Stankoimport 262 horizontal boring machines

Stankoimport 2620 B Service manual for horizontal boring machines The horizontal boring machines, models 2620B, 2620E, 2622B, 2622P, incorporate modern electrical drive with elaborate electrical remote control. The machines can be used for various operations such as boring, drilling, threading, milling, and profiling. The manufacturer reserves the right to introduce minor alterations in the design of the machine's electrical equipment without reflecting them in the present manual. Maintenance and repair of the machine's electrical equipment should only be entrusted to a qualified electrician familiar with the present manual. The rotary motion of the spindle and facing head is derived from a two-speed asynchronous motor. The details not shown in the foundation drawings are prepared and made at the site of installation to suit local conditions. The cross-section of the supply cables must be at least 6 sq. mm at 380, 400 and 440 V supply and not less than 10 sq. mm at 220 V supply.
The total lengths of the cables required are determined at the installation site. The supply wires are connected to the input terminals located on the side wall of the cabinet.
The machine is shipped to the customer dismantled into assemblies, and the external wiring is factory-made and delivered with the machine. The installation of the electrical equipment on the machine before putting it into service is reduced to the connection of wires to the terminal box on the headstock and to making plug-and-socket connections. To earth the machine and its electrical equipment, the machine frame and all electrical equipment must be connected to a suitable earth connection. The motor of the two-speed spindle is switched on by the contactor or in each rotational speed level of the spindle, with the position of the shift lever determining the setting movement. The stator windings are delta-connected only. The adjustment movement takes place while the motor is running at a reduced torque. This is due to the voltage drop across the ballast resistors introduced in each phase circuit of the stator winding. This adds to the smoothness of the spindle motion and reduces the break current at the release of the push-button. The spindle is stopped by a strong reverse-current braking of the motor. The continuous spindle rotation is ensured by the rotating contactor PKC, which rotates simultaneously with the motor shaft when the motor is turned on by the contactor. The intermediate relay is energized when the contact is closed, preparing the spindle for stopping. The tremor current is reduced when the push-button is released. The automatic reversing of the engine causes the wheels to engage smoothly. Usually, 1-2 impulses of the motor will suffice to complete the gear engagement. Once the gear engagement is completed, only one switch remains depressed and the spindle continues to rotate in the same direction at the new speed selected. To prevent the excessive wear of the gear wheels in the process of gear shifting, the impulse reversal of the driver wheels is performed at a very low value of the motor torque since the motor is here connected to the supply network via a ballast resistor in each phase. The order of speed change control operators, the sequence of movements of drive elements, and the performance of the electric circuitry thereat are explained through a cyclogram. The pie is located on a desk, specifically in the lower longitudinal slide housing built into the table in the lower legs of the saddle frame. The motor that turns the table only operates when the button is pressed. The Amplidyne control is managed by push-buttons on the main control panel, and the amplidyne is started and stopped respectively by push-buttons labeled On and Off. A pilot lamp on the main panel glows when the amplidyne is in rotation. To increase the life of the electrical machine bearings and brushes, the amplidyne should be switched off during long interruptions in operation. The protection of the main and auxiliary drives can be seen in the schematic diagram of the main and auxiliary drives in the appendix and in figure 3. The spindle drive motor is protected against short-circuits by a three-phase circuit-breaker with an electromechanical trip and two thermal relays for overload protection. One operates at 1500 rpm and the other at 3000 rpm of the motor. Operating principle of the automatic speed control system for the feed drive motor consists of maintaining the preset speed of the drive motor constant within the required degree of accuracy. The major elements of the electric drive include a DC drive motor with separate excitation, an amplidyne to power the drive motor, a tachometer, a low-output DC generator, an intermediate vacuum-tube amplifier, and a feedback system to ensure required mechanical characteristics of the drive motor within a wide speed control range. The control coupling is obtained with a tachometer negative feedback.

The vacuum-tube amplifier is used to amplify the speed control and flexible reverse connections. It is used in the drive transmission and consists of a two-stage vacuum-tube amplifier. The first stage is a voltage amplifier, and the second stage is for power amplification. The second stage plate load is made up of the high-ohmage control windings of the amplidyne, which are connected opposedly as to the flux set up by the second stage tube plate currents. The resulting flux density is equal to zero if there is no input signal applied to the amplifier. A magnetic voltage stabilizer works as follows: when a signal is applied to the amplifier input, if the signal has a positive polarity, the left grid of the first tetrode will get an increment while the right grid will decrease. Consequently, there is an increase in the voltage drop across the left arm resistance of the plate load and a decrease in the voltage drop across the right arm resistance of the same plate load. The output voltage from the first stage of the vacuum-tube amplifier is picked up by the second stage. In this case, the right grid of the second stage tube is given a positive potential increment while the left grid of the tube receives a negative potential increment. The current increases in the right-hand control winding of the amplidyne and decreases in the left-hand control winding, creating a resulting magnetic flux equal to the difference between the two. The main parallel observation circuits are connected in parallel with the amplidyne. The discharge resistors of the windings are used to prevent the breakdown of the windings in case of overvoltage. The automatic current limiting device for the self-limitation of the feed motor current at starting and braking consists of an independent source of DC voltage, three-phase rectifier, rectifier load resistor, valve bridge circuit, and a resistor in the compensation circuit. The operation of the device depends on the comparison of the voltage proportional to the current in the main circuit. In the compensating winding, a current is created that generates an on-compensated armature reaction flux, causing a voltage drop across the winding. This exceeds the setting value determined by the stabilizer characteristic, and is precluded due to the increase in the demagnetization reaction of the amplidyne device. Therefore, the current-limiting device provides for a speed-up of the feed motor at a constant maximum allowable intensity of main current. Current-limiting adjustment is performed regardless of the direction of rotation. While braking, the current-limiting adjustment is secured due to the magnetizing action of the amplidyne non-compensated armature reaction flux, impressed by the motor counter-electromotive force. The machine incorporates a device intended to prevent generator voltage polarity errors and faults. Feed motor positioning validator Feed motor control switch for adjustment Rapid traverse feed control Feed control switch for traverse Time delay for rapid traverse with tachogenerator Tachogenerator with time delay for feed Breaking stop Figure 11. Feed control diagram 1 Feedback amplifier; 2 electromagnetic clutch engagement circuit; 3 positioning control; 4 feed variator; 5 input signal reversal; 6 forward; 7, 9 rapid; 8 positioning; 10 backward; 11 feed motor excitation; 12 tacho-generator excitation contact for switching on the selected moving member the brakes are disengaged as soon as the moving member gets actuated direction of feed or positioning motion is controlled by intermediate relays. These relays act to change the polarity of the amplifier output. Cutting feed and positioning traverses braking during setting movements braking for setting and feed movements. The feed rate is preset by the variator on the headstock, and the speed of the positioning traverse and the setting movements are selected by the control switch on the main control panel. The required speed for rapid positioning traverses is obtained with the drive by increasing the amplidyne voltage and lowering the motor main pole flux. For this purpose, the coil ends from every other pair of its main poles are led to the terminals of the motor. The flux of one pole pair is completely cancelled when rapid positioning traverse goes on, and the flux of the other pole pair is retained. The operation does not depend on the position of the slides. The motor runs at maximum speed. The speed of the spindle depends on the position control and the variator. The motor braking is accomplished by restoring the motor's field flux. The tacho-generator field flux is also restored, and the motor slows down to its nominal speed. The drive schematics are found in the appendix. The profiling milling is done on the machine with alternating movement of the spindle head, table, and cross-slider. The operating sequence of all devices is shown in the cyclogram. The frame milling can be done with separate movements of the spindle head and table. At the main control panel, there are five main control switches. Accurate positioning for layout based on coordinates. If necessary, the machine can be fitted with precision positioning devices that will assure a fine stop of the headstock and table upper saddle when boring or drilling holes. The boring axes layout is preset by a precise adjustment of stops on the vertical and transverse-longitudinal rules. When the lever projecting from the device comes against the stop on the rule, the shaft inside the device will be moved and will release a retardation microswitch, such as from forced pressure. A relay H-M will be energized through the normally closed contact of the microswitch. The contacts of the relay break the vario circuit and supply the signal from the independent source of voltage to the amplifier input. The voltage size of this signal is such that the speed of the performing motor stops on the machine. The installation settings were switched by the normally closed contacts of the relay. Protection, interlocking, and signaling are carried out in the control circuit of the feed drives. Figure 16 shows the automatic protection of the feed motor with an electromagnetic and thermal circuit-breaker 8A. Starting the feed drive is only possible after 15-20 seconds from the moment the amplidyne is switched on. The time delay for warming the amplifier tubes is secured with a thermal-group. Cutting feed is possible only when the spindle and facing head are in rotation. Hand-wheel operation is impossible when the feed motor is switched on, and starting the power feed cuts out the hand-wheel mechanism. When cutting threads, the power feed cuts out. In accordance with the ratings of safety fuses and thermal relay heating elements, the condition of elements of electrical equipment should be considered from the viewpoint of preparation for operation. This includes the removal of transport fastenings, packing, slushing, and lubrication. Tightness of screw terminals and insulation of electrical machine windings and separate circuits of the schematic diagram that are not connected galvanically should also be checked. Insulation resistance should not be lower than 0.5 MQ for general purposes and not lower than 1 MQ for tachogenerators. The direction of rotation of the amplidyne motor should correspond to the arrow on the amplidyne housing. If the direction is reverse, then the supply phases on the terminals of the input switch should be switched. Finally, safety fuses should be installed and circuit breakers should be tested. The feed of the spindle will only pick up when the spindle is rotating. Check the operation of the travel limit switches and electrical interlocks. Switch on the circuit breaker and check the operation of the optical readouts. Check the operation of the hand-wheel mechanism and the signaling lamps and measuring instruments. Check the drive protection system for integrity. After repair or dismantling of D.C. machines, be careful to check the brushes for neutral setting. Eliminate any difference in speed greater than 50 r.p.m. by adjusting the neutral setting of the brushes through shifting the brush holder yoke in the direction in which the motor armature rotates at a slower speed. The reliability of electrical equipment largely depends on the cleanliness of motors and electrical apparatus. Keeping up cleanliness is of itmost importance to the attending personnel. To assure proper operation of the machine's electrical equipment, it is recommended to keep a record of the repairs, breakdowns, and troubles. In regular service of the electrical machines, care should be taken to prevent penetration of dust and moisture inside the machine, especially onto the windings, dirt accumulation on the commutator, brush arcing, machine overheating, running unlubricated, overheating and abnormal noise, and machine vibration. The load of the motors should not exceed the ratings given below, see Hints to Adjuster. Inspection of bearings and oil replacement should be carried out after 3000-5000 hours. Monitor that the wire leading to the brushes does not rub against the commutator. If the brush edges are found to be burnt too much, check the operation of the automatic current limiter. After long lay-up periods, or repair of the electrical equipment, check the insulation of the winding relative to the frame and between each other. The field windings of 220-volt motors are supplied from the 110-volt control circuit, with the field winding being reconnected accordingly. Rotation of the amplidyne is required only during machining of the workpiece and for positioning traverses of moving members. In all other cases, including interruptions in operation, the amplidyne should be stopped; this will increase the life of the machine, amplification tubes, and rectifiers. Prevent dirt and moisture from getting on the apparatus by periodically examining the contact surfaces and cleaning the gaps between busses and contacts. Measuring instruments should only be switched on for adjustment and checking, and switched off otherwise. A.C. apparatus will operate normally against voltage fluctuations from 85 to 105 of the rated value. If the voltage of the shop mains is too high, causing the coil overheating in the apparatus, necessary measures should be taken to reduce the voltage. See that the armature motion of the electromagnetic apparatus is free, without symptoms of binding or misalignment of the moving parts. With the apparatus being energized, the armature and magnet yoke should make a good contact over the entire surface; failure to do so may require measures to be taken. To observe the balancing resistor axle of the meter display in the VersiI OK, and ensure the plate current is equal to 22 minutes, the balancing may need to be re-adjusted. It is not allowed to operate the machine with removed tubes, as this may result in heavy current flow through the tacho-generator armature and the amplifier input resistors, which can cause protective resistors to burn out at the amplifier input. Therefore, safety precautions must be taken, such as using an insulating stand or floor mat and fastening a warning plate. Before starting the feed mechanism, ensure that no removable handles for manual control are left at the ends of the feed drive and clamp shafts. Access to the contact parts of electrical machines and apparatus must not be adjusted, and the contact parts of the amplidyne set must not be tampered with. When a fault has been discovered in the circuit during one duty, but the cause is yet to be determined, it is recommended to test the performance at another duty to facilitate trouble shooting. Use conventional methods of trouble shooting, such as testing with a probe, control lamp, and measurements. When checking panel circuits, never pull at the wires, and use a control lamp of no more than 8w in power for testing circuits that incorporate telephone relay contacts. If the fault is with A.C. drive control circuits, it is recommended to disconnect the supply wires of the respective motors from the terminals in the electrical cabinet to prevent malfunction of the motors and machine mechanisms while testing individual circuit sections to determine the cause of the fault V11. Gearbox Malfunction and System Failure in Problems with the gearbox and transmission system can have multiple causes and lead to system failure. It is crucial to ensure sufficient lubrication to avoid excessive wear and tear on the spindle key and system. After disassembling or repairing the main engine, the mechanism should not move beyond acceptable limits. Load issues Disconnecting the main drive due to gearbox overload can cause a sudden halt in operation. To prevent this, check the condition and performance of the drive and eliminate any defects. Adequate lubrication for gear drives; insufficient lubrication during disassembly or repair can cause damage. Position 5 of the regulator Electrical faults and abnormalities can cause system failures. Check the condition of the rectifier, semi conductor, and fuse. Engine speed at maximum and minimum settings Imbalances or defects in the lighting system, such as faulty bulbs or poor contacts, can lead to various issues. Balancing and adjusting the axis rotation with variable resistance can ensure proper performance. If balancing the bulb fails, it is better to replace the whole set. Grounding the input of the amplifier to reduce current variations. The ammeter readings may be higher than normal, but the system should not be damaged. Disconnect the input during balancing. Trouble shooting method and remedy. Possible cause Main drive is overloaded Inadequate lubrication of spindle system; defects in assembly of mechanisms after dismantling or repair. Start rotation of spindle at no load and maximum speed. Main motor current should not exceed permissible values on load chart. Main drive is cut off by circuit breaker of pump drive or jamming of pump Inadequate lubrication of gearing or guideways; incorrect assembling after dismantling or repair. Change load current of drive motor after motion without cutting. With varlator set in 5th position, current in amperes should not exceed: Feed Rapid Drive Traverse Headstock upward Table length- 10 Table crosswise 11 Spindle 11 Radial slide 10. Feed rate is too high or low Check to see that input signal voltage corresponds to varlator position. Fault in speed varlator circuit. Creeping motor with drive switching off field killer circuit break or poor contact in generator short separate portions of field killer circuit with temporary jumper. Where faulty section is shorted, motor will stop. Drive starting and breaking are accompanied by thrust arcing above intensity No. 2 and by characteristic hissing of generator Current protection of armature circuit functions upon starting. Check operation of current-limiting device. With drive jammed artificially, watch load. Do not allow load to exceed 21 rated. With varlator set at last position, motor speed is different when running in opposite directions. Different internal resistances of semi-conductor bridge group in current-limiting winding are disconnected. Replace semi-conductor group if speed difference is more than 10 b. No feed revolution, but meter indicates motor overload, but drive can be easily turned by hand field winding Check and reconnect it in accordance with description and wiring diagram after repair or dismantling. Motor shows different speeds in opposite directions Disturbed balancing of fiber or failure of a tube or amplifier unit. Instruments inserted in plate circuit or give different readings when toggle switches are turned into position. Balancing and instruments can be obtained by turning variable balancing resistor axle. In case of failure of amplifier, replace faulty tube with a better whole set. Earthing of amplifier input units Both milliammeters give readings above open-circuit current. Amplifier balancing is effective only with input circuit deenergized. Locate earthed part with a probe and eliminate earthing. Tacho-generator brushes were displaced from neutral in course of dismantling or repair Measure speed and voltage of tacho-generator in either direction of rotation. Ratio of tacho should be the same.  Feed rates are different in opposite directions Replace or repair the faulty parts in the feed drive mechanism. Motor speeds in both directions are limited by resistances in the branches of the three-phase bridge circuit for current-limiting devices when the power is turned off at the last stage of the AC drive. The amplitudes of the windings are different and they balance the speeds. When the speed difference is over 10, the semi conductor groups must be replaced. If there are errors in the feed movements, the ammeter shows the overloading of the connection. However, the drive can be rotated manually. When the button on the control panel is pressed, the feed stops. Failure in the amplifier balancing circuit: various displays of measuring devices in the anode circuit can occur due to tube failure or replacement. By rotating the axis of the variable balancing resistance, the measuring devices show the same values. Damaged tubes must be replaced. Ground fault in the current circuits at the amplifier input: both milliammeters show higher values than the idle currents. The amplifier can only be balanced by turning off the input circuit. Ground faults can be detected by means of a line tester and eliminated. During disassembly and repair, the brushes of the tachometer generator were displaced from the neutral position. The speed and voltage of the tachometer generator must be measured during the rotation in both directions, and the ratio should remain the same.  The feeds are different in different directions. The speed is higher in one direction and lower in the other. When one of the tubes in the amplifier fails, one of the milliammeters does not show any display, and the tube must be replaced.