Use Of Cad In Product Development Process Computer Science Essay

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CAD is used every day by designers and engineers in all fields from designing motor vehicles right down to the design of kitchen appliances.

CAD was first developed in 1962 and since that time has come a long way. Manufactures of CAD software are continually coming up with ways in which to improve the design process and improve the simplicity and ease of use of their software. The history of CAD and its development has been reviewed.

Basic Principles of CAD have been discussed, its uses and applications and how it fits in within the 'Product Development Process'.

Two industrial case studies conveying the use of CAD within the marine and oil drilling industries has been explored.

CAD (Computer Aided Design) software refers to computer programs which assist designers and engineers in a wide range of industry applications to design and manufacture 3D products. This can range from building bridges to cars to designing mobile phones.

The first CAD software called 'Sketchpad' was developed in 1962 by Ivan Sutherland at MIT; although very primitive it allowed the designer to interact with the computer graphically with a light pen which was able to draw on the computers monitor.

Large automotive and aerospace companies were the first to use CAD software commercially due to the relatively high cost of computers and to the complex engineering requirements of these automobiles and aircraft.

Some of the larger electronic firms such as Motorola used CAD for PCB design. However the use of CAD became more widespread during the 1970's.3

CAD software has come a long way since those early days and is now an affordable solution for even the smaller companies. The use of CAD is not just limited to the engineering industry but is also used by architects and by people in the art and design industry to create complex sculptures and pieces of art which would be time consuming or near impossible to create by hand.

Literature Search

History of CAD

In 1957 Dr Patrick J Hanratty developed the first commercial CAM (Computer Aided Manufacture) software system, a numerical control programming tool called PRONTO.

The first CAD software called 'Sketchpad' was developed in 1962 by Ivan Sutherland at MIT, although very primitive it allowed the designer to interact with the computer graphically with a light pen which was able to draw on the computers monitor.

1971 - MCS was founded in 1971 by Dr P.J Hanratty, it has since had a reputation as a technological leader in CAD/CAM software. It is estimated that 70% of 3D CAD/CAM systems available today trace back to MCS's original code. [1] 2D drafting and basic 3D wireframe was used during the 70's. Surface modelling came about in the late 70's and 80's.

1975 - Solid Modelling software started to appear which used basic Boolean operations such as add and subtract to create shapes and parts.

1979 - Boeing developed the IGES industry standard format for transferring complex information such as NURBS curves.

1981 - The first Solid Modelling system was introduced by a company called Unigraphics.

The first commercial solid modeller program, 'Syntha Vision' was released by Magi in 1969.

PC's appeared in the 1980's and Autodesk released the first CAD software for PC's 'AutoCAD' in November 1982. [2] 

Basic Principles of CAD

2D Drafting

Early CAD systems were essentially an electronic drawing board. Design engineers were still working in 2D to create technical drawings made up of standard entities such as points, lines, arcs, conic sections and splines etc...

Any design modifications and alterations were easier than by doing them by hand and gradually the software and hardware became more affordable.

2D CAD nowadays is useless for anything other than representation; however the 2D techniques still form the fundamental basis for many 3D CAD operations. [3] 

Wire-frame Modelling

Wire frame models are skeletal representations of 3D parts or models using lines or curves. It is essentially 2D drafting with an additional 'Z' axis.

Wireframe is usually used to visually view the structure of 3D objects like solids, surfaces and mesh's.

A wireframe model is built up of points, lines and curves which define the edges of the part or model. This type of 3D modelling is time consuming as objects which make up the model must be drawn and positioned independently. [4] 

Wireframe models can be used for:

Simplicity

Sheet metal work3

Analyzing spatial relationships such as distances between corners and edges and to check for any interference.

Programming tool paths for CNC machining.

Wire-frame modelling has a very limited use in further analytical techniques and is generally very limited in its uses; its pictorial representation can be very ambiguous.

http://www.dmmultimedia.com/multimedia/jaguar_003b.jpg

Figure - Jaguar S Type Model [5] 

Surface Modelling

Surface modelling was developed in the late 1970's for the automotive and aerospace industries to design and manufacture complex shapes. [6] 

Surface modelling is basically the 'skinning' or 'surfacing' of a wire-frame model to give it the look of a complete part. Surface modelling is used today for complex 'freeform' surfaces such as car bodies and turbine blades. The surfaces for these models will be generated from complex curves such as Bézier, B-Spline, Cubic or NURBS (non-uniform rational B-splines).3

IGES supports Cubic and NURBS and is used as a file format to exchange data between different CAD software packages.

The CAD system will generate polynomial equations to represent Cubic and NURBS formats but will keep the mathematics behind the surfacing hidden from the user.

Complex Curves and Surfaces

Bézier

A Bézier curve is defined as a curve made up of four points, two at each end and two in between which affect its shape. [7] This was one of the first methods of curve creation techniques in CAD software. The drawback to this type of curve is that they approximate their control points; they are also a polynomial representation and are not as flexible as B -Spline curves.

This type of curve is only globally modified meaning if one point is moved it affects all of the others apart from the two end points. [8] 

http://eom.springer.de/common_img/b110460a.gif

Figure - Bézier Curve with 2 control points8

Cubic Spline

A Cubic spline is a curve which goes through a number of control points. This type of curve can sometimes be locally modified; meaning moving one control point will only affect the curve in its vicinity.3

B-Spline

This curve is a modification to the Bézier curve formula to allow local modification.3

NURBS

NURBS is a mathematical representation of 3D geometry that accurately describes any shape from simple 2D shapes to complex 3D surface models or solid models. Its flexibility and accuracy mean it can be used in any process from the initial illustration to the actual manufacturing. [9] The following qualities make it the perfect choice for CAD:

Models can be transferred between modelling and analysis programs due to the industry standard way of exchanging NURB geometry.

NURBS accurately represent standard objects such as circles and lines as well as freeform surfaces such as car bodies.

NURBS reduces database complexity and eases graphics and manipulation.3

http://www.3drender.com/nurbana/figures/mouthcenterb.gif

Figure - Head built from NURBS surface [10] 

Surfaces

The simplest type of surface is a flat plane, but there are other complex surfaces formed from already generated surfaces such as fillets, blends and chamfers as well as the complex curves discussed earlier.

There are also surfaces which are curve based, such as a revolve, loft and sweep.

Solid Modelling

There are two basic types of solid modelling: Constructive Solid Geometry (C-Rep or CSG) and Boundary Representation (B-Rep). The more advanced solid modellers are a combination of the two and called Hybrid modellers.

C-Rep or CSG

CSG allows the user to create complex surfaces or parts by using 'Boolean' or 'set-theoretic' methods. A library of primitives (simple shapes) such as cubes, cylinders, spheres, prisms, and pyramids are added, subtracted or intersected to build up a part.

Figure - Workings of CSG [11] 

CSG is only good for basic modelling as it is very difficult to create complex models such as car bodies.

B-Rep

B-Rep is a method where boundaries of an object are defined and the CAD software constructs a solid within the boundaries. [12] 

Two parts make up a B-Rep model: topology (Faces, Vertices and edges) and geometry (Curves, Surfaces and Points).

Models are produced by 'stitching' a surface model or by 'extruding' a curve profile.3

Uses and Applications

CAD is a tool which is used in many applications by designers and engineers in various professions. Each type of CAD software will require the user to think about the most efficient way to use it and the best way in which to design their part.

Their ultimate goal will be to simplify all future work on the current project. A sound understanding of the CAD system being used is crucial and any additional time spent on learning could mean additional savings in the future.

CAD is used in many applications within many industries such as automotive, aerospace, telecommunications, architecture, medical and many more.

CAD is not just used to create a 3D image of a part; it may also be used to create technical drawings, assembly diagrams, and may also supply additional information such as BOM (Bill of Materials), processes, tolerances and dimensions.

CAD is regularly used in technical guides and manuals to show how parts are to be assembled to build the model.

FEA and Testing

During the product development stage there are numerous costs when it comes to testing the product. Any product which is developed will undergo some sort of testing, this may be physical and will ensure that safety standards are met and to ensure that the product will work effectively within the conditions it is expected to operate in.

The following may be conducted: Stress Analysis, Thermal Analysis, Structural Dynamics, Computational Fluid Dynamics (CFD) and Electromagnetic Analysis.

An aeroplane wing will be put through vigorating stress tests to make sure that it can withstand the severest of weather condition before it gets full approval for use. If the company building the wing had to build a new wing every time they made a change and tested it, this would be time consuming and ridiculously expensive.

By using CAD software it is possible to simulate severe wind conditions on the plane wing and run virtual stress tests. Not only is testing time reduced but so is cost, the greatest advantage being that design modifications can be made instantly as the tests are conducted.

When physically testing complex wing shapes it can be near impossible to discover where unexpected turbulence is being caused in certain conditions. With the virtual tests, any alterations to complex designs can be tested over and over until the issue has been fully resolved. [13] 

http://www.raetech.com/Analysis/images/view%20of%20using%20rigid%20bolt.PNG

Figure - Wing Spar - FEA [14] 

Rapid prototyping systems require high quality 3D CAD models in order to produce a high quality accurate part. It is not possible to use 2D CAD or wireframe models for any RP process.

Rapid Prototyping

Rapid prototyping systems require high quality 3D CAD models in order to produce a high quality accurate part. It is not possible to use 2D CAD or wireframe models for any RP process.

The STL file format has become the industry standard for RP machines. The surface of a solid 3D CAD model is represented as a closed volume mesh approximated with triangles. The number and size of triangles used is defined by the complexity and accuracy of the model surface.

Nearly all of the CAD software packages available today are capable of saving 3D models as an STL file.

CNC Machining

In CNC machining, the part building is automated using CAD/CAM software. A 3D CAD model is created in a CAD software package and this file is then transferred to a CAM software package which produces a 'G code' file that interprets the commands needed by the CNC machine. This file is then transferred to the CNC machine and the outcome should be a part which matches the 3D CAD model very closely.

Technical Drawings

Technical drawings are used by design engineers, architects and many other professionals. A technical drawing must be concise and clear so that an engineer is able to look at it and transform it into a physical form.

Using CAD software the process of technical drawing has been fully automated and a great reduction in time made. In CAD packages such as SolidWorks®, a 3D model is created and from this it is possible to generate technical drawings automatically. There are various 3D views and projections which can be used and it is also possible to add dimensions and remove any which are not required.

Using 3D CAD software it is possible to create cutaway drawings of 3D parts or models. This allows internal features of a 3D part or model to be made visible whilst still showing part of the exterior features. This is a useful feature as it provides a visual illustration of a complex part such as the internal parts of an engine.

These sorts of drawings are used greatly in user and repair manuals to show the location or connectivity and linkage of parts.

http://www.bmbikes.co.uk/photos/mechanicalphotos/-5%20engine%20&%20gearbox%20cutaway.jpg

Figure - BMW R Model Engine [15] 

Architecture

3D CAD is used widely by architects worldwide, the benefits are endless and the end result is a far superior product than if created by hand. Human error factor is reduced and there are higher rates of production with a smaller team. Accuracy is far greater and any errors will probably be noticed quicker than if it was drawn by hand.

Using 3D CAD software is far quicker and simpler than if drawing by hand as any design iterations can be made instantly.

Storage space is reduced as all data is stored on a hard drive and is not in paper format. Templates of regularly used parts can be made, such as doors, windows and staircases etc… thus reducing time again.

CAD models can also be imported into software such as Photoshop so they can be rendered and special effects added if required to enhance them visually for clients.

3D drawings can also be sent to clients or other departments instantly via email, eliminating the need to send paper copies by mail or internally.

CAD and the Product Development Process

When it comes to product design, many companies are not very well configured so management and coordination of the design process can prove to be difficult.

A well oiled product development plan will:

Improve quality of the product

Reduce the cost of prototypes

Reduce the time taken to market the product

Make a reduction in waste material

Help to integrate the whole team involved in the work.

The Design Process

A competitive market place now means shorter product lifetime, therefore adding pressure to increase design productivity. CAD can be utilised to improve product quality and by using it as a simulation tool during the design process will allow product systems and sub systems to be graphically and mathematically simulated.16

The use of CAD will not automatically generate new concepts and designs, this will be down to the design engineer's creativity; CAD is just a tool which can be utilised by the designer. The use of CAD within a company allows design teams and manufacturing teams to work simultaneously as both groups will have access to the same data "concurrently instead of consecutively" and this in turn will allow the design and manufacturing functions to work together. [16] 

Re-interpretation involving any design information is reduced due to paper less drawings and all data being stored electronically. The output from the CAD process can be sent directly to the CAM process therefore eliminating the need for paper drawings to be transferred via the different departments.

For CAD to be used successfully during the product development stage it is crucial that the design engineer is aware of the different manufacturing technology and processes available so they understand the problems and techniques which come with product design. Without this knowledge the use of CAD is pointless.

Flow Chart Showing Use of CAD3

Programming Package

Concept Design Modelling

No

Is design evaluation possible with available software?

Develop customized software

Modelling and graphics package

Inspection and Robotics Package

NC Package

CAPP Package

No

Yes

Yes

Yes

No

Assembly

Inspection

Machining

NC programming

Manufacturing discrepancies in CAD data?

Process Planning

Documentation

Drafting

Is final design suitable?

Design testing and evaluation

Benefits of CAD uses

In today's economic climate companies are under huge amounts of pressure to respond to consumers ever-changing needs. The life cycle of many products has been shortened and the requirement for customised products has increased more so.

By responding to these customer demands it will allow these companies to be far more successful than their competitors.

By moving to use CAD technology these companies are extensively benefiting by increasing their profits.3

Some of these benefits may be:

Rapid Prototyping

3D CAD models are used to create prototypes or actual parts by using Stereolithography, FDM and other RP techniques.

FEA

3D CAD models are used for analysis and therefore reduce the number of physical prototypes which are required. This reduces cost and time of producing prototypes.

CAM

3D CAD models are used to generate CNC part programmes, and tool paths can be verified before actual building of the part commences.

CE

3D CAD data is shared therefore allowing engineering and manufacturing processes to work simultaneously. Many CAD systems allow the user to make changes to the actual model and the drawing will update automatically with these new changes.

Higher Quality

The end product should be of a higher quality due to the increase in efficiency and being able to explore different design iterations during the product design and development process.

Lower Unit Costs

Cost will be reduced due to the minimal amount of prototype expenses.

Personnel Development

The technology used for 3D CAD modelling provides a challenging working environment for employees. There will always be a number of ways to achieve the desired outcome but it is critical that all designs are created in the most efficient way possible.

Personnel Advancement

The implementation of a 3D CAD system to a company opens up job opportunities regarding the management and supervision of that department.

Identify and Eliminate Inefficiencies

Any inefficiency in existing work practices can be eliminated with the implementation of 3D CAD.

Increased workload Capacity

If the 3D CAD is used efficiently it will allow a greater output of work whilst maintaining the same number of staff.

Greater feedback and control of production operations

3D CAD enables machining tool paths to be created, updated and verified with minimum human involvement.

Improved overall communications

An electronic paperless system will be used rather than traditional paper based designs. Data can be transferred between departments far more easily and efficiently.

Increased Accuracy of MRP Data

MRP (Material Requirements Planning) software can be linked to 3D CAD data and easily managed.

Increased Design Flexibility

The tools available within most 3D CAD software are far more robust and allow designs to be modified.

Increased Design Data Integrity

Any changes are reflected accurately and quickly due to a single 3D CAD model supporting all downstream processes.

Industrial Case Studies

CAD/CAM for Marine Moulds

Company: Lanulfi

Location: Italy

Specialise in: Marine model and mould manufacture

Due to marine models and moulds being rather large, they are split into manageable parts. These parts then fit together like a jigsaw to resemble the full scale model or mould.

The surfaces must be of a superior quality to perfectly match with the various components as any errors with continuity during assembly will require costly repair.

Lanulfi use 'powerSHAPE CAD' software by Delcam to import clients designs and then to make modifications to the design to streamline the manufacturing process, and to split the design into smaller parts. These smaller parts are machined in Polyurethane using CAM software and then assembled to make the full scale model. This model is then used to create a resin mould which is used in the final manufacture of the boat.

"According to Lanulfi, the software performs very accurate machining when using continuous five-axis operations, allowing for high-precision components and surfaces with a quality finish". [17] 

The CAD software is also flexible as it allows users to edit tool paths and to visualise cutting processes on screen to ensure that the parts are fabricated perfectly without supervision.17

Oil Well Drilling - PDF Documents, Manuals & Animations.

Company: Tesco Corporation

Location: Alberta, Canada

Specialise in: design, manufacture and service of technology-based solutions for the upstream energy industry.

Tesco Corporation specialise in design and manufacture of products and services which reduce the cost of drilling.

They have a daunting task of connecting their CAD modelling division with their multimedia, press and web departments who need to make animations, PDF's and presentation material out of the CAD drawings to demonstrate their drilling techniques.

Using software called 'Solidworks into 3ds Max' by Okino, they are able to transfer CAD files from SolidWorks® into a 3D rendering software which allows them to compress large CAD files and add affects and animations to use for presentations and documentation. [18] 

Without CAD software this would be a laborious task which would have to be done on some sort of photo editing software such as Photoshop.

Figure - Images from PDF Brochures and Manuals18

Conclusion

Over the past 50 years CAD software, the way in which it is used and its purpose for use has drastically changed. There is not one 3D CAD package which is perfect; there will always be ways in which it can be improved. One issue with many packages is the complexity and lack of simplicity for people of a non design/engineering background to understand it.

It is inevitable that using CAD definitely speeds up the 'Product Development Process' as problems can be identified at earlier stages and reductions in cost made.

As mentioned earlier for CAD to be used successfully it crucial that design engineers are aware of the different manufacturing technology and processes available so they understand the problems and techniques which come with product design.

The reduced cost of 3D printers now means that designers are able to communicate more directly with customers by producing 3D prototypes much quicker and earlier during the 'Product Development Process', this in turn produces a product of a high quality, reduces the time to market and allows non technical customers to view an actual part rather than an on screen CAD file.

'Actuality Systems' a company specialising in 3D displays has been researching the idea of a 3D holographic display which will show the 3D CAD model on screen as a hologram which would be viewable from all angles [19] , if this idea was to materialise it would again significantly reduce the cost of prototyping and further speed up the 'Product Development Process'.

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