Oil circuit maintenance for offset press machine maintenance
6.2 Oil circuit maintenance
Oil circuit is one of the most important contents in machine maintenance. The role of the oil circuit is:
1. Minimize the area where two rigid surfaces are in direct contact, thereby reducing wear on both surfaces. Due to the reduced wear and tear, the accuracy of the machine is less impaired and the energy consumption is greatly reduced.
2. Due to the fluidity of the oil circuit, the heat generated by the machine parts is taken away by the oil, so that the machine parts always work within the normal temperature (will not cause thermal deformation) to ensure the transmission accuracy of the machine.
3. Anti-corrosion effect. Because there is always oil on the surface of the component, the air is separated from the surface of the component to prevent the oxidation reaction. Especially high-speed moving parts have higher requirements for this, because the surface temperature is high, and oxidation reactions are more likely to occur.
4. Sealing effect. Due to machining errors on the part surface, there is always a gap between the two surfaces. If lubricating oil is present on both surfaces, the two surfaces can form a void-free state.
5. Increase the contact area between components, so that the machine runs smoothly. There are always machining errors on the surface of the parts, so the contact area between the parts cannot reach 100%. The higher the surface roughness, the smaller the contact area and the worse the running stability. If there is lubricating oil between the two surfaces, the contact area of ​​the two surfaces is greatly increased, so that the machine operates stably.
The role of the oil circuit can be seen from its role. Oil is like human blood, and a machine without oil is as unimaginable as a person without blood.
6.2.1 Working principle of lubricating oil
Why does oil play the above role? Let's analyze its working principle. As shown in Figure 6.l, when the upper object moves relative to the lower object, first, the peaks on both sides are worn away, then the contact area of ​​the two surfaces. bigger. During further relative movement, the heat generated by the two surfaces increases, and the heat dissipation rate slows down, thereby increasing the temperature of the contact surface and increasing the fluidity of the metal, causing the two sides to fuse together. At this time, if the relative movement between the two sides continues, more power is needed, and thus more heat is generated, the temperature further increases, and the metal combined together continues to increase. This reciprocates until the contact surfaces of the two sides form a whole, and the relative motion cannot proceed.
(Figure 6.1)
After adding lubricant to the contact surface, the situation will be greatly improved, as shown in Figure 6.2.
(Figure 6.2)
During relative movement, the peaks on both sides of the contact surface are worn away, resulting in the situation shown in Figure II. When the relative movement continues, due to the presence of lubricating oil. The upper and lower sides are not in contact, so that the wear of the two surfaces is avoided, and the transmission accuracy is guaranteed. The friction of the contact surface is mostly carried out with oil as the medium, and the heat generated by the friction is drawn away. The role of oil here can be summarized into two points:
1. Isolate the two contact surfaces so that the two contact surfaces are in indirect contact;
2. Heat dissipation to keep the temperature of the contact surface to a minimum.
Although it is necessary to add oil in the contact surface, there is generally no need to leave a gap for lubricating oil, and the processing error of the contact surface is enough to ensure the formation of the oil film.
6.2.2 Composition of oil circuit
Lubricating oil roads are generally divided into two types: one is circulating; the other is non-circulating. Circulating oil circuit means that the lubricating oil (except for the loss) entering the contact surface is returned to the oil tank. This oil circuit is suitable for lubricating parts with large oil consumption. The non-circulating oil circuit means that the oil entering the contact surface is completely lost and no longer returns to the oil tank. Components with low fuel consumption are suitable for this type of lubricant circuit.
Refueling of the oil circuit is divided into manual and automatic. Manual refueling is mainly used in places where it is difficult to pass the oil passage or it is not necessary to refuel for a long time. This oil circuit can only be non-circulating. Due to the large number of lubricating parts on the machine, manual refueling cannot guarantee the normal operation of the machine. Such oil levels must be automatically refueled. Both circulating and non-circulating oil circuits can be refueled in this way. The development of the machine's oil circuit is close to fully automatic refueling, which can ensure the safe and stable operation of the machine.
The oil circuit for automatic refueling can be drawn with the following transmission keys:
Fuel tank-front filter-oil pump-rear filter-oil pipe â… -sub-throttle-oil pipe â…¡-oil service
The oil tank is mainly used to hold oil. The oil tank is generally equipped with an oil mark, which can be used to display the level of the oil level; the front filter is mainly used to filter the impurities in the oil tank to prevent these impurities from entering the oil pump; That is, the oil is changed from low pressure to high pressure and sent to the required place. Pseudo-pumps are generally used in printing machines. The gear pump occupies a small space, is simple and reliable; the rear filter is mainly used for iron scraps in the transitional gas system to prevent it from entering the relative motion contact surface of people.
The tuber is the channel that connects the fuel divider and the post-scanner. This is because there are so many refueling parts. It is impossible to connect each oil eye with the oil pipe and the oil pump.
The oil pipe â…¡ is used to connect the channel between the oil dividing valve and the oil eye. The above automatic refueling oil circuit is actually a non-circulating oil circuit, which is slightly improved. It can be changed to a circulating oil circuit. As follows;
Fuel supply tank-front filter-oil pump-rear filter-oil pipe â… -oil eye-oil return pipe â… -oil return tank-oil return pipe â…¡-oil supply tank [next]
6.2.3 Function and maintenance analysis of oil circuit components
The oil circuit is the lifeblood of the machine, so it must be in a normal working state at all times, that is to say the entire oil circuit must be unobstructed. In order to keep the oil passage smooth, every component on the oil passage must be in a normal working state. The following takes the oil circuit wiring diagram as an example to analyze the maintenance content of each component in detail.
1. Fuel supply tank. When the fuel supply tank works normally, the fuel tank must contain enough oil. Whether the amount of oil meets the requirements can be detected by the oil mark, and some machine oil palms can show the amount of oil in the oil tank in both dynamic and static states. It should be noted that when the oil mark of the fuel tank fails, you can only open the cover of the oil tank to observe the amount of oil or estimate the amount of oil in the oil tank through the oil mark of other parts (or the amount of oil in the lubrication part). Some oil tanks with poor sealing are prone to oil leakage, so you should always check the amount of oil in the oil tank. The oil in the oil tank should be kept clean. It is best to filter the oil (with gauze) when changing the oil.
2. Front filter. The front filter is used to filter impurities in the fuel tank. After a long time, the impurities in the oil tank may block the filter hole, so that the oil cannot enter, so that the lubricating part can not get normal lubricating oil. If you find this filter dirty, you should clean it in time, but you should be careful not to break it.
3. Oil pump. The oil pump is to make the oil get energy, so that it can flow to the place where the fuel is needed. Because most oil pumps use gear pumps. From the perspective of transmission, such pumps will generally not stop. But should pay attention to the leakage of this pump. Especially the greater the pressure, the more serious the leakage. Another is to prevent impurities from entering the pump and causing gear wear.
4. Rear filter. The rear filter is used to filter the gold in the oil pump. Among them, iron filings are the main components of impurities. This filter must be absolutely reliable because the oil that goes out is used for lubrication. Therefore, the post filter generally uses ultra-fine filters. Because the filter hole pile of this filter is small, it is easy to block, so it must be cleaned frequently. Otherwise, once blocked, it will make subsequent oil supply difficult.
5. Oil supply pipe â… . The oil supply pipe I mainly transfers the oil to the oil distribution valve. The requirement is to allow oil to flow smoothly, so it should not be bent too much, and should not be given to moving parts. When the oil pipe is not smooth, it is better to replace it with a new pipe. For emergency, steel wire can also be inserted to make it smooth.
6. Oil separator valve. The oil separation valve is used to distribute the amount of lubricating oil, because the oil consumption of each oil level is not exactly the same. In addition to controlling the oil distribution, the oil separation valve should also be able to control the pressure. At present, the oil separation valve used in domestic machines can only control the amount of oil, while the oil separation valve used in most imported machines can also control the pressure. The oil separation amount of the oil separation valve should be adjusted according to the requirements of the berth, and generally should not be adjusted at will. The oil separator valve is not working properly and can be opened for cleaning. The production of oil separation valve has been standardized and can be purchased according to requirements.
7. Oil supply pipe â…¡. The oil supply pipe II is responsible for sending the oil in the distribution valve to the parts to be lubricated. Some of these oil supply pipes are connected to the oil eye, and the oil is directly injected into the oil eye; some are the end of the oil nozzle is located above the lubrication part, and the oil drops through the oil nozzle into the part to be lubricated. For the oil pipe directly connected to the oil eye, if the oil eye is fixed, connect the oil tube; if the oil eye is not fixed, the oil pipe should move with the movement of the oil eye. In this case, flexible tubing should be selected, and oil-based tubing should be selected for its pressure resistance. If the pressure resistance is not enough, it will rupture during work, which will destroy the lubrication conditions of the part, and the consequences will be unimaginable. For the oil pipe that is not directly connected to the oil eye, the position of the oil pipe must be opposite to the oil eye (or lubricated part). If it is not opposite, the lubrication of this part cannot be carried out, especially this should be paid attention to during maintenance, and the oil pipe should not be arbitrarily moved. The maintenance of the oil supply pipe II itself is the same as that of the oil supply pipe I.
8. Oil eyes. Oil service is the best way to pass oil to the lubricated part. The oil eye generally consists of two parts: the oil injection hole and the oil groove. Oil flows to the oil groove through the oil hole, and then directly injected into the lubricating part through the oil groove. Therefore, whether the oil hole is unblocked and whether the oil groove is properly opened directly affects the quality of the lubrication effect. Unfiltered oil may block the oil holes. In addition, iron filings in the lubrication area may also damage the lubrication efficiency of the oil groove. When disassembling and overhauling the machine, clean the oil holes and impurities in the oil tank. There are oil eyes for the lubrication of shafts, but there is no oil service like gears and cams. The oil drops directly to the parts to be lubricated after passing through the oil supply pipe area. At this time, it should be noted that the oil pipe cannot deviate from the lubricated part, otherwise it will cause a decrease in accuracy.
9. Oil return pipe â… . Oil return pipe â… generally consists of two parts: oil return hole and oil pipe. The oil return hole and the oil pipe must be unblocked, otherwise the oil in the lubricating part will not leak anywhere, and the subsequent lubricating oil will be continuously added, which will cause the oil pressure to rise sharply at this place. Start leaking out through the sealing ring. In addition, impurities in the lubricated parts cannot leak out, which makes lubrication difficult. In this case, replacing the sealing ring is useless, and it is necessary to find a way to make the return pipe I unblocked. This problem does not exist in oil circuits without oil eyes.
10. Return to the tank. The oil return tank is used to hold the lubricating oil flowing out from the lubricating part. On small machines, the supply tank and return tank are shared. On large machines, since some lubrication parts are too far away from the oil supply tank, a special oil return tank is required. The oil return tank can also play the role of storing lubricating oil. Because a large amount of lubricating oil is required when lubricating the type machine. If you only rely on the fuel tank to supply fuel, the fuel tank must be quite large, which makes the machine look awkward. Moreover, it is difficult to return the oil from a distant place, which may cause oil leakage.
11. Return to the oil pipe â…¡. The oil return pipe â…¡ is used to connect the oil return tank and the oil supply tank, so that the oil in the oil return tank can quickly return to the oil supply tank, so that these oils re-enter the lubricating oil circuit. If the oil return pipe â…¡ is not smooth, the oil in the oil supply tank is getting less and less, and the lubrication cannot be maintained normally. As long as it is circulating lubrication, the supply tank and return tank are always connected.
6.2.4 Lubrication details
The purpose of lubrication is to reduce harmful friction. The harmful friction mentioned here means that not all parts of the friction must be lubricated, and some parts of the friction, such as pulleys, are beneficial and therefore cannot be lubricated. To have friction, there must be relative motion (or relative motion trend), so only the contact surfaces of relative motion need to be lubricated. This is a basic criterion for designing a lubricating oil circuit. From the perspective of lubrication, the simpler the oil circuit, the better, the fewer lubrication parts, the better, and the more convenient the lubrication. This requires the machine to be in contact with relatively few moving parts, the better, and the more obvious the lubrication parts. This is another basic criterion for designing the oil circuit.
Due to the complicated structure of the printing machine and the relatively large number of moving parts, this has brought great difficulties to the design of the oil circuit. It is almost impossible to equip every lubricating part with an oil pipe, so two lubrication methods are generally used on printing machines: one is positioning lubrication and the other is rain-type lubrication. Positioned lubrication is to add lubricating oil directly to the lubricating part. This lubrication is suitable for fixed rotary shafts. Rain-lubricated lubricating oil flows from high places to the parts to be lubricated like rain. This lubrication method has to take into account many lubrication parts, and the design has to use a larger amount of oil, which increases the possibility of oil leakage.
The oil pressure required for positioning lubrication is larger, the higher the machine speed, the greater the oil pressure required. Therefore, the positioning lubricating oil pipes are required to have high compressive strength. Rain-type lubrication does not require large oil pressure, as long as the oil in the oil tank can be added to the upper end of the required lubrication parts. But the speed of the machine changes, and the amount of oil used also changes accordingly. The above is the third basic principle to be followed when designing an oil circuit.
Is the more lubricating oil the better? Some masters always think that the more lubricating oil, the better. When refueling, always try your best to add it. I wish to put the lubricated part in the oil tank, and think that the best lubricating effect is. In fact, this is inappropriate and unnecessary. Lubricating oil has a certain viscosity, so it will also cause a certain energy consumption, so it should not be too much.
There are several ways to lose lubricating oil: One is deterioration. The lubricating oil in the lubricating part will produce a chemical reaction under high temperature, and lose the performance of the oil itself. The second is leakage. Although the seal ring is used in the lubrication area, there is always more or less oil seeping from the edge of the seal ring. Due to the loss of lubricating oil, the oil in the lubrication area needs to be continually replenished. Many machines are equipped with a delay device on the oil line, which can ensure regular oiling.
Selection of lubricating oil. The type of engine oil used for different machines is different. For lubricating parts at high temperature, lubricating oil with high viscosity is required, while for low temperature, lubricating oil with low viscosity is required. This is because the higher the temperature, the lower the viscosity of the lubricating oil; the lower the temperature, the higher the viscosity of the lubricating oil. The oil in the lubricated part must have a certain viscosity, so that it can adhere to the contact surface. Taking the machine as an example, if you choose No. 40 oil in winter, you should choose No. 50 oil in summer. For the air pump, the viscosity of the oil used should be greater because it operates at a high temperature.
6.2.5 Oil lubrication and grease lubrication
Oil lubrication and expansion lubrication are the two most widely used lubrication methods on the machine, but each has its own emphasis in actual use. Because the fluidity of oil is large and can be replenished continuously, the heat generated by friction can be diffused in time, so oil lubrication is suitable for high-speed, heavy-duty mechanical lubrication. The fluidity of grease is poor, the heat generated by friction is completely absorbed, and cannot be diffused out, so grease lubrication is suitable for the lubrication of low-speed, light-load machinery. Grease lubrication is manual lubrication. Because the fluidity of grease increases after heat absorption, it is easy to overflow from the lubricated part. However, it cannot be continuously replenished by itself, so it is necessary to regularly check the condition of expansion and lubrication.
All opening and closing tooth cams do not need lubrication, and all springs need lubrication.
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