What does HVAC stand for

Full form of HVAC is Heating Ventilation and Air Conditioning.

HVAC can stand for a climate-control mechanism for providing thermal comfort and acceptable indoor air quality and regulate the humidity and temperature in a living environment.

It is a sub-discipline of mechanical engineering, based on the principles of thermodynamics, fluid mechanics, heat transfer and sometimes refrigeration and air conditioning. 

This technology is used for indoor and vehicular environmental comfort. Its goal is to provide thermal comfort and acceptable indoor air quality.

There are three types of setting done in HVAC :

Full Heat Setting :

Maximum airflow is directed through the heater core by the blend door to deliver the most heat possible to the main upper vents. 

So in this setting operator has demanded full heat.

Economy Mode Setting :

Maximum airflow is directed around the heater core to allow filtered air at ambient temperature to enter the cabin through the main upper vents. 

Max A/C Setting :

In this setting, the HVAC system takes air from the cabin that has already been cooled once and cools it again instead of trying to cool hot ambient air.

To get the most cooling power in this setting the operator has selected max A/C.

What is slotting machine

The slotting machine was developed by Brunel in the year 1800 much earlier than a shaper was invented. It falls under the category of the reciprocating type of machine tool similar to a shaper or a planer. Both are operated almost on the same principle but the major difference between them is in a slotter the ram holding the tool reciprocates in a vertical axis, whereas in a shaper the ram holding the tool reciprocates in horizontal axes. 

What is slotting machine?

Slotting machine is vertically reciprocating machine tool used for making a mortise or shaping the sides of an aperture, in which ram holding the tool reciprocates in a vertical axis and the cutting action of the tool is only during the return downward stoke.

The slotting machine is used for cutting grooves, keyways and slots of :

• Various shapes
• For making regular and irregular surfaces both internal and external. 

It is also used for handling large and awkward workpieces, for cutting internal and external gears and many other operations which can't be conventionally machined in any other machine tools.

Types of slotter machine :

There are mainly two types of slotter machine :

• Puncher slotter
• Precision slotter 

Puncher slotter :

It is heavy, a rigid machine designed for removal of a large amount of metal from large forging or casting. 

The length of puncher slotter is large it may be as long as 1800 to 2000 mm. 

In this machine puncher slotter, ram is usually driven by a spiral pinion meshing with the rack teeth cut on the underside of ram. The pinion is driven by a variable speed reversible electric motor similar to that of a planer. 

In this machine, feed is also controlled by electrical gear. 

Precision slotter :

It is a lighter machine and is operated at high speeds.

This machine is designed to take light cuts giving an accurate finish. 

By using special jigs, the machine can handle a number of identical works on a production basis. 

This machine is also used for general-purpose work and is usually fitted with a whitworth quick return mechanism. 

Parts of slotter machine :

• Base 
• Column 
• Saddle 
• Cross-slide 
• Rotating table 
• Ram and tool head assembly 
• Ram drive mechanism 
• Feed mechanism 

Now we can see parts in details :

Base or bed :

The base is rigidly and it takes up all the cutting forces and entire load of the machine. 

It is the key parts of the machine that made from cast iron. 

The top of the bed is accurately finished to provide guideways on which the saddle is mounted. The guideways are perpendicular to the column face. 

Column : 

The column is the vertical member which is made up of cast iron. 

The column is assembled with the base and houses driving mechanism of the ram and feeding mechanism. 

The vertical front face of the column is accurately finished for providing ways in which the ram reciprocates up and down. 

Saddle :

The saddle is mounted upon the guideways and may be moved towards or away from the column either by power or manual control to supply longitudinal feed to the work. 

The top face of the saddle is accurately finished to provide guidance for the cross-slide. These guideways are perpendicular to the guideways on the base. 

Cross-slide : 

The cross slide is mounted upon the guideways of the saddle and may be moved parallel to the base of the column.

The movement of the slide may be controlled either by hand or power to supply crossfeed. 

The circular worktable is mounted on the top of the cross-slide.  

Handwheels :

It is provided for rotating the table for the longitudinal and cross traverse.

Rotary table : 

The rotary table is a circular table which is mounted on the top of the cross slide. 

The table may be rotated by rotating a worm which meshes with a worm gear connected to the underside of the table. 

The rotation of the table may be affected either by hand or power. 

The rotary table enables a circular or contoured surface to be generated on the work piece. 

Ram and tool head assembly : 

The run is reciprocating member of the machine mounted on the guideways of the column. 

It supports the tools at its bottom end on a tool head. 

A Slot is cut on the body of the ram for changing the position of the stock. 

In some mechanism, a special type of tool holders is provided to relieve the tool during the return stroke. 

Ram drive mechanism : 

A slotter removes metal during the downward cutting stroke. No metal removed during the upward return stroke.

The usual types of ram drive mechanisms are :

• Whitworth quick return mechanism
• Variable speed reversible motor drive mechanism
• Hydraulic drive mechanism 

The operation performed on slotter machine :

• Machining internal and external flat surfaces.
• Internal recess of circular, semi-circular, concave and convex surfaces.
• Machining internal and external circular surfaces.
• Internal machining of blind holes.
• For shaping internal and external forms or profiles.
• Machining vertical, angular or inclined surfaces.
• Machining irregular surface which is difficult to produce.
• For machining dies and punches.
• To cut slots, grooves, splines and keyways for both internal and external surfaces.
• Machining internal and external gear teeth. 

Cutting speed :

The rate at which the metal is removed during downward cutting stroke is called cutting speed.

It is expressed in meters / minute. 

Depth of cut :

The perpendicular distance measured between the machined surface and the un-machined surface called the depth of cut.

It is expressed in mm. 

Feed :

The movement of the work per double stroke is called feed.

It is expressed in mm.

Cutting speed feed and depth of cut of slotter machine

Cutting speed :

The rate at which the metal is removed during downward cutting stroke is called cutting speed.
It is expressed in meters/minute. 

Feed :

A feed is the movement of the work per double stroke. 
It is expressed in mm.

Depth of cut :

Depth of cut is a perpendicular distance measured between the machined surface and un-machined surface also.
It is expressed in mm. 

Slotting machine operation

There is a different operation performed on the slotting machine because this operation is more economical for certain types of work. 

Let us see the different operation performed on the slotter machine :

• Machining internal and external flat surfaces.
• Internal recess of circular, semi-circular, concave and convex surfaces.
• Machining internal and external circular surfaces.
• Internal machining of blind holes.
• For shaping internal and external forms or profiles.
• Machining vertical, angular or inclined surfaces.
• Machining irregular surface which is difficult to produce.
• For machining dies and punches.
• To cut slots, grooves, splines and keyways for both internal and external surfaces.
• Machining internal and external gear teeth. 

Slotting machine parts

In this article you can see some different parts of a slotting machine which are following below :

• Base 
• Column 
• Saddle 
• Cross-slide 
• Rotating table 
• Ram and tool head assembly 
• Ram drive mechanism 
• Feed mechanism 

Now we can see parts in details :

Base or bed :

The base is rigidly built to take up all the cutting forces and the entire load of the machine. 

It is the key parts of the machine that made from cast iron. 

The top of the bed is accurately finished to provide guideways on which the saddle is mounted. The guideways are perpendicular to the column face. 

Column : 

The column is the vertical member which is made up of cast iron. 

The column is assembled with the base and houses driving mechanism of the ram and feeding mechanism. 

The vertical front face of the column is accurately finished for providing ways in which the ram reciprocates up and down. 

Saddle :

The saddle is mounted upon the guideways and may be moved towards or away from the column either by power or manual control to supply longitudinal feed to the work. 

The top face of the saddle is accurately finished to provide guidance for the cross-slide. These guideways are perpendicular to the guideways on the base. 

Cross-slide : 

The cross slide is mounted upon the guideways of the saddle and maybe moved parallel to the base of the column.

The movement of the slide may be controlled either by hand or power to supply crossfeed. 

The circular worktable is mounted on the top of the cross-slide.  

Handwheels :

It is provided for rotating the table for the longitudinal and cross traverse.

Rotary table : 

The rotary table is a circular table which is mounted on the top of the cross slide. 

The table may be rotated by rotating a worm which meshes with a worm gear connected to the underside of the table. 

The rotation of the table may be affected either by hand or power. 

The rotary table enables a circular or contoured surface to be generated on the work piece. 

Ram and tool head assembly : 

The run is a reciprocating member of the machine mounted on the guideways of the column. 

It supports the tools at its bottom end on a tool head. 

A Slot is cut on the body of the ram for changing the position of the stock. 

In some mechanism, a special type of tool holders is provided to relieve the tool during the return stroke. 

Ram drive mechanism : 

A slotter removes metal during downward cutting stroke only whereas during upward return stroke no metal is removed. 

The usual types of ram drive mechanisms are :

• Whitworth quick return mechanism
• Variable speed reversible motor drive mechanism
• Hydraulic drive mechanism 

Types of slotting machine

There are mainly two types of slotting machine :

• Puncher slotter
• Precision slotter 

Puncher slotter :

It is a heavy, rigid machine designed for removal of a large amount of metal from large forging or casting. 

The length of puncher slotter is large it may be as long as 1800 to 2000 mm. 

In this machine puncher slotter, ram is usually driven by a spiral pinion meshing with the rack teeth cut on the underside of ram. The pinion is driven by a variable speed reversible electric motor similar to that of a planer. 

In this machine, feed is also controlled by electrical gear. 

Precision slotter :

It is a lighter machine and is operated at high speeds.

This machine is designed to take light cuts giving an accurate finish. 

By using special jigs, the machine can handle a number of identical works on a production basis. 

This machine is also used for general-purpose work and is usually fitted with a whitworth quick return mechanism. 

Advantages and disadvantages of friction welding

Friction welding works on the basic principle of friction is used to generate heat at the interference surface this heat is used to join two workpieces by applying external pressure at the surface of the workpiece. The joint is created in this welding is due to thermomechanical treatment. The main advantage of friction welding is the ease with which the joining can take place. Now, let us have a deep insight into the pros and cons of friction welding. 

Advantages of friction welding :

• Oxides and contaminants present would easily be removed during the initial rubbing so that edge cleaning is not a problem.
• Since the joining takes place by diffusion rather than by actual melting, even dissimilar metals can be joined. 
• The heat generated is small and below the melting temperature, there will be no distortion and warping.
• The quality of weld achieved is very high.
• High welding speed.
• Economical in other welding operation.
• No skilled operator is required to work on the friction welding machine since it is completely automatic in operation.
• No possibility of porosity and slag inclusion.
• It is an environmentally friendly process since there is no fumes, gases or smoke is generated.
• No flux, filler metal or gas is required to perform this process.
• No special power supply is required.
• Wide variety of metal can be weld by this process.

Disadvantages of friction welding : 

• This process used for only round bars of the same cross-section. 
• Limited to angular and flat butt joints. 
• Set-up cost is very high. 
• Preparation of workpiece is difficult. 
• Non-forgeable materiel can not be weld.
• It can only be used for smaller parts of machines, big parts are not compatible with it. 

Advantages and disadvantages of projection welding

Projection welding is also called as resistance welding produces coalescence of welding material, the heat generated from electric resistance to current through the workpiece hold together with pressure applied to electrodes. Let us have a deep insight into the pros and cons of projection welding in this article. 

Advantages of projection welding :

• It is possible to weld more than one spot at a given time. The number of welds depends on the number of projections that can come under the tip of the electrode. Up to about 6 welds per cycle can be made which substantially reduces the cost of manufacture.
• The welds may be placed closer than possible in spot welding.
• Because of the large-sized electrodes used, their life is much longer than that of the spot welding electrode. The larger contact area makes for very limited deformation of the welding tip.
• They can help in holding the workpieces together in proper alignment during the welding process.
• Proper heat balance can be easily obtained in projection welding by making the projections in thicker plates while welding sheets of different thickness. 
• For welding dissimilar metals, the projections are to be made on the material having higher electrical conductivity to provide proper heat balance.
• The uniformity and appearance of the weld are much better compared to spot welding.

Disadvantages of projection welding :

• Prior operation of embossing is required before welding.
• Electrodes are often to be specially made for a particular operation. This can only be justified when production rates and volumes are large. 

Atomic hydrogen welding

Introduction :

Atomic hydrogen welding is an arc welding process. In this process the arc used in between two tungsten electrodes in a shielding atmosphere of hydrogen. This process was invented by Irving Langmuir in the course of his studies of atomic hydrogen. When Hydrogen is in its atomic state, is a strong reducing gas which prevents oxidation of weld metal and rapid burning of electrodes. Any oxygen present in the surrounding combines with hydrogen forming water which is converted into steam.

Equipment set up :

Set up of this operation consist of hydrogen cylinder, an AC welding machine and the welding torch to accommodate to tungsten electrons, with provision for changing the distance between them. The normal voltage range of the power supply is between 50 to 75 volt with the current varying from 15 to 150 A. This measure is good enough for an electrode size of 1 to 5 mm.

The path of electron travel between the two electrodes is not a straight path as in other arc welding process. Instead, they travel in the form of a fan. This is because the hydrogen atoms formed by the arc causes a downward force because of with electron flow slightly deviates. This fan shape can be changed by altering the distance between the electrodes and the current level. The DC machines could also be used in atomic hydrogen welding, but because of the electron flow is only in one direction, the wear of electron is particularly high and as a result, only AC power supply is used.

When hydrogen atoms recombine near the workpiece surface, they generate a temperature of the order of the 300 0C. Because of this heat, the molten metal becomes highly fluid and therefore, atomic hydrogen welding is used for the flat position only. Filler metal when needed is melted intermittently in the arc fan for fusing with the base metal.

Working principle :

Atomic hydrogen welding the atomic hydrogen welding is an inert gas welding arc welding process done with non-consumable electrodes. The main difference between tungsten inert gas welding and this process is that in atomic hydrogen welding, the arc is obtained between the two tungsten electrodes rather than between the tungsten electrode and the workpiece. This shielding gas used here is hydrogen, which is reactive in nature compared to argon. The hydrogen molecule (H₂), when passing through the electric arc, get this dissociated into two hydrogen atoms (H+). The hydrogen atoms are highly reactive. They form hydrogen molecule and combine with oxygen if present to form water vapour enters release intense heat for the necessary melting of the joint. Because of its type reactivity, the atomic hydrogen is able to break the oxide on the base metal and thus allow the formation of a clean weld. 

Application :

When properly performed, atomic hydrogen welding gives an extremely clean weld with excellent quality. It is generally used for welding of tool Steels containing tungsten, Nickel and Molybdenum as also for hard surfacing and repairing of moulds, dies and tools. Though it can be used for any job, its high cost prohibits its general usage.

Oxy hydrogen welding

Working principle :

In oxy-hydrogen welding, hydrogen combines with oxygen to generate steam and attains a flame temperature of around 2800⁰C. But the weld pool is not protected from the atmosphere when the oxygen for combustion is completely provided by the torch itself. So, Oxygen is an amount slightly less than that required for complete combustion is provided by the torch, whereas atmospheric oxygen accounts for the burning of the remaining hydrogen. This gives rise to a protective preheating flame that surrounds the main flame. But this reduces the flame temperature to some extent. Because of the lower flame temperature, oxy-hydrogen welding is a generally slow process. It is normally used to weld thin sheets of steels and alloys with low melting temperatures.

Key features :

• Operation is convenient & safe

Oxy hydrogen generator produces oxygen and hydrogen gas that you required and also no gas cylinder is required. There is no risk of explosion.

• Environmental friendly 

In this process, fuel comes from water and there is water vapour after finishing this process so this process is environmentally friendly.

• Welding features 

Welding work is fast, precision, smooth and beautiful welding spot. The oxyhydrogen flame is concentrated up to 2800 ⁰C so it can heat the welding spot to melting point very quickly.

• Energy-saving and low cost 

This process is done with very low electricity and pure water. The cost of electricity and water is reduced by more than 40% compared with LPG and other welding processes.

Tungsten inert gas welding

Tungsten inert gas welding is also known as gas tungsten arc welding.

In this process, an inert gas shielded arc welding process using a non-consumable electrode. The electrode may also contain 1 to 2% thoria mix along with the core tungsten or tungsten with 0.15 to 0.40% zirconia. The pure tungsten electrodes are less expensive but also it will carry less current. The thoriated tungsten electrodes carry high current and more desirable because they can strike and maintain a stable at with relative ease. The zirconia added tungsten electrode better than pure tungsten but inferior to thoriated tungsten electrodes.

The process set up :

Tungsten inert gas welding setup is shown in figure it consists of a welding torch at centre electronic inert gas is supplied to the welding zone through the Anil apart surrounding the tungsten electrode to effectively displays the atmosphere Around The World Patel the smaller world tours may not be provided with Anni cooling device for the electrodes but larger ones are provided with circulating cooling water 30 welding process can be used for joining a number of materials through the more aluminium magnesium and stainless steel.

Components used :

• Power Supply (A.C or D.C)
• Filler Rod
• Non-consumable Tungsten electrode
• Welding Head
• Inert Gas Supply

Working principle :

TIG welding process is relatively difficult to perform out of another welding process because it normally requires two hands for the process to be performed while other processes require that the welder manually feed a filler metal into the weld area with one hand.

In this process, first of all, strike the welding arc that can be produced by torch. A high-frequency generator provides an electric spark. This spark is a conductive path for the welding current through the shielding gas and it allows the arc to be initiated while the electrode and the workpiece are separated. The inert gas forms a gas shielding around the weld. It protects the weld from the external atmosphere. 

Once the arc is struck, the welder moves the torch in a small circle to create a welding pool, the size of that depends on the size of the electrode and the amount of current then torch moves back and filler metal is added manually to the front end of the weld pool as it needed.
The arc current is often gradually reduced to allow the weld crater to solidify and prevent the formation of cracks at the end of the weld. Thus, this process can be done.

Advantages of TIG welding :

• It produces high quality and clean welds.
• No slag is produced so welds are not weakened.
• The weld is automatically protected by the inert gas during the welding process so welds are corrosion resistance, more ductile, and stronger.
• This process can apply for any position of welding like wise horizontal, vertical or flat.
• It can be performed by both automatic and manual technique.
• It easily applied to thin material and used for a wide range of metal thickness.
• There is less distortion of work piece because the small heat affected zone.
• Only the necessary amount of filler metal is added to the welding puddle so there is no spatter or sparks are produced.
• Use one shielding gas mainly Argon for all applications.
• In this process finishing process required little or less. Sometimes grinding or preparation before it can be painted.
• It is the preferred choice in most of the intricate works, where shape of each and every weld joint counts.

Main most common limitations of TIG welding is low deposition rate of the filler and metal per pass so that time increased to completed the welds that's why it is mostly used for thinner metal. More than that it has certain disadvantages we can check it below :

Disadvantages of TIG welding :

• As we seen it is slow process.
• More complicated process so that highly skilled labour is required.
• Less economical than consumable electrode for sections thicker than 3/8 inch.
• Tungsten inclusion.
• Welder is exposed to the huge intensities of light.
• This process is also more expensive.
• Sensitive to drafts.

Tungsten Inert Gas Welding offers several advantages that account for its popularity and its use in agriculture and many other industries. 

Applications of Tungsten Inert Gas Welding :

• Stainless steel
• Alloy steel
• Aluminium
• Titanium
• Copper
• Magnesium
• Nickel alloys

Broaching machine

Broaching process is the simplest of all machine tools that can be performed on a broaching machine. It can be consist of a work welding fixture, broaching tools, a drive mechanism and suitable supporting frame. Although the component parts are few, several variations are possible. 

There are two principal types of machine :

• Horizontal 
• Vertical 

In addition to these standard types, there are special and continuously operating machines. Both horizontal and vertical types have one or more rams depending on production recruitment. Dual ram models are arranged so that when one ram is on the cutting stroke the other is on the return stroke and the return stroke is performed quickly to gain time, which is used to and load the machine. 

Broaching machines usually pull or push the approach through, or past a work piece that is held in a fixture. On some machines, however, the work piece is moved past that is fixed position. Most broaching machines operated to secure a smooth, uniform cutting action.


Horizontal broaching machine :

Most of all broaching machines at the pull type. They may be used for either internal or external broaching. The horizontal broaching machine consists of a bed or a little more than twice the length of broaching stroke, a broach pilot and the drive mechanism of pulling the brooch. 
It is used in many application especially for broaching keyways, splines, slots, round holes and other internal shapes or contours. They have the disadvantages of taking more floor space than vertical machines. 

Vertical broaching machine :

The vertical type may be obtained in either push or pull type. The push-type is more popular. It can be employed in multiple operations, since they are convenient to pass work from one machine to another, and they are more likely to be found doing surface operations. Of the three models available pull-up, pull-down and push down, the pull-up type is most popular. 

Vertical machines require an operator platform or a pit and are economical of floor space than the horizontal type.


Surface broaching machine :

Surface broaching machines have their broaching tools attached to the ram or ram forced in a straight path along with guide ways past the work piece. On some machines, the ram moves horizontally on other vertically. When two rams are used, the machine is called duplex broach. 


Continuous broaching machines : 

For mass production of smart small parts, the highly productive continuous broaching method is used on rotary or horizontal continuous-broaching machines. 

In this machine the work piece is loaded on the table which rotate continuously. During the operation the broach is stationary. 

In the horizontal continuous broaching machine the work piece travel as they are carried by an endless chain. The work piece are loaded into work holding fixture that is mounted on the continuous moving chain. During the operation the broach is stationery as before. Such machines are used for broaching small parts.

Types of belt drive

A belt drive is one of the most common and effective means of transmission of motion from one shaft to another shaft. There are different belt drive used for different applications. Now we can see the different types of belt drive :

Types of belt drive :

According to the power transmitted :

1. Light belt drive 
2. Medium belt drive 
3. Large belt drive 

According to the arrangement of the belt :

1. Open belt drive
2. Crossbelt drive
3. Quarter twist drive
4. Right angle drive
5. Stepped pulley drive
6. Fast and loose pulley drive 
7. Compound drive 

VTVT vs CRDI

VTVT and CRDI are the fancy names given to engines from different manufacturers. 

Let us have a deep insight into the difference between VTVT and CRDI. 

VTVT is standing for variable valve timing valve train has ability to independent control of the intake and exhaust valves in an automobile engine on different engine load criteria.

CRDi stands for common rail direct injection is a fuel injection mechanism to supply the requisite amount of fuel at constant pressure and also to maintain a certain amount of pressurized reserve fuel during starting of the engine.

Mostly VTVT technology used for petrol engine while CRDi technology working for a diesel engine.

Application of belt drive

There are different variations of industrial machining application of belt drive that employ a wide range of different types of synchronous timing belt drive systems. 

Application of belt drive :

• Automobile timing belt 
• Treadmills
• Sewing machine
• Drilling machine with speed cone pulleys
• An open belt drive in a jig-saw machine
• Lathe machine with time belt
• A planner machine with guide pulleys 
• A flat belt in a circular saw machine