Introduction to graphics communications and drawing standards In engineering, 92% of the design process is graphically based. Another 8% percent:

mathematics,

written and

verbal communications.

The reason: graphics serves as the primary means of communication for the design process.

Even more – not only for design:

Product Lifecycle Management (PLM) software (CAD s/w) allows to integrate data management of

computer-aided design,

manufacture,

test,

analysis, and

sharing of best practice,

for increasingly extended supply chains.

The idea here: to have a digital model shared by partners internally and externally, with ready access to CAD

models, changes, specifications, purchasing and related documents, through the product lifecycle.

Design collaboration from an early stage can prevent costly mistakes.

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PLM brings together all information about a product, how it was made and how it is used.

Extremely important place here belongs to the Engineering Graphics.

Why?

Engineering graphics is a real and complete language used in the design process for:

Drafting and documentation, along with design modeling, comprise over 40 percent of the engineer's time and are purely visual and graphical activities.

Engineering analysis depends largely on reading engineering graphics.

Manufacturing engineering and functional design also require the production and reading of graphics.

Engineering graphics can also communicate solutions to technical problems. Such engineering graphics are produced according to certain standards and conventions so they can be read and accurately interpreted by anyone who has learned those standards and conventions.

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Very important concept in graphics communications is drawing – a graphical representation of objects and structures which is done using freehand, mechanical, or computer methods.

Technical drawing is used to represent complex technical ideas with adequate precision for the product to be mass-produced and the parts to be easily interchanged.

Technical drawing tools (traditional & modern) Technical drawings are created using a variety of instruments, ranging from traditional tools, such as pencils, compass, and triangles, to the computer.

Traditional drawing instruments are still important, especially for sketching; today, however, the computer can be used for most drawing and modeling purposes.

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Computer-aided design/drafting (CAD) is now the standard.

CAD/CAM/CAE – Computer Aided Design/Manufacturing/Engineering

DMU – Digital Mock-Up

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A CAD system consists of hardware devices used in combination with specific software. The hardware for a

CAD system consists of the physical devices used to support the CAD software.

Software comprises the written and coded instructions that govern the operation and the functions of the computer.

CAD software:

* AutoCAD (Autodesk)

* Pro/ENGINEER (PTC)

* SolidWorks (Dassault Systems)

* Solid Edge (UGS PLM)

* CATIA (Dassault Systems)

* Unigraphics (UGS PLM)

* Inventor (Autodesk)

* IronCAD

* IDEAS (UGS PLM)

etc.

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Main components of CAD workstation:

The central processing unit (CPU) – runs the PC

programs and controls the input/output devices.

Display – an output device, through which

information flows from the computer out to the user.

In a CAD system, the display device can be thought

of as the drawing paper upon which technical

drawings and models are produced.

The output devices used to make hard copies of the drawings created on screen are categorized as:

printers, plotters, or film recorders.

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Input devices transmit information flows from the user into the computer:

A scanner is used for converting a

drawing created with traditional tools to a

CAD drawing.

The keyboard is used to input

alphanumeric data and to make

CAD menu selections.

The mouse is used to control cursor

movement and to make menu selections.

A tablet is an input device for entering

graphical information.

A storage device is used to store information on a specific medium and retrieve that information as needed.

Storage devices are usually

o fixed (the hard disk inside computer), or

o removable (Zip disks, floppy disks, CDs and DVDs, flash drives).

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National Standard of Canada and other standards

All engineering drawings should be created according to the conventions. Conventions are commonly accepted

practices, rules, or methods used in technical drawing.

Standards are sets of rules that govern how technical drawings are represented. Standards allow for the clear

communication of technical ideas.

In Canada the top body in standartization is the Canadian Standartization Agency (CSA). The main standard for the

drawing preparation is CAN3-B78.1-M83 Technical Drawings – General Principles.

The Canadian standards closely correlate with those of the United States.

In the United States, the American National Standards Institute (ANSI) is the governing body that sets the

standards used for engineering and technical drawings. Other professional organizations, such as the American

Society for Mechanical Engineering (ASME), assist ANSI in developing technical graphics standards.

ANSI standard = ASME standard.

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Fundamentals of Graphics Communication, Gary R. Bertoline and Eric N. Wiebe, McGraw Hill, Fourth edition. Engineering Drawing and Design, Cecil Jensen, Jay D. Helsel, and Dennis R. Short, McGraw Hill, Sixth edition.

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CAN3-B78.1-M83 - Scope and Introduction

This Standard is intended to cover the field of technical drawing practice. It applies primarily to "end-

product" drawings, which usually consist of detail drawings, and assembly or subassembly drawings.

All linear dimensions in this Standard are shown in millimetres (mm) unless otherwise indicated.

Another important Canadian Standard is CAN/CSA-B78.2-M91 Dimensioning and Tolerancing of Technical Drawings

Example of dimensioned mechanical

drawing using ASME Y14.5M-1994

and CSA M83/M91 standards.

In the following lectures we will get

acquainted with the main rules and

principles of drawing preparation

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Standard sheet sizes & inside borders First of all we will consider the Drawing Sizes, Format, Title Blocks, etc.

Standard Sheet Sizes

Table 1 shows the dimensions of P Series drawing sheet sizes and Table 2 shows the dimensions of A Series

and Bl drawing sheet sizes. The most commonly used smallest format is A4.

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The following figure clarifies the terms used in the tables.

The Inside border encloses the working area, including the title block and other tables. The border shall be 20 mm wide on the binding edge and 10 mm wide on the other three sides, with resulting working area sizes as shown in Tables 1 and 2.

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A general format for drawings is shown in figure below, which shows a drawing trimmed to size. It is

recommended that pre-cut and printed drawing forms be made to the trimmed size.

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Title blocks are used to record all the important information necessary for the working drawings.It contains general as well as specific information.

The data may refer to company policy or to the drawing. The form and information vary from company to company. A company that produces large castings, as an example, may have different notes than a company that makes small tools and dies.

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The title block is normally located in the lower right corner of the drawing sheet.

Though the arrangement and size of the title block is optional, the following information is considered

mandatory:

Drawing number;

Title of the drawing or description;

Name of firm or organization;

Original scale;

Specifications & notes area;

Drafter name area.

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Besides this data title blocks may contain the following:

• Design approval, when subcontractors are used.

• Federal supply code for manufacturers (FSCM) number.

• Drawing sheet size letter designation.

• Actual or estimated weight of the item.

• Sheet number, if there are multiple sheets in the set.

• Date of issue.

• Signatures.

• Professional seals.

• Job, order or contract number.

• References to this or other documents.

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Change or Revision Table.

All drawings shall carry a change or revision table, preferably on the right-hand side or across the

bottom of the drawing. In addition to a brief description of drawing changes, provision may

be made for recording a revision symbol, zone location, issue number, date, and approval of the

change. Typical revision tables are shown here:

Left figure – Vertical Revision Table, placed by the right vertical borderline.

Right figure – Horizontal Revision Table, placed at the bottom of the drawing, on the left from the

title block.

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Folding of reproductions To facilitate handling, mailing, and filing, reproductions should be folded in such a way that the title block

and auxiliary number will always appear on the front face, and the last fold will always be at the top.

In filing, this prevents other drawings from being pushed into the folds of filed reproductions.

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Reproductions larger than size

A2 are folded in vertical folds,

then folded at two-thirds of

width from the lower edge, and

finally at one-third of width, as

illustrated for size Al.

To avoid loss of clarity by frequent folding, important details should not be drawn in close proximity to fold

areas.

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Drawing titles The proper selection of drawing titles is very important. A drawing title

should be as brief as possible,

should describe the item depicted, and

should distinguish between similar items.

Two part titles Drawing titles may be in two parts.

a) The first part of the title shall be the item name, which may consist of a noun or noun phrase

and suitable modifiers.

The noun or noun phrase shall describe the item and the use of the item, but not the material or

method of fabrication.

The terms CASTING, FORGING, WELDED, MACHINING, etc. shall not be used in the noun

phrase.

Examples:

Noun and noun phrases: COVER. IMPELLER MAGNET HOUSING. 3/4x2 SHOULDER SCREW.

Noun phrase with modifier: CABLE ASSEMBLY, SPECIAL PURPOSE.

b) The second part shall consist of any additional modifiers necessary to distinguish between items

having the same name. The second modifier must always express a different characteristic from

the first modifier.

Example: GEAR, SPUR, 80 TOOTH.

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General rules The following general rules should be observed in selecting the first part of a title:

(a) The conjunction “or” and the preposition “for” shall not be used.

Not acceptable: CRANK FOR BRAKE

Acceptable: BRAKE CRANK

(b) No abbreviation of any portion of the item name (first part of title) shall be made, except those

necessarily used for trademarked names, and the words ASSEMBLY (ASSY), SUBASSEMBLY

(SUBASSY), and INSTALLATION (INSTL).

Not acceptable: IR PUMA 560

Acceptable: Industrial Robot PUMA 560

Acceptable: SCARA Robot

c) An ambiguous noun or one that designates several classes of items shall not be used alone or as a

modifier, but shall be used as part of a noun phrase.

Acceptable: JUNCTION BOX WIRING HARNESS

Not Acceptable: JUNCTION HARNESS, WIRING, BOX

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Lettering & numbering The most important requirements for lettering are legibility, reproducibility, and ease of execution.

These are particularly important due to the increased use of microfilming, which requires optimum

clarity and adequate size of all details and lettering.

It is recommended that particular attention be paid to the avoidance of the following common faults:

• Unnecessary fine detail (simple lettering & numbering);

• Poor spacing of details (distinguished letters & numbers);

• Carelessly drawn numerals and letters (legible letters & numbers) ;

• Inconsistent delineation (uniformity of style);

• Incomplete erasures, leaving ghosted images (clean area around letters & numbers);

• Use of different densities, such as pencil, ink, and typescript on the same drawing (uniformity of

appearance).

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Gothic lettering The standard requirements are best met by the style of lettering known as single stroke Gothic. Though

different companies and industries may use different computer lettering styles, Single Stroke Gothic is still the ANSI

and CSA standard. (In AutoCAD, the closest equivalent is Roman Simplex).

An example of hand-lettered Gothic text style commonly used in engineering drawings. Upper case, vertical lettering is preferred, except for SI symbols such as mm, m and km, for which lowercase is required.

Examples of Gothic lettering.

Standard Gothic

Microfont, a Gothic lettering style recommended

by the USA National Microfilm Association, also

meets these requirements.

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Size Minimum lettering size for dimensions and notes is 3.5 mm. Recommended character heights "h" and

character line thicknesses "d" in millimetres are shown in the Table.

For drawings size Al and larger, the recommended character height "h" is 7.0 (minimum 5.0). For very large

drawings it may be desirable to use a character height "h" of 10 or greater. Larger characters should be

used for drawing titles and numbers, and it is permissible to use smaller letters (2.5) in the revision table.

Letters with serifs In cases where confusion may arise between

alphabetics and numerics, such as in code numbers, it

is recommended that the serifs or identifying marks

be added:

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Introduction to CAD lettering technique

1. Text is added to a CAD drawing by selecting the TEXT command, entering the letters and numerals with the keyboard, and then picking a point on the drawing where the text is to be placed.

2. Before adding text to a drawing, many variables must be set. Some of the more common computer text variables are height, font, alignment, aspect ratio, slant, and rotation.

3. Although some CAD software makes it easy to use different fonts, technical drawings that adhere to ANSI standards should always use the block Gothic style, for maximum clarity when reproducing technical drawings.

4. Text alignment controls the justification of a line of CAD text. Typical alignments are center, left, and right.

Center justification centers the text about a

selected point, which is indicated by the X in the

Figure A.

ation places the text flush left with a Left justific

margin and results in a ragged right margin

(Figure B).

ation places the text flush right with Right justific

a margin and results in a ragged left margin

(Figure С).

Some CAD systems provide even more precision in placing text, using the following: ■ Top center ■ Top left ■ Top right ■ Middle center

■ Middle left ■ Middle right ■ Bottom center ■ Bottom left

■ Bottom right

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Scaling All drawings should be drawn to scale, and the denomination of the used scale should be shown in the title block

of the drawing.

If a drawings has details drawn larger than full size, it should, where practicable, include an undimensioned view

drawn to actual size. This view may be an axonometric projection or may be simplified by showing only the outlines

of the object.

If most features of the drawing are not drawn to scale, the abbreviation NTS must be shown in the scale space in the

title block.

Recommended Scale. Drawings should be full scale (1:1) whenever practicable, but when other scales are necessary

the recommended scales for use on technical drawings are specified in the Table.

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Where it is necessary to use more than one scale on a drawing, the main scale only should be inscribed in the title

block. All other scales should be shown near the detailed drawing.

Wrong scale, but correct placement!

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Another example of wrong scaling:

Correct scale 3:1

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A convenient practice consists in drawing the layout of the centre lines of the members to one scale and

superimposing the details to a larger scale on the points of intersection of the centre lines.

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Notes Notes are used to simplify or complement the graphic presentation by indicating information on a drawing in a

condensed and systematic manner. Types of notes: general or local.

General rules for all types of notes

Requirements

Notes should

• be stated in the present tense, and

• be in either imperative or permissive mood as required.

Avoid

• Lengthy,

• complex, or

• indefinite notes.

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General Notes are notes that refer to the part or the drawing as a whole.

Such notes should be shown in a central position below the view to which they apply, or in a general note column.

Typical examples

of general notes:

a) FINISH ALL OVER 6.3

(Note: Roughness in μin.)

b) ALL FILLETS R4;

c) TOLERANCES APPLY

AFTER PLATING.

Reference to a general note on the drawing may be shown adjacent to a dimension, or connected by a leader to the

applicable feature, or indicated by the word NOTE and its number in parenthesis, for example: Ø15 (NOTE 2).

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Local notes apply to local requirements only, and are connected by a leader to the feature to which the

note applies.

Typical examples of local notes: a) Ø 4 HOLES; 9.71

9.56

b) CBORE Ø6 x 4 DEEP;

c) CHAM 2 x 45°.

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