Lathe electric drive

Contents

CONTENTS

PAPER

LIST OF GRAPHIC DOCUMENT SHEETS

INTRODUCTION

1. DESCRIPTION OF MACHINE AND PROCESS DESIGN

1.1 Basic Technical Data

1.2 Machine Design

1.3 Description of kinematic diagram

1.4 Process Description

1.5 Some data of machine technical passport

2. REQUIREMENTS FOR ELECTRIC DRIVE

2.1 Requirements for NC Machine Electric Drives

2.2 Requirements for electric drive of main motion

2.3 Requirements for Feed Drives

3. POWER CALCULATION AND SELECTION OF ELECTRIC DRIVE SYSTEM

3.1 Power calculation and selection of main motion drive

3.2 Construction of load diagram and tachogram for master drive

movements

3.2.1 Engine check by heating and G-load

3.3 Calculation and selection of feed motors

3.3.1 Selection principle

3.3.2 Longitudinal transmission

3.3.3 Transverse transmission

3.4 Construction of load diagram and tachogram for feed motors

3.5 Determination of anchor circuit parameters

3.6 Analysis of dynamic properties of electromechanical converter

as a management object

4. DEVELOPMENT OF AUTOMATIC CONTROL SYSTEM. DYNAMIC CALCULATIONS

4.1 Requirements to ACS

4.2 Complete electric feed drive type

4.2.1 Block Diagram of the Supply Package Electric Drive

4.2.2 Non-linear link and functional converter of EMF

4.2.3 Characteristics switch

4.2.4 Dependent current limitation unit

4.2.5 Power part

4.3 Calculation of parameters of the mathematical model of the power part of the valve converter

4.4 Thyristor converter as a component of automatic control system

4.5 Setting of current and speed regulators

4.6 Calculation of automatic control system of main motion drive

4.6.1 Calculation of main circuit model parameters

4. DEVELOPMENT OF AUTOMATIC CONTROL SYSTEM

4.1 Requirements to ACS

4.2 Calculation of main movement ECS

4.2.1 Structure of the drive control system

4.2.2 Base values

4.2.3 Calculation of parameters of control objects

4.2.3.1 Armature circuit

4.2.3.2 Excitation circuit

4.2.4. Selection of uncompensated time constant Tμ

4.2.5. Development and modeling of current ECS

4.2.6. Consideration of EMF influence of engine armature

4.2.7. Development and modeling of speed ECS

4.2.8 Development and simulation of excitation current ECS

4.2.9 Development of EMF ECS

4.2.10 Development of magnetic flux regulator

4.2.11 Development and modeling of intensity setter

4.2.12 Simulation of the system

4.3 Calculation of EE ECS

4.4. Implementation of ATS

5. NUMERICAL SOFTWARE CONTROL SYSTEM

5.1 NC Systems for Metal Working Machines

5.1.1 ECC Functions

5.1.2 ECC operation modes

5.1.3 Machine coordinate system

5.1.4 Control Program

5.1.5 Main Advantages of CNC Machines

5.2 ECC NC-

5.2.1 CNC Device NC-

5.2.2 Technical characteristics of ECC

5.2.3 Composition of ECC

5.2.4 Installation procedure, preparation for operation, operation procedure of ECC

6. TECHNICAL AND ECONOMIC JUSTIFICATION OF THE PROJECT

6.1 Necessity of modernization

6.2 Calculation of capital investments

6.3 Determining the Annual Economic Impact

6.3.1 Energy Costs

6.3.2 Depreciation deductions

6.3.3 Repair Cost

6.3.4 Reduction of wages of the main workers

6.4 Determine Payback Period

6.5 Conclusion

7. PROJECT SAFETY AND ENVIRONMENTAL FRIENDLINESS

7.1 Introduction

7.2 Harmful and dangerous factors

7.2.1 Equipment Requirements

7.3 Safety

7.3.1 Electrical safety measures

7.3.2 Noise

7.3.3 Vibration

7.4. Microclimate

7.5. Environmental friendliness

7.5.1. Harmful substances in the air

7.5.2. Ventilation

7.6. Emergencies

7.6.1. Fire safety

7.6.2. Possible emergencies (emergency)

7.6 Output

8. PROSPECTS FOR THE DEVELOPMENT OF METAL CUTTING MACHINES

8.1 Improving Performance

8.2 Improving Accuracy

8.3 Machine Readability (Flexibility)

8.4 Improving Reliability

8.5 GPM Implementation

CONCLUSION

BIBLIOGRAPHIC LIST

1.2. Description of kinematic diagram

Main drive

The drive from the motor to the spindle shaft is carried out by means of a speed box having three speed ranges switched by CNC NC210 according to the control program. The speed box includes five shafts included in one way or another, depending on the range. The transmission of rotational motion from the motor to the shaft I is transmitted by means of a belt.

I range

From shaft I, movement is transmitted to shaft II through a gear train (gears 1 and 2) with a gear ratio of i = 1.0; further to shaft III with gear ratio i = 1.0; (gears 3 and 4). From shaft III to shaft IV with gear ratio i = 0.36; (gears 7 and 8) and finally from shaft IV to shaft V by means of gears 9 and 11, gear ratio i = 0.5;

Fig.1.1 shows the inclusion on the I band.

II range

The movement to shaft II is transmitted in the same way as I range, from shaft II to shaft V through a gear train (wheels 5 and 10) with a gear ratio of i = 1.25;

III range

The movement to shaft II is transmitted in the same way as I range, from shaft II to shaft V through a gear train (wheels 6 and 11) with a gear ratio of i0.5;

Gears 10 and 11 are combined and secured to the shaft depending on the range by means of a sliding key.

The information on the rotation angle V of the shaft is taken from the feedback sensor DP LIR 2, which receives rotational movement by means of a gear transmission through gears 11 and 12 with a gear ratio i = 1.0 .

Longitudinal transmission

Rotation from the motor shaft is transmitted through a gear train (gears 20 and 19) with a gear ratio of i = 3.0; to helical ball pair of longitudinal displacement. Information about the turn angle is taken from the feedback sensor of LIR PD 2.

Movement in electric drive (kinematics) of transverse motion is transmitted in the same way.

Kinematic diagram is shown in Figure 1.2.

1.5. Some data of machine technical passport

The technical certificate of the machine contains instructions for operation.

For the lathe model 16K20PFZ, they are as follows:

1. The machine is designed for use in machining workshops.

2. The temperature in the premises where it is set should be within + 15... + 40 С.

3. Relative air humidity is not more than 80%.

4. Dust content of the room within the sanitary norm (6 mg/m3).

5. The machine shall not be subjected to local heating or severe temperature differences.

6. Near the machine there shall be no grinding machines operating without cooling, large diving equipment. Devices installed near the machine using high frequency currents shall be protected against radio interference.

7. In the premises for installation of the machine, it is necessary to lay a bus connected to the low-resistance grounding loop to connect the grounding wires of the machine.

8. The CNC machine is connected to a three-phase AC network of 380 V and 50 Hz.

9. To protect against electrical interference caused by the operation of other electrical equipment, it is recommended to power the NC from a separate motor generator, to which it is not allowed to connect machines without NC or other equipment.

10. Sufficient space shall be provided for convenient cleaning of the machine from chips and its timely removal.

11. The machine shall be installed on the foundation.

12. Lubrication of the machine shall be performed with the oils specified in the operating manual.

13. Do not use liquids with aggressive impurities to cool the tool.

14. Persons trained for NC machine work and safety training shall be allowed to work, set up and maintain the CNC machine.

2. requirements for electric drive

2.1. Requirements for NC Machine Electric Drives

The requirements for electric drives are determined by the processing technology, the design features of the machine, the cutting tool, and the functionality of the NC system. The main technological requirements are to provide: the necessary technological processing modes using a modern cutting tool; maximum performance; required processing accuracy; high purity of the treated surface (reduced roughness); Repeatability of part dimensions in machined lot (stability).

The requirements for machine drives are determined mainly not by the group to which the machine belongs, but by the movement for which the drive is intended: main movement, supply or auxiliary, since this determines the power and moment, speed control method, control range, requirements for dynamic characteristics, for rigidity of mechanical characteristics and speed stability.

Expansion of processing modes on one machine using modern cutting tool has led to complication of installed electric drives, increase of installed power of engine of main motion, rotation moments of feed motors, expansion of ranges of control of speed of main drive, working feed and setting displacements, increase of speed of all drives under control and disturbing action, tightening of requirements for stability and uniformity of rotation of electric motors of all drives.

The demand for increased performance also led to an increase in the power and maximum speed of the main movement drive; to increase speed of fast travel of feed drives; increase of maximum working feeds; reduction of acceleration and braking time; positioning of feed and auxiliary drives and spindle orientation.

Meeting the requirements for reducing roughness and improving accuracy during processing and positioning tightened the requirement for electric drives by the value of errors in steady and transient modes under various disturbing effects, to expand the control range and increase the sensitivity of electric drives to the load by increasing the uniformity of movement, especially at low speeds, to increase speed during disturbance, at load and at reverse under load at low speed.

In order to ensure repeatability of the dimensions of the part in the machined lot and high accuracy of positioning, it is necessary to have a highly stable drive with high uniformity of movement and aperiodic transition process when the speed changes.

A very important requirement for CNC electric drives, especially when working in automated manufacturing, is to ensure their high reliability - both regarding the preservation of parameters and accident-free and repairability. The availability of technological reserves on parameters of individual electronic elements and circuit solutions, timely implementation of preventive measures and installation of the necessary diagnostic system that allows quick detection and elimination of malfunctions contribute to the increase of reliability of electric drives operation [1].

2.3. Requirements for Feed Drives

The creation of multi-operation machines and the development of high-strength and fast-cutting tools ensured the possibility of milling, turning, drilling on one machine. This required an increase in the torque on the shaft of the actuator motor, an expansion of the range of working feeds and installation movements, an increase in the speed of the drive both under control action and under load disturbance. The need to meet these requirements has led to a change in the design of the supply drives and the use of special engines in them.

The simplification of the kinematics of the feed mechanisms in turn caused a decrease in the reduced moment of inertia of the drive. As a result, engine loads during idle movements decreased, and the component cutting force in the total drive load in the working mode increased. The latter increased the load fluctuation on the electric drive, which tightened the requirements for its static and dynamic stiffness. Requirements for quality parameters of control of feed drives are formed in accordance with the need to ensure maximum productivity, highest accuracy of development, low roughness of the treated surface, high accuracy of positioning of machine working elements and stability of dimensions of the batch of processed parts.

On machines with a large number of installation movements and a small screw stroke, not so much the absolute speed of fast travel is important as the speed of the drive and the NC system.

However, the increase of accelerations increases the loads in the mechanical part of the drive, the permissible level of which is limited by its strength characteristics. The NC system type also limits the minimum acceleration and deceleration times of the drive. This is due to the limitation of the maximum amount of mismatch that the system can work out without losing information.

Therefore, the speed of the feed drives depends on the gear ratio and the characteristic of its mechanical part, the maximum frequency and discreteness of the control signal supplied from the CNC system and the limit misalignments worked out by it completely, the maximum rotation speed of the actuating engine and the gain in speed of the servo drive. At linear acceleration of servo drive to maximum speed of fast stroke Ubx dynamic error d is proportional to speed of fast stroke Ubx and acceleration time tp. With a small amount of working movement and insufficient speed of the drive, the motor may not have time to accelerate to its maximum speed. Therefore, the value of tp on machines does not exceed 0.2s. However, in feed drives, not only the time of transients is limited, but also the nature of the movement itself. The most favorable is the aperiodic law of changing the output coordinate, which eliminates the opening of joints in mechanical units, impact overloads. When positioned, this type of motion provides an approach to a given coordinate always on one side.

In the driving mode with a constant steady speed Uy, the speed error C = Uy/kU, where the Q-value of the tracking drive is kU.

The level of the kU value is determined by the actuator design and is within 1050c1. The Q-value kU can be increased to 3008001 by introducing a rate error compensation signal proportional to the rate of change of the control action into the system.

The measuring devices in the NC system shall provide large measurement ranges at small values of permissible error, so the resolution and accuracy of the position sensors shall be significantly higher than the permissible accuracy of the test. With linear performance, all elements of measuring devices must have high reliability, low inertia and low friction moments.

Unsatisfactory properties of the feed drive, especially in case of load disturbances, lead to an increase in the roughness of the workpiece. Therefore, it is necessary to achieve high speed of the drive in conditions of reset and load surge with a wide range of control, as well as in conditions of engine reversal under load at the lowest speeds of rotation.

The development of noise-resistant systems capable of reliably performing their functions in workshop operation is gaining special activity in the conditions of an increase in the level of automation of production and the introduction of waste-free and low-waste technology. One means of increasing reliability of equipment is improving its repairability. In this regard, a high degree of unification of units and individual elements of feed drives is required, their equipment is equipped with diagnostic devices, easy adjustment and maintenance.

The stability of the positioning and dimensions of the machined products on CNC machines depends on the stability of the characteristics of the feed drives, position sensors and the NC system. With a sufficiently large gain, the stability of the characteristics is mainly determined by the stability of the parameters of the input amplifier and tachogenerator. At low speeds of rotation, the zero drift is amplified and the voltage drop in the brush contacts of the tachogenerator becomes commensurate with the useful signal. Therefore, the allowable stability of the input signal and the feedback signal should not exceed 10% of the useful signal.

Meeting these requirements has led to more complicated feed drives, which has allowed optimal alignment of drives with the machine and NC device.

Due to the unsatisfactory dynamic properties of the adjustable electric drive, especially when disturbed by the load, surface roughness appears, so it is important to ensure a high speed of the drive when connecting and disconnecting the load, as well as when reversing the engine under load at the lowest speeds of rotation when disconnecting and connecting a load of 0.5 Mnom relative to a given level should not exceed 100% at n = 0.001 nom and a recovery time of 100 ms .

The following requirements are imposed on the electric supply drive:

- minimum dimensions of the motor at high torque;

- high maximum speed;

- significant overload capacity of the drive in short-term and re-short-term load modes;

- wide range of regulation;

- high stability of characteristics;

- high speed during acceleration and braking, connection and disconnection of load;

- high uniformity of movement at different loads at all speeds up to the lowest;

- convenience of constructive engine installation on the machine and embeddings of the operated converters in cases and niches of cases and a niche of machines.