the body of the pen.
If the point is rough above the tolerance level of the manufacturer the point has
to filed by using small files.
Further processing:
The pen cover is then washed thoroughly to enhance the shinning of the piece
and is then send to bath in a special plastic polishing material, in order to enhance
the transparency and glossy look of the cover.
The name of manufacturer (Piano) is then painted on the holder of the pen by
using special stamps and is the piece is then left undisturbed for a while for drying
so the name of piano becomes permanent.
Assembly:
The pen is then fully assembled and ink refill, spring along with clutch is then
added into the body of the pen. The pen is then passed through a Quality Control
Unit where the requirements of manufacturer or company are tested on their
desired scale.
Quality Control:
The Quality Control unit is active during every part of the process but as pen is
being formed in bulk quantity the manufacturer cannot check individually each
pen. The main task of the QC is to sort out the defected pieces which may have
arrived during the injection process due to human error, voltage change,
difference in humidity etc. The selected pieces undergo special treatment and
then brought them back to the chain.
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8. The QC is active mostly during the last phase of the process when the pen is fully
assembled. The workers randomly select the pieces .The selected piece is then
measured thoroughly in all dimensions to make sure that the piece is up to the
manufacturer’s design.
Although we don’t know much about the quality department of Piano pen
manufacturer but we can say by observations that they are more prone to errors
as compared to that of a foreign manufacturer.
Why use injection molding?
For producing piano ball pen, injection molding is recommended because of the
following reasons
1) Multiple pens can be produced in a single cycle.
2) Complex parts can be easily produced
3) Cycle time is less
4) Economical process for mass production
Materials used for making pen
Plastic granules are used for making the shells of the pens. Following are the
materials that are most commonly used for making the body of pen:
Polypropylene (PP): This polymer is hard, tough and easily moldable. It is mostly
used in the barrels of use - and - throw models. A random copolymer PP is also
used in the barrel of Ocean Gel Pen model because of its transparency.
High Density Polyethylene (HDPE): HDPE is used for making mostly caps, plugs
and adopters of ball pens of various models. This polymer is useful in those areas,
where flexibility and strength both are equally needed.
Polystyrene (PS): Polystyrene is a very versatile plastic that can be rigid or
foamed. General-purpose polystyrene is clear, hard and brittle. It has a relatively
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9. low melting point. This is suitable for injection molding applications. This material
is used for making transparent barrels for many models of ball pens.
Styrene Acrylonitrile Copolymer (SAN): This material is used for making
transparent barrels of expensive pen for its greater strength and clarity.
Poly Acetal: This is a novel material because of its toughness and huge
compressive strength. It is mostly used for the mechanism of the Pen.
ABS (Acrylonitrile Butadiene Styrene): This is a terpolymer(a polymer made from
the mixture of three polymers) and useful for its toughness and lower density
among all engineering plastic materials. It is mostly used for making clips, plugs
and knobs for many models. It is an excellent choice for the electroplating
application in different parts of ball pen.
TPE (Thermoplastic Elastomer): It is a material that combines the properties of
elastomers and thermoplastics. Elastomers are rubbers that can stretch easily.
Thermoplastics can be molded easily with heat. It is used in the Grips of many
models. It provides a better comfort in writing.
Polycarbonate (PC): This is the toughest of all transparent plastic materials. Due
to the hard and tough nature it is mostly used in the transparent caps of many
models, where the locking mechanism lasts long even after repeated opening
and closing of caps.
Masterbatches: These are color concentrates and available in the form of
granules. Colour pigments are mixed up with a high flow polymer vehicle,
normally LDPE or EVA and now-a-days colour masterbatches are made to be used
as colourant and accordingly it takes an important role in making coloured plastic
parts
Some other materials include
Bakelite: an early plastic (phenolic resin to be exact) used by a few pen
manufacturers (like Parker). Colors were limited (typically red, yellow or dark
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10. brown) and tended to darken over time. Celluloid offered more color variety and
became the plastic of choice for pens.
Black Hard Rubber: a compound produced by mixing crude rubber with sulfur at
high temperatures. Carbon black was used to dye it and give it higher tensile
strength. It was the preferred material for fountain pen caps and barrels until
plastics became popular during the 1920's. Also called ebonite or vulcanite.
Platinum: an especially beautiful celluloid in charcoal gray with luminous silver
gray 'grained' highlights. Used in the 1930's by European manufacturers like
Montblanc and OMAS.
Overall cost
The overall cost of the material is divided into three subgroups. They are:
1) Material cost
2) Production cost
3) Tooling cost
1. Material cost:
The material cost is determined by the weight of the final part that is required.
The weight of the material depends upon the density of material and size of the
material. It also depends upon the thickness of material. If the final part is thick
and larger in size then it material cost is increased.
2. Production cost:
The production cost of a material is calculated from the hourly rate and the time
in which the part is produced. The hourly rate depends upon the size of the
injection machine being used. The design of the machine affects the production
cost. Injection machines are chosen on the basis of clamping force they provide.
The clamping is determined by the projected area of the part and the pressure
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11. with which the material is injected. If the required part is larger in size then the
clamping force would be greater which increases the size of machine and
production cost. The size of machine also depends upon the material that is being
used. If the material used is thermo setting plastic then more temperature and
pressure is required to eliminate the problems that are encountered with thermo
setting i.e. once they cool, their molecular structure changes. That is the reason
they require higher temperature.
The production cost also depends upon the cycle time. Cycle time includes the
injection time, time taken by the molten material to solidify and resetting time. By
reducing the cycle time the production cost can be reduced. A larger part
increases the production cost.
3. Tooling cost:
The tooling cost depends upon the cost of the mold. If large parts are being
produced then the size of the mold is increased which in turn increases the
tooling cost. The numbers of parts produced also contribute to the tooling cost. A
large production quantity will require a higher class of mold that does not wear
easily.
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12. Bill of Material:
S no Part number
Part name
Part size
1
injection mold
Quantity
Height = 40 mm
5050-IM
Length = 40 mm
1
Breadth = 177 mm
2
5050-MML
Main Mold(Left)
Height = 30 mm
Length = 126 mm
1
Breadth = 23 mm
3
5050-MMR
Main Mold(Right)
Height = 30 mm
Length = 126 mm
1
Breadth = 23 mm
4
5050-SM
Support Mold
Height = 49 mm
Length = 32.5 mm
1
Breadth = 154 mm
5
5050-CR
Core
Length = 126 mm
Dia = 8.5 mm
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