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Eyeglasses also called spectacles, are frames bearing lenses worn in front of the eyes, normally for vision correction, eye protection, or for protection from UV rays. Eyeglasses supported by pads on the bridge of the nose and by temples placed over the ears.
Important of the Product:
Eyeglasses help from defect eye like myopic or cylindrical or both of them.The lenses of eyeglasses are ground in the form of concave spherical lenses for nearsightedness (myopia),convex spherical lenses for farsightedness (hyperopia), cylindrical lenses for astigmatism,and prisms for defects of convergence.Frequently it is necessary to grind lenses in a combination of these forms to correct several anomalies at once.The upper part of such lenses is ground for distant vision and the lower part for close vision, so that the user has merely to lower the eyes to read and raise them to look at distant objects.
Eyeglasses is very need for people who has defect eye. From the aspect of economic,by manufacture the eyeglasses,it helps to reduce the unemployment in our country.If the eyeglasses is exported to other country,it even contributes to the economic of our country.The cost to produce a eyeglasses is medium and the price to buy it is agreed price and affordable for every people.
2.0 Material for the product
The materials used in production of eyeglass lenses are polycarbonate.Eyeglass frame made from aluminum.Manufacturers select materials that are stiffness and strength,toughness,corrosion,good electrical conductivity and good thermal conductivity and low density.
2.1 Eyeglass Lenses:
Characteristic of Polycarbonate:
Polycarbonate is a clear,colorless thermoplastic polymer. They are easily worked, moulded,and thermoformed.It is brittle,so it won't easily to break.This polycarbonate is a very durable material,and can be laminated to make bullet-proof "glass",though "bullet-resistant" would be more accurate.
This polymer is highly transparent to visible light and has better light transmission characteristics than many kinds of glass.Polycarbonate possesses extraordinarily good dimensional stability with a high impact strength which is maintained over a wide temperature range.The melting temperature is 225oC Polycarbonate is very lightweight. It has low density. The density of polycarbonate is 1200 kgmâˆ’3.
They also have the best impact resistance. Polycarbonate is excellent resistance(no attack)to dilute acids and mineral oil. It also good resistance(no attack)to alcohols and vegetable oil.The termal conductivity is 0.180 W/m-°C.The toughness is 1.8MN mâˆ’3/2.The abrasion resistance is low.The tensile strength is 10,000 psi.The hardness is 114-122. Cost of polycarbonate is high.
We will choose polycarbonate to make eyeglasses lens because it has high impact resistance which it is not easy to break compare to the glass.Besides,it has highly transparent to visible light compare to glass.Polycarbonate has low density which is suitable to make a eyeglasses lens.
2.2 Eyeglass Frame:
Characteristic of Aluminum:
General colour of aluminum is silver.Frames made from aluminum is a non-ferrous metal.Aluminum is used primarily by high-end eyewear designers because of the unique look it creates.Aluminum is not only the world's most abundant, but also the most widely used,non-ferrous material.
Aluminum has high stiffness and strength.It can be alloyed for high rigidity,strength,and hardness.Besides this,aluminum use as material of frame is toughness which is caoacity to absorb energy better than other classes of materials.Although aluminum are highweight,aluminum has a tensile strength and exhibits high strength to weight ratio.
Aluminium is a soft,lightweightAluminum offers excellent corrosion resistance,It is highly resistance to corrosive media such as environment(oxygen,pollution,acid rain),and water.Aluminum can avoid rust when it gets wet because cHYPERLINK "http://en.wikipedia.org/wiki/Corrosion"orrosion resistance is excellent due to a thin surface layer of aluminHYPERLINK "http://en.wikipedia.org/wiki/Aluminium_oxide"ium oxide that forms when the metal is exposed to air,effectively preventing further oxidation.
Aluminum has high electrical conductivity that is approximately27Î©m/cm and high thermal conductivity that is222W/mK,and melting point of 699.7Â°c.Instead,aluminum has low density 2700Kg/m3.The cost of aluminum is very low.
Factor in selecting aluminum compare with stainless steel are their density,their stiffness and strength,their resistance to corrosion by environments,their cost and their melting point.Aluminum provide 669.7Â°c compare with stainless steel which provide 1420Â°c.After consider the cost and characteristic of each other,Aluminum is select as the material of eyeglass frame.
3.1 Producing the frame of eyeglasses
Solidification of Aluminum (Through Casting Process)
Starting work material is either a liquid or molten condition,and a part is created through solidification of the material.In producing the frame for the eyeglasses,aluminum was being chasing as a main material of making the frame because of is wide use and advantage.Casting can create both external and internal shapes.Through solidification process,the step of casting for metal was being choosed.Casting process which molten metal flows by gravity or other force into a mold where is solidifies in the shape of the mold cavity.In this process,aluminum is being heated to become a heaten liquid or highly plastic state.As the diagram shows below,the molten metal is being pour into a mold and let it solidifies to form part geometry.
After producing the aluminum through the solidification process,the aluminum will undergo a coating process.The aluminum will take the place as a core and coating process will done through plastic molding.This is because aluminum generally considered to be very castable although it has strong properties and easy of machining.Besides,this will make the person who wear the eyeglasses more comfortable and strength to wear.Thus,the aluminum is suggest to undergo the coating process.
Bending of the frame of eyeglasses(Bending the aluminum)
Standard die sets are used to produce a wide variety of shapes.After producing out the part of the frame,the part need to undergo a bending process.Bending process is a flexible and conventional process which many different size and shapes of parts can be produced.A standard die sets are use to produce a wide variety of shapes and sizes.Firstly,the material(aluminum)is placed in the dieand positional in place. With stop or gagesThe part is hold in place with hold downs.The upper part of the press the ram with the appropriately shaped punch descends and forms a bend shape.
After producing the frame of the eyeglasses,punching process will be needed which is a fabricating process that removes a scrap slug from the work piece each time a punch enters the punching die.Its ability to produce economical holes in roll material.Besides,multiple punches can be used together to produce a complete part with just one stroke of the process that means by the process.This means by using multiple punches will decreasethe cost,time and energy.Punching process is needed to connect the frame and the lens.
3.2 Producing the nose pad of eyeglasses
Casting process is use to produce the piece of connector(the nose pad) between the frames and lens.Frames and the connectors are choosed to make of aluminium which are lightweight and highly corrosion-resistant.Firstly,aluminium is go through the casting process.Casting process is a process which a molten metal flows by gravity or other force into a mold where it solidifies in the shape of geometry of the mold cavity.At first,the aluminium which is choosing will undergo the melting process.Then it will pour into a mold and after that the molten aluminium will let to freeze.The mold in casting contains the cavity which geometry will determine the part shape and size.
The solidification process:
After producing the part(the piece of aluminium)from liquid state to solid state,the part also need to undergoing the coating process with plastic.This coating process is to make sure the aluminium is corrosion free.This also not just make the person wear eyeglasses more comfortable,but also safety with corrosion free.
The coating process:
So,after the coating process,the part with desired size and geometry will go through the bending process.Bending is a flexible and free process which many shapes can be produced.Standard die are use to produce a wide variety of shapes.The material is placed on the die,and positioned in place with stop or gages.
Solidification process use to produce the connector between two lens.
3.3 Producing the lenses of eyeglasses
To make the lenses of eyeglasses
By undergoing the solidification process,the starting material which is a molten liquid then pour into a mold through pouring ladle to form part geometry.This is the net shape processes which most starting material is used and no subsequent maching is required to get the final part geometry.
To make the shape of lens of eyeglasses
After producing the part of lens of eyeglasses,it must be undergo over die cavity and the punch and pushes the part into the opening.Under this process,it can produce various shapes and sizes.
After producing the mold,it will be arranged to undergo vacuum thermoforming process to get either negative or positive mold to get concave or convex shape.So,for lens,we will chosing to produce negative and which need concove cavity.
After producing the plastic lens through the solidification process,the lens also must undergo the punching process before undergo assembly operations.A slug or scrap was cutting out after the punching process then the hole will filling by screw through drilling process.The remaining stock will be the desired part.Punching process is a fabricating process that removes a scrap slug from the workpiece each time a punch enters the punching die.Its ability to produce economical holes in roll material.The illustration that follows shows a few common punches and die configurations and the workpiece would be formed by this combination.Multiple punches can be used together to produce a complete part with just one stroke of the press.Through the process,the hole(slug) will be dropped and we will get a part with the hole we want.
Solidification of Plastic:
Besides we using the plastic to make the lens,we also use plastic to make "supporter" for the eyeglasses.The starting material we will use the heated liquid plastic then will solidifies to form a part geometry after undergoing the solidification process.Firstly,the starting material is heated to transform into form of liquid or highly plastic state.Then will pour into the mold to form the part with vary size and geometry.
Then the part which produce will undergo punching process before undergo assembly operation.A slug or scrap was cutting out through the punching process then the hole will filling by screws through drilling process.The remaining will be the desired part which with desired size and geometry.
4.0 Assembly Operation
Two assembly processes are involved:
4.1 Mechanical Assembly
It will use various fastening methods to mechanically attach two or more parts together.This assembly is to create a temporary assembly.It is a process which involve on the assemblies of aluminum eyeglasses.It is a temporary assembly that using fasteners.This screws are to attach the frames and the lens.
The mechanical assembly is choosed to use to connect the frame and the lens because of its easier for packaging and more strong.Furthermore,mechanical process is selected to assemble eyeglasses because it is ease of transportation and ssembly.This means that the eyeglasses can be transported or changed to disassembly form and can assemble it again at the desired or same place.Thus,this means that it can also accomplishedby unskilled workers with minimum of special tooling and in short time.This will save the time and also more easier.
Screw Thread Inserts
For eyeglasses,screw thread inserts are used to assemble the lens and the frames.There are seven part are use screw thread inserts.At first,a hole with desired size and position is making through lens by using punching process.Then the internally threaded plug or wire is designed to be inserted into an unthreaded hole of aluminum frame,and then it accepts on externally threaded fasterner or screw with the attached part.When assembly of screw is drilled into insert,insert barrel expands into hole to secure the assembly.So,we will use bolts and nuts to join the frames and lens.
We use mechanical assembly:to join frame and lens
We use mechanical assembly:to connect lens to the aluminum frame
We use mechanical assembly:to join the two aluminum part(the frame)together.
4.2 Joining Process:Welding
Welding process is an assembly process to create a permanent joint which welded components become a single entity.Welding is a joining process which two or more parts are coalesced at their contacting surfaces by application of heat or pressure.Heat or pressure is use but heat will be choosed to use to join the aluminum and plastic.The type of welding used is welding under the solid state welding category.Solid statewelding is results from application of pressure or a combination of heat and pressure.Resistance welding is choose to use which a group od fusion welding processes that use a combination of heat and pressure to accomplish coalenscence.The heat is generated by electrical resistance to current flow at junction to be welded.Welding is chosen to join the aluminum tube and the nose ped because can form a strong joint.The joining must be strong enough to support the eyeglasses.Furthermore,welding is cheaper compared with others assembly.Lastly,welding not restricted to factory environment,it can be accomplished "in the field".
The part which using welding:
4.3 Adhensive Bonding
Adhensive bonding which is a joining process and a filler material is used to hold two(or more)closely-spaced parts togethers by surface attachment.It is used in wide range of bonding and sealing applications for joining a similar or even dissimilar materials.Hence,we choose to use adhensive bonding to join the frames.