In today’s modern world machine design is challenging day by day because of lots of options available in the market. So, there is challenging for a designer to design a machine with all these criteria as per below mention in this article. What is machine design, types of machine design, general considerations, and general procedure for machine design?
Definition of Machine design
Machine design is to build new and better machines and improve existing ones. A new or improved machine is one that is more economical in the overall cost of production and operation. The design process is a long and a time consuming one. From the study of existing ideas, a new idea has to be imagined. The idea is then studied keeping in mind its commercial success and the shape and form given to the picture.
In the preparation of these drawings, the availability of resources in money, in men, and in real thought must take into account the materials necessary for the successful completion of the new idea. In designing machine components, it is necessary to have a good knowledge of many subjects such as mathematics, engineering mechanics, material strength, a theory of machine, workshop procedures, and engineering drawings, etc.
Types of Machine Design
Machine design can be classified as follows:
Adaptive Design: In most cases, the designer’s work is concerned with the adaptation of existing designs. This type of design does not require any special knowledge or skills and can be attempted by designers of general technical training. The designer makes only minor reversion or modification to the existing designs of the product.
Development Design: This type of design requires considerable scientific training and design in order to transform existing designs into new ideas by adopting new materials or different methods of manufacture. In this case, although the designer starts with the existing design. The end product can be quite different from the original product.
New Design: This type of design requires a lot of research, technical ability, and creative thinking. Only designers who have sufficiently high order personal qualities can work a new design.
Designs based on the methods used can be classified as follows:
- Rational Design: This type of design depends on mathematical formulas of the principle of mechanics.
- Empirical Design: This type of design depends on empirical formulas based on practice and past experience.
- Industrial Design: This type of design depends on the product features for manufacturing any machine component in the industry.
- Optimal design: It is the best design for a given objective function under specified constraints. This can be achieved by reducing undesirable effects.
- System Design: It is the design of any complicated mechanical system like a motor car.
- Element Design: It is the design of any part of a mechanical system such as a crankshaft, piston, connecting rod, etc.
- Computer-Aided Design: This type of design relies on the use of computer systems to aid in the construction, modification, analysis, and optimization of a design.
What are the General Considerations in Machine Design?
The following are general considerations in designing machine components:
Type of load and stress due to load
The load on a machine component can act in many ways due to which internal stresses establish.
The motion of machine parts or kinematics
The successful operation of any machine depends largely on the simplest arrangement of the parts that will provide the required speed. The speed of the parts can be:
- Rectilinear motion including unidirectional and recrossing motion.
- curvilinear motion consisting of rotary, oscillation, and simple harmonic.
- Steady speed.
- Constant or variable acceleration.
Selection of materials
It is essential that a designer should have an in-depth knowledge of the properties of materials and their behavior in working conditions. Some important features of the materials are strength, durability, flexibility, weight, resistance to heat and corrosion, moldability, welded or hardened, machinability, electrical conductivity, etc.
Size and shape of parts
Form and shape are based on decisions. The smallest practical cross-section can use. But it can test that the stresses induced in the designed cross-section are more secure. To design the part of any machine for form and shape. It is necessary to know the forces that the part must maintain. It is also important to estimate any sudden applied or impact loads that may cause failure.
Abrasion resistance and lubrication
There is always a loss of power due to abrasion resistance and it should be noted that the starting friction is greater than the running friction. Therefore, it is necessary that careful attention should be paid to the case of lubrication of all surfaces, which run in contact with others, whether they are in rotating, sliding, or rolling bearings.
Convenient and economical features
In designing, the operating characteristics of the machine must be carefully studied. Starting, controlling, and stopping the lever must be located on the basis of convenient handling. Wear adjustments must provide to employ various take-up devices and to organize them so that the alignment of the parts preserved. If parts replaced for different products or replaced due to wear or breakage, easy access should provide, and if possible, the need to remove other parts to accomplish this should avoid.
The economical operation of a machine, which is to use for production, or for the processing of materials, must be studied to find out whether it has the maximum capacity to correspond to the production of good work.
Use of standard parts
The use of standard parts is closely related to cost, as the cost of standard or stock parts is only one part of the cost of similar parts made to order.
Standard or stock parts should use whenever possible; Parts for which patterns already exist such as gears, pulleys, and bearings. And parts that can select from regular shop stock such as screws, nuts, and pins. Bolts and studs should be as short as possible to avoid delays in changing drills, reamers, and taps. As well as reducing the number of wrenches required.
Safety of operation
Some machines are dangerous to operate, especially those that are fast to insure production at the maximum rate. Therefore, any moving part of a machine, which is within a worker’s zone, is considered a risk of accident and may cause injury. Therefore, it is necessary that a designer should always provide safety equipment to protect the operator. Safety devices should not interfere with the operation of the machine in any way.
A design engineer should be familiar with the limitations of his employer’s workshop. So, as to avoid the need to work in some other workshop. Sometimes it is necessary to plan and supervise the operation of the workshop and to draft methods for casting, handling, and machining special parts.
The number of machines to be manufactured
The number of articles or machines manufactured affects design in many ways. Engineering and shop costs called fixed charges or overhead expenses are distributed over the number of articles to manufactured. If only a few articles are to make, the additional expense is not reasonable unless the machine is large or of some special design. An order calling for a small number of products will not allow for any undue expense in the workshop processes so that designers can limit their specification to standard parts.
Cost of manufacture
The cost of building an article the most important consideration involved in the design. In some cases, it is very possible that the high cost of an article may immediately prevent it from further consideration. If an article has been invented and tests of handmade samples have shown that it has commercial value. It is possible to justify the expense of a considerable amount of money in the design and development of automated machines for the production of the article. Especially if it is Can be sold in large numbers. The objective of the design engineer, under all conditions, should be to minimize manufacturing costs.
Each machine or structure must assemble as a unit before functioning. Larger units must often assemble in the shop, tested, and then transported to their place of service. The final location of any machine is important and the design engineer must estimate the exact location and local facilities for manufacture.
What is the General Procedure in Machine Design?
In designing machine components, there is no hard and fast rule. The problem can try in many ways. However, the general procedure for resolving a design problem is as follows:
- Recognition of Necessity: First, make a complete statement of the problem, indicating which purpose or purpose the machine is to be designed for.
- Synthesis (a mechanism): Select the possible mechanism or group of mechanisms that will give the desired speed.
- Analysis of forces: Find the forces acting on the energy transmitted by each member of the machine and each member.
- Material Selection: Select the most appropriate material for each member of the machine.
- Design of Elements: Find the size of each member of the machine by considering the force and permissible stress on the member for the material used. It should be kept in mind that each member should not deflect or deform beyond the permissible limit.
- Modification: Modify the size of the member to agree with previous experience and decision to facilitate construction. Modification may also be necessary by considering manufacturing to reduce overall costs.
- Detailed drawing: Draw a complete drawing of the assembly of each component and machine with the entire specification for suggested manufacturing processes.
- Production: The component is manufactured in the workshop according to the drawing.