Posted by: mmeazaw | January 4, 2011

What is Engineering Design?

Haresh Khemani

There are various branches of engineering like Mechanical, Automobile, Civil, Electrical, Chemical, Electronics, Telecommunications, Computer, IT, Petroleum etc. At the heart of all the applications of various branches of engineering is Engineering Design. Let us see what engineering design is.

Importance of Engineering

Engineering is one of the most important fields discovered by the human beings. Almost all the applications being used by the human beings have engineering background in some or the other way. There are various branches of engineering like Mechanical, Automobile, Civil, Electrical, Chemical, Electronics, Telecommunications, Computer, IT, Petroleum and many others.

Some branches of engineering are core branches like Mechanical, Civil, Electrical etc for without them the progress of the humankind is unthinkable. Then there are some branches like Electronics, Telecommunications, Computer etc that are applications intensive and they increase the productivity and efficiency of the human brain.

Different branches of engineering have different applications. For instance the applications of mechanical engineering are automobiles, refrigerators and air-conditioners, various types of machines like milling, drilling, lathe etc, various types of appliances and much more. Some applications of electrical engineering are power supply systems in the big industries, domestic power supply systems, transformers etc. Some applications of chemical engineering are various chemicals like caustic, HCL acid, fertilizers, etc. Some applications of electronics engineering are various appliances like television, lights, washing machines, dishwashers etc.

What is Engineering Design?

At the heart of all the applications of various branches of engineering is Engineering Design. To understand its importance let us for example consider a car. If the new car is to be manufactured, the manufacturing engineer just cannot manufacture the car haphazardly on his or her own. It’s not like say last night the manufacturing engineer dreamt of the car and next day the production started. The most important part before manufacturing the car is designing the car. The car has to be designed to give it particular shape considering the aesthetics, ergonomics, costs, safety, security etc. It cannot be designed all at once rather various iterations are carried out that means if one option is not suitable the other is considered. The iterative design and calculations will keep on going unless the beautiful looking car with all the modern facilities that can be made available at affordable costs to the potential customers has been designed. Manufacturing the car will be the last step.

Thus designing is the most crucial part of any branch of engineering. Engineering Design can be defined as the iterative decision making process which creates the plans to convert resources optimally into systems, processes or devices so as to perform the desired functions and meet the needs of the humans. In brief, in engineering design we first consider various resources available and then make plans to convert these resources into suitable systems, processes or devices to meet certain functional and human needs by making the best use of the resources at the lowest possible cost.

The main aim of the engineering design course is to help the students apply knowledge that they have gained from their studies in science, engineering, social studies, and humanities to the solution of the practical engineering problems. The object of Engineering Design course is not to teach the new engineering course, rather it is to help the students utilize purposefully and effectively whatever they have they have already learnt.

What is Mechanical Design or Machine Design?

What is Machine Design

Mechanical Design or Machine Design is one of the important branches of Engineering Design. To understand what exactly machine design or mechanical design is let us consider the example of the gear box of the car. The gear box transmits the motion and the power of the engine to the wheels of the vehicle. The gearbox comprises group of gears which are subjected to not only motion but also the load of the vehicle. For the gears to run at desired speeds and take desired loads it is important that they should be designed. During designing various calculations are performed considering desired speeds and loads and finally the gear of particular material and specific dimensions that can take all loads and that can be manufactured at least possible cost giving optimum performance is designed. In similar fashion all the components of the car, including engine, have to be designed so that they optimally meet all the functional requirements at lowest possible cost. This whole process of designing is called as machine design or mechanical design.

Machine Design or Mechanical Design can be defined as the process by which resources or energy is converted into useful mechanical forms, or the mechanisms so as to obtain useful output from the machines in the desired form as per the needs of the human beings. Machine design can lead to the formation of the entirely new machine or it can lead to up-gradation or improvement of the existing machine. For instance if the existing gearbox is too heavy or cannot sustain the actual loads, entirely new gearbox can be designed. But if the same gearbox has the potential to lift more loads, it can be upgraded by making certain important changes in its design.

The Purpose of Machine Design Course

The course in Machine Design help students understand the fundamentals of designing the most commonly used parts, elements and units of various machines. Small components of machine on assembling make a big machine, hence the machine as a whole as well as its individual components have to be designed.

The knowledge of machine design helps the designers as follows:

1) To select proper materials and best suited shapes,

2) To calculate the dimensions based on the loads on machines and strength of the material,

3) Specify the manufacturing process for the manufacture of the designed component of the machine or the whole machine.

Machine Design is the application of: mathematics, kinematics, statics, dynamics, mechanics of materials, engineering materials, mechanical technology of metals and engineering drawing. It also involves application of other subjects like thermodynamics, electrical theory, hydraulics, engines, turbines, pumps etc. Machine drawing is the integral part of the machine design, since all the components or the machines that have been designed should be drawn to manufacture them as per the specifications. Without machine drawing the subject of machine design is incomplete.

What is a Machine?

Machine design is an important part of engineering applications, but what is a machine? Machine is the devise that comprises of the stationary parts and moving parts combined together to generate, transform or utilize the mechanical energy. All the machines are made up of elements or parts and units. Each element is a separate part of the machine and it may have to be designed separately and in assembly. Each element in turn can be a complete part or made up of several small pieces which are joined together by riveting, welding etc. Several machine parts are assembled together to form what we call as complete machine.

Here are some examples of the machines:

1) Lathe: It utilizes mechanical energy to cut the metals. The other types of machine tools also perform the same task.

2) Turbines: They produce mechanical energy.

3) Compressors: They use mechanical energy to compress the air.

4) Engines: They consume the fuel and produce mechanical energy.

5) Refrigerators and air-conditioners: They use mechanical engineering to produce cooling effect.

6) Washing machines: They use mechanical energy to wash the clothes.

Classification of Machines

Considering the various applications of the machines, they are classified into three main types, these are:

1) Machines generating mechanical energy: The machines generating mechanical energy are also called as prime movers. These machines convert some form of energy like heat, hydraulic, electrical, etc into mechanical energy or work. The most popular example of these machines is the internal combustion engine in which the chemical energy of the fuel is converted into heat energy which in turn is converted into mechanical work in the form of the rotation of the wheels of the vehicle. Some other examples of this group of machines are gas turbines, water turbines, steam engine etc.

2) Machines transforming mechanical energy: These machines are called converting machines because they convert mechanical energy into other form of energy like electricity, hydraulic energy etc. Some examples of these machines are electric generator in which the rotation of the shaft is converted into electrical energy, and hydraulic pump in which the rotation energy of the rotors is converted into the hydraulic energy of the fluid.

3) Machines utilizing mechanical energy: These machines receive mechanical energy and utilize it for various applications. Some examples of these machines are lathe machine that utilizes the mechanical energy to cut metals and washing machine that utilizes the rotation of the rotor for washing the clothes.

What are Machine Elements?

All the machines are made up of elements or parts and units. Each element is a separate part of the machine and it may have to be designed separately and in assembly. Each element in turn can be a complete part or made up of several small pieces which are joined together by riveting, welding etc. Several machine elements are assembled together to form what we call as complete machine, which performs various applications.

Classification of Machines Elements

The machines elements are classified into two main types: general purpose elements and special purpose elements. These have been described below:

1) General purpose elements: The elements which are common to various types of machines serving different applications are called general purpose elements. Examples of these elements are nuts, bolts, keys, axles, shafts, couplings, bearings etc.

2) Special purpose elements: The elements that are used only in the specific type of machine are called as special purpose elements. For instance piston and connecting rods are used in the engines and compressors, while blades are used in the turbines and blowers. Some other examples are cam shafts, push roads, crankshaft, cylinder etc.

Types of General Purpose Elements

The general purpose elements, which are common in all types of machines, are classified into two types: fasteners and elements of rotary motion drive. These are described below:

1) Fasteners: The fasteners are the machine elements that connect or join various parts of the machine. The joints can be of permanent type or temporary type. The permanent joints are the ones that cannot be separated or disassembled into individual elements without destroying or damaging them. The examples of permanent joints are welded joints, riveted joints etc. The temporary joints are the ones in which the individual elements of the assembly can be separated easily without destroying or damaging them. The joints obtained by nut and bolt, and the cotter joints are common and widely used examples of the temporary joints.

2) Elements of rotary motion drive: These are the elements that help transmit the motion or power to or from the machines. For example belt connected to the motor and pump helps running the pump. The fear box helps transmit the motion and power from the engine to the wheels of the vehicles. Other examples of elements of the rotary motion drive are rope, chain, gear, worm drives, shafts, axles, couplings, bearings etc.

Machine Design Procedure

There is no fixed machine design procedure for when the new machine element of the machine is being designed a number of options have to be considered. When designing machine one cannot apply rigid rules to get the best design for the machine at the lowest possible cost. The designer who develops the habit of following a fixed line of steps for designing the machine or machine elements cannot come out with the best product. When the new product is to be developed the problems keep on arising at design stage, and these can be solved only by having flexible approach and considering various ways.

Important Steps of Designing Machine

Though the machine design procedure is not standard, there are some common steps to be followed; these can be followed as per the requirements wherever and whenever necessary. Here are some guidelines as to how the machine design engineer can proceed with the design:

1) Making the written statement: Make the written statement of what exactly is the problem for which the machine design has to be done. This statement should be very clear and as detailed as possible. If you want to develop the new produce write down the details about the project. This statement is sort of the list of the aims that are to be achieved from machine design.

2) Consider the possible mechanisms: When you designing the machine consider all the possible mechanisms which help desired motion or the group of motions in your proposed machine. From the various options the best can be selected whenever required.

3) Transmitted forces: Machine is made up of various machine elements on which various forces are applied. Calculate the forces acting on each of the element and energy transmitted by them.

4) Material selection: Select the appropriate materials for each element of the machine so that they can sustain all the forces and at the same time they have least possible cost.

5) Find allowable stress: All the machine elements are subjected to stress whether small or large. Considering the various forces acting on the machine elements, their material and other factors that affect the strength of the machine calculate the allowable or design stress for the machine elements.

6) Dimensions of the machine elements: Find out the appropriate dimensions for the machine elements considering the forces acting on it, its material, and design stress. The size of the machine elements should be such that they should not distort or break when loads are applied.

7) Consider the past experience: If you have the past experience of designing the machine element or the previous records of the company, consider them and make the necessary changes in the design. Further, designer can also consider the personal judgment so as to facilitate the production of the machine and machine elements.

8) Make drawings: After designing the machine and machine elements make the assembly drawings of the whole machines and detailed drawings of all the elements of the machine. In the drawings clearly specify the dimensions of the assembly and the machine elements, their total number required, their material and method of their production. The designer should also specify the accuracy, surface finish and other related parameters for the machine elements

Skills a Good Machine Designer should possess


Machine designer is the one who designs the machine and its various elements. A good machine designer possesses some skills that help him/her design the machine elements and machine that meet all the needs of the designer and that helps develop the high quality machine at lowest possible costs. These skills help the machine design engineer consider all the relevant parameters in the broad sense and understand their effects on machine. The good designer has knowledge of wide range of subjects related to the machine that helps them find out the best solution to the problem. Their communications skills help them communicate their problem to others and get find the solution of the problem from different sources.

Some Important Skills the Machine Designer should possess

Here are some important skills that a good machine designer should possess.

1) Inventiveness: This skill is the foundation stone for a good machine design engineer. Any new design starts with the need or some objective. A good designer should have inventiveness, which is the ability to think of or discover valuable and useful ideas or concepts for the things or processes to achieve the given objective. Without inventiveness the designer cannot start the process of machine design.

2) Engineering analysis: Engineering analysis is the ability of the designer to analyze the given component, system or the process using engineering and scientific principles. The designer who possesses this skill will be able to find answer to the engineering related problems very quickly for he or she knows what exactly the problem is and where it is.

3) Engineering science: This is another skill without which the designer will just not be able to do any designing. A good designer is the one who has thorough knowledge of and in depth training in the engineering science in which they are doing designing. For instance, if the person doesn’t know what the refrigerator is and other basics of mechanical engineering how will they be able to design the refrigerator?

4) Interdisciplinary ability: A good design engineer is the one who has the ability to solve the problems not only those related to his/her specialty, but also have the ability to competently and confidently deal the basic problems or ideas from other disciplines which are in some or the other manner linked to the machine they are designing.

5) Mathematical skills: All types of designs involve lots of mathematical calculations and iterations. A good designer should have the knowledge of all the basics and advanced mathematical concepts so that they can be applied fruitfully and effectively wherever required.

6) Decision making: During designing many times a number of uncertain situations arrive, in such cases the designer should be able to take the decision with balanced mind considering all the relevant factors involved. If the person doesn’t maintain the balance of mind and doesn’t consider all the relevant factors there are greater chances of taking the wrong decision.

7) Manufacturing processes: The design engineer should have the knowledge of the manufacturing process like cutting, drilling, milling etc and the knowledge of all the machines. They should also the knowledge of potential and limitations of all the machines and manufacturing processes which may be old or new.

8) Communication skills: Communication skill is the ability of the design engineer to express oneself clearly and persuasively orally, graphically as well as in writing.

These are the important skills that the machine design engineer or rather any designer should posses. Apart from this there are many other skills desired from a good designers, these are: skill in design, good judgment, simulation skill, measurement skill, thought skill, work in team, ability to make conclusion etc.


Book: Machine Design by Dr. P. C. Sharma and D. K. Aggarwal

Machine Design or Mechanical Design

This is the series of articles on Machine Design or Mechanical Design. Machine design and drawing are very important subjects of mechanical engineering. No produce can be manufactured without designing it. Here some basic concepts of machine design or mechanical design have been covered


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