Machine tool is an important tool for human production and labor and an important symbol of the development level of social productive forces.

Ordinary machine tools have a history of nearly 200 years. With the development and comprehensive application of electronic technology, computer technology and its automation, precision machinery and measurement technology, a new machine tool with electromechanical integration-CNC machine tool has emerged. Once used, CNC machine tools show their unique advantages and strong vitality, which makes many previously unsolvable problems find scientific solutions.

CNC lathe is the abbreviation of CNC lathe. It combines the characteristics of general lathe with good versatility, precision lathe with high machining accuracy and special lathe with high machining efficiency. It is a CNC machine tool with the largest usage and the widest coverage in China. It is also an electromechanical integrated processing equipment that controls the machine tool to automatically process according to the given motion trajectory through digital information. After half a century's development, CNC machine tools have become one of the important symbols of modern manufacturing industry in China.

Practice, practice, report and revise the text.

Since entering the university, the employment problem always seems to surround us and become an endless topic. In today's society, the posters of job fairs always say "experience is preferred", but how much social experience will our students have on campus? In order to expand one's knowledge, expand contact with society, increase one's experience in social competition, exercise and improve one's ability, make oneself really enter the society after graduation, adapt to the changes of domestic and international economic situation, and handle various problems in life and work well. This holiday, I started an off-campus internship. .

Apply the theoretical knowledge you have learned to the objective reality, and let your theoretical knowledge be applied. Learning without practice equals zero, and theory should be combined with practice. On the other hand, practice can lay a foundation for finding a job in the future. Through this period of internship, I learned something that I couldn't learn at school. Because the environment is different, the people and things you contact are different, and the things you learn from it are naturally different. Learn to learn from practice and practice from learning. Moreover, with the rapid development of China's economy and China's accession to the WTO, the domestic and international economies are changing with each passing day, and new things are constantly emerging every day. While there are more and more opportunities, there are also more challenges. The more China's economy is integrated with the outside world, the higher the demand for talents will be. We should not only learn what we have learned in school, but also learn other knowledge from life and practice.

1.f function

F function instruction is used to control cutting feed. In the program, there are two ways to use it.

(1) Feed per revolution

Programming format G95 F~

The number after f represents the feed speed of the spindle per revolution, and the unit is mm/r.

For example, G95 F0.2 indicates that the feed speed is 0.2 mm/r..

(2) Feed per minute

Programming format G94 F~

The number after f indicates the feed per minute, and the unit is mm/min.

For example, G94 F 100 means that the feed speed is 100mm/min.

2. Axis function

S function instruction is used to control the spindle speed.

Programming format S~

The number after s indicates the spindle speed in rpm. On the machine tool with constant linear speed function, the S function instruction also has the following functions.

(1) Maximum speed limit

Set the machining coordinate system

Programming format g50s ~

The number after s indicates the maximum speed: r/min.

For example, G50 S3000 means that the maximum speed is limited to 3000 rpm.

(2) Constant linear speed control

Programming format g96s ~

The number after s represents a constant linear velocity: m/min.

For example, G96 S 150 means that the linear speed of the cutting point is controlled at 150 m/min.

(3) Cancel the constant linear speed

Programming format g97s ~

The number after s indicates the spindle speed after canceling the constant linear speed control. If s is not specified, the final value of G96 will be retained.

For example, G97 S3000 indicates that the spindle speed is 3000 r/min after the constant linear speed control is cancelled.

3. Test function

The t function command is used to select a tool for machining.

Programming format t ~

T is usually followed by two digits to indicate the selected tool number. But there are also four digits behind T, the first two digits are the tool number, and the last two digits are the tool length compensation number and the tool tip arc radius compensation number.

Example: T0303 indicates the selection of No.3 cutter, the compensation value of No.3 cutter length and the compensation value of tool tip arc radius.

T0300 means canceling tool compensation.

4.m function

M00: the program is suspended, and the program can be kept running with the loop start command;

M0 1: The plan is suspended, which is similar to M00, but M0 1 can be selected by using the "optional stop button" of the machine tool.

M03: Spindle rotates clockwise;

M04: Spindle rotates counterclockwise;

M05: Spindle rotation stops;

M08: Coolant is turned on;

M09: Coolant is turned off;

M30: The program stops, and the program is reset to the starting position.

5. Set the machining coordinate system G50

Programming format g50x ~ z ~

Where the values of x and z are the positions of the starting point relative to the machining origin. The usage of G50 is similar to that of G92.

When programming a CNC lathe, all X coordinate values use diameter values, as shown in the figure.

For example, the program part of setting machining coordinates according to drawings is as follows:

G50 X 128.7 Z375. 1

6. Quick positioning instruction G00

G00 command commands the machine tool to move to the next target position at the fastest speed, with acceleration and deceleration during the movement. This command has no requirement for motion trajectory. Its instruction format:

g00 X(U)_ _ _ _ _ _ _ Z(W)_ _ _ _ _ _ _；

When programming with absolute value, the values after x and z are the coordinates of the target position in the workpiece coordinate system. When programming with relative values, the values after u and w are the distance and direction between the current point and the target point. As shown in the figure, the positioning instructions are as follows:

G50 X200.0 Z263.0 Set the workpiece coordinate system.

g00 x 40.0 z 2 12.0； Absolute value instruction programming A→C

Or g00u-160.0w-51.0; Relative value instruction programming A→C

Because the feed speed of X axis and Z axis is different, when the machine tool executes the fast motion instruction, the combined motion trajectory of the two axes is not necessarily a straight line. Therefore, when using G00 instruction, we must pay attention to avoid the collision between the tool and the workpiece and fixture. If we ignore this point, it is easy to collide, and the collision in a fast moving state is even more dangerous.

7. Linear interpolation instruction G0 1

G0 1 command commands the machine tool to move from the current position to the target position given by the command at a certain feed speed.

Instruction format: g 01x (u) _ _ z (w) _ _ f;

Where f is the cutting feed rate or feed speed, and the unit is mm/r or mm/min, depending on the setting of the program section before the instruction. When using G0 1 instruction, you can use absolute coordinate programming or relative coordinate programming. When absolute coordinate programming is adopted, after receiving the instruction G0 1, the CNC system moves the tool to the point of X and Z coordinate values. When relative positioning programming is adopted, the tool moves to a point away from the current points U and W.. As shown in the figure, the linear motion command is as follows:

G0 1 X40.0 Z20。 F0.2 absolute value instruction programming

g 0 1 u 20.0 W-25.9 f 0.2； Relative value instruction programming

8. Circular interpolation instructions G02 and G03

The circular interpolation command commands the cutter to perform circular interpolation motion at a given F feed speed in the specified plane, which is used to process the circular contour. Circular interpolation command is divided into clockwise circular interpolation command G02 and counterclockwise circular interpolation command G03. The instruction format is as follows:

Instruction format of clockwise circular interpolation: G02x (u) _ _ z (w) _ _ i _ _ _ _ k _ _ f _ _;

g02 X(U)_ _ Z(W)_ _ R _ _ _ F _ _ _ _；

Instruction format of counterclockwise circular interpolation: G03x (u) _ _ z (w) _ _ i _ _ _ _ k _ _ _ f _ _; ;

g03 X(U)_ _ Z(W)_ _ R _ _ _ F _ _ _ _；

Using circular interpolation instruction, you can program in absolute coordinates or relative coordinates. When programming absolute coordinates, x and z are the coordinates of the end of the arc; In incremental programming, u and w are the distance between the end point and the start point. The position of the center of the circle can be specified by R, and I, K, and R can also be used as arc radius values; I and k are the coordinate increments of the center of the circle on the X axis and Z axis relative to the starting point of the arc; F is the feed rate or feed speed along the tangent direction of the arc.

When the radius r is used to specify the position of the center of the circle, there are two arc possibilities from the starting point to the end point of the arc under the same radius r, which are greater than 180 and less than 180. For the sake of distinction, it is stipulated that when the central angle α ≤180, it is represented by "+R"; α& gt； When 180, use "-R". Note: R programming is only suitable for arc interpolation of non-integer circles, not for machining integer circles. For example, the arc shown in Figure 3- 13 is clockwise from the starting point to the end point, and its feed instruction can be written as:

g02 x 50.0 z 30.0 I 25.0 f 0.3； Absolute coordinates, diameter programming, cutting feed rate of 0.3 mm/r.

g02 u 20.0 W-20.0 I 25.0 f 0.3； Relative coordinates, diameter programming, cutting feed rate of 0.3 mm/r.

G02 X 50。 0z 30.0 r 25.0 f 0.3； Absolute coordinates, diameter programming, cutting feed rate of 0.3 mm/r.

g02 u 20.0 W-20.0 r 25.0 f 0.3； Relative coordinates, diameter programming, cutting feed rate of 0.3 mm/r.

9. Pause instruction G04

G04 instruction is used to pause feeding, and its instruction format is:

G04 P____ _ _ or G04x (u) _ _ _

The length of the pause time can be specified by the address X(U) or p, where the number after p is an integer and the unit is ms; The number after X(U) is a number with decimal point, and the unit is s. In some machine tools, the number after X(U) indicates the number of empty turns of the tool or workpiece.

This command can make the tool not feed for a short time, and can be used for turning and boring, and also for corner trajectory control. For example, when turning an annular groove, if the tool is withdrawn immediately after the feed is finished and the annular groove is in the shape of a helicoid, you can use the pause command G04 to idle the workpiece for a few seconds, so that the shape of the annular groove can be rounded. For example, it will idle for 2.5s, and the program segment is G04 X2.5 or G04 U2.5 or G04P2500.

G04 is a modeless instruction, which is only valid in this program section.

10. English and metric input instructions G20 and G20 1

G20 stands for English input and G20 1 stands for metric input. G20 and G20 1 are two alternative codes. Machine tools are generally set to G2 1 state before leaving the factory, and all the parameters of the machine tools are set to metric units, so CNC lathes are generally suitable for machining workpieces with metric dimensions. If a program starts to use G20 instruction, it means that some data related to the program is in English (in inches). If the program is instructed by G2 1, it means that some data related to the program is in metric system (in mm). In a program, instructions G20 or G20 1 cannot be used at the same time, and must be specified before determining the coordinate system. G20 or G20 2 1 instructions are consistent before and after the power outage, that is, the instructions G20 or G20 2 1 used before the power outage will still be valid after the next power outage unless reset.

1 1. Feed speed size control instructions G98 and G99.

There are two ways to set cutting feed mode in NC turning, namely feed speed (feed mode per turn) and feed speed (feed mode per minute).

(1) feed speed, in mm/r, and its instruction is:

G99 feed speed conversion instruction

g 0 1X _ _ _ _ _ Z _ _ _ _ _ F _ _ _ _； The unit of f is mm/r.

(2) Feed speed, in mm/min, and its instruction is:

G98 feed speed conversion instruction

g 0 1X _ _ _ _ _ Z _ _ _ _ _ F _ _ _ _； The unit of f is millimeter/minute.

Both G98 and G99 are modal instructions, which remain valid once they are specified until another modal is specified. The default feed mode of turning CNC system is feed speed, that is, the feed mode per minute is adopted only when milling with electric tools.

12. Reference point return instructions G27, G28 and G30

The reference point is a fixed point on the NC machine tool, and the tool rest can be moved to this point by using the reference point return instruction. Up to four reference points can be set, and the position of each reference point is preset by using parameters. After turning on the power supply, you must first return to the first reference point, otherwise you can't do other operations. There are two ways to return the reference point:

(1) Manual reference point return.

(2) Automatic reference point return. This function is an automatic reference point return function, which is used when it is necessary to return to the reference point for program tool change after the power is turned on and the manual reference point is returned.

Automatic reference point return requires the following instructions:

(1) Return to the reference point to check G27.

G27 is used to check whether the X axis and Z axis return to the reference point correctly. The instruction format is:

g27 X(U)_ _ _ _ _ Z(W)_ _ _ _ _

X(U) and Z(W) are the coordinates of the reference point. The premise of executing G27 instruction is that the machine tool must return to the reference point manually after being electrified.

When this command is executed, each axis is quickly positioned according to the coordinate values given in the command, and the system checks the travel switch signal of the reference point internally. If the switch signal is detected to be correct after positioning, the reference point indicator light is on, indicating that the skateboard has returned to the reference point position correctly; If the detected signal is incorrect, the system will give an alarm, indicating that the coordinate values of the reference points indicated in the program are incorrect or the positioning error of the machine tool is too large.

(2) Reference point return instructions G28 and G30

g28 X(U)_ _ _ _ _ _ _ Z(W)_ _ _ _ _ _ _； The first reference point returns, where X(U) and Z(W) are the intermediate points when the reference point returns, x and z are absolute coordinates, and u and w are relative coordinates. The reference point return process is shown in Figure 3- 14.

g30 P2 X(U)_ _ Z(W)_ _ _ _ _ _ _； The second reference point returns, and P2 can be omitted.

g30 P3 X(U)_ _ Z(W)_ _ _ _ _ _ _； Return of the third reference point

g30 P4 X(U)_ _ Z(W)_ _ _ _ _ _ _； Fourth reference point return

The meanings of X(U) and Z (W) in the second, third and fourth reference point returns are the same as those in G28.

When the tool returns to the reference point, the tool returns to the reference point from the current position through the intermediate point (190,50), and its instruction is: g30x190z50; G30 U 100 W30 .

CNC machine tools are generally composed of input device, CNC system, servo system, measuring link and machine tool body (the mechanical part of machine tool body). As shown in the composition diagram of CNC machine tools.

Schematic diagram of NC machine tool composition

1) input and output devices

operation panel

It is a tool for operators to exchange information with numerical control equipment: button station/status light/button array/display. The figure below shows the operation panel of Siemens CNC system.

Control substance

The intermediate medium for establishing some connection between human and CNC machine tools is the control medium, also known as the information carrier. Commonly used quality control includes punched tape, punched card, magnetic disk and magnetic tape.

Man-machine interaction equipment

In the process of machining operation of CNC machine tools, operators usually need to intervene in the state of CNC system, edit, modify and debug the input machining program, and display the running state of CNC machine tools, which means that CNC machine tools should have the function of man-machine contact. Devices with human-computer contact function are collectively called human-computer interaction devices. Commonly used human-computer interaction devices include keyboards, monitors, photoelectric readers, etc.

Communication In addition to using input and output devices, modern CNC systems usually have the ability to exchange information through communication. They are the basic technologies to realize the integration of CAD/CAM, FMS and CIMS. The method adopted is as follows:

Serial communication (RS-232 serial port)

Special interfaces and specifications of automatic control (DNC mode, MAP protocol, etc.). )

Network technology (Internet, LAN, etc.). ).

DNC is an English word for direct digital control or distributed digital control.

The abbreviation of the word means direct digital control or distributed digital control.

2) Computer numerical control (CNC) device

Numerical control device is the center of numerical control machine tool. Numerical control device (numerical control unit)

Composition: computer system, position control board, PLC interface board, communication interface board, special function module and corresponding control software.

Function: Perform corresponding processing (such as motion trajectory processing, machine tool input and output processing, etc.). ) according to the input parts processing program, and then output control commands to the corresponding executive components (servo unit, driving device and PLC, etc. ). All these tasks are coordinated and reasonably organized by the hardware and software in the CNC device, so that the whole system can work in an orderly way. Numerical control device is the core of numerical control system.

3) Feed servo drive system

The feed servo drive system consists of servo control circuit, power amplifier circuit and servo motor. The function of the servo drive is to convert the position control movement command sent by the numerical control device into the movement of the working parts of the machine tool, so that the workbench can move or accurately position according to the specified trajectory, and the workpiece that meets the requirements of the pattern can be processed, that is, the weak command signal sent by the numerical control device is amplified into a high-power signal that can drive the servo motor.

Commonly used servo motors include stepping motor, DC servo motor and AC servo motor. According to the received instructions, there are pulse servo drive and analog servo drive, and analog servo drive can be divided into DC servo drive and AC servo drive according to the power supply type of the driving motor. Stepper motor adopts pulse drive mode, and AC and DC servo motors adopt analog drive mode.

4) Electrical control of machine tools

The electrical control of the machine tool includes two aspects, as shown by the arrow in the figure. PLC (Programmable Logic Controller) is used to complete the I/O control of sequential actions related to logical operation, and the I/O circuit and device of machine tool are the executive parts for realizing I/O control, which are logic circuits composed of relays, solenoid valves, travel switches and contactors.

5) Measuring device

Measuring device in numerical control machine tool

Feedback system in CNC machine tools. The function of the feedback system is to detect the actual position and speed parameters of the machine tool movement through the measuring device, convert them into electrical signals, and feed them back to the CNC device, so that CNC can judge whether the actual position and speed of the machine tool are consistent with the instructions at any time, and issue corresponding instructions to correct the errors. In other control fields, measuring equipment also has their applications.

Control motor and measuring device in robot hand

The measuring device is installed on the workbench of CNC machine tool or on the lead screw. According to the presence or absence of detection devices, CNC systems can be divided into open-loop and closed-loop systems, and according to the installation position of measuring devices, they can be divided into closed-loop and semi-closed-loop CNC systems. Open-loop control system has no measuring device, and its control accuracy depends on the accuracy of stepping motor and lead screw, while the accuracy of closed-loop numerical control system depends on the accuracy of measuring device. Therefore, the detection device is an important part of high-performance CNC machine tools.

6) Machine tool body

The mechanical parts of CNC machine tools include: main moving parts, feed motion executing parts, such as workbench, carriage and its transmission parts, lathe bed, columns and other supporting parts; In addition, there are auxiliary devices such as cooling, lubrication, indexing and clamping. For CNC machine tools with machining centers, there is a tool library for storing tools and a manipulator for exchanging tools and other parts. Numerical control machine tool is a kind of automatic processing machine tool with high precision and high productivity. Compared with ordinary machine tools, it should have better vibration resistance and stiffness, and require a small friction coefficient relative to the moving surface and a small gap between the feed transmission parts. Therefore, its design requirements are stricter than those of ordinary machine tools, and its machining and manufacturing requirements are precise. The design measures of strengthening stiffness, reducing thermal deformation and improving accuracy are adopted. The auxiliary control device includes tool magazine index and tool change.

The above is the general structure of CNC lathe. During my internship, I learned about CJK0620 CNC machine tool produced by our company, which consists of the following units: frequency converter (model lnovance), two all-digital AC servo units (model SD20B) and control transformer (model BK 1500, capacity 1.5KV/A, frequency 50-. The machine level voltage is 380V, and the secondary voltage is 220V), and the control transformer (model BK 150, capacity 150V/A, frequency 50-60HZ, insulation class b, machine level voltage 380V, secondary voltage1-kloc). 11-13: 220v), a fan, two lead screws, a workbench, two AC servo motors, a tool rest, a lubricating device, a carriage, etc.

last or end syllable

Time flies, and two weeks have passed quickly. The experience I got from this internship is:

(1) Through this internship, we learned about the production mode and technological process of modern CNC machine tools. Familiar with the forming methods and main processing methods of some materials, the working principle and typical structure of the main equipment used, the use of fixtures and measuring tools and the safe operation technology. Understand the knowledge of CNC machine tools and the application of new technologies, new processes and new equipment in machine tool production.

(2) Engaged in the production, assembly and debugging of CNC machine tools, with preliminary independent operation skills.

(3) In the process of understanding, being familiar with and mastering certain basic knowledge and operation skills of CNC machine tools, I have cultivated, improved and strengthened my hands-on ability, innovative consciousness and innovative ability.

This internship made us understand that we should be careful and not careless. At the same time, it also cultivated our strong and unyielding nature, and never gave up perseverance until the last second!

⑤ We have cultivated and exercised our views on labor, quality and economy, strengthened our awareness of observing labor discipline, safety technical regulations and caring for state property, and improved our overall comprehensive quality.

Yes, the knowledge learned in textbooks is the most basic knowledge. No matter how the actual situation changes, mastering the most basic knowledge can keep changing. Now many students feel that the knowledge learned in class is useless and depressed, but I think how to deal with the ever-changing society without book knowledge? After this internship, although the time is very short, I learned something that I didn't understand in school for a semester. For example, how to get along with colleagues, I believe that interpersonal relationship is a big problem for many college students who have just stepped out of society, so I deliberately observed how seniors get along with colleagues and superiors during my internship, and I also tried my best to ask for advice humbly. Improving interpersonal relationships is not limited to our own department, but also good relations with colleagues in other departments, such as the marketing department, so that the work efficiency will be high, and what people call "making money harmoniously" is not unreasonable in our daily work. Moreover, chatting with seniors at work can not only relax your nerves, but also learn a lot of things outside of work. Although we may not encounter many situations, it is also one of the purposes of this internship to get to know them.

Soon we will step into the society and face employment. The employment unit will not tell us the work to be done in detail like the teacher, but we need to observe and learn by ourselves. Without this ability, it is difficult to be competent for future challenges. With the rapid development of science and the wide application of new technologies, there will be many fields that we have never touched. Only by daring to try can we make a breakthrough and make innovations. Just like the processing of parts that I came into contact with in my internship, although it is very dangerous, I have to operate it myself and make a finished product, which has exercised my courage to try.