DESIGN AND MANUFACTURE OF A PNUEMATICALLY CONTROLLED ARTIFICIAL HAND PROJECT REPORT Submitted by AMITH KUMAR (AM.EN.U4ME10008) SANDEEP V (AM.EN.U4ME10049) SREERAJ R NATH (AM.EN.U4ME10059) VARUN RAJAN THAYYIL (AM.EN.U$ME10064) In partial fulfillment of the award of the degree Of BACHELOR OF TECHNOLOGY In MECHANICAL ENGINEERING Under the guidance of Dr.Ganesh Udupa Department Of Mechanical Engineering Amrita School Of Engineering Amritapuri, Clappana P OKollam 690 525,Kerala May 2014
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DESIGN AND MANUFACTURE OF A PNUEMATICALLY CONTROLLED ARTIFICIAL HAND
PROJECT REPORT
Submitted by
AMITH KUMAR (AM.EN.U4ME10008) SANDEEP V (AM.EN.U4ME10049) SREERAJ R NATH (AM.EN.U4ME10059) VARUN RAJAN THAYYIL (AM.EN.U$ME10064)
In partial fulfillment of the award of the degree
Of
BACHELOR OF TECHNOLOGY
In
MECHANICAL ENGINEERING
Under the guidance of
Dr.Ganesh Udupa
Department Of Mechanical Engineering Amrita School Of Engineering
Amritapuri, Clappana P OKollam 690 525,Kerala
May 2014
DEPARTMENT OF MECHANICAL ENGINEERING AMRITA SCHOOL OF ENGINEERING AMRITAPURI CAMPUS
CLAPPANA P.O, KOLLAM-690525, KERALA
PROJECT WORK CERTIFICATE
This is to certify that
AMITH KUMAR AM.EN.U4ME10008 SANDEEP VENU AM.EN.U4ME10049 SREERAJ R NATH AM.EN.U4ME10059 VARUN RAJAN THAYYIL AM.EN.U4ME10064
Have completed satisfactorily the project work entitled ‘DESIGN AND ANALYSIS OF A PNUEMATICALLY CONTROLLED ARTIFICIAL HAND’ during the year 2013-2014 in partial fulfillment to the requirements for the award of the degree of BACHELOR OF TECHNOLOGY in MECHANICAL ENGINEERING by AMRITA VISHWA VIDYAPEETHAM
___________________ ___________________ Dr.Ganesh Udupa Mr.Pramod Sreedharan Dept. Mechanical Engineering Assistant-Professor D Dept. of MechanicalEngineering
____________________ ______________________ Dr.K Sankaran Dr.Balakrishna Shankar Principal Chairperson Amrita School of Engineering Dept. of Mechanical Engineering Amritapuri Date:
ACKNOWLEDGEMENT
Our humble pranams at the lotus feet of Her Holiness MATA AMRITANANDAMAYI
DEVI, our beloved AMMAfor providing us this opportunityand for her blessings throughout
the project without which this project would not have been possible
We would like to express our deep sense of gratitude to Dr. GaneshUdupa, Department of
Mechanical Engineering, Amrita School of Engineering for his invaluable guidance, constant
support throughout the course of this project
We would like to express our sincere gratitude to Mr. PramodSreedharan, assistant
professor Department of Mechanical Engineering, Amrita School of Engineering, for his
invaluable guidance, constant encouragement and support throughout the course of this
project.
We are also grateful to Mr.SreepathyBhatt, Elgi Ultra Industries Limited and
Dr.AjithRamesh, Department of Mechanical Engineering, Amrita School of Engineering,
Ettimadai for their sustained suggestions throughout the course of this project work.
We would also like to express our sincere gratitude to Dr.BalakrishnaSankar, Associate
dean Amrita school of Engineering for his valuable support which helped in carrying this
work towards its destination.
We also express our gratitude to Br.Sudeep, Director, Amrita Vishwa Vidyapeetham,
AmritapuriCampus, Dr .KSankaran, Principal, Amrita School of Engineering, Amritapuri
campus for giving us this opportunity to carry out this project work.
Also we would also like to thank our entire Mechanical Engineering department faculty
members and our colleagues without whom this project would not have been possible
\
ABSTRACT
The purpose of our project is design a low cost pneumatically controlled artificial hand to
replicate the functionalities of the human hand. In the area of Bio-Robotics the artificial
human hand plays a very important role as it is required to hold and place the object at the
desired location. The requirements of the hand in terms of load capacity, and flexibility to
adapt to the form of the object with tactile sensing capability which suit the strength of the
object are necessary .Extensive research work is under way in the designing of artificial
human hand. An exhaustive survey of all such hands convey the idea of higher and higher
sophistication with innumerable components and elaborate controls with programmable
ability has been the outcome of the research. Design and fabrication of a multi-fingered
artificial hand is based on single chamber asymmetric flexible pneumatic actuator (AFPA)
compared to three chamber actuators by earlier researchers. Based on AFPA, two types of
joints such as bending and side sway joints are been developed. Experiments are carried out to
investigate the bending characteristics of asymmetric flexible bellow and side sway joints.
Experimental results demonstrate that bending and side sway joints based on AFPA can meet
the designed requirement of application.
1. INTRODUCTION
This project is aimed at designing a 10 degree of freedom pneumatically powered arm for
prosthetic applications. In today’s world the degree of accidents and hazards areincreasing at
an alarming rate. Amputations are nowadays becoming a very dangerous factor in the
environment .The growing technology and importance of artificial prosthetics have sparked
an interest in many manufacturers these days making it a subject of great interest in the
robotic field.
Today three types of prosthetic hands are available. Static prosthetic, Electrode or sensor
prosthetics and myoelectric prosthetic hands. The numerousvarieties available in the market
have given people a lot of options to choose from .There are prosthetic arms which can simply
be used as a hook to other types of hands which behaves as a complete human hand that even
has a sense of touch and even detect the sensation of hot and cold. As time passes by new
developments are being made in the field of prosthetics and we can be sure it won’t be long
before the development of an artificial hand that behaves exactly like that of a human hand.
1.1 AIM
To design and fabricate a compact, lightweight and low cost artificial pneumatic prosthetic
hand capable of producing human like behaviour.
1.2 SCOPE OF THE PROJECT
1. To redesign and correct the current available bellow and mould design
2. To simulate and confirm the finger design in a simulation software
3. To design an electrical circuit and to programme different grasps into the pneumatic
prosthetic hand
4. To manufacture the bellows and assemble them to form a five fingered hand
5. Experimenting the performance of the manufactured hand and comparing results with the
previous designs and current market models.
2. LITRATURE SURVEY
2.1 FLEXIBLE MICRO ACTUATOR ARMFlexible micro actuators (FMA)is made of silicone rubber reinforced with nylon fiber in the
circumferential direction. The fiber gives the rubberan anisotropic elasticity, the rubber is
easily deformed in the axial direction but resists deformation in the radial direction. For this
reason, when the pressureis increased in one chamber, the FMA bendsin the direction
opposite to the pressurized chamber. It can be bend in any direction by appropriate
pressurecontrol in each chamber, and can be stretched in the axial direction when the pressure
is increased inall three chambers. It is assumed that FMA deformation is smalland that it takes
the form of an arc.
d Autonomous Systems 18 (1996) 135-140
Figure (Suzumori/Robotics and Autonomous Systems 18 (1996) 135-140)
2.1.1APPLICATIONS
ROBOT HAND
By connecting FMAs serially, an arm is obtainedwith many degrees of freedom and snake-
like movements .Fig3.2shows a prototype made of two FMAsand a mini-gripper, which is
also made of fiber reinforced rubber.It has seven degrees of freedom including the gripper
motion. Pneumatic tubes connected to the upper FMA and the gripper pass through the
chambers in the lower FMA.The arm movement is detected optically using an LED attached
to the tip of the arm and a position sensing device.
Measured data regarding the LED positions are fed to a computer, and a closed loop with
proportional control is constructed. It indicates that the FMA arm compliance can be
controlled by adjusting feedback gain Kf. In this experiment, reference inputs were kept
constant. The sampling period for the control system was 50 ms.It indicated that compliance
control could be achieved also with robots made of soft materials. While the compliance
control of a conventional robot made of rigid links is used to increase compliance, the
compliance control of a rob made of soft materials is used to increase stiffness.
Fig.2.2 ROBOT ARM(Suzumori/Robotics and Autonomous Systems 18(1996) 135-
140)
2.2PNEUMATIC TENDON DRIVEN HAND
2.2.1Construction and mechanism
The appearance and mechanisms of the balloon actuators are portrayed in figure3.3.The
balloon actuator has an air pressure-drive-type actuator comprising a silicone oval tube and
tendon. The silicone rubber tube is sealed at one end to produce a balloon. Compressed air is
supplied through an opening at the other end to expand the balloon. The tube ist hen fixed at
both ends by acrylic plates. The wall is arranged on one side of the balloon to restrain its
expansion. To decrease the loss of the output efficiency, a roller is arranged in the part where
the tendon direction is changed. A The tendon wrapped around the balloon is expanded when
the balloon expands, which creates tensile force for the tendon drive.
Fig2.3 Tendon driven ballon actuator (Design of a variable-stiffness robotic hand
This device consists mainly of silicone rubber, fiber reinforcement, and a jointed part. The
fiber reinforcement is inserted in the silicone rubber in a mesh-like pattern like the
McKibben-type artificial muscle actuator.
FABRICATION OF VARIABLE STIFNESS DEVICEThe variable-stiffness device is fabricated by pouring room temperature vulcanized (RTV) silicone rubber into molds. Molds have a convex shape part for making grooves in the rubber surface to arrange fibers with an angle of 54.7 .The cylindrical core is put between two molds. Then RTV silicone rubber in a liquid state is poured into them. After heating at 80 ◦C for 20 min, it reaches an elastic state. Then, it is reinforced with 16 fibers. The 104 μm diameter Kevlar fiber material has high tensile strength. The reinforced tube part with the cylindrical core is put into other molds that have no convex shape; silicone rubber is poured in again to cover them thinly. Using this manufacturing method, fibers are not exposed on the device surface. The rubber thickness is 1.5 mm, with an outer diameter of 20 mm.
2.2.3 ROBOT HAND WITH VARIABLE STIFNESS FINGER
CONSTRUCTION AND DRIVING MECHANISMS
The robot hand fingers are four in all, with three joints per finger, making 12 in all. Degrees of freedom of the joints are two per finger, making eight in all. The robot hand size is almost identical to that of a human hand. Eight balloon actuators are installed in the palm of the robot hand. Six balloon actuators are for fingers, and twoballoon actuators are for a thumb. An actuator is used for each MP joint per finger, and another actuator is also used for the PIP joint and DIP joint per finger. These fingers can be controlled individually. The robot hand generates grasping force by restoring the force of the elastic element and decreasing it by the tensile force of the balloon actuator. Grasping, pitching, and platform are possible using this proposed robot hand. The robot hand frame is made of ABS resin. Its total weight is 0.27 kg, which is lighter than a human hand.
TABLE 2.1 Specifications of robot hand(Design of a variable-stiffness robotic hand
FRICTION CHARACTERISTICSThe proposed robot hand can grasp objects flexibly, similarly to a human hand when the input air pressure is 10 MPa. It is sure to perform dexterous manipulation and slip motion easily by the decreasing coefficient of friction when the input air pressure is high. In an earlier study, Sugano developed a finger with finger tip curvature that differs at each point. This finger’s frictional force is adjusted by changing the contact area when changing the contact point. Murakami developed a finger for which the rubber is arranged on the surface. Its frictional force can be changed by changing the contact area when changing the contact force. This finger
can be adjusted to the coefficient of static friction; it has achieved turning of pages. To change the frictional force, the user must adjust the fingertip posture and must later adjust the contact force to objects. Therefore, these fingers are changed passively according to the frictional force. For this proposed finger, the frictional force is changed actively. By changing the finger surface stiffness, the frictional force can be adjusted by changing the contact area, and does not require adjustment of the finger posture and contact force. Therefore, for instance, when the finger rubs the human body, it might be moved smoothly on the body without giving unpleasantness to the human by keeping the contact force and finger posture.2.3FLUID POWERED HAND
2.3.1 SYSTEM SPECIFICATIONS AND DESIGN
It consists of following general components:i. One hydraulic pump, one fluid reservoir, five electric valves, and an
electronic unit, which are integrated in the metacarpus of the new adaptive hand.
ii. Eight flexible fluidic actuators of compact design, which are integrated in the finger joints.
iii. One battery for power supply and two myoelectric electrodes which are placed in the socket.
TABLE 2.2(Development of a miniaturised hydraulic actuation system for artificial hands A. Kargov∗, T. Werner, C. Pylatiuk, S. Schulz
According to the design concept of the electro-hydraulic system, the artificial hand does not need any other external components for functioning, except for a rechargeable lithium battery and myo-electrodes that are housed within the socket tocontact the user’s skin. The joints of this prosthesis are actuated by flexible fluidic actuators which are connected to the micro valves. Some actuators are coupled, like the base joints of fingers IV–V and both joints of fingers II and III accord-ingly. Actuators of the thumb can be controlled independently of each other. Consequently, the prosthetic hand prototype may accomplish up to five grasping patterns: power grasp, precision grasp, tripod grasp, hook grasp, and stretching of an index finger.The grasping patterns are pre-assigned in the control unit of the hand and accomplished as follows. Firstly, the electronic unit receives the control signals from the user. The control system of the prosthetic hand collects control signals from the upper limp muscles via myo-electrodes . The control unit is responsible for the analysis of control signals, selection of preprogrammed grasping patterns, and operation of the hydraulic pump and valves. Afterwards, the hydraulic pump generates the fluid pressure in the actuators, and electric valves control the action of the actuator. Depending on the grip type selected, the corresponding actuators will be filled and the joint will move. The pump and valves will be controlled by the hand electronics as well. The electronic unit consists of a custom-made, multilayer, small-sized circuit board that fits into the meta carpus of the hand. It includes a programmable microcontroller (typePIC16F877 by Microchip Technology Inc., USA), drivers for the valves and the pump, an analogue–digital converter, and a serial RS232 and Bluetooth interfaces to change settings of the controller.
ROBOTIC HANDS
Many varieties of robotic hands are present in today’s market. Each of them having their own
unique characteristics and functions. Technologies and innovations have helped various
multinational companies to invest in this field of robotics and manufacture some of the most
state of the art prosthetic arms that is available now. Various varieties in terms of the material
used in the arm, powering source i.e.(electrical, pneumatic, fluidic)etc. are also available.
Some of the most sought after and successful prosthetic hand models manufactured by some
of the leading prosthetic hand manufacturing companies are discussed below
2.4.1 BEBIONIC MYOELECTRIC HAND
Bebionic utilizes leading-edge technology and unique, ergonomic features that make it unlike
any other hand available. These innovations combine to give the hand unrivalled versatility,
functionality and performance. Bebionic hands are an example of a myoelectric prosthetic
hand manufactured by RSLSTEEPER industries. Programmed to meet almost each and every
need of a amputed normal human being . Bebionic is said to have all that is necessary to stand
shoulder to shoulder to a natural human hand.
A single bebionic hand have individual motors in each fingers that will enable a person to
move and grip this hand as exactly that of a human hand. In order to make it more compact
the motors are positioned to optimize weight distribution. It also consists of a powerful
microprocessor which gives us unwavering control of the hand all the time.
It contains 14 different grasps including all the basic grips that are required for day to day
function of a human being. While an object is grasped bebionic hands automatically sensor
the surface of the object and automatically adjust the grips so that slipping from the fingers do
not occour. Its programmed to perform heavy duties like lifting supporting etc. It is said that a
person may take the support of this myoelectric hand to lift himself up from a seated position.
This shows that this hand is manufactured and designed in way that it may withstand even
weight of a human being. The hand can also be configured and customized wirelessly to
individual user requirements via smart electronics and easy-to-use software package,
bebalance. The innovative palm design of this myoelectric hand protects it from impact
damage. Unlike many hands this myoelectric hand is programmed in a way so that it may
even grasp softer objects like paper cup and eggs without crushing them or deforming them.
2.4.2 DRAPA’S BRAIN CONTROLLED PROSTHETIC ARM
This hand has been produced and developed by the US Department of Defence. It aims at
providing help to amputed people in the field of Military defence. It particularly stands out
from the rest of the hands in the market as this prosthetic hand can be directly controlled by
the human brain. The nerves in human hand which still remains after amputation is surgically
attached to the different muscles in the prosthetic arm. Targeted muscle innervation (TMR)
developed by the Rehabilitation of Chicago allows manipulation of the prosthetic with
thoughts alone.
The DRAPA programme associated with this hand design is named as Hand Proprioception
and Touch Interface or simply HAPTIX.
HAPTIX aims to achieve its goals by developing interface systems that measure and decode
motor signals recorded in peripheral nerves and/or muscles. The programme will adapt one of
the advanced prosthetic limb system developed under revolutionizing Prosthetic to
incorporate sensors that provide tactile and proprioceptive feedback to the users, delivery
through patterned stimulation of sensory pathway in the peripheral nerve. One of the key
challenge in this programme is to identify stimulation patterning strategies that elicit
naturalistic sensation of touch and movement. The Ultimate goal is to create fully implanted
device that is safe reliable effective and approved for human use.
In addition to the improved motor performance that restored touch and proprioception would
convey to the user, mounting evidence suggests that sensory stimulation in amputees may
provide important psychological benefits such as improving prosthesis “embodiment” and
reducing the phantom limb pain that is suffered by approximately 80 percent of amputees. For
this reason, DARPA seeks the inclusion of psychologists in the multi-disciplinary teams of
scientists, engineers, and clinicians proposing to develop the electrodes, algorithms, and
electronics technology components for the HAPTIX system. Teams will need to consider how
the use of HAPTIX system may impact the user in several important domains including motor
and sensory function, psychology, pain, and quality of life.
2.4.3 MICHELANGELO HAND
Another hand present in the market is the Michelangelo hand designed by the Ottobock
industries. The main and the most important component of the Michelangelo hand is the
futuristic Axon-Bus system. Combined with the Michelangelo hand the Axon-Bus system
offers more degrees of freedom than ever before .A new technology derived from the aviation
and aerospace industry ensures a smooth and especially fast data transfer between individual
components.
In many prosthetic hands the type of movement like turning papers or sorting out money from
a purse is comparatively difficult to produce and programmed but in the Michelangelo hand in
a variety of different grasps there is an individual grasp which performs this function it is
relatively called as the WIN.
The main reason for the success of this hand is mainly due to the Axon-Bus system and all the
variable components adapted to meet its individual needs. A component in this collection is
the Axon Wrist. The flexible Axon wrist joint is an important part of the Axon-Bus system .It
consist of two interconnected modules which in flexible mode imitate the natural movement
of the human wrist joint. At the same time the variable movement pattern minimizes unnatural
compensating movements and thus promotes a healthy posture in the user. The Flexion
present along with the Axon wrist helps in flexibility of the hand .Also near the wrist there is
an extension part provided. So when in flexible mode the Axon Wrist allows the user to
extend the hand to the back according to the natural model (extension) and it can also be
locked in that position
2.4.4 I LIMB
I limb prosthetic hands are manufactured by Touch bionics industries. This hand gives more
importance to its appearance and movement like that of a normal human hand. Each finger
bends at the natural joints so that it can accurately adapt to fit around the shape of the object.
I limb prosthetics are powered by biosim software. They use biosim to select the grip patterns
and hand features that they want to use, including the option to create your own custom
gestures. Built-in training modes are included to help achieve better results with the prosthesis
I limb ultra is the only prosthetic arm which can gradually increase the strength of its grip on
an object. This hand also has the auto grasp feature which prevents the object from slipping
off the fingers. The wrist rotation in this hand can either me rotated manually or by an
electronic wrist rotator. Made for high durability. The whole chassis is made up of aluminium
COMPANY/
MODELNAME
COST AREA OF
DISTRIBUTION
WEIGHT SIZE
Be bionic/Myoelectric Prosthetic hands
$11,000 Mainly supplied in open markets of north and south America
570g-610g 190 mm-200mm
DRAPA/Brain controlled prosthetic arm
$50,000-$7000 Mainly supplied for military service assistance and also for us open markets
430g-510g 170mm-190mm
Ottobok healthcare/Michelangelo hand
$73,000 Main distribution in German markets and also in medical facilities
>420g 180mm-182mm
THEORY AND PRINCIPLE
ECCENTRICITY
The suggested bellow is an elastic tube with one half thicker than the other, giving it a plane-
symmetrical cross section instead of an axis-symmetrical cut section .Since the cut-section is
not axis-symmetrical, its centroid is slightly removed from the center of pressure (COP) by a
small distance 'e' fig and it is termed has eccentricity of the bellow .This results in a
bending moment M= PxAin xe. The equation of eccentricity for the given bellow is derived
Fig :Abaqus simulation of taper bellow at 5 bar pressure
This taper model gives a bending angle of 810 for a pressure of 5 bar. The stress concentration
factor is also considered in the design. The material does not deform to cause stress that could
be harmful for the functioning of the bellow.
Due to the taper towards the end of the bellow, the core pin can be easily removed from the
bellow. Hence, the taper model can be manufactured in a single piece mould.
The assurance that the bellow manufactured as a single piece will not have leakage problems
after repeated usage, and the noticeable increase in the bending angle makes it an apt choice
for the finger design.
3.2 FINGER DESIGN
The bellow is the pneumatic actuator in the finger. Due to the length limitations we have
included 2 bending joints in each finger. Each bellow is provided with a separate polyurethane
tube that provides the pressurised air. Many attempts were done to include the pneumatic
tubes inside the finger design.
Fig : Addition of tubes within the finger bending joint
But any addition to the bending joint caused the bending angle to reduce. Hence, the tube was
allowed to freely pass the first bellow and join the second bellow.
The final finger design consists of 4 parts.
Fig : Four pieces join together to form finger
The four pieces are attached together using strong adhesive called Clubber. The finger has a
150 bend at the tip and at the connection between the two bending joints.
Fig :Abaqus simulation bending of the full finger (a) outside view (b) cross sectional view
The combined bending of both bending joints and the fixed bending angles of the connector
and the tip gives the finger a bending angle of about 1940 at 5 bar pressure. Pressure is applied
separately to each bellow using pneumatic polyurethane tubes if 4mm O.D.
3.3 PALM DESIGN
The palm has been designed to accommodate each finger. The fingers can be fixed into the
palm individually. Provision has been made for the pneumatic tubes to pass through the palm
without being seen outside. It has been made of foam that is weightless and soft, thus giving it
a soft human like feel. The palm enhances the grip of the hand by supporting any object the
fingers grasp.
Fig : Palm design
3.5 Full hand assembly
The full hand assembly design is such that each finger can be attached to the palm separately.
Hence, any damaged pieces can be replaced individually. The palm design assures the
placement of the fingers in a fashion most similar to the human hand. An extension to the
hand is made using cardboard. This extension acts as an arm and it also holds the solenoid
valves, control systems and pressure regulator. Buttons placed on this arm can be used to
activate different grasp patterns in the hand.
Fig : Full hand assembly design
MANUFACTURING OF BELLOWS
MANUFACTURE OF MOULD FOR BELLOWS
The design of bellows is done in solid works. Now to manufacture this bellow a mould is also
designed in solid works. The manufacturing of bellow involves high temperatures and
pressure. So the mould need to withstand high temperature and pressure for some duration.
Keeping all these in mind a mould of steel is made. A proper design is made in solid works
with cope, drag and core.
The technique used for manufacturing this mould is Electric Discharge Machining (EDM). It
is also called spark machining, spark eroding, burning, die sinking or wire erosion. In this
technique a desired shape is obtained by using electrical discharges between two electrodes,
separated by a dielectric liquid and subject to an electric voltage. One of the electrodes is
called the tool-electrode, or simply the ‘tool’ or ‘electrode’, while the other is called the
workpiece-electrode, or ‘workpiece’. When the distance between the two electrodes is
reduced, the intensity of the electric field in the volume between the electrodes becomes
greater than the strength of the dielectric, which breaks, allowing current to flow between the
two electrodes. This phenomenon is the same as the breakdown of a capacitor. As a result,
material is removed from both the electrodes.
Once the current flow stops, new liquid dielectric is usually conveyed into the inter-electrode
volume enabling the solid particles to be carried away and the insulating properties of the
dielectric to be restored. Adding new liquid dielectric in the inter-electrode volume is
commonly referred to as flushing. Also, after a current flow, a difference of potential between
the two electrodes is restored to what it was before the breakdown, so that a new liquid
dielectric breakdown can occur.
The electrode and workpiece are connected in an electrical circuit. When the electrode (tool) is brought closer to workpiece spark is created between them and material melts and evaporates or eroded
COREPIN
COPE AND DRAG
DRAWING
MANUFACTURING OF NITRILE RUBBER BELLOWS
The bellows is made from nitrile rubber, to further strengthen it reinforcement with carbon
black was done. Carbon black is widely used for reinforcement of rubbers. Reinforcement is
directly proportional to surface area. It means that smaller the size of carbon black used
greater the reinforcing effect. It also depends on increasing levels of carbon black (parts per
hundred rubber). Reinforcement gives increased tensile, hardness, abrasion resistance and
modulus and tear strength.
Producing a rubber having optimum curing time with necessary physical properties, a proper
mixing mechanism is needed. The Banbury internal mixer is commonly used to mix the
compound ingredients. The rubber along with carbon black powder is introduced into its two
spiral shaped rotors within a closed chamber. A dual step procedure is followed to ensure that
premature vulcanisation does not occur.
6.2.1 BANBURY INTERNAL MIXER Internal batch mixers such as the Banbury mixer are used for mixing or compounding rubber and
plastics in which heat and pressure are applied simultaneously. The Banbury mixer resembles a
robust dough mixer in that two interrupted spiral rotors move in opposite directions at 30 to 40
rotations per minute. These intersect so as to leave a ridge between the blades. The shearing
action is intense, and the power input can be as high as 1,200 kilowatts for a 250-kg (550-
pound).
The Banbury mixer is a brand of internal batch mixer. The blades may be cored for circulation of heating or cooling. Its invention resulted in major labour and capital savings in the tire industry, doing away with the initial step of roller-milling rubber. It is also used for reinforcing fillers in a resin system. 6.2.2 PROCEDURE FOR MAKING RUBBER BELLOW Once the nitrile rubber sheets are prepared, they are cut into pieces and placed in the mould
along with the core. Then the mould is placed into a hydraulic vertical press assisted by heating
coils to attain desired temperature. The mould is put under a pressure of 120 bar and
temperature of 150 ⁰ C for 12 minutes. Proper removal of cope and drag and core gives the
desired bellow. The procedure is explained neatly along with pictures in next page.
MANUFACTURING OF HAND AND PALM
PNEUMATICS
The extreme costs of Servo motor-controlled hands in the market, lead us to find a better
actuating media-air. Thus we try to develop a pneumatically controlled hand, so as to reduce
cost.
Pneumatics has a large role to play in Mechanical Engineering, Design and Automation of
systems.
To be able to control machines and system requires the development of a complex logical
interconnection of status and switching conditions. This occurs by the interaction of sensors,
processors or pneumatic systems. The technological progress made, has improved the quality,
diversity of pneumatic components and thereby contributed to its use in automation.
ADVANTAGES OF PNEUMATICS
i. Air is the medium
ii. Availability- Air is available practically everywhere in unlimited quantity
iii. Transport- Air can be easily transported in pipelines, even over large distances
iv. Storage- Compressed air can be stored in a reservoir and removed as required. In
addition, reservoir can be transportable.
v. Temperature- Compressed air is practically insensitive to temperature fluctuations.
This ensures stable and reliable operation, even under extreme conditions.
vi. Explosion proof- Compressed air offers offer no risk of explosion or Fire.
vii. Cleanliness- Unlubricated exhaust air is clean. Any unlubricated air which escapes
through leaking pipes or components does not cause contamination
viii. Components- The operating components are of simple construction hence,
inexpensive.
ix. Speed- Compressed air is a very fast working medium. Enables high working speeds
to be attained.
x. Overload safe- Pneumatic tools and operating components can be loaded to the point
of stopping and are therefore overload safe
COMPONENTS
AIR COMPRESSOR
The compressed air supply for pneumatic system should be adequately calculated and made
available in appropriate quantity. Air is compressed by a compressor and delivered to an air-
distribution system.
As a rule pneumatic components are designed for a maximum operating pressure of 8-10bar
but in practice, it is recommended to use 5-6 bar.
Fig : Air compressor
PRESSURE REGULATING VALVE
A Pressure regulating valve is put right after the storage tank or the compressor. It is used for
controlling the air pressure entering the system. It can be used for setting a particular pressure
limit beyond which pressure, the value will not rise. The compressor is kept open and the
knobof the device is adjusted till the optimum value we want is reached. We set a pressure of
5 bar in the device for our purpose. Our pressure regulator has a maximum limit of 10bar
pressure.
Fig : Pressure regulator
SOLENOID VALVE
Solenoid valves are used to actuate each finger independently. Different grasps are possible to
the pneumatic hand by the usage of solenoid valve. We use the solenoid valve from SMC with
the series name SYJ314-5LZ. It operates at 24v DC and It works on normally closed
position.
The length of the lead wire is 100mm.
Fig : Solenoid valves
CONNECTORS
A connector is used to connect pipes of different diameters. For example in our circuit, the
input from the compressor is from a 6mm dia tube and the input to the pressure regulator is
4mm tube, So we use a connector to connect both the tubes. Hence a connector is absolutely
necessary in this circuit. A Connector is usually used in almost all pneumatic circuits and is
easily available in the market. The connectors which we use are listed below
i. 6mm to 4mm reducer
ii. 4mm Y connectors
Fig : 6-4 Reducer Fig : 4mm Y connector
POLYURETHANE TUBEWe use SMC polyurethane tubes of outer diameter 4mm and 6mm for our pneumatic circuit.
PNEUMATIC BLOCK DIAGRAM
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COMPRESSOR
PRESSURE REGULATOR
SOLENOID VALVE(normally closed 5 output)
4mm Y connector
4mm Y connector
4mm Y connector
4mm Y connector
4mm Y connector
Finger Finger FingerFinger Finger
CONTROL SYSTEM
COMPONENTS
FUSE
A fuse is an electronic equipment which gets shorted out or turns off the circuit when a
current of more than the maximum value flows through the circuit. Fuse which operates once
and then must be replaced.
FUSEFUSE HOLDER SMALL GOOD SS54
The combination of the fuse base with its fuse carrier.
DID IN 40007 G.ARK
A flyback diode (sometimes called a snubber diode, freewheeling diode, suppressor
diode, suppression diode,clamp diode or catch diode]) is a diode used to eliminate flyback,
which is the sudden voltage spike seen across an inductive load when its supply voltage is
suddenly reduced or removed.
IC LM 317The LM317 is a popular adjustable linear voltage regulator.The LM337, a negative
complement to the LM317, regulates voltages below, rather than above, the reference As
linear regulators, the LM317 and LM337 are used in DC to DC converter applications.