DESIGN AND FABRICATION OF A PRINTING BLOCK MACHINE

Thesis Overview

1.1 INTRODUCTIONNigeria 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 COLLECTIONThere 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 PRINTINGThe 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 1Material 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
0.0972Ceiling 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 2.3 831.2OBSERVATION:
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 DEPOSITIONGold 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 PRINTSince 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 SPECIFICATIONThe printing (blocking) machine to be designed must be able to:
1.4.1 produce sharp print on paper from gold coated sheet
1.4.2 require small effort for operation
1.4.3 resist failure of excessive effort should be applied.
1.4.4 Be easily operated by anybody
1.4.5 Produce as many per unit time as possible.
1.4.6 Must be relatively cheap in every respect
1.4.7 Should be compact and portable
1.4.8 Should nut be too heavy – can easily be moved from one location to another
1.4.9 Position of operator in use should be convenient not tiring
1.4.10 Should be durable
1.4.11 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.
1.4.12 Manufacture ability – can be manufactured within the limits of available materials and processes in the school workshop and neighboring establishments.