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CAD, Computer-Aided Design

CAD, Computer-Aided Design

CAD, Computer - Aided Design
Time: 12 min |

Nowadays there is a vast application of CAD or Computer-Aided Design to act as a powerful tool in to aid in the creation, modification, analysis, or optimization of a design. CAD tools in any software platforms is used to increase the accuracy, designer productivity, create database and digital documentation base for manufacturing, communication and so on. CAD software can also generate output in the form of electronic files for print, machining, or other manufacturing operations. In addition to CAD, the term CADD is also used (Computer Aided Design and Drafting).

Introduction

CAD is considered as an art industry which used in many applications with high importance, including automotive, shipbuilding, and aerospace industries, engineering and architectural design, prosthetics, and many more. One of the most attractive application of CAD is DDC or Digital Content Creation which CAD is used to produce computer animation for special effects in movies, advertising and technical manuals. There is an enormous economic importance for CAD which leads to CAD has been a major driving force for research in computational geometry, computer graphics and discrete differential geometry.

– EDA & MDA

Two special application of CAD have the specific name as EDA and MDA. EDA refers to CAD’s use in designing electronic systems known as Electronic Design Automation or EDA. Similarly, in mechanical design it is known as Mechanical Design Automation or Computer-Aided Drafting (CAD), which includes the process of creating a technical drawing with the use of computer software.

In CAD software, for showing the overall appearance of design objects, vector based graphics (or may also produce raster graphics) are used. However, it involves more than just shapes. The output (exported file) of CAD must convey information include materials, processes, dimensions and tolerances, according to application-specific conventions, as in the manual drafting of technical and engineering drawings.

Another prominent application of CAD might be used to design curves and figures in 2D, two-dimensional space, or curves, surfaces, and solids in 3D, three-dimensional space.

History (1940s – today)

Since computer’s invention designers have used computers for goals such as calculation and modeling. During 1940s to 1950s various development and empowerment were made in computer software. There are few development examples include servo-motors controlled by generated pulse (1949), a digital computer with built-in operations to automatically coordinate transforms to compute radar related vectors (1951), and the graphic mathematical process of forming a shape with a digital machine tool (1952).

Figure 1. Example: 3D CAD model

In 1953, MIT Laboratory, “interactive display equipment” being used by radar operators. A developing program was used in order to create electronic symbols and geometric figures to create simple electronic circuit diagrams and flowcharts. These programs also enabled objects to be reproduced at will; it also was possible to change their orientation, linkage (flux, mechanical, lexical scoping), or scale. This made many possibilities available to them.

The invention of the 3D CAD/CAM is attributed to French engineer Pierre Bézier (Arts et Métiers ParisTech, Renault). He developed UNISURF to design of parts and tools with ease for automotive industry. It was used as the working based for the following generations CAD software. These tools led to some prominent technological developments in such attractive fields in the industries of aircraft, automotive, industrial control, and electronics provided advancements in the fields of three-dimensional surface construction, NC programming, and design analysis.

The development of the SKETCHPAD system at MIT by Ivan Sutherland was a turning point. With this system the graphically interacting between user and computer became available; the design can be fed into the computer by drawing on a CRT monitor with a light pen.

The first CAD system commercial applications were in large companies associated with automotive, aerospace, and electrical industries. These was because of ability of afford a CAD system which was needed for calculations in CAD systems. The foundation of Manufacturing and Services Inc was one of the most influential events in the development of CAD. As computers became more affordable for people and industries, the application of CAD gradually expanded into new areas such as engineering, industries and so on.

Figure 2. 3D rendering of spoons in CAD software

Advances in software development specially programming and also computer hardware, most notably solid modeling in the 1980s, have allowed more versatile applications of computers in design activities. During 1980s the key products such as Romulus (ShapeData), Uni-Solid (Unigraphics), the surface modeler CATIA (Dassault Systemes), and Autodesk (which led to the two-dimensional system AutoCAD). The release of Pro/Engineer in 1987 was the next milestone. Which heralded greater usage of feature-based modeling methods and parametric linking of the parameters of features; this marked the introduction of parametric modeling. This subsequently led to the release of mid-range packages such as SolidWorks, TriSpective (later known as IRONCAD), Solid Edge (then Intergraph), and Autodesk Inventor.

Availability of free and open-source CAD software and high costs of advanced and 3D CAD software may restrain the growth of the CAD software market. Free and open-source CAD software packages include BRL-CAD developed for the US Army, LibreCAD, FreeCAD, and others.

– CAD systems today

These days, people use CAD system extensively. To be precise people use them across all industries and engineering problems. As the CAD system became more affordable for use in PCs, laptops, tables, and smartphones, more and more people use the CAD systems. We remember that these systems once only worked in expensive workstations using UNIX operating systems.

Three-dimensional modeling is the norm today; it even exists in application for the general public. In many industries, CAD has and integral part of the work that employees they do. In fact, some of them would not be able to function in our current business environment without CAD systems. For instance, the Ford Motor Company has started 3D-printing car parts from computer-aided designs.

Uses

Depending on the profession of the user and the type of tools of software that is needed, CAD is used associated with many other tools which are used by engineers. These tools together form whole DPD (Digital Product Development) and PLM (Product Lifecycle Management), which are either integrated modules or stand-alone products, such as:

  • CAE: Computer-Aided Engineering
  • FEA: Finite Element Analysis and FEM: Finite Element Method
  • CAM: Computer-Aided Manufacturing including instructions to computer numerical control (CNC) machines
  • Motion simulation and Photorealistic rendering
  • PDM: Product Data Management for document management and revision control

CAD has been proven to be useful to engineers as well. The four properties which are history, features, parametrization, and high-level constraints, have very vital importance in this. The construction history can be used to look back into the model’s personal features and work on the single area rather than the whole model. Parameters and constraints can be used to determine the size, shape, and other properties of the different modeling elements. The features in the CAD system can be used for the variety of tools for measurement such as tensile strength, yield strength, electrical or electromagnetic properties. Also its stress, strain, timing or how the element gets affected in certain temperatures, etc.

  • CAD allows for simple and accurate automation and/or process modeling (known as Mechanical Design Automation). Traditionally MDA was not possible without first building a physical prototype of every part in the system and then assembling it to check functionality. The ability to digitally model and automate a prototype before ever generating a physical model adds enormous efficiency to manufacturing processes and cost reduction benefits.
  • CAD allows for the ability to conduct Computer Aided Manufacturing (CAM). For example, integrating CAD technology with Computer Numerical Control (CNC) machines or Additive Manufacturing processes (3D printers) e.g. Fused Deposition Modeling (FDM) machines.
  • CAD takes into account material properties and interactivity characteristics between different materials.
  • CAD allows for highly accurate dimensional analysis and mathematical scalability using vector graphic technology (digital images based on mathematical formulas).
  • CAD provides highly precise part tolerance (much lower margin of error between parts).

Types

Nowadays, there are many different types of CAD platforms, each requiring the operator to think differently about how to use them and design their virtual components in a different manner for each. Including a number of free and open-source programs, there are many producers of the lower-end 2Dsystems, which provide an approach to the drawing process without all the fuss over scale and placement on the drawing sheet that accompanied hand drafting since these can be adjusted as required during the creation of the final draft.

Figure 3. A simple procedure

Basically, by extension of 2D drafting we obtain 3D wireframe which is not often used today. Each line has to be manually inserted into the drawing. 3D wireframe final product has no mass properties associated with it and cannot add features directly to it, such as holes. Despite the new tools in CAD systems such as solid modeling, many 3D systems allow using the wireframe model to make the final engineering drawing views.

Two-dimensional projected views can easily be generated from the models. Basic 3D solids don’t usually include tools to easily allow motion of components, set limits to their motion, or identify interference between components. Basic three-dimensional geometric forms (prisms, cylinders, spheres, and so on) have solid volumes added or subtracted from them as if assembling or cutting real-world objects.

There are two types of 3D solid modeling:

  • Parametric modeling allows the operator to use what is referred to as “design intent”. The objects and features created are modifiable. Any future modifications can be made by changing how the original part was created. If a feature was intended to be located from the center of the part, the operator should locate it from the center of the model. The feature could be located using any geometric object already available in the part, but this random placement would defeat the design intent. If the operator designs the part as it functions the parametric modeler is able to make changes to the part while maintaining geometric and functional relationships.
  • Direct or explicit modeling provide the ability to edit geometry without a history tree. With direct modeling, once a sketch is used to create geometry the sketch is incorporated into the new geometry and the designer just modifies the geometry without needing the original sketch. As with parametric modeling, direct modeling has the ability to include relationships between selected geometry (e.g., tangency, concentricity).

Benefits and Drawbacks

Using CAD systems in modeling offers a number of advantages over traditional drafting methods that use rulers, squares, and compasses. For instance, designs can be altered without erasing and redrawing. There is camera viewing in CAD systems that offers special helpful tools such as viewing in different angles, zoom, rotating on any axis, much as one could rotate an actual three dimensional model in one’s hand, enabling the designer to gain a fuller sense of the object. In addition to these features, CAD systems lend themselves to modeling cutaway drawings, in which the internal shape of a part is revealed, and to illustrating the spatial relationships among a system of parts.

To clarify and more understand about CAD systems, it is also helpful that CAD what cannot do. There is big challenge in comprehending real-world concepts in CAD systems; by the example, the nature of the object being designed or the function that object will serve. Generally, the function of CAD systems is codify geometrical concepts based on their capacity. Thus in a CAD modeling process involves transferring a designer’s idea into a formal geometrical model. Efforts to develop computer-based “artificial intelligence” (AI) have not yet succeeded in penetrating beyond the mechanical—represented by geometrical (rule-based) modeling. In recent years, the companies which produce CAD software added some special features to their products that have empowered the CAD software feasibility and performance, features like the definition of weight, tensile strength, flexibility, even manufacturing processes simulation, and so on—into CAD software.

Simulation of performance is one of the most attractive and applicable tools in CAD system technologies which has developed in recent years. These tools make the virtual experiment available, such as testing for response to stress and modeling the process by which a part might be manufactured or the dynamic relationships among a system of parts. To achieve these simulation, CAD systems usually use FEA.

The processes of design and manufacture are, in some sense, conceptually separable. Yet the design process must be undertaken with an understanding of the nature of the production process. The conceptual overlap between design and manufacture is suggestive of the potential benefits of CAD and CAM and the reason they are generally considered together as a system.

The utility of CAD/CAM systems is influenced by recent technical developments. For instance, nowadays, the new configuration of personal systems are available that give people viability as a vehicle for CAD/CAM application, with day-by-day increasing in processing power of them. Another important trend is toward the establishment of a single CAD-CAM standard, so that different data packages can be exchanged without manufacturing and delivery delays, unnecessary design revisions, and other problems that continue to bedevil some CAD-CAM initiatives. Finally, with spreading of visual representation and integration of modeling and testing applications, CAD-CAM software continues to evolve such realms in these fields.

Technology

In the beginning, originally, software for CAD systems was developed with computer languages such as FORTRAN, ALGOL but with the development of object-oriented programming methods this has radically changed. Via development in these activities the modern parametric feature-based modeler and freeform surface systems have been gained. A CAD system can be seen as built up from the interaction of a graphical user interface (GUI) with NURBS geometry or boundary representation (B-rep) data via a geometric modeling kernel. To manage associative relationships between geometry, such as wireframe geometry in a sketch or components in an assembly. These capabilities led to a new form of prototyping called digital prototyping. In contrast to physical prototypes, which entail manufacturing time in the design. Digital prototyping has a vast application in design and modeling which made the many virtual investigations available.

Figure 4. A CAD model of a computer mouse

By the revolution in computer technologies, the CAD systems are not depend on hardware; which no special hardware is required for most of CAD software. However, some CAD systems can do graphically and computationally intensive tasks, so a modern graphics card, high speed (and possibly multiple) CPUs and large amounts of RAM may be recommended.

Computer-Aided Design Multi-Dimensional Viewing

 We need to rotate all models which is created via CAD in all defined axis. By the rotating, we can view two- or three-dimensional diagrams from several angles. In fact, we can see from the inside looking outward. Designers use a special plotter or printer for professional design renderings. The main cause that people like CAD programs is that they can change different design ideas rapidly and with ease. The production of the model in virtual space is another reason for that. To be precise, we can test the model before manufacture it physically. Companies like this because it reduces the cost of modifying prototypes and purchasing parts. Therefore, they get more mileage out of each dollar they spend. A growing number of professions are using computer-aided design programs. Examples include artists, drafters, engineers, and architects.

Range of Computer-Aided Design Systems

Nowadays, for all the major computer platforms, there is at least one CAD software. For instance, they exist for Mac OS X, UNIX, Windows, and Linux. The user interface typically centers on a mouse, pen, and digitizing graphic tablets which we hold. With some CAD systems, you can use stereoscopic glasses to view three-dimensional models.

According to Techopedia:

“Most U.S. universities no longer require classes for producing hand drawings using protractors and compasses. Instead, there are many classes and different types of CAD software.”

Computer-Aided Design Benefits

  • Better Visualization: of the finished product, sub-assemblies, and component parts of a CAD system significantly speeds up the design process.
  • Better Accuracy: people who use CAD software work more accurately. In other words, they make fewer mistakes.
  • Easier: CAD programs offer more robust and easier design documentation, including geometrics and dimensions, bills of materials, etc.
  • Re-Use: the software offers easy re-use of best practices and design data.
Figure 5. Autodesk Inventor, one of the top-ten CAD programs on the market today. It enables designers to create animations, snapshots and exploded videos with a timeline-based story panel to manage it all.

Types of Computer-Aided Design

There are many kinds of CAD, covering a vast range of uses. However, in each case, the design of their virtual components requires a different approach. At the lower end of the 2D systems, there are several free and open source systems. In other words, there are many freely-available programs which we may modify and redistribute. These programs provide an approach to drawing without all the intricacies regarding scale and placement on the drawing sheet that hand drafting requires. During the creation of the final draft, the designer can make adjustments.

– 3D Wireframe

3D Wireframe is an extension of 2D drafting. The designer must manually insert each line into the drawing. The finished product has no mass properties associated with it. For example, it is not possible to add features, such as holes, directly to it. The 3D Wireframe model is an edge or skeletal representation of a real-life object. Models consist of lines, points, arcs, circles, and other curves that define the center lines or edges of objects.

– 3D ‘Dumb’ Solids

With 3D ‘Dumb’ Solids, the designer creates things in a way similar to manipulations of real world objects. You can add cylinders, prisms, spheres, and other basic 3D geometric forms to the design. You can also take them away as if you were cutting or assembling real-world objects. Designers can also generate 2D projected views from the models. More upmarket systems offer capabilities to incorporate more ergonomic, aesthetic, and organic features into designs.

With a computer-aided design program, you can visualize where to place goods on the shelves of supermarkets and other stores. You can move them around and even look at them from different angles.

* Commercial

AgiliCity Modelur, Autodesk AutoCAD, Bricsys BricsCAD, Dassault Systemes CATIA, Dassault Systemes SolidWorks, Kubotek KeyCreator, PTC PTC Creo (formerly known as Pro/ENGINEER), Siemens Solid Edge, Trimble SketchUp, Alibre Design, AllyCAD, Autodesk Inventor, AxSTREAM, Bentley Systems – MicroStation, Cobalt, IRONCAD, MEDUSA, Onshape, ProgeCAD, Promine, PunchCAD, Remo 3D, Rhinoceros 3D, RoutCad, Siemens NX\, SketchUp, SpaceClaim, T-FLEX CAD, TurboCAD, VariCAD

* Freeware and open source

123D, BRL-CAD, BricsCAD Shape, FreeCAD, LibreCAD, QCad, OpenSCAD, SolveSpace

* CAD kernels

Parasolid by Siemens, ACIS by Spatial, ShapeManager by Autodesk, Open CASCADE, C3D by C3D Labs



#01 – Main CAtegory: CFD, FEA, CAD

Mohsen
Mohsen Website
Mechanical Engineer (M.Sc.), with more than 8 years, since 2011, of experience in simulation, analysis, modeling, software courses teaching, academic and industrial research and development. Read more about me

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