A CONCEPTUA L DESIGN OF A RAPID RECONFIGURATION METHOD [602283]

A CONCEPTUA L DESIGN OF A RAPID RECONFIGURATION METHOD
USED IN MULTI -POINT FORMING DIES

Muhammad Tayyab Rabbani1, Dr. Ijaz Ahmed Chaudhry1, Adnan Ahmed Naeem1,

1“Universi ty of Management and Technology, Department of Industrial Engineering
CII Johar Town, Lahore, Pakistan

Corresponding Author: Muhammad Tayyab Rabbani; Email: [anonimizat]

Abstract: Due to continuously changing customer’s
demand, market trend has now been changed. Companies
are now heading towards flexible manufacturing system.
The focus is now shifting from mass production to small
batch production, high variety with minimum time -to-
market. In the field of sheet metal forming, the flexibility
can be achieved by using reconfigurable dies and fixtures.
These dies and fixtures can configure themselves according
to the shape required. The reconfigurable multi -point
forming discrete die is composed of small pins. The surface
of the die is configured by adjusting the vertical positions of
the individual pins. The vertical positions of the pins are
controlled by some kind of pin actuation system. Differe nt
type of pin actuation methods have been proposed in the
past. In this research work, different pin actuation schemes
are studied, their pros and cons are discussed and finally, a
conceptual design of a new technique of pin actuation is
presented and compared with some renowned pin actuation
schemes.

Keywords: reconfigurable die, discrete pin die, multi -point
forming (MPF), sheet metal forming, CAD/CAM, pin
actuation method

1. INTRODUCTION

In the development of a new product, the development
of dies, molds and fixtures is the most time consuming
and expensive step (Walczyk D. , 1996) . Researchers
are continuously working on it to develop new
technologies to reduce the cost and time associat ed
with it. Now a days market requirements are
continuously changing, customer demands more
variety and customized products in minimum time.
Current dies and mold making techniques are designed
for minimum variety, mass production. So it is not
possible fo r the conventional systems and technologies
to meet the requirements of current and future market.
This give rise to the concept of flexible manufacturing
systems. The introduction of flexibility in the case of
molds, dies and fixtures are of great importa nce, as
major cost and time is associated in their development.
The concept of reconfigurable discrete dies was evolved in early 20th century. These reconfigurable
dies fit themselves well in the flexible manufacturing
systems. The reconfigurable machines are composed
of integrated hardware and software, which are
capable of reconfiguring or reorganizing them selves
safely and rapidly (Mehrabi, 2000) .

Fig. 1 . Reconfigurable die developed at University of
Galati (Paunoiu V. T., 2010)

In the field of sheet metal forming, the flexibility is
achieved by usi ng multipoint forming (MPF)
principle . Reconfigurable dies follows this principle of
multipoint forming (MPF). In the reconfigurable die,
the multi point forming is achieved by configuring the
die surface, consisting of densely packed matrix of
active discrete punches called pins , according to the
geometrical configuration of the final part (Paunoiu V.
N., 2006) . The configuration of the die surface is
governed b y the relative vertical pos itions of the pins.
The data for the vertical heights of the pins is provided
from the CAD/CAM/CAE software. Using the
information from CAD/CAM/CAE software, the
control system prepares the die for a new setup. The
whole proces s of sheet metal forming by using
reconfigurable dies is shown in the Fig . 2.

Fig 2. Process flow chart of sheet metal forming using reconfigurable dies

2. BACKGROUND FOR DIFFERENT PIN
ACTUATION METHODS

Selection of pin actuation method in reconfigurable
tooling plays a very important role. Many researchers
have worked in this area and try to come with a robust,
accurate, speedy, reliable and inexpensive solution .
One of the earlier applications of reconfi gurable
tooling is in the manufacturing of leaf springs for
vehicles. The first known patent for this invention was
awarded to Ansted (US Patent No. 483,094, 1892) .
The device is composed of a forming frame and a
sliding frame. The movement of sliding frame is
controlled by a hand lever. Each frame has a row of
pins. The height of the pins are adjusted by having
adjustable collars of different lengths.

Fig. 3 . Machine for forming leaf spring by Ansted (US
Patent No. 483,094, 1892)

In 1920, a similar patent was awarded to Elkin, which
in addition to Ansted’s patent, has the fine adjustment
of individual reconfigurable pins (US Patent No.
1,331,630, 1920) . Another patent was awarded to
Williams and Skinner (1923) on a spring forming
device (US Patent No. 1,465,152, 1923) . It contains
uniformly spaced pins which are configured by the
rotation of a two threa ded shaft driven by chain and
sprocket (US Patent No. 1,465,152, 1923) .
Fig. 4 . Manual Pin Actuation method by Williams (US
Patent No. 1,465,152, 1923)

All of the pin actuation schemes discussed above are
based on 2D forming principle. Later in 1943, Walters
extended this idea to 3D forming by adding multiple
rows of the pins for shaping the sheet metal parts (US
Patent No. 2,334,5 20, 1943) .
In 1969, Nakajima made the first attempt to
automatically reconfigure the pins (Nakajima, 1969) .
In his research, he mounted a push metal on the CNC
milling machine head stock to adjust the vertical
heights of the pins. Two approaches were used to
configure the surface of the die. (a) Numerical point to
point control using push metal to adjust the height of
each pin one by one (b) Using triangular shaped
positioning stylus, which swept forward and backward
over the pins to incrementally change the surface of
the die.

Fig. 5 . Pin configuration using positioning stylus
(Nakajima, 1969)

In 1980, Pinson developed an automatically controlled
reconfigurable pin tooling in which is each pin is
connected to a separat e computer controlled servo
actua tor as shown in fig. 6 . (US Patent No. 4212188,
1980) .

Fig. 6 . Computer controlled servo -actuators (Pinson, 1980)

Woodall was granted a patent in 1983 for open ended
tubes containing pins and immersed in the fluid bath
(US Patent No. 4390491, 1983) . The pins are lifted to
a specific height by a vacuum device mounted on a
three axis servo m echanism, which in result draw fluid
in the tubes. The elevation of a pin is maintained by a
check valve at the bottom of the tube.

Fig. 7 . Woodwall Apparatus for pin actuation (US Patent
No. 4390491, 1983)

Hoffman (US Patent No. 5851563, 1998) , Laskowski
and Pintz (US Patent No. 5796620, 1998) , and Umetsu
and Miura (Patent No. 5192560, 1993) , used three axis
lead screw driven serv o mechanism to push each pin
to its specific height and then locked them in their
position by some kind of mechanism. Later in 1991,
Finckenstein and Kleiner developed a four axis servo mechanism to adjust the height of threaded rods
individually to give t he die a specific shape. The die is
composed of densely packed square cross sectioned
pins (Kleiner, 1991) . In another design six servo
motors are used, four for pin height adjustment and
two for longitudinal and transversal mo vement. Thus
total 12 motors were used, 6 for lower half and six for
upper half of the die (Heo, 2010) .
In Nakajima’s design (1969), there was a limitation of
dragging adjacent pins when adjusting the height of a
specific pin. Later in 1998, Walczyk and Hardt solved
the Nakajima’s problem by introducing sheet metal
separators between the rows of the pins (Walczyk D.
F., 1998) . Pin height adjustment by using lead screw
mechanism is another effective me chanism. It contains
a hemispherical head hollow pin having internal
threads with a self -locking lead screw inside it. Height
of the pins are adjusted either in serial fashion or in
parallel fashion with the help of servo motor attached
to the lead screw. When all the pins reached at their
required heights, as specified in the CAD data, they
behave as a solid die. In the Haas (1996, 2002) design,
shaft -driven lead screw was used to adjust the height
of 42×64 pins matrix (US Patent No . 5,546,784, 1996)
(Haas E. S., 2002) . In 1997, Boas developed a 48×72
pins matrix die capable of sequentially adjusting 16
pins at a time (Boas, 1997) . In 2008, Liu et al. at Jilin
university of China, developed a group of motor
driven lead screws reconfigurable die capable of
adjusting all pins simultaneously (Liu, 2008) .

Fig. 8 . Lead screw pin actuation (Liu, 2008)

In 2000 (Im, 2000) , the Northrop Grumman
Corporation decided to carry out a research to develop
three different pin actuation systems and compare
these three different pin actuation schemes. The first
team from the Massachusetts Institute of Technology
develop Sequential S et-up Concept of pin actuation
(Fig. 9 ). This concept was similar to Finckenstein and
Kleiner. The additional advantage is of its shorter pin
setting time, which is achieved by mounting a group
of 4×4 servo motors on the X -Y servo head. The group
of 4×4 mo tors couples with the pins through hex
coupler and set their heights in a parallel fashion.

Fig. 9 . The Sequential Set -up Concept of pin actuation (Im,
2000)

The second team at Rensselaer Polytechnic Institute,
developed a new mechanism for pin adjustment, which
involves hydraulic actuation of the pins as shown in
the figure 7 (Walczyk D. F., 2000) . The body of pin is
hollow and act like hydraulic cylinders. Each pin has
a stationary hollow piston in it and connected to in -line
servo valve. The hydraulic fluid pressure inside the
pins is controlled by servo valves, which lifts the pin
to a specified height. Single source of hydraulic power
is used to provide pressurized hydraulic fluid to lift
each pin through series of plenums. The entire pin
matrix is adjusted in a parallel fashion. This is
achieved by moving all pins upwards against a slow
moving platen. The pins continue to move up ward
with the platen unless required height of a specific pin
is reached. The in -line servo valve of that specific pin
is closed to hold the pin in its position while the
remaining pins continue to move upward with the
platen until their specified height i s reached. When all
pins reached their specified heights, the whole pin
matrix is clamped to form a rigid tool. The whole
process is controlled by a computer. The home
position of the pins is achieved by unclamping the
whole pin matrix and opening all the in-line servo
valves to evacuate the hydraulic fluid.

Fig. 10 . Hydraulic actuation of the pins (Walczyk D. F.,
2000)

The third team from Northrop Grumman Corporation
came up with “shaft driven lead screw concept”. The servo motors are mounted externally on the drive
shafts. The worm gear is attached to drive shaft. The
clutches present between the worm gear and pin’s lead
screw engages and disengages the worm gears with the
pin’s lead screw. The lead screw rotates inside the
hollow pin to adjust its heig ht (Fig . 11).

Fig. 11 . Shaft Driven Lead screw Concept (Im, 2000)

3. PROS AND CONS OF DIFFERENT PIN
ACTUATION METHODS

Construction and working of different pin actuation
schemes employed in reconfigurable MPF dies were
discussed previous ly. In this section, the pros and cons
of some renowned pin actuation methods are
discussed. Before going in to discussion, following
important factors that are dependent on the type of pin
actuation method selected should be kept in mind:
Pins size and shape
Accuracy
Repeatability
Resolution
Speed of reconfiguration
Economy
It is not possible to have all the discussed factors
justified in a single pin actuation scheme.
Compromises have to be made on the selection of a
particular pin actuation scheme. Depending on the
required final sheet metal product, a particular pin
actuation method is selected. For example, for
producing gentle curves, as in the case of the
production of fuselage sheet metal parts of a plane,
there is no need to use very small cross -sectional size
of the pins, as it affects the economy of the system.
The quality of the sheet metal part produced by
discrete die depends mainly on the pins cross sectional
size, pin’s shape and pins matrix density. Smaller the
pin’s cross sectional size and greater the density of
pins matrix, the more intricate shapes and sharp curves
can be produced on the part . But the cross sectional
size of the pin is mainly limited by the selection of pin
actuation method. Similarly, the accuracy,
repeatability, resolution, speed of configuration and

economy is mainly based on the selection of pin
actuation method.

3.1 Pin actuation using Stylus

First of all, discussing the limitations and advantages
of pin actuation using stylus. The main limitation in
pin actuation using stylus is the dragging of adjacent
pins due to friction, when a particular pin is moved.
This affects the accuracy, resolution and repeatability
of the s ystem. Secondly, considerable time is
consumed in the reconfiguration of pins, as stylus has
to move forward and backward several times to
acquire a desired shape. Thirdly, a separate clamping
mechanism is required to hold the pins to form a rigid
tool. Now focusing on its advantages , reconfiguration
of pins only requires a stylus to reconfigure pins which
reconfigure the pins one by one and does not require
large space. Resulting in more densely packed matrix
of pins, capable of producing more sharp curves and
surfaces. Secondly, solid pins are used instead of
hollow pins, which requires less space. This model is
also economical one, as fabrication of solid pins is
simple as compared to hollow pins.

3.2 Pin actuation using Sequential Set -up

In Sequential Set -up for pin Actuation, the pins are
hollow fro m inside and mounted on the lead screw.
Group of motors are used to adjust the height of pins
by rotating the lead screw in them. Keeping in view
these factors, only gentle curves can be obtained.
Because hollow pins have greater cross sectional area
of pi n tips as compared to solid ones. Speed of pin
actuation is dependent on the number of motors in the
motors matrix. Number of motors and hollow pins
contribute to its high cost. Using lead screw, the back
lash error is always present in it. If no feedback system
is present, the amount of backlash effects accuracy,
repeatability and resolution. Its advantages include self-locking mechanism in the pins, which eliminates
the need of side clamping. The design is simple and it
requires less wires and circuitry.
3.3 Hydraulically actuated pin mechanism

Hydraulically actuated pin mechanism used hollow
pins to have fluid in it. Like all other pin actuation
mechanism having hollow pins, only gentle curves can
be produced as compare to solid pins. Secondly, no
self-locki ng of pins is present, therefore side clamping
of pins is used. Side clamping requires more space and
cost as compared to self -locking. Pressurized
hydraulic fluid is used to lift the pins, so there are
chances of leak in the joints, especially in the pin -valve
interface. Any leakage will affect the output of the
system. Each pin is attached to a separate servo control
valve, so complex wiring system is present. This
complexity contributes towards its high cost. Its main
advantages is, it required less time to reconfigure the
pins to achieve the desire shape of the die. Because all
pins are set in a parallel fashion. Only single power
source is required to lift all pins at the same time.

3.4 Pin Actuation using Shaft driven Lead screw

Like the above discussed Sequential Set -up for pin
actuation, the shaft driven lead screw also employed
the hollow pin with internal threading. This lead to
greater cross sectional area of pin tip. Which in turn is
used to make to make gentle curves, not the sharp
ones. Secondly, high cost is associated with its
manufacturing due to its complex design and the use
of hollow pins and servo motors. Thirdly, the accuracy
of the system is affected by the amount of back lash
error present in it. Feedback system is required to
eliminate the effect of back lash error present in it. Its
advantages include: no side clamping is required, a s
self-locking of pin is present in it. Also the speed of
reconfiguration is high, as all pins are positioned in
parallel fashion.

Table 1. Comparison of different pin actuation methods
Pin actuation
using Stylus Pin actuation
using Sequential
Set-up Hydraulically
actuated pin
mechanism Pin Actuation using
Shaft driven Lead
screw
Type of pin Solid Pin Hollow pin
Internally threaded Hollow Pin
Smooth internal
bore Hollow pin
Internally threaded
Speed of pin
Configuration Slow. Depend on
the number of
passes of stylus Dependent on the
number of servo
motors High. All pins
move in a parallel
fashion Dependent on the
number of servo
motors
Clamping External
Clamping
Required Self-Locking .
No external
clamping External Clamping
Required Self-Locking .
No e xternal clamping
Potential
Cause of
Failure Adjacent pins
start to move
along with the
pin Chances of Back
lash error Leakage Chances of Back lash
error

Power source 3 Servo motors
connected to the
stylus. Servo motors.
Quantity depends
on speed of
configuration Single hydraulic
power source Servo motors.
Quantity depends on
speed of
configuration
Economy Economical.
Simple
Less power units
Solid pins Less economical
Hollow threaded
pins
More power units
Less economical
Mess of wires
External clamp ing
Hollow pins Less economical
Hollow threaded pins
More power units

4. DESCRIPTION OF PROPOSED PIN
RECONFIGURATION METHOD
In this section, a conceptual design of a rapid pin
reconfiguration method is proposed. First of all, the
main components of the proposed rapid
reconfiguration pin method are discussed one by one
then its construction and working mechanism is
explained . Its main components include:
 Pins – forming pins and reconfiguration pins
 Pins gripping bo x containing pins grippers
 Pins lifting system – Servo ball jack screw for
lifting Pins gripping box
 Supporting Structure for holding all the
components

Fig. 12 . Main components of proposed pin actuation model

4.1 Pins
In the proposed design , based upon their function , two
different kinds of pin matrices ar e used. One pin
matrix is composed of ‘forming pins’ and the other
matrix of pin is c omposed of ‘reconfiguration pins ’.
The both matrices of pin uses solid pins. The forming
pin matrix is used to bear the forming load to form the
sheet metal part while the reconfiguration pins are
used to set the forming pins at the required height.
4.1.1 Forming pins
The forming pin has a uniform square cross sectional
shape, with its top end is hemisphere and its bottom
end is flat with a dimple in its center. One main reason,
for using square cross sectional forming pins is the
minimum branching off the clamping load during
clamping (as used by Walczyk) . The worst case
loading scenario exists when a forming pin protrudes
above the adjacent pins. Such a pin may fail under excessive buckling and bending. Consider such a
protruding pin as a Cantilever beam.

Fig. 13 . Forces acting on the protruding Pin

σmax =𝐹𝑝𝐿𝐶𝑚𝑎𝑥
𝐼 (1)
Where,
σmax = maximum tensile bending stress

𝐹𝑝= Bending Load
L= Length protruding above the adjacent pins
𝐶𝑚𝑎𝑥= the distance between the neutral axis of
the pin and the part of its cross -sectional
geometry farthest from this axis
I = second moment of area of the pin's cross –
section
The top end of the forming pin has a spherical shape
so that it may not penetrate through the interpolator or
sheet metal. Secondly, the spherical end only contact
the sheet at a tangency point. The bottom end of the
pin is flat and has a di mple. The dimple is used to
locate the head of reconfiguration pin.

Fig. 14 . Shape of the forming pin

4.1.2 Reconfiguration pins
The reconfiguration pin has a circular cross sectional
shape. It has a smaller cross sectional area as compared
to the forming pin’s cross sectional area. The top end
of the reconfiguration pin has a spherical shape while
its bottom end is flat. The reconfiguration pin lifts the
forming pin to the required height by us ing its
hemispherical tip to locate the dimple at the bottom
center of the forming pin. After setting the forming pin
to a specific height, the reconfiguration pins are
retract ed to the datum surface. The maximum load FR
that a reconfiguration pin has to lift is the weight of the
FF forming pin and the F frictional forces that exists
between the walls of that forming pin and the adjacent
forming pins/ walls of the clamping box.
FR = F F + F (4)
A reconfiguration pin slides through two holes that
serves the purpose of a guide. The reconfiguration pin
has serrations at its middle. This serration helps in
proper gripping of the pin by the small spring loaded
grippers.
Fig. 15 . Shape of Reconfiguration Pin

4.2 Pins Gripping Box
The gripping and lifting of the reconfiguration pins is
carried out in pins gripping box using small grippers
associated with each reconfiguration pin . This box is
lifted up with a constant feed by a controlled lifting
mechanism. Only those reconfiguration pins will
move upward along the gripping box, that have been
gripped by the gripper s located inside the gripping
box. The small grippers are mounted on the slant bed
inside the gripping box. The spring loaded gr ippers are
actuat ed by a power source. The gripping box have
four bushes near its corners which slides on the four
pillars of the structure.

Fig. 16 . Pins Gripping Box

4.3 Pins grippers
The small spring grippers are located inside the pins
gripping box. The spring gripper performs gripping
action with the help of a gripping plate. Gripping
plates are curved plates having internal radius equal to
the radius of reconfiguration pins. The internal surface
of gripping plate has serrations. During gripping
action, the serrations of gripping plate interlock with
the serrations of reconfiguration pins. The extent to
which these grippers can hold load is mainly
dependent on the area of contact surface of the
gripping surface, pneumatic force, and frictional
constan t between them, pitch and depth of serrations.
The gripping plate is attached to a strip spring. The
strip spring is attached to an inflexible cord. The

gripping action is done by pulling the cord using
pneumatic power source .

Fig. 17 . Spring Loaded Grippers

4.4 Pins lifting system
The servo ball jack screw is used to lift the gripping
box with a constant required feed. The servo ball jack
screw lies below the gripping box. The servo ball jack
screw is ca pable of lifting the load of both pins
matrices , gripping box and frictional losses. After
reaching its maximum height, they servo motor stops
and wait for the clamping action and then it retracts to
its datum position.

Fig. 18. Servo Ball Jack Screw

4.5 Supporting Structure
Its structure consists of pillars, base and shelves. The
four pillars are used for holding the load of all
assemblies mounted on it. The four pillars also act as
guiding rods for the movement of gripping box. A
perforated shelf is attached on the top of th e pillars.
These perforations are round in shape. The diame ter of
each perforation is slightly larger than the diameter of
reconfiguration pin. A second shelf exist below the
gripping box and mount on the base. This second shelf
is a solid plate and act as a datum plane for the
reconfiguration pins . The base is a rigid structure on which lies whole load of the assembly. The servo ball
jack screw assembly also rests on the base.

Fig. 19. Supporting Structure

5. WORKING
Support software have already been developed that
uses data files from CAD software to analyze and filter
the required information from the CAD files to find the
required height of the pins and automatically generate
control instructions for the actuation of servo motors
and other actuating devices. The support software used
for multipoint forming consists of two modules i.e.:
 CADS (CAD Subsystem)
 CCS (Computer control Subsystem)
The CADS uses the data files from CAD to develop 3d
models, select the parameters for the multi -point
forming met hod, calculate the positions of the pins and
simulate the forming process. Then the data generated
by CADS is transferred to CCS. The CCS is a multi –
axes numeric control system. The CCS uses data from
CADS to create numerical control commands for the
servo actuators. After receiving control commands
from CCS, the servo motors adjust the height of each
pin. The function of CCS includes: data exchange
from the CADS software, adjusting process
parameters, data exchange with the slave control
devices via field busses, using feedback from sensors
to develop error signal, shape contour control and data
save etc.
In the first step , a 3d model of the required surface
geometry is produced in a CAD software. Then the
support software CADS uses the data file produced by
the CAD software to generate data regarding the
height of each pin. Then the data generated by CADS
is transferred to CCS. Based on the CADS data, the
CSS generate the control signals for the servo motor
and the pneumatic actuators. After receiving comm and
from CCS, the servo ball jack screw start lifting the pin
gripping box with a constant specified feed. Inside the
gripping box, t he gripping action performed by the
spring grippers is done by pneumatic actuators on the
control command generated by CCS. The
reconfiguration pins were initially resting on the

datum shelf. Only those reconfiguration pins are start
moving upward along the gripping box , which were
gripped by the spring grippers. These upward moving
reconfiguration pins , after passing through the
perforation in the perforated shelf , start lifting the
forming pins, which were initially resting on the
perforated shelf. These perfor ations also act as a guide
for the reconfiguration pins. The configuration of the
pins is done in a parallel fashion, means all pin are
configured simultaneously. Sensors are provide to
measure the positions of the forming pins and give
feedback signal to CSS for any corrective action if
needed. After reaching t he specified height, the
gripping box stops and wait for the clamping action to
be performed. After clamping the forming pins, the
whole matrix of pins turns into a rigid tool. Then the
small spring grippers releases the reconfiguration p ins,
which they we re gripping . The reconfiguration pins
falls on the datum surface with gravity. Proper
damping and thrust bearing material is applied on the
datum shelf. After releasing the reconfiguration pins,
the pin gripping box start moving downward to its
initial pos ition. Now the required surface geometry has
been produced on the forming pin matrix. Then
stretched sheet of interpolator is place d above the
forming pin tips. On this sheet of interpolator, sheet
metal blank is placed. Then hydroforming punch
applies the forming load on the sheet metal blank to
form it according to the surface geometry generated by
forming pins.

6. CONCLUSION
Despite of having many advantages of the
reconfigurable discrete dies , this manufacturing
technology is not widely adopted by industries. One
main reason incl ude is having complicated actuation
and locking methods of discrete pins. Second ly, its
high construction cost. Another reason for it’s not
widely acceptance in industry is that, it is used as a
stand -alone system. It full a dvantages can be
uncovered by integrating it into a complete
manufacturing system.
After comparing the proposed pin reconfiguration
technique with previous ly discussed pin
reconfiguration techniques given by researchers,
following advantages are found:  In most pin reconfiguration techniques, pin
actuation is done in series or one by one. A lot
of time is c onsumed in configuring the pins . In
this proposed hybrid rapid pin reconfiguration
mechanism, all pins are set in a parallel
fashion, means all pins are configured
simultaneously and in minimum time we are
able get the desired surface geometry on the
pins bed .
 Solid pins are used in the proposed design.
The solid pin requires less area as compared to
hollow pins having the same cross sectional
area. This r esults in more intricate and sharp
curves can be produced on the part as
compared to hollow pins having same cross
sectional area.
 The design of pins is simple and inexpensive.
The manufacturing cost of hollow pins is high
as compared to solid pins. More m achining is
required to hollow a solid pin and then
produce internal threads in it. Its complex
manufacturing leads to high chance of quality
defects.
 In most pin actuation schemes, multiple power
sources are used to configure the pins. More
servo motors a re used to decrease th e pin
configuration time. In proposed rapid pin
reconfiguration mechanism o nly two power
sources are used. One is pneumatic source and
other is a servo motor. which means, it is more
environment friendly , running cost is low and
Initial investment is less
 In most pin actuation schemes lead screw is
used to lift the hollow pins. Which requires
proper lubrication between the moving
surfaces. Also the effect of backlash error is
always present. Which in turns affects its
accuracy. In the proposed rapid pin
reconfiguration mechanism backlash is
minimized by using ball screw in servo ball
jack screw. Also serrations in the grippers and
reconfiguration pins results in a firm grip. No
slippage is present. This results in a better
accuracy .
Some of its disadvantages are:
 More space is required
 External clamping is required

Table 2 . Comparison of different pin actuation methods with the proposed pin actuation method
Pin actuation
using Stylus Pin actuation
using
Sequential Set –
up Hydraulically
actuated pin
mechanism Pin Actuation
using Shaft
driven Lead
screw Proposed
Method
Type of pin Solid Pin Hollow pin
Internally
threaded Hollow Pin
Smooth internal
bore Hollow pin
Internally
threaded Solid Pin

Speed of pin
Configuration Slow. Depend
on the number
of passes of
stylus Dependent on
the number of
servo motors High. All pins
move in a
parallel fashion Dependent on
the number of
servo motors High. All
pins move
in a parallel
fashion
Clamping External
Clamping
Required Self-Locking .
No external
clamping External
Clamping
Required Self-Locking .
No external
clamping External
Clamping
Required
Potential
Cause of
Failure Slippage
among pins Chances of
Back lash error Leakage in
piping Chances of Back
lash error Leakage in
pneumatic
system
Power source 3 Servo
motors
connected to
the stylus. Servo motors.
Quantity
depends on
speed of
configuration Single hydraulic
power source Servo motors.
Quantity depends
on speed of
config uration Two.
1 servo
1
pneumatic
Economy Economical.
Simple
Less power
units
Solid pins Less
economical
Hollow
threaded pins
More power
units
Less economical
Mess of wires
External
clamping
Hollow pins Less economical
Hollow threaded
pins
More power
units
Economical
Less power
sources
Sold pins

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