Coolant falls into the horizontal spindle machine. So that the spindle worked for a long time. High-precision feed mechanism
02.11.2012
New Destinations in Coolant Storm for Metalworking
1. Oil instead of emulsion
In the early 90s. Proposals for replacing coolant emulsions to clean oils were considered from the point of view of the analysis of the total cost of the process. The main objection was the highest cost of anhydrous working fluids (5-17% of the total cost of the process) compared with water-based coolant.
Currently, the replacement of coolant emulsions to clean oil is the possible solution of many problems. When using clean oils, the advantage is not only in the price, but also in improving the quality of metalworking, as well as to ensure security in the workplace. In terms of safety, clean oils are less harmful when exposed to open areas of human skin, rather than emulsion. There are no biocides and fungicides in their composition. Anhydrous coolant has a longer service life (from 6 weeks for individual machines to 2-3 years in centralized circulation systems). The use of clean oils has a smaller negative effect on the ecology. Clean oils provide higher quality metalworking practically at all stages of the process (more than 90%).
Replacing the oil emulsion provides better coolant lubricating ability, improves surface quality during grinding (finishing) and significantly increases the service life of the equipment. The price analysis showed that during the production of the gearbox, the cost of almost all stages decreases twice.
When using anhydrous coolant, the service life of the equipment on CBN (cubic nitride boron) ripping and stretching holes is increased by 10-20 times. In addition, the processing of cast iron and soft steels does not require additional corrosion protection. The same applies to the equipment, even if the protective layer of paint is damaged.
The only disadvantage of anhydrous coolant is the allocation in the process of metalworking a large amount of heat. Heat removal can decrease four times, which is especially important with operations such as drilling solid high carbon materials. In this case, the viscosity of the applicable oils should be as low as possible. However, this leads to a decrease in the safety of work (oil fog, etc.), and evacuator exponentially depends on the reduction of viscosity. In addition, the flare point is reduced. This problem can be solved by the use of non-traditional (synthetic) oil bases that combine the high outflow temperature with low evaporation and viscosity.
The first oils that meet these requirements were mixtures of hydrocracking oils and esters, which appeared in the late 80s. XX century, and pure essential oils received to the market in the early 90s.
The most interesting are the oils based on esters. They have very low evaporation. These oils are products of various chemical structures, obtained from both animals and vegetable fats. In addition to low evaporation, essential oils are characterized by good tribological properties. Even without additives, they provide reduced friction and wear due to their polarity. In addition, they are characterized by a high viscosity-temperature index, explosion-fire-safety, high biostability and can be used not only as coolant, but also as lubricating oils. In practice, it is better to use a mixture of essential oils and hydrocrack oils, as the tribological characteristics remain high, and their price is significantly lower.
1.1. Family of multifunctional coolant
The use of clean oils was the crucial step in optimizing the cost of lubricants in metal processing processes. When calculating the cost of coolant, the influence of the cost of lubricants used in metalworking was underestimated. Studies in Europe and the United States have shown that over the year the mixing of hydraulic fluids from coolant occurs from three to ten times.
In fig. 1 These data are given in graphical form for the 10-year period in the European Automotive Industry.
In the case of coolant applied on a water basis, the ingress of significant amounts of oils in coolant leads to a serious change in the quality of the emulsion, which worsens the quality of metalworking, causes corrosion and leads to an increase in value. When using clean oils, coolant contamination with lubricants is irrevotably and becomes a problem only when the processing accuracy begins to decrease and equipment wear increases.
Trends to use clean oils as coolant metalwork open a number of cost reduction possibilities. An analysis conducted by German machine builders showed that on average, in each type of metalworking machines, seven different names of lubricants are used. This, in turn, raises problems of leaks, compatibility and value of all used lubricants. The wrong choice and use of lubricants can lead to the exit of the equipment failure, which is likely to entail the production stop. One of the possible solutions to this problem is the use of multifunctional products that satisfy a wide range of requirements and can replace lubricants of various assignments. An obstacle to the use of universal liquids is the requirements of the standard ISO.to hydraulic fluids VG. 32 and 46, since modern hydraulic equipment is developed taking into account the viscosity values \u200b\u200bgiven in these standards. On the other hand, metalworking requires low viscosity to reduce losses and improve heat removal at high-speed metal cutting. These contradictions in viscosity requirements with different use of lubricants are allowed by using additives, which reduces the total cost.
Benefits:
. Inevitable losses of hydraulic and permafront oils do not worsen coolant;
. the invariability of quality, which makes it possible to exclude complex analyzes;
. The use of coolant as lubricating oils reduces the total cost;
. improving the reliability, the results of the process and durability of the equipment significantly reduces the total cost of production;
. Universality application.
The rational use of universal liquids is preferable to the consumer. An example of this can serve as a motor construction. The same oil can be used in the primary processing of the cylinder block and when they are honed. Such technology is very effective.
1.2. Detergent lines
These lines of cleaning operations need to eliminate detergents on a water basis to avoid the formation of unwanted mixtures with hydrophilic oils. Solid pollution is removed from ultrafiltration oils, and detergents (energy consumption for cleaning and pumping water, the analysis of the quality of exhaust water) can be excluded, which will lead to a decrease in the total cost of production.
1.3. Removal of metal waste and equipment
The correct selection of additives allows you to engage back to the process of oil extracted from metal waste and from equipment. The volume of recycling is up to 50% of losses.
1.4. Prospects for universal liquids - " Unifluid»
Future for low-grade oil, which will be used as hydraulic fluid, and as coolant for metalworking. Universal liquid " Unifluid»Developed and tested in the German research project sponsored by the Ministry of Agriculture. This liquid has a viscosity of 10 mm 2 / s at a temperature of 40 ° C and shows excellent results at car motors manufacturing enterprises in metalworking processes, for lubrication and in power lines, including hydraulic systems.
2. Minimization of the number of lubricants
Changes in legislation and enhancing environmental protection requirements relate to and coolant production. Given international competition, the metalworking industry takes all possible measures to reduce the cost of production. Analysis of the automotive industry, published in the 90s, showed that the main problems of the cost are caused by the use of fluids, and the cost of coolant in this case plays an important role. The real value is caused by the value of the systems themselves, the cost of labor costs and the costs of maintaining liquids in working condition, the cost of cleaning both liquids and water, as well as disposal (Fig. 2).
All this leads to the fact that much attention is paid to a possible reduction in the use of lubricants. A significant reduction in the amount of coolant used as the result of using new technologies makes it possible to reduce the cost of production. However, this requires that solee function so as heat, decline in friction, the removal of solid contaminants, were solved with other technological processes.
2.1. Analysis of coolant needs for various metalworking processes
If coolant is not used, then, naturally, the equipment during operation is overheated, which can lead to a structural change and leave of metal, a change in size and even breakdown of equipment. The use of coolant, firstly, allows to remove heat, and secondly, reduces friction during metal processing. However, if the equipment is made of carbon alloys, the use of coolant can, on the contrary, lead to its breakdown and, accordingly, reduce the service life. And yet, as a rule, the use of cooling liquids (especially due to their ability to reduce friction) leads to an increase in the service life of the equipment. In case of grinding and honinging, the use of coolant is extremely important. The cooling system plays a huge role in these processes, as the normal temperature of the equipment is maintained, which is very important in metalworking. When removing the chips, approximately 80% of heat stands out, and the coolant performs a double function here, cooling both cutters and chips, preventing possible overheating. In addition, part of the shallow shavings goes together with coolant.
In fig. 3 shows the need for coolant with various metalworking processes.
Dry (without coolant) Metal processing is possible with processes such as crushing, and very rarely - when cutting and drilling. But it is impossible to pay attention to the fact that dry processing with the geometrically inaccurate end of the cutting tool is impossible, since in this case the heat dissipation and irrigation of the liquid has a decisive effect on the quality of the product and the service life of the equipment. Dry processing when crushing the cast iron and steel is currently applied using special equipment. However, the removal of chips should be made or simple cleaning, or compressed air, and as a result there are new problems: increased noise, the additional cost of compressed air, as well as the need for thorough cleaning from dust. In addition, dust containing cobalt or chromniecel is toxic, which also affects the cost of production; It is impossible to ignore and increased explosion hazardousness with dry aluminum and magnesium processing.
2.2. Small Sludge Systems
By definition, the minimum amount of lubricant is considered the amount not exceeding 50 ml / h.
In fig. 4 shows a schematic diagram of a system with a minimum amount of lubricant.
With the help of a dosing device, a small amount of coolant (maximum 50 ml / h) in the form of small splashes is supplied to the place of metalworking. Of all the types of dosing devices that exist on the market, only two types are successfully used in metalworking. The most widespread use of pressure systems. Systems are used, where oil and compressed air are mixed in the container, and the hose aerosol is supplied directly to the place of metalworking. There are also systems when oil and compressed air, without mixing, are fed under pressure to the nozzle. The volume of fluid supplied by the piston per course, and the frequency of the piston is quite different. The amount of compressed air supplied is determined separately. The advantage of using the metering pump is that it is possible to apply computer programs that control the entire workflow.
Since very small amounts of lubricant are used, the feeding directly to the workplace should be made with special accuracy. There are two scenery options that are very different: internal and external. With external feed fluid, the mixture is sprayed with nozzles on the surface of the cutting tool. This process is relatively inexpensive, easy to execute and does not require large labor. However, with external supply, the tool length ratio to the diameter of the hole must be no more than 3. In addition, when changing the cutting tool it is easily allowed to allow a positional error. When the inner supply of coolant, the aerosol is supplied through the channel inside the cutting tool. The ratio of length to the diameter should be more than 3, and the positional errors are excluded. In addition, the chips are easily removed through the same internal channels. The minimum diameter of the tool is 4 mm, due to the presence of the coolant channel. This process is more expensive, since the coolant occurs through the spindle of the machine. Systems with low yields have one common line: the fluid enters the working area in the form of small droplets (aerosol). At the same time, the main problems becomes the toxicity and maintenance of hygienic standards of the workplace at the proper level. Modern development of coolant aerosol systems allow you to prevent the workplace pouring, reduce losses when spraying, thereby improving air performance in the workplace. A large number of minor coolant systems leads to the fact that although it is possible to choose the desired drop size, but many indicators, like that: concentration, particle size, etc., are not sufficiently studied.
2.3. Coolant for minor systems
Along with mineral oils and nozzles on a water basis, oils based on esters and fatty alcohols are used today. Since in low-supply systems, oils are used for flow lubrication, sprayed in the working area in the form of aerosols and oil mist, then issues of labor and industrial safety (from and PB) become priorities. In this regard, the use of lubricants based on esters and fat alcohols with low-toxic additives is preferable. Natural fats and oils have a large drawback - low stability to oxidation. When using lubricants based on esters and fatty acids, precipitation is not formed in the working area due to their high antioxidant stability. In tab. 1 shows data on lubricant materials based on esters and fatty alcohols.
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For systems with low yields, the correct selection of lubricants is important. To reduce emissions, the lubricant used should be low toxic and dermatologically safe, while possessing high lubricant and thermal stability. Lubricants based on synthetic esters and fatty alcohols are characterized by low evaporation, high outbreak temperature, low-toxic and well established in practical application. The main indicators in the selection of low-emission lubricants are flash temperatures ( DIN EN ISO.2592) and the loss of evapoability on Noahaka ( DIN. 51 581T01). t. The VS should be no lower than 150 ° C, and the loss of evaporation at a temperature of 250 ° C is not higher than 65%. Viscosity at 40 ° C\u003e 10 mm 2 / s.
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With equal viscosity, lubricants based on fat alcohols have an outbreak temperature lower than based on esters. Their evaporation is higher, so the cooling effect is lower. Lubricating properties compared with lubricants based on esters are also relatively low. Fat alcohols can be used where lubricants are not the basic requirements. For example, when processing gray cast iron. Carbon (graphite), which is part of the cast iron, itself provides a lubricating effect. You can also apply them when cutting cast iron, steel and aluminum, as the working area as a result of rapid evaporation remains dry. However, too high evaporation is undesirable due to air pollution in the working area with oil fog (should not exceed 10 mg / m 3). Lubricants based on esters are advisable to use when good lubricant is needed and a large chip is observed, for example, when cutting threads, drilling and turning. The advantage of lubricants based on esters is in high boiling and flash temperatures at low viscosity. As a result, evacuability is below. At the same time, corrosion film remains on the surface of the part. In addition, lubricants based on esters are easily decomposed biologically and have the 1st grade of water pollution.
In tab. 2 shows examples of applying lubricants based on synthetic esters and fatty alcohols.
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The main aspects covered in the development of low-flow coolant are shown below. The main thing is to pay attention to the development of coolant, these are their low evaporation, non-toxicity, weak impact on human skin in combination with a high flare point. The results of new studies on the selection of optimal coolants are shown below.
2.4. The study of factors affecting the formation of oil fog coolant for low-feed systems
When a minor coolant system is used in the metalworking process, the formation of the aerosol occurs when the fluid is supplied to the working area, and the high concentration of aerosol is observed when using the external splashing system. In this case, the aerosol is an oil fog (particle size from 1 to 5 microns), which has a harmful effect on human lungs. The factors contributing to the formation of oil mist were studied (Fig. 5).
Of particular interest is the effect of viscosity of lubricant material, namely a decrease in the concentration of oil mist (oil mist index) with an increase in coolant viscosity. Studies were conducted on the influence of anti-human additives in order to reduce its harmful effects on human lungs.
It was necessary to figure out how the pressure used in the coolant system is affected by the amount of oil fog formed. In order to estimate the formed oil mist, a device based on the "Tindall cone" effect is used - Tyndallometret (Fig. 6).
To estimate the oil fog, the tyndallometr is located at some distance from the nozzle. The following data is processed on the computer. Below are the results of the assessment in the form of graphs. From these graphs, it can be seen that the formation of oil mist is enhanced with an increase in pressure during spraying, especially when using low-viscosity liquids. An increase in splashing pressure twice causes respectively an increase in the volume of the resulting fog also twice. However, if the splashing pressure is low and the starting characteristics of the equipment are low, then the period for which the amount of coolant reaches the required rules to ensure normal operation increases. At the same time, the oil fog index increases significantly when the coolant viscosity is reduced. On the other hand, the starting characteristics of splashing equipment are higher when using low viscosity fluid than when using high-viscous coolant.
This problem is solved by adding anti-human additives to coolant, which reduces the amount of fog formed for fluids with different viscosity (Fig. 7).
The use of such additive makes it possible to reduce the formation of fog by more than 80%, without degrading the starting characteristics of the system, no coolant stability, nor the characteristics of the oil mist itself. As shown by the conducted studies, the formation of fog can be significantly reduced with the right choice of the pressure of splashing and viscosity of the coolant used. The introduction of the appropriate antitum additives also leads to positive results.
2.5. Optimization of low coolant systems for drilling equipment
Tests were carried out on materials used in low-yield systems (deep drilling (ratio length / diameter of more than 3) with external coolant feed), on drilling equipment DMG. (Table 3)
In the workpiece from high-alloyed steel (X90MOG18) with high gap strength (from 1000 H / mm 2), a deaf hole is required. High carbon steel drill SE - rod with cutting edge with high resistance to bending, covered PVD-TIN. Coolant was selected in order to obtain optimal conditions of the process with regard to external feed. The effect of ether viscosity (coolant bases) and compositions of special additives on the service life of the drill were investigated. The test stand allows measuring the magnitude of the cutting forces in the direction of the Z axis (in depth) using the measuring platform of the cystler. The operating characteristics of the spindle were measured during the entire time required for drilling. The two methods adopted for measuring the loads with a single drilling made it possible to determine the load during the entire test. In fig. 8 shows the properties of two ether, each with the same additives.
Roman Maslov.
According to the materials of foreign publications.
The primary task of modern processing on metal-cutting machines is the grease of the tool, as well as the rapid removal from the chip cut zone. If this task is not fulfilled, there may be problems leading to premature wear or damage to the instrument, and even to the machine breakage.
The standard device of machines of the HAAS series and VM is a ring coolant mechanism, in which the coolant feed is provided by irrigation to the cutting area, the chips are simultaneously removed, which is formed when cutting.
This concept, compared to the traditional, in which hoses are used, significantly improved. The accurate adjustment of the tips of the lungs of the rings allows you to direct the coolant stream at various angles to the tool. Ergonomic rings installation provides ease of use and maximum gap.
In addition to the main coolant system, there are still other cooling methods. One of them is the use of coolant programmable nozzles (P-Cool), which, depending on the tool, are automatically adjusted under its length.
Spindle Coolant System
Another effective way is to supply coolant through the tilt of the instrumental mandrel and the channels of the cutting tool under high pressure. The coolant system via the TSC Spindle (Through-Spindle Coolant) is available in 2 configurations in accordance with the pressure: 300 or 1000 pounds per inch 2 (20 or 70 bar). Its effectiveness is particularly high when drilling deep holes and milling of deep recesses.
Air jet supply system through the tool
When using a modern carbide tool with advanced coatings for cutting in a dry medium, the likelihood of repeated cutting chips is large, timely unobed from the cutting zone. This is the main reason for the increased wear of the instrument. To solve the problem, Haas Automation has developed a system that applies a stream of air through the tool (addition to the TSC system), with which the chips are immediately removed from the processing zone, before it falls under the cutting tool. This method is important in the process of treating deep cavities.
The same function is performed using the air automatic GAAS gun. The system is flawless to use small tools that are unsuitable for air supply through the tool. Automatic air cannon is an excellent addition to the air supply system through the tool. The gun is used when it is impossible to use a liquid cooling system and, if necessary, feeding significant air volumes.
Minimum coolant system
In cases where it is impossible to use a lubricant-coolant, but it is necessary to provide a tool lubrication, the system of feeding the minimum amount of lubrication is used. The Innovative HAAS system sprays the moderate amount of lubricant to the tool cutting edges using an air jet. The amount of coolant used is so little that it cannot be seen.
The main advantage of the method is a slight consumption of lubricant material. The amount of air and coolant supplied independently, i.e. In each specific mode of operation, you can independently adjust the optimal cooling.
For a good drainage of chips when coolant drilling must be served through the tool if the machine is not equipped with the coolant system through the spindle, it is recommended under
For a good drainage of chips when coolant drill should be served through the tool. If the machine is not equipped with the coolant system through the spindle, it is recommended to supply coolant through special rotating adapters. With a hole depth of less than 1xd, the use of external cooling and reduced modes is allowed. The diagram shows the coolant consumption for various types of roller and materials. The type of coolant is recommended Emulsion 6-8%. When drilling stainless steel and high-strength steels, use a 10% emulsion. When using drilling heads IDM, use 7-15% emulsion based on mineral and vegetable oils for drilling stainless steel and high-temperature alloys. The coolant drilling is possible to drill the cast iron without coolant with the supply of oil fog through the drill channels. Symptoms of drilling head wear Changing diameter 0\u003e D Nominal + 0.15mm d Nominal (1) New head (2) The worn head increases the vibration and noise of D41 (Schshrti. (Schshdz / Manual using the processing condition The pressure of the internal cooling Recommended pressure values \u200b\u200band Consumption SOC (l / min) minimum coolant pressure (bar) Drill Diameter D (mm) Drill Diameter D (mm) For Special Twisted More 8xd Recommended High Pressure Coolant 15 70 Bar.
Most often, the coolant is supplied to the processing zone of a freely incident jet. Coolant flows from the nozzles of various designs under pressure 0.03-0.1 MPa (that is, under the action of gravity).
In addition to the watering method, the following types of fluid supply exist:
- pressure jet;
- jet air-liquid mixture in sprayed state;
- through the channels in the body of the cutting tool.
The pressure of the pressure jet is widely practiced with deep drilling operations. The jet pressure usually varies within 0.1-2.5 MPa, but can reach 10 MPa.
The pressure jet can be supplied both in the processing zone (from the side of the rear facet of the tool) and through the channels in the body of the instrument. When the processing zone is submitted, the speed of the pressure jet reaches 40-60 m / s. In order to reduce splashing, it is recommended to branch the stream of coolant: part of the stream is directed as a fine pressure jet, and a part is free watering.
When coolant is reduced, the following disadvantages are observed:
- the difficulty of ensuring the desired direction of the coolant jet to the cutting edge of the instrument;
- the need to care for coolant to avoid clogging nozzles;
- mandatory equipment of the machine with a special pumping station;
- strong splashing of fluid.
The serum supply in the sprayed state is carried out by mixing the liquid with air and its direction to the cutting zone. Such a supply is more efficient than cooling a unwritten jet, since the physical and chemical activity of aerosol colas is higher. In addition, the spraying method is distinguished by an extremely low yield.
Spray cooling is used in the case when irrigated by liquid is impossible or ineffective, if it is necessary to improve working conditions, in order to reduce the temperature deformations of parts during the processing process.
Coolas in the form of aerosols are used on aggregate machines, automatic lines and CNC machines, including multi-operational.
The feeding through the channels in the body of the tool is very effective, but it is possible for a limited tool nomenclature. Such a technology was distributed when cutting deep holes with spiral, rifle and annular drills, tags, trains. For the supply of coolant to rotating tools with internal channels, special ammunition and oil workers are used.
Deep holes are drilled with the forced outer or inner chip and the coolant.
The greatest difficulties occur when selecting coolant technology on the processing operations of deep holes with a small-sized tool without internal channels. In these cases, it is advisable to apply several fluid jets to the cutting zone evenly along the cone, the axis of which coincides with the axis of the cutting tool, and the peak is located in the gap between the conductor sleeve and the workpiece.
In the processing of deep holes, the soup feed (shock) method is also promising. Thus, when the coolant is filled with a frequency of 10-13 Hz, the processing, crushing, crushing and cutting of chips is 2-2.5 times higher than when the coolant is supplied by a continuous pressure jet.
On some boring operations in the coinkering and deployment of holes in a depth of less than two diameters, as well as holes of the small coolant diameter are injected through the annular nozzles.
Advantages of metal processing without the use of lubricating fluid (coolant) or dry processing sound visible: saving production costs for coolant and its cleaning, increase performance. However, it is not enough just to close the coolant faucet. To carry out dry processing, the machine must be functionally modified.
With the usual cutting, coolant performs the following main functions: cooling, lubrication, chip and removal of contaminants. In the exclusion of coolant use, these functions should be compensated by a machine and a tool.
Lubrication compensation
Coolant lubricating applies in two directions. On the one hand, the friction surface is lubricant between the part and the tool, and on the other, the lubrication of moving elements and seals in the working area. The working area of \u200b\u200bthe machine, located here, moving elements and the removal of chips should be designed to work with a dry chips. However, when cutting, no lubrication failure is possible in all cases, for example, when drilling on whole aluminum alloys. At this type of processing, the lubricant is necessary in the minimum dosing amounts in the form of an oil fog, which is fed under pressure on the cutting edges and into the chips of the drill. Such lubrication effectively reduces heat dissipation when cutting and sticking material to a tool that leads to a decrease in its performance. With a dosage supply of lubrication, its ashort is 5..100 ml / min, so the chips are weakly moistened with oil and can be deleted as dry. The content of oil in the chip directed to the smelting, with proper configuration of the system does not exceed the permissible value - 0.3%.
The dosage lubricant feed causes an increase in the contaminants of the part, fixtures and the machine as a whole and can lead to a decrease in the reliability of the processing process. To improve the lubrication of the cutting edges of the drill, the machines used for dry processing must be equipped with an internal flow of oil fog in the spindle hole. Next, the aerosol is fed through the channel in the cartridge and the tool directly to its cutting edges. The main requirement for the systems of dosage reduction of coolant is fast and accurately adjustable preparation of oil fog. Not only tool protection depends on this, but also purity in the working area.
Cooling compensation
The refusal of coolant and coolant should also be compensated by constructive changes in the machine.
In the process of cutting, the mechanical work is almost completely turning into heat. Depending on the parameters of cutting and the tool used 75: 95% of thermal energy remains in the chips, removed from the part. With dry processing, it performs the function of removal of heat generated from the working area. Therefore, it is important to minimize the effect of this heat transport to the accuracy of processing. The uneven temperature field in the working area of \u200b\u200bthe machine and the point transmission of thermal energy into the part, the device and the machine as a whole affect accuracy.
The possibility of accumulating chips on the device and parts of the machine should be excluded. From here it is clear that treatment is the unfavorable option. In order to limit the harmful effect of thermal energy, the machine should be designed in such a way that the thermal deformations of individual nodes and parts of the machine do not affect the position of the tool relative to the part.
Coolant flushing compensation
Since coolant is not used, then when processing materials such as cast iron or light metals, dust and the smallest chips are formed, which are no longer associated with liquid. Seals and protective devices must be additionally protected from abrasive effects.
Since the direction of the trajectory of the shavings is not definitely, then the effect of gravity should be used. To do this, it is necessary to ensure the unimpeded fall of the chips on the removal conveyor, located at the bottom of the workspace. Any horizontal plane becomes a storage with chips and can affect the reliability of processing.
Another fraction of chip removal is the system of vacuum suction. The main requirement here will be the placement of suction nozzles as close as possible to the working area to increase the reliability of chip trapping. You can recommend the systems in which the nozzle is attached to the spindle or tool as well
in which the nozzle is installed with a programmable turn in the next mode. In some cases, for example, when milling the planes, the end milling cutter, the suction effect can be strengthened by using the bell-shaped fencing cutter. Without it, a powerful air flow will take a powerful air flow for capturing the chips.
The suction system should, first of all, remove dust and excess oil mist, and the removal of large chips is the task of the chip conveyor. Sleeping of the smallest particles is very important, because, mixing with an aerosol, they form a durable mud layer. The air from the suction system is returned to the environment and must be carefully cleaned from the suction products.
Safety aspects with dry processing
With dry processing, it is necessary to take into account the possibility of explosion of dust in the workspace. Therefore, the dust pumping nozzle must be placed in such a way as to eliminate the appearance of zones with a critical concentration of dust.
The risk of ignitions of oil aerosols, as studies conducted at the Institute of Machine Tooling and Technological Equipment of the University of Karlsruhe, are extremely unlikely. When working suction systems and workshop air conditioners, this danger can be neglected. All these statements may scare the small production and manufacturers of individual details. Many represent the transition from processing with coolant to dry processing is much easier.
Path to a multi-purpose machine working on dry technology
A machine-tool firm that knows exactly where to go, is Hüller Hille. This supplier of complete systems is required to provide high quality processing in automatically operating settings. The same requirements should be presented to all machines working on dry technology. As an example, in Fig. 1 shows the production module of the technological system intended for processing the car wheel bracket. On each of the two machines included in the module, at 3 replaceable work, it is processed with dosage coolant supplies1400 pairs of brackets. Processed material - aluminum.
Submission of dosage lubrication when cutting light alloys
If in the processing of gray cast irons in a wide range, it is possible to realize completely dry processing, then when drilling, deploying and threaded by aluminum and magnesium alloys, dosage supply is required to ensure reliability of the process. Otherwise, due to the blocking groove driving, there is a threat of frequent breakdowns of the instrument and the formation of an outflow that prevents the preparation of high-quality processing.
The main aspect is the lubrication lubrication. With dosage coolant - this is an air-and-oil mixture (aerosol).
The systems currently used by type of supply of aerosols are divided into external and internal. If, with an external supply of aerosol or individual oil drops, you can contact directly to the cutting edges of the tool, then with the inner dosage oil supply, it is performed through the spindle and the channel in the tool to the cutting zone. There are also 2 technical solutions: a 1-channel and 2-channel approach. With a 2-channel supply, air and oil are served separately and mixed immediately before feeding to the tool. This allows you to quickly deliver the mixture to the working area and reduce the path of aerosols inside the quick-repair parts, thereby reducing the danger of its bundle.
In fig. 2 shows the technical solution used by Huller Hille, for separate supply of aerosol components through a rotating distributor to the spindle. The oil falls into the dosing device, which pushes it into the housing, made by powder metallurgy. The housing is a storage device for oil and a mixer with the summed air. The aerosol is formed immediately before entering the tool channel. This is how the minimum path is created to the cutting edge, where the effect of the bundle is possible. The device allows you to accurately adjust the content of oil in aerosols and thanks to this it is more accurate to adapt to the conditions of operation of various tools.
In addition, the device allows you to quickly turn on and off the dosage of coolant. Depending on the channel design in the instrument, the response time can be 0.1 s. This allows you to turn off the oil supply during the positioning process, which helps to reduce the flow of oil and the pollution of the machine.
As a result, with the experimental processing of the cylinder head, the average oil consumption was 25 ml / h, whereas when processing with free watering, consumption reaches 300: 400 l / min.
Currently, to eliminate dead zones, test tests of the dosage system of coolant, aimed at increasing the aerosol homogeneity, decrease in the oil content and optimization of the structure of the aerosol supply through the type shank<полый конус>. The solution to these problems will reduce the oil consumption and the pollution of the machine. The possibility of adaptive control of the lubricant jet depending on the specified and measured volumetric flow values \u200b\u200bis investigated. This will maintain permanent lubrication conditions when the temperature, viscosity, internal instrument geometry changes.
Optimization of the working area of \u200b\u200bthe machine
In addition to the spindle created in accordance with the requirements of the dosed lubricant submissions through the internal cavity, Huller Hille has released a multipurpose machine designed to handle parts for dry technology. The base for reliable chip removal was the constructive design of the working area. So excluded all sorts of edges and planes on which chips can accumulate. The size of the windows for the free passage of the incident shavings are increased, which are limited to steep walls (angle of inclination of more than 55 0). Unpainted steel sheets of fences are reduced to a minimum sticking of chips and the formation of subpalin.
The installation of a device with a part on the vertical wall is important for the unobstructed fall of chips (Fig. 3). On the machine for changing satellites with parts is used rotary around the horizontal axis internal manipulator. In the change position, the part takes the usual vertical position and can be replaced by manually or automatically an external manipulator connecting the machine with the transport system.
When chopping chips from the working area uses a dusting system. As prescribed in the UES countries, the suction nozzle is located under the grid conveyor. It takes dust particles, residues of aerosol and fine chips. A large chips is delayed by a conveyor grid and they are removed. Such a solution allows to reduce the power of the dust system.
Despite the optimal embodiment of the part, in some cases the chips are not removed by a free drop, for example, when processing cabinet parts having internal cavities where it can accumulate. For such cases, the machine is equipped with a round table with a high frequency of rotation - 500 min -1 compared to 50 min -1 on ordinary machines. With a rapid rotation, the chips is thrown out of the cavities of the part, especially if it is set to a horizontal position when changing it from time to time.
An important aspect is the pollution of the machine. The fine chips, moistened with oil, covers a rather thick layer of the machine nodes in the working area. If, due to the high kinetic energy, the deployed large chips is difficult to remove the suction, then the small, which is the main component of the contamination, is easily removed. Therefore, the use of dustproof is the main component of contamination.
The topical subject of research is to search for universally used solutions of dust removal for various types of tools or the possibilities of using the store and manipulator of the automatic tool changing system for automatic shift of suction devices.
Thermal effect
Thermal problems relate to both devices for fastening parts and the processing process and the machine as a whole. The machine must have a thermosymmetric design. 3 coordinate nodes that the Specht Gamma Machines are completed, satisfy these conditions. The swivel in the vertical plane of the internal manipulator for the satellite with the part is mounted on two supports in the frame-type rack, which also provides thermosymmetry of the structure. Thus, the uniformity of thermal deformations of the machine perpendicular to the surface of the part is ensured. In the upper part, the rack is connected to the 3-coordinate knot. Together with a bundle at the bottom of the bed, the design eliminates tilting. A pure translational displacement occurs, which can be taken into account by the introduction of compensation.
Thermosymmetry, however, does not prevent errors along the z axis, in the integrity of the spindle lengthening and the machine nodes. In general, the processing operations in which accurate positioning on the Z axis is found not so often. Nevertheless, Hüller Hille offers additional possibilities for active compensation for error through this axis. So, the SPECHT 500T machine is equipped with a laser tool breakage system. The position of the control grades on the spindle and on the adaptation is recorded by a laser beam, by means of which the change in the positions is determined and the correction is introduced.
Construction of the processing process determines accuracy
For the same construction of the process is decisive to achieve accuracy. The sequence of operations during dry processing in comparison with wet is substantially changed. In most cases, direct transition of the sequence of operations with wet processing on dry is not desirable. On the other hand, the sequence used for dry technology is not harmful and wet technology. Therefore, dry processing concepts can be accepted in any cases.
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