“Develop success from failures. Discouragement and failure are two of the surest stepping stones to success.”
Printing equipment & maintenance (PEM)
Maintenance
The principal of maintenance is to extent the useful life of an asset. A proper maintenance will improve the production capacity with only existing capacity utilization.
Maintenance is usually viewed as a repair function of maintenance is composite in nature. In fact, maintenance keeps our entire system to be reliable, production and efficient.
Maintenance is not an activity confined or restricted to technical workers, supervisors, Fore-man or works managers in a factory. It affects and convers all human being in every sphere of life.
A doctor treats his patients to maintain their health.
A sadhu puts, in efforts to maintain his mental peace.
We eat food many times a day to maintain our body.
Thus, it is not that only technical personnel have to maintain their equipment. The term maintenance is all pervasive and covers all facets of our lives. Thus, it is very necessary to understand what, why and how of maintenance.
The case of a fire extinguisher and the case of a first aid box can be cited. It is an item that is rarely used, but whenever it is required to be used, it has to work properly. We can consider the possibilities of its not working is an emergency situation. In the case of a first aid box, once again, an item that can result in saving the life of a person in emergency or at times can resulting in causing more harm to a person who could have survived otherwise in normal circumstances. It is therefore, important that the content are there in it with proper identification by labelling along with the condition of the contents for life expiry and instructions to use as well.
Objectives of maintenance:
It saving in money, material & manpower.
Organizational structure: first of all the student may be made aware of the organization of the press plant. The maintenance wing can be identified and its structure concept can be discussed with relation to the size and nature of the organization.
Broadly, maintenance wings in press plant can be three types:
Now we can come to the point of printing press plant where all men, materials, money, equipment, machinery etc. are brought together for manufacturing process. Their idle time or down time becomes much more expensive.
Plant maintenance plays a very important role in production management because plant break down creates problems such as:
Categories for status of machines
Categories
Description
A
operational or production machine is fully productive.
B
set is being done, machine is temporarily idle, changeover to new job etc
C
Delay (waiting for every category except the first one represents a reduction in the utilization of equipment.
Unit - 2
HAND TOOLS AND OTHER MAINTENANCE AIDS
Material used:
Fuse wires of different rating:
Unit - 4
LUBRICATION
The lubrication of the moving parts of machine is important to the correct working of these parts over long period. Every press manufacturer supplies oiling and greasing schedule, indicating the point which need servicing and specifying the type of lubricant. Efficient lubrication plays such a vital part in the reduction of wear that its important cannot be overstressed. The presence of lubricating medium greatly diminished the following:
Classification of lubricants: lubricants can be broadly divided into:
They have low shear strength and adhere to the surface.
The solid lubricants are used where-
The most common solid lubricants which are used are graphite and malyubdenum disulphide.
The other are iron sulphide, silver iodine, lead monoxide, ag2so4, Teflon.
The solid lubricants are used in the form of dry powder or mixed with water or oil. The solid fill up the low spots in the surfaces of moving parts and form solid films.
Graphite: it the most widely used solid lubricants.
Besides this, lubricating oils acts as coding medium, sealing agent and preventer of corrosion.
Types of liquid lubricants:
However, the posses comparatively poor oiliness as compared to that of animal and vegetable oils.
The oiliness of petroleum oils can be increased by the addition of high molecular weight compound like oleic acid, stearic acid, etc.
Gases have the advantage of low viscosity changes with temperature and they are unaffected by nuclear radiation.
They have low inertia.
They also do not trip making them suitable for food industries.
They are of relatively low cost, easy to form and operate with less noise.
Both thermoplastic and themo-setting polymer are used.
Thermoplastic materials commonly used are PTFE, nylons PE and HDPE. These materials can be used as such as with fillers like graphite, bronze, HOS2 etc.
The lubricating property of grease is mostly decided by the characteristics of the oil used for preparing it.
Important greases are: calcium based grease, soda based grease, lithium based.
Method of lubrication:
Hand oiling for light loads and slow speeds. These are various methods in hand oiling. Such as countersunk hole, hole carried with ball and spring.
Oil pump, hand pump, and grease gun belong to this category.
Properties of lubricating oils:
Color coding: for the types of lubricant to be used.
MAINTENANCE OF PUMP AND COMPRESSOR
Maintenance of pump: these are several maintenance procedure that must be performed periodically for any centrifugal pump. Pump packing wears out, bearing must be lubricant or replaced, mechanical seals need replacing couplings must be maintained, and motor and pump shafts must be aligned.
Pump packing: it is one of the biggest problem areas for operators in charge of pump maintenance poor maintenance of pump packing is responsible for more pump damage than any other maintenance item.
Damage caused by packing failure:
Removing old packing: it is time to replace the packing when there is no more adjustment lift in the packing gland and there is too much leakage from the stuffing box. When this occurs, all of the packing rings must be replaced.
Unit - 5
SYSTEM OF MAINTENANCE
Maintenance periodicity
In general practice, there are three types of periodicity
Types of maintenance
Maintenance may be classified into following categories.
Who should do the PM it may be taken care of by production department, maintenance department or a separate division of inspector. However the choice depends on the size, location, machinery etc.
Where to start the PM, one should not apply the PM programme to the entire plant at once rather it should be built up in pieces, when one piece is finished, start the next.
What to inspect in the PM, this programme is very costly and it is not advisable to apply this programme to all the items in a plant. There are certain key items which are more essential for continuing the production that the others, a breakdown of the key items would seriously interrupt production and badly affect production schedule.
What to inspect for, what physical parts of each pieces of equipment needs attention. In this regard, one should make a check list to ensure that no inspection point is missed.
How often to inspect, a decision with regard to the frequency of the inspection is made. From the paste experience, if annual inspection keeps a key item in perfect running condition, one may not think of inspection the same every six months.
Records, it is very necessary to keep records because they are only reliable guides for measuring the effectiveness of PM programme. Good updated record proper filling equipment and adequate clerical help are the backbone of PM programme.
Storage of spare parts.
This repairs, which are carried out at a planned interval under preventive maintenance, can be broadly classified as four categories involving different volume of work and each of which following the other in a sequence.
The repair cycle of a center i.e. C-I1, S1, I2, S2, I3, M1, I4, S3, Is, S4, I6, M2, I7, S5, I8, S6, I9, C, I1. This mean that after a plant interval (say 6 months on 2 shift basis).
After removing the defect the maintenance engineers do not attend the equipment again until another failure or breakdown occurs.
This type of maintenance is quite justified in small presses which are indifferent to the benefits of scheduling techniques. Breakdown maintenance practice is economical for those equipment shoes downtime and repair costs are less this way than with any other type of maintenance.
Typical causes of equipment breakdown.
Disadvantage of breakdown maintenance:
Preventive maintenance function:
Unit - 6
INSTALLATION OF MACHINE
Repair technique: welding and brazing can be very useful in repair work. The former is today more reliable with modern advances in repair technique. Brazing can be useful but its success depends on the skills of the operator and the basic quality of brazing operation cannot be satisfactorily welded, there are cases on record. Where new sections have been welded into gears on cylinder from litho presses and no marks of gear marks has resulted.
Soldering is a quick useful method of making joints in light articles mode from steel, cooper and brass. It should not be used where the joint will be subjected to vibration or heat. At its best solder is only a soft metal with a strength of about 3 tons per square inch so that where much strength is required on alternative from of joint much be used. This alternative is provided in brazing where joining metal employed is brass a harder stronger, and more rigid metal than solder. A new technique is used for repair of damage cylinder and roller is metal spraying.
Tracing faults: when a machine is not functioning correctly, the trouble may be machine fault or a fault in the machine. If the answer does seem to be in some adjustments of the machine whether pt. be a conventional adjustment or not, always follow the rule of altering only one thing at a time. In obstinate cases do not be afraid to reverse the direction of adjustment, after nothing the original point so that if necessary the original setting can be re-obtained.
Returning to the original setting can be important, particularly where other adjustments have to be tried. Do not be in a hurry to alter machine settings unduly but observe the machine and try to locate visually the fault.
Some general advice: your press should always be capable of producing the best result. However, it is essential that the press be accurately set the receive attention in accordance with the instruction. A conscientious operator knows what attention the press requires. Problem can nevertheless arise in one form or another. This may be due to faulty plates, ink or paper, although the most common reason is faulty setting. Where exactly does the faulty lie. The answer to this question must be available as quickly as possible. A systematically arranged faulty tracing schedule has therefore been prepared.
Engineering analysis: it is observed that few equipment require more frequent repairs as compared to others. The following are the main reasons:
The application of a particular type of maintenance system suited to a plant: there are a number of parameters which are taken care of while certain system of maintenance in a plant. Some of important consideration are.
Arrival of new machine or equipment:
On arrival of the machine on the site the packing cases should be checked against the dispatch particulars. The packing of contains parts list, a duplicate of advice note. After unpacking the machine, the packing material should be damaged, because there may be chances that the machine supplied by the manufacturer is not according to the required specification and may be returned back of the supplier.
Different types of lifting devices likes pulley blocks, chain hoists, overhead cranes etc. may be required.
Maintenance schedule: it follows a similar procedure to that outline for production. It is required to know that how long a job will take, when it should be done and if resources are available. It should plan major repairs and overhauls during holidays.
Weekly maintenance schedule of printing press plant
Unit - 7
ELECTRICAL PANEL BOARD CONNECTIONS
Electric motors are used to convert electrical energy into mechanical energy. A motor generally consists of a stator, rotor, end bells and windings.
The rotor has an extending shaft which allows a machine to be coupled to it. Most large motors will be three phase motors rated from 220 or 4160 volts.
Single phase motors: these are normally operated on 110-220 volts AC single phase systems. This requires a special start circuit within the motor to make sure it runs in the right direction.
Single phase power leads will have three wires, like a three-prong extension cord. The third wire is the neutral or ground.
Three phase motors: these are three sets of winding in the motor and three legs of power coming in from the distribution system.
This type of motors are used where loads becomes larger than single phase circuits can handle with three legs to carry power, more amps can be derived to the motor.
These motors are most common types used in water and waste water system.
Air compressor: a machine which provide air at high pressure called air compressor.
An air compressor takes in atmospheric air and compresses it to the desired pressure.
The high pressure is delivered to a storage vessels which is conveyed by a pipe line to a place where high pressure is required.
Application of air compressor:
Cluth: it is a mechanical device which engages and disengages power transmission especially from driving shaft to driven shaft.
Cluches connect and disconnect two rotating shafts (drive shafts or line shafts).
Relay: a relay is an electrically operated switch. Many relays use an electromagnet to mechanically operate a switch, but other operating principles are also used, such as solid-state relays.
Relays are used where it is necessary to control a circuit by a separate low-power signal, or where several circuit must be controlled by one signal.
Limit switch: it is a switch operated by the motion of a machine parts or presence of an object.
It is an electromechanical device that consists of an actuator mechanically linked to a set of contacts.
Unit - 8
SOME PROBLEMS
Cause: pile not at proper height
Remedy: correct adjustment of pile height.
Cause: suckers not performing properly.
Remedy: provide appropriate separation air.
Cause: too much separation air.
Remedy: adjust the sucker properly.
Cause: fault in workmanship
Remedy: correct working of workmanship.
Cause: fault in machine feeder
Remedy: correct adjustment of machine feeder.
Cause: incorrect front & side lays.
Remedy: appropriate positions should be provided for front & side lays.
Cause: fault in material
Remedy: use correct materials.
Cause: ink is more-tacky
Remedy: remove the tackiness.
Cause: non-uniform tension
Remedy: give sufficient quick release to the blanket.
Cause: blanket with insufficient quick release.
Remedy: to set the uniform tension.
A printing defect in offset printing which is caused by light and darks blends in solid and halftone parallel to gripper edge of a machine sheet.