Automatic Pneumatic Grinding Machine: Working Principle and Applications

Last Updated on 27/01/2021


Selva Kumar
Kalasalingam University, Tamil Nadu, India


The automatic pneumatic grinding is a metal grinding machine tool designed to cut/grind metal by applying pneumatic pressure. It is widely used in carding machine to grind wire.

Automatic Pneumatic Grinding Machine
Fig: Automatic Pneumatic Grinding Machine

The automatic pneumatic grinding machine is exclusively intended for mass production and they represent the fastent and more efficient way to cut a metal. The slow speed operation is occurring in a grinding operation. This machine is a multipurpose machine.

Hacksaws are used to cut thin and soft metals. The grinding shaft is used to grinding operation by replacing the hacksaw frame. The operation of the unit is simplified to a few simple operations involving a cylinder block and piston arrangement.

There are numerous types of grinding machines in Engineering field, which are used to fulfil the requirements. We are interested to introduce automatic pneumatic system in especially in grinding machine and also grinding operation.

The main function of automatic pneumatic grinding machine is to cut thin and soft metals by pneumatic power.


The word ‘pneuma’ comes from Greek and means breather wind. The word pneumatics is the study of air movement and its phenomena is derived from the word pneuma. Today pneumatics is mainly understood to means the application of air as a working medium in industry especially the driving and controlling of machines and equipment.

Pneumatics has for some considerable time between used for carrying out the simplest mechanical tasks in more recent times has played a more important role in the development of pneumatic technology for automation.

Pneumatic systems operate on a supply of compressed air which must be made available in sufficient quantity and at a pressure to suit the capacity of the system. When the pneumatic system is being adopted for the first time, however it wills indeed the necessary to deal with the question of compressed air supply.

The key part of any facility for supply of compressed air is by means using reciprocating compressor. A compressor is a machine that takes in air, gas at a certain pressure and delivered the air at a high pressure.

Compressor capacity is the actual quantity of air compressed and delivered and the volume expressed is that of the air at intake conditions namely at atmosphere pressure and normal ambient temperature.

The compressibility of the air was first investigated by Robert Boyle in 1962 and that found that the product of pressure and volume of a particular quantity of gas.

The usual written as:

PV = C (or) PıVı = P2V2

In this equation the pressure is the absolute pressured which for free is about 14.7 Psi and is of courage capable of maintaining a column of mercury, nearly 30 inches high in an ordinary barometer. Any gas can be used in pneumatic system but air is the mostly used system now a days.

Mechanization is broadly defined as the replacement of manual effort by mechanical power. Pneumatic is an attractive medium for low cost mechanization particularly for sequential (or) repetitive operations. Many factories and plants already have a compressed air system, which is capable of providing the power (or) energy requirements and the control system (although equally pneumatic control systems may be economic and can be advantageously applied to other forms of power).

The main advantage of an all pneumatic system are usually economic and simplicity the latter reducing maintenance to a low level. It can also have outstanding advantages in terms of safety.

Pneumatic systems operate on a supply of compressed air, which must be made available. In sufficient quantity and at a pressure to suit the capacity of the system. When pneumatic system is being adopted for the first time, however it wills indeed the necessary to deal with the question of compressed air supply.

The key part of any facility for supply of compressed air is by means using reciprocating compressor. A compressor is a machine that takes in air, gas at a certain pressure and delivered the air at a high pressure.

Compressor capacity is the actual quantity of air compressed and delivered and the volume expressed is that of the air at intake conditions namely at atmosphere pressure and normal ambient temperature. Clean condition of the suction air is one of the factors, which decides the life of a compressor. Warm and moist suction air will result in increased precipitation of condense from the compressed air.

Compressor may be classified in two general types:

  1. Positive displacement compressor.
  2. Turbo compressor

Positive displacement compressors are most frequently employed for compressed air plant and have proved highly successful and supply air for pneumatic control application.

The types of positive compressor:

  1. Reciprocating type compressor
  2. Rotary type compressor

Turbo compressors are employed where large capacity of air required at low discharge pressures. They cannot attain pressure necessary for pneumatic control application unless built in multistage designs and are seldom encountered in pneumatic service.

Built for either stationary (or) portable service the reciprocating compressor is by far the most common type. Reciprocating compressors lap be had is sizes from the smallest capacities to deliver more than 500 m³/min. In single stage compressor, the air pressure may be of 6 bar machines discharge of pressure is up to 15 bars. Discharge pressure in the range of 250 bars can be obtained with high pressure reciprocating compressors that of three & four stages.

Single stage and 1200 stage models are particularly suitable for pneumatic applications, with preference going to the two-stage design as soon as the discharge pressure exceeds 6 bar, because it in capable of matching the performance of single stage machine at lower costs per driving powers in the range.



Pneumatic cylinder
An air cylinder is an operative device in which the state input energy of compressed air i.e. pneumatic power is converted in to mechanical output power, by reducing the pressure of the air to that of the atmosphere.

Single acting cylinder
Single acting cylinder is only capable of performing an operating medium in only one direction. Single acting cylinders equipped with one inlet for the operating air pressure, can be production in several fundamentally different designs.

Single cylinders develop power in one direction only. Therefore, no heavy control equipment should be attached to them, which requires to be moved on the piston return stoke single action cylinder requires only about half the air volume consumed by a double acting for one operating cycle.

Double acting cylinders:
A double acting cylinder is employed in control systems with the full pneumatic cushioning and it is essential when the cylinder itself is required to retard heavy messes. This can only be done at the end positions of the piston stock. In all intermediate position a separate externally mounted cushioning derives most be provided with the damping feature.

The normal escape of air is out off by a cushioning piston before the end of the stock is required. As a result, the sit in the cushioning chamber is again compressed since it cannot escape but slowly according to the setting made on reverses. The air freely enters the cylinder and the piston stokes in the other direction at full force and velocity.

Various types of control valves are used to regulate, control and monitor the air energy for control of direction pressure, flow, etc.

Pneumatic energy is regulated and controlled by pneumatic valves. Functionally valves are divided into four major groups.

  • Direction Control
  • Flow Control

In our project electrically actuated solenoid operated 5/2 DC valves are used.

Solenoid is another name for an electromagnet. Direction control valves are very often actuated by electromagnets. An electromagnet is a temporary magnet. A magnetic force is developed in an electromagnet when electrical current passes through it and force drops down as soon as it is de energized.

This electromagnet is commonly termed as solenoid. The proper working of a solenoid operated valve depends on the reliability of the electromagnets.

It ensures

  • Quick and sure action
  • Long life.
  • Easy maintenance.
  • Less wastage of energy.

Solenoid Valve
The directional valve is one of the important parts of a pneumatic system. Commonly known as DCV, this valve is used to control the direction of air flow in the pneumatic system. The directional valve does this by changing the position of its internal movable parts.

This valve was selected for speedy operation and to reduce the manual effort and also for the modification of the machine into automatic machine by means of using a solenoid valve. A solenoid is an electrical device that converts electrical energy into straight line motion and force. These are also used to operate a mechanical operation which in turn operates the valve mechanism.

Solenoids may be push type or pull type. The push type solenoid is one in which the plunger is pushed when the solenoid is energized electrically. The pull type solenoid is one is which the plunger is pulled when the solenoid is energized.

The name of the parts of the solenoid should be learned so that they can be recognized when called upon to make repairs, to do service work or to install them.

Solenoid Valve
Fig: Solenoid Valve

It is provided for the passage of compressed air from the compressor outlet to the operating valve.

Two separate pipes also connect the operating valve with the working cylinder pressure drop through and airline depends on the flow rate, pipe diameter, pipe length and pipe geometry. It can be determined directly for straight pipes of any given length. A small chaining bore size can have marked effect on pressure drop, whereas even doubling the pipe length, will only result in doubling the pressure drop.

Pressure drop through bends and fittings can only be determined by empirical tests, since it is specific to the internal geometry involved. Rigid pipes however are less manipulated through remain form of bends with arrangements increase and variable air have to flow and the flow itself may be of fluctuating or pulsating nature. In this case it is thus normally based on practical recommendation.

Seal is an important component of a pneumatic system and is used to prevent the air leakage through the joint.

This project passes the static seal which are used to prevent the leakage through the stationary surface.

Material of the seal is Teflon tape. Teflon has the following properties:

  • Withstand the system pressure and temperature without any damage.
  • Resist the wear and abrasion.
  • Recover from deformation.
  • Resists the adverse effects such as deterioration and shrinking caused by the system air.

Seals are devices for closing gaps to prevent leakage or make pressure joints and also to prevent the entry of air and dirt from outside into the system. The material of seal must be compatible with the fluid medium. It is a circular ring made of synthetic rubber. It is used for providing tight sealing between the piston and the cylinder wall. It prevents air leakage from the top and bottom of the cylinder.

Seals for air cylinder and valves are not normally called upon to seal pressure higher than about 2 bars. Since the fluid to be seated is a gas, (in our case air) rubbing speeds tends to be high and the seal the seal may have to be operated under dry conditions with minimal lubrication.


Need for a Timer Circuit:
Main purpose to timer circuit is to actuate the solenoid valve at regular interval of time to achieve proper lubrication at the desired interval.

Here the 555 IC has been used as a multi vibrator. The output of IC 555 is fed to the input pin (pin no 14) of CD 4017 continues counting.

The output of the IC becomes available at pin Nos. 3, 2 and 4. The output pulse of any one of output pin triggers (Puts ON) the Triac and current starts flowing across the load connected. This process continues on other pins at different time intervals and the cycle continues. The frequency interval (Time) of the cycle can be adjusted by the pre-set look connected to pin 6 of 555 Timer IC.

Automatic Grinding Machine
Fig: Diagram of Automatic Pneumatic Grinding Machine



Pneumatic circuit
Fig: Pneumatic circuit

Since pneumatic circuit plays a vital role in this device, it is very necessary to explain the working of this circuit.

Initially starting with air compresses, its function is to compress air from a low inlet pressure (usually atmospheric) to a higher-pressure level. This is an accomplished by reducing the volume of the air.

Air compressors are generally positive displacement units and are either of the reciprocating piston type or the rotary screw or rotary vane types. The air compressor used here is a typically small sized, two-stage compressor unit. It also consists of a compressed air tank, electric rotor and pulley drive, pressure controls and instruments for quick hook up and use. The compressor is driver by a 10HP motor and designed to operate in 145 – 175 PSI range. If the pressure exceeds the designed pressure of the receiver a release value provided releases the excesses air and thus stays a head of any hazards to take place.

The stored air from compressor is passed through an air fitter where the compressed air is filtered from the fine dust particles. However, before the suction of air into compressor a filter process take place, but not sufficient to operate in the circuit here the filter is used.

Then having a pressure regulator where the desired pressure to the operated is set. Here a variable pressure regulator is adopted.

Through a variety of direction control value are available, a hand operated solenoid Valve with control unit is applied.

The solenoid valve used here is 5 ports, 3 positions. There are two exhaust ports, two outlet ports and one inlet port. In two extreme positions only, the directions can be changed while the Centro ore is a neutral position and no physical changes are incurred.

The 2 outlet ports are connected to an actuator (Cylinder). The pneumatic activates is a double acting, single rod cylinder. The cylinder output is coupled to further purpose. The piston end has an air horning effect to prevent sudden thrust at extreme ends.


  • The compressed air from the compressor reaches the solenoid valve. The solenoid valve changes the direction of flow according to the signals from the timing device.
  • The compressed air pass through the solenoid valve and it is admitted into the front end of the cylinder block. The air pushes the piston for the grinding stroke. At the end of the grinding stroke air from the solenoid valve reaches the rear end of the cylinder block. The pressure remains the same but the area is less due to the presence of piston rod. This exerts greater pressure on the piston, pushing it at a faster rate thus enabling faster return stroke.
  • The weight attached at the end of the hacksaw frame gives constant loads which lower the hacksaw to enable continuous grinding of the work.
  • The stroke length of the piston can be changed by making suitable adjustment in the timer.
  • Grinding hacksaw frame is removed in the case of grinding operation. The above same procedure is occurring in the grinding operation.


1. Agriculture:

  • Crop forming
  • Stock breeding
  • Animal food industries
  • Foresting

2. Utilities:

  • Power Station
  • Nuclear Engineering
  • Water Supply

3. Mining
4. Chemical Industry
5. Plastics and rubber industries
6. Stone, Ceramic and glass industries
7. Metal Industries:

  • Iron and Steel
  • Non-ferrous metals
  • Foundries
  • Scrap and recycled metals

8. Leather Industry
9. Textile Industry
10. Paper and Printing Industry
11. Grinding Industries



  • There is no need of giving feed during every cut due to the presence of weight.
  • The grinding/grinding speed can be varied according to our needs by adjusting the timer.
  • It is portable
  • It does not have any Prime mover, like electric motor related to the unit.
  • As the air is freely available, we can utilize the air to cut the metal and hence it is economical.
  • Simple in construction than mechanical hacksaw and grinder
  • It is a compact one
  • Less Maintenance


  • Only smaller size and soft metal can be cut
  • It is costlier than the mechanical hacksaw because of compressor unit.
  • Less efficiency when compressed to mechanical device.
  • Leakage of air affects the working of the unit.


Sl. No.PARTSQty.Cost
i.Cylinder block (with piston)1
ii.Solenoid valve1
iii.Machine vice1
iv.Timing device1
v.Flexible hoses
vi.Hack Saw frame1
vii.Bolts & Nuts
viii.PU Connectors
ix.Flow Control Valve1
xGrinding Shaft1


The overhead charges are arrived by “Manufacturing cost”

Manufacturing Cost = Material Cost + Labour cost

Overhead Charges = 20% of the manufacturing cost

Total cost = Material Cost + Labour cost + Overhead Charges

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