Modernization of the main motion drive circuit of the milling machine to the SINUMERIC 820C USP

Introduction

Modern manufacturing requirements require a constantly developing industry in machine tool engineering. New GOST and accuracy requirements appear. Increasingly complex tasks inexorably force the modernization of existing machines, as well as the creation of new models. Today, machines should provide the possibility of high-performance production without manual subsequent refinement of parts that meet modern and constantly increasing requirements for the accuracy and increased quality of the manufactured parts.

In particular, great attention is paid to the drives of the main movement and feeds: to increase rigidity, increase the accuracy of rotation of shafts, spindle units.

A set of mechanisms with a motion source for actuating an actuator of a machine with predetermined speed and accuracy characteristics is called a drive.

Metal cutting machines are equipped with an individual drive; on many machines, the main movement, feed movement, auxiliary movements are carried out from separate sources - electric motors and hydraulic devices. The speed change can be stepless and stepped.

Drives of metal cutting machines are DC and AC electric motors, hydraulic motors and pneumatic motors. Electric motors were most widely used as machine drives. Where stepless shaft speed control is not required, asynchronous AC motors are used (as the cheapest and simplest). For stepless speed control, especially in feed mechanisms, direct current motors with thyristor control are increasingly used.

The advantages of using an electric motor as a drive include: high rotation speed, the possibility of automatic and remote control, as well as the fact that their operation is independent of ambient temperature.

Milling machines are designed for processing of external and internal flat and shaped surfaces, cutting of grooves, cutting of external and internal threads, gears, etc. The main movement is the rotation of the cutter, and the supply is the movement of the product together with the table on which it is fixed. In the process of processing, each blade of the cutter removes chips during a fraction of the revolution of the cutter, and the cross section of the cutter changes continuously from the smallest to the largest. Two groups of milling machines are distinguished: general purpose (for example, horizontal, vertical and longitudinal-milling) and specialized (for example, copy-cutting, tooth-cutting).

Depending on the number of degrees of freedom of movement of the table, cantilever-cutting (three movements - longitudinal, transverse and vertical), non-cantilever-cutting (two movements - longitudinal and transverse), longitudinal-milling (one movement - longitudinal) and carousel-cutting (one movement - circular working supply) machines are distinguished. All of these machines have the same master drive for rotating the spindle and different feed drives.

Copy and Mill is used to process spatially complex planes using template copying. As an example, the surfaces of dies, press molds, hydraulic turbines impellers, etc. On universal machines, the treatment of such surfaces is too complex or impossible at all. A variety of these most common machines are electro-copying machines with electric tracking control.

In the spindle head body there is a spindle motor, a speed box and a spindle for a cutter. Spindle head moves along crossbeam guides along its axis, and crossbeam, in its turn, along fixed post with vertical guides.

Thus, the machine has three mutually perpendicular movements: horizontal movement of the table, vertical movement of the spindle head together with the crosspiece, transverse movement of the spindle head along its axis. Volumetric processing is carried out in horizontal or vertical lines. Working tool: finger cylindrical and cone or end cutters.

The electric equipment of milling machines includes the main movement drive, feed drive, auxiliary movements drives, various electric control, control and protection devices, alarm systems and local lighting of the machine.

Machine drive is a set of devices that transmit motion from a motion source to working elements of the machine. Modern machines have individual drives, that is, each machine is driven by a separate electric motor, all the movements of the machine are carried out either from one or from several electric motors. There are main movement drive, feed drive, quick movement drive, etc.

The source of motion is an electric motor, most often asynchronous, short-circuited, installed in the immediate vicinity of the machine or on the machine itself. Motors that are installed directly on the machine and attached to it by their cover (flange) are called flange ones. Most often, such engines are used on drilling machines. On grinding and sharpening machines, built-in motors are widely used. These are engines in which the rotor is seated on the spindle of the machine.

By the nature of the control of the speed of the machine working elements, stepped and stepless drives are distinguished. Stepped drives allow to obtain within the specified limits a certain number of rotation speeds, double strokes or feed values. Stepless control systems allow you to set the most advantageous parameters of the cutting mode on the machine, in addition, this can be done without stopping the machine (on the go). In modern machines, stepless drives are used electric, hydraulic and mechanical (variators).

Stepped drives

Drives with stepwise adjustment are made in the form of gear gearboxes. The stepwise control mechanisms are simple in design and reliable in operation, so they are more widely used in modern machines than stepless control mechanisms. Since general purpose machines are used to process parts of various materials and different sizes (diameters), the value of spindle speeds in modern machines varies within quite large limits.

Limit speeds of rotation of machine spindle are found by maximum and lowest permissible cutting speeds and limit diameters of machining.

Stepless drives

In modern machines, stepless drives are electric, hydraulic, pneumatic and mechanical (variators).

Electric drives of stepless control. DC motors are often used as a source of motion. Since industrial enterprises are not centrally supplied with direct current, special sources are required to obtain it.

In modern machines, thyristor-controlled engines according to the thyristor converter-engine scheme are widely used. The drive allows to increase spindle rotation speeds up to 4000 rpm and more with stepless adjustment. The wide range of spindle speed control allows to ensure the required working and fast (idle) movements of the working elements without the use of intermediate mechanical gears. The thyristor is a semiconductor device. Thyristors are manufactured for current up to hundreds of amperes and voltage up to 1000 V or more. They have high efficiency, relatively small sizes, high speed. They can operate in a wide temperature range (from - 60 to + 60 ° C).

The main disadvantages of thyristor converters include a high sensitivity to overloads. Therefore, reduction is required for full use of the drive power when operating at low speeds of rotation of the spindle. The required control range in this case is obtained by combining an adjustable DC motor with a simplified speed box.

Hydraulic actuators. In modern metal cutting machines, drives are quite widespread. They are mainly used for rectilinear movements and to a lesser extent for rotational movements. Hydraulic drives are used both in mechanisms of the main movement (in long, strict, long), and in feeding mechanisms (grinding, software-controlled machines, copying, aggregate, etc.). Hydraulic drives are widely used in machine control mechanisms.

The main advantages of hydraulic drives: the ability to continuously adjust speeds, receive significant forces with relatively small drive dimensions; simplicity of overload protection; long service life, since the working medium itself simultaneously performs lubrication functions; low weight and volume per unit of power compared to an electric drive.

Disadvantages of hydraulic drives: the possibility of leakage of working fluid through seals and gaps, air penetration into working fluid, changing the properties of working fluid under the influence of pressure and temperature. One of the significant drawbacks of the hydraulic drive is its non-rigid characteristic.

Currently, frequency drives have become widespread.

The control of the electric motor involves the automation of all its operation, including starting, braking, reversing and changing the speed of rotation of the electric motor.

Automatic start-up enables smooth start-up resistances, the ability to adjust current within the required limits, which reduces the number of startup errors and improves the overall system performance. The same goes for reverse and braking.

The frequency control eliminates one of the significant disadvantages of short-circuited motors - the constant rotor speed of the motor, independent of the load. The frequency control makes it possible to control the speed of the motor according to the nature of the load. This, in turn, avoids complex transient processes in electrical networks, ensuring that the equipment operates in the most economical mode.

Frequency control of the electric motor is effectively used in industrial enterprises, in the field of energy, utilities and other fields. This is due to the fact that frequency control allows you to automate production processes, economically spend electricity and other resources involved in production, improve the quality of products, as well as increase the reliability of the entire system.

Frequency control also improves the reliability and durability of the process system. This is ensured by reducing starting currents, eliminating overloads of system elements.

The modernization of the drive scheme of the main movement of the milling machine to the CNG SINUMERIC 820C will be considered using the example of the control scheme of the CNG 40 CNC E universal tool milling machine using the ALTIVAR frequency converter.

Relevance of the work: due to the constant increase in requirements for the quality of production and processing of parts, the CNG 40 CNC E tool universal milling machine is widely used in the engineering industry. This machine is equipped with modern components of the SINUMERIC 820C ECC and the ALTIVAR frequency converter. Therefore, it is relevant to consider the connection of the main motion drive to the ECC to control the cutting process.

The purpose of the graduation qualification work is to modernize the drive scheme of the main movement of the milling machine to the SINUMERIC 820C ECC for the control of the CNG 40 CNC E universal tool milling machine.

In order to achieve this goal, a number of objectives must be met:

Analyze the technical literature on the systematization of various schemes;

coordinate systems of machine, part, tool;

Analyze the technical literature of the study and the principle of operation of frequency converters;

Develop technical description of power circuit components of CNG 40 CNC E Universal Tool Milling Machine

analyze the operation of CNG 40 CNC E Universal Tool Milling Machine power scheme

perform analysis of possible failures of power circuit and methods of their elimination.

The subject of the study is the universal tool milling machine CNG 40 CNC E.

The subject of the study is the power scheme of the CNG 40 CNC E universal tool milling machine.

Conclusion

In the final qualification work on the topic "Modernization of the drive diagram of the main movement of the milling machine to ECU SINUMERIC 820C," the connection of the SINUMERIC 820C system to the CNG 40 CNC E. universal tool milling machine was analyzed. Structure and principle of operation of frequency converters are considered in detail. The operation and installation manual of CNG SINUMERIC 820C was studied, functional decomposition of the schematic diagrams of the CNG 40 CNC E universal tool milling machine was made, the connection diagrams of the supply and drive drives of the main movement of SINUMERIC 820C were given.

During the work, the material of the technical literature on the issues of coordinate systems of machines with numerical program control, types and types of schemes was studied.

The following general and professional competencies have been applied by me in the course of the thesis project.

Professional competencies

PC 1.1. Perform performance analysis of measuring instruments and automation equipment.

PC 3.2. Monitor and analyze operation of system parameters during operation.

PC 4.1. Perform analysis of automatic control systems taking into account the specifics of technological processes.

PC 4.3. To make schemes of specialized knots, blocks, devices and the systems of automatic control.

PC 5.2. Analyze reliability characteristics of automation systems.

General competencies (QA):

OK 1. To understand the essence and social significance of your future profession, to show steady interest in it.

OK 2. Organize your own activities, choose standard methods and methods for performing professional tasks, evaluate their effectiveness and quality.

OK 3. Make decisions in standard and non-standard situations and be responsible for them.

OK 4. Search and use information necessary for the effective performance of professional tasks, professional and personal development.

OK 5. Use information and communication technologies in professional activities.

OK 6. Work in a team and team, communicate effectively with colleagues, management, consumers.

OK 7. Take responsibility for the work of team members (subordinates), the result of completing tasks.

OK 8. Independently determine the tasks of professional and personal development, engage in self-education, consciously plan for advanced training.

OK 9. To be guided in conditions of frequent change of technologies in professional activity.

Thus, I consider the goals and tasks set and the final qualification work fulfilled.