Regarding the daily maintenance of the sand making machine, we have also shared it before. There are many details of the daily operation, which may have been forgotten by many friends. Today, the small mine will be introduced in detail. What are the daily maintenance tips for sand making machines? (1) First of all, regular inspection and maintenance are required Regular inspection and maintenance are one of the basic tasks of the daily operation of the sand making machine, and it plays a major and important role in ensuring the normal production and operation of the sand making machine. Regarding the inspection items, mainly include: the internal wear of the sand making machine, the wear degree of the center feed pipe, the cone cap, the upper and lower flow channel lining plates of the impeller, the circumferential guard plate, and the wear-resistant block, etc. If these parts are worn, we need to replace or repair them in time. (2) Strictly follow the operating procedures Strictly follow the rules of the operating procedures to effectively avoid equipment and personal accidents caused by improper operation or negligence during operation. (3) Select special lubricating oil and lubricate regularly The lubrication of sand making machine is very important, we need to choose special lubricating oil and replace lubricating oil regularly. When the machine works for 2,000 hours, we have to open the main shaft assembly to clean the bearings, and when the machine works for 7,200 hours, replace the new bearings. (4) The tension of the V-belt is properly adjusted to ensure uniform stress The tension force of the transmission triangle belt should be adjusted appropriately to ensure that the triangle belt is evenly stressed. When driven by two motors, the triangle tapes on both sides should be selected in groups, so that the lengths of each group are as different as possible. The current difference between the two motors should be adjusted so that the current difference between the two motors does not exceed 15A. There are actually a lot of daily maintenance of the sand making machine. For example, it is necessary to stop the machine before maintenance. During the normal operation of the sand making machine, the operator should stay away from the equipment. However, the above are some major direction points. If we do these items well, the daily production efficiency will not be greatly affected.
1. Abnormal vibration of sand making machine If the material entering the sand making machine is too large to cause abnormal vibration, the feeding particle size of the stone can be checked. When the impeller of the sand making machine wears unevenly, it will cause abnormal vibration of the machine. At this time, the damage of the impeller and the alloy hammer head can be checked. If there is any damage, it should be repaired and replaced immediately if necessary. The imbalance of the impeller of the sand making machine causes abnormal vibration, and the balance of the sand making machine needs to be adjusted. Abnormal vibration caused by improper foundation of sand making machine, check whether the anchor bolts are loose, and fix it immediately. 2. The bearing of the sand making machine heats up The lack of oil and too much oil in the bearing of the sand making machine will cause the bearing to heat up. You can check the oil level when it is hot. Damage to the bearing of the sand making machine will also cause the bearing to heat up, so it is necessary to check and replace the bearing in time. If the upper cover of the bearing body of the sand making machine is too tight, the bolts should be adjusted to properly adjust the looseness. 3. Sand making machine belt turning The belt of the sand making machine is worn and can be replaced with a new one. There may be a problem with the belt installation and the pulleys need to be adjusted in the same plane. Check the quality of the V-belt of the sand making machine to see if there is any problem with the quality. 4. The discharge particle size of the sand making machine is too large Check the damage of the alloy hammer head and the side impact plate of the sand making machine, and the alloy hammer head and the side impact plate can be repaired and used, and can be removed and replaced if necessary. Check the particle size of the material of the sand making machine. The material is one of the key factors affecting the output of the sand making machine. If the particle size is too large, the output particle size of the sand making machine will be too large. 5. The impeller is stuck When the inside of the crusher enters metal and other hard objects, the impeller of the sand making machine may be stuck, causing the equipment to fail to work. Therefore, the hardness of the material should be strictly controlled, and the entry of unbreakable objects is prohibited. 6. The bearing is locked or the spindle is broken If it is caused by the fracture of the spindle, it is necessary to repair or replace the worn spindle. If it is caused by the locking of the bearing, it is necessary to find out the cause of the locking, install the bearing correctly, ensure that the bearing has a certain working clearance, and do a good job of lubricating the bearing, otherwise the problem cannot be fundamentally solved. 7. There is a problem with the device connection line If the connecting line is broken or has poor contact, the sand making machine will also suddenly stop, especially when there is no sound without warning, it is likely that the connecting line has a problem.
To ensure the efficient production of the sand making machine, we also need to pay attention to: 1. The sand making machine should be suspended regularly to extend its service life; shut down regularly to check the internal wear of the machine, especially the center feed pipe, cone cap, impeller upper and lower runner linings, circumferential guard plates, wear-resistant blocks, etc. For the degree of wear and tear of the wearing parts, timely replace or repair the parts with serious wear and tear. In particular, ensure that the wearing parts are replaced in time. At the same time, pay attention to the weight, model, and size of the replacement parts must be replaced according to the original part parameters. 2. As we all know, the shaft of the sand making equipment bears the full load of the negative machine. Regular lubrication directly affects the service life and operating speed of the equipment. Therefore, regular lubrication is required, and the injected lubricating oil must be clean, the seal must be good, and the instructions must be strictly followed. Standards for the use of lubricants. Appropriate amount of lubricant should be added when the sand making machine runs for 400 hours, and the bearings should be cleaned when running for 2000 hours. New bearings must be replaced after running for 7200 hours to ensure the normal operation of the equipment. The staff should also always pay attention to whether the various parts of the equipment are working normally. When the bearing oil temperature rises, there is a huge impact, etc., they should stop immediately to check the cause and eliminate it. 3. The sand making machine is a high-speed equipment, so during the equipment work, the staff should pay special attention to personal safety, stay away from the equipment, and must not open for observation to avoid dangerous accidents. If it needs to be repaired on the machine, it must be operated after the power is cut off. 4. In the event of a serious failure, it is recommended to ask professional maintenance personnel to repair it, and do not disassemble the core components without the permission of the manufacturer. 5. Maintenance of impeller. The impeller is one of the important parts of the sand making machine, and it is also the most vulnerable part. Protecting the impeller and improving its stability can not only effectively improve the working efficiency of the sand making machine, but also extend the service life of the sand making machine. The direction of rotation of the impeller device should be counterclockwise from the feed port, otherwise the motor wiring position must be adjusted; the feed should be uniform and continuous, and the size of the river pebbles should be strictly in accordance with the equipment regulations. Oversized river pebbles will cause the impeller to be damaged. Unbalance, wear the impeller; stop feeding when shutting down, otherwise it will cause the impeller to be crushed and cause damage to the impeller; it is also necessary to check the wear of the impeller device regularly, and replace the worn impeller in time to ensure the normal operation of production. 6. Maintenance of the rotor. There are several effective methods to extend the life of the rotor bearing of the sand making machine: Correctly choose the type of rotor bearing: Because the double row radial spherical roller bearing has the advantages of strong load-bearing capacity and good self-aligning performance, this type of bearing is often used as the rotor bearing. Improve the balance accuracy of the rotor body: The rotor of the sand making machine is of large mass and high speed, and the casting deviation of the rotor body and the mass deviation caused by the installation of the hammer will cause unbalanced centrifugal force when the rotor rotates. This centrifugal force causes the machine to generate forced vibrations, causing damage to bearings and other mechanical parts. Therefore, the rotor of the crusher must undergo a balance test. Choose a reasonable matching relationship: the rotor bearing of the sand making machine is mainly subjected to the impact load when it is working. The load on the rolling element is different. The rolling element under the line of the impact load is the most stressed, the inner and outer rings The raceway also receives the greatest force when it is in contact with the rolling elements here. It is recommended to use F8 or E8 for the cooperation between the outer ring and the bearing seat. Improve the bearing force: the impact load acting on the bearing depends on the support flexibility of the impulse bearing seat acting on the rotor. Increasing the support flexibility of the bearing seat will reduce the impact load acting on the bearing. For this reason, we add a rubber plate of appropriate thickness between the bearing seat and the support frame to improve the support flexibility of the bearing seat. Due to the addition of the rubber plate, the support flexibility is increased, which absorbs a part of the vibration energy, improves the force condition of the bearing, and achieves the purpose of extending the service life. At present, the price of sand and gravel is so high, improving the efficiency of the sand making machine will help increase corporate profits!
Sand making machines are widely used with the development of the global sand and gravel business. The equipment is generally used to crush harder materials. However, the friction between the equipment and the materials cannot be avoided in this process. It may cause scratches inside the device. Therefore, when the equipment is in operation, the staff need to pay attention to whether there are quality problems such as failures, because this quality problem also affects its service life. In order to extend the life of the sand making machine, we need to do the following: 1. In order to prolong the life of the sand making machine, it is necessary to improve its quality. This makes it necessary to choose a manufacturer with good quality and high reputation when buying a sand making machine. The pre-sales, sales and after-sales of their equipment are somewhat strict. The running process. 2. The equipment needs to be checked during the operation of the sand making machine to ensure that it can run smoothly during our use. In addition, it needs to be maintained before and after use. The equipment is not cheap and if you want it to play its due effect and function, this maintenance and maintenance link is also essential. 3. During the operation of the sand making machine, professional operators are required to perform operations. These personnel need to undergo rigorous and professional training and have precise operations, etc., so as to ensure that there is a sudden occurrence of the equipment during use. The problem can be found and solved in time, and it is more convenient to use at the same time. For the sand making machine, if it wants to realize its value and achieve the goal of production to a greater extent, it is also more important to extend the service life. In addition to the quality of the equipment, the life expectancy is also an important issue at the time of purchase.
For vertical shaft impact breaking, whether it is “stone hitting stone” or “stone hitting iron”, the movement and force conditions of the material in the rotor are the same: the material enters from the center of the rotor, and passes through the distribution plate, guide plate, throwing head, etc. Throw it into the crushing cavity. That is to say, these parts in the rotor are in direct contact with the material and are easy to wear, so their wear resistance is directly related to the replacement cost and operating efficiency. In order to improve the wear resistance, the material of the wear-resistant parts must be selected first. Wear-resistant material series The series of wear-resistant materials currently in common use in my country are: (1) High manganese steel series: such as high manganese steel (ZGMn13), high manganese alloy (ZGMn13Cr2MoRe), super high manganese alloy (ZGMn18Cr2MoRe), etc.; (2) Anti-wear high chromium cast iron series: such as high, medium and low chromium alloy cast iron (such as Cr15MoZnCu); (3) Wear-resistant alloy steel series: such as medium, low and high carbon multi-element alloys (such as ZG40SiMnCrMo and ZG35Cr2MoNiRe); (4) Ao Bei Ductile Iron (ADI) series; (5) Various composite or gradient materials and cemented carbide materials: such as chromium carbide composite materials (Cr2C3+Q235), high-energy ion implantation tungsten carbide materials (WCSP), high toughness cemented carbide (YK25.6), etc.; (6) Various non-metallic wear-resistant materials: such as polymer ceramic composite materials, silicon nitride (Si3N4), toughened zirconia (Y203+ZrO2), toughened aluminum oxide (Al2O3/ZrO2), etc. Below we take the sand making machine as an example to introduce the material selection of the material distribution plate, the throwing head, the guide plate and the anvil in the core part of the rotor. 1. Distribution tray When the material enters the high-speed rotating rotor and contacts with the distribution plate, it rotates with the rotor. Under the action of centrifugal force, it moves from the center of the distribution plate (rotor) to the outer end of the channel (throwing port). In this process, the distribution plate bears the vertical impact load and the horizontal stone acceleration load at the same time, and the outer edge of the distribution plate wears more severely than the center part. Therefore, the material of the distribution tray must have a certain degree of toughness to overcome vertical impact; it must have a certain degree of hardness and be able to withstand horizontal loads. In summary, the distribution tray should be selected from medium and low-carbon multi-element alloy steels (such as ZG40SiMnCrMo and ZG35Cr2MoNiRe). 2. Throwing head The movement of the stone in the rotor: the horizontal speed of the stone when it enters the contact point of the distribution plate is zero, and it rapidly accelerates the horizontal movement in the direction of the throwing head (outer edge of the rotor). The speed of the stone at the throwing head can be determined according to kinematics, as shown in the figure below. The throwing head has to withstand strong impact and high-speed punching (sliding friction). Therefore, the material of the throwing head should be selected from high-manganese alloy steel series wear-resistant materials (such as ZGMn13Cr2MoRe), or ultra-high manganese alloy steel (such as ZGMn18Cr2MoRe). When the high manganese alloy steel is subjected to severe impact, the surface hardens rapidly, while the core still maintains extremely strong toughness. The outer hard and inner toughness are both wear-resistant and impact-resistant. The heavier the surface is impacted, the more the surface hardens and the wear-resistant The better the performance. 3. Guide plate In the crushing process, the guide plate mainly bears the gravity and sliding friction of the stone. Therefore, the wear of the guide plate is mainly high-speed scouring. Optional wear-resistant chromium cast iron series materials (such as Cr15MoZnCu). 4. Iron drill In the vertical shaft impact crusher of the “stone hitting iron” type, the abrasion of the iron drill is very high. In order to obtain higher kinetic energy conversion, the facing surface of the iron drill is installed on the front of the material. The material hits the iron drill close to the vertical, and the iron drill bears severe impact load. According to the characteristics of wear-resistant materials, the hardness of high manganese steel (such as ZGMn13) is higher than HB550 when subjected to severe impact, while the core hardness is lower than HB170-230, and still maintains extremely strong toughness. Therefore, high manganese steel is an ideal material for iron drills. The wear parts of the vertical shaft impact crusher (except the iron drill) are small in size, small in size, and light in weight. In order to reduce production costs, some parts suppliers often use the same material distribution plate, guide plate, and ejector head body. A kind of wear-resistant material casting, blind pursuit of hardness, the effect is not ideal, resulting in a substantial increase in cost and waste, users should pay more attention when purchasing accessories.
As a professional sand making equipment, the vertical shaft impact crusher (sand making machine) has a wide range of market demands, but the uneven product quality makes the price of the equipment vary, even several times. So why is the price difference so big? There are many reasons, and the details are the key! 1. The design difference of the feed hopper The hopper on the left adopts the welding hemming process, and the hopper on the right adopts the stamping process, which is formed at one time. The latter has a higher technical level and is more durable, and the price will increase accordingly. 2. The difference between bulk cone or bulk tray On the left is the bulk material cone, and on the right is the bulk material tray. The latter can quickly realize the conversion between center feeding and waterfall feeding, reducing downtime adjustment time and improving efficiency. The height of the two can be adjusted to affect the feeding method. Take the bulk material cone as an example: High-less material in the center, more material in the waterfall; Low-the center feed is more, the waterfall feed is less, In actual production, most users use 70% central feed, 30% waterfall feed, or complete central feed. 3. The difference in the structure of the throwing head The sand making machine throwing heads on the market have two structures, one is integrated (as shown on the left), the other is combined up and down (as shown on the right), and the latter is a combination of two large and small throwing heads. , Only need to replace the worn out throwing head part, effectively prevent it from damaging the vertical plate after it is worn out, and can reduce the use cost by more than 30%. 4. The difference in the structure of the peripheral guard plate The peripheral guard plate composed of the upper and lower two parts can be turned up and down after partial wear, which improves the material utilization rate, prolongs the service life by more than 48%, and saves the cost of parts. 5. The difference in the shape of the impact block The impact block of the sand making machine has two types: a square structure and a diamond structure. The latter is more popular with users, because the diamond-shaped combined impact block can avoid material impact damage to the vertical board. It can also be used in turns while improving its own wear resistance. , Which not only improves the utilization rate of materials, but also effectively protects the life of the inner peripheral guard plate of the sand making machine. 6. Design differences of crushing cavity The high-quality sand making machine has the best launch port and smooth internal curve design, which reduces the flow resistance of the material, greatly improves the passing capacity of the material, and thereby improves the production efficiency of sand making. In addition, the rotor is an important crushing component of the sand making machine, and its design affects the amount of sand and the type of sand and gravel. The deep cavity rotor greatly improves the ability to handle materials. 7. Equipment material, configuration and process differences For example, the key parts of the machine are made of first-class alloy materials, the bearings are selected from international leading brands such as Japan, Sweden, and the United States, equipped with high-protection motors, imported from Japan with hydraulic cover opening devices, and the world’s advanced light oil anti-leakage devices are used. The frame made by steel plate bending and hot rivet technology, after quenching, the complex spindle processing technology is annealed… The material and technology of the equipment affect the quality of the product and also affect the price of the product.
Good equipment maintenance is the basis to ensure the efficient production and operation of machinery, especially in the severe winter, when the cold current continues to hit, it is very important to do a good job in the maintenance of machinery. Taking the commonly used sand making equipment as an example, since most of the sand making machines are used in harsh outdoor production operations, it is more necessary for users to master certain winter sand making machine maintenance knowledge. Based on this, Fangchi will share some key points of winter sand making machine maintenance from the following points. 1. Pay attention to lubrication No matter in any season, the lubrication of the parts of the sand making machine cannot be relaxed, and a suitable lubricant should be selected. However, it should be noted here that it is recommended to use lubricating oils with high thermal stability and oxidation resistance in winter. Due to the harsh working environment of the sand making machine, dust, coal powder, etc., the mandatory selection of universal lubricants will not only fail to achieve the lubrication effect, but will also increase the damage to the equipment. In addition, due to the relatively dry winter, in order to prevent hidden dangers such as fires, the selected lubricant must also have a certain degree of flame retardancy. Therefore, it is recommended to use anti-rust, anti-corrosion, and anti-combustible lubricants. Second, do a good job in the insulation of sand making equipment In the production process of the wet sand production line, a ground pump device is usually installed, and the sand making equipment must follow the principles of short circuit, less bending, and tight joints. In its layout, in order to prevent the pipeline from being difficult to dredge due to icing, in addition, the exposed pump pipe must be insulated. For example, rubber and plastic insulating materials can be used to wrap them to reduce the probability of protruding events such as pump tube rupture due to overcooling, and to help sand making machine equipment to better produce and operate. Three, need to be equipped with professional operators During the operation of the sand making machine, the operator is required to have a professional operation method. Therefore, the operator must learn some knowledge about the construction operation of the sand making machine in winter to ensure the smooth progress of the winter construction. The above is a brief description of the three main points of the winter sand making machine maintenance. Winter is coming, in order to avoid reducing the production efficiency of the sand making machine, it is very important to do a good job in the maintenance of the sand making machine.
Nowadays, in order to protect the environment, private sand mining is prohibited in various places. As a concrete ingredient in the construction industry, sand and gravel consume a lot of resources, and natural sand resources are becoming less and less, forming a seller’s market in short supply. In addition, there are countless construction projects at home and abroad every year, natural sand is scarce, and the price of machine-made sand is rising rapidly. Heavy industrial equipment for manufacturing sand and gravel ushered in the spring of the market, and demand soared. However, in the production process of the sand making machine, a certain decibel noise will inevitably be generated, which will not only pollute the environment, but also affect the physical and mental health and work progress of the staff. So how to find a way to create a noise for the workers What about relatively harmonious and quiet work? Next, Zhongmei Tongda will take everyone to analyze and solve the problem of noise reduction from the following aspects. 1. Noise reduction at the target For the protection of operators, a rotation system is adopted to reduce the working time of workers entering the noise area. Second, the propagation path noise reduction By adopting the method of adding barriers, it can hinder the spread of noise to a certain extent or rely on natural terrain, such as hills, woods, and tall buildings. In the overall planning of the sand making machine, the equipment can be placed away from the office area, or concentrated together for easy operation, so that the purpose of reducing noise can be achieved. 3. Noise reduction at the source The production process of the sand making machine equipment was transformed and upgraded and low-noise equipment was selected. After the test, the equipment of Youzhong Machinery has higher output and lower energy consumption than the same type of products in the same industry after the upgrade, and it is running at the same time During the process, the noise is also very low.
Today’s sand and gravel plants are inseparable from this demand for environmental protection. In the environmentally friendly production process, not only must be satisfied from the production process, but also from the equipment configuration and the equipment itself. As a common equipment for sand and gravel production, the environmental protection and energy saving of sand making machines are also the focus of our concern. So which kind of sand making machine is environmentally friendly and energy-saving? Today, Xiao Mine will introduce to everyone. 1. What are the types of sand making machines? Common sand making machines on the market mainly include: hammer sand making machine, pair-roll sand making machine, vertical impact crusher, mobile sand making machine, hydraulic open-box sand making machine, impact sand making machine, Rod mill type sand making machine, etc. Impact sand making machine 2. Which kind of sand making machine is energy-saving and environmentally friendly? In terms of energy saving and environmental protection, the impact crusher is superior. Why do you say this way? Here are some of its specialties: 1. There are two modes of sand making and stone shaping The impact crushing cavity can realize the mutual conversion of the two crushing modes of stone-on-rock and stone-on-iron. 2. Intelligently controlled thin oil lubrication system Changing the traditional manual lubrication method, the lubrication and temperature are controlled by PLC and intelligent instruments. 3. Convenient maintenance The automatic self-lifting boom facilitates the maintenance of the impeller and the bearing barrel. At the same time, hydraulic jacks are used to lift and feed materials, which is very convenient for maintenance. 4. Low cost of use The impact crushing technology is relatively advanced, which can reduce wear resistance during the processing process, the relatively long service life of the wearing parts, and the overall use cost of the equipment is low. 5. Good quality The impact-breaking machine adopts casting material, the transmission part adopts a special sealing structure, and the bearing adopts imported material. The sealing and transmission performance of the whole equipment is relatively good. 6. Convenient maintenance Equipped with a lifting device, the equipment can be overhauled and maintained at any time. The lower part of the machine body adopts a structural design, which can prevent the material from blocking the lower part due to excessive water content. Energy saving and environmental protection generally involve the process, material, structure and other aspects of the equipment, which means that a good sand making machine can meet our needs for energy saving and environmental protection.
The sand making machine is an important equipment in the sand making process. It consists of a hopper, a distributor, a crushing cavity, an impeller body, a main shaft assembly, a base, a transmission device, and a motor. This article shares with you 7 reasons and countermeasures for the sudden shutdown of the sand making machine. 1. The material in the crushing cavity is blocked The blockage of materials will cause the equipment to stop suddenly. The reasons for the blockage of materials in the crushing chamber of the sand making machine are as follows: (1) Feeding is too fast. When the sand making machine is just started, if the material put in is too large or too hard, it will cause the equipment to be blocked, and there will be vibrations, so the equipment cannot be officially put into production when it is started. At the same time, it is not easy to put materials too fast, otherwise it will cause blockage. (2) The size of the discharge opening. When the discharge port of the sand making machine is too small and exceeds the minimum range of the equipment, some larger materials will accumulate at the discharge port of the crushing cavity, resulting in unsmooth discharge, and in severe cases, a crushing cavity will appear. The phenomenon of clogging. (3) Due to the high water content or high viscosity of the crushed material, it will stick to the outlet of the crushing cavity when the sand making machine is crushed, which will affect the discharge of the material and cause the phenomenon of blockage. It is recommended that when crushing materials, screening should be carried out first to avoid blockage during work. (4) When the sand making machine is crushing, when the hammer is worn or uneven, the crushing force of the hammer will be reduced. When crushing hard materials, the crushing operation cannot be completed, resulting in uneven or excessive crushing of the materials Phenomenon, and reduce the service life of the hammer. At the same time, the material is too large to affect the discharge of the discharge port, and in severe cases it will cause the crushing cavity to be blocked. Responses If the material in the crushing cavity is blocked, the material needs to be cleaned up. In subsequent use, materials with large particle size or high water content are prohibited from entering the machine, and the feeding should be kept uniform to avoid excessive feeding. 2. The triangle belt is too loose Check whether the V-belt is too loose or loses tightness. Responses If it is too loose and cause the machine to stop, you need to adjust the tightness of the V-belt. If the V-belt loses its tightness due to prolonged use, the V-belt needs to be replaced. 3. The working voltage is not suitable When the working voltage of the production site is too low, it is not enough to maintain the normal operation of the sand making machine and shut down. Responses Need to select a voltage that meets the requirements of the device. 4. The internal parts fall off If there is a sound of metal collision before the equipment is shut down, it may be that a part in the crushing cavity has fallen and the sand making machine suddenly shuts down. Responses It is necessary to check the inside of the equipment to confirm that the internal parts have fallen off, and then install it correctly. 5. The impeller is stuck When metal and other hard objects enter the crusher, the impeller of the sand making machine may be stuck, causing the equipment to fail to work. Responses It is necessary to strictly control the hardness of the material, and prohibit the entry of unbreakable materials. 6. The spindle is broken or the bearing is locked Responses If the main shaft is broken, the worn main shaft needs to be repaired or replaced. If it is caused by bearing lock, it is necessary to find out the cause of lock lock, install the bearing correctly, ensure that the bearing has a certain working clearance, and do a good job of lubricating the bearing, otherwise the problem cannot be solved fundamentally. 7. There is a problem with the device connection line If the connection line is broken or the contact is poor, the sand making machine will suddenly stop, especially when there is no sound without warning, it is likely that there is a problem with the connection line. Responses If the equipment connection line is broken or has poor contact, it needs to be adjusted or replaced in time.