The maintenance work of the offset press can be divided according to the workload.
Minor repair: generally refers to the daily maintenance work, mainly for single replacement, disassemble and install the workload is not large, downtime is short.
In the repair: general guidelines for sexual repairs, the main parts of the offset press to replace or repair, repair time is longer.
Overhaul: Complete and thorough inspection and repair of offset presses, replacement or repair of all parts that exceed wear standards, and longer repair times.
Maintenance basis The maintenance of the offset printing press is a specific analysis of the specific problems of the specific machine, and there must be a certain basis for the development of the repair or overhaul plan.
1. The quality of prints Determines whether major repairs are required through the inspection and analysis of print quality. If there are obvious bars in the printed matter, the outlets are seriously deformed, the overprint errors are relatively large, the hair characters, ghost images, and the writings are imaginary, then the overhaul of the aircraft should be considered.
2. Offset printing machine's use time The offset printing machine inevitably will have the natural wear in the use process, the machine precision and the technical performance will change, as shown in Fig. 1 is one offset printing machine use value change curve chart. It can be seen from the figure that when the use value of an offset press (determined by product quality, output, etc.) is reduced, the machine should be overhauled.
3. Offset Accuracy Index The offset index of an offset press is a comprehensive index that measures the wear of a machine. It inspects some key parts of an offset press, obtains data, and grasps the wear of each component.
T-machine accuracy index;
TP - the actual measured value of the precision index;
Ts-accuracy index of the licensed value;
The number of n-test items.
The calculation results should be assessed as follows:
0.5
Prepare work For machines that need to be repaired or overhauled, in order to shorten the working hours. Costs are minimal, strict plans must be made before repairs, necessary organizational and technical measures are taken, and preparations are made:
(1) Check the relevant drawings and specifications and clarify the structure of the machine and the relationship between the parts.
(2) Prepare a repair schedule.
(3) Prepare repair tools and materials.
(4) Determine the necessary labor organization, equipped with necessary technical personnel and inspectors.
(1) According to the information and practical experience, in the reverse order of assembly, from outside to inside, from ± to below, first disassemble parts or assemblies and then disassemble them into parts.
(2) The parts to be dismantled shall be marked or affixed with a label, in particular, the position where the parts are matched shall be marked and stored in categories, and they shall not be randomly placed to prevent loss.
(3) Make a record. Parts are worn during disassembly. Scraps, relevant technical data and technical requirements, etc. should be recorded one by one so that they can be handled in a timely manner in the maintenance process.
(4) Wash and inspect. The disassembled parts should be cleaned with kerosene as quickly as possible, and the inspection should be carried out after cleaning. First, the appearance inspection should be performed to see if there are cracks, damages, and rust. Pitches, twists, and bends, etc., are checked for geometry and dimensions to measure if the wear of each running part exceeds the requirements.
(5) Replace or repair parts. According to the inspection situation to determine which parts should be repaired or replaced, the following principles should be mastered when repairing or replacing parts:
1 When main parts and minor parts are operated in conjunction, the main parts are generally repaired after wear and the minor parts are replaced.
2 When the parts with long processing cycle and short processing cycle work together, the repair cycle will generally be repaired after the wear and the replacement cycle will be short.
When the 3 large parts and small parts are operated together, after the surface is worn, the large parts are generally repaired and the small parts are replaced.
The disassembly procedure is basically the same as that of domestically-made offset presses. If overhauling is required or the disassembly is required before installation, the disassembly procedures adopted for each print are not the same, but the basic principles are the same. Now take the J2205 offset press as an example to introduce the disassembly steps of the main components:
(1) Remove the shield frame on both sides of the mainboard. Plate roller gear.
(2) Remove the roller gear.
(3) Remove the uniform ink section.
(4) Remove the electrical button box inside the operation panel of the mainboard.
(5) When removing the eccentric sleeves on both sides of the plate cylinder, use a chain to lift one end of the cylinder or use wood. The wooden wedge supports the roller to prevent it from being deformed after it has been removed.
(6) When removing the drum, lift the drum and move the drum to the hole of the wall of the transmission surface so that the axle head of the drum can be removed from the hole of the wall board, and tilt the drum body by 15-25 degrees.
1. Dismounting the impression cylinder After disassembling the plate and the blanket cylinder, the following procedure should be followed if the impression cylinder needs to be disassembled. This method can also be applied to the removal of the transfer device and the delivery roller.
(1) Remove the feed dog and take-up roller. Impression roller drive gear and hub.
(2) Disassemble the sleeves on the both sides of the paper feed roller, delivery roller, and impression cylinder. When removing the sleeve, use wood and wooden wedges to support the above components.
(3) Remove the pull shaft. Paper guide rail fastening screws and other related fasteners.
(4) Remove the main console wall panel.
(5) Hang the impression cylinder.
2. Disassemble the gears and hubs of the second color plate cylinder (1) Remove the second color water-removing and ink-disconnecting rods inside the operation panel wall plate.
(2) Remove the support plate of the printing plate cylinder by the printing plate mechanism.
(3) Remove the axial operation surface of the lower plate cylinder.
(4) Remove the hub and gear of the lower plate cylinder.
3. Removing the impression cylinder pick-up shaft (1) Remove the plug of the large compression spring and remove the compression spring and spring rod.
(2) Disassemble open lever and swing rod.
(3) Remove the bearing housing in the middle of the gripper shaft (remove the fastening screw) and the needle roller bearing.
(4) The gripper shaft is first moved toward the transmission surface, and the gripper shaft end of the operation surface is released from the positioning hole of the shoulder roller of the impression cylinder, and then the axial operation surface of the gripper is moved. Remove the pick roller shaft of the impression cylinder.
4. Remove the paper feed shaft of the transfer unit (1) Remove the large tension springs on both sides and the pull arm of the delivery arm swing arm.
(2) Tap the tapered pin on the shaft and remove the open lever and retaining ring.
(3) The feed shaft swings. When the shaft aligns with the positioning hole on the wall plate (the dedicated hole designed for the removal of the gripper shaft), the feed shaft can be removed from the stack.
The purpose of repairing mechanical parts is to restore the parts' original structure size, matching accuracy and working ability.
1. Roller repair The wear part of the drum is mainly the drum journal. Offset roller journal is a key part, and its fit clearance should not be too large. If the fit clearance exceeds the standard 0.7-0.8mm, it should be repaired. Commonly used methods are insert steel coating, metal spraying and brush plating. If the embossing cylinder prints one size of paper for a long time, a pit will be struck in the cylinder and the repair can be performed by chrome plating and re-leveling. If the surface of the drum is crushed (such as the screw is dropped into the machine), metal spraying may be used and then the flattening method may be used.
2. Bush or eccentric sleeve repair In general, the drum journal and sleeve (or eccentric sleeve) of the steel sleeve wear together, and the steel sleeve wear faster than the journal. If the wear amount of the journal is 0.3-0.4mm, the wear amount of the steel sleeve has generally reached 0.7-0.8mm. At this time, the roller journal and sleeve (or eccentric sleeve) should be repaired. The sleeve and the eccentric sleeve are mainly replaced. If the journal has slight wear, it needs to be flattened. In addition, the sleeve and eccentric sleeve of the transmission surface and the control surface should be repaired at the same time.
3. Restoration of the dental pad After the wear of the receiving pad, the dental pad is generally replaced with a new dental pad. The size of the new dental pad has been modified to be used. Delivery tooth pads generally have to be replaced as a whole. After the replacement, the surface grinder is used to grind the work surface of the tooth pads to ensure that the working surfaces of the tooth pads on the tooth row are on the same straight line.
There are two methods for repairing the tooth decay of the roller cavities: First, the new tooth pads are processed according to a certain size; First, the top surface of the worn tooth pads is polished and then plated with artificial diamond powder.
4. Nylon Roller Repair (1) Re-spray the nylon layer: Remove the worn nylon roller car to the nylon layer, clean it, and then heat and re-spray the nylon layer.
(2) Replaced by plastic: If it is difficult to spray the nylon layer, the car can go to the nylon layer of the roller body and hang a layer of plastic.
5. Repairing the rubber roller If the aging occurs on the surface of the rubber roller, the aging layer can be worn away. The sandpaper can be used to add oil and gasoline to the surface of the roller to remove the aging layer. For severely worn or cracked rubber rollers, the original rubber layer should be removed and the rubber layer re-attached.
Offset presses have adjusted the relative relationship between parts at the factory. Therefore, after the new machine arrives at the printing factory, the installation and adjustment tasks only adjust the part of the connection relationship. It is not necessary to adjust the parts that have already been positioned. . After the overhaul, the installation and positioning of the machine and the installation and adjustment of the new machine are very different. The difficulty of the latter is quite large. Therefore, in the process of disassembling the machine in some respects, records are made and used for related parts. It is very important to mark with a needle. Some parts do require some theoretical knowledge and rich practical experience to complete the repair installation