History of Engineering Drawing 

Technical drawing has been around since ancient times. As in the ancient Renaissance, complicated drawings were created, including Leonardo da Vinci's drawing. Modern engineering drawing, including its specific orthographic projection with scale conventions, began in Europe (France) during the early stages of Industrialization. L.T. C. Rolt also made some of Marc's drawings for its block-making machinery (in 1799) that also may have contributed significantly to British engineering technology. Since he learned the art of presenting three-dimensional(3D) items in a two-dimensional(2D) plane, as we now term mechanical drawing.  

Similar kind of study done by Gaspard Monge of Mezieres developed this in 1765 for military machinery items in England. All engineering drawings were made manually for decades, until around the post-World War II period, employing pencil and pen on paper and perhaps other substrates (such as vellum, mylar). 

With every passing decade after the advent of computer-aided design (CAD), engineering drawing has become an increasingly electronic medium. The majority of engineering drawings are now made using computer-aided design (CAD), however, pencil and paper are still used. Drafting machines are instruments that help with manual drafting by integrating technical drawing boards, straightedges, pantographs, as well as other tools into the unified technical drawing environment. Their virtual versions of any object technical drawing are provided by CAD which creates sketches that typically begin with the creation of an original, which is then copied in several copies for distribution to the sales floor, suppliers, and business records, among many other places. Engineering drawings were nowadays openly called "blueprints" or "bluelines," even though such terms appear anachronistic from a literal perspective, while most prints for engineering drawings nowadays are produced by further modern methods that generate in black or white appearances. The CAD file would be the original, as well as the printouts of such a file are the "prints" as in the case of CAD technical drawings. Mostly in the 2010s, these technical drawings have some Technical Product Specification that was updated noticeably. 

What is Engineering Drawing? 

An engineering drawing is a type of technical drawing used to express knowledge about a specific item. A detailed technical drawing is commonly used to specify the geometry required for the design of a component. Even a basic part usually necessitates a range of technical drawings to be fully defined.  

A master drawing/assembly drawing connects the sketches by providing technical drawing numbers for subsequent precise parts, quantities needed, building materials, and perhaps 3D images that may be used to identify specific items. Although the majority of the material is conveyed by pictographic depictions, acronyms and symbols can be used for brevity, however, additional textual descriptions may also be given. 

What is the meaning of "Engineering Design"?  

Engineering design is a systematic method for obtaining solutions to humanity's needs.  Drawing is the act of conceiving or inventing new ideas and expressing them with others in an easy and concise manner. Engineering drawings specify the complex characteristics of a part or assembly. The definition and interpretation of standards are governed by laws. Standardization also helps globalization so people from different countries speaking different languages can read and understand the same engineering drawing. ASME Y14.5 and Y14.5M are two major sets of engineering drawing standards that have been revised in the United States (US) since 2009, but ISO 8015 (Geometrical product requirements (GPS)) is growing rapidly in India. The Invocation Theorem was updated in 2011 to comply with ISO8015 (Geometrical Package Parameters (GPS)). Tolerance ISO8015 labelling on such a technical drawing or other specification is the best way to eliminate using the ISO GPS system which is non compulsory, thus according ISO GPS guidelines. Mostly in the United Kingdom, BS8 received major upgrades in 2010. 

Classification of Drawing 

The method of expressing ideas on paper using systematic lines. The art of representing an item on paper using systematic lines. 

Classification is as follows,

• Artistic Drawing - It’s also called Free-hand or Model Drawing. The skill of an artist representing an entity in his imagination or by holding the item in front of him. Paintings, movie posters, advertisements, and other similar items are examples. 
• Engineering Drawing - It’s also called Instrument Drawing. The art of depicting engineering objects such as structures, highways, machinery, etc. 

Types of Engineering Drawing 

i. Geometrical Drawing: This skill of technical drawing represents only geometrical things, for examples rectangle, cone, cylinder, etc. 

• Plain Geometrical Drawing: This skill of technical drawing represents only Two dimensional drawing having only length and breadth. for example triangle, square, etc. 
• Solid Geometrical Drawing: This skill of technical drawing represents only three dimensional (3D) drawing taking length, breadth and thickness, for example prism, cube, etc. 

ii. Mechanical Engineering or Machine Drawing: This skill of technical drawing represents only mechanical engineering items, for example machines and its parts, etc. 

iii. Civil Engineering Drawing: This skill of technical drawing represents only civil engineering items, for example highways, structures, dams, etc. 

iv. Electrical & Electronics Engineering Drawing: This skill of technical drawing represents only electrical and electronics items, for example electrical system diagrams, transformers etc.

Rules of Engineering Drawing 

Used Key tools and features to draw Engineering Items. 

Key tools information which is used in ED such as Straightedges, T-squares, French curves, circles, rulers, protractors, dividers, compasses, weights, erasers, and tacks or push pins are only a several of the tools used in manual drafting.  Nowadays, manual drafting also benefits from using a pocket calculator and its onscreen similarity.  Drawing boards (also known as drafting boards) and tables are, of necessity, among the instruments. Some Technical Drawing Materials and Instruments are needed for the manual drawing such as Drawing Board, Drawing Sheet, Drawing Sheet Holder, Set-Squares. 

Systems of Dimensioning and Tolerancing 

Key information such as Dimensions, for example, are normally only defined once on a technical drawing, reducing repetition and the chance of ambiguity. To enable the part to be manufactured and work, appropriate tolerances are set for critical measurements. Based on the details provided in an engineering drawing, more accurate production drawings may be created. 

All engineering drawings express not only geometry such as shape, location, and moreover proportions and tolerances for certain features with the exception of regard to views or original sketches. There have been many systems of dimensioning and tolerancing developed. The most basic dimensioning scheme simply defines distances between points (e.g., the length or width of an item, or the position of the hole centre). These lengths have been followed by plus-minus or min-max-limit tolerances since before the advent of very well compatible manufacture. Many points, lines, planes, including profiles are described in Cartesian coordinates with such a common origin in reference dimensioning. Geometric dimensioning and tolerancing, that deviates from the limits of coordinate dimensioning (for example, rectangular-only tolerance regions, and tolerance stacking) to enable the most rational tolerancing among all geometry and proportions (such that, both type [shapes/locations] as well as sizes), was developed in the post-World War II period. 

Layout of a Drawing Sheet 

An information box or title block on a drawing contains information such as who drew the technical drawing, who accepted it, the units of measurement, the significance of views, the title of the drawing, and the drawing number. Any technical drawing sheet must adhere to a certain format. Enough margins should be given on both sides of the drawing sheet as a common procedure. Drawing space and a title page should be used on the drawing board. 

• Lines : One of the most critical aspects of scientific technical drawing is lines. In order to create realistic sketches, lines are often used. Technical drawings are constructed using a variety of lines, each of which has a particular purpose. The lines are drawn in accordance with the BIS's regular conventions (SP46:2003). Curved, smooth, continuous, or segmented lines are all possible. It can be drawn as thin or as thick as you want. 
• Scales : Technology items come in a wide variety of sizes. Others are very large (e.g., Aeroplanes, missiles, etc.) and others are very small (e.g., wrist watches, MEMs components). When designing the items on paper, it is necessary to minimize or expand them. Some things can be made in their true dimensions. The size of a drawing refers to the proportion whereby the drawing of an item is expanded or diminished. The representative fraction is the proportion of a drawing's length to the total length of a thing it depicts (i.e. R.F.). This RF is used for making the drawing for big things which cannot be drawn in the paper of the sheets. 

Different types of projection are possible to use to draw ED, which is widely used all over the world. The discussion on the projection of the object and its methodology is necessary to understand the drawing (ED) and type of item. 

Types of Methods of Projection 

There are 4 types of methods of Projection described below. 

1.Orthographic Projection The projection is considered orthographic because the projectors become parallel to one another and perpendicular to the plane. Orthographic projection is used for Drafting, maps, floorplans, Technical sketches, drafting, Conceptual sketches including a set of 3 Planes found in the Orthographic Projections. The following methods are used for Orthographic Projection. 

• First-angle Projection Method (FAPM) - In First-angle projection method, Object in first quadrant Sequence following such as: Observer-Object-Plane Plane: which is recommended by BIS India. 
• Third-angle Projection Method (TAPM)- In Third-angle projection method, Object in third quadrant Sequence following such as: Observer-Plane-Object Plane: that is used in USA (1991).  

2. Isometric Projection- Isometric projection is a form of visual projection wherein the 3D of a solid is not only seen in one perspective, and also calculated directly from it. Mainly Isometric projection used for conceptual sketches, technical drawings, 3-D sketch view. 

3. Oblique Projection- Oblique projection is a basic method of graphical projection that is used to create 2D representations of 3D structures. The main type of this projection is cavalier and cabinet projection. 

4. Perspective Projection- The term "perspective projection" refers to a three-dimensional space that extends outward from the camera's position over four boundary rays.  

Applications of ED 

• Technology drawings are the only way to get knowledge from specification to production for decades. In recent decades, a new approach known as model-based definition (MBD) as well as digital product classification has emerged (DPD). 
• In MBD, the data collected by using the CAD software application has been automatically fed it into CAM application (also known as computer-aided manufacturing), that with or without post - processing apps generate code in many other languages like G-code that can be implemented by using CNC (also known as computer numerical control) machine tool, 3D printer, a hybrid machine tool which utilizes by both applications. 
• As a result, today's knowledge always flows from the designer's imagination to the assembled product without ever being codified by such an engineering drawing. The legal tool in MBD is the dataset, not a painting. 
• The expression "technical data package" (TDP) now refers to the whole package of information (in either medium) that expresses information from concept to output, for example, 3D-model datasets, engineering change orders (ECOs), engineering sketches, etc. 
• Manufacturing also necessitates CAD/CAM programmers, CNC setup staff, and CNC technicians, and also quality assurance (inspectors) and logistics personnel (i.e. for materials handling, shipping-receiving, and front office functions).  
• In the process of their work, these staff often use sketches created from the MBD dataset. When correct protocols are followed, a simple chain of precedence is often registered, so when a user gets at a sketch, she is informed that it is not the ruling instrument by a notation upon sketches as the MBD is a dataset. The sketches are still valuable in all situations, even if it is technically listed as "for comparison only," which means that if any controversies or inconsistencies occur, the MBD dataset, not the sketches, would take precedence. 

Context and Applications

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for 

• Bachelors in Technology (Mechanical Engineering) 
•  Masters in Technology (Mechanical Engineering)