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

usingpneumatic soft rubber actuators Jun-ya Nagase1, ShuichiWakimoto2, Toshiyuki Satoh3,Norihiko Saga1 and Koichi Suzumori4)

2.2.2PNEUMATIC VARIABLE STIFNESS FINGER

VARIABLE STIFNESS DEVICE

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

usingpneumatic soft rubber actuators Jun-ya Nagase1, ShuichiWakimoto2, Toshiyuki Satoh3,Norihiko Saga1 and Koichi Suzumori4)

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

as follows

Eccentricty = Centreof pressure - centroid-------------(1)

Type of hand Finger Material used

Mechanism weight Degree of freedom

Pneumatic tendon driven balloon hand

Silicon rubber One end of tube is sealed and pressure is passed through the other end which makes it expand

Pneumatic variable stiffness finger hand

Vulcanized silicon rubber(RTV)

Generates force by restoring the force of the elastic element and decreasing it tensile force ofthe actuator

0.27 kg 12

Fluidic powered hand

Reinforced soft flexible actuators which forms a closed elastic chamber

Actuators will be filled with fluids which inflates and deflates the actuators

0.300 kg

Electro hydraulic hand

Any flexible thin film hydraulic actuators

An electronic unit is present which receives control signals. A control unit analyses these signals and operates the pump and valves

0.350 kg

Centre of pressure (COP) = 4 (r+ t )

3 π+b-----------(2)

To find the centroid of the end section of the bellow,let the cordinates of the centroid be

(X,Y)then X=0(since the coordinate axis pass through the centroid of each section) Let us

assume that area of the semicircular section be A1 and r be the radius of the semicircle, t be

the top thickness and b be the base thickness of the bellow

Area of the semicircle A1 =π4

(r+t )2and centroid Y1 = 4 (r+t)

3 π+b---------------(3)

Let area of the base rectangle be A2=l x b and centroid Y2= b2 ----------------(4)

Substituting equation (3) and(4)

The centroid of the whole section can be found by the formula Y= Y 1 A 1+Y 2 A 2

A 1+A 2

Y=[ 4 (r+t )3 π

+b] x π x (r+t )2+l b2

2 lb+π (r+t)2 ---------------------(5)

Substituting (5)and(2) in (1)

Eccentricity= 4 (r+ t )+b

3π -[ [ 4 (r+t )

3 π+b ]x π x (r+ t)2+ lb2

2 lb+π (r+ t)2 ]

BENDING EQUATION

Euler–Bernoulli beam model is suggested for modeling the bellow's bending under quasi-

static loading. The following assumptions were used for the bending model:

i. The cross-section does not change along the actuator.

ii. The weight of the bellow is neglected

iii. The Young modulus of the material, E, remains constant during actuation.

iv. Change in length of bellow is neglected

For the bellow M= PxAxe ------------------------ (1)

where,

P -pressure applied inside the bellow

A- Inlet area of the bellow where pressure acts,

e -Eccentricity of the bellow

Moment equation can also be written as M= F X L-------------(2)

F -Normal force exerted by the bellow

L- Length of bellow

equating equations (1) and(2) F=PAeL ------------(3)

L2=R2+R2−2 RxRxcos∅ ( cosine law for a triangle )

where R is the radius of curvature of bending

L=R√2¿¿----------------------------(4)

R=S

sin∅ -----------------------------(5)

S- the distance of specified point measured from the fixed end

Substituting equation (5) in(4)

L =S

sin∅ √2¿¿

M=FxS

sin∅ √2¿¿

Substituting for F from (3)

M=PAeL x S

sin∅ √2¿¿---------------------------(6)

According to the bending equation

puttingdydx = tan∅ ,we get EI cos∅ d∅

dS=M--------------(7)

Substituting value for moment from (6) EI cos∅ d∅dS

=¿ PAeL

Ssin∅ √2¿¿¿

by rearranging the terms equation becomes

sin∅ cos∅ d∅√2¿¿¿

=PAe S dsEIL

integrating both sides

∫ sin∅ cos∅ d∅√2¿¿¿

¿ =∫ PAe S dsEIL

Taking LHS integeration

∫ sin∅ cos∅ d∅√2¿¿¿

¿ =∫cos∅ cos ∅2

d∅

Applying trignometric releations∫cos∅ cos ∅2

d∅ transforms into

¿ sin ∅2

+sin( 3∅

2 )3

2sin ∅2 [1+2(cos ∅

2 )2]

3

=2sin ∅

23

⌈ 2+cos∅ ⌉

by trial and error method the term sin ∅2

cos∅ is neglected and the LHS becomes 4sin ∅

23

Integerating RHS we get PAeS C

2EI ,where c is a constant for integeration and the value for c is

6.67.

Equating LHS and RHS the equation for bending angle becomes

∅=2sin−1 3 PAeLc8 EI -----------------------(8)

From equation (8) it is inferred that bending angle is a function of applied pressure,area at

which pressure acts, eccentricity of the body, youngs modulus of the material, length of the

bellow and moment of inertia of the bellow.

WEIGHT CARRYING CAPACITY OF FINGER

Consider a body being hold by pneumatic hand .During holding of an object the bellow exert

a normal reaction towards the object and only due to the friction between the body and the

bellow the finger made of bellow is able to hold the object. The maximum weight that N

number of fingers can carry is derived below

W=µ(nR), where,

W - weight of the body carried by the fingers

µ - Coefficient of friction for nitrile rubber= .20 at 5 bar

n -Number of fingers

R - Normal reaction offered by bellow to the surface

The normal reaction is given by R= PAe

L

P -pressure inside the bellow

A-Cross sectional area of pressure acting surface

e - eccentricity of the bellow

L - length of bellow

Therefore the maximum weight a finger can carry, W=nPAe µ

L

FORWARD KINEMATICS

Forward kinematics refers to the use of the transformation matrix to compute the position of

the end-effector from specified values for the joint parameters. The kinematics equations of

the robot are used in robotics, computer games, and animation. The reverse process that

computes the joint parameters that achieve a specified position of the end-effector is known as

inverse kinematics.

The transformation matrix and transformation coordinate system for our finger is given

below

i-1Ti = cosØ -sinØ 0 ai-1

sinØ cosα cosØcosα -sinα -sinαdi

sinØsinαcosØ sinα cosα cosαdi

0 0 0 1

Tabulation for the forward kinematics analysis is given below

LINK α ai-1 di Ø

1 0 0 0 Ø1

2 0 27.5 0 0

3 0 12.5 0 15+Ø3

4 0 27.5 0 15

5 0 19.5 0 0

The transformation matrix for each link is given below0T1 = CosØ1 -SinØ1 0 0

sinØ cosØ1 0 0 --------------------(1)

0 0 1 0

0 0 0 1

1T2 = 1 0 0 27.5

0 1 0 0 ----------------------(2)

0 0 1 0

0 0 0 1

2T3 Cos(15+ø3) -Sin(15+ø3) 0 12.5

Sin(15+ø3) Cos(15+ø3) 0 0---------------------(3)

0 0 1 0

0 0 0 1

3T4 =.965 -.258 0 27.5

.258 .965 0 0 ---------------------(4)

0 0 1 0

0 0 0 1

5T4= 1 0 0 19.5

0 1 0 0

0 0 1 0 ------------------------(5)

0 0 0 1

Multiplying equations 1,2,3,4,5 gives the transformation matrix as

0T5 = .965A-.258B -.258A-.965B 0 19.5(.965A-.258B)+27.5A+C

.965B+.258A -.258B+.965B 0 19.5(.965B+.258A)+27.5B+D -------(6)

0 0 1 0

0 0 0 1

Where ,

A=Cos(Ø1 +Ø3+15) , B=sin(Ø1+Ø3+15) , C=40CosØ1 D=40SinØ1

With substitution of bending angle of the bellows in the equation (6) gives the transformation

matrix of the finger. By multiplying the initial position of the finger with the transformation

matrix gives the theoretical final position of the finger tip point.

MATERIAL

ACRYLONITRILE-BUTADIENE RUBBER (NBR)

PROPERTIES AND APPLICATIONS

Nitrile Rubber (NBR) is commonly considered the workhorse of the industrial and automotive

rubber factories. NBR comes from a complex family of unsaturated copolymers of

acrylonitrile and butadiene. By selecting an elastomer with the appropriate acrylonitrile

content in the balance with other properties, the rubber compounder can use NBR in a wide

variety of applications involving oil, fuel, and chemical resistance. With a temperature range

of -40̊C to +125̊C, NBR can withstand all but the most severe automotive applications.

Industrial NBR finds uses in roll covers, hydraulic hoses, conveyor belting, graphic arts, and

seals for plumbing applications.

Like most unsaturated thermoset elastomers, NBR requires formulating with added

ingredients, and further processing to make articles that are useful. Additional ingredients

usually include reinforcement fillers, protectants, and vulcanization packages. Processing

includes mixing, pre-forming to required shape, application to substrates, extrusion, and

vulcanization to fabricate the finished rubber article. Mixing and processing are typically

performed on open mills, internal mixers, and extruders

CHEMISTRY AND MANUFACTURING PROCESS NBR is produced in an emulsion polymerization system. The water, emulsifier, monomers

(butadiene and acrylonitrile), radical generating activator, and other ingredients are introduced

into the polymerization vessels. The emulsion process yields a polymer latex which is

coagulated using various materials (e.g. calcium chloride, aluminum sulfate) to form crumb

rubber that is dried and compressed into bales. Most NBR manufacturers make at least 20

conventional elastomer variations, with one global manufacturer now offering more than 100

grades to choose from. NBR producers vary polymerization temperatures to create “hot” and

“cold” polymers. Acrylonitrile (ACN) and butadiene (BD) ratios are varied for specific oil

and fuel resistances and low temperature requirements. Some NBR elastomers are

hydrogenated so as to reduce the chemical reactivity of the polymer backbone, significantly

improving heat resistance. Each modification by either adding compounds or removing a few

contributes uniquely different properties.

ACRILONITRILE (ACN) CONTENT The ACN content is one of the two primary criteria defining each specific NBR grade. The

ACN level, by the reason of polarity, determines several basic properties, such as oil and

solvent resistance, low temperature flexibility, and abrasion resistance. Higher ACN content

provides improved solvent, oil and abrasion resistance along with higher glass transition

temperature.

MOONEY VISCOSITY AND POLYMER ARCHITECTURE Mooney viscosity is the other commonly used criterion for defining NBR. The Mooney test is

reported in arbitrary units and is the current standard measurement of the polymer’s collective

architectural and chemical composition. The Mooney viscosity of polymers will normally

relate to how they might be processed. Lower Mooney viscosity materials (30 to 50) will be

used ininjection molding, while higher Mooney products (60 to 90) can be used in extrusion

and compression molding.

GENERAL TYPES OF NBR

COLD NBR The current generation of cold NBR’s spans a wide range and variety of compositions.

Acrylonitrile content ranges from 15% to 51%. Mooney values range from 110 (very tough)

to pourable liquids, with 20-25 as the lowest practical limit for solid materials. They are made

with a wide array of emulsifier systems, coagulants, stabilizers, molecular weight modifiers,

and varying chemical compositions. Third monomers are also added to the polymer backbone

to provide advanced performance.

Cold polymers are polymerized at a temperature range of 5 to 15̊C, depending on the balance

of linear-to-branched configuration desired. The lower polymerization temperatures yield

more-linear polymer chains compared to that of the branched ones. Reactions are conducted

in processes universally known as continuous, semi-continuous and batch polymerization.

Cold rubber has a superior process ability as well as ability to produce vulcanized materials

with good tensile strength, expansion and flex resistance. They are also characterized by good

stereo regularity. Except a few SBR and NBR used for special purposes, most SBR and NBR

available in the market are considered cold rubber.

CROSS-LINKED HOT NBRCross-linked hot NBR’s are branched polymers which are further cross-linked by the addition

of a di-functional monomer. These products are usually used in molded parts to provide

sufficient molding forces, or back pressure, to eliminate trapped air. Another use is to provide

increased dimensional stability or shape retention for extruded goods. This leads to more

effective extruding and vulcanization of intricate shaped parts. These NBR’s also add

dimensional stability, impact resistance, and flexibility for a PVC modification.

CARBOXYLATED NITRILE (XNBR) Addition of carboxylic acid groups to the NBR polymer’s backbone significantly alters

processing and curing properties. The result is a polymer matrix with significantly increased

strength, measured by improved tensile, tear modulus and abrasion resistance. The negative

effects include reduction in compression set, water resistance, resilience and low-temperature

properties.

BOUND ANTIOXIDANT NBR Nitrile rubbers are available with an antioxidant polymerized into the polymer chain. The

purpose is to provide additional protection for the NBR during prolonged fluid service and air

exposure.

When compounding with highly reinforcing furnace carbon black, the chemical reactivity

between the polymer and the pigment can limit hot air aging capability. Abrasion resistance is

improved when compared with conventional NBR, especially at high temperatures. They have

also been found to exhibit excellent dynamic properties compared to other types. Hence, NBR

is and will continue to be a complex family of workhorse elastomers.

Load vs percentage of elongation graph for nitrile rubber

3. DESIGN EVOLUTION

PNEUMATIC ACTUATOR

The bellows used in this hand assembly has evolved from a very simple to a bit complicated

structure but performance has drastically improved. Initially only a tube made of nitrile rubber

was used with an eccentric hole. But to approach the size and dimensions of the human finger,

the design had to be changed.

Now in iteration the length of the bellow was decreased. But length is directly proportional to

stiffness. So to decrease stiffness of shorter bellow, material from the bellow had to be

removed. So grooves were made at the thicker side of bellow. These grooves assisted in

bending. In this design the size was reduced but the bending was not satisfactory.

Now to further reduce the dimensions of the bellow and increase its pressure withstanding

capacity and bending abilities, a new design was proposed. This bellow had corrugations on

top and flat surface at the bottom. The corrugations were thinner and the flat surface was

thicker. It had square shaped corrugations. This bellow also failed to generate expected

bending. Next design was that of a corrugated bellow with semicircular cross section having

internally corrugated cavities. This design was dropped taking into consideration the

manufacturing difficulties associated with it.

Fig : Nitrile rubber eccentric tube [first design] Fig : Nitrile rubber with corrugations

Fig : Bellow with square corrugations

The next bellow had similar dimensions to the previous bellow, but the corrugations are of

semi-circular shape. This bellow can bend up to 360for a pressure of 3 bar. This bellow failed

at a pressure of 3.5 bar pressure. So holding capacity of this bellow is very low. This bellow is

made with natural rubber. The same design was then manufactured using nitrile rubber.

Nitrile rubber was chosen due to its average stiffness and availability considerations. The

bellow design available to us was a bellow with external and internal square corrugations with

a rectangular base.

Fig :Nattural rubber bellow

Fig : Nitrile rubber bellow with internal and external square corrugations and rectangular base

This bellow had a top thickness of 1mm and base thickness of 2mm. The whole bellow had a

length of 30mm. Under 6 bar air pressure this bellow showed a bending angle of 450.

Our design objective was to develop a bellow that produces a higher bending angle for a

smaller pressure. We tested the nitrile rubber at the Rubber Research Institute of India to find

the Mooney-Rivlin constants for the material. We have used SolidWorks for designing the

bellow and as nitrile rubber has non linear properties, we achieved non linear simulation

analysis in Abaqus.

BELLOW WITH BASE CORRUGATIONS

To reduce the resistance to bending from the rectangular base, we corrugated the base to

match the top half of the bellow.

Fig : Nitrile rubber bellow with internal and external square corrugations and base corrugations

Fig :Abaqus simulation of nitrile rubber bellow with base corrugations for 5 bar pressure

The length was maintained at 30mm, top thickness 1mm, and base thickness 2mm. Using

Mooney-Rivlin properties this design was simulated in Abaqusat 5 bar pressure to give a

bending angle of 1300.Even though the modified bellow showed a tremendous increase in its

bending angle, the manufacturing of this design could be done only in a two piece mould like

the previous design.

Fig : Two piece bellow mould

The top half and the base had to be moulded separately and then attached together under high

temperature and pressure using a strong adhesive called Clubber. This two piece moulding

caused a chance for leakage of air after repeated pressurising of the bellow. To resolve this

problem the bellow has to be made in a single mould.The square internal corrugations created

a resistance for removal of the core pin after the bellow was manufactured.

Fig : Core pin with square corrugations

BELLOW WITH TRIANGULAR CORRUGATIONS

To simplify the manufacturing process and design a single mould bellow, the corrugations

were made triangular. The triangular corrugations on the core pin would cause as much

resistance during removal as the square corrugations.

This model has a top thickness of 1.5mm and base thickness of 2mm. Length has been

reduced to 27.5mm.

Fig : Nitrile rubber bellow with triangular corrugations

Fig :Abaqus simulation results of triangular corrugated bellow at 5 bar pressure

Simulation in Abaqus for a pressure of 5 bar gives a bending angle of 1150.

3.1.3 SHORTER BELLOW WITH TRIANGULAR CORRUGATIONS

Another attempt at reducing the length of the below was done. The triangular corrugated

bellow was reduced to a length of 21.5mm.

Fig : Shorter bellow with triangular corrugations Fig : Abaqus simulation at 5 bar pressure

The reduction in length caused the bending at 5 bar pressure to reduce to 800.The core still

couldn't be removed without resistance from the manufactured bellow. Hence, a different

design was developed.

3.1.4 CIRCULAR BELLOW WITH DIFFERENT TOP AND BASE THICKNESS

A circular bellow was developed with different material thickness on each side. This

difference in thickness caused an eccentricity that caused the bellow to bend in a certain

direction.

Fig : Circular bellow simulation for different top and bottom thicknesses

Several models with different top and base thicknesses were designed and simulated at 5 bar

pressure. But no design had any significant bending angle advantage over the previous

designs. So, the circular bellow was rejected.

3.1.5 TAPER BELLOW WITH TRIANGULAR CORRUGATIONS

To make the core pin removal easier, the internal and external corrugations were tapered. This

tapering inhibits the bending of the bellow, so to counter the effect of the taper, the length was

again raised to 27.5mm.

Fig : Nitrile rubber taper bellow Fig : Core pin for taper bellow

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

jj

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.

CAPACITOR DISC AECAn aluminum electrolytic capacitor, or shorter electrolytic capacitor (e-cap), is

a capacitor which anode (+) consists out of a pure aluminum foil with etched surface, covered

with an uniformly very thin layer of non-conducting aluminum oxide which operates

as dielectric. The electrolyte covers the rough surface of the oxide layer and operates as

second electrode, the cathode (-). E-caps have the largest capacitance values per unit volume

compared to the two other main conventional capacitor families, ceramic and plastic film

capacitors

RESISTOR .25W RES 1MP

The function of a resistor is to contain the flow of electric current in an electronic circuit.

Resistors are classified into two classes of resistors; fixed resistors and the variable resistors.

A resistor is made of either carbon film or metal film.

CAPACITOR 1000/25v 1mp

An electrolytic capacitor is a capacitor that uses an electrolyte (an ionic conducting liquid) as

one of its plates to achieve a larger capacitance per unit volume than other types. The large

capacitance of electrolytic capacitors makes them particularly suitable for passing or

bypassing low-frequency signals and storing large amounts of energy.

Relay OEN 46-05-2CE

Signal relays are used for low level current switching, often below 2A but up to 40A. Some

applications for signal relays include communications, AC control, security, measurement and

control equipment, automotive devices and audio visual devices.

9. PCB

A printed circuit board (PCB) mechanically supports and electrically connects electronic

components using conductive tracks, pads and other features etched from copper

sheets laminated onto a non-conductive substrate.