CAD : What A Wonderful Field It Is

Engineers, design professionals, and manufacturers have learned the value of using and developing technologies based on CAD, or Computer Aided Drafting. This ever expanding field utilizes CAD for conceptual design and layout of virtual products, effectively eliminating the high cost of manufacturing a test product; creating architectural, construction, and building plans for contractors; planning mechanical, electrical, and plumbing layouts for builders and manufacturers; and all in a fraction of the time of what was once possible using 2 dimensional drafting practices.
So why seek a career in CAD drafting? The median salary for an entry-level CAD is approximately $40,000 per year, and it provides employment opportunities in almost every field. CAD is used in the medical and forensic science fields; for manufacture of aviation, automotive, and ship building; and 2D & 3D modeling of tools and machinery. CAD drafting has had an enormous impact on almost every field imaginable, and without it modern advancements would still be decades away.
The future of CAD is already moving forward, and students of CAD and Auto-CAD will be poised on the cutting edge of technology as 3D and Spatial 3-D holographic imaging replace 2D as the standard. In order to take full advantage of this, finding the right CAD drafting school is important, and one city stands out: Kansas City, Missouri is in the right location and has the right schools to help students learn the skills they'll need.

Disadvantages of Mechanical Engineering

Disadvantages of Mechanical Engineering
The workload is usually high and the atmosphere is competitive. Even Working environment is not so best. You find much Air conditioners like Software jobs. Also, despite recent increases in enrollment of women across all science and engineering disciplines, mechanical engineering still contains the lowest percentage of women. Since, it involves bit hard work.

Advantages are more than Disadvantages. so, dont afraid of Mechanical engineering.

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Mechanical Core Jobs

Mechanical Core Jobs

As a Mechanical Engineer we all like to join in a Mechanical Core Job. Mechanical engineering is finding more and more applications these days in other areas of engineering also.

Now we are having great opportunities in CAD/CAM industry. It is the future of Mechanical engineering.

Simplex and Duplex Pump

Simplex and Duplex Pump

A simplex pump, sometimes referred to as a single pump, is a pump having a single liquid (pump) cylinder. A duplex pump is the equivalent of two simplex pumps placed side by side on the same foundation.The driving of the pistons of a duplex pump is arranged in such a manner that when one piston is on its upstroke the other piston is on its downstroke, and vice versa. This arrangement doubles the capacity of the duplex pump compared to a simplex pump of comparable design.

Direct-Acting and Indirect-Acting Pumps

Direct-Acting and Indirect-Acting Pumps

Some reciprocating pumps are powered by prime movers that also have reciprocatingmotion, such as a reciprocating pump powered by a reciprocating steam piston. The piston rod of the steam piston may be directly connected to the liquid piston of the pump or it may be indirectly connected with a beam or linkage. Direct-acting pumps have a plunger on the liquid (pump) end that is directly driven by the pump rod (also the piston rod or extension thereof) and carries the piston of the power end. Indirect-acting pumps are driven by means of a beam or linkage connected to and actuated by the power piston rod of a separate reciprocating engine.

Reciprocating Pumps types

Reciprocating positive displacement pumps are generally categorized in four ways:
Direct-acting or indirect-acting
Simplex or duple
Single-acting or double-acting
Power pump

Principle of Operation of Positive Displacement Pump

This is the operation of simple Positive Displacement Pump is given below.

Principle of Operation of Positive Displacement Pump

All positive displacement pumps operate on the same basic principle. This principle can be most easily demonstrated by considering a reciprocating positive displacement pump consisting of a single reciprocating piston in a cylinder with a single suction port and a single discharge port as shown in Figure. Check valves in the suction and discharge ports allow flow in only one direction.
During the suction stroke, the piston moves to the left, causing the check valve in the suction line between the reservoir and the pump cylinder to open and admit water from the reservoir.During the discharge stroke, the piston moves to the right, seating the check valve in the suction line and opening the check valve in the discharge line. The volume of liquid moved by the pump in one cycle (one suction stroke and one discharge stroke) is equal to the change in the liquid volume of the cylinder as the piston moves from its farthest left position to its farthest right position.

Definition of Positive displacement pump

Pumps are the basic requirement in our day to day life. These are having so much of importance. Pumps field is so good. for every mechanical engineer should have a good idea in Pumps. All the fundamentals of pumps are given below.........

Introduction
A positive displacement pump is one in which a definite volume of liquid is delivered for each cycle of pump operation. This volume is constant regardless of the resistance to flow offered by the system the pump is in, provided the capacity of the power unit driving the pump or pump component strength limits are not exceeded. The positive displacement pump delivers liquid in separate volumes with no delivery in between, although a pump having several chambers may have an overlapping delivery among individual chambers, which minimizes this effect. The positive displacement pump differs from centrifugal pumps, which deliver a continuous flow for any given pump speed and discharge resistance.
Positive displacement pumps can be grouped into three basic categories based on their design and operation.
The three groups are
1. Reciprocating pumps
2. Rotary pumps
3. Diaphragm pumps

Rotary Liquid Seal ring type Air compressor

Rotary Liquid Seal ring type Air compressor has forward inclined, open impeller, in an oblong cavity filled with liquid. As the impellerrotates, the centrifugal force causes the seal liquid to collect at the outer edge ofthe oblong cavity. Due to the oblong configuration of the compressor case, large longitudinal cells are created and reduced to smaller ones. The suction port is positioned where the longitudinal cells are the largest, and for the discharge port, where they are smallest, thus causing the vapor within the cell to compress as the rotor rotates. The rotary liquid seal compressor is frequently used in specialized applications for the compression of extremely corrosive and exothermic gasses and is commonly used in commercial nuclear plants as a means of establishing initial condenser vacuum.

Rotary Lobe type Air Compressor

Rotary Lobe type Air Compressor has two mating lobe-type rotors mounted in a case. The lobes are gear driven at close clearance, but without metal-to-metal contact. The suction to the unit is located where the cavity made by the lobes is largest. As the lobes rotate, the cavity size is reduced, causingcompression of the vapor within. The compression continues until the discharge port is reached, at which point the vapor exits the compressor at a higher pressure.

Rotary slide vane type Air Compressor

Rotary slide vane type Air Compressor has longitudinal vanes, sliding radially in a slotted rotor mounted eccentrically in a cylinder. The centrifugal force carries the sliding vanes against the cylindrical case with the vanes forming a number of individual longitudinal cells in the eccentric annulus between the case and rotor. The suction port is located where the longitudinal cells are largest. The size of each cell is reduced by the eccentricity of the rotor as the vanes approach the discharge port, thus compressing the air.

Types Rotary Compressors

Rotary Compressors
The rotary compressor is adaptable to direct drive by induction motors or multicylinder gasoline or diesel engines. The units are compact, relatively inexpensive, and require a minimum of operating attention and maintenance. They occupy a fraction of the space and weight of a reciprocating machine of equivalent capacity.
Rotary compressor units are classified into three general groups
Slide vane-type
Lobe-type
Liquid seal ring-type.

Types of Air Compressor

Air compressors of various designs are used widely throughout DOE facilities in numerous applications. Compressed air has numerous uses throughout a facility including the operation of equipment and portable tools.
Three types of designs
1. reciprocating
2. rotary
3. centrifugal air compressors.

Working of Centrifugal Compressor

Introduction

Air compressors of various designs are used widely throughout DOE facilities in numerous applications. Compressed air has numerous uses throughout a facility including the operation of equipment and portable tools. Three types of designs include reciprocating, rotary, and centrifugal air compressors.

Centrifugal Compressors

The centrifugal compressor, originallybuilt to handle only large volumes of lowpressure gas and air (maximum of 40psig), has been developed to enable it tomove large volumes of gas with dischargepressures up to 3,500 psig. However,centrifugal compressors are now mostfrequently used for medium volume andmedium pressure air delivery. Oneadvantage of a centrifugal pump is thesmooth discharge of the compressed air.The centrifugal force utilized by thecentrifugal compressor is the same forceutilized by the centrifugal pump. The airparticles enter the eye of the impeller,designated D in Figure 6. As the impeller rotates, air is thrown against the casing of the compressor. The airbecomes compressed as more and more air is thrown out to the casing by the impeller blades.The air is pushed along the path designated A, B, and C in Figure 6. The pressure of the air is increased as it is pushed along this path. Note in Figure 6 that the impeller blades curve forward, which is opposite to the backward curve used in typical centrifugal liquid pumps.Centrifugal compressors can use a variety of blade orientation including both forward and backward curves as well as other designs.There may be several stages to a centrifugal air compressor, as in the centrifugal pump, and the result would be the same; a higher pressure would be produced. The air compressor is used to create compressed or high pressure air for a variety of uses.Some of its uses are pneumatic control devices, pneumatic sensors, pneumatic valve operators, pneumatic motors, and starting air for diesel engines.

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Grain Boundary Strengthening

Grain Boundary Strengthening in Strenghtening Process
Decreasing/Finer grain size will increase the yield stress.

The grain size indicates two conditions: The distance for the dislocations have to move to form grain boundary pile-ups and the number of dislocations involved. Having finer grain size, the mobility of the dislocations is harder to move from one grain to another for plastic deformation. In other words, finer grain will impede the dislocations. This will give rise to the strength of the material. However, the grain size cannot be too small (around below 10 nm). This will lead to grain-boundary sliding. The grain boundaries tend to slide and difficult to fit the dislocations in the grain. Thus, less stress required to move them. The equation to this mechanism is The Hall-Petch Equation which states an increase in yield stress is related to a decrease in diameter of the average grain.


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