Introduction to Engineering Drawing

Introduction
Drawing is the Graphical means of expression of technical details without the barrier of a language. Engineering Drawing is the Universal Language for Engineers

Communication in engineering is necessary for effectively transferring one’s ideas to others.  While communicating,  we use our memory to remember objects, sense organs to perceive objects and mind to imagine objects. Our perception are coloured or modified by our past experiences.

We see things around us, perceive the objects and identify them by their names. Later, when we hear these names we can remember these items easily and imagine various features like the shape, size, color, functions  etc,. e.g. if I say that a particular object is having the shape of a cricket bat, it is easy for a high school student to imagine the shape of the object since he has seen a cricket bat and has perceived the object. If I say that a particular object looks like the Dendrite formed during solidification of a metal, then it is difficult for the same student to imagine, since he has not seen a dendrite. His question will “how do a dendrite look like?” when we say that dendrite means tree-like structure,  his imagination can go to different types of trees, but still he may not have a clear picture of the dendrite. If we show him a picture of a dendrite, he can very easily perceive that object.

One picture/drawing is equivalent to several sentences. It is not easy for anyone to make another person understand somebody’s face just by explaining the features. Even if several sentences are used to explain the features of the face, words it would be difficult for the listener to perceive  the image of the face.  However, if you show a sketch or a photograph of the person, all these sentences can be saved. i.e., We grasp information easily if it is illustrated with diagrams, sketches, pictures, etc.

Engineering drawing
Drawings help us in developing our thoughts and ideas in to a final product. 
Drawings are also necessary for engineering industries since they are required and are being used at various stages of development of an engineering product.  Engineering drawing is completely different from artistic drawing, which are used to express aesthetic, philosophical, and abstract ideas. In an industry, these drawings help both the technical as well as commercial staffs at various stages like:

·        conceptual stage

·        design stage

·        modification stage

·        prototype development stage

·        process and production planning

·        production

·        inspection

·        marketing

·        Servicing and maintenance,  etc.

What information should be available in an engineering drawing?
A  perfect engineering drawing should have the following information:

·        Shape of an object

·        Exact Sizes and tolerances of various parts of the object

·        The finish of the product

·        The details of materials

·        The company’s name

·        Catalogue no of the product

·        Date on which the drawing was made

·        The person who made the drawing

Drawings are the road maps which show how to manufacture products and structures. No industrial level construction/manufacturing of any (man-made) engineering objects is possible without engineering drawing.

What will you learn from this course?
In this course you will learn how to communicate technical information by:
Visualization – the ability to mentally understand visual information.
Graphics theory – geometry and projection techniques used for preparation of drawings.
Use of standards – set of rules for preparation of technical drawings.
Use of conventions – commonly accepted practices in technical drawings.
Tools – devices used to create technical drawings and models.
Applications – the various uses for technical drawings.
Developing an engineering drawing can be either by manual drawing or by computer graphics

Computer has a major impact on the methods used to design and create technical drawings. The tools are Computer aided design and drafting (CADD).Design and drafting on computer are cheap and less time consuming. Then why we go for manual drawing?

Computer cannot replace the drafting board and equipment as a learning tool. In schools, students are not allowed to use calculators up to calss 12. During this period if they use calculators from class 1, they will not improve their mathematical skills. After calss 12, i.e., once they have learned the basics of mathematics, they are allowed to use calculators and computers. Hence before use of the drafting software, their fundamentals regarding drawing should be clear.  If basic fundamentals are clear, better use can be made of the power of the software. To be an expert in technical drawing, this first course on Engineering (manual) drawing is the first step.

DRAWING INSTRUMENTS AND ACCESSORIES
The following set of instruments are required for ensuring perfection in manual drawing:

1.    Drawing board

Drawing board is made of soft wooden platens.  Almost perfect planning of the working surface of the drawing board is to be ensured. A  strip of hard ebony edge is fitted up in a groove on the shorter edge of the board and perfectly lined to provide the guide for the T-square.  The standard sizes of the drawing board is shown in Table 1.1 below. D2 size of drawing board is normally recommended for the First year Engineering students.

Design of spur gear.

What Is a Gear ?

• † A gear is a toothed wheel which is used to transmit power and motion between machine parts.
• Gears are used in many applications like automobile engines,     household  appliances, industrial machine tools.
• When two gears of different sizes are meshed ,the larger is called “gear” while the smaller is “pinion”.

† Gear Tooth Terminology

Root Diameter : Diameter of root circle.

Pitch Diameter : Diameter of imaginary pitch circle specifying addendum and dedendum 

Outside Diameter : Diameter of addendum (outside) circle .

Addendum : Radial distance from pitch to top of tooth .

Dedendum : Radial distance from pitch to bottom of tooth .

Circular Pitch : Distance on pitch circle from a point on one tooth to corresponding point on the adjacent tooth .

Tooth Thickness : Thickness of a tooth along the pitch circle .

Clearance : Distance between top of a tooth and bottom of mating space .

Working Depth : Distance a tooth projects into mating space .

Whole Depth: Total height of the tooth.

†  

How To Draw a In-volute profile of the Spur Gear

The method of constructing an in-volute is illustrated as:-

These parameters are need for a in-volute gear drawing:

 Diametrical Pitch (P),Tooth (N), 'Φ' Pressure Angle (PA) in-volute spur gear.

And we need to calculate the following:

• The Pitch Diameter (D) = N/P 
• The Pitch Radius (R) = D/2 = 
• The Base Circle Diameter (BD) = D * COS (PA)
• The Base Circle Radius (BR) = DB/2 
• The Addendum ('a') = 1/P 
• The Dedendum ('d') = 1.157/P
• Outside Diameter ('OD') = D+2*a 
• Outside Radius ('OR') = .625" (R) + .0625" (a) 
• Root Diameter ('RD') = D-2*d               
• Root Radius ('RR') = .625" (R) - .0723" (d)"            

For our method we need to compute the following as well:

1. Circumference of the Base circle, (CB) = Pi * (DB) 
2. 1/20th of the Base Circle Radius, (FCB) 
3. Number of times that FCB can be divided into CB, (NCB) 
4. 360 degrees divided by NCB, (ACB) 
5. Gear Tooth Spacing (GT) = 360/T 
6. The 1/20th of the Base Circle Radius (FCB) is an arbitrary division, which yields a very close approximation; you can use whatever fraction you think will yield a good result. Now we have all our pertinent data, let's start drawing:-

• Open up your CAD program and draw concentric circles of the Pitch Diameter (D), Base Circle diameter (BD), Outside Diameter (OD), and Root Diameter (RD). Add a circle of any diameter for the bore of the gear. Make sure the circle centers are at origin.

Cycles Explaining Engine Working

Air is considered an ideal gas such that the following ideal gas relationships can be used in explanation of engine cycles:

OTTO CYCLE 

The cycle of a four-stroke, SI, naturally aspirated engine at WOT. This is the cycle of most automobile engines and other four-stroke SI engines. For analysis, this cycle is approximated by the air-standard cycle shown in . This ideal air-standard cycle is called an Otto cycle, named after one of the early developers of this type of engine. The intake stroke of the Otto cycle starts with the piston at TDC and is a constant-pressure process at an inlet pressure of one atmosphere (process 6-1 ). This is a good approximation to the inlet process of a real engine at WOT, which will actually be at a pressure slightly less than atmospheric due to pressure losses in the inlet air flow. The temperature of the air during the inlet stroke is increased as the air passes through the hot intake manifold. The temperature at point 1 will generally be on the order of 25° to 35°C hotter than the surrounding air temperature. The second stroke of the cycle is the compression stroke, which in the Otto cycle is an isentropic compression from BDC to TDC (process 1-2). This is a good approximation to compression in a real engine, except for the very beginning and the very end of the stroke. In a real engine, the beginning of the stroke is affected by the intake valve not being fully closed until slightly after BDC. The end of compres- sion is affected by the firing of the spark plug before TDC. Not only is there an increase in pressure during the compression stroke, but the temperature within the cylinder is increased substantially due to compressive heating. The compression stroke is followed by a constant-volume heat input process 2-3 at TDC. This replaces the combustion process of the real engine cycle, which occurs at close to constant-volume conditions. In a real engine combustion is started slightly bTDC, reaches its maximum speed near TDC, and is terminated a little a TDC. 

Terminology Of Internal Combustion Engine

Internal Combustion 

Spark Ignition (SI)

An engine in which the combustion process in each cycle is started by use of a spark plug. 

Compression Ignition (CI) 

An engine in which the combustion process starts when the air-fuel mixture self-ignites due to high temperature in the combustion chamber caused by high compression. CI engines are often called Diesel engines, especially in the non-technical community.

Top-Dead-Center (TDC)

Position of the piston when it stops at the furthest point away from the crankshaft. Top because this position is at the top of most engines (not always), and dead because the piston stops at this point. Because in some engines top-de ad-center is not at the top of the engine (e.g., horizon- tally opposed engines, radial engines, etc.), some Sources call this position

Head-End-Dead-Center (HEDC)

Some sources call this position Top-Center (TC). When an occurrence in a cycle happens before TDC. When the occurrence happens after TDC. When the piston is at TDC, the volume in the cylinder is a minimum called the clearance volume. 

Fundamentals of Internal Combustion Engine

 INTRODUCTION

The internal  combustion engine is a heat engine that convert  chemical energy in a fuel into mechanical  energy, usually made available on a rotating output shaft. Chemical energy  of the fuel is first converted  to thermal energy by means of com- bustion  or oxidation  with air inside the  engine.This  thermal energy raises the temperature and pressure  of the gases within the engine, and the high-pressure gas then  expands  against  the mechanical  mechanisms  of the engine.  This expansion  is converted  by the mechanical  linkages of the engine to a rotating crankshaft,  which is the  output  of the  engine.  The  crankshaft,   in turn,  is connected  to a transmission and/or  power  train  to transmit  the rotating  mechanical  energy  to the  desired  final use.

EARLY HISTORY

During 19th century,different internal combustion engines were built and tested.The first fairly practical engine was invented by J.J.E. Lenoir (1822-1900) and appeared about in 1860.

lenoir Engine

During the next decade,Engines were built with power up to about 4.5 kW (6 hp) and mechanical efficiency up to 5 %.In 1867 the Otto-Langen engine, with efficiency improved to about 11%, was first introduced, and several thousand of these were produced during the next decade. This was a type of atmospheric engine with the power stroke propelled by atmospheric pressure acting against a vacuum. Nicolaus A. Otto (1832-1891) and Eugen Langen (1833-1895) were two of many engine inventors of this period. During this time, engines operating on the same basic four-stroke cycle as the modern automobile engine began to evolve as the best design. Although many people were working on four-stroke cycle design, Otto was given credit when his prototype engine was built in 1876. In the 1880s the internal combustion engine first appeared in automobiles. Also in this decade the two-stroke cycle engine became practical and was manufactured in large numbers. By 1892, Rudolf Diesel (1858-1913) had perfected his compression ignition engine into basically the same diesel engine known today. This was after years of development work which included the use of solid fuel in his early experimental engines. Early compression ignition engines were noisy, large, slow, single-cylinder engines. They were, however, generally more efficient than spark ignition engines. It wasn't until the 1920s that multi-cylinder compression ignition engines were made small enough to be used with automobiles and trucks.

 Classification of Engine.


Internal  combustion  engines can be classified in a number  of different  ways:

History of BMW

BMW:  Bayerische Motoren Werke (OR) English - Bavarian Motor Works

The Founder of BMW  - Karl Friedrich Rapp

   BMW is a German auto mobile company. BMW is a Motorcycle and engine manufacturing company founded in 1916. BMW headquarter in Munich, Bavaria, Germany.  In 2012, the BMW Group produced 1,845,186 automobiles and 117,109 motorcycles across all of its brands. BMW is part of the "German Big 3" luxury automakers, along with Audi and Mercedes-Benz, which are the three best-selling luxury automakers in the world.

   BMW AG is a German company and one of the leading manufacturers of automobiles and motorcycles in the world. Founded in 1916 and based in Munich (state capital of Bavaria), Germany, BMW is also the parent company of the MINI and Rolls-Royce car brands. BMW AG stands for Bayerische Motoren Werke Aktiengesellschaft, or Bavarian Motor Works.

1922 - After the end of the war, railway brakes and inboard engines were manufactured following the prohibition on the production of aero-engines. After the company was sold to Knorr Bremse AG in 1920, financier Camillo Castiglioni acquired engine production along with the workforce and production facilities. That same year the company relocated to the production facilities of BFW at Munich’s Oberwiesenfeld airfield. 

1923 - BMW announced its first motorcycle, the R 32, in 1923. Until then the company had only supplied engines rather than complete vehicles. The basic concept of the original BMW Motor rad model – a boxer engine with longitudinally positioned cylinders and shaft drive – is so sound, that it continues to be employed in the company’s motorcycles to this day.

OVERVIEW OF CAD/CAM

What is computer Aided Design (CAD) ?   CAD or computer aided design defined in many methods and includes a  variety of activities.  It can be said to be the integration of computer   software techniques in engineering design. At  end when we talk of modelling, it emphasis on the following: 1.)Use of computer for  product design. 2.)Numerical methods, optimizations technique etc. 2-D/3-D drafting 3.)3-D modeoling for visualization of product. 4.)Modelling curve, surface, solid, mechanisms, assembly, etc. The model then developed is first visualize on  monitor using a variety of techniques including shaded images displays, hidden surfaces removed displays  etc. Once the product designer is convinced, then  model is then move to next step for many types of analysis softwares. thus, at the end it include various steps of analysis  processes. These could be following- 1.)Stress or deflection simulation, i.e. numerical method meant for estimation of the behavior of product with respect to given parameters. It includes software tools like the Finite Element Method (FEM). 2.)Simulation softwares of actual use 3.)Optimization softwares Other applications like 1.)CAD/CAM integrations 2.)Process planning methods These are processes which usually use model developed using CAD softwares. They all use CAD models and often the kind of application they have to be used in a determines the kind of model to be developed.  Thus there are these following aspects to CAD. 1.)Modelling of product. 2.)Display/ Visualization of product. 3.)Applications of product. MODELING   Modelling typically includes a set of processes like 1.)Defining object. 2.)Defining relations between objects. 3.)Defining properties of object. 4.)Defining the orientations of the object in suitable coordinate system 5.)Modification of existing definitions or editing. The figure below explains what a typical CAD models would need to be defined, what kind of entity need to be defined  and what relationships exist .

Design of Flywheel

Flywheel

 A flywheel is an inertia energy-storage member of engine. It absorb mechanical rotational energy and serves as a energy reservoir, storing energy during the power stroke when the supply of energy is more than the requirement and releases it during the idle stroke when the requirement of energy is more than the supply. 

Flywheels Function need and Operation 

The main function of a fly wheel is to smoothen out variations in the speed of a shaft caused by torque fluctuations. If the source of the driving torque or load torque is fluctuating in nature, then a flywheel is usually called for. Many machines have load patterns that cause the torque time function to vary over the cycle. Internal combustion engines with one or two cylinders are a typical example. Piston compressors, punch presses, rock crushers etc. are the other systems that have fly wheel. Flywheel absorbs mechanical energy by increasing its angular velocity and delivers the stored energy by decreasing its velocity.

What is Powder Metallurgy( PM) ?

Powder Metallurgy is one of the continuously and rapidly evolving technology relating with most metallic and alloy material, and a wide range of shape and sizes. Powder Metallurgy is a very developed way of manufacturing reliable ferrous and non-ferrous products. The Europe Market single-handed has an annual turnover of over Six Billion Euro, with annual metal powder production exceeding one million tons.

Created by mixing elemental or alloy powders and compacting the mixture in a die, the resultant shapes are then heated or "sintered" in a controlled atmosphere furnace to bond the particles metallurgical. The high precision forming capability of PM generates components with near net shape, intricate features and good dimensional precision pieces are often finished without the need of machining.

By producing parts with a homogeneous structure the PM process enables manufacturers to make products that are more consistent and predictable in their behavior across a wide range of applications. In addition the PM Process has a high degree of flexibility allowing the tailoring of the physical characteristics of a product to suit your specific property and performance requirements. These include:

§  Structural pieces with complex shapes

§  Controlled Porosity

§  Controlled performance

§  Good performance in stress and absorbing of  vibrations

§  Special properties such as hardness and wear resistance

§  Great precision and good surface finish

§  Large series of pieces with narrow tolerances

The unique flexibility of the PM process enables products to be made from materials that are tailored to your specific needs. By using specially selected materials this capability enables refinements to be engineered into the mechanical properties of the part.

Top mechanical CAD software Tools

Here is the list of CAD softwares that are focused mainly on mechanical design and parametric modeling. Although majority of the mechanical CAD market share is dominated by Autodesk, PTC, Dassault and Siemens, there are many other small and medium scale CAD packages which are very useful and economical for small industries. It is important that you invest on the right CAD package. So lets see some of the CAD softwares that are available for mechanical stream.

If you think of mechanical CAD, the first thing that comes in your mind is AUTOCAD. AUTOCAD is developed and distributed by AUTODESK INC. This CAD software is mainly used for creating 2D drawings although it can be used for 3D modeling. In my opinion, 3D modeling is not that user friendly but when it comes to 2D drafting it is the best software available compared to others.

Autodesk Inventor is developed and distributed by AUTODESK INC. It directly competes with major 3D CAD modeling softwares like Creo, NX, Catia, Solid works etc. 

Creo parametric formally known as Pro Engineer is developed and marketed by Parametric Technology Corporation (PTC). It is a CAD/CAM/CAE supported software. Pro Engineer was the first mechanical CAD software to bring parametric feature based 3D modeling. Recently Pro Engineer was replaced by Creo parametric series. Easy user interface and powerful modeling options are advantages here. Creo can be easily configured with Windchill (PLM). 

Catia is developed and marketed by French company Dassault Systems and has CAD/CAM/CAE support. It is one of the major CAD software in mechanical domain. It directly competes with Creo, NX and Inventor and is particularly used in industries where rich surface modeling is needed such as Aerospace, Automobiles etc. 

NX (UG or Unigraphics) is also one of the major mechanical CAD software which is developed and marketed by Siemens. Being CAD/CAM/CAE software, it is rapidly growing because it has an advantage of easy configuration with Teamcenter (PLM) which is developed by the same company. Teamcenter is already an established PLM software in many industries and domains.

Solid Edge is developed and marketed by Siemens. It is the lower end software which only includes CAD. All other major softwares Creo, Catia, NX are CAD/CAM/CAE softwares. It is economical and user friendly compared to NX and used in many small scale industries.

Solidworks is a direct competitor of  Solid edge. It is economical and user friendly. It is developed by Dassault Systems. It is a major software and used by many companies.

Draftsight is 2D drafting and editing software for DWG and DXF files. It is similar like AutoCAD 2D and is completely free. 

Cobalt is a very powerful economical 2D/3D CAD software. It has advanced modeling features and has many modules including surface modeling, Animations and rendering etc.. It has a huge mechanical parts library. It uses parametric modeling.

Vectorworks fundamentals is 2D/3D mechanical CAD software which is a part of Vectorworks suite.

HiCAD is an other 2D/3D CAD software. It is very economical and has many features in its class. 

VariCAD is another powerful 2D/3D mechanical CAD software which includes crash tests, calculations etc.

QCAD is a 2D drafting software and is economical.

Sketchup is developed and marketed by Google INC. It uses pull, move, fill, and combine techniques for modeling and uses basic geometric primitive shapes. Although it is mainly used for layout drawings and it can be used for mechanical design. The basic version is free. 

These are the top mechanical cad software in the market