airframes chapter 3 manufacturing technology

8/12/2019 Airframes Chapter 3 Manufacturing Technology

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Uncontrolled copy not subject to amendment

Airframes

Revision 1.00


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Chapter 3:

Manufacturing Technology


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Learning Objectives

The purpose of this chapter is to discuss in more detail, thetools and processes technology that is utilised in themanufacture and assembly of an airframe.

By the end of the lesson you should have an understandingof some of the processes, techniques and tools used in themanufacture of the component parts of an airframe.

But first a recap of Chapter 2 with some questions.


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Chapter 2 Revision

A few questions about the previous chapter.

1. What is meant by the term Homogeneous ?

2. Which of the following 3 materials has the highestStreng th to W eigh t Rat io ?

a. High Tensile Steel

b. Aluminium

c. Titanium

3. Name the one of the three types of Composite Repair?

4. What does the term GLARE stand for?


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What is Man Tech

Manufacturing technology (or Man Tech) provides the toolingrequired to enable the production of all manufactured goods.

These magnify the effort of individual workers and provide the powerto turn raw materials into finished and functioning products.

Production tools include machine tools and other related equipmentand their accessories and tooling.

Machine tools are non-portable, power-driven manufacturingmachinery and systems used to perform specific.

Computer Aided Design (CAD) and Computer AidedManufacturing (CAM) as well as assembly and test systems tocreate a subassembly or final product.


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Manufacturing Tools & Techniques

For the purposes of this subject, Manufacturing Technologycan be broken down into the following sub-sets.

Material removal and tooling

Material forming

Additive processes

Controls/Software Plastics technology


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Material Removal and Tooling

The vast majority of tools and techniques withinManufacturing Technology fall within machining processes and perhaps form the basis of the public perception ofManufacturing .

This can range from the simple hand saw through to lasercutters. The tools and techniques most likely to be used inthe manufacture of aircraft structures are;


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Cutting

Cutting is the most common material removal andmachining processes.

Cutting is typically achieved using a cutting blade with

hardened teeth to cut through (or Saw ) the workpiece.

Cutting can also be achieved through the use of a highvelocity jet of ionised gas that conducts electricity. Thistechnology is referred to as a Plasma Cutter .

The plasma heats the workpiece, melting material andallows the operator to produce complex cut-outs.


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Drilling

Like cutting, drilling is one of the most common materialremoval and machining processes. It is estimated that overtwo-thirds of all metal-cutting material removed comes fromdrilling operations.

Drilling is an operation that uses a hardened rotating tool toproduce a round hole in a workpiece. This is accomplishedmost typically by using a twist drill.

Drilling is generally performed before machining operationssuch as boring, reaming, tapping, counterboring,countersinking and spotfacing.


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Turning & Boring

Turning is one of the basic machining processes andproduces solids of revolution which can be tightlytoleranced because of the specialized nature of theoperation.

Turning machines can be used to enlarge drilled or coredholes this process is referred to as Boring .

The turning process is performed on amachine called a Lathe in which thework piece is mounted on the chuck,which rotates relative to the stationarytool.


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Grinding

Grinding is a finishing process used to improve thesurface finish, abrade hard materials, and tighten thetolerance on flat and cylindrical surfaces by removing asmall amount of material.

In grinding, an abrasive material rubs against thecomponent to remove material and is typically on thesurface of a wheel or belt.

The excessive heat produced during the grinding process,requires the use of fluid within the cutting area to preventthe workpiece becoming damaged or distorted.


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Milling

Milling is as fundamental as drilling among the poweredmetal cutting processes and uses a rotating cutter that ismoved laterally to remove material from the workpiece.

Milling is versatile for a basic machining process, butbecause the milling set up has so many degrees offreedom, milling is usually less accurate than turning orgrinding.

For manual machining, milling is essential tofabricate any object that is not axially symmetric .


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Broaching

Broaching uses a toothed tool, to remove material fromthe workpiece.

The process is used when precision machining isrequired, especially for odd shapes as Broaching finishes

a surface in a single pass, which makes it very efficient.

Commonly machined surfaces include circular and non-circular holes, splines, and flat surfaces. Typicalworkpieces include small to medium sized castings,forgings, screw machine parts, and stampings.

Even though broaches can be expensive, broaching isusually favorable to other processes when used for high-quantity production runs


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Electrical Discharge Machining

Electrical Discharge Machining (EDM) is also referredto as spark machining, spark eroding, burning, die sinkingor wire erosion

The material removal from the workpiece occurs by aseries of rapidly recurring current discharges between twoelectrodes, separated by a dielectric liquid and subject toan electric voltage.

EDM is a manufacturing process whereby thedesired shape of the workpiece, is obtainedusing electrical discharges (or sparks ).


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Material Forming

Not all components can be manufactured through the useof Material Removal tools & techniques.

It is often advantageous to use Material Forming

techniques, where it is easier to manufacture morecomplex components whilst maintaining the materialproperties.

Material forming techniques include;


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Bending

Another of the basic manufacturing processes, bending isone of the most common material forming processes.

If a bend is required in a workpiece (be it sheet metal, baror tube), a Bending Machin e is used to apply a strain atthe desired location to form the designed bend.


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Forging

Forging is the term for shaping metal by using localisedcompressive forces.

Cold forging is done at room temperature or near roomtemperature, whilst Hot forging is done at a high

temperature, which makes metal easier to shape and lesslikely to fracture.

Warm forging is done at an intermediate temperaturebetween room temperature and hot forging temperatures.

Forged parts can range in weight from less than akilogram to 170 metric tons.

Forged parts usually require further processing to achievea finished part.


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Types of Forging Process

There are many different kinds of forging processesavailable, however they can be grouped into three mainclasses:

Drawn out: length increases, cross-sectiondecreases

Upset: Length decreases, cross-section increases

Squeezed in closed compression dies: produces

multidirectional flowCommon forging processes include roll forging, swaging,cogging, open-die forging, impression-die forging, pressforging, automatic hot forging and upsetting


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Casting

Casting is a process by which a liquid material is pouredinto a mould, which contains a hollow cavity of the desiredshape, and then allowed to solidify.

The solidified part is known as a casting, which is ejectedor broken out of the mould to complete the process.Casting materials can be metals or various cold settingmaterials that cure after mixing two or more componentstogether; examples are epoxy, concrete, plaster and clay.

Casting is most often used for making complex shapesthat would be otherwise difficult or uneconomical to makeby other methods.


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Pressing

Pressing is a manufacturing process that allows flat sheetsof metal to be formed into three dimensional workpieces

It can also be used to shear the sheet metal in order to cutout forms, press holes or other features using specialpunches and dies

Pressing machines have a stationary bed and a slide (ram)

which uses a controlled reciprocating motion toward andaway from the bed surface


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ExtrusionExtrusion is a process used to create objects of a fixed

cross-sectional profile, where the base material is pushedor drawn through a die of the desired cross-section.

The two main advantages of this process over othermanufacturing processes are;

Its ability to create very complex cross-sections andwork materials that are brittle, because the materialonly encounters compressive and shear stresses.

It also forms finished parts with an excellent surfacefinish.

The extrusion process may be continuous or semi-continuous and can be done with the material hot or cold.


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Additive Processes

Additive processes, otherwise known as Rapid Prototyping is a manufacturing process for the rapid andflexible production of sample parts for demonstration,evaluation and/or testing.

It typically uses advanced layer manufacturing technologiesthat can quickly generate complex three dimensionalobjects direct from computer based models

Rapid prototyping techniques include;


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Fused Deposition Modelling

Fused Deposition Modelling is a process which formsthree-dimensional objects from CAD-generated solid orsurface models.

The Fused Deposition Modelling patterns are generallyused when an acroylonitrile-butadiene-styrene thermalplastic part is required for use in a working prototype.


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Laminated Object Modelling

Laminated Object Modelling is a process that createdmodels from inexpensive, solid-sheet materials.

The process is similar to that of Sterolithography in that itslices a three-dimensional electronic file from the

computer to the Laminated Object Modelling machine toproduce parts for use in visualisation models, castingpatterns and designs.


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Selective Laser Sintering

Selective Laser Sintering is a flexible technology thatuses a CO 2 laser beam to fuse ( sinter ) layers of nylon,metal or trueform powdered materials into a three-dimensional model.

This is a leading rapid prototyping technology as it providesmore choices of materials for flexibility and has moreapplications than the other technologies.


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Stereolithography

Stereolithography is a manufacturing technology wherethe layers are formed using a laser to cure the surface of abath of photo-sensitive polymer resin in order to producethe desired shape.

The process takes a CAD design andproduces a solid three-dimensionalprototype model using a combination oflaser, photochemistry, optical scanning andcomputer software technology.


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Controls/Software

A feature of modern manufacturing technology, computersoftware has improved not only the accuracy of the designprocess, but also the material output.

Often, the more complex machining operations with tightengineering tolerances can only be achieved using toolingcontrolled by computer.

Typical processes encountered include;


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Computer Aided Design

Computer-aided design (CAD) is the use of computertechnology for the design of objects, real or virtual.

As in the manual drafting of technical and engineering

drawings, the output of CAD must also convey symbolicinformation such as materials, processes, dimensions,and tolerances.

CAD may be used to designcurves and figures in two-

dimensional space or curves,surfaces and solids in three-

dimensional objects.


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Computer Aided Manufacturing

Computer-aided manufacturing (CAM) is the use ofsoftware tools in the manufacture of product components.

Its primary purpose is to create a faster productionprocess and components with more precise dimensions

and material consistency, which in some cases, uses onlythe required amount of raw material (thus minimizingwaste), while simultaneously reducing energyconsumption.

With CAM it is possible to manufacture physical modelsusing CAD programmes, creating real life versions ofcomponents designed within a software package.


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Computer Integrated Manufacturing

Computer-Integrated Manufacturing (CIM) is a closed-loop method of manufacturing in which the entireproduction process is controlled by computer.

The traditional separated process methods are joinedthrough a computer by CIM.

This integration allows the processes to exchangeinformation with each other to initiate actions. Throughthis, integration the manufacturing can be faster and with

fewer errors.

The main advantage is the ability to create automatedmanufacturing processes.


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Numerical ControlNumerical Control refers to the automation of machine

tools that are operated by means of predeterminedprogrammed commands, as opposed to manuallycontrolled via handwheels or levers.

This can be found in the following forms; Computer Numerical Control (CNC): Control of the

machine tools is performed by a softwareprogramme executed by a computer.

Direct Numerical Control: Control of a number ofCNC machines by a large centralised host computer.

Distributed Numerical Control: Hierarchical controlof all machine tools controlled by a central plantcomputer, where the controllers are themselves

CNC units.


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Plastics Technology

Plastics technology is the collective of processes used toturn a wide range of synthetic or semi-synthetic organicamorphous solid materials into a final product.

A number of processes are available, but for the purposesof this chapter the following will be considered further;


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Blow Moulding

Blow Moulding is a manufacturing process by whichhollow plastic parts are formed from thermoplasticmaterials.

There are three main types of blow moulding;

Extrusion Blow Moulding: produces a hollow plastictube from the die head and then expanded within thecavity by air pressure to produce a blown object.

Injection Blow Moulding: supported by a metal core

pin to produce blown objects. Stretch Blow Moulding: is used in both of the above

types to produce odd blown shapes, referred to as Bi-oriented.


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Injection Moulding

Injection Moulding is a manufacturing process forproducing parts from both thermoplastic and thermosettingplastic materials.

Material is fed into a heated barrel, mixed, and forced into a

mould cavity where it cools and hardens to theconfiguration of the mould cavity.


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Co-Injection Moulding

The Co-Injection Moulding process is similar to that of theInjection Moulding process.

The key difference is that the mould cavity is first partially

filled with one plastic and then a second shot is injected toenclose the first shot.

There a two types, Machine Based and Mould Based.


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Compression Molding

Compression moulding uses material, generally

preheated, that is first placed in an open, heated mouldcavity. The mould is closed with a and pressure is appliedto force the material into contact with all mould areas.Heat and pressure are maintained until the mouldingmaterial has cured.

The process employs thermosetting resins in a partiallycured stage and advanced composite thermoplastics canalso be compression moulded with unidirectional supportmaterial.

The advantage of compression moulding is its ability tomould intricate parts and produces fewer knit lines andless fibre-length degradation than injection moulding.


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Die

Within the context of Plastics Technology , the term die,mould and tool are sometimes considered the same.

This is considered true in that they have a female ornegative cabity through, or into, which the molten plasticmoves under heat and pressure.


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Plastics Extrusion

Plastics extrusion is a high volume manufacturingprocess in which raw plastic material (often in bead form) ismelted and forced through a die to form a single continuousprofile.

The process is similar to that of Metal Extrustion .


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Thermoforming

Thermoforming is a manufacturing process where aplastic sheet is heated to a pliable forming temperature,formed to a specific shape in a mould, and trimmed tocreate a usable product.

The plastic sheet is heated to a high-enough temperature,so that it can be stretched into or onto a mould using avacuum and cooled to a finished shape.


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Curing

Curing is the process that refers to the toughening orhardening of a polymer material by cross-linking of polymerchains, brought about by the use of chemical additives,ultraviolet radiation, electron beam or heat.

In rubber, the curing process is also called vulcanization.

With composite materials, the final process involves curing

the assembly using heat in an Auto-clave or large oven.


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Ultimate Aim!

By using the previously mentioned tools, techniques andprocesses, it is possible to do the following..


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Questions

Here are some questions for you!

1. What is meant by Forging ?

2. What does the acronym CNC stand for?

3. What is an Additive Process ?

4. Name the 5 Manufacturing Technology sub-groupings?
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