Method of control over metal cutter high-rpm direct drive spindle motor. RU patent 2509627.

FIELD: process engineering.

SUBSTANCE: proposed method comprises fitting the spindle in machine spindle assy housing and clamping by flange to run in front and rear bearing assemblies. Note here that channels are made in said housing and flange to coo down spindle assy elements. To increase service life, temperature is additionally controlled by temperature transducers arranged nearby bearing outer races. Vibration is controlled by vibration gage arranged in the housing nearby spindle front bearing assy. Spindle axial displacement is controlled by appropriate pickup arranged at spindle front end. Readings of said transducers are used to cur off drive motor in due time in case allowable load falls beyond tolerances.

EFFECT: longer life.

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The invention relates to the mechanical engineering, in particular, for machine tools.

Known way to improve the performance of the motor spindles of metal cutting machines by the wide use of mechatronic modules, combining energy, information and control functions within a single structural unit, which ensures a consistent choice of parameters of separate subsystems to achieve the required performance characteristics (Bushuev V.V., Sabirov FS directions of development of the world machine-tool construction. - M: Vestnik MGTU "Stankin", №1(9), 2010, p.24-30).

The closest technical solution to the claimed object is spindle unit of metal-working machine, which contains the motor, the rotor is installed on the shaft, while the spindle is installed inside spindle Assembly of the machine and fix through flange with the possibility of rotation in the front and rear bearing. To improve performance spindle create additional cooling of the front bearing by means of execution in the case and in the flange channels (EN 112656 U1 20.01.2012).

The disadvantage of technical solutions is relatively low performance motor-spindle as a result of insufficient regulation of its work during operation.

The technical result, which directed the claimed invention is increase of a resource of operation of high-speed motor-spindle (VMS) through the provision of timely switching off the engine by means of the equipment and the location of appropriate control sensors.

Specified the technical result is achieved by control of high-speed motor-spindle, machine tool, which contains the motor, the rotor is installed on the shaft, while the spindle is installed inside spindle Assembly of the machine and fix through flange with the possibility of rotation in the front and rear bearing, housing and flange perform channels for cooling elements spindle Assembly, according to the invention, additionally carry out: control of temperature in the zone of the bearing through sensors temperature, which set near the outer rings of the bearings; vibration monitoring with the help of a shock sensor, which is installed in the chassis near the front spindle bearings; control of axial displacement of the spindle with the help of sensors installed on its front end, which together functionally provide timely off the motor in excess of the permissible load.

The claimed invention is illustrated by drawings, where:

- figure 1 presents the structure of the main subsystems VMS for metal-cutting machines;

- figure 2 - scheme of the tool clamping mechanism;

- figure 3 - installation of bearings in VMS;

- figure 4 - schematic-based VMS on the machine.

System to implement the process includes two blocks subsystems: basic, built-in WMS, subsystems and additional serving VMS subsystem (figure 1).

Basic, built-in WMS, subsystems include motor spindle bearings, the sensor position feedback mechanism tool clamping, spindle to base surface for installation tool, a sub-feed coolant (coolant) with both internal and external her podvodni in the cutting zone, and a subsystem of diagnostics.

Additional serving VMS, the subsystem includes the following subsystems: the engine cooling, cooling of bearings, lubrication bearings, creating interference fit in bearings, protection pillars of dust, cleaning tool cone, and control system.

System for realization of the claimed process works as follows.

In spindle site Metalworking machine there are two subsystem block: basic, built-in WMS, subsystems and additional serving VMS subsystem, and then carry out the optimal synthesis of these subsystems.

Figure 1 shows schematically the main subsystems designed VMS. On request of the customer can range: type of lubrication of bearings (grease or airborne grease), create a preload in the bearings (permanent by springs or adjustable pneumatic cylinder, when roughing operations), control system, circuit coolant (internal, external or both), the diagnostic level (mandatory level - monitoring of the motor temperature and poles).

Subsystems VMS.

The motor spindles includes two subsystems: built in a single structural unit (actually motor-spindle) and service subsystems which are installed in close proximity to VMS. Some of them, for example, the lubrication system can be chosen depending on desires of the customer and the required output parameters, as provided in the construction of motor-spindle.

Design features VMS.

All VMS range designed by the unified constructive scheme with some differences related to peculiarities of separate subsystems and conditions VMS.

Used motors. Using synchronous motors F. "Siemens". Losses in the conversion of electrical energy into mechanical occur mainly in the motor stator installed in case VMS. Therefore, the stator is equipped with a cooling system. Provides cooling system, which is installed near the machine and is used as heat water with anti-corrosion additives.

The required heat dissipation must exceed the power losses and is expected to be not less than (0,1...0,2) P nom , where P nom - nominal power of the motor. More accurate parameters losses are set by the suppliers of electric motors.

In the frequency range up to par nom speed - developed power increases in proportion to the number of revolutions, and the time - maximum. At the rotating frequency range from n to m EBM max torque is reduced, but has constant power.

Permissible load. High-speed bearings are very sensitive to congestion, especially in the absence of rotation, due to the deterioration of lubrication. Overloading can be associated with power impacts during installation and in collisions of nodes, tool breakage and assigned to incorrect processing modes. With advanced diagnostics VMS able to minimize the negative impact of possible overloads.

Durability supports. Bearing life largely depends on the correct functioning of the lubrication system, as well as from the dust content of the air in the area of their location. Therefore provides a continuous air flow under low pressure in the cavity labyrinth seals 21 (see below Fig.5). Load and speed also have an impact on durability, however, calculation of durability of bearings for typical technological regimes showed that when grease design longevity, not taking into account the conditions lubrication, 5...6 times larger than the actual, limited according to literary data 20000 hours (determined durability greases).

Lubrication of the bearings. For lubricating bearings are used or grease (plastic) grease, which fill the bearing in the Assembly, or airborne grease, if you want to get the maximum frequency of rotation of a spindle. In this case, it is about 1.5 times higher than in plastic grease. Drops of oil served with the air flow directly into the contact area from the special plant, located in close proximity to VMS. The used lubricant is continuously removed from the bearing.

Cooling system supports. During operation, the bearings are heated, which decreases their health. So provide them cooling. Uses a single engine cooling system and bearings. Research has shown that the share of heat discharged through external and internal bearing rings, is approximately 75% and 25%. Change of coolant flow through the support VMS with HSK-A100 from 5 to 7.5 l/min little effect on the bearing temperature (the temperature difference of about 1 degree C). Spring-loaded bearings, installed in the "floating" Bush have a temperature greater by 5-10 Celsius C than bearings, installed stationary.

Base frame with the tool. Unlike traditional machines with the parameter speed spindle n·d m order (0,6...0,75)·10 6 mm/min, (where d m - bearing mean diameter in front leg, mm)in VMS to install and based tool holder uses a short cone (1:10) and end (connection type HSK-A according to GOST R 51726-2001 and GOST R 51747-2000).

Replacement is connected with the fact that at certain engine speeds from the action of centrifugal forces occurs a significant change radial dimensions boarding cones of the mandrel and the spindle. In this case, in the absence of an end face (as in conical connection type 7:24 according to GOST 24644-81) axial position of the tool is changed, because the pot is delayed spring clamping mechanism inside the spindle. This lack is eliminated in the connection type HSK-A cone and the end.

Based on the cone and the face you want to make the frame and spindle with small deviations from each other in size cones, as well as with certain regulated gap (HSK-A100 about 60...170 microns) between the ends of the mandrel and the spindle in the free state. It is technologically much more complex than basing only on the cone.

The mechanism of the clip frame of the instrument. Distinctive features of the clamping mechanism in VMS associated with the action of centrifugal forces that reduce the effort of a clip. In addition, to improve the reliability provided not power and geometrical circuit clamping forces on the spindle. The design of the mechanism of the clamp must be extremely compact, as all subsystems are integrated into a single mechatronic module.

Figure 2 shows the principal simplified scheme of clamping mechanism VMS that implements these features.

Pot 1 is set in the spindle 2 at left (down) position thrust 3, where Cams 4 does not interact with the mandrel. After installation mandrel in the spindle thrust 3 under the action of springs (Fig.3 not shown) is moved to the right and through the gland 4 affects Cams 5. Cams in contact with conical surfaces 6 mandrel and 7 spindle, thus giving a positive locking clamping forces between 8 and end surface 7 spindle.

When clamping thanks to the conical surfaces 9 and 10 of the sleeve and push Cams angle cones equal to 20 degrees force spring affecting the pot increases up to 3 times in comparison with spring force F SAG . At higher frequencies of rotation of a spindle of the centrifugal force acting on Cams, increases and the contact pressure between the conical surface of the mandrel and the spindle is reduced. As a result, the force of interaction between the ends of the mandrel and spindle increases by the square-law (HSK-A100 about 25% at maximum speeds (about 15,000 rpm)) in relation to the effort provided by springs.

Clamp mechanism can be a significant source of imbalance occurs spindle due to a change in the relative position of the disc springs in the brakes and the clip frame. The design of the clamping mechanism takes into account operational features high-speed spindle bearings that have a valid static load is often less than dynamic. Force at unclamping of tools is not transferred completely to the bearings, and closed mostly within the mechanism.

To monitor the status and functioning of the tool clamping mechanism provided with appropriate sensors. When setting up and consolidation of the new mandrel conical surface spindle is cleaned with compressed air.

Figure 3 presents the scheme of installation of bearings in VMS.

Spindle bearings. Very responsible in VMS are spindle bearings and their installation. For all sizes VMS used hybrid ceramic bearings FAG (steel rings, rolling elements of ceramic). The increasing speed of these bearings is achieved, first of all, due to decrease of centrifugal forces, and therefore the frictional forces acting on the rolling elements due to their lower (approximately 2.5 times) than that of steel density. The used scheme of installation of the bearings in the range VMS shown in figure 2.

In front leg used angular contact ball bearings 11. Rear mounted single-row cylindrical roller bearing 12, tightness in which is installed in the Assembly by displacement of the inner ring of the bearing with a tapered surface. When thermal expansion of the spindle his rear end is easy to move due to the absence of axial fixation of the rollers in the outer ring of the bearing. Since VMS with HSK-50A, in front leg installed dual bearings.

Clamped in front leg adjustable springs 13, regardless of the load and thermal phenomena. The magnitude of the interference fit is selected in accordance with the recommendations of the bearing manufacturers. In particular VMS with HSK-A100 value of tightness around 1600 N. At speeds less than 0.5 n max , and also at high loads tension can be increased with the help of a pneumatic cylinder 14 (approximately 1.5-fold) when the supply air under the appropriate pressure.

Figure 4 presents a scheme based VMS on the machine.

1) based and retaining VMS in spindle grandmother should strive to eliminate redundancy, which can appear deformation and additional load on the bearings.

2) due to the residual imbalance of spindle and tools for bearings valid variable power. Residual imbalance causes angular f 1 and radial f 2 fluctuations.

3) headstock must be tough enough in the whole range of frequencies of rotation of a spindle had no coincidence frequencies grandmother and spindle. Her lowest resonance frequency should not exceed the maximum excitation frequency is f max =k·n/60 Hz, where k and n is the number of teeth and the speed tool to limit processing mode.

Basing VMS (figure 4) is performed on a cylindrical 15 and 16 mechanical surfaces. The nodes of small dimensions are based only on the cylindrical surface. The cylindrical surface of 15 is a very extensive, allowing to increase the rigidity and resonance frequency of f 1 except to provide front rear 17 bearing housing VMS, which has a positive impact on the dynamic characteristics of spindle head. The mounting flange must be sufficiently thick and rigid connection with the case.

Supply of lubricating-cooling liquid (GM). In the cutting zone coolant may be submitted in two ways: external coolant through nozzles mounted on the front end of the motor spindle and the internal coolant supply through the rotating spindle, directly to the cutting zone. Coolant is done through the Central hole in the thrust of clamping mechanism. To exclude leaks are provided with appropriate seals.

Systems of condition diagnostics VMS. Provides:

1) the Control temperature of the motor and the spindle bearings. Temperature sensors installed in the immediate vicinity of the outer rings of the bearings. When the temperature is above the permissible stop the spindle. The temperature sensors of the supports can also be used to monitor the functioning of bearings on basis of statistical information, establishing the relation between the operating conditions (speed, duration, and others) and their temperature.

2) Control the vibration VMS using vibration transducer installed in the case near the front support the spindle. If the customer data maximum allowable levels of vibrations on the specific operations (e.g., the amplitude of oscillations at certain frequencies) can very effectively manage the process of cutting at the expense of regime change. The connection to the vibration sensor mobile diagnostic systems allows to detect incipient defects in bearings and monitor their condition.

3) the Control of axial displacement of the spindle is produced by the sensor mounted on the front end VMS. The offset can be caused by stress from cutting, collision VMS with the workpiece, heating spindle, different spindle speed resulting from the centrifugal force is changing position of the contact spot in the bearings. Information about the position of the spindle can be used to improve efficiency VMS (disable VMS in collisions, accounting control program axial movement of the tool to increase the accuracy and the like).

Control system VMS as part of the machine.

Management by numerical control machine provides the required parameters of rotation of a spindle, work subsystems VMS (Pneumatics, cooling, clip-unclamping of tools and so on), automatic tool change, assessment of the results of diagnostics, etc.

Installing VMS on the machine.

The motor spindles can be installed in horizontal, vertical and inclined provisions. VMS integrated into the structure of the machine, so the static and dynamic characteristics should be agreed between VMS and spindle head. When designing spindle stock consider the following features:

Operational features.

The speed control. For VMS is very dangerous to exceed the maximum speed of the spindle or instrument (turns off), which is determined, first of all, the state of the tool and processing modes. When it is exceeded, the spindle stops.

Achieving high frequencies of rotation. Feature WMS is different than in conventional machines, the algorithm of reaching high speeds, due to the need of heating supports. As a rule, in the dispersal of a spindle up to speeds close to the maximum, provides for the warming up of spindle bearings within 2 to 3 minutes at speeds that make up (0,25-0,5-0,75) n max . The algorithm warming is built in the software of the machine. Similarly (but longer time up to 5...6 minutes) is made warming VMS during his long stop (over a week).

Maximum angular acceleration in the dispersal of the spindle. At high accelerations (small acceleration time) can cause thrashing of rolling element bearings, which negatively affects their durability. It is advisable to set the acceleration in which the acceleration will not exceed 500 1/2 .

The rigidity of the spindle-tool. At work affects the rigidity of the spindle Assembly, and the rigidity of pots and tools. In most cases, the rigidity of pots and tools are much smaller than the rigidity of the spindle Assembly.

Axial displacement of the shaft. Axial spindle shift caused by temperature deformations at warming up of spindle to the steady temperature and the centrifugal forces at different speeds, resulting in the displacement of the contact spot rolling elements with rings. To reduce the effect of axial movement of the spindle on the accuracy you can introduce corrections into the operating program for sensor signal the axial position of the spindle.

The choice of instrument. Only quality tool provides low vibration, low noise, personnel safety, durability of bearings. The tool should have the same precision and should not reduce the natural frequency of the spindle below critical, equal to the maximum excitation frequency f max , cutting forces and the weight of the instrument must not cause overloading of the bearings. The resonance frequency of the spindle and spindle mandrel must be higher than the frequency, due to valid rpm tool. Especially strongly on the reduction of resonant frequencies are affected: dimensions (length, diameter and weight of the mandrel and the tool. The necessary balancing tool with a large residual unbalance.

Static and dynamic characteristics VMS. At high speeds static and dynamic characteristics crucially determine the efficiency VMS. Avoid resonance phenomena, when the frequency of the perturbation approach eigenfrequencies VMS.

The tool has a determining influence on the dynamic quality VMS. The first natural frequency of the system spindle-snap for most operations are in the field...700 600 Hz, which allows to state that the most common modes are outside resonance zones.

The main parameters VMS.

The main parameters, such as power and torque of the engine, speed, valid forces were appointed on the basis of the analysis of modes of processing of steel and billet aluminum face, long edge, end, disk cutters and boring, drilling and retinoblastome tools (drills, reamers, cutters etc). As a material tool was used carbide and ceramic. When choosing a treatment modes took into account the fact that overclocking above certain speeds in conical connection cable and spindle may occur gap that should be excluded. The main parameters of the developed under government contract VMS presented in table 1.

The way to improve the performance of high-speed motor spindles for machine tools is as follows.

1. There are two subsystem block: basic, built-in WMS, subsystems and additional serving VMS subsystem.

2. The Main subsystems include: motor spindle bearings, the sensor position feedback, the tool clamping mechanism, the spindle to base surface for installation instrument subsystem feed coolant (coolant) with both internal and external her podvodni in the cutting zone, and a subsystem of diagnostics.

3. Additional subsystems include: engine cooling, cooling of bearings, lubrication bearings, creating interference fit in bearings, protection pillars of dust, cleaning tool cone, and control system.

4. Perform calculations and analyze the model cutting, static and dynamic characteristics, the influence of working conditions of the site (including engine speed) on the contact stiffness of the joint spindle - arbor-type HSK-a tool clamping mechanism and thermal phenomena in the bearings.

5. Determines the load generated by typical for this class of spindles technological operations.

6. Based on the capabilities of the basic and auxiliary tools, establish the specifications of maximum permissible modes of treatment. For limit for each operation modes of cutting assess the characteristics of the main motion drive, reaction forces and the lifetime of the bearings.

7. Analyze rigidity and dynamic as the spindle Assembly with the use of software for finite element modeling "GSP", developed at the Department "Machines" MSTU "STANKIN". Resulting receive information on the size of the static deformation spindle Assembly for typical technological operations and to provide estimates of its distribution between the structural elements.

8. Analyze the dynamic quality by building amplitude-frequency characteristics (AFC) of the point tool holder, located in the cutting area, and set the mode shapes spindle Assembly on the lowest natural frequencies. These data are judged on the value and character of oscillations of construction on their own frequencies that are within the operating frequency range of the institution or in its immediate vicinity.

9. Calculates connection spindle - instrumental pot when rotating and assess the impact of speed on the performance of clamping mechanism and limit the speed at which the connection is losing its performance. Calculated design (figure 2) included the front part of the projected spindle with tool cone type HSK, instrumental mandrel and Cam clamp mechanism. Calculations and analysis were performed in the environment of finite element modeling, Simulation, CAD-integrated system "SolidWorks". The calculations were carried out at various speeds, from zero to maximum for a given size of the connection. The results of the calculation are the displacement caused by the deformation of the spindle, tool holder and clamping mechanism and reaction on the mating surfaces of individual parts of the structure.

10. Examine the operational connection properties spindle - instrumental mandrel under action of external loads was to assess its load carrying capacity and stiffness. Calculation model, as in the previous case, included the front part of the projected spindle with tool HSK-A and instrumental frame. The calculation was made in the environment solid modeling Simulation. The calculation results are displacements, deformations caused by spindle mandrel and slippage in the joints connection, the reaction in the joint elements, plots of pressure on the mating surfaces.

Compared with traditional spindle units of machines, VMS is more intensity thermal loads. They are caused by the concentration of powerful heat sources (motor spindle bearings) inside the compact design of the site. High concentration of heat sources requires intensive cooling how to keep the site (which is defined permissible temperature of the motor windings and bearings bearings)and excluding thermal impact on the surrounding design elements that causes the reduction of precision because of their temperature deformations.

Temperature limit spindle bearings and windings of the motor depends on the performance of the cooling installation, how are distributed by flow between shirts cooling and on the intensity of heat shirts, i.e. from the design.

Such heat calculations are almost impossible to perform analytical methods because of the complex geometry shirts cooling. With the application "FlowSimulation" SolidWorks intended for simulation of dynamics of liquid and gas, transport phenomena of heat and mass transfer, has been developed a mathematical model that takes into account radiation and convective heat transfer case motor-spindle with the environment. Due to the fact that the bearing heat (because of a change oil viscosity) depends on temperature, which is not known in advance, then the power of heat sources in the models were asked in the form of functional dependences on temperature holes bearing outer ring. The decision of tasks in "FlowSimulation" is carried out by the method of finite volumes.

11. Carry out the computational experiments on mathematical teplotehnicheskoj model: define the balance of the flow of water through the cooling jacket (front support, engine, rear foot) when the variation of the total consumption; calculated the balance of heat flows in rotating the bearing outer ring which is placed in the water jacket cooling; determined the temperature of the outer rings of the most loaded in the heat respect, support and recommendations on the appointment of the flow of water through the cooling jacket to ensure the health of her bearings; evaluated the performance of the pump and excessive pressure in the line discharge for the subsequent choice of the cooling system.

In the result of the work performed the necessary theoretical and engineering preparation of development and serial production in Russia high-speed motor spindles for almost all sizes of machines, drilling-milling-boring group.

The way to control high speed motorthe spindle of the machine tool, containing a motor, the rotor is fitted on the shaft, where the spindle is installed inside spindle Assembly of the machine and fix via a flange with the possibility of rotation in the front and rear bearing supports, in the case and in the flange perform channels for cooling elements spindle Assembly, wherein the additional control temperature with temperature sensors, which are mounted near the outer rings of the bearings, control of vibration level with the help of vibration transducer, which set in a building near the front support of the spindle, and the control of axial displacement of the spindle with the help of sensors installed on its front end on the totality of evidence shall be performed by timely off the motor in excess of the permissible load.