1.1 Introduction to concept of drawings | unit 1 introduction

CACED

Unit – 1

Introduction

1.1 Introduction to concept of drawings

Drawing is a form of visual art in which a person uses various drawing instruments to mark paper.

An engineering drawing is a type of technical drawing which is used to convey information about an object.

Drawings convey the following information: -

Geometry – the shape of the object; how the object will look when it is viewed from various angles, such as front, top, side, etc.

Dimensions – the size of the object is captured in units.

Tolerances – the allowable variations for each dimension.

Material – represents what the item is made of.

Finish – specifies the surface quality of the item, functional or cosmetic.

Engineering drawing is the basic need to develop the design and assembly of a machine, the three necessary techniques of drawing/projection are:

Orthographic Projection: In this method the object is placed in space in such a way that the front view of it is taken in the vertical plane, and the top view of the same, is taken in the horizontal plane, other name 'orthographic'.

Perspective Projection: The observer's eye position, height, and the distance from the object, all affect the outcome of the drawing. Two sub-methods are adopted for this projection technique are Visual Ray Method and Vanishing Point Method.

Isometric Projection: It gives the total detail of the component under consideration. The basic principle behind isometric projection is that it involves the consideration of three axes that are inclined to each other making equal angles with each other (120 deg).

1.2 Interpretation of typical drawings

The Engineering Drawing Interpretation course is a guide to interpreting drawings found in manufacturing. It is the ‘short course’ of ‘need to know’ information for blueprint reading. Beginning with the background of blueprints, looking at the types of lines used on a drawing, and how parts are shown in different views

The first step in making quality parts or assemblies is computing the drawing correctly and applying the given information to the final product.

Completing this course should enhance the learner’s ability to maintain employment in a manufacturing/machining area and/or.

1.3 Planning drawings to show information concisely and comprehensively

Building Drawing.

A drawing is prepared before constructing any structure.

A drawing is needed for every building, but the drawing of a big building is very accurate Since constructional details of a small building may remain in the mind of someone, but a big building cannot remain in the control of anyone.

The drawing of a building is prepared 1st, and then it is approved is to be had from local authority.

The drawing of building should be in accordance with the bye laws of local municipality.

Each and every body has made some rules and restriction by considering the health of people and environment of locality which are called ByeLaws

Many sketches are prepared for the building drawing.

1st of all a single line sketch is prepared showing size and arrangement of rooms. It is called the line plan.

In detailed drawing the detailed plan is show the detail of order, size, and thickness of walls of room

Foundation detail is to show the size and depth of foundation.

Separate working drawing are prepared for electricity, gas, water supply and sewerage column, plumbing, etc

The submission drawing is then made to get the approval of municipal corporation or other concerned development authority according to their bye-Laws

Types of Building Drawing.

1. Site Plan.

2. Line Plan.

3. Detailed Plan.

4. Foundation Plan.

5. Landscape plan.

6. Elevation.

7. Sectional Elevation.

8. Perspective Drawing.

9. Submission drawing

10.Model

1.4 Optimal layout of drawings and Scales

When you work in a layout, the scale factor of a view in a layout viewport represents a ratio between the actual size of the model and the size of the layout.

This ratio is determined by dividing the paper space units by the model space units

You can change the view scale of the viewport by using

The characteristic palette

The triangular scale grip in a selected viewport

The Viewports Scale on the status bar

The XP option of the ZOOM command

Note:

Scaling or stretching the layout viewport border does not affect the scale of the view

You can modify the list of scales that are displayed in all view and plot scale lists with SCALELISTEDIT.

Annotative Objects and Scaling

It is defined at a paper height instead of a model size and assigned one or more scales. These objects are scaled based on the recent annotation scale setting .The annotation scale controls the size of the annotative objects relative to the model shape in the drawing.

Scale drawing

Scale drawings are used to illustrate items that it is not useful or convenient to draw at their actual size

A distance at full size: The distance at the scale used that would be the same length.

For example:

A full-size drawing would be 1:1 (or sometimes 1/1 or ‘one to one’).

A tenth size drawing would be 1:10.

A triple size drawing would be 3:1.

In the construction industry a range of scales are available

For example:

A location plan at 1:1000.

A site plan at 1:200.

A floor plan at 1:100.

A room plan at 1:50.

A component drawing at 1:5.

An assembly drawing at 1:2.

Original sheet size that the scale was drawn at, so for example A4, A3, A2, A1, A0, and so on.

Sometime we use more than one scale on a single drawing, for example, to show the elevation of land across a significant distance. In this case, differences in elevation might be illustrated at a larger scale and a smaller scale used for horizontal distances.

While in other cases a scale might use more than one unit of measurement.

The use of CAD and building information modelling (BIM) has introduced a new concept to this process

1.5 Introduction to computer aided drawing

It involves creating computer models defined by geometrical characteristic. CAD systems enable designers to view objects under a wide variety of representations.

CAM uses geometrical design data to command automated machinery. CAM systems are associated with computer numerical control (CNC) or direct numerical control (DNC) systems.

Computer-aided design and manufacturing systems are commonly known as CAD/CAM.

THE ORIGINS OF CAD/CAM

CAD had its birth from 3 sources. The first source of CAD resulted from attempts to automate the drafting process. The second source of CAD was in the testing of designs by simulation. The third source of CAD development resulted from efforts to smooth the flow from the design process to the manufacturing process using numerical control (NC) technologies.

Advantages of CAD:

1. Save’s time: It can make better and more systematic designs in shorter time duration.

2. Easy to edit: it will be much easier and safer to make any changes because you can fix the errors and modify the drawings easily.

3. Decrease in error percentage: the percentage of error that occurred because of manual designing is decreased.

4. Decrease design effort: It has been reduced significantly because the software brutalise most of the task.

5. Easy to share: It makes easier to save the files and store it in a way that you can use it time and again.

6. Improved accuracy: The fact that the kind of accuracy that CAD software will offer can never be achieved by opting for manual drawings. You have tools to measure the precision, skill and accuracy level of the designs.

Disadvantages of CAD:

Work can be lost because of the sudden crash of computers

Work is liable to viruses

Time taking process to know how to manage or run the software

High production or purchasing cost for new structure.

Time and cost of training the staff.

Needs less employment because of CAD/CAM systems

1.6 Coordinate systems

AutoCAD drawing file can be identified by its X, Y, Z coordinates or WCS i.e., World Coordinate System

Coordinate input

Absolute Cartesian (X, Y) coordinates in the form X, Y (for example, 6,5)

Relative X, Y coordinates in the form @X, Y (for example, @4,6):

Relative polar coordinates in the form @distance<angle (for example, @6<30):

Draw by numbers

It define absolute X, Y coordinates with respect to the 0,0 point of the drawing — usually, its lower-left corner...

Data is defined in both horizontal and vertical coordinate systems. Horizontal coordinate systems locate data cover the surface of the earth, and vertical coordinate systems locate the elevation or depth. Horizontal coordinate systems can be of three types: geographic, projected, or local

1.7 Reference plan

Reference Work Planes

It is defined as a plane on the face of the extents of a modifier. Every modifier has an unseen extent, or boundary box, that defines the extents of the feature

These are the various ways of a reference plane, example of each one:

Offset Distance

Coincident with 3 vertices

Coincident with a line and a vertex

Angle

Parallel

Tangent and Parallel

Tangent and Perpendicular

Mid Plane

Perpendicular at a Point

Create a plane parallel to the screen

1.8 Commands: Initial settings

Before we make a drawing, we make many settings in the blank file like changing Units, Limits, Adding Layers, Line types, Blocks Dimension styles etc and it is not always empirical to duplicate the settings.

To make it easier, we can make a drawing template in AutoCAD. Templates are saved with DWT file extension and saved file work in a template file it gets saved as a DWG file.

Setting Drawing Units

Close all open tabs from your AutoCAD window to reach the start screen. Now click on the arrow which is next to “Templates” and select acad.dwt template from the list

A completely blank drawing will open. Go to Application menu on the top left of AutoCAD window and select Drawing Utilities option and then select Units or you can also use its command UN.

The Drawing Units window will open with default settings as per the selected template. Click the Type drop-down menu and change the unit type to Architectural, if you are a metric user then change it to Decimal.

The precision is simply the precision up to which AutoCAD will display the decimal places. Irrespective of the precision format

In the “Units to scale inserted content” dropdown change the value to Inches, this is the Unit which will be displayed in the drawing

In the Angle panel change type to Decimal Degrees, we can change it to other angle formats as well from the drop-down menu. Change the precision from Angle drop-down menu to 0.00

Click OK to save these changes and close the Drawing Units window.

Understanding Units representation

When Architectural length type is selected in the Units window, we can use apostrophes symbol to specify the drawing units like (‘) for feet and (“) for inches. For example, if you want to make a line of length 5 feet and 6 inches then you can enter its length as 5’6” on the command line.

If you are using Decimal length format instead of Architectural then feet and inches symbol will return an error. For example, to make a line of length 1’4” simply type 16 for its length (1’=12”) without any apostrophes.

Setting drawing limits

We need to specify the extents of the working area of the drawing. All the drawings are not made on a single scale as an example a large floor plan of an Hall would take a lot of space and its dimensions will be in the range of many feet and if you are making a simple watch gear then the dimensions should remain in the scale of a few millimeters.

we will make a simple drawing which has maximum dimensions of 10 feet in length and width. So, to make it we will define a drawing area of 15 feet in length and width keeping 5 feet margin.

Type LIMITS and press enter. Command line will prompt “Specify lower left corner or [ON/OFF] <0′-0″,0′-0″>:” simply press enter to accept the default values of the lower left corner which is 0,0.

On the next step “Specify upper right corner <1′-0″,0′-9″>:” type 15’,15’ and press enter.

To apply the changes type Z and press enter then type A and press enter again. This will reset your drawing area.

Now the height of your drawing area is 15 inches and the length of the drawing area will be 15 inches.

This limit value is not a permanent value and you can alter the limits by zooming in or out of your drawing.

Creating drawing Template

To save these changes as a template go to application button the top left of the drawing area and select “Save As” option and select Drawing Template.

Save Drawing As window will open with a list of templates in the Template folder

You can save your template with these pre-existing templates or you can also specify a new location to save the template file.

Now click on save and click OK when description box opens. The template will be saved on the desktop with dwt file extension. You can now open your drawing with this template simply by double-clicking on the My Template file on the desktop.

Opening drawing with no templates

If you don’t want to use any preinstalled or custom template to start your drawing moreover you want to open the drawing with the blank properties then there is an option for that too. Click on the “New” icon on the quick access toolbar or use command NEW.

The drawing template window will open. Click on the arrow right next to the open button and select “open with no template”.

1.9 Drawing aids

The drawing aids in the AutoCAD program are like the triangles, compasses, and engineering scales of traditional drafting.

1.10 Drawing basic entities

ENTITIES: It is the main section of a drawing file and contains the actual characteristic Each characteristic contains standard information, such as its colour, layer, line style, and geometry.

In a drawing you can create a variety of different entity types. Drawing entities can be very simple such as lines, circles, arcs, points and rays or complex such as polylines, splines and planes.

To create an entity you can choose between selecting the command in the Draw menu, using the tools on the Draw

When you use a tool or a drawing command, the program box open to enter coordinate points, such as endpoints or insertion points. You can enter the points or distances either using a mouse or by typing coordinate values in the command bar

New entities are made on the current layer, using the current colour, line type and line weight.

1.11 Modify commands

Modify Panel is used for the editing of any existing drawing.

Erase (E+Enter)
Offset (O+Enter)
Array (AR+Enter)
Explode
Lengthen
Break (BR+Enter)
Break at point
Join (J+Enter)
Edit Hatch
Edit Array
Edit Polyline (PEdit+Enter)
Edit Spline
Scale (SC+Enter)
Trim (TR+Enter)
Extend (EX+Enter)
Fillet (F+Enter)
Chamfer (CHA+Enter)
Blend Curves

19. Erase (E+Enter)

20. Offset (O+Enter)

21. Array (AR+Enter)

22. Explode

23. Lengthen

24. Break (BR+Enter)

25. Break at point

26. Join (J+Enter)

27. Edit Hatch

28. Edit Array

29. Edit Polyline (PEdit+Enter)

30. Edit Spline

31. Move (M+Enter)

32. Rotate (RO+Enter)

33. Copy (CO+Enter)

34. Mirror (M+Enter)

35. Stretch

Essential Commands of Modify Panel in AutoCAD

Move (M+Enter): -

We can move any objects at a specified distance and direction.

Process of using move command: -

Select Move Command from modify panel.

Select the object.

Right click.

Left click on object.

Move it any direction.

D Enter

Type distance

Enter.

Rotate (RO+Enter): -

We can rotate any selected object around a base point to an angle.

It rotates any objects in clock and anti-clockwise.

Process of using Rotate command: -

Select Rotate command from modify panel.

Select the object.

Right click

Specify base point

Enter C (copy) or Enter R (reference)

Type rotation angle

Enter.

Copy (CO+Enter): -

It is used to copy an object at a specified distance or direction. It works almost like Move Command.

Process of using Copy command: -

Select copy command.

Select object.

Right click

Specify base point.

Move it any direction.

Make multiple copies.

Enter.

Mirror (MI+Enter): -

It creates a reverse copy of the selected object.

Process of using mirror command: -

Select mirror command.

Select object.

Right click.

Click on the first point of mirror line.

Drag mouse in the direction where you want to make mirror

Specify the second point of mirror line.

Enter.

Stretch: -

In these, one can move some part of drawing with carrying the connection with other parts.

Process of using Stretch command: -

Select Stretch Command.

Select the part of the object which you want to stretch.

Right click.

Drag the mouse in that direction where you want to stretch.

Scale (SC+Enter): -

We one can enlarge or reduce the objects. The length and width of objects would be enlarged or reduced at the same size.

Process of using Scale command

Select Scale command.

Select the part of the object which you want to enlarge or reduces.

Select base point

Type the value

Right click.

Drag the mouse.

Trim (TR+Enter+Enter): -

It is used to trim any objects whose edge meet the other objects. It trims the crossed line.

Process of using Trim Command: -

Select trim command from modify panel

Double Enter.

Double click on the intersect line or extra line.

If we want to exchange trim command into Extend command enter shift.

Extend (EX+Enter): -

It helps to extend the line to join the edges of other objects line. It is used as a trim command.

Process of using Extend command: -

Select Extend command from modify panel.

Select object.

Specify opposite corner.

Right click.

Double left click on object whom you want to Extend.

Enter.

1.12 Layers

Choose Format, Layer.

2. Type LAYER at the command prompt.

Command: LAYER (or LA)

3. Pick the layers icon from the Layer Control box on the object properties toolbar.

? Lists layers, with states, colours and line types.

Make Creates a new layer and makes it current. Set

Sets current layer.

New Creates new layers.

ON Turns on specified layers.

OFF Turns off specified layers.

Colour Assigns colour to specified layers.

Ltype Assigns linetype to specified layers

Freeze completely ignores layers during regeneration.

Thaw Unfreezes specified layers Ltype.

Lock makes a layer read only preventing entities from being edited but available visual reference and osnap functions.

Unlock Places a layer in read write mode and available for edits.

PlotTurns a Layer on for Plotting

No PlotTurns a Layer Off for Plotting

LWeightControls the line weight for each layer

1.13 Text and Dimensioning

Select Home tab

https://help.autodesk.com/cloudhelp/2020/ENU/AutoCAD-Core/images/ac.menuaro.gif

Annotation panel

Dimension Style.

2. In the Dimension Style Manager, select the style you want to change. Click Modify.

3. In the Modify Dimension Style dialog box, Text tab, under Text Appearance, select a text style.

4. If the current text style does not have a fixed height, enter the height of dimension text in the Text Height box.

5. Under Tolerances, enter a height for tolerance values in the Scaling for Height box.

6. In the Offset from Dim Line box, enter a value for the gap around base dimension text.

7. Select a colour from the Text Colour box.

8. Click OK.

Create dimension objects

DIM

Draw horizontal or vertical linear dimensions.

DIM ALIGNED

Draw a linear dimension lined up with two points.

DIMANGLE

Dimension the angle between two lines.

DIMAREA

Dimension the area of a closed curve, surface, mesh, or hatch.

DIMCURVELENGTH

Dimension the length of a curve.

DIMDIAMETER

Dimension the diameter of a curve.

DIMORDINATE

Dimension the x or y distance from a base location.

DIMRADIUS

Dimension the radius of an arc or circle.

DIMROTATED

Draw a linear dimension that is rotated from the xy axis.

DIMCREASE ANGLE

Dimension the angle between two planes.

1.14 Block

Insert symbols and details into your drawings from commercial online sources

Block is a collection of objects that are combined into a single named object.

Insert a Block

Each of these blocks is an individual drawing file, saved in a folder with similar drawing files. When you need to insert one into your current drawing file, you use the INSERT command

The first time you insert the drawing as a block, you need to click Browse to locate the drawing file.

Once inserted, the block definition is stored in your current drawing.

1.15 Drawing presentation norms and standards.

You can create a standards file to define properties in order to maintain consistency throughout your drawing files.

Standards define a set of common properties for named objects such as layers and text styles

Named Objects for Standards-Checking

Layers

Text styles

Linetypes

Dimension styles

Standards File

Define standards, save them as standards file then associate the standards file with one or more drawing files. After you associate a standards file with a drawing, you should check the drawing to make sure it confirms with the standards.

How a Standards Audit Works

Check a drawing for standards violations, each named object of a specific type is checked against the standards files linked with the drawing.

A standards audit can uncover two types of problems:

An object with a nonstandard name is present in the drawing being checked.

A named object in a drawing tie the name of one in a standards file, but their properties are different.

Example: -you fix a nonstandard layer, WALL, and replace it with the standard ARCH-WALL. In this example, choosing Fix in the Check Standards dialog box transfers all objects from layer WALL to layer ARCH-WALL and then purges layer WALL from the drawing.

Standards Plug-Ins

The auditing process uses standards plug-ins, define the rules for the properties that are checked for individual named objects.

All plug-ins check all properties for each named object except for the layer plug-in.:

Colour

Linetype

Lineweight

Plot style mode

Plot style name (when the PSTYLEMODE system variable is set to 0)

The following layer properties are not checked by the layer plug-in:

On/Off

Freeze/Thaw

Lock

Plot/No Plot

References:

1. Subhash C Sharma & Gurucharan Singh (2005), “Civil Engineering Drawing”, Standard Publishers

2. Ajeet Singh (2002), “Working with AUTOCAD 2000 with updates on AUTOCAD 200I”, Tata- Mc Graw- Hill Company Limited, New Delhi

3. Sham Tickoo Swapna D (2009), “AUTOCAD for Engineers and Designers”, Pearson Education

4. Venugopal (2007), “Engineering Drawing and Graphics + AUTOCAD”, New Age International Pvt. Ltd.

5. Balagopal and Prabhu (1987), “Building Drawing and Detailing”, Spades publishing KDR building, Calicut

6. (Corresponding set of) CAD Software Theory and User Manuals.

7. Malik R.S., Meo, G.S. (2009) Civil Engineering Drawing, Computech Publication Ltd New Asian. Sikka, V.B. (2013), A Course in Civil Engineering Drawing, S.K.Kataria& Sons.

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