CHAPTER ONE
1.1 INTRODUCTION
Nigeria
in recent times lays strong emphasis on mass literacy and indigenous technology. Printed matters are indispensable materials
in mass literacy campaign and the trend
towards indigenous technology imposes a
severe clamp down on imputed
engineering including printing block machinery.
Thus the situation is such that
make the acquisition of printing
machinery from outside our boards extremely difficult.
Therefore
to lessen the economic strain on the
mass literacy campaign local production
of printing machinery is apparently
imperative. It is this fact that
rendered integrative to the conception and realization of this low cost but
efficient printing machine based entirely on local technology and resources.
The
present machine is very useful in the printing of many items like paper backs
cards etc. its design and fabrication is expected to motivate and advance the
design and fabrication of other machines destined for similar purpose and based
on indigenous technology and resources.
1.2 LITERATURE REVIEW AND DATA
COLLECTION
There were no available books in
printing in both the state and school libraries that actively dealt with
printing technology. The only books available were those on the
history of ‘Types’ and trade journals advertising products of foreign
companies which were fund to be of little or no relevance.
However
a visit to the government printing press gave us an opportunity to study the
‘types’ available and the basic operations of
the giant printing (Blocking)
machine with respect to the ‘Types’ from there we were able to establish;
(a)
The
effect of temperature on the amount of gold deposited from sheet (sharpness of
print )
(b)
The effect of life time on the gold foil sheet
depositor.
(c)
The
effect of pressure on the amount of
gold deposited from sheet (sharpness of print )
(d)
The effect of size of ‘types’ on the
sharpness of print (amount of gold deposited )
Definition:
Types : These are the characters or
alphabets that forms the letters.
Print :- This is the mark or impression produced on paper due
to the types. Gold foil sheet depositor
:- is a thin rectangular cellophane sheet
coated with gold compound.
1.3
EXPERIMENTAL DETERMINATION OF PRESSURE FOR PRINTING.
The print there must be impact force between two surfaces on e of which contains the ‘type’
and the other the paper on which print will be made. The force produces the necessary
pressure for printing.
Consider alternative ‘B’ of
the possible design solution. Impact
force is due to the acceleration of mass
of moveable plate and rail against the stationary letter box located on the
element box. The pressure for printing is impact force for a constant surface area
Impact surface area the pressure varies with variation in the impact
force. Similarly the impact force varies
with the mass and acceleration. But the
mass is constant and equal to mass of rail plus mass of moveable plate
hence only the acceleration varies. Therefore in this experiment effort has
been made to determine.
(a)
The pressure
required to print clearly on thin
cellophane sheet without perforating it.
(b) The pressure required
to print clearly on paper of average
thickness without perforating it
(c)
The pressure required
to print on cardboard sheet such that very sharp prints are obtained by varying the input acceleration
Materials: very light cellophane paper, paper back of higher education
exercise book ceiling sheet (card board)
silver sheets,
Apparatus: Election- speed printer machine
Definition: The electronic speed printer machine is a motorized
electronic motor. It has a device for varying the acceleration the
current input can varied hence the heat
generate and therefore the temperature varied.
Method: the acceleration is varied keeping the temperature and surface
area of impact constant. Already the
striking mass is constant. The following
values show the accelerations at which sharpest prints were obtained without
perforation of the materials after several trial. The corresponding forces and pressure are
also shown.
TABLE 1
Material
Accel. For sharpest print without perforation
Mass (m)
Force (ma)
Pressure (ma/a)
Cellophane paper
0.07mls 2
35kg
2.45N
2.45
0.0972 = 25.24 n/m2
Paper back of higher education note book
0.76 mls2
35kg
26.6N
26.6 = 273.N/M2
0.0972
Ceiling sheet
Cardboard
2.3 mls2
35kg
80.8n
80.8 = 831 N/m2
0.0.972
·
operating
temperature 1550c (fixed)
·
0.0972
= area of foolscap sheet (fixed)
for the heating coil, the
heat dissipated given by H. = 12 Rt where 1 = current passing in ampere R = resistance of
coil in ohms and t = duration time in seconds. It varies directly with temperature which is the measurement of heat
hence the determination of:
TABLE 11
EFFECT F TEMP. ON SHARPNESS
OF PRINT
Temp
(0 c)
Cellophane paper
Paper back of higher Edu. Book
Ceiling sheet cardboard
Acceleration (m/s2)
Pressure (N/m2
25
No print
No print
No print
0.07
25.2
50
Slight deposit
No print
No print
0.07
25.2
155
Sharp print
No
print
No print
0.07
25.2
200
No
print
0.07
25.2
250
Shrinks
Non – clear print
No print slight deposit
0.07
25.2
25
Slight deposit
No print
No print
0.76
273
50
Clear print
Slight print
No print
0.76
273
155
Perforation
Sharp print
No print
0.76
273
200
Burns / shrins
Slight groove
Slight deposit
273
250
Increased burns
Deeper grooves
Non- clear print
0.76
273
25
Fairly clear print
Slight deposit
Slight deposit
2.3
831.2
50
Perforation
Clear print
Non-clear print
2.3
831.2
155
Burns/ shrinks
Sharp print with very deep groove
Sharp print
2.3
831.2
200
Increased burns
Perforation begins
Grooving begins
2.3
831.2
250
Increased burns
Deeper perforations
Deeper groove
2.3
831.2
OBSERVATION:
From tables 1 and 11 it can be
observed that
(a)
The
sharpness of print varies directly with the acceleration and hence the operating
pressure.
(b)
The
sharpness of print varies directly with temp.
(c)
No
matter how high the pressure applied at room temp.250c) a sharp
print can never be obtained before and even after grooving and consequent
perforation occurs.
(d)
By
increasing acceleration and decreasing tem. Or vice- versa sharpness of prints
can be altered provided the temp. Variation does not require a fall below 1550c.
CONCLUSION:
Sharpness of print depends on
pressure and on temp (from about 1500c upwards).
(a)
EFFECT OF LIFE TIME ON GOLDEN FOIL DEPOSITION
Gold
foil sheet as already defined is a very thin rectangular cellophane sheet
coated with golden compound chemical such that temperature and pressure can be
regulate its deposition on paper. Form the time of production (coating of gold
on cellophane) the coherency of gold
deposit decreases with time until a times when the layers of the compound
starts peeling off from the sheet by itself.
Hence sharpness of print depends on
life time of coating. This fact
was established after observing different life
golden sheets used under same temperature and pressure.
(b) THE EFFECT OF SIZE OF
TYPES ON THE SHARPNESS OF PRINT.
Since pressure = force /
Area the same force applied ‘types’ having smaller surface area exerts greater
pressure in direct proportion to the ratios of
their surface area.
1.4 DESIGN SPECIFICATION
The printing (blocking) machine to be designed must be able
to:
1.1.1
produce sharp print on paper from gold coated sheet
1.1.2
require small effort for operation
1.1.3
resist failure of excessive effort should be applied.
1.1.4
Be easily operated by
anybody
1.1.5
Produce as many per unit time as possible.
1.1.6
Must be relatively cheap in every respect
1.1.7
Should be compact and portable
1.1.8
Should nut be too heavy – can easily be moved from one location to another
1.1.9
Position of operator
in use should be convenient not tiring
1.1.10
Should be durable
1.1.11
should have replaceable parts – using bolts, screws
and other forms of assembly rather than welding. Also using components whose forming / manufacturing process is less
complex so the user can easily replace damaged parts.
1.1.12
Manufacture ability –
can be manufactured within the limits
of available materials and processes in
the school workshop and neighboring establishments.
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