# Recent questions in Physics

Factors Affecting Dimensional Precision of Precision Casting

In general, the precision precision of cast parts is affected by the casting structure, casting material, mold making, shelling, roasting, pouring and other factors, any one of the links set, the operation will cause the casting shrinkage will change, Resulting in casting dimensional accuracy and requirements are biased. The following are the factors that can cause defects in the accuracy of Precision casting:
(1) the impact of casting structure: a. Casting wall thickness, shrinkage, casting wall thin, small shrinkage. B. Free shrinkage rate, hinder the shrinkage rate is small.
(2) the impact of casting material: a. The higher the carbon content of the material, the smaller the line shrinkage, the lower the carbon content, the greater the line shrinkage. B. Common material casting shrinkage rate is as follows: casting shrinkage K = (LM-LJ) / LJ × 100%, LM for the cavity size, LJ for the casting size. K is affected by the following factors: wax mold K1, casting structure K2, alloy type K3, casting temperature K4.
(3) the impact of molding on the shrinkage of the casting line: a. Wax temperature, wax pressure, holding time on the size of the melt to the temperature of the most obvious wax, followed by wax pressure, holding time in the guarantee The effect of melt-molding on the final size of the melt is very small. B. The line shrinkage of the wax (mold) material is about 0.9-1.1%. C. When the mold is stored, shrinkage will be further generated, the shrinkage value is about 10% of the total shrinkage, but after 12 hours of storage, the die size is basically stable. D. The radial shrinkage of wax mold is only 30-40% of the shrinkage rate in the longitudinal direction. The effect of wax wax temperature on the free shrinkage is much greater than that on the shrinkage shrinkage (the best wax temperature is 57-59 ℃, The higher the temperature the greater the contraction).
(4) the impact of shell material: the use of zircon sand, zircon powder, on the shop sand, shop powder, because of its small expansion coefficient, only 4.6 × 10-6 / ℃, so negligible.
(5) the effect of shell roasting: the expansion coefficient of the shell is small, when the shell temperature is 1150 ℃, only 0.053%, so it can be ignored.
(6) the impact of casting temperature: the higher the pouring temperature, the greater the shrinkage, pouring temperature is low, the smaller the shrinkage, so the pouring temperature should be appropriate.

Precision casting industry development

Precision casting industry development goals are the following aspects:
First, the completion of the growth mode by the labor, resource-intensive to the technology capital-intensive changes from extensive pollution to green intensive type of change, the product quality, variety, the number of the world's advanced level, the proportion of high-quality materials Increase, the entire precision casting plant production efficiency, economic benefits doubled; environmental pollution has been effectively managed, initially built with the environment co-ordination of China's casting materials industry system.
Second, the formation of a number of reasonable structure, the overall level of high combination of research and development and education and training base, can continue to transport professional personnel, and constantly develop high-quality, high-grade casting new varieties of materials to meet the growing casting materials Need, and gradually increase the intensity of technology exports.
Third, to complete the industrial structure adjustment, out of a number of low technological level, poor product quality, serious pollution, poor economic efficiency of small precision casting plant, the formation of a relatively concentrated "small giant" and "Star Enterprise" to achieve "professional Of large-scale "production. In particular, to the emergence of one or two world-renowned enterprises to compete with the backbone of enterprises, their high level of technology, well-equipped, well-funded, advanced management level, can continue to provide high-end market, high-quality casting materials, market share High rate.

Precision casting development prospects

Investment Casting is a fusible material made of fusible material, on which a number of layers of special refractory coating, after drying and hardening to form a whole shell, and then steam or hot water from the shell Melt the model, and then put the shell in the sand box, filled with dry sand in its surrounding shape, and finally the mold into the roasting furnace after high temperature roasting, casting or shell by roasting, pour molten metal in which Get cast.
The precision welding of the products obtained by Precision casting is very close to the final shape of the parts, which can be used without processing or very little processing. It is an advanced process of near net forming. It is an excellent process technology in the casting industry. Application is very extensive. It is not only suitable for all types of casting of various alloys, but also to produce the casting size accuracy, surface quality than other casting methods to be high, and even other casting methods difficult to cast the complex, high temperature, easy to process castings, Can be used to melt casting precision casting.
At present, the world's investment casting process has developed rapidly and widely used. From the current situation, the future development trend of the process is that the casting products are getting closer to the parts and components. The traditional casting is only blank, Market quick response. The complexity of parts and components and the quality of the increasingly high grade, research and development means more and more strong, professional collaboration began to show, CAD, CAM, CAE application of parts and components to become the main technology.
From the current development situation analysis, investment casting technology is very wide range of applications, the future development prospects to be broad.

Daily Production of Ore Milling Equipment

Power plant mill 'test does not change the tile' refers to the thermal power plant pulverizer of the gold pad in more than 60 ℃ high temperature work to maintain a stable state, not because of the bearing temperature and the export of lubricating oil temperature caused by rapid high temperature Bearing seat vibration intensified and then melted, there is a thermal ore milling equipment operation in the 'tile' phenomenon.

Only the ore milling equipment 'trial operation does not change the tile', in order to allow the entire fire power plant safe operation In addition, the ore milling equipment in the work process, the fine grinding of coal powder is also related to the power of the power plant The In the thermal ore milling equipment to complete the grinding and grinding work, will be through the heat of the coal into the boiler, and then the coal combustion in the boiler after the formation of hot flue gas will flow along the boiler to exotherm, follow-up coal ash Separation.

Power plant mill grinding efficiency and fine degree of a good guarantee, then easier, the coal in the boiler full combustion, but also can improve the utilization of coal and reduce the possibility of environmental pollution.

Construction waste disposal equipment for construction waste special crusher

At the beginning of the new year, the local two sessions were held this month. To the construction waste disposal industry is excited that in this year's local two sessions, on the promotion of construction waste disposal recommendations and comments have mushroomed. So what are the concerns and suggestions for building waste disposal?
In recent years, with the rapid progress of urbanization in Fuqing City, Fujian Province, road construction, area transformation involving more than one million square meters of housing relocation, resulting in a large number of construction waste. At present, these construction waste is basically landfill treatment, can not be recycled, resulting in waste of resources, destruction of the ecological environment.
Assembly construction can shorten the construction period, reduce construction waste, reduce environmental pollution. According to the General Office of the State Council in September 2016 "on the development of assembly-oriented construction of the guidance", the proposed timely introduction of Fenghua policy, in the "three five" period, vigorously support the development of assembly-style construction, promote Fuqing ecological civilization construction, Strengthen the construction waste management capacity. At the same time, in Fuqing City to carry out the Construction Waste Crusher pilot, the use of commercial operations, the implementation of classified classification of construction waste, such as grinding into powder, turning waste into treasure and so on.
Today, Xiamen City, Fujian Province has started construction waste resource utilization, as soon as possible into the ranks of resources to help the city building waste turning waste into treasure. Xiamen Honglu Sheng construction waste recycling projects are used from the SBM independent research and development of construction waste construction waste single-stage broken modular production line, the host using DPF construction waste special crusher, the performance is very stable, superb assembly skills, and very focused on environmental protection , The production of recycled aggregate processed into a block, paving brick, tile tiles and other building materials products, to achieve the construction waste recycling, reduction, harmless economic, social and ecological benefits.
In addition, SBM construction waste crusher is a domestic steel cutting device with a special garbage crusher, the host will not be blocked, recycled bone grain size is good, variable three broken broken single section, with the file model in the more cost-effective High, is the best building waste crushing equipment.

out of the mill's 'trial delivery

Double inlet and double is an important equipment in coal-fired units of thermal ore milling equipment. The safety and stability of operation are directly related to the whole work of the whole thermal power unit. Therefore, Must be carried out quality testing, which should be verified during the trial operation of the load, double into the double out of the coal mill function to achieve 'trial delivery of the tile' quality.

Double into the double out of the mill's 'trial delivery of the tile' refers to the thermal ore milling equipment of the Ukrainian bearing in more than 60 ℃ high temperature work to maintain a stable state, not because the bearing temperature and export lubricants temperature fast High temperature and lead to vibration at the bearing seat and then melt, then double into the double mill operation of the 'tile' phenomenon.

Only double into the double out of the coal mill 'trial delivery of the tile' in order to allow the entire thermal power unit safe operation In addition, low-speed coal mill in the course of work, the fine grinding of coal powder is also related to the ore milling equipment power combustion The quality of the. Generally after the low-speed coal mill to complete the pulverized coal mill, the use of hot air in the drum drying of coal, after the separation of the separator into the burner for combustion and heating. Because the structure of low-speed coal mill is very large, grinding the type of coal, so it is also widely used in thermal ore milling equipment power generation.

artificial sand making machine performance

Sand making machine is one of the most used equipment in the mining industry, is dedicated to the production of building sand, sand road equipment, can put all kinds of rock, gravel. Sand making machine made various size of buildings, made of sandy granularity, high compressive strength, than natural sand, manufactured by sand conforms to the architectural requirements, can improve the quality of construction, with the hot sand, sand making equipment is also increasingly popular.
The sand making machine is a for producing artificial sand with mechanical processing as the main way. With the popularization and application of artificial sand, it is also developing steadily. There are "rock stone" and "hot stone" two types of "rock stone" for abrasive material processing and strong; "hot stone" for abrasive material processing is not strong, "hot stone" into the sand rate 35% higher than "rock stone". The use of selective fragmentation and cleavage of advanced crushing principle, directly applied enough kinetic energy on the sand, and converting kinetic energy into the broken sand required by the impact, the material particles produced in many areas meet the material demand.
Sand production line we have been very familiar with, equipment is composed of vibrating feeder, jaw crusher, sand making machine, vibrating screen, sand washing machine, belt conveyor and other equipment combination, first by jaw crusher for coarse crushing, fine crushing of the crusher, the vibrating sieve get the required size, unqualified size by belt conveyor back river gravel sand machine sand process, according to the need can increase the sand washing machine, the impurities in stone wash. The sand making line can be produced by dry sand making and wet sand making process. The main difference is whether to use water or not. What kind of sand production line is adopted, and the users should combine their actual needs.

SBM machinery to explain the construction waste crusher handling equipment precautions

In the construction waste crusher processing line, we may think that he has little effect, but in fact it is indispensable in the process of building waste disposal, which not only improves the surrounding environment, but also is available Resources have also been greatly improved, it can be seen, Construction Waste Crusher processing equipment is essential. SBM machinery below to tell you about the use of some of the useful parts of construction equipment and the need to avoid dangerous matters. Hope to give you a little help
1, boot work, should be carefully examined to recognize the ministry is not qualified, qualified before the official start work.
2, installed at the point should ensure that the loading and unloading of the tape in the center of the direction, not allowed in a large height directly unloaded to prevent injury to tape and lead to tape deviation.
3, the reducer, motor, coupling and all the drum bearing the temperature is not normal, movement is not abnormal.
4, the conveyor belt material should be carefully observed during the delivery of the situation, found abnormal should be timely downtime.
5, the conveyor belt tension is not appropriate, with or without skid deviation, card grinding and other abnormal appearance.
6, often check the hydraulic coupler, hydraulic system, reducer is not leaking, regularly check the amount of oil is not appropriate, and timely adjustment to add.
7, Construction Waste Crusher equipment before starting, should first start close to unload the drum motor, in the drive near the storage tank of the motor, so that the surface when the load exceeds the load.
8, maintenance should be shut down, should be hung on the stop signs.
9, before the shutdown should clean up the debris.
10, the conveyor belt on the material after processing completely in order to stop the construction waste disposal equipment.

Will the ultrafine mill freeze in the winter?

In our lives, there are many times when we use electrical appliances and our food and so on will be affected by the weather, hot summer will burn electrical or rotten food, cold winter will freeze these items, so in order to reduce this Kind of unnecessary damage, we need to carry out different maintenance measures.
Not only these small size of the items will be affected by the climate, for ultrafine grinding of such a large production equipment, the same will be affected by the external climate, such as hot weather or cold weather, lubricating oil will degenerate, Then it will affect the effect of lubrication, and thus cause the mill state of production changes, not only that, these extreme weather will cause damage to equipment, where to analyze the ultrafine mill machine in the winter, will not Frozen problems.
We know that manufacturers in the production of ultrafine grinding of this equipment, its structure is composed of many different components, these components for the production, but also played a significant role, such as bearing not only assume the majority of equipment The weight of the role, but also played a role in the transmission, such as grinding roller grinding ring is mainly played the role of grinding materials, these different components for the production of the role is not the same, but they are in common need to lubricate, and will be outside the air influences.
First of all, for lubrication, due to the role of cold weather will occur when the phenomenon of solidification, so at work, we need to choose lower than the local climate temperature freezing point of the oil, so as to ensure the effect of lubrication in order to ensure that the super Fine grinding parts of the normal work;
The next is the mill parts are made of steel, and then made by the advanced casting process, so they will be affected by the outside temperature, the weather is cold, then it will make SCM ultrafine mill parts of the phenomenon of freezing , So we need to put it in the room or to cover it, to prevent frost, in addition to preheating before the boot, so as to better production;
The article mainly describes the ultrafine grinding in the winter when it will not freeze the problem, the conclusion is frozen, mainly through two aspects of the analysis, for each aspect we introduced the corresponding solution to ensure that Its normal working condition, in order to ensure the smooth progress of production.

The new classification crusher

A crushing apparatus for energy efficient occurred in twentieth Century 80 time later period, called construction waste crusher, just as its name implies is to crush large materials at the same time, for less than the discharge opening material without broken but with the roller rotates to discharge, to a certain extent, that has a dual role, in fact, it is a kind of with double gear, crushing machine and using the new crushing mechanism manufacture, is a crusher has good market foreground.
After the crushing machine available has caused a great sensation, all parts of the country began to rise production construction waste crusher, crushing roller basically are used in gear shape structure of small roll diameter, shape of cross arrangement of teeth, broken selectively to the material, and the finished products particle type uniform, set all the advantages in one, so customers are willing to choose construction waste crusher crushing equipment as part of their production lines, in many companies, the crusher production specifications are not the same, after feedback customer verification and the market was informed, Shanghai Zenith construction waste crusher is popular, and the construction waste crusher price advantage is obvious, and has low energy consumption, high production efficiency, body lighter and automation device has the advantages of simple operation and easy to understand and other advantages, has become the industry a much told story.

SBM construction waste disposal equipment once again in Shenzhen resource project successfully put into operation

Recently, SBM mobile construction waste disposal equipment once again in Shenzhen resource project successfully put into operation, this is SBM multiple sets of Construction Waste Crusher equipment settled in Shenzhen, crack construction waste "siege" trend.
Shenzhen space is small, the land is limited, and the city construction day by day, how many increase in the storage field can not fundamentally meet the needs of construction waste landfill, and construction waste dumping phenomenon, and can not rely on increased punishment can get Radical cure. It is reported that the annual output of more than 50 million square meters of Shenzhen mud, which can be reused the annual output of about 10 million tons of construction waste, 10,000 tons of construction waste to account for 2.5 acres of land, then Shenzhen annual construction waste at least Covering an area of 2500 acres, garbage siege trend gradually become.
In order to change the traditional construction waste disposal, resource recycling has become an inevitable choice. With the resources to look at the construction of garbage, with market-oriented means to digest the construction waste, with a strong rule of law and effective policies to regulate construction waste. Therefore, a company in Shenzhen to introduce SBM mobile construction waste disposal equipment for the use of resources, the output of a variety of recycled building materials, efficient processing of construction waste and ecological restoration of the urban environment.
At present, the construction waste recycling products to a variety of types, high quality, high value-added direction, the average rate of resources in more than 95%, resource-based process to achieve pollutant standards "0" emissions, profit model can not rely entirely on government subsidies Market-oriented operations, and to achieve key technology processes, equipment breakthroughs, complete the technology and standards of the whole industry chain coverage. In addition, SBM construction waste disposal equipment can be 100% of the construction waste recycling rate, 100% of the environmental protection process, 100% market rate of recycled products, and promote the development of resources to achieve social, economic and ecological coordination of the three benefits.

A 50 kg crate is being pushed on a horizontal floor at constant velocity. Given that the coefficient of kinetic friction between crate and floor is $\mu$k = 0.1, what is the push force F?
A uniform ladder of length L is leaning against the side of a building, as shown. A person of mass m = 75 kg is standing on it. The mass of the ladder is M = 10 kg. The coefficient of static friction between the ground and ladder is $\mu$s1 = 0.5, and the coefficient of static friction between the wall and ladder is $\mu$s2 = 0.3. What is the minimum angle $\theta$ so that the ladder doesn't slip?