"CNC" is the English Computerized Numerical Control (computer digital control) abbreviation. CNC machine tools are in accordance with the pre-programmed processing program, automatically processed parts. We put the parts of the machining process route, process parameters, tool trajectory, displacement, cutting parameters (spindle speed, feed, back eating amount, etc.) as well as auxiliary functions (tool change, spindle positive, negative, cutting fluid on, off, etc.), in accordance with the provisions of the CNC machine tool instruction code and program format is written into the processing program list, and then the contents of this program list is recorded in the control media (such as perforated paper tape, Magnetic tape, magnetic disk, magnetic bubble memory), and then input to the CNC machine tool CNC device, so as to command the machine tool processing parts.
This from the analysis of the parts map to make the control medium of the whole process called CNC program preparation. CNC machine tools and ordinary machine tools to process parts of the difference is that CNC machine tools are in accordance with the program to automatically process parts, and ordinary machine tools to be operated by people, we only need to change the program to control the action of the machine tool to achieve the purpose of processing different parts. Therefore, CNC machine tools are particularly suitable for processing small quantities and complex shapes requiring high precision parts.
Because CNC machine tools have to process parts according to the program, the programmer prepares the program and inputs it into the CNC device to command the machine tool to work. The input of the program is through the control medium.
The CNC program can be divided into three parts: the beginning of the program, the content of the program and the end of the program.
The first part of the program start part
The main definition of the program number, call out the parts machining coordinate system, machining tools, start the spindle, open the coolant and other aspects of the content.
CNC program
Spindle maximum speed limit definition G50 S2000, set the spindle's maximum speed of 2000RPM, for CNC lathe, this is a very important instruction.
Coordinate system definition if not specified, the CNC system defaults to G54 coordinate system.
Return to reference point instruction G28 U0, in order to avoid collision or interference between the tool holder and the workpiece or fixture during the tool change process, an effective way is for the machine tool to first return to the X-axis direction of the machine's reference point and to leave the spindle a safe distance.
Tool Definition G0 T0808 M8, auto-tuning No. 8 left offset tool No. 8 tool complement, turn on the coolant.
Spindle speed definition G96 S150 M4, constant linear speed S function definition, S function makes the spindle speed instruction function of CNC lathe, there are two ways of expression, one is to r/min or rpm as the unit of measurement. The other is in m/min as the unit of measurement. The S code of the CNC lathe must be used in conjunction with G96 or G97 to set the spindle speed or cutting speed.
G97: RPM command, defines and sets the revolutions per minute.
G96: Constant Line Speed instruction, which makes the cutting speed the same at any position on the workpiece.
Part II Program Content Section
The program content is the main part of the entire program and consists of several program segments. Each program segment consists of a number of words, and each word consists of an address code and a number of numbers. Commonly, the program segments are composed of the G and M instructions and the coordinate points of each axis, with the addition of the functional definition of the feeds.
F function is the function of feed speed, CNC lathe feed speed has two ways of expression, one is the amount of feed per revolution, that is, expressed in mm / r units, mainly used for turning feed. Another and CNC milling machine the same use of feed per minute, that is, expressed in mm/min units. Mainly used in milling milling machining center feed.
The third part of the end of the program
At the end of the program, the need for the tool holder to return to the reference point or the machine reference point for the next tool change safety position, while the spindle stop, turn off the coolant, the program selects the stop or end of the program and other actions.
The return reference point instruction G28U0 is to return to the X-axis direction machine reference point, G0 Z300.0 is to return to the Z-axis direction reference point.
Stop instruction M01 is a selective stop instruction, which is valid only when the selective stop switch of the equipment is open; M30 is an end-of-program instruction, which stops all the coolant, feed and spindle when executed. The CNC program and CNC equipment reset and return to the original state before machining to prepare for the next program run and CNC machining restart.
CNC Machine Programming
I. CNC machine tool programming methods
There are three methods of CNC machine tool programming: namely, manual programming, automatic programming and
Machining Center CAD/CAM .
1. Manual Programming
To be completed by manual parts drawing analysis, process processing, numerical calculations, writing program lists until the program input and inspection. Applicable to point processing or geometric shape is not too complex parts, however, very time-consuming, and the preparation of complex parts, prone to error.
2. Automatic programming
Using a computer or programmable machine, the process of completing the preparation of the part program, for complex parts is very convenient.
3. CAD/CAM
Use CAD/CAM software to realize the modeling and image automatic programming. The most typical software is Master CAM, which can complete the milling two-coordinate, three-coordinate, four-coordinate and five-coordinate, turning, wire EDM programming, such software, although a single function, but easy to learn, the price is low.
II. CNC machine programming content and steps
1. The main content of CNC machine programming
Analysis of parts drawings, to determine the process of machining technology, mathematical processing, preparation of the program list, the production of control media, program checking, input procedures, and the workpiece test cutting.
2. CNC machine steps
1) Analyze the parts drawing and process
Analyze the geometric shape and size of the parts according to the drawing and technical requirements, clarify the content and requirements of machining, and decide on machining programs, determine the machining sequence, design fixtures, select cutting tools, determine a reasonable tool route and select a reasonable amount of cutting and so on.
At the same time, it should also play the function of the CNC system and the ability of the CNC machine itself, the correct choice of the tool point, cut into the way to minimize such as tool change, transposition and other auxiliary time.
2) Mathematical processing
Before programming, according to the geometric characteristics of the parts, first establish a workpiece coordinate system,
NC system functions according to the requirements of the parts drawings, the development of machining routes, in the establishment of the workpiece coordinate system, the first calculation of the tool's trajectory. For parts with relatively simple shapes (such as parts composed of straight lines and arcs), only the starting point of the geometric elements, the end point, the center of the arc, the intersection of the two geometric elements or the tangent point of the coordinate values need to be calculated.
3) Preparation of parts program list
After the machining route and process parameters are determined, the parts program list is prepared according to the specified code and program segment format specified by the CNC system.
4) Program input
5) Program verification and the first piece of test cutting
three. The structure of the CNC machining program
1. Composition of the program: consists of a number of program segments.
O0001; O (FANUC-O,AB8400-P,SINUMERIK8M-%) function to specify the program number, each program number corresponds to a machining part.
N010 G92 X0 Y0; the semicolon indicates the end of the program segment
N020 G90 G00 X50 Y60;
... ; subroutines can be called.
N150 M05;
N160 M02;
2. Program segment format:
1) Word address format: such as N020 G90 G00 X50 Y60;
The most commonly used format, modern CNC machine tools use it. Address N for the program segment number, address G and the number 90 constitute the word address for the preparation function, ....
2) Variable program segment format: such as B2000 B3000 B B6000;
Using the separator B to open each word, if there is no data, the separator can not be omitted. Commonly used in CNC wire-cutting machine tools, in addition, there are 3B programming and other formats.
3) Fixed sequence program segment format: such as 00701 + 0;
Rarely seen. The data therein are arranged strictly in accordance with the order and length, there shall be no
Siemens system control of the robot error, the above program segment means: N007 G01 X+02500 Y-13400 F15 S30 M02;
Mathematical treatment of parts drawings
Mathematical treatment of parts drawings is mainly the calculation of the dimensions of the parts machining trajectory, that is, the calculation of the The coordinates of the base point and node of the machining contour of the part, or the base point and node of the tool center contour, in order to prepare the machining program.
I. Calculation of base point coordinates
General CNC machine tools only straight line and arc interpolation function. For the plane contour composed of straight lines and circular arcs, programming the main task of numerical calculation is to find the coordinates of the base point.
1. The meaning of the base point
The intersection or tangent point of different geometric lines that constitute the contour of the part is called the base point. The base point can be used directly as the starting point or end point of its trajectory.
2. The content of the direct calculation
Based on the requirements of filling out the machining program, the content of the direct calculation of the base point are: the coordinates of the start and end of each trajectory in the selected coordinate system, the center of the arc trajectory coordinates.
Base point of direct calculation method is relatively simple, generally according to the known conditions given by the part drawing can be completed manually. That is, based on the dimensions given on the parts drawing using algebra, trigonometry, geometry or analytical geometry knowledge, directly calculate the value. In the calculation, pay attention to the number of decimal places to stay enough to ensure sufficient accuracy.
II. Calculation of nodal coordinates
For some plane contour is a non-circular equation curve Y = F (X) composition, such as involute, Archimedean spiral, etc., can only be processed with the straight line and arc to approximate them. The task of numerical computation at this point is to calculate the coordinates of the nodes.
1. Definition of nodes
When the use of non-circular curve interpolation function does not have the CNC machine tool processing non-circular curve contour parts, in the preparation of the machining program, commonly used in a number of straight line segments or arcs to approximate the replacement of non-circular curves, which is known as the fitting process. The intersection or tangent point of the fitted line segment is called the node.
2. Calculation of node coordinates
The node coordinates of the calculation of the difficulty and workload are larger, it is often done through the computer, if necessary, can also be calculated manually, commonly used linear approximation (such as the spacing method, such as the length of the step method, and so the error method) and the arc approximation method.
Some people use AutoCAD drawing, and then capture the coordinate points, in the range of accuracy allowed,
Fanuc CNC system is also a simple and effective method.
Cultivation objectives:
This program trains students to engage in CNC machining, mechanical product design and manufacturing, production technology management of higher engineering technology application talents. Students are required to be able to engage in product manufacturing, development work in the production site, or in the technical department engaged in process, management work. The main training students CNC programming, processing and CNC lathe, CNC milling machine, CNC machining centers and other CNC equipment operation and maintenance, maintenance of theoretical knowledge and professional knowledge. And can get the national labor and social security ministry issued by the CNC technician technical grade certificate, turning and clamping grade certificate.
The main courses: mechanical drawing and computer graphics, engineering mechanics, mechanical design, microcontroller principles and interface technology, basic mechanical manufacturing technology, basic electrical and electronic, electrical control technology, CNC machine tool control technology and systems, CNC machine tool principles and applications, CNC machine tool programming and operation, CAD/CAM technology, machine tool fixtures, CNC machine tool maintenance technology. AUTOCAD plane drawing, MASTERCAM three-dimensional design, PRO/E entity modeling. As well as metalworking practical training, turning and clamping practical training, CNC car practical training.
Employment:
The graduates of this program are mainly oriented to the Pearl River Delta foreign-funded large and medium-sized enterprises and institutions and state-owned enterprises and institutions of the operation, sales, process, equipment maintenance and other departments, mainly to train CNC machine operators, CNC programming process personnel, NC NC programming, CNC equipment maintenance personnel, CNC equipment marketing personnel. In addition can also be engaged in CAD / CAM software applications, CNC systems or equipment sales and technical service work, CNC equipment installation and commissioning and maintenance, as well as workshop production organization and management work.NC NC programming,
Programming skills
The development of science and technology, resulting in the accelerated replacement of products and the diversification of people's needs, the production of products tends to be kind of Diversification, batch size small and medium-sized. In order to adapt to this change, the role of numerical control (NC) equipment in the enterprise is getting bigger and bigger. Our school as a national key vocational school, in order to comply with the trend of the times, focusing on the construction of CNC specialization, the purchase of BIEJING-FANUC Power Mate O CNC lathe. It is compared with the ordinary lathe, a significant advantage is: the adaptability of parts changes, replacement parts only need to change the corresponding program, a simple adjustment of the tool can make qualified parts, to save costs to win the first opportunity. However, to give full play to the role of CNC machine tools, not only to have good hardware, (such as: high-quality cutting tools, machine accuracy, etc.), and more importantly, the software: programming, that is, according to the characteristics of different parts, the preparation of reasonable and efficient machining program. Through years of programming practice and teaching, I figured out some programming skills.
Although CNC lathe processing flexibility is superior to ordinary lathes, but only on the productivity of a particular part, and ordinary lathes there is still a certain gap. Therefore, to improve the efficiency of the CNC lathe has become the key, and the rational use of programming skills, the preparation of high-efficiency machining program to improve the efficiency of the machine tool often has an unexpected effect.
Flexible setting of the reference point
BIEJING-FANUC Power Mate O CNC lathe **** there are two axes, namely, the spindle Z and the tool axis X. The center of the bar for the origin of the coordinate system, the knife is close to the bar, the value of the coordinates decreases, known as the tool into the knife; on the contrary, the value of the coordinates increase, known as the knife back. When back to the beginning of the tool position, the tool stops, this position is called the reference point. The reference point is a very important concept in programming. After each automatic cycle, the tool must return to this position to prepare for the next cycle. Therefore, before executing the program, the actual position of the tool and spindle must be adjusted to be consistent with the coordinate values. However, the actual position of the reference point is not fixed, the programmer can adjust the position of the reference point according to the diameter of the part, the type and number of tools used, and shorten the empty travel of the tool. This improves efficiency.
Zero to whole method
In the low-voltage electrical appliances, there are a large number of short pin parts, its length-to-diameter ratio of about 2 ~ 3, the diameter of more than 3mm below. Due to the small geometric size of the parts, ordinary instrument lathes are difficult to clamping, can not guarantee the quality. If programmed in accordance with conventional methods, only one part is processed in each cycle, due to the short axial dimensions, resulting in frequent reciprocation of the machine tool spindle slider in the bed guideway localized, and the spring collet clamping mechanism moves frequently. After a long time of work, it will cause excessive wear of the machine guideway, affecting the machining accuracy of the machine tool, and even cause serious machine scrap. The frequent action of the collet clamping mechanism will lead to damage to the control electronics. In order to solve the above problems, it is necessary to increase the spindle feed length and the action interval of the collet clamping mechanism, while not reducing productivity. It is envisioned that whether in a machining cycle in the processing of several parts, the spindle feed length for the length of a single part several times, and even up to the spindle's maximum operating distance, and the spring collet clamping mechanism of the action interval is extended to the original several times. More importantly, the original single-piece parts of the auxiliary time is spread over several parts, each part of the auxiliary time is greatly reduced, thus improving productivity. In order to realize this idea, I computer to computer programming in the main program and the concept of subroutine, if the geometric dimensions of the parts involved in the command field in a subroutine, and will be related to machine tool control command field and cut off the parts of the command field in the main program, each processing of a part, by the main program through the invocation of the subroutine commands to invoke the subroutine once, after the completion of the processing, jump back to the main program. Need to process several parts will call several subroutines, very conducive to increasing or decreasing the number of parts processed per cycle. The machining program prepared in this way is also more concise, easy to modify and maintain. It is worth noting that, due to the sub-program parameters in each call remain unchanged, while the spindle coordinates are always changing, in order to adapt to the main program, the sub-program must be used in the relative programming statements.
Reducing tool empty travel
In BIEJING-FANUC Power Mate O CNC lathe, the movement of the tool is dependent on the stepping motor to drive, although in the program commands have a fast point positioning command G00, but compared with the feeding method of the ordinary lathe, but it still seems to be inefficient. Therefore, to improve the efficiency of the machine tool, it is necessary to improve the running efficiency of the tool. The empty travel of the tool is the distance run by the tool to approach the workpiece and return to the reference point after cutting is completed. As long as the tool empty stroke is reduced, the running efficiency of the tool can be improved. (For point-controlled CNC lathes, only high positioning accuracy is required, and the positioning process can be as fast as possible, while the movement route of the tool relative to the workpiece is irrelevant.) In terms of machine adjustment, the initial position of the tool should be arranged as close as possible to the bar. In terms of the program, according to the structure of the parts, the use of as few tools as possible to process the parts so that the tools in the installation of each other as far as possible dispersed, very close to the bar when each other will not interfere; on the other hand, due to the actual initial position of the tool has been changed from the original, it is necessary to modify the tool's reference point position in the program, so that it is in line with the actual situation, at the same time with the fast point positioning command, the empty travel of the tool can be controlled within the minimum range to improve the efficiency of machine tool machining.
Optimizing parameters, balancing tool loads, and reducing tool wear
These are the main reasons why it's so important to optimize your tooling.