Features of spindle nodes. An important feature of multi-purpose CNC machines is the use of motor spindles in their design. They provide high rotational accuracy, big numbers revolutions (up to 60,000 rpm and more), have small dimensions and their own weight. A prerequisite is the presence of cooling systems. The systems of external and internal coolant supply are used. The external system is based on the use of nozzles installed in the right direction to cool the cutting tool and flush chips from the machined surfaces. internal system provides coolant supply directly through the spindle. The pressure of coolants can reach significant values.

One example of the appearance of such a spindle is shown in Fig. 79. And in fig. 80 shows a section through a similar device. Attention should be paid to the presence of vibration sensors and temperature sensors on the bearings, as well as a tool presence sensor and a position sensor.

Rice. 79. Appearance spindle for high-speed machining of parts

Rice. 80. Structural diagram of the spindle device (longitudinal section)

Such a number of sources of information about the machining process makes it trouble-free and safe at high cutting conditions, and allows you to obtain the required dimensional accuracy of the workpieces.

On fig. 81 shows graphs of the operation parameters of spindle assemblies of multi-purpose machines. Number 1 indicates the dependence curve of the developed power on the spindle speed, and number 2 - the curve of the dependence of the developed torque also on the spindle speed.

The nature of the change in these parameters is clearly visible from the shape of the curves and does not require explanation.

The MTS-28.63 model spindle is characterized by higher values ​​of power and torque parameters than the ETS-21.32 model spindle, which coincides with the data in Table. 10. The number of revolutions is much less.

Therefore, the MTS-28.63 model should be used for more severe machining conditions, including for roughing operations.

Rice. Fig. 81. Graphs of parameters (power and torque) of the operation of spindle units: a - spindle model ETS-21.32; b – spindle model MTS-28.63

Tab. 10. Models of spindle units of machine tools and their technical data

Tab. 11. Main characteristics of some spindle units of machining centers

Spindle units, as the main units of machine tools and the most responsible for the quality of processing, are equipped with additional systems. Among them are an internal cooling system, a system for supplying coolant to the tool through the spindle, a system for cooling parts by watering under pressure through special nozzle tubes. There are vibration magnitude sensors, as well as temperature sensors for bearing assemblies, the presence of a tool, etc. (Fig. 82).

Given the difficult high-speed machining conditions, the issues of quick replacement of bearing assemblies and increasing the durability of bearings through the use of ceramic rolling elements are being addressed.

A

b

Rice. 82. Scheme of placement of sensors: a - the presence of vibration; b - bearing heating temperatures

Machine cooling systems. The developers of CNC machine tools pay great attention to the problem of cooling. The object of attention is the spindle units, the rotational speed of which reaches tens of thousands of revolutions per minute. The accuracy of processing and the durability of the operation of the units themselves depend on the effective cooling of the structural elements of the machine.

It is even more important to effectively cool the workpiece and the tool in the cutting zone. This determines the accuracy of the resulting dimensions and the durability of the cutting tool. Currently, various schemes for supplying LC to the cutting zone are being used (Fig. 83). For example, feed under pressure through the spindle and channels made in the tool. In this case, the part is cooled directly over the surface being machined (in the hole). Improved cutting conditions due to chip flushing. Carbide drills with a diameter of 1 mm or more can be supplied with such channels for internal supply.

The primary task of modern machining on machine tools is tool lubrication, as well as the rapid removal of chips from the cutting zone. Failure to do so can result in problems leading to premature tool wear or damage, and even machine failure.

A standard feature on Haas and VM series machines is an annular coolant supply that provides coolant by spraying into the cutting area while removing chips that form during cutting.

This concept, compared to the traditional one, which uses hoses, is significantly improved. Precise adjustment of the tips of the easily moving nozzles of the ring allows you to direct a jet of coolant to the tool under different angles. Ergonomic ring setting provides ease of use and maximum clearance.

In addition to the main coolant supply system, there are other ways of cooling. One of them is the use of programmable coolant nozzles (P-Cool), which, depending on the tool, automatically adjust to its length.

Coolant system through the spindle

Another effective method- supply of coolant through the tail of the tool holder and the channels of the cutting tool under high pressure. The TSC (Through-Spindle Coolant) coolant system is available in 2 pressure configurations: 300 or 1000 psi (20 or 70 bar). Its efficiency is especially high when drilling deep holes and milling deep recesses.

Air jet system through the tool

When using modern carbide tools with advanced coatings for cutting in a dry environment, there is a high probability of re-cutting chips that are not removed from the cutting zone in a timely manner. This is main reason increased tool wear. To solve the problem, Haas Automation developed a system that blows air through the tool (an addition to the TSC system) that immediately removes chips from the cutting area before they enter the cutting tool again. This method is important in the process of processing deep cavities.

The same function is performed using the Haas automatic air gun. The system is flawless to use small tools unsuitable for supplying air through the instrument port. An automatic air gun is a great addition to a through-tool air supply system. The gun is used when it is impossible to use a liquid cooling system and when it is necessary to supply significant volumes of air.

Minimum Coolant System

In cases where it is not possible to use a cutting fluid, but it is necessary to ensure tool lubrication, a system for supplying a minimum amount of lubrication is used. The innovative Haas system sprays a moderate amount of lubricant onto the cutting edges of the tool using an air jet. The amount of coolant used is so small that it cannot be seen.

The main advantage of the method is the low consumption of lubricant. The amount of air and coolant supplied is independently adjustable, i.e. in each specific operating mode, you can independently make adjustments for optimal cooling.

Manufacturer: Sunmill, production: Taiwan

General Information of JHV-710 CNC Vertical Machining Center

Options, descriptions

Every SUNMILL machine is tested:

BALL BAR TEST

Using the ball bar test, roundness, out-of-shape and backswings (actuator mismatch) are checked.

Laser check

Additional options:

4th and 5th axis processing (option) :

On a CNC milling machine, it is possible to install a 4th / 5th axis, and, accordingly, create a 4th / 5th coordinate machining center. On the table of the machining center can be installed as a vertical Rotary table(4th axis) and tilt/tilt axis (5th axis). When installing the 4th or 5th axis, it is recommended to use the FANUC 18iMB control system.

Coolant supply through the spindle:

Supplying coolant through the spindle using a special tool allows better heat dissipation when machining blind holes and avoids overheating of the tool and workpiece. Supplied complete with filtration system.

High-speed spindle that allows you to withstand the parameters: 10000, 12000, 15000 rpm.

Tool magazine for 20 or 24 positions.

Complete set of this machine.

• CNC system Fanuc 0i-MD controller.
• Fourth axis interface.
• Spindle BT40 10,000 rpm
• Motor power 5.5 / 7.5 kW
• Spindle drive
• Spindle taper blowing system
• Automatic lubrication system
• Carousel magazine ATC 16-tools, BT40
• Complete cutting area enclosure
• Machine lighting
• Toolbox and Documentation Kit
• Oil cooled spindle
• Chip screw conveyor

Equipment for an additional fee:

02.11.2012
New Directions in Coolant Technology for Metalworking

1. Oil instead of emulsion

In the early 90s. proposals to replace coolant emulsions with pure oils were considered from the point of view of the analysis of the total cost of the process. The main objection was high price anhydrous working fluids (5-17% of the total cost of the process) compared to water-based coolants.
Currently, replacing coolant emulsions with pure oils is a possible solution to many problems. When using pure oils, the advantage is not only in price, but also in improving the quality of metalworking, as well as ensuring safety in the workplace. In terms of safety, pure oils are less harmful when exposed to exposed areas of human skin than emulsions. They do not contain biocides and fungicides. Anhydrous coolants have a longer service life (from 6 weeks for individual machines to 2-3 years in centralized circulation systems). The use of pure oils has less Negative influence on ecology. Pure oils provide a higher quality of metalworking at almost all stages of the process (more than 90%).
Replacing the emulsion with oils provides better lubricity of the coolant, improves the surface quality during grinding (finishing) and significantly increases the service life of the equipment. The price analysis showed that in the production of a gearbox, the cost of almost all stages is halved.
When using anhydrous coolants, the service life of equipment for CBN (cubic boron nitride) peeling and hole broaching increases by 10-20 times. In addition, when machining cast iron and mild steels, additional corrosion protection is not required. The same applies to equipment, even if the protective paint layer is damaged.
The only disadvantage of anhydrous coolants is the release of a large amount of heat during the metalworking process. Heat dissipation can be reduced by a factor of four, which is especially important in operations such as drilling in hard, high-carbon materials. In this case, the viscosity of the oils used should be as low as possible. However, this leads to a decrease in operating safety (oil mist, etc.), and the volatility depends exponentially on the decrease in viscosity. In addition, the flash point is reduced. This problem can be solved by using unconventional (synthetic) oil bases that combine high flash point with low volatility and viscosity.
The first oils to meet these requirements were mixtures of hydrocracked oils and esters, which appeared in the late 80s. XX century, and pure essential oils that entered the market in the early 90s.
The most interesting are oils based on esters. They have very low volatility. These oils are products of various chemical structures derived from both animal and vegetable fats. In addition to low volatility, essential oils are characterized by good tribological properties. Even without additives, they provide friction and wear reduction 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 coolants, but also as lubricating oils. In practice, it is better to use a mixture essential oils and hydrocracking oils, since the tribological characteristics remain high, and their price is much lower.

1.1. Family of multifunction coolants

A decisive step in optimizing the cost of lubricants in metalworking processes was the use of pure oils. When calculating the total cost of coolant, the impact of the cost of lubricants used in metalworking was underestimated. Studies in Europe and the USA have shown that hydraulic fluids are mixed with cutting fluids three to ten times per year.
On fig. 1 these data are shown graphically over a 10-year period in the European automotive industry.

In the case of water-based coolants, the ingress of significant amounts of oils into the 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 cost. When using pure oils, contamination of the coolant with lubricants is imperceptible and becomes a problem only when machining accuracy begins to decrease and equipment wear increases.
The trend towards using pure oils as cutting fluids opens up a number of opportunities to reduce costs. An analysis by German machine builders showed that, on average, seven different types of lubricants are used in each type of machine tools. This in turn raises the issues of leakage, compatibility and cost of all lubricants used. Incorrect selection and use of lubricants can lead to equipment failure, which is likely to result in a production stop. One of possible solutions This problem is the use of multifunctional products that satisfy a wide range of requirements and can replace lubricants for various purposes. An obstacle to the use of universal fluids is the requirements of the standard ISO to hydraulic fluids VG 32 and 46 because modern hydraulic equipment is designed to meet the viscosity values ​​given in these standards. On the other hand, metalworking requires low viscosity cutting fluid to reduce losses and improve heat dissipation during high-speed metal cutting. These inconsistencies in viscosity requirements for different lubricant applications are resolved by the use of additives to reduce overall cost.
Advantages:
. the inevitable loss of hydraulic and break-in oils does not impair the coolant;
. invariability of quality, which eliminates complex analyses;
. the use of coolants as lubricating oils reduces the overall cost;
. improving reliability, process results and equipment durability significantly reduces the overall cost of production;
. versatility of application.
Rational use of universal fluids is preferable to the consumer. An example of this is the engine industry. The same oil can be used in the initial processing of the cylinder block and in their honing. This technology is very efficient.

1.2. Washing lines

In these lines of cleaning operations, water-based cleaning solutions must be avoided to avoid the formation of undesirable mixtures with hydrophilic oils. Solid contaminants are removed from oils by ultrafiltration, and detergents(energy costs for cleaning and pumping water, analyzing the quality of waste water) can be eliminated, which will lead to a decrease in the total cost of production.

1.3. Removing oil from scrap metal and equipment

The correct selection of additives allows the oils extracted from metal waste and equipment to be recycled back into the process. The volume of recirculation is up to 50% of the losses.

1.4. Perspectives on universal fluids - " Unifluid»

The future lies in low viscosity oil, which will be used both as a hydraulic fluid and as a cutting fluid for metalworking. Universal fluid " Unifluid» developed and tested in German research project sponsored by the ministry Agriculture. This fluid has a viscosity of 10 mm2/s at 40°C and performs excellently in automotive engine manufacturing plants for metalworking, lubrication and lines of force including hydraulic systems.

2. Minimize the amount of lubricants

Legislative Changes and Increasing Security Requirements environment also apply to the production of coolant. Given the international competition, the metal processing industry takes all possible measures to reduce the cost of production. An analysis of the automotive industry published in the 1990s showed that the main cost problems are caused by the use of working fluids, with the cost of the coolant playing an important role in this case. The real cost comes from the cost of the systems themselves, the cost of labor and the cost of keeping the fluids in working condition, the cost of cleaning both fluids and water, and disposal (Figure 2).

All this leads to the fact that much attention is paid to the possible reduction in the use of lubricants. A significant reduction in the amount of coolant used, as a result of the use of new technologies, makes it possible to reduce the cost of production. However, this requires that coolant functions such as heat dissipation, friction reduction, removal of solid contaminants be solved using other technological processes.

2.1. Coolant needs analysis for various processes metalworking

If coolants are not used, then, naturally, the equipment overheats during operation, which can lead to structural changes and tempering of the metal, changes in dimensions, and even equipment failure. The use of coolant, firstly, allows heat to be removed, and secondly, it reduces friction during metal processing. However, if the equipment is made of carbon alloys, then 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 coolants (especially due to their ability to reduce friction) leads to an increase in the life of the equipment. In the case of grinding and honing, the use of coolant is extremely important. The cooling system plays a huge role in these processes, as it maintains the normal temperature of the equipment, which is very important in metalworking. Chip removal generates about 80% of the heat, and the coolants perform a dual function here, cooling both the cutter and the chip, preventing possible overheating. In addition, part of the small chips leaves with the coolant.
On fig. 3 shows the coolant requirements for various metalworking processes.

Dry (without coolant) metal processing is possible in processes such as crushing, and very rarely in turning and drilling. But it should be noted that dry machining with a geometrically inaccurate end of the cutting tool is not possible, since in this case heat removal and liquid irrigation have a decisive influence on the quality of the product and the service life of the equipment. Dry processing in the crushing of iron and steel is currently used with the help of special equipment. However, the removal of chips must be carried out either by simple cleaning or by compressed air, and as a result, new problems arise: increased noise, additional cost of compressed air, and the need for thorough dusting. In addition, dust containing cobalt or chromium nickel is toxic, which also affects the cost of production; the increased explosion and fire hazard during dry processing of aluminum and magnesium cannot be ignored.

2.2. Low Coolant Systems

By definition, the minimum amount of lubricant is an amount not exceeding 50 ml/h.
On fig. 4 is given circuit diagram systems with a minimum amount of lubricant.

With the help of a dosing device, a small amount of coolant (maximum 50 ml/h) is supplied in the form of fine sprays to the metalworking site. Of all the types of dosing devices on the market, only two types are successfully used in metalworking. The most widely used are systems operating under pressure. Systems are used where oil and compressed air are mixed in containers, and the aerosol is supplied by a hose directly to the place of metalworking. There are also systems where oil and compressed air, without mixing, are supplied under pressure to the nozzle. The volume of fluid supplied by the piston in one stroke and the frequency of the piston are very different. The amount of compressed air supplied is determined separately. The advantage of using a dosing pump is that it is possible to use computer programs that control the entire workflow.
Since very small quantities of lubricant are used, the supply directly to the work station must be done with great care. There are two types of coolant supply, which are quite different: internal and external. With an external supply of liquid, the mixture is sprayed by nozzles onto the surface of the cutting tool. This process is relatively inexpensive, easy to perform and does not require much labor. However, with external coolant supply, the ratio of the tool length to the hole diameter should be no more than 3. In addition, when changing the cutting tool, it is easy to make a positional error. With internal coolant, the aerosol is fed through a channel inside the cutting tool. The ratio of length to diameter must be greater than 3, and positional errors are excluded. In addition, the chips are easily removed through the same internal channels. The minimum tool diameter is 4 mm, due to the presence of a coolant channel. This process is more costly as coolant is supplied through the machine spindle. Systems with low coolant supply have one thing in common: the liquid enters the working area in the form of small droplets (aerosol). At the same time, toxicity and maintaining the hygiene standards of the workplace at the proper level become the main problems. Modern developments of coolant aerosol supply systems make it possible to prevent flooding of the workplace, reduce losses during spraying, thereby improving the air quality in the workplace. A large number of low coolant supply systems leads to the fact that although it is possible to select the required droplet size, many indicators, such as concentration, particle size, etc., are not well understood.

2.3. Coolant for low flow systems

Along with mineral oils and water-based cutting fluids, oils based on esters and fatty alcohols are used today. Since low coolant systems use flow lubrication oils sprayed into the work area in the form of aerosols and oil mist, occupational health and safety (OHS) issues become a priority. In this regard, the use of lubricants based on esters and fatty alcohols with low toxicity additives is preferable. Natural fats and oils have a big drawback - low oxidation stability. When using lubricants based on esters and fatty acids, deposits do not form in the working area due to their high antioxidant stability. In table. Table 1 shows data for lubricants based on esters and fatty alcohols.

For systems with low coolant supply, the correct selection of lubricant is of great importance. To reduce emissions, the lubricant used must be low-toxic and dermatologically safe, while maintaining high lubricity and thermal stability. Lubricants based on synthetic esters and fatty alcohols are characterized by low volatility, high temperature flashes, low toxicity and have proven themselves in practical applications. The main indicators in the selection of low-emission lubricants are the flash point ( DIN EN ISO 2592) and evaporative loss according to Noack ( DIN 51 581T01). t vsp should not be lower than 150 °C, and evaporation losses at a temperature of 250 °C should not exceed 65%. Viscosity at 40 ° C> 10 mm 2 / s.

For the same viscosity, fatty alcohol based lubricants have a lower flash point than ester based lubricants. Their volatility is higher, so the cooling effect is lower. The lubricating properties are also relatively low compared to ester-based lubricants. Fatty alcohols can be used where lubricity is not essential. For example, when processing gray cast iron. Carbon (graphite), which is part of cast iron, itself provides a lubricating effect. They can also be used when cutting cast iron, steel and aluminum, as the working area remains dry as a result of rapid evaporation. However, too high evaporation is undesirable due to air pollution in the working area with oil mist (should not exceed 10 mg / m 3). Ester-based lubricants are useful when needed good lubrication and there is a large waste of chips, for example, when cutting threads, drilling and turning. The advantage of ester-based lubricants is high boiling and flash points at low viscosities. As a result, volatility is lower. At the same time, a corrosion-preventing film remains on the surface of the part. In addition, ester-based lubricants are readily biodegradable and have class 1 water pollution.
In table. 2 shows examples of the use of lubricants based on synthetic esters and fatty alcohols.

The main considerations when designing coolants for low flow systems are listed below. The main thing to pay attention to when developing coolants is their low volatility, non-toxicity, low effect on human skin, combined with a high flash point. The results of new research on the selection of optimal coolants are shown below.

2.4. Investigation of factors affecting the formation of oil mist in coolant systems with low flow

When a low coolant system is used in the metalworking process, aerosol formation occurs when fluid is introduced into the work area, with a high concentration of aerosol observed when using an external spray system. In this case, the aerosol is an oil mist (particle size from 1 to 5 microns), which has bad influence on human lungs. The factors contributing to the formation of oil mist were studied (Fig. 5).

Of particular interest is the effect of lubricant viscosity, namely the decrease in oil mist concentration (oil mist index) with increasing lubricant viscosity. Studies have been conducted on the effect of anti-fog additives in order to reduce its harmful effects on the human lungs.
It was necessary to find out how the pressure applied in the coolant system affects the amount of oil mist generated. In order to assess the generated oil mist, a device based on the “Tyndall cone” effect, a tyndallometer, was used (Fig. 6).

To assess the oil mist, the tindallometer is placed at some distance from the nozzle. Further, the obtained data is processed on a 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 increases with increasing pressure during spraying, especially when using low-viscosity liquids. A doubling of the spray pressure causes a corresponding doubling of the mist volume. However, if the spray pressure is low and the starting characteristics of the equipment are low, then the period for which the amount of coolant reaches the required rates for normal operation increases. At the same time, the oil mist index increases significantly with a decrease in the viscosity of the coolant. On the other hand, the start-up performance of spray equipment is better with low viscosity fluids than with high viscosity fluids.
This problem is solved by adding anti-fog additives to the coolant, which makes it possible to reduce the amount of fog formed for liquids with different viscosities (Fig. 7).

The use of such additives makes it possible to reduce the formation of mist by more than 80%, without compromising either the starting characteristics of the system, or the stability of the coolant, or the characteristics of the oil mist itself. Studies have shown that fog generation can be significantly reduced by right choice spatter pressure and viscosity of the applied coolant. The introduction of appropriate anti-fog additives also leads to positive results.

2.5. Optimization of low coolant systems for drilling equipment

The tests were carried out on materials used in systems with low coolant supply (deep drilling (length / diameter ratio more than 3) with external coolant supply), on drilling equipment DMG(Table 3)

In a workpiece made of high-alloy steel (X90MoSg18) with high tensile strength (from 1000 N / mm 2), it is required to drill a blind hole. High carbon steel drill SE— a stem with a cutting edge that has a high resistance to bending, coated PVD-TIN. coolants were selected in order to obtain optimal conditions process taking into account external supply. The influence of the viscosity of the ether (the base of the coolant) and the composition of special additives on the service life of the drill was studied. The test bench allows you to measure the magnitude of cutting forces in the direction of the z-axis (in depth) using the Kistler measuring platform. Spindle performance was measured over the entire time required for drilling. The two methods adopted for measuring the loads during a single drilling made it possible to determine the loads during the entire test. On fig. 8 shows the properties of two esters, each with the same additives.

Roman Maslov.
Based on materials from foreign publications.

For good chip evacuation when drilling, coolant must be supplied through the tool If the machine is not equipped with coolant through the spindle, it is recommended to

For good chip evacuation when drilling, coolant must be supplied through the tool. If the machine is not equipped with coolant through the spindle, it is recommended to supply coolant through special rotating adapters. With a hole depth of less than 1xD, external cooling and reduced modes are allowed. The diagram shows the coolant consumption for various types drills and materials. Coolant type Recommended emulsion 6-8%. When drilling stainless steel and high strength steels, use a 10% emulsion. When using IDM drill heads, use 7-15% emulsions based on mineral and vegetable oils for drilling stainless steel and high temperature alloys. Dry drilling It is possible to drill dry cast iron with oil mist through the drill channels. Drill head wear symptoms Diameter change 0 > D nominal + 0.15mm D nominal (1) New head (2) Worn head Vibration and noise increase greatly flow rate Coolant flow (l/min) Minimum coolant pressure (bar) Drill diameter D (mm) Drill diameter D (mm) For special drills larger than 8xD, a high coolant pressure of 15-70 bar is recommended.