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P1: die casting. Advantages of Die Casting

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P1: describe the moulding
techniques used to manufacture a metal-based product

Die
Casting

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It is a
process where moulds called dies are used to create dies and replicates of
products. It is a popular way for manufacturers to create products as it is an
efficient and cheap long term solution to mass produced products. Another
advantage is that you can cast both low and high melting point metals making it
suitable for many different types of metals which is why it is so popular .This
method requires a furnace, the casting machine itself, the die and the metal.

There are
two types of Die casting:

The first
method of die casting is used for metals with a low melting point using Hot
Chamber machine which requires the melted metal to feed the die. When the piston
on the machine retracts it allow the molten metal to fill the die assembly
which creates the die when it enters the mould. This method is called Hot Die
Casting. The second method of die casting is used for metals with
high melting point which is melted is a furnace separately after which a
specific amount of molten metal is transferred to the cold chamber machine
feeding it to a unheated shot chamber which has a mould which creates a die. This
method is called the cold die casting. 

 

 Advantages
of Die Casting

Die
casting allows a vast range of metals to be used which is why it has so many
advantages. As it allows you to work with many types of metals it also then
allows you to produce work pieces of all sizes making this an advantage as
manufacturers can use this method with all different types of products.  Another advantage is that difficult shapes
within a design can also be made with the end product having a good finish. It
saves a lot of money for the company as little to no waste is produced from the
casting. Even if waste is produced it can be melted and used in the casting
process again giving this method a sustainable approach.

Disadvantages of Die casting

Creating
and designing the mould is a very slow and expensive process as each mould is
made to specific order with different needs and mould each time. Moreover
another problem is that the cast is used only for that specific part and it
cannot be changed once made which is why it is so costly and like a
non-recyclable item.  Another problem
with die casting is that after you have made the die the product will need some
further hardening in order to improve the strength of the product.

 

Sand casting

Sand
casting is a method which is used to create expendable sand moulds as it can
create complex metals parts. A sand mould is created for the mould and the
product to be build which requires the use of a furnace, metal, pattern, and
sand mould which are then destroyed after each cast to take out the product;
this makes this method of casting really expensive. The metal which is going to
be used is melted in a huge furnace and then poured into the cavity of the sand
mould where it goes to the shape the mould is made out of. When the metal in
its liquid form is poured in to the cavity it separates along a parting line
and the solidified casting can be removed.

The
process cycle for sand casting consists of six main stages

Mould-making – The
first step in the sand casting process is to create the mould for the casting. The
mould is created from sand in a pot or other similar thing which makes it
easier for the person to retrieves the cast after the casting.  Clamping –
After
the mould has been made, it must be prepared for the molten metal to be poured.
The whole mould is lubricated well so when the cast is produced it detaches
from the pot easily and creates a smooth cast. Pouring – The
metal which will be poured into the mould is kept at fixed temperature in a
furnace until the mould is securely clamped. After this the molten metal is
poured into the mould at a slow pace so the entire cavity is filled up from the
molten metal.  Cooling – After the molten metal has been poured into the cavity then
it is time for it to cool and solidify once it enters the cavity. Once the
molten metal solidifies then it is time to check if the cast is ready to be
taken out of the mould.  Removal – After
the right time has arrived to take the cast out; then it is time for you to
break the sand mould to retrieve the cast. Trimming –This last
part of the sand casting technique is to cut off all the tunnels to the cast
which supplied the molten metal to the mould. General cleaning of the product might
also be needed.

Sand casting Advantages and
Disadvantages

Advantages

Disadvantages

Ø  Scrap
can be recycled

Ø  High
labour cost

Ø  Many
material options

Ø  Poor
surface finish and tolerance

Ø  Short
lead time possible

Ø  Low
production rate

Ø  Can
produce very large parts

Ø  Poor
material strength

Ø  Can
form complex shapes

Ø  Secondary
machining often required

Ø  Low
tooling and equipment cost

Ø  High
porosity possible

 

 

Investment casting

One
if the oldest casting method of manufacturing process is called investment
casting; it is where molten metal is poured into an expendable ceramic mould
which is created by using wax which is melted out once the molten metal has
taken shape of the cast.  The mould is
surrounded by invested wax and created one mould and one part; this increases
production time and costs relative to other casting processes. However, since
the mould is destroyed during the process, parts with complex geometries and
intricate details can be created. Many different metals like aluminium alloys,
bronze alloys, magnesium alloys, cast iron, stainless steel, and tool steel can
be used with this mould which is why it’s a good method of casting. Similar to
the previous casting investment casting requires the use of a metal die, wax,
ceramic slurry, furnace, molten metal, and any machines needed for
sandblasting, cutting, or grinding.

The
process steps include the following:

Pattern
creation –
The mould is created after wax is injection moulded onto a metal die and is
formed as one piece. Mould
creation –
The mould is dipped into the fine ceramic particles and then dried to form a
ceramic shell around the pattern and gating system of the mould creation. Pouring – The mould
is preheated in a furnace to approximately 1000°C and the molten metal is
poured from a ladle into the gating system of the mould, filling the mould
cavity.Cooling –
When
the mould is filled by the machine; then they let the molten metal to cool down
and solidify to the final shape of the casting which is created using the wax.  Casting
removal –
when the molten has cooled then the mould can be broken and the casting can be
removed to reveal it and see the results. Finishing
– This
part is important not only in this method but all. Finishing operation such as grinding
or sandblasting are used to smooth the part at the gates. Heat treatment is
also sometimes used to harden the final part.  

Investment casting Advantages and
Disadvantages

Advantages

Disadvantages

Ø  Very good surface finish and accuracy

Ø  High tooling cost

Ø  High
strength parts

Ø  Time-consuming process

Ø  Little
need for secondary machining

Ø  Low
production rate

Ø  Can
form complex shapes

Ø  Poor
material strength

Ø  Many material options

Ø  Long lead time possible

 

 

M1: compare and contrast the different
moulding techniques used to manufacture products from metals.

Letter opener

I will
choose die casting as the manufacturing process for my letter opener as it
would allow me to make and work with different types of metals not just
restricting me to one type of metals like other processes. Moreover it will
also allow me to make the letter opener to any size I want with greater
flexibility in terms of size with other processes like sad casting do not
allow. Another reason why I think die casting is good is that it allows you to
make difficult shapes within a design and give the product a good finish. I
would be able to use alloys like Aluminium, Zinc, and Magnesium to make my
letter opener.

There are two types of casting that I
can do however I will go with hot casting rather than cold casting. I think my
firm decision of hot casting is perfect as it will allow me to create something
that is smooth with not roughness which is a must for letter opener. Die
casting is allow particularly good as it reduces waste and even if waste is
produced it still can be burned down and reused for another time which is a
sustainable approach.

However Creating
and designing the mould is a very slow and expensive process as each mould is
made to specific order with different needs and mould each time. Moreover
another problem is that the cast is used only for that specific part and it
cannot be changed once made which is why it is so costly and like a
non-recyclable item.  Another problem
with die casting is that after you have made the die the product will need some
further hardening in order to improve the strength of the product.

After
careful consideration I intend to be firm on my choice of moulding process for
my letter opener.

P2: describe the moulding techniques
used to manufacture a ceramic-based product.

Sintering

The
firing of ceramics materials is called sintering where ceramic powder particles
diffuse with separate particles creating a compaction between the two. The main
reason why sintering is so popular is that it allows reduction of surface
energy of the particles caused by decreasing their vapour-solid interfaces.
During the so called diffusing process the ceramic take place in the green
compact and diminishes resulting in the part denseing thus improving its mechanical
properties. Because of the diffusion this process requires long time and high
temperature because the diffusion proceeds in solid state. Applying pressure decreases
sintering time and this results porosity. Equipment like tunnel kilns and
periodic kilns are commonly used for ceramics sintering (firing) process.

Sintering Advantages and Disadvantages

Ø  Complex shapes

Ø  Large material quantity is needed

Ø  High dimensional precision

Ø  Size limitation based on size chamber

Ø  Excellent surface finish

Ø  High temperature leads to high energy costs

Ø  Reliability and repeatability on large mass production

Ø  High initial capital cost relative to other moulding
processes

 

 

There are two types of sintering that I
have identified:  

A solid
state sintering is where all the densification takes place when the particle
shapes are changed without the elongation and the correct rearrangement of the
liquid in the solid state. Whereas Liquid phase is where some liquid that is
present when at sintering temperatures that it supports compaction.

 

 

 

 

 

 

 

 

 

Powder metallurgy

Producing products like bar and sheets from metal powder is
called powder metallurgy. This process of manufacturing and technique combined
with technical features and cost efficiency are one of the big advantages which
produces sintered hard metals known as ‘carbides’ or ‘tungsten carbides’. This
technique of power metallurgy deals with both metals and non-metals however
they are used
for iron based components. The powders used as raw material can be elemental,
pre-alloyed, or partially alloyed. Elemental powders like iron and copper are
more compressible and produce pressed compacts with good strength. Pre-alloyed
powders are harder but less compressible therefore require higher pressing
loads to produce high density compacts.

 

 

 

 

 

 

 

Advantages
and disadvantages of powder Metallurgy

Advantages

Disadvantages

Powder metallurgy produces near net
shape components. The technique required few or no secondary operations.

The products of metallurgy can have
limited shapes and features.

The tolerance of components produced
by this technique have quite high tolerance, therefore no further machining
is not required.

The production of powder for
metallurgy is very high.

The tolerance of components produced
by this technique have quite high tolerance, therefore no further machining
is not required.

This technique causes potential
workforce health problems from atmospheric contamination of the workplace.

This technique involves high
Production Rate along with low Unit Cost.

The tooling and equipment require for
powder metallurgy are very expensive, therefore becomes main issue with low
production volume.

It can produce complicated forms with
a uniform microstructure.

It’s difficult to produce large and
complex shaped parts with powder metallurgy.

Powder metallurgy has full capacity
for producing a variety of alloying systems and particulate composites.

The parts produce by powder
metallurgy have low ductility and strength.

By using powder metallurgy, parts can
be produced with infiltration and impregnation of other materials to obtain
special characteristics which are needed for specific application.

Finally divided powder like
aluminium, magnesium, titanium and zirconium are fire hazard and explosive in
nature.

This technique has flexibilities for
producing PM parts with specific physical and mechanical properties like
hardness, strength, density and porosity.

This technique is not useful for low
melting powder such as zinc, cadmium and tin as they show thermal
difficulties during sintering operations.

M1: compare and contrast the different
moulding techniques used to manufacture products from ceramics.

Ceramic washer

I have
chosen Powder Metallurgy as my manufacturing technique for my ceramic washer.
This process of manufacturing and technique combined with technical features
and cost efficiency are one of the big advantages which produces sintered hard
metals known as ‘carbides’ or ‘tungsten carbides’. This technique of power
metallurgy deals with both metals and non-metals however they are used for iron
based components. The powders used as raw material can be elemental,
pre-alloyed, or partially alloyed. Elemental powders like iron and copper are
more compressible and produce pressed compacts with good strength. Pre-alloyed
powders are harder but less compressible therefore require higher pressing
loads to produce high density compacts.

I think
that with that many advantages over the other method we should go with powder
metallurgy. Furthermore powder metallurgy produces near net shape components.
The technique required few or no secondary operations; moreover by using powder
metallurgy, parts can be produced with infiltration and impregnation of other
materials to obtain special characteristics which are needed for specific
application.

I believe
with this number of Advantages I should go with Powder metallurgy even though
this technique is not useful for low melting powder such as zinc, cadmium and
tin as they show thermal difficulties during sintering operations also It’s
difficult to produce large and complex shaped parts with powder metallurgy;
however this does not affect me as the washer is small.

P3: describe the moulding techniques
used to manufacture a polymer-based product.

Injection moulding

This
process involves plastic granules which are melted until they are soft enough
to be injected under pressure to fill a mould; this plastic injection moulding
process produces large numbers of high quality parts with great accuracy and
very quickly making it the industry favourite. 
These previous stages ensure that the shape is exactly copied.  Once the plastic moulding has cooled
sufficiently to harden the injection mould opens releasing the part.  The whole injection moulding process then
repeats.

Polystyrene,
nylon, polypropylene and polythene can be used in a process called injection
moulding. These are thermoplastics and this means when they are heated and then
pressured in a mould they can be formed into different shapes.

                                                                                                                                                                                 1.
Granules of plastic powder (note the plastics listed above) are poured or fed
into a hopper which stores it until it is needed.

 

 

2. A heater heats up the tube and when it reaches a high
temperature a screw thread starts turning.

 

3. A motor turns a thread which pushes the granules along
the heater section which melts then into a liquid.  The liquid is forced into a mould where it
cools into the shape (in this case a DVD storage unit).

 

 

4. The mould then opens and the unit is removed.

 

 

 

Rotational Moulding

Commonly known as roto moulding is moulding methods for
plastics which are ideal for making hallow articles; this is a casting
technique which has pressure involved unlike the other technique with no
pressure. Moulds for these methods are relatively cheap as they do not have to
withstand pressure and therefore relatively short production runs can be made
very economically. They are used to make a very diverse range of products. The
process offers the product designer exceptional freedom as just about any shape
can be produced. There is almost no limit to the size of mouldings and there
are literally thousands of applications which can help carry the task out.

The Process

Using rotational moulding is very simple as
the main bit is that a plastic material in powder form is placed into a hollow
mould, usually made from cast aluminium or fabricated from sheet steel. After
this the mould is closed and rotated slowly on two axis. Then the mould is heated
in an oven whilst rotating and the polymer gradually melts and ‘lays-up’ on the
inside of the mould. When the polymer powder fully melts then the mould is
moved to a cooling station and cooled usually with air and sometimes a fine
mist of water. As the mould cools the part solidifies. When the material has
finally cooled sufficiently to release away from the mould surface the process
is stopped and the product is taken out of the mould (de-moulded).

The process of rotational moulding might seem easy but in
fact it is as hard as any technique gets as it’s really complicated. As there
is no pressure involved in this technique it is hard to control the mould  and all other important aspects like the ambient
temperature and humidity, type of mould, material specification and powder
quality.

 

 

 

 

 

 

 

 

 

 

 

Advantages and disadvantages of rotational moulding

Advantages

Disadvantages

Ø  Low tooling costs. As this is a casting process there is
no pressure. This means moulds are inexpensive and low volume can be
economic.

Ø  The materials costs are high due to the nature of the
plastics that must be used.

Ø  It’s easy to make complicated shapes. Rotomoulding readily
accommodates production complexities such as stiffening ribs, moulded inserts
and different surface textures.

Ø  Some shapes and features are difficult to incorporate, so
anything more involved than a simple shape may slow down production, thus
raising production costs.

Ø  There is almost no limit to the size of products and
several different products can be moulded at the same time.

Ø  Rotational moulding is limited to poly-based resins such
as polyethylene, polycarbonate, polyurethane, polyamide and polypropylene, to
name a few.

Ø  Rotational moulding machine costs are low compared to
other processes and the investment required is small. There is great
production flexibility with the process.

Ø  Due to the reduced output, it takes longer to market fewer
materials.

 

Blow moulding

Technique and process

Blow moulding is a process were air is
used to inflate soft plastic bottle into a mould by manufacturing 2 part
manufacturing stage at which firstly a tube is molten plastic is made and then
secondly inflated to the shape the person wants to make. There are two ways in
which the shape can be made either by extrusion or injection. Blow moulding is
used to make hollow plastic containers such as bottles, jars and containers.
Milk containers, shampoo and soda bottles, and watering cans are examples of
products that are typically blow moulded.

 

Advantages and disadvantages

The mould is placed in a mould cavity and inflated to take
the shape of the mould. Blow moulding has both advantages and
disadvantages.  The advantages are that
tooling is low in cost, production times are quick, complex parts can be
manufactured, and products can be recycled. The down side is that parts made
this way must always be hollow and controlling wall thickness is difficult.

There are three types of blow
moulding:

 

1)      Extrusion Blow Moulding

In this process the plastic is first melted and extruded
into an object called a parison, which is a hollow tube of plastic to be formed
into a hollow object, as a bottle, by blow moulding.  The parison is then inserted into a cooled
metal mould.  Air is then blown into the
parison to inflate it into the desired shape. 
When the plastic has cooled enough the mould is opened and the part ejected.
It is for very high production of plastic bottles and is often integrated
downstream with operations such as filling and labelling the bottles.

 

2)      Injection Blow Moulding

Injection Blow Moulding is a process were air is used to
inflate soft plastic bottle into a mould by manufacturing 2 part manufacturing
stage at which firstly a tube is molten plastic is made and then secondly
inflated to the shape the person wants to make. There are two ways in which the
shape can be made by injection moulding.

 

3)      Stretch Blow Moulding

Injection Stretch Blow Moulding is the process of
manufacturing high quality and very high clarity bottles. The plastic is melted
and then injected into a mould to form a preform. The preform is then pre
heated before being held inside two halves of a mould. When the preform enters
the mould then it is inflated using high pressured air while also stretching
it; this would freeze the plastic to the ends of the moulds and this create a
bottle.

M1: compare and contrast the different
moulding techniques used to manufacture products from polymers.

Sports Bottle

The process which I will use and think
is the best is blow moulding for the sports bottle. The reason I choose blow
moulding was that there are three different parts of blow moulding which I
think will create a good bottle. Blow moulding is a process were air is used to
inflate soft plastic bottle into a mould by manufacturing 2 part manufacturing
stage at which firstly a tube is molten plastic is made and then secondly
inflated to the shape the person wants to make and I think this is a unique
point of blow moulding. Also by using blow moulding as my method of
manufacturing I would also benefit from low tooling costs. As this is a casting
process there is no pressure. This means moulds are inexpensive and low volume
can be economic. Furthermore it would also enable me to make complicated shapes
by using a mould.The initial set up of the tooling would be high however for
mass production it would be greater in the longer term.

x

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