Packaging Assignment

8/10/2019 Packaging Assignment

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1) The Blown Film Process:-

One way of producing plastic film (flexible packaging films) is by a process called "blown film".

(Another method is calendering)The blown film process consists of injecting molten plastic into a

blow film machine and blowing air through the molten plastic. This creates a bubble in the molten

plastic, just like a person blowing a bubble in chewing gum. The bubble is blown vertically, creating a

long bubble like a party balloon.Air is blown onto the outside of the balloon from a cooling ring at

the base of the balloon. The air blown onto the outside, together with the air blown inside the

balloon chills the balloon as the air rises. This cooling effect solidifies the plastic, creating the plastic

film that we see used in carrier bags etc.

The top of the balloon is guided between rollers and then pinched to flattened the balloon.The

flattened balloon is guided on rollers to where it is wound onto a reel. The flattened balloon of

plastic is called "lay-flat tube". Lay-flat tube can be heat sealed and perforated to make plastic bags,

or it can be slit to form sheets of plastic.

Polyethylene (polythene) is the most common plastic used in blown film production. Low density

polyethylene and high density polyethylene are suitable for blown film production but other

materials such as polypropylene (PP) and Polyamide/Nylon (PA) are sometimes blended with

polyethylene or used to produce multi layered laminates.


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2) Injection Moulding Process:-

Injection moulding is a widely used process in manufacturing. It is a quick way of producing large

numbers of identical components such as plastic trays and safety helmets. Most thermoplastics can

be injection moulded, including, Nylon (PA), Polycarbonate (PC), Polypropylene, (PP), Polystyrene

(GPPS) and Acrylonitrile-Butadiene-Styrene (ABS).

2.1) Equipment:-

Injection molding machines consist of a material hopper, an injection ram or screw-type plunger,

and a heating unit.Also known as presses, they hold the molds in which the components are shaped.

Presses are rated by tonnage, which expresses the amount of clamping force that the machine can

exert. This force keeps the mold closed during the injection process. Tonnage can vary from less than

5 tons to over 9,000 tons, with the higher figures used in comparatively few manufacturing

operations. The total clamp force needed is determined by the projected area of the part being

molded. This projected area is multiplied by a clamp force of from 1.8 to 7.2 tonsfor each square

centimeter of the projected areas. As a rule of thumb, 4 or 5 tons/in2can be used for most products.

If the plastic material is very stiff, it will require more injection pressure to fill the mold, and thus

more clamp tonnage to hold the mold closed.The required force can also be determined by the

material used and the size of the part; larger parts require higher clamping force.

2.2) Mold Design :-

Moldordieare the common terms used to describe the tool used to produce plastic parts in

molding.

Since molds have been expensive to manufacture, they were usually only used in mass production

where thousands of parts were being produced. Typical molds are constructed from hardened steel,

pre-hardened steel, aluminum, and/orberyllium-copperalloy. The choice of material to build a mold

from is primarily one of economics; in general, steel molds cost more to construct, but their longer

lifespan will offset the higher initial cost over a higher number of parts made before wearing out.Pre-hardened steel molds are less wear-resistant and are used for lower volume requirements or

larger components; their typical steel hardness is 3845 on theRockwell-C scale.Hardened steel

molds are heat treated after machining; these are by far the superior in terms of wear resistance and

lifespan. Typical hardness ranges between 50 and 60 Rockwell-C (HRC). Aluminum molds can cost

substantially less, and when designed and machined with modern computerized equipment can be

economical for molding tens or even hundreds of thousands of parts. Beryllium copper is used in

areas of the mold that require fast heat removal or areas that see the most shear heat generated.

The molds can be manufactured either by CNC machining or by usingelectrical discharge

machiningprocesses.
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3) Thermoforming:-

Thermoformingis a manufacturing process where a plastic sheet is heated to a pliable forming

temperature, formed to a specific shape in a mold, and trimmed to create a usable product. The

sheet, or "film" when referring to thinner gauges and certain material types, is heated in an oven toa high-enough temperature that it can be stretched into or onto a mold and cooled to a finished

shape.

In its simplest form, a small tabletop or lab size machine can be used to heat small cut sections of

plastic sheet and stretch it over a mold using vacuum. This method is often used for sample and

prototype parts. In complex and high-volume applications, very large production machines are

utilized to heat and form the plastic sheet and trim the formed parts from the sheet in a continuous

high-speed process, and can produce many thousands of finished parts per hour depending on the

machine and mold size and the size of the parts being formed.


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Thermoforming

3.1) Process:-

In the most common method of high-volume, continuous thermoforming of thin-gauge products,

plastic sheet is fed from a roll or from an extruder into a set of indexing chains that incorporate pins,

or spikes, that pierce the sheet and transport it through an oven for heating to forming temperature.

The heated sheet then indexes into a form station where a mating mold and pressure-box close on

the sheet, with vacuum then applied to remove trapped air and to pull the material into or onto themold along with pressurized air to form the plastic to the detailed shape of the mold. (Plug-assists

are typically used in addition to vacuum in the case of taller, deeper-draw formed parts in order to

provide the needed material distribution and thicknesses in the finished parts.) After a short form

cycle, a burst of reverse air pressure is actuated from the vacuum side of the mold as the form

tooling opens, commonly referred to as air-eject, to break the vacuum and assist the formed parts

off of, or out of, the mold. A stripper plate may also be utilized on the mold as it opens for ejection

of more detailed parts or those with negative-draft, undercut areas. The sheet containing the

formed parts then indexes into a trim station on the same machine, where a die cuts the parts from

the remaining sheet web, or indexes into a separate trim press where the formed parts are trimmed.

The sheet web remaining after the formed parts are trimmed is typically wound onto a take-up reel

or fed into an inline granulator for recycling.

3.2) Mold Design:-

Cast aluminum Molds-Cast aluminum molds are cast at a foundry and typically have

temperature control lines running through them. This helps to regulate the heat of the

plastic being formed as well as speed up the production process. Aluminum molds can be

male or female in nature and can also be used in pressure forming applications. The main

drawback with this type of mold is cost.


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Machined aluminum Molds - Machined aluminum molds are like cast aluminum except they

are cut out of a solid block of aluminum using a CNC machine and some sort of CAD

program. Typically machined aluminum is used for shallow draw parts out of thin gauge

material. Applications may include packaging as well as trays. Again, cost is a significant

factor with this type of tooling.

Composite material|Composite Molds - Composite molds are a lower cost alternative to cast

or machined aluminum molds. Composite molds are typically made from filled resins that

start as a liquid and harden with time. Depending on the application, composite molds last a

relatively long time producing high quality parts. Within the category of composite molds,

the subset of "Ceramic" molds has consistently proven to be the most durable. While not

temperature controlled, these molds can run nearly as fast as Cast or Machined aluminum,

yet at a substantially lower price point. Suitable for all but the highest volume production

and strictest tolerances.

Thin-gauge thermoforming is primarily the manufacture of disposable cups, containers, lids, trays,

blisters, clamshells, and other products for the food, medical, and general retail industries. Thick-

gauge thermoforming includes parts as diverse as vehicle door and dash panels, refrigerator liners,

utility vehicle beds, and plastic pallets, blister packaging films.

Thermoforming PEEK-based APTIV film

APTIV film provides a key advantage over thermoset films: it can be shaped into a variety of parts

using thermoforming processes. The thermoformer can start with either the amorphous or

crystalline grades of APTIV film and use the appropriate process conditions to shape the part. Parts

ranging from a thickness of 6 microns up to 600 microns have been thermoformed, and thicker parts

are also possible.

Slitting PEEK-based APTIV film

APTIV film rolls can be slit into custom widths to suit the needs of end users. Victrex has

incorporated a state-of-the-art slitter rewinder into the APTIV film production facility to provide

customers with slit widths down to 45 mm. Customers can also use their own in-house slitting

equipment or local convertors for such operations.

4) vacuum forming:-It is a simplified version of

thermoforming, whereby a sheet of plastic is heated to a forming

temperature, stretched onto or into a single-surface mold, and held against the mold by applying

vacuum between the mold surface and the sheet. The vacuum forming process can be used to make

most product packaging, speaker casings and even car dashboards.

Normally, draft angles must be present in the design on the mold (a recommended minimum of 3),

otherwise release of the formed plastic and the mold is very difficult.

Vacuum forming is usually - but not always - restricted to forming plastic parts that are rathershallow in depth. A thin sheet is formed into rigid cavities for unit doses of pharmaceuticals and for


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loose objects that are carded or presented as point-of-purchase items. Thick sheet is formed into

permanent objects such as turnpike signs and protective covers.

Relatively deep parts can be formed if the form-able sheet is mechanically or pneumatically

stretched prior to bringing it in contact with the mold surface and before vacuum is applied.

Suitable materials for use in vacuum forming are conventionally thermoplastics, the most common

and easiest being High Impact Polystyrene Sheeting (HIPS). This is molded around a wood, structural

foam or cast/machined aluminum mold and can form to almost any shape. Vacuum forming is also

appropriate for transparent materials such as acrylic which are widely used in applications for

aerospace such as passenger cabin window canopies for military fixed wing aircraft and "bubbles"

for rotary wing aircraft ex. DuPont Teflon PFA film.

5)Compression molding:-

compression molding is one form of low-moisture processing method used to make EFC (edible films

and coatings).

Thermoplastic material which softens when heated, is placed on one half of a mold. Heat and

pressure are applied to the mold once it is closed. Film material then fills the mold cavity and

polymerization accurs. The film is then, obtained by cooling the mold. The flowability of the film-

forming material for compression molding can be low, while for extrusion the material needs to

have high flowability. Because compression molding has very limited production amount, it is

economical for small production. Compression molding was used recently as one of the methods to

make EFC. Foulk and bunn showed that films showed that SPI films could be produced bycompression molding. Films were made according to the method developed by poly-med inc.

Mechanical and barrier properties of the SPI films that have various solubility were significantly

different. They concluded that compression molded acetylated SPI films could be used as

commercial thermoplastic. Slightly yellow and transparent SPI films plasticized with ethylene

glycol(EG) formed by compression molding under pressure of 15 Mpa at 150C Was Developed due

to physical crosslinking between chains induced by EG water adsorbtion of SPI films was reduced. SPI

films made by compression molding has improved TS, breaking elongation, water resistance and

thermostability and therefore, they suggested that the thermoplastic material from SPI could be

used commercially for food packaging.

Materials may be loaded into the mold either in the form of pellets or sheet, or the mold may be

loaded from a plasticating extruder. Materials are heated above their melting points, formed and

cooled. The more evenly the feed material is distributed over the mold surface, the less flow

orientation occurs during the compression stage.

Thermoplastic matrices are commonplace in mass production industries. One significant example

are automotive applications where the leading technologies are long fibre reinforced thermoplastics

(LFT) and glass fiber mat reinforced thermoplastics (GMT).


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In compression molding there are six important considerations that an engineer should bear in mind

Determining the proper amount of material.

Determining the minimum amount of energy required to heat the material.

Determining the minimum time required to heat the material.

Determining the appropriate heating technique.

Predicting the required force, to ensure that shot attains the proper shape.

Designing the mold for rapid cooling after the material has been compressed into the mold.

5.1) Mold design:-

Three types of molds used are the flash plunger-type, straight plunger-type, and the "landed"

plunger-type molds. The flash type mold must have an accurate charge of plastic and produces a

horizontal flash (excess material protruding from the mold). The straight plunger-type mold allows

for some inaccuracy in the charge of plastic and produces a vertical flash. The landed plunger type

mold must have an accurate charge of plastic, and no flash is produced.

Compression molding press


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6) Cast films extrusion:-

The cast film process involves the extrusion of polymers melted through a slot or flat die to form a

thin, molten sheet or film. This film is "pinned" to the surface of a chill roll (typically water-cooled

and chrome-plated) by a blast of air from an air knife or vacuum box. The film quenches immediately

and then has its edges slit prior to winding.

Because of the fast quench capabilities, a cast film generally has much better optics than a blown

film and can be produced at higher line speeds. However, it has the disadvantage of higher scrap due

to edge-trim, and very little film orientation in the cross-direction.

Cast films are used in a variety of markets and applications, including stretch/cling films, personal

care films, bakery films, and high clarity films. Cast film extrusion orients the film in the machine

direction only, producing a large difference in machine and transverse directional properties. Castfilm extrusion has advantages as well. The techniques used in the production of wide width films are

more easily controlled than in the blown film process. Higher take off speeds are possible, which

translates into lower cost per unit weight of film. Cast film extrusion offers better gauge control and

gauge consistency, which are critical for thin films below 1 mil (25 microns). Lastly, optical properties

such as gloss and haze are typically better when produced on cast film equipment. SBC(styrene

butadiene copolymers) can be manufactured into cast films.

6.1) Equipment:-

Film die

Cast film dies should employ coat-hanger designs and be equipped with a restrictor bar and

adjustable flex-lip die opening. Older cast film dies such as T-dies offer many stagnant areas where

polymers can hang-up and degrade, significantly decreasing the quality of the film. A die opening of

3040 mils (0.91.0 mm) is recommended for cast film extrusion with K-ResinSBC. However,

draw resonance may be encountered if the drawdown ratio is too large. If draw resonance is

encountered, decreasing the die opening or line speed may improve processing stability.

Air Knife, Edge Pins & Vacuum Box

To pin the molten web to the chill roll and stabilize the film edges, an air knife may be used to blow a

gentle stream of air on the film at the point where it contacts the chill roll. In addition, edge pins

may be used to reduce the amount of neck in and also help stabilize the film edges. These

techniques are especially useful when producing thin films with large drawdown ratios. A vacuum

box may also be used to stabilize the web during extrusion.


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Air Gap

The air gap is the distance from the die exit to the point where the film contacts the chill roll. This

distance can control drawdown ratio and cooling and shrinkage differences in multilayer films. The

air gap is typically minimized for K-ResinSBC cast film production. Cast film properties can be

altered by adjusting the air gap, however optimization trials are required.

Chill Rolls

The chill rolls may be chrome plated and highly polished; matte finished, or embossed rolls. All rolls

should be individually temperature controlled by a separate heat exchanger capable of maintaining

roll temperatures of 40150F (465C). It is advantageous to use a system which will control the

temperature gradient across the entire roll as closely as possible, preferably within 5F (3C)

maximum variation. The optimum chill roll temperature for K-Resin SBC cast film production will

vary with film structure, output rate and equipment. However, 120180F (4982C) is typically

used for monolayer K-Resin SBC cast film production.

cast film extrusion


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Packaging technology assignment

Topics:

Blown film extrusion

Injection moulding

Thermoforming

Vacuum forming

Compression moulding

Cast film extrusion


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Submitted by

Abhijeet kumar

2k11/ps/001

6 sem (psct)

Documents

Packaging Assignment