Automated manufacturing process of ball-pen by injection molding.

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Information about Automated manufacturing process of ball-pen by injection molding.
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Published on March 6, 2014

Author: danialme089

Source: slideshare.net

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) P.E Project by ME-75, 89,102,104,105 1

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 P.E Project by ME-75, 89,102,104,105 2

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 P.E Project by ME-75, 89,102,104,105 3

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. P.E Project by ME-75, 89,102,104,105 4

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 P.E Project by ME-75, 89,102,104,105 5

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 P.E Project by ME-75, 89,102,104,105 6

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. P.E Project by ME-75, 89,102,104,105 7

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 P.E Project by ME-75, 89,102,104,105 8

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 P.E Project by ME-75, 89,102,104,105 9

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 P.E Project by ME-75, 89,102,104,105 10

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. P.E Project by ME-75, 89,102,104,105 11

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 P.E Project by ME-75, 89,102,104,105 12 1

Views: MOLD: Isometric view front view P.E Project by ME-75, 89,102,104,105 13

Top view P.E Project by ME-75, 89,102,104,105 14

PEN: P.E Project by ME-75, 89,102,104,105 15

Isometric Front P.E Project by ME-75, 89,102,104,105 16

Top Side P.E Project by ME-75, 89,102,104,105 17

Clutch: Isometric Front P.E Project by ME-75, 89,102,104,105 18

Top Side P.E Project by ME-75, 89,102,104,105 19

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