DESIGN AND FABRICATION OF POKA YOKE

PNEUMATIC FIXTURE FOR MILLING AND SHAPER

MACHINE

A Project Report

Submitted By-

Arun Singh Rathore, Mohit Verma, Shubham Bagi, Shubham

Dhaneshree, Shubham Mathur, Shubham Singh Rathore.

Towards Partial Fulfillment for the Award of

Bachelor of Engineering (Mechanical Engineering)

Guided By-

Prof. Pankaj Gera

Department of Mechanical Engineering Mahakal Institute of Technology &

Science, Ujjain

Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal

2016-2017

MAHAKAL INSTITUTE OF TECHNOLOGY & SCIENCE, UJJAIN

(Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal M.P.)

(2016-2017)

CERTIFICATE

This is to certify that Mr Arun Singh Rathore, Mr. Mohit Verma, Mr. Shubham Bagi, Mr.

Shubham Dhaneshree and Mr. Shubham Mathur, Shubham Singh Rathore. Student of B.E.

(Mechanical Engineering Department) of this college has carried out Project “DESIGN AND

FABRICATION OF POKA YOKE PNEUMATIC FIXTURE FOR MILLING AND SHAPER

MACHINE.”

It is submitted towards partial fulfillment of the requirements for the award of Bachelor of

Engineering in Mechanical Engineering from Mahakal Institute of Technology & Science;

Ujjain affiliated to Rajiv Gandhi Proudyogiki Vishwavidyalaya, Bhopal (M.P.).

Prof. Pankaj Gera Prof. Santosh Vyas Prof. V.M. Shah

Project Guide Head of Department Director

M.I.T.S., Ujjain M.I.T.S., Ujjain M.I.T.S., Ujjain

ACKNOWLEDGEMENT

The successful completion of the project is the result of dedicated efforts of many people and

this report would be incomplete without giving due credit to them. This acknowledgement is

taken of small gratitude in recognition of the help provided by them.

We wish to express our heartfelt appreciation to all the people who had contributed to this

project, both explicitly and implicitly. First to all we want to thank our projects guide Prof.

Pankaj Gera for giving us this opportunity to work under his guidance. His empathy towards

us made our work easy. Many thank to him for encouraging and supporting us to complete this

project work. We are thankful to Prof. Santosh Vyas Head of the Department, Mechanical

Engineering and Prof. V.M Shah Director Mahakal Institute Of Technology & Science, Ujjain

for understanding our problem and shorting them out. We are thankful to staff of Mechanical

Engineering Department for letting us know about problem of industry and encouraging us to

work on it. In the last but not least, we are also thankful to all the persons and colleagues who

have helped us directly or indirectly during this project.

Arun Singh Rathore

Mohit Verma

Shubham Bagi

Shubham Dhaneshree

Shubham Mathur

Shubham Singh Rathore

DECLARATION

We final year students of B.E. (Mechanical Engineering) hereby declare that

major project work titled as “DESIGN AND FABRICATION OF POKA YOKE

PNEUMATIC FIXTURE FOR MILLING AND SHAPER MACHINE” is

original to the best of our knowledge and has not been submitted in any institute

or university under Bachelor of Engineering program.

NAMES & SIGNATURES OF STUDENTS WITH DATE

1. Arun Singh Rathore

2. Mohit Verma

3. Shubham Bagi

4. Shubham Dhaneshree

5. Shubham Mathur

6. Shubham Singh Rathore

ABSTRACT

As the modern industries are shifting towards the automation, most of the industrial production

is held by the aid of robots and in such boom of modernization the main problem that was face

by the industries is to held work piece and proper position during machining work. Because of

heavy machineries cutting forces and due to little care needed on the automation work quality

of the automation fabricated product is little bit lesser than expectation. Hence it is must to

design a rigid and efficient work holding device called jigs and fixtures. Work holding and

releasing is the most essential act to carry out machining to hold the job in proper position. To release

the job quickly and hold the job rigidly, to prevent the vibrations of the job while the machining is

carried out we are using mechanical work holding devices. In this project we are dealing with pneumatic

fixture used in milling or shaper machines. In pneumatic type piston cylinder arrangement one end of

piston rod is connected to the movable jaw and the piston slides in the cylinder. Here the air actuates

the movement of the piston this in turn actuates the movable jaw. Here the principle movement is only

a reciprocating movement. Pneumatic systems are safer than electromotive systems because they

can work in inflammable environment without causing fire or explosion. Apart from that,

overloading in pneumatic system will only lead to sliding or cessation of operation. Unlike

electromotive components, pneumatic components do not burn or get overheated when

overloaded. The operation of pneumatic systems does not produce pollutants. The air released

is also processed in special ways. Therefore, pneumatic systems can work in environments that

demand high level of cleanliness. And use of pneumatic systems in turn reduces the

manufacturing times of jobs by a significant amount, hence increasing the production

efficiency.

Keywords: Jigs, Fixtures, Pneumatic Vice, Job.

CONTENTS page no.

Acknowledgement i

Abstract ii

CHAPTER 1: Introduction 1-10

1.1 Pneumatics and Compressed Air 2

1.2 Poka-Yoke 5

1.3 Jigs and Fixtures 8

CHAPTER 2: Literature Review 11-13

2.1 Principle of Locations 11

2.2 Design Considerations in Fixtures 12

2.3 Clamping Approach 12

CHAPTER 3: Apparatus and Tool Used 14-23

3.1 Compressor 14

3.2 Cylinder 17

3.3 Direction Control Valve 18

3.4 Pressure and Flow Control Valve 21

CHAPTER 4: Methodology 24-28

4.1 Design Criteria for Fixtures 24

4.2 Making of Fixtures 25

4.3 Material Selection 27

CHAPTER 5: Result and Analysis 29-35

Conclusion 36

References 37

LIST OF FIGURES

Figure Description Page no.

Figure 1.1 An example of Poka-Yoke 6

Figure 1.2 Jigs 8

Figure 1.3 Fixtures 9

Figure 2.1 Scheme of 3-2-1 Fixture Setup 11

Figure 2.2 Layout of Working 12

Figure 2.3 Fixture Design for the Sample Part 13

Figure 3.1 Regular Reciprocating Compressor 14

Figure 3.2 Double Acting Cylinder 18

Figure 3.3 Direction Control Valve 20

Figure 3.4 Pneumatic Flow Control Valve 21

Figure 3.5 Pressure control valve 22

Figure 3.6 PU tubes 23

Figure 4.1 Forces impact on work holding design 24

Figure 4.2 Locating Pins 25

Figure 4.3 Pneumatic Power Clamp 26

LIST OF TABLES

Table no. Name of table Page no.

4.1 List of Component Used 28

5.1 Maximum clamping force calculations 31

5.2 Table Comparative Analysis 34

CHAPTER 1

INTRODUCTION

One of the most time-consuming and labor extensive processes in the manufacturing of a

mechanical part is the process of work holding or fixturing. It is often remarked that only

approximately 10-15% of the overall time required to produce a part is spent

Actually on cutting or drilling a work piece; the other time is spent primarily planning for

executing part setup or work holding which is still performed by highly skilled Machinists

based on their experience. Recently, industries have begun to experience Difficulty finding

highly skilled machinists because the number of apprentices is decreasing and it is likely that

the situation will worsen in the future. As a result of this trend together with the increasing

power of computation speed, there has been a vast activity devoted to analyze the stability of

fixturing and to automate fixture designs via CAD techniques. A fixture may constrain the

motion of work pieces in two different ways. One, form closure, is purely kinematics, in which

the geometry of the contacting rigid parts prevents motion regardless of the magnitude of the

applied force. The other, force closure, involves the use of friction to assist in the freedom of

motion of a kinematically under constrained object. Most analyses focused on the stability of

the final fixture configurations and were less concerned on the sequence of placing the fixels.

Based on the theories of grasping planar objects demonstrated that improper sequence of

placing the fixels will result in the rotation of the planar work pieces. Instead of focusing on

the fixturing of planar work pieces which ignores the sequence of placing the overhead clamp

that is consider the fixturing of prismatic work pieces which are polyhedral objects with all

outer boundary faces either parallel or perpendicular to the fixture base plate. It is shown that

proper sequences of placing clamps can actually relax the stringent requirement in the

positioning accuracy of the fixels. So, in order to design a complete set or perfect jigs and

fixtures, the determination about all the factors which are influence the jigs and fixtures during

machining process is important. The factors are force, pressure, weight, cutting speed and

others.

1.1 Pneumatics and Compressed Air

Pneumatics (pronounced new-MATT-ix) is an aspect of physics and engineering that is concerned

with using the energy in compressed gas to make something move or work. “Pneumos” means “Air”

and “Tics” means “Technology Pneumatics is using air to push/pull things or suck them up. The origins

of pneumatics trace back to the first century when the Greek mathematician Hero of Alexandria created

mechanical systems powered by wind and steam and documented his processes. Today, pneumatics

plays an important role in manufacturing and mechatronics.

With pneumatics, valves control the flow of energy from pressurized gas, which is often

simply compressed air. The device that converts energy from the pressurized gas into motion is called

a pneumatic actuator. Pneumatic actuators are often powered by electric compressors and are capable

of producing either linear or rotary motion. A nail gun is an example of a linear pneumatic actuator.

When the user pulls the nail gun's trigger, a valve opens and compressed air is released with enough

force to drive the nail into a solid surface. In manufacturing, pneumatic technology and

automated solenoid valves can be used in an assembly line to move process and package product.

An incredible range of manufacturing systems use the force and power of fluids such as water, oil and

air. Powered clamps open and close with the force of pressurized air or oil, large presses shape and form

metal with hydraulic pressure, and assembly torque tools fasten components with pressurized air. In

each example, fluid power provides the energy necessary to exert significant mechanical forces.

Systems that use air are called pneumatic systems while systems that use liquids like oil or water are

called hydraulic system. Pneumatic systems are similar to hydraulics in function, but hydraulic systems

use liquid to power movement and work instead of gas. Pneumatic systems are simpler to design and

simpler to manage than hydraulic systems, but hydraulic systems are capable of greater pressures: up

to 10,000 PSI (pounds per square inch) with hydraulics, compared to about 100 PSI with pneumatics.

In general pneumatic systems are more sustainable than hydraulic systems because air can be exhausted

into the atmosphere, while hydraulic fluid must be exhausted into a fluid reservoir and eventually

disposed of.

Both these systems (hydraulic and pneumatic) are used in industry as per need and convenience.

Pneumatic systems in fixed installations, such as factories, use compressed air because a sustainable

supply can be made by compressing atmospheric air. The air usually has moisture removed, and a small

quantity of oil is added at the compressor to prevent corrosion and lubricate mechanical components.

Advantages of Pneumatic Systems

Pneumatic control systems are widely used in our society, especially in the industrial sectors for the

driving of automatic machines. Pneumatic systems have a lot of advantages.

1. High effectiveness

Many factories have equipped their production lines with compressed air supplies and movable

compressors. There is an unlimited supply of air in our atmosphere to produce compressed air.

Moreover, the use of compressed air is not restricted by distance, as it can easily be transported

through pipes. After use, compressed air can be released directly into the atmosphere without the

need of processing.

2. High durability and reliability

Pneumatic components are extremely durable and cannot be damaged easily. Compared to

electromotive components, pneumatic components are more durable and reliable.

3. Simple design

The designs of pneumatic components are relatively simple. They are thus more suitable for use in

simple automatic control systems.

4. High adaptability to harsh environment

Compared to the elements of other systems, compressed air is less affected by high Temperature,

dust, corrosion, etc.

5. Safety

Pneumatic systems are safer than electromotive systems because they can work in inflammable

environment without causing fire or explosion. Apart from that, overloading in pneumatic system

will only lead to sliding or cessation of operation. Unlike electromotive components, pneumatic

components do not burn or get overheated when overloaded.

6. Easy selection of speed and pressure

The speeds of rectilinear and oscillating movement of pneumatic systems are easy to adjust and

subject to few limitations. The pressure and the volume of air can easily be adjusted by a pressure

regulator.

7. Environmental friendly

The operation of pneumatic systems does not produce pollutants. The air released is also processed

in special ways. Therefore, pneumatic systems can work in environments that demand high level of

cleanliness. One example is the production lines of integrated circuits.

8. Economical

As pneumatic components are not expensive, the costs of pneumatic systems are quite low.

Moreover, as pneumatic systems are very durable, the cost of repair is significantly lower than that

of other systems.

Compressed Air

Compressed air is a gas, or a combination of gases, that has been put under greater pressure than the air

in the general environment. This compressed air possesses great amount of energy which can be utilized

to do a great deal of work and operations in an industry; like lifting, moving or holding of humongous

objects to perform various mechanical operations upon them. To understand how compressed air is able

to do things, let’s think of a ball. If we blow up the ball so that it is full, it will contain a lot of compressed

air. If we bounce the ball, it will bounce very high. However, if the ball is burst then the compressed air

will escape and the ball will not bounce as high. Quite simply, the ball bounces because it is using the

energy stored in the compressed air.

It serves many domestic and industrial purposes. Current applications using compressed air are

numerous and diverse, including jackhammers, tire pumps, air rifles, and aerosol cheese. According to

proponents, compressed air also has a great potential as a clean, inexpensive, and infinitely renewable

energy source. Its use is currently being explored as an alternative to fossil fuels.

In 1991, the first compressed air energy storage (CAES) plant in the United States opened in McIntosh,

Alabama. The world's largest CAES plant, planned for Norton, Ohio, is expected to store sufficient

energy to provide electric power for 675,000 homes for two days. Another product that uses compressed

air is the so-called "air car" currently in development by several manufacturers, and expected to be on

the market within the next few years. According to "How Stuff Works," one such car, the e-Volution,

will run 120 miles without refueling, at a cost of about 30 cents. Compressed air in spray cans

(sometimes called canned air) is often used to clean things that are especially delicate or sensitive, such

as keyboards or the inside of computer cases. This explains that compressed air usage in cost effective

and easy.

Although in industry, compressed air is so widely used that it is often regarded as the fourth utility, after

electricity, natural gas and water. However, compressed air is more expensive than the other three

utilities when evaluated on a per unit energy delivered basis. A large number of operations are

performed in industries with the help of compressed air. Compressed air generations in industries

accounts for up to 10% of total industrial electricity consumption. Hence it is optimal to use compressed

air for making a vice for holding jobs and to operate pneumatic machines as it is in abundance and can

be manufactured easily.

1.2 Poka-Yoke

Poka-yoke [poka joke] is a Japanese term that means "mistake-proofing" or “inadvertent error

prevention”. The key word in the second translation, often omitted, is "inadvertent". There is

no Poka Yoke solution that protects against an operator’s sabotage, but sabotage is a rare

behavior among people. A poka-yoke is any mechanism in a lean manufacturing process that

helps an equipment operator avoid (yokeru) mistakes (poka). Its purpose is to eliminate product

defects by preventing, correcting, or drawing attention to human errors as they occur. The

concept was formalized, and the term adopted, by Shigeo Shingo as part of the Toyota

Production System. It was originally described as baka-yoke, but as this means "fool-proofing"

(or "idiot-proofing") the name was changed to the milder poka-yoke.

More broadly, the term can refer to any behavior-shaping constraint designed into a process to

prevent incorrect operation by the user.

A simple poka-yoke example is demonstrated when a driver of the car equipped with a manual

gearbox must press on the clutch pedal (a process step, therefore a poka-yoke) prior to starting

an automobile. The interlock serves to prevent unintended movement of the car. Another

example of poka-yoke would be the car equipped with an automatic transmission, which has a

switch that requires the car to be in "Park" or "Neutral" before the car can be started (some

automatic transmissions require the brake pedal to be depressed as well). These serve as

behavior-shaping constraints as the action of "car in Park (or Neutral)" or "foot depressing the

clutch/brake pedal" must be performed before the car is allowed to start. The requirement of a

depressed brake pedal to shift most of the cars with an automatic transmission from "Park" to

any other gear is yet another example of a poka-yoke application. Over time, the driver's

behavior is conformed to the requirements by repetition and habit.

Fig 1.1 an example of Poka-Yoke

Poka-yoke can be implemented at any step of a manufacturing process where something can

go wrong or an error can be made. For example, a fixture that holds pieces for processing might

be modified to only allow pieces to be held in the correct orientation, or a digital counter might

track the number of spot welds on each piece to ensure that the worker executes the correct

number of welds.

Shigeo Shingo recognized three types of Poka-yoke for detecting and preventing errors in a

mass production system:

1. The contact method identifies product defects by testing the product's shape, size, color,

or other physical attributes.

2. The fixed-value (or constant number) method alerts the operator if a certain number of

movements are not made.

3. The motion-step (or sequence) method determines whether the prescribed steps of the

process have been followed.

Either the operator is alerted when a mistake is about to be made, or the poka-yoke device

actually prevents the mistake from being made. In Shingo's lexicon, the former implementation

would be called a warning poka-yoke, while the latter would be referred to as a control poka-

yoke.

Shingo argued that errors are inevitable in any manufacturing process, but that if appropriate

poka-yokes are implemented, then mistakes can be caught quickly and prevented from resulting

in defects. By eliminating defects at the source, the cost of mistakes within a company is

reduced.

A methodic approach to build up poka-yoke countermeasures has been proposed by the

Applied Problem Solving (APS) methodology, which consists of a three-step analysis of the

risks to be managed:

1. identification of the need

2. identification of possible mistakes

3. management of mistakes before satisfying the need

This approach can be used to emphasize the technical aspect of finding effective solutions

during brainstorming sessions.

Benefits of Poka Yoke implementation

Less time spent on training workers;

Elimination of many operations related to quality control;

Unburdening of operators from repetitive operations;

Promotion of the work improvement-oriented approach and actions;

A reduced number of rejects;

Immediate action when a problem occurs;

100% built-in quality control.

1.3 Jigs and Fixtures

The jigs and fixtures are the economical ways to produce a component in mass. So jigs and fixtures are

used and serve as one of the most important facility of mass production system. These are special work

holding and tool guiding device. Quality of performance of a process is largely influenced by the quality

of jigs and fixtures used for this purpose. What makes a fixture unique is that each one is built to fit a

particular part or shape. The main purpose of a fixture is to locate and in the cases hold a work piece

during an operation. A jig differs from a fixture in the sense that it guides the tool to its correct position

or towards its correct movement during an operation in addition to locating and supporting the work

piece.

Figure 1.2 Jigs

An example of jig is when a key is duplicated; the original key is used as base for the path reader which

guides the movement of tool to make its duplicate key. The path reader of a CWC machine here works

as a jig and the original is called template. Sometimes the template and jig both are the name of same

part of a manufacturing system.

A fixture is a device used to locate, clamp and support a work piece during machining,

assembly or inspection. The most important criteria’s for fixturing are work piece stability,

position accuracy and work piece deformation. A good fixture design is one that minimizes

work piece geometric error. Work piece location principles are defined in terms of 3-2-1

fixturing which is widely used work piece location method for prismatic parts. Force analysis

is concerned with checking whether the forces applied by the fixture and clamping are

sufficient to maintain static equilibrium.

Fig. 1.3 Fixtures

Fixtures must correctly locate a work piece in a given orientation with respect to a cutting tool

or measuring device, or with respect to another component, as for instance in assembly or

welding. Such location must be invariant in the sense that the devices must clamp and secure

the work piece in that location for the particular processing operation. There are many standard

works holding devices such as jaw chucks, machine vises, drill chucks, collets, etc. which are

widely used in workshops and are usually kept in stock for general applications. Fixtures are

normally designed for a definite operation to process a specific work piece and are designed

and manufactured individually.

Purpose and advantages of Jigs and Fixtures

Following the purpose and advantages of jigs and fixtures:

(a) It reduces or sometimes eliminates the efforts of marking, measuring and setting of work piece on a

machine and maintains the accuracy of performance.

(b) The work piece and tool are relatively located at their exact positions before the operation

automatically within negligible time. So it reduces product cycle time.

(c) Variability of dimension in mass production is very low so manufacturing processes supported by

use of jigs and fixtures maintain a consistent quality.

(d) Due to low variability in dimension assembly operation becomes easy, low rejection due to les

defective production is observed.

(e) It reduces the production cycle time so increases production capacity. Simultaneously working by

more than one tool on the same work piece is possible.

(f) The operating conditions like speed, feed rate and depth of cut can be set to higher values due to

rigidity of clamping of work piece by jigs and fixtures.

(g) Operators working become comfortable as his efforts in setting the work piece can be eliminated.

(h) Semi-skilled operators can be assigned the work so it saves the cost of manpower also.

(i) There is no need to examine the quality of produce provided that quality of employed jigs and fixtures

is ensured.

Importance of Fixtures in Manufacturing

The use of fixtures has two fold benefits. It eliminates individual markings positioning and frequent

checking before machining operation starts, thereby resulting in considerable saving in set-up time. In

addition, the usage of work holding devices saves operator labor through simplifying locating and

clamping tasks and makes possible the replacement of skilled workforce with semiskilled labor, hence

effecting substantial saving in labor cost which also translates into enhanced production rate.

Furthermore, the use of well-structured fixtures with higher locating and clamping rigidity would allow

for increase in cutting speeds and feeds, thereby reducing tm, hence improving production rate. Besides

improving the productivity in Terms of the rate of production, there are also other benefits accrued

through the use of Fixtures, they are: It Increases machining accuracy because of precise location with

fixtures.

CHAPTER 2

LITERATURE REVIEW

2.1 Principles of Locations

Guohua Qin et al., (2006), focuses on the fixture clamping sequence. It consists of two parts:

a. For the first time he evaluated varying contact forces and work piece position errors in each

clamping step by solving a nonlinear mathematical programming problem. This is done by

minimizing the total complementary energy of the work piece-fixture system. The prediction

proves to be rigorous and reasonable after comparing with experimental data and referenced

results.

b. The optimal clamping sequence is identified based on the deflections of the work piece and

minimum position error. Finally, to predict the contact forces and to optimize the clamping

sequence three examples are discussed.

Fig. 2.1 Scheme of 3-2-1 Fixture Setup (Guohua Qin, Weihong, Zhang Min Wan, 2006)

First mathematical modeling for clamping sequence is done then he determined the contact

forces in clamping sequence as shown in Figure 1. After that he optimized of clamping

sequence for higher stiffness work pieceand low stiffness work piece. He found that with the

use of optimal clamping sequence, good agreements are achieved between predicted results

and experimental data and the work piece machining quality can be improved.

2.2 Design Consideration in Fixtures

The importance of fixture design automation is emphasized by Djordje Vukelic (Michael

Stampfer, 2008). General structure of the automated design system is shown in Figure 2 with

a highlight on the fixture design systems and their main characteristics.

It also shows a structure and a part of output results of the automated modular fixture design

system. The expert systems have been mostly used for the generation of partial fixture

solutions, i.e. for the selection of locating and clamping elements.

Fig. 2.2: Layout of Working (Michael Stampfer, 2008)

Shrikant et al., (2013), discussed various design and analysis methods in the context of to

improve the life of fixture; different fixture geometries are compared experimentally and are

selected. The proposed eccentric shaft fixture will fulfilled researcher Production target and

enhanced the efficiency, fixture reduces operation time and increases productivity, high quality

of operation.

2.3 Clamping Approach

J Cecil proposed an innovative clamping design approach is described in the context of fixture

design activities. The clamping design approach involves identification of clamping surfaces

and clamp points on a given work piece. This approach can be applied in conjunction with a

locator design approach to hold and support the work piecework piece correctly with respect

to the cutting tool. Detailed steps are given for automated clamp design. Geometric reasoning

techniques are used to determine feasible clamp faces and positions. The required inputs

include CAD model specifications, features identified on the finished work piece, locator

points and elements.

Fig. 2.3: Fixture Design for the Sample Part (J Cecil, 2008)

CHAPTER 3

APPARATUS AND TOOL USED

There were various tools used while designing and making our projects. These are as follows:

3.1 COMPRESSOR

A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume.

An air compressor is a specific type of gas compressor. You'll find air compressors used in a wide range

of situations—from corner gas stations to major manufacturing plants. And, more and more, air

compressors are finding their way into home workshops, basements and garages. Models sized to

handle every job, from inflating pool toys to powering tools such as nail guns, sanders, drills, impact

wrenches, staplers and spray guns are now available through local home centers, tool dealers and

mail-order catalogs.

Fig 3.1 Regular Reciprocating Compressor

Like a small internal combustion engine, a conventional piston compressor has a crankshaft, a

connecting rod and piston, a cylinder and a valve head. The crankshaft is driven by either an

electric motor or a gas engine. While there are small models that are comprised of just the pump

and motor, most compressors have an air tank to hold a quantity of air within a preset pressure

range. The compressed air in the tank drives the air tools, and the motor cycles on and off to

automatically maintain pressure in the tank.

The big advantage of air power is that each tool doesn't need its own bulky motor. Instead, a

single motor on the compressor converts the electrical energy into kinetic energy. This makes

for light, compact, easy-to-handle tools that run quietly and have fewer parts that wear out.

Compressors are similar to pumps: both increase the pressure on a fluid and both can transport

the fluid through a pipe. As gases are compressible, the compressor also reduces the volume of

a gas. Liquids are relatively incompressible; while some can be compressed, the main action

of a pump is to pressurize and transport liquids.

An air compressor is a device that converts power (using an electric motor, diesel or gasoline

engine, etc.) into potential energy stored in pressurized air (i.e., compressed air). By one of

several methods, an air compressor forces more and more air into a storage tank, increasing the

pressure. When tank pressure reaches its upper limit the air compressor shuts off. The

compressed air, then, is held in the tank until called into use. The energy contained in the

compressed air can be used for a variety of applications, utilizing the kinetic energy of the air

as it is released and the tank depressurizes. When tank pressure reaches its lower limit, the air

compressor turns on again and re-pressurizes the tank.

Compressors can be classified according to the pressure delivered:

1. Low-pressure air compressors (LPACs), which have a discharge pressure of 150 psi or

less

2. Medium-pressure compressors which have a discharge pressure of 151 psi to 1,000 psi

3. High-pressure air compressors (HPACs), which have a discharge pressure above 1,000

psi

They can also be classified according to the design and principle of operation:

1. Rotary Screw compressors

2. Turbo or Axial Compressors.

There are other design types of compressors also, but the general type is given above. These

are also differentiated on the basis of method of displacement of air in the compressors.

There numerous methods of air compression, divide it into either positive-displacement or roto-

dynamic types.

Positive displacement

Positive-displacement compressors work by forcing air into a chamber whose volume is

decreased to compress the air. Once the maximum pressure is reached, a port or valve opens

and air is discharged into the outlet system from the compression chamber. Common types of

positive displacement compressors are:

Piston-type: air compressors use this principle by pumping air into an air chamber

through the use of the constant motion of pistons. They use one-way valves to guide air

into a cylinder chamber, where the air is compressed.

Rotary screw compressors: use positive-displacement compression by matching two

helical screws that, when turned, guide air into a chamber, whose volume is decreased

as the screws turn.

Vane compressors: use a slotted rotor with varied blade placement to guide air into a

chamber and compress the volume. A type of compressor that delivers a fixed volume

of air at high pressures.

Dynamic Displacement

Dynamic displacement air compressors include centrifugal compressors and axial compressors.

In these types, a rotating component imparts its kinetic energy to the air which is eventually

converted into pressure energy. These use centrifugal force generated by a spinning impeller

to accelerate and then decelerate captured air, which pressurizes it.

Compressor The compressor works best when there is no air pressure in the system to resist

the pump. As the pressure increases the compressor labours longer to get more pressurized air

into the system. When at first the system is empty, the compressor can move a lot of air, but as

pressure builds up the compressor takes longer and longer to stuff more air in.

3.2 CYLINDER

Pneumatic cylinder(s) (sometimes known as air cylinders) are mechanical devices which use

the power of compressed gas to produce a force in a reciprocating linear motion. Like hydraulic

cylinders, something forces a piston to move in the desired direction. The piston is a disc or

cylinder, and the piston rod transfers the force it develops to the object to be moved. Engineers

sometimes prefer to use pneumatics because they are quieter, cleaner, and do not require large

amounts of space for fluid storage.

Because the operating fluid is a gas, leakage from a pneumatic cylinder will not drip out and

contaminate the surroundings, making pneumatics more desirable where cleanliness is a

requirement. For example, in the mechanical puppets of the Disney Tiki Room, pneumatics are

used to prevent fluid from dripping onto people below the puppets.

Single-acting cylinders

Single-acting cylinders (SAC) use the pressure imparted by compressed air to create a driving

force in one direction (usually out), and a spring to return to the "home" position. More often

than not, this type of cylinder has limited extension due to the space the compressed spring

takes up. Another downside to SACs is that part of the force produced by the cylinder is lost

as it tries to push against the spring

Double-acting cylinders

Double-acting cylinders (DAC) uses the force of air to move in both extends and retracts

strokes. They have two ports to allow air in, one for outstroke and one for in stroke. Stroke

length for this design is not limited; however, the piston rod is more vulnerable to buckling and

bending. Additional calculations should be performed as well.

Fig. 3.2 Double Acting Cylinder

Many hydraulic and pneumatic cylinders use them where it is needed to produce a force in both

directions. A double-acting hydraulic cylinder has a port at each end, supplied with hydraulic

fluid for both the retraction and extension of the piston. A double-acting cylinder is used where

an external force is not available to retract the piston or where high force is required in both

directions of travel.

3.3 DIRECTION CONTROL VALVE

DIRECTIONAL VALVES As the same name implies, directional valves start, stop, and

control the direction of fluid flow. Although they share this common function, directional

valves very considerably in construction and operation.

There are basically three types of valves employed in hydraulic systems:

a. Directional control valves

b. Flow control valves

c. Pressure control valves

a. Directional control valves:- Directional control valves are used to control the distribution of

energy in a fluid power system. They provide the direction to the fluid and allow the flow in a

particular direction. These valves are used to control the start, stop and change in direction of

the fluid flow. These valves regulate the flow direction in the hydraulic circuit.

Directional control valves can be classified in the following manner:

1. Type of construction:

• Poppet valves

• Spool valves

2. Number of ports:

• Two- way valves

• Three – way valves

• Four- way valves.

3. Number of switching position:

• Two – position

• Three – position

4. Actuating mechanism:

• Manual actuation

• Mechanical actuation

• Solenoid actuation

• Hydraulic actuation

• Pneumatic actuation

• Indirect actuation

b. Flow control valves: -The flow control valves work on applying a variable restriction in the

flow path. Based on the construction; there are mainly four types viz. plug valve, butterfly

valve, ball valve and balanced valve.

Fig. 3.3 Direction Control Valve

c. Pressure control/relief valves:-The pressure relief valves are used to protect the hydraulic

components from excessive pressure. This is one of the most important components of a

hydraulic system and is essentially required for safe operation of the system. Its primary

function is to limit the system pressure within a specified range. It is normally a closed type

and it opens when the pressure exceeds a specified maximum value by diverting pump flow

back to the tank. The simplest type valve contains a poppet held in a seat against the spring

force.

The direction control valve that has been used by us in this project is a 5*2 Manual Head lever

Valve.

3.3 PRESSURE AND FLOW CONTROL VALVE

Pressure-control valves are found in virtually every hydraulic system, and they assist in a

variety of functions, from keeping system pressures safely below a desired upper limit to

maintaining a set pressure in part of a circuit. Types include relief, reducing, sequence,

counterbalance, and unloading. All of these are normally closed valves, except for reducing

valves, which are normally open. For most of these valves, a restriction is necessary to produce

the required pressure control. One exception is the externally piloted unloading valve, which

depends on an external signal for its actuation.

Pneumatic Pressure and Flow Control Valves

Pneumatic valves circulate air throughout a larger pneumatic system by either allowing or

inhibiting the flow of pressurized air, whose force is then used to power a device.

Fig. 3.4Pneumatic Flow Control Valve

Because valves can have varying numbers of entryways for air, creating different flow patterns,

valves are classified according to the number of ports they possess and the flow-paths they

create. Additionally, because they can move air in a variety of ways they can suit a variety of

applications. Aside from the commonly used directional control valves, there are valves that

are designed to serve more specific purposes, such as pressure regulator, venting-type regulator

valves, and needle valves. Pressure and venting-type valves both help control pressure, whereas

needle valves help control the flow within a pneumatic system.

Pressure Regulators

A pressure regulator is responsible for preventing pressure fluctuation by controlling pressure

as it is coursed through an actuator or another part of a pneumatic system. In order to air

pressure within an appropriate pressure range, the pressure should be set low enough so that it

can fluctuate between 3 and 5 psi without altering the minimum and maximum pressure system

requirements. In certain applications, a pressure regulator valve must ensure that air-pressure

output stays at a constant regardless of changes in pressure at earlier points in the system and

changes in flow. Other applications require pressure regulators to lower pressure so that air

isn’t wasted while still meeting the basic pressure requirements of the device.

Fig. 3.5 Pressure Control Valve

Pressure regulators work with sensors to monitor the pressure as it expands as it moves through

a pneumatic system. Once the pressure has reached the maximum level of expansion, a sensor

is triggered by the high pressure, which in turn signals to the pressure valve to close thus cutting

off pressure. As a result of the pressure valves opening and closing in response to pressure

levels, pressure is kept at a relatively constant level as it reaches the actuator or other pneumatic

device.

3.5 Pneumatic Tubes

Pneumatic tubes (or capsule pipelines; also known as Pneumatic Tube Transport or PTT)

are systems that propel cylindrical containers through networks of tubes by compressed air or

by partial vacuum. They are used for transporting solid objects, as opposed to conventional

pipelines, which transport fluids. Pneumatic tube networks gained acceptance in the late 19th

and early 20th centuries for offices that needed to transport small, urgent packages (such as

mail, paperwork, or money) over relatively short distances (within a building, or, at most within

a city). Some installations grew to great complexity, but were mostly superseded. In some

settings, such as hospitals, they remain widespread and have been further extended and

developed in recent decades.

Fig. 3.6 PU tubes

CHAPTER 4

METHODOLOGY

In design methodology the whole study of arrangements are taken in account. We divide the

whole project or research into various steps in which the whole model of project is

manufactured. These steps based on principles and concepts of production technology, which

are used as follows.

4.1 Design criteria for Fixtures

A work holding device is a tool that establishes a relationship between the work piece and the

machine tool. Every work holding device is designed to securely support, locate, and hold the

work piece as it sustains machining forces, as shown in Figure 4.1. However, many variables

affect the design of an effective customized fixture for any given machining operation. The

responsibility of the designer is to create a fixture that is sturdy, easy to use, and inexpensive.

An effective fixture also reduces nonproductive time spent on tasks other than machining. The

designer plays a crucial role in maintaining quality while increasing production.

Fig. 4.1 Machining forces impact workholding design

4.2 Making of Fixture

After the base plate is selected, the designer must choose the appropriate components for

supporting the workpiece. Besides size and shape, the material of the workpiece will greatly

affect workholding design. A workpiece made of aluminum or other soft material will generate

less cutting forces. However, softer materials may distort and bend, especially while cutting.

Extra support may be necessary to prevent this distortion during machining.

With high-carbon steels, tool steels, or other harder materials, the designer must anticipate

greater cutting forces. Harder materials experience less distortion. However, supporting

components must be able to resist these increased cutting forces. Supports must also be able to

withstand the wear encountered by the loading and unloading of parts. Regardless of the

material, the workpiece must always be supported near the location of the machining. In this

project, the material that is used for supporting is mild steel for making the fixture, bed and for

fasteners.

Locating Pins

Locating pins are used to hold the workpiece at its desired place or to align it in order to perform

operations on it. Locating pins are a great way to make sure the parts you are putting together

fit the way you want them to fit. Drill two holes opposite each other in each part; install a

cylindrical locating pin, and presto! Your parts are aligned exactly the way you want.

There are two ways for locating an object, internal locating and external locating. If internal

holes are not feasible, the designer can locate the part externally using the 3-2-1 method, as

demonstrated in Figure 4.2.

Fig. 4.2 External Location requires location on several surfaces.

According to the 3-2-1 method, the workpiece must be supported by at least three points from

below. The rest buttons accomplish this task. The workpiece must also be located along an axis

by two points, which is satisfied by the two locating pins at the top and right. Finally, the

workpiece must be located along an axis perpendicular to the previous axis by a single point.

This method is implemented as an option for locating the workpiece in our project.

For any workholding assignment, the designer has numerous tools and components available.

Every workholding device must accurately support, locate, and hold the workpiece. Generally

manual clamps are used on small machines. Since, manual clamps may increase the time

required to load and unload a workpiece, this introduces a labor cost. Flat angle clamping bars

are used for clamping the workpiece. Another option for the designer is power clamping. If

power clamps such as the system in our project as shown in Figure 4.3 are used, the operator

can clamp the workpiece with a flick of a switch. Because they are driven by hydraulic power

or pneumatic power, the clamping force is always the same and is evenly distributed to all the

clamps. Most importantly, the time required for securing parts is greatly reduced. As

compressed gas for pneumatic components is easily available in industries, power clamping

turns out to be a cost effective when used large manufacturing.

Fig. 4.3 Pneumatic Power Clamp

Modern manufacturing is a race to produce the greatest number of high quality parts in the least

amount of time. As time increases, the cost of the part increases as well. As you might imagine,

the workholding setup plays a key role in reducing the time it takes to make a part.

An effective fixture can reduce nonproductive time. A fixture effectively secures more parts

with fewer clamps. Nonproductive time includes setup time spent setting up the fixture,

calculating tool offsets, and other tasks required to make the first good part. However,

nonproductive time also includes more general tasks such as loading and unloading the part,

part checking, tool changes, etc.

A basic truism of the shop is that if you are not producing chips, you are not making money.

An effective workholding setup reduces the amount of nonproductive time and helps keep a

machine running.

The responsibility of the tool designer is to create a fixture that is sturdy, easy to use, and

inexpensive. The design of the plate fixture begins with the selection of a base plate, which

acts as the tool body containing all the workholding components. Besides size and shape, the

material of the workpiece and the operations performed greatly affect workholder design.

First, supporting components are used to resist cutting forces and sustain wear. Second,

locating pins are strategically placed to prevent the workpiece from sliding. Finally, clamping

prevents the workpiece from lifting off the supports and out of the fixture. Clamps should be

secured over supports to prevent distortion of the workpiece.

These workholding steps are often best accomplished with the use of standard components.

Workholding components are generally hardened to resist wear and ground to precise

dimensions. An effective fixture can also be an opportunity to reduce nonproductive time and

increase overall efficiency.

4.3 Material Selection

The selection of material used depends upon the forces and vibrations generated while

operating on the workpiece. The materials selected are for two components namely, the base

of the project and the base plate of the fixture.

The base of the project is made of wooden ply; the whole project is assembled and fastened on

this ply.

Whereas the material of the base plate of the fixture is mild steel. Since the force generated by

a drill or a milling machine on the fixture is not very high hence the material should not be very

tough or brittle. Mild steel is chosen over other materials because it is rigid and resilient in

absorbing sudden loads and vibrations on fixture plate.

Other components used are incorporated by us from their OEM (original equipment

manufacturer for the components used).

These components are listed as follows.

S.No. Component Qty. Specifications

1 Double Acting Cylinder 1 Pressure: 1.5-8 Kgf/cm2

2 Direction Control Valve 1 Pressure: 0.15-0.85 MPa

3 Pressure Control Valve 1 Pressure: 0-10 Kgf/cm2

4 Fluid flow Regulators 2 1/8 inch

5 Pneumatic Pipes 4 6mm,8mm

6 Silencers 2 1/8 inch

Table 4.1 List of Components Used.

CHAPTER 5

RESULTS AND ANALYSIS

FORCE

The fluid pushes against the face of the piston and produces a force. The force produce is given

by the formula.

F = PA

P is the pressure in N/m2 and A is the area the pressure acts on in m2.

This assumes that the pressure on the other side of the piston is negligible. The diagram shows

a double acting cylinder. In this case the pressure on the other side is usually atmospheric so if

p is a gauge pressure we need not worry about the atmospheric pressure.

Let A be the full area of the piston and a be the cross sectional area of the rod. If the pressure

is acting on the rod side, then the area on which the pressure acts is (A-a).

F= P A on the full area of piston.

F= P (A-a) on the rod side.

This force acting on the load is often less because of friction between the seals and both the

piston and piston rod.

SPEED

The speed of the piston and rod depends upon the flow rate of fluid. The volume per second

entering the cylinder inside. It follows then that.

Q m3/ s =Area * distance moved per second

Q m3/s=A*velocity (full side)

Q m3/s= (A-a)* velocity (rod side)

Note in calculus form velocity is given by v= A dx/dt this is useful in control applications.

In this case of air cylinders, it must be remembered that Q is the volume of the volume of

compressed air and this changes with pressure so any variation in pressure will cause a variation

in the velocity.

POWER

Mechanical power is defined as Force * velocity. This makes it easy to calculate the power of a cylinder.

The fluid power supplied is more than the mechanical power output because of friction between the

sliding parts.

CALCULATION

Diameter of the cylinder D=2R

Diameter of the connecting rod = d= 2r

Total stroke length of the cylinder = 80mm

Effective stroke length = 40 mm

F =Force exerted on work piece

F = P*A

F= (Pcomp – Patm) * π/4(D^2 –d^2)

Pressure Measurement

Considering P= 10 bar = 1.01 N/mm2=145.03 PSI

Diameter of piston = D= 25mm

Diameter of piston rod =d=10mm

A= (3.14 / 4) * (D2 –d2)

= (3.14 / 4) * (252-102)

= 412.33 mm2

And P= F / A

0.068 = F / 412.33

F = 28.42 N =2.84kg

So, we have selected pneumatic cylinder move 2.8 Kg. Of force at 10 psi pressure.

5.1 Table for the maximum clamping force at different pressure variation

S no. Pcomp

psi

Pcomp

N/mm2

A=D2-

d2)

mm2

F=P*A

N

1 10 0.068 412.33 28.03

1 Bar = 100Kpa = 100KNm2 = 14.5 PSI

2 15 0.103 412.33 42.46

3 20 0.137 412.33 56.48

4 25 0.172 412.33 70.92

5 30 0.206 412.33 84.93

The Sample required clamping force are :

Metal Removal Rate = d x Fr x Vc x 12 (in./ft.)

(Q) (cu.in./min.)

Where d = Depth of Cut (in.)

Fr = Feed Rate (in.)

Vc = Cutting Speed (sfm)

or Q = .060 in. x .010 in. x 1500 ft/min x 12 in./ft

= 10.8 cu. in./min

Horsepower required = metal removal rate x unit power

(Hp) (Q) (P)

or Hp = 10.8 (cu. in./min) x.3 (Hp/cu.in/min)

= 3.24 Hp

Resultant cutter force = Hp x 33000 / cutter speed (sfm)

(Fc) (ft-lbs/min/Hp)(Vc)

or Fc = (3.24 x 33000) / 1500 sfm

= 72 pounds

Clamping Force =

72lbs/.15

= 480 lbs=217.72 kg

DATA AVAILABLE FROM RESEARCH PAPER

Shailesh S Pachbhai1* and Laukik P Raut2 “DESIGN AND DEVELOPMENT OF

HYDRAULIC FIXTURE FOR MACHINING HYDRAULIC LIFT HOUSING” ISSN 2278 –

0149 © 2014 IJMERR

Calculations for Existing Fixture

Followings are the data available from the Company

1) Time Required

Total number of shifts = 3

There are 3 Shift of 8 hours each.

Total working time in a shift is 7 hr 30 min i.e

450 min (30 minutes utilized in lunch break).

Total number of finished part in each shift =

32

Processing time = machining time + loading/

unloading time + part travel time (from pallet

to fixture or vice versa)

Machining time = 11.36 min

Loading time = 1.20 min

Unloading time = 1 min

Part travel time = 10 sec

Therefore, Processing time = 14.06 min

2) Cost of Operation

Cost of finished product = Rs. 345/- part

Cost of finished product/shift = Rs. 11040/-

Cost of finished product /day = Rs. 33120/-

There are 26 days of working in one month

Therefore,

Annual production cost of finished product =

Rs. 10333440/-

3) Machine Utilization

A measure (usually expressed as a percentage)

of how intensively a resources is being

used to produce a good or service (J Cecil,

2008).

Capacity = 3*8*1*6

= 144 machine hours

Hours available - hours down

Machine Utilization = —————————————— x 100

Hours available

= 91.66%

Calculations for New Proposed Fixture

1) Time Required

Total processing time includes machining

time, clamp actuation/de-actuation time and

part travel time.

According to standard specification of cylinder,

clamping will actuate in 5 sec.

Therefore,

Processing time = machining time + clamp

acting time + part travel time

v machining time = 11.36 min

clamp acting time = 0.10 min

part travel time = 0.10 min

Total number of finished parts per shift = 39

2) Cost of Operation

Cost of finished product per day = Rs.40365/-

Annual cost of finished part = Rs.1,25,93880/-

Annual increase in production cost of finished

part = Rs.22,60,440/-

3) Machine Utilization

Hours available - hours down

Machine Utilization = —————————————— x 100

Hours available

Machine hours = 144

Hours down = 9.5

S no. Parameter Existing

Fixture

Proposed

Fixture

1 Finished

part/Shift

32 parts 39 Parts

2 Production Cost Rs1,03,334440/- Rs 1,25,93880/-

3 Machinine

Utilization

91.66% 93.40%

4 Prossessing tie 14.06 min 11.56 min

5.2 Table Comparative Analysis

CAD Model of pneumatic Vice:-

Isometric View

Top View

CONCLUSION

The unique and novel design of proposed project automates the otherwise tedious task of

manually operating the vice and fixture to set the object for manufacturing operations with the

help of pneumatic clamp.

In industries our proposed system has a very vital application. With abundant supply of

compressed air, this project could serve as a cost effective vice or fixture, which can help reduce

non-productive time by speeding up the setup time.

Since there is minimal use of hands to manually operate the fixture component or workpiece,

this could help in reducing the accidental cases of hand getting trapped or injured in vice or in

any other mechanical component as everything is available at just a flick of a switch. It will

also improve error-proofing and the quality of manufactured workpiece.

The project is meant to produce a low cost pneumatic fixture as a work holding devices for

machining operations like filing, grinding, drilling. Etc. We designed a pneumatic fixture

which costs less than that available in the market. We tested our project on holding the work

pieces. Our pneumatic fixture is useful to do machining operations operation and 10 kgf/cm2

max pressure withstanding. We can do simple operations which is very useful and helpful to

do small works at our college. With a few extensions to this project it could serve well in

industries where pneumatic vices or fixtures are required to setup difficult to hold workpiece.

FUTURE SCOPE

1. Two cylinders side by side placed in the arrangement leads to hold a greater size work piece

for grinding operations also for higher thickness metals.

2. Two adjustable cylinders placed in opposite side results in the holding of all sizes work

piece.

REFERENCES

1. Guohua Qin, Weihong, Zhang Min Wan “Analysis and Optimal Design of Fixture Clamping

Sequence ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND

ENGINEERING, 2006.

2. Michael Stampfer “Automated setup and fixture planning system for box-shaped Parts”

International Journal of Advance Manufacturing Technology 45:540–552 DOI

10.1007/s00170-009-1983-1, 2008.

3. Djordje Vukelic, Uros Zuperl & Janko Hodolic “Complex system for fixture selection,

modification, and design” Int J Adv Manuf Technol 45:731–748 DOI 10.1007/s00170-009-

2014-y, 2009

4. Weifang Chen ,Lijun Ni & Jianbin Xue “Deformation control through fixture layout design

and clamping force optimization” Int J Adv Manuf Technol 38:860–867 DOI 10.1007/s00170-

007-1153-2,2008

5. J. Cecil “A Clamping Design Approach for Automated Fixture Design” Int J Adv Manuf

Technol 18:784–789,2008

6. Nicholas Amaral · Joseph J. Rencis · Yiming (Kevin) Rong “Development of a finite element

analysis tool for fixture design integrity verification and optimization” Int J Adv Manuf

Technol 25: 409–419, 2005

7. Y. Wang, X. Chen. N, Gindy “Surface error decomposition for fixture development” Int J

Adv Manuf Technol DOI 10.1007/s00170-005-0270-z, 2007

8. Shrikant.V.Peshatwar, L.P Raut “Design and development of Fixture for eccentric shaft: A

Review” International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-

9622 Vol. 3, Issue 1, February 2013.

9. Shailesh S Pachbhai1* and Laukik P Raut2 “DESIGN AND DEVELOPMENT OF

HYDRAULIC FIXTURE FOR MACHINING HYDRAULIC LIFT HOUSING” ISSN 2278 –

0149 © 2014 IJMERR