Compare CAD and Manual Drawing

Keywords: cad advantages and disadvantages

P1) Identify and describe a range of equipment, furniture and media necessary to produce manual and CAD drawings for the projects.

Manual

There are four types of materials traditionally used for drafting, which come in arrange of sizes including; A1, A2 and A3.

Types of Paper used for drafting;

Bond – This is similar to the paper used everyday in office printers. It’s the least expensive paper and is usually supplied in roll form for drafting plotters. Bond paper is most commonly used in weights from 18 lb all the way up to 24 lb, but much heavier weights are available and used for mainly posters and presentation work.

Mylar – This is a drafting film made from plastic material. It has the advantage of being erasable which, if you are working in ink, is a great advantage. It’s also semi transparent, making it possible to overlay mylar drawings on a light table to check if line work matches up. The film is however more resistant to tears but is more durable than paper. It is still used with drafting plotters and is available in roll form and in cut sheets. Mylar has a matte side and a shiny side which you draw on. The surface of mylar is quite slippery, and therefore pen companies in the past have released special pens and inks which are developed specifically for drawing on it. Modern plotters have found problems printing on mylar as the material does not absorb ink quickly and therefore is prone to smudging as well as unclear lines. Where as bond paper is far more absorbent and does not smudge so easily. Mylar is also quite expensive.

Vellum – This is a linen based paper that has traditionally been used for historical building plans along with many drafting offices. The high linen content makes it durable and allows pencil work to be easily erased and revised multiple times. It’s not as strong as mylar material but is not as expensive. Vellum also has a smooth surface which does not absorb ink as fast as bond paper. That may cause problems with the ink smudging and therefore is not fit for purpose if used for printing. With this said vellum paper is no longer used today to draft plans.

Photo – With the advances in drafting printers, photo media became available in roll form for printing super size renderings and images. It’s a costly media and is usually reserved for the best of presentation graphics. But it allows the engineering office to do more by taking on work that was previously done by printing shops and the graphic designer.

Although these are the four main materials used for drafting tracing has also been used in the past in the drawing industry, but is still heavily used for smaller scale work, such as; school/college/university projects, art projects and much more.

Tracing Paper – this paper is thin and translucent which enables the drawer to copy the image/design several times easily. The faint lines of the image/design are then re-drawn in pencil and are later filled in using a specific drawing pen. The paper comes in a range of grades for drafting work. They start at around 80g/m2 and go up to around 110g/m2 when there are master copies needed. In the past tracing paper when copied using a ammonia copier it was prone to fading in the light and therefore was not clearly visible. However this problem does not occur anymore due to the introduction of photocopying machines which have no side effects as yet.

Drawing boards – The drafting table is still in use despite all the advances in computer aided drafting. There are still many individuals who still use the traditional drawing table. Architects, graphic artists and many structural steel drafters use the drawing table to make and modify there drawings on paper along with pencil or ink. Drawing boards are large tables which are angled with a lip and a rule which slides up and down the board. The instruments allow you to create parallel, perpendicular and diagonal lines. Drawing boards are becoming less popular due to the introduction of Computer Aided Design.

Pencils – These are the main working tool of a draftsperson and are available in arrange of harnesses’. The darkest pencil used for technical drawings is a ‘B’ which is used for shading and adding texture to a drawing. The ‘HB’ pencil follows which is the most commonly used on a day to day basis but is only used for rough sketches for drafting. The ‘F’ is used for printing and general line work. Following on from the ‘F’ is the ‘H’ pencil which is used for dimension lines and hatching by draftsperson’s. Finally is the ‘2H’ which is used for construction lines. For the finest drawings, all pencils used must be permanently sharp and have standard, smooth point. A soft rubber is used for rubbing out pencil lines.

Scale rules – Drawing are produced to a particular scale which will fully fit onto a drawing sheet. The main tool which helps you draw scale drawings more easily is a scale rule, the most common scales; 1:5, 1:10, 1:20, 1:50, 1:100, 1:200, 1:250, 1:500, 1:1000, 1:1250 and 1:2500.

g/m2: refers to the paper quality and weight

Tee Square – It can be used as a guide for architectural and mechanical drawings. It consists of two arms joined at 90 degree angles. The smaller arm moves along the edge of the drawing board and the larger arm is used to draw straight parallel lines. It can also be used to support set squares which can draw lines at different angles.

Adjustable set squares – These are mainly used to draw vertical lines at 90 degree angles to the parallel motion arm. A set square can also produce a line at any angle on the paper by adjusting the scale of the protractor.

Propelling Pencils – A propelling pencil is very thin and can be easily replicable. Unlike a normal standard pencil a propelling pencil always stays sharp due to the thinness of the lead. The most common leads are 0.5 and 0.7. You can also purchase leads in thicknesses of 0.3, 0.9 and 2mm.

Compass – These are used to create circles and arcs when drawing. Precision sets include a thumbwheel compass. A standard compass set includes an extension arm, a pen clamp and replaceable leads. The purpose of an extension arm is to draw larger arcs and circles with the same amount of precision.

Protractor – They are generally made from transparent plastic. Protractors can come either in semi-circle or full 360 degree form. There are bevel protractors which are circular protractors with a pivoted arm used for accurately measuring and creating angles to draw from.

Rubbers – Rubbers come in a large variety of shapes and form. The trapezium shaped is preferred as its points can rub out pencil lines more accurately. Plastic and putty rubbers can be moulded into points to carry out similar work.

CAD

For CAD to be successfully installed and used the computer which will run this software must have CPU with 3 GHz or more. This number of GHz will allow the CAD software to run at the correct speed rather than it crashing/freezing. Microsoft Windows Vista or Microsoft XP are both operating systems which allow CAD to be used successfully. The computer will also need 2GB of RAM on its operating disk and 2GB of free space minimum on its hard drive. The computer screen must have revolutions of at least 1280×1024 pixels which will include a display adapter which is able to produce 32-bite colour 128MB or more if possible.

There are three main hardware configurations for the use of a CAD system. Depending on the size of the company and office will decide which hardware will be in use.

The first software configuration is a standalone single user which simply means that the information and software is held by a private domain. Therefore CAD drawings can only be sent by email or sent by post.

The next main hardware configuration is a small office based intranet where CAD drawings and document information is held in a project folder which is within the computers server. The work is organised by a plot management function which segregates the drawings in order of importance. Therefore the company can easily track and record the drawings within the software easily.

Finally the third main hardware configuration is a large multi located extranet set up for a wide area network which contains various members of a project team which are more often than not in different parts of the country or countries. As there may be members of the project team in another country this extranet allows the members to easily access the drawings or information which has been uploaded from the drawing office onto the internet through subscription.

Mouse’s, keyboards, digitisers/pads and light pens are used everyday by CAD workers.

Mouse’s – A standard mouse has two buttons which are positioned where your fingers lie on the mouse. 2D motion ball mouse’s are also used and easily direct the mouse much like a standard mouse. More advanced mouse’s include scroll buttons or additional buttons which are found on the side of the mouse which allow the user to carry out a task quicker. Laser mouse’s are far more accurate than a standard mouse as the movements are a lot more refined.

There are more advanced mouse’s like the trackball mouse which are far more accurate due to the trackball which is located at the top of the mouse. These mouse’s are used by designers, gamers and web designers. The actual trackball contains optical and mechanical sensors which are able to track movement and therefore gain on accuracy.

Keyboards – The most common is the QWERTY keyboard which is used for everyday life and has all requirements covered. However if you are sat at your desk in the office all day you may face some health and safety issues due to the basic design of the QWERTY keyboard. Therefore there are keyboards specifically designed for this issue which are called Ergonomic keyboards which are designed to relieve stress. Using a keyboard can result to carpal tunnel syndrome and repetitive stress injury therefore the ergonomic keyboard was designed for this purpose and is recommended by doctors. Finally there is the DVORAK keyboard which is an ergonomic alternative to the QWERTY keyboard. QWERTY keyboards were designed to comply with typewriters and therefore they are ineffective for touch typing. For that reason the DVORAK keyboard was invented for touch typing which also adds to the comfort of the typer.

Digitisers/pads and light pens – These are electronic drawing pads which allow people to easily draw and scribe free hand. This enables easier usage of the computer.

P4

AutoCAD

AutoCAD is usually used on Microsoft desktop software and is available in around 20 languages. It is a form of CAD software which is used to produce 2/3 dimensional designs. AutoCAD can be used for a range of tasks including designing landscapes, buildings and automotive machinery. The earlier versions of AutoCAD used basic functions which included lines, circles, arcs, plotlines and text. The latest version of AutoCAD is more advanced than the earlier additions and is able to form solid modelling such as creating prisms, boxes and spheres. There are also far more detailed and accurate models which use 3D tools. There are many support programs which use AutoCAD such as Auto LISP, VBA, Object ARX and Visual LISP. Object ARX is a base model which helped create AutoCAD Architecture, AutoCAD Civil 3D and AutoCAD Electrical.

AutoCAD LT – This is a smaller, cheaper version of AutoCAD which can easily be purchased from computer stores unlike the full version of AutoCAD, purely due to the cost of the who AutoCAD programs. AutoCAD LT costs around $900 where as the full version of AutoCAD costs around $4000 which is far more specialist. AutoCAD LT costs around a quarter of the price of the AutoCAD full version as it has to compete with other similar software’s where as the full version of AutoCAD is unique and is the only software of its type used by company in this sector of work. However due to the cheapness of AutoCAD LT software there are some features which are excluded from this software which are included on the full version of AutoCAD. One of the features excluded from the LT version is the 3D function, others include the exclusion of LISP programs and the inability to interact with 3rd party programs.

AutoCAD student version – This version has a noticeable price difference for student, teachers and lecturers, and can be licensed for 14 months. There are few features which are included on AutoCAD but of which are excluded from the AutoCAD student version. However when a DWG file is created or changed by the student the file is given an educational flag and when this type of file is printed on AutoCAD software it has a plot stamp or banner on all four sides and therefore makes it invalid for commercial use. If a student imports a DWG commercial file they will infect the file so that it can then be used commercially. Also a registered student can has access to free AutoDesk applications from the AutoDesk community. Hence the student therefore has access to the Civil 3D version and the Architectural version of AutoCAD software’s.

Other AutoCAD software’s – There are many vertical programs which have been designed such as AutoCAD Architecture or AutoCAD Civil 3D. These vertical programs allow the designer to illustrate 3D objects with more intelligent data rather than using sample lines, circles and other solid objects. The program can also be programmed to symbolize products used to construct the design. Therefore the data can be used to estimate the overall cost for the construction of the building, the cost of the materials and other values needed for the building as a whole.

Managing CAD

Designers need to be assured that the CAD software will save, store and manage their work efficiently so that it can easily be found if changes are required. To achieve this, major company’s have different files for their software. Graphisoft’s ArchiCAD is an example of this. This software depending on whether the data is two or three dimensional, Graphisoft’s ArchiCAD uses a filing system of which the designers work is stored in a drawing database. DWG files can be easily imported onto this system and this allows a larger range of information to be stored. Thanks to the DWG software, the latest version of CAD has been strengthened and developed by using the DWG software as the primary file format. Due to the filing system employed by the DWG system it is popular with most designers.

Due to frequent updates CAD is now a well-built piece of software and has helped improve modern day computers due to the requirements needed to run the CAD software successfully. The modern day computer now has a greater ram, better resolutions, far more memory, superior CPU and more enhanced hard drives which means that the computer can easily support the software’s which are ran through them.

CAD can project an image in several ways, of which include; Orthographically, Isometrically, Axonometrically and can use perspective views but sometimes an exploded view is used. An exploded view can take apart an image to show the parts and layers which enables you to examine all parts of the original image. This view is used by Architects and Engineers to enable them to perfect their projects. A designer can use pre-set symbols to represent objects such as doors for a cross section of a building.

CAD also allows you to use standard house designs, which can save time for architects and therefore allows them to be ahead of the project and deadlines. The CAD software allows you to easily save work into electronic drawings and also enables you to transfer drawings by email.

CAD enables you to create very realistic designs and images depending on the specific CAD software which you are using. The software allows you to create 3D virtual environments which include pictures of real life buildings and people. Other software’s enable you to create naturalistic textures including sunlight, shadows, plants which move in the wind and people walking or moving. To meet the clients needs certain CAD programs allow you to create walkthroughs. This allows the client to visually see their building in a realistic view rather than two or three dimensional form drawing.

Advantages and Disadvantages of using CAD and Manual drawings

Manual Drawings

Advantages;

• Cheaper to buy the equipment needed to construct the drawings such as set squares or scale rules.
• If the equipment is broken or not working correctly the user can simply buy a new one without having to go to allot of trouble.
• The equipment never needs updating as it is already adequate to carry out the job correctly.
• If you are on site it is far easier to use a manual drawing as you are able to get a better perspective and scale.
• Easy to modify a manual drawing.
• You do not need as much technical ability.
• You always have a hard copy.

Disadvantages;

• Takes a long time to post or fax the drawing to the client.
• Need a large, light area to set out and work on the drawing.
• The equipment can be effected by human error maybe a shaky hand.
• It takes a long time to construct or reproduce a drawing when manually drawing.
• It is difficult to get the pressure applied to the pencil to determine the type of line you are looking to achieve whether it is a tracer line or primary line.
• A manual drawing can get easily damaged.
• A manual drawing is far harder to store as each drawing takes up space and you need put a storage system in place so that each individual drawing can easily be found.

CAD

Advantages;

• The drawing can be accurate as the tolls on the software are electronic so they won’t be affected by human error such as the incorrect thickness of line.
• The user can save their work to any electronic storage device such as the hard drive of the computer or a CD or even a memory stick.
• The computer memorises the drawing in every dimension possible so that the user doesn’t have to waste time trying to remember what the drawing looked like and which is which drawing.
• It is very easy for the user to rectify any mistakes they have made or to move a part of the drawing. Rotate a 3D drawing or to erase any irrelevant parts.
• The drawing can be transferred by email, saving on postage time and cost.
• CAD is far quicker to use.
• The storage and organisation of drawing using CAD software means drawings can easily be stored, don’t take up any office space and are well organised and maintained.

Disadvantages;

• Some shapes are still very difficult to draw using CAD software.
• It is very expensive to purchase CAD software no matter what version you choose.
• The computer and the necessary equipment needed have to be maintained and regularly updated which adds to costs.
• If the software was to crash or something went wrong it will need to be fixed by a professional in this field of work which costs time and money.
• CAD is very difficult to use and is regularly updated, therefore it is very hard to use and understand. As a result you will regularly need to be trained on how to use the software which adds to costs and time.
• If the software was to break all of the drawings and information ever saved on the computer software may be lost.
• CAD is not always suitable for site work.
• There are always doubts concerning glitches or viruses to the computer system.

How the quality of graphical information significantly affects the quality of the completed civil engineering/construction project.

In the construction industry ‘finished work ‘it contains a number of things such as the written specification; whether the designers requirements were met or not; whether the contractor has estimated the cost accurately or not; the products are ordered within time; whether the design and construction team have kept misunderstandings to a minimum.

Consequently the graphical information for the civil engineering/construction project must always be correct and accurate. The graphical information should include every single material or item that is needed for the civil engineering/construction project with all its specifications. The designer must ensure they have created an accurate drawing along with a detailed schedule plan. This will ensure the contractor has the all of the correct products ordered before the work is supposed to commence. However if the architect or designer knows they have not achieved an accurate drawing they may include a schedule which they have used already on a similar project so that they can spend the remaining time modifying their drawing so that it meets their own and the clients standards. Though this may save time for the architect to create a perfectly accurate drawing the schedule is inaccurate and therefore lowers the standard of the project and also may add to costs as they may have the wrong equipment as the schedule is not specific to the project. If the schedule initiates up to the construction stage this may cause the project to run past the deadline dates and therefore add cost to the overall project.

If the designer creates an accurate drawing for the project which is specific and contains the specific schedule it means that the overall finished construction of the project should also be of a high quality because it allows the contractors to plan ahead before the construction work starts. But if a schedule of high quality is used on the project which has originally used on a similar project the quality of the overall construction will suffer as a result. So no matter how detailed a schedule or information is on the drawing will only create a high quality project if it is specific and accurate to the job.