CNC lathes are one of the most widely used CNC machine tools. It is mainly used for cutting inner and outer cylindrical surfaces of shaft parts or disc parts, inner and outer conical surfaces with arbitrary cone angles, complex rotating inner and outer curved surfaces, cylinders, and conical threads. It can also perform grooving, drilling, reaming, and reaming. Hole and boring etc.
The CNC machine tool automatically processes the processed parts according to the pre-programmed processing program. We compile the machining process route, process parameters, tool motion trajectory, displacement, cutting parameters and auxiliary functions of the part into a machining program list according to the instruction code and program format specified by the CNC machine tool, and then record the contents of the program list On the control medium, it is then input into the numerical control device of the numerical control machine tool to direct the machine tool to process the parts.
Table Of Contents
- Institutional Introduction
- Selection Principle
- Basic Composition
- Installation Method
- Commissioning And Acceptance
- Three Elements
- Tooling Lathe
- Structure And Code
- Number Programming
- Contents And Steps
- Mathematical Processing
- Programming Skills
- Tool selection Method
- Application Of Frequency Converter
- Quality Control
- Processing Object
- Conditions Of Use
- Country Code
- Development Trend
- Cnc Turning Machine
Numerical control (English name: Numerical Control, abbreviated: NC) technology refers to a technology that uses digital instructions composed of numbers, characters and symbols to control the motion of one or more mechanical equipment. Numerical control generally uses general-purpose or special-purpose computers to realize digital program control. Therefore, numerical control is also called Computerized Numerical Control (Computerized Numerical Control), or CNC for short. It is generally called CNC abroad, and the concept of NC is rarely used. What it controls is usually the position, angle, speed and other mechanical quantities and the switch quantity related to the flow of mechanical energy. The generation of numerical control relies on the emergence of data carriers and binary data operations. In 1908, the perforated sheet metal interchangeable data carrier came out; at the end of the 19th century, a control system with paper as the data carrier and auxiliary functions was invented; in 1938, Shannon conducted rapid data calculation and transmission at the Massachusetts Institute of Technology in the United States. Laid the foundation of modern computers, including computer digital control systems. Numerical control technology is developed in close combination with machine tool control. In 1952, the first CNC machine tool came out, which became an epoch-making event in the history of the world machinery industry and promoted the development of automation.
Numerical control technology is also called Computerized Numerical Control (CNC, Computerized Numerical Control), which is a technology that uses computers to realize digital program control. This technology uses a computer to execute the sequential logic control function of the movement track of the device and the operation of the peripherals according to the control program stored in advance. Because the computer is used to replace the original numerical control device composed of hardware logic circuits, the storage, processing, calculation, and logic judgment of input operation instructions can be realized by computer software, and the microscopic instructions generated by the processing can be transmitted to The servo drive device drives the motor or hydraulic actuator to drive the equipment to run.
Traditional mechanical processing is performed by manual operation of ordinary machine tools. During processing, the mechanical tool is shaken by hand to cut metal, and the accuracy of the product is measured by the eye with tools such as calipers. Modern industry has already used computer digitally controlled machine tools for operations. CNC machine tools can automatically process any products and parts directly in accordance with the procedures programmed by technicians in advance. This is what we call CNC machining. Numerical control processing is widely used in any field of all mechanical processing, and it is the development trend and important and necessary technical means of mold processing.
CNC Machine Tools
CNC lathes, also known as CNC lathes, are computer digital controlled lathes. They are the most widely used and covered CNC machine tools in China, accounting for about 25% of the total number of CNC machine tools. CNC machine tools are mechatronics products that integrate multiple technologies such as machinery, electricity, hydraulics, pneumatics, microelectronics, and information. It is a working mother machine with the advantages of high precision, high efficiency, high automation and high flexibility in mechanical manufacturing equipment. The technical level of CNC machine tools and the percentage of their output and total ownership of metal cutting machine tools is one of the important indicators to measure a country’s national economic development and the overall level of industrial manufacturing. CNC lathe is one of the main varieties of CNC machine tools. It occupies a very important position in CNC machine tools. For decades, it has been widely valued by countries all over the world and has been rapidly developed.
Since the advent of CNC lathes in the 1950s, due to the use of CNC lathes to process complex-shaped parts in single-piece production and small-batch production, it not only improves labor productivity and processing quality, but also shortens the production preparation cycle and reduces the skill of workers. Proficiency requirements. Therefore, it has become an important development direction for realizing technological innovation and technological revolution in single-piece, small-batch production. Countries all over the world are also vigorously developing this new technology.
We know that for mass-produced parts, the use of automated and semi-automated lathes can already automate the production process. However, for single-piece, small-batch production parts, achieving automation has always been a problem. For a long period of time in the past, it has always been unable to solve it satisfactorily. Especially for parts with complex shapes and high machining accuracy requirements, they have been at a standstill on the road to automation. Although some application profiling devices have solved part of it, practice has proved that profiling lathes still cannot completely solve this problem.
The emergence of CNC lathes (machine tools) has opened up a broad way to fundamentally solve this problem, so it has become an important development direction in mechanical processing.
CNC machine tool is the abbreviation of digital control machine tool, which is an automatic machine tool equipped with a program control system. The control system can logically process the program with control codes or other symbolic instructions, and decode it, so as to make the machine tool move and process the parts.
Compared with ordinary machine tools, CNC machine tools have the following characteristics:
- High processing precision and stable processing quality;
- Multi-coordinate linkage can be carried out, and parts with complex shapes can be processed;
- When machining parts change, generally only need to change the numerical control program, which can save production preparation time;
- The machine tool itself has high precision and high rigidity, can choose a favorable processing amount, and has high productivity (generally 3~5 times of ordinary machine tools);
- The machine tool has a high degree of automation, which can reduce labor intensity;
- Higher requirements for the quality of operators and higher technical requirements for maintenance personnel.
Determine the process requirements of typical parts and the batch of processed workpieces. The function that the CNC lathe should have is to make preparations and the prerequisite for a reasonable selection of CNC lathes: meet the process requirements of typical parts.
The process requirements of typical parts are mainly the structural size, processing range and accuracy requirements of the parts. According to the accuracy requirements, that is, the dimensional accuracy, positioning accuracy and surface roughness of the workpiece, the control accuracy of the CNC lathe is selected. Choose based on reliability. Reliability is a guarantee for improving product quality and production efficiency. The reliability of a CNC machine tool means that the machine tool runs stably for a long time without failure when it performs its functions under specified conditions. That is, the mean time between failures is long, even if there is a failure, it can be restored in a short time and put into use again. Choose machine tools with reasonable structure, well-manufactured, and mass-produced machines. Generally, the more users, the higher the reliability of the CNC system.
Machine tool accessories and tools
Machine tool accessories, spare parts and their supply capacity, cutting tools, are very important for CNC lathes and turning centers that have been put into production. When choosing a machine tool, carefully consider the compatibility of tools and accessories.
Manufacturers generally choose products from the same manufacturer, and at least buy the control system of the same manufacturer, which brings great convenience to the maintenance work. Teaching units require students to be knowledgeable and knowledgeable, so it is a wise choice to choose different systems and to equip them with various simulation software.
Performance and price ratio to choose
Make sure that the functions and accuracy are not idle, not wasted, and do not choose functions that have nothing to do with your own needs.
Protection of machine tools
When needed, the machine tool can be equipped with fully enclosed or semi-enclosed protective devices and automatic chip removal devices.When choosing CNC lathes and turning centers, the above-mentioned principles should be considered comprehensively.
The CNC lathe is composed of CNC device, bed, headstock, tool post feed system, tailstock, hydraulic system, cooling system, lubrication system, chip conveyor and other parts.
Parallel double spindle CNC lathe
CNC lathes are divided into two types: vertical CNC lathes and horizontal CNC lathes.
Vertical CNC lathes are used for the turning of disk parts with larger turning diameters.
Horizontal CNC lathes are used for turning processing of parts with long axial dimensions or small disks.
Horizontal CNC lathes can be further divided into economical CNC lathes, ordinary CNC lathes and turning machining centers according to their functions.
Economical CNC lathe: a simple CNC lathe formed by reforming the turning feed system of an ordinary lathe with a stepping motor and a single-chip microcomputer. The cost is low, the degree of automation and functions are relatively poor, and the machining accuracy of turning is not high. It is suitable for turning machining of rotary parts with low requirements.
Ordinary CNC lathe: a CNC lathe that is specially designed in structure according to the requirements of turning processing and is equipped with a general CNC system. The numerical control system has strong functions, high degree of automation and processing accuracy, and is suitable for turning processing of general rotary parts. This CNC lathe can control two coordinate axes at the same time, namely the x-axis and the z-axis.
Turning machining center: On the basis of ordinary CNC lathes, a C axis and power head are added. More advanced machine tools also have a tool magazine, which can control the three coordinate axes of X, Z and C. The linkage control axis can be (X, Z), (X, C) or (Z, C). Due to the addition of the C-axis and milling power head, the processing functions of this CNC lathe are greatly enhanced. In addition to general turning, it can also perform radial and axial milling, surface milling, and holes and diameters whose centerline is not at the center of the part’s rotation. Drilling and other processing of the hole.
Hydraulic chuck and hydraulic tailstock
Hydraulic chuck is an important accessory for clamping workpieces during CNC turning. Ordinary hydraulic chucks can be used for general rotary parts; special chucks are required for parts whose clamping parts are not cylindrical; use bar materials directly A spring chuck is required when machining parts. For parts with a large ratio of axial size to radial size, it is necessary to use a live center mounted on a hydraulic tailstock to support the end of the part to ensure the correct processing of the part. The tailstock has ordinary hydraulic tailstock and programmable hydraulic tailstock.
Universal tool holder
CNC lathes can be equipped with two tool holders:
- Special tool holder: developed by the lathe manufacturer, the tool holder used is also special. The advantage of this tool holder is low manufacturing cost, but lacks versatility.
- Universal tool holder: The tool holder is produced according to certain general standards (such as VDI, German Engineers Association). CNC lathe manufacturers can choose and configure according to the functional requirements of CNC lathes.
Milling power head
After the milling power head is installed on the tool post of the CNC lathe, the processing capacity of the CNC lathe can be greatly expanded. Such as: using a milling power head for axial drilling and milling of axial grooves.
Tools for CNC lathes
When turning parts on a CNC lathe or turning machining center, the position of the tool on the tool holder should be reasonably and scientifically arranged according to the tool holder structure of the lathe and the number of tools that can be installed, and attention should be paid to avoid the tool when the tool is stationary and working. Interference phenomenon with the machine tool, the tool and the workpiece, and the tool.
Machine tool composition
The host machine is the main body of the CNC machine tool, including the machine body, column, spindle, feed mechanism and other mechanical parts. It is a mechanical part used to complete various cutting processes.
The numerical control device is the core of the numerical control machine tool, including hardware (printed circuit board, CRT display, key box, paper tape reader, etc.) and corresponding software, used to input digital part programs, and complete the storage of input information and data Transformation, interpolation calculation and realization of various control functions.
The driving device, which is the driving part of the CNC machine tool actuator, includes the spindle drive unit, the feed unit, the spindle motor, and the feed motor. He realizes the spindle and feed drive through the electric or electro-hydraulic servo system under the control of the numerical control device. When several feeds are linked, the processing of positioning, straight line, plane curve and space curve can be completed.
Auxiliary devices, some necessary supporting parts of index-controlled machine tools, are used to ensure the operation of CNC machine tools, such as cooling, chip removal, lubrication, lighting, monitoring, etc. It includes hydraulic and pneumatic devices, chip removal devices, exchange tables, CNC turntables and CNC indexing heads, as well as cutting tools and monitoring and testing devices.
Programming and other ancillary equipment can be used to program and store parts outside the machine.
Since the Massachusetts Institute of Technology developed the world’s first CNC machine tool in 1952, CNC machine tools have been widely used in the manufacturing industry, especially in the automotive, aerospace, and military industries. CNC technology is used in both hardware and software. , Both have rapid development.
Lifting and transportation
The hoisting and positioning of the machine tool should use the special hoisting tool provided by the manufacturer, and other methods are not allowed. No special lifting tools are required, and steel wire ropes should be used to lift and place them in accordance with the specified positions in the instructions.
Foundation and location
The machine tool should be installed on a firm foundation, and the location should be far away from the source of vibration; avoid sunlight and heat radiation; be placed in a dry place to avoid the influence of humidity and airflow. If there is a vibration source near the machine tool, an anti-vibration trench must be set around the foundation.
Machine tool installation
The machine tool is placed on the foundation, it should be leveled in a free state, and then the anchor bolts should be evenly locked. For ordinary machine tools, the level should not exceed 0.04/1000mm, and for high-precision machine tools, the level should not exceed 0.02/1000mm. When measuring the installation accuracy, it should be carried out at a constant temperature, and the measuring tool should be used after a fixed temperature period. When installing the machine tool, every effort should be made to avoid forced deformation of the machine tool. Certain parts of the machine tool should not be disassembled casually when the machine tool is installed. The disassembly of the parts may cause the redistribution of the internal stress of the machine tool, thereby affecting the accuracy of the machine tool.
Preparation before commissioning
After the geometric accuracy of the machine tool is qualified, the whole machine needs to be cleaned. Use cotton or silk cloth soaked with cleaning agent, not cotton yarn or gauze. Clean the anti-rust oil or anti-rust paint applied to protect the guide rail surface and the machined surface when the machine tool leaves the factory. Clean the dust on the outer surface of the machine tool. Coat each sliding surface and working surface with lubricating oil specified by the machine tool.
Check carefully whether all parts of the machine tool are filled with oil as required, and whether enough coolant is added to the cooling box. Whether the oil of the hydraulic station of the machine tool and the lubrication device of the automatic room reaches the position specified by the oil level indicator.
Check whether the switches and components in the electrical control box are normal, and whether the integrated circuit boards are in place.
The centralized lubrication installation is started by electrifying, so that the lubricating parts and the lubricating oil circuit are filled with lubricating oil. Make all the preparations before each part of the machine tool moves.
Commissioning And Acceptance
The acceptance of CNC lathes should be carried out in accordance with the “Technical Requirements for the Manufacturing and Acceptance of CNC Horizontal Lathes” promulgated and implemented by the state. During the acceptance process, if disputes occur, they should be resolved through consultations based on relevant national standards.
Check the items in the box one by one according to the random packing list and the specific attachment list in the contract. And make inspection records. It has the following contents:
- Whether the packing box is intact, whether the appearance of the machine tool is obviously damaged, it is rust, peeling paint;
- Whether there is technical information and whether it is complete;
- Types, specifications and quantities of accessories;
- Variety, specification and quantity of spare parts;
- Tool variety, specification and quantity;
- Knives (blade) varieties, specifications and quantities;
- Installation accessories;
- Variety, specification and quantity of electrical components;
- Start-up test
After the installation and commissioning of the machine tool is completed, the manufacturer will be notified to send someone to commission the machine tool. The main tests are as follows:
1. Various manual tests
- a. Manual operation test Test the accuracy of manual operation.
- b. Jog test
- c. Spindle shift test
- d. Overtravel test
2. Function test
- a. Use buttons, switches, and manual operations to perform functional tests on the machine tool. The flexibility, stability and functional reliability of the test action.
- b. Choose any spindle speed for continuous test of spindle start, forward rotation, reverse rotation and stop. No less than 7 operations.
- c. Spindle high, medium and low speed conversion test. The allowable difference between the command value and the displayed value of the speed is ±5%.
- d. Choose one kind of feed, and continuously do work feed and rapid feed tests on the entire stroke of XZ axis. The rapid stroke should be greater than 1/2 of the full stroke. The positive and negative side and continuous operation shall not be less than 7 times.
- e. Perform low, medium, and high feed rate conversion tests on all strokes of X and Z axes. The turret tool post performs various indexing clamping tests.
- f. The hydraulic, lubrication, and cooling systems are tested for sealing, lubrication, and cooling to ensure no leakage.
- g. The chuck is tested for clamping, unclamping, flexibility and reliability.
- h. The spindle is tested for forward rotation, reverse rotation, stop and change of spindle speed.
- i. The turret tool post performs a forward and reverse direction indexing test.
- j. The feed mechanism is tested for rapid feed conversion for low, medium and high feeds.
- k. Test feed coordinate overtravel, manual data input, position display, reference point return, program serial number indication and retrieval, program pause, program deletion, address line interpolation, linear cutting wandering, taper cutting cycle, thread cutting cycle, circle Reliability and flexibility of functions such as arc cutting cycle, tool position compensation, pitch compensation, clearance compensation, etc.
3. Idling test
a. The running test of the active mechanism should not be less than 1 hour in the highest speed range, the temperature value of the spindle bearing should not exceed 70℃, and the temperature rise value should not exceed 40℃;
b. Continuous dry running test, the exercise time is no less than 8 hours, and each cycle time is no more than 15 minutes. Stop at the end of each cycle and simulate the movement of the loosened workpiece. Stop for no more than one minute before continuing to run.
4. Load test
The user prepares the drawings and blanks of typical parts, and programs and enters the program under the guidance of the debugger of the manufacturer to select the cutting tool and cutting amount. The load test can be carried out in the following three steps: rough turning, heavy cutting, and fine turning. Each step is divided into single cutting and cycle program cutting. After each cutting is completed, the actual size of the processed part of the part is checked and compared with the command value, and the running accuracy of the machine tool under load conditions, that is, the overall machining accuracy of the machine tool, and the indexing accuracy of the turret tool post are checked.
After the machine tool is unpacked and accepted, the functional test, the dry running test, and the load test are completed, and the qualified products are processed, the acceptance and transfer procedures can be handled. If there is any problem, the manufacturer shall be responsible for solving it.
The basic principle of determining the three elements: first determine the amount of back-grabbing according to the cutting requirements, then look up the table to get the feed, and then look up the table to calculate the main cutting speed through the formula.
In many cases, we can determine the value of these three elements through empirical data.
Practice has proved that the selection of a reasonable cutting amount is related to many factors such as machine tools, tools, workpieces and processes. The method of reasonably selecting the processing dosage is as follows:
- ① When roughing, it is mainly necessary to ensure higher production efficiency, so you should choose a larger back-grab amount, a larger feed rate, and a medium-low cutting speed U.
- ②In the finishing process, the size and surface accuracy of the parts are mainly ensured, so choose a smaller back-cutting amount, a smaller feed amount, and a higher cutting speed.
- ③When roughing, it is generally necessary to give full play to the potential of the machine tool and the cutting ability of the tool. When semi-finishing and finishing in a CNC lathe factory, it should focus on how to ensure the quality of the processing, and on this basis, try to increase the productivity as much as possible. When selecting the cutting amount, the CNC lathe factory should ensure that the tool can complete a part or ensure that the durability of the tool is not less than one work shift, and at least not less than half the working time of the work shift. The specific values of the CNC lathe factory should be selected according to the specifications in the machine tool manual, tool durability and practical experience.
The selection of the amount of back-grabbing: The selection of the amount of back-grabbing should be determined according to the rigidity of the machine tool, fixture and workpiece, and the power of the machine tool. If the process system permits, choose a larger amount of back-grabbing as much as possible. Except for the allowance left for later processes, the remaining rough machining allowance should be cut at one time as much as possible to minimize the number of passes.
Usually on a medium-power machine tool, the back-cutting amount for roughing is 8~10 mm (single side). The semi-finish machining of the CNC lathe machine factory is 0.5~5 mm; the precision machining is 0.2~1.5 mm.
The determination of the feed rate: When the quality of the workpiece can be guaranteed, in order to improve the productivity, a higher feed rate can be selected. When CNC lathe factory cuts, turns deep holes or finish turning, it is advisable to choose a lower feed speed. The feed speed should be compatible with the spindle speed and the amount of back tool. When roughing, the selection of feed is limited by cutting force.
Determine the processing route
The processing route is the movement track and direction of the tool relative to the part during the processing of the index-controlled machine tool.
- It should be able to guarantee the processing accuracy and surface roughness requirements;
- The processing route should be shortened as much as possible to reduce the idle travel time of the tool.
The relationship between processing route and processing allowance
Under the condition that the CNC lathe has not yet reached the popular use, the excess margin on the blank, especially the margin containing the forging and casting hard skin layer, should be arranged on the ordinary lathe for processing. If you must use a CNC lathe to process, you need to pay attention to the flexible arrangement of the program.
Main points of fixture installation
The connection between the hydraulic chuck and the hydraulic clamping cylinder is realized by a tie rod. The main points of hydraulic chuck clamping are as follows: First, use a moving hand to remove the nut on the hydraulic cylinder, remove the pull tube, and pull it out from the back of the spindle, and then use it. Remove the fixing screw of the chuck by moving your hand to remove the chuck.
Structure And Code
Numerical control car program can be divided into three parts: program start, program content and program end.The beginning of the program
Mainly define the program number, call up the part processing coordinate system, processing tool, start the spindle, turn on the coolant and other aspects. The maximum spindle speed limit defines G50 S2000, and sets the maximum spindle speed to 2000RPM, which is a very important command for CNC lathes.
If the coordinate system definition is not specified, the CNC system defaults to the G54 coordinate system.
Return to the reference point command G28 U0, in order to avoid collision or interference between the tool post and the workpiece or fixture during the tool change, an effective method is that the machine tool first returns to the machine reference point in the X-axis direction and leaves the spindle for a safe period of time. distance.
Tool definition G0 T0808 M8, automatically adjust No. 8 left offset tool No. 8 tool compensation, turn on coolant.
Spindle speed definition G96 S150 M4, constant linear speed S function definition, S function enables the spindle speed command function of CNC lathe, there are two expressions, one is r/min or rpm as the unit of measurement. The other is based on 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: Speed command, define and set the speed per minute.
- G96: Constant surface speed command, so that the cutting speed at any position on the workpiece is the same.
Program content part
The content of the program is the main part of the entire program and consists of multiple program segments. Each program segment is composed of several words, and each word is composed of address code and several numbers. The common ones are the program segments composed of G and M commands and the coordinate points of each axis, and the function definition of the feed amount has been added.
F function refers to the function of feed speed. There are two ways to express the feed speed of CNC lathes. One is the feed per revolution, which is expressed in mm/r. It is mainly used for the feed of turning. The other is the same as the CNC milling machine, which uses the feed per minute, which is expressed in mm/min. Mainly used for milling feed in turning and milling machining centers.
End of program
At the end of the program, it is necessary for the tool post to return to the reference point or machine tool reference point, which is the safe position for the next tool change. At the same time, the spindle stops, the coolant is turned off, and the program chooses to stop or end the program.
The reference point return command G28U0 is the machine reference point of the X-axis direction, and G0 Z300.0 is the reference point of the Z-axis direction.
The stop command M01 is a selective stop command, which is valid only when the device’s selective stop switch is turned on; M30 is a program end command. When executed, the coolant, feed, and spindle all stop. The numerical control program and numerical control equipment are reset and returned to the original state before processing, to prepare for the next program run and restart of numerical control processing.
There are three methods for programming CNC machine tools: manual programming, automatic programming and machining center CAD/CAM.
Manually complete part pattern analysis, process processing, numerical calculation, writing program list until program input and inspection. It is suitable for point processing or parts with less complex geometric shapes, but it is very time-consuming and prone to errors when compiling complex parts.
Using a computer or a programming machine to complete the process of compiling a part program is very convenient for complex parts.
Use CAD/CAM software to realize automatic programming of modeling and images. The most typical software is Master CAM, which can complete the programming of milling two-coordinate, three-coordinate, four-coordinate and five-coordinate, turning, and wire cutting. Although this type of software has a single function, it is simple and easy to learn, and the price is low.
The main content of CNC machine tool programming
Analyze the part drawings, determine the processing process, perform mathematical processing, write program lists, make control media, perform program inspections, input programs, and test workpieces.
Steps of CNC machine tools
Analyze the drawing and process of the part, analyze the geometric shape, size and technical requirements of the part according to the drawing, clarify the processing content and requirements, determine the processing plan, determine the processing sequence, design the fixture, select the tool, determine the reasonable path and choice of the tool Reasonable cutting amount, etc.
At the same time, the functions of the CNC system and the capabilities of the CNC machine should be used to correctly select the tool setting point and cut-in method to minimize auxiliary time such as tool change and indexing.
Contents And Steps
Before programming, first establish a workpiece coordinate system according to the geometric characteristics of the part.
The function of the numerical control system formulates the processing route according to the requirements of the part drawing, and first calculates the movement trajectory of the tool on the established workpiece coordinate system. For parts with relatively simple shapes (such as parts composed of straight lines and arcs), you only need to calculate the coordinate values of the start point, end point of the geometric element, the center of the arc, and the intersection or tangent point of the two geometric elements.
Compile part program list
After the processing route and process parameters are determined, the part program list is compiled according to the designated code and block format specified by the numerical control system.
The structure of CNC machining program
1. Program composition: It is composed of multiple program segments.
- O0001; O (FANUC-O, AB8400-P, SINUMERIK8M-%) function specifies the program number, and each program number corresponds to a machined part.
- N010 G92 X0 Y0; semicolon means the end of the block
- N020 G90 G00 X50 Y60;
- …; subroutines can be called.
- N150 M05;
- N160 M02;
2. Program segment format
- ①Word address format: such as N020 G90 G00 X50 Y60;The most commonly used format, modern CNC machine tools use it. The address N is the block number, the address G and the number 90 constitute the word address for the preparation function,….
- ② Variable block format: such as B2000 B3000 B B6000;Use the separator B to open each word. If there is no data, the separator cannot be omitted. Commonly used in CNC wire cutting machine tools, in addition, there are also 3B programming formats.
- ③Fixed sequence program segment format: such as 00701+0;The robot controlled by Siemens system is wrong, the above program segment means: N007 G01 X+02500 Y-13400 F15 S30 M02;
The mathematical processing of the part drawing is mainly to calculate the size of the part processing track, that is, to calculate the coordinates of the base point and node of the part processing contour, or the coordinates of the base point and node of the tool center contour, in order to compile the processing program.
Calculation of base point coordinates
Generally, CNC machine tools only have linear and circular interpolation functions. For a plane contour composed of straight lines and circular arcs, the main task of numerical calculation during programming is to find the coordinates of each base point.
1. The meaning of the base point
The point of intersection or tangency of the different geometrical lines that make up the contour of the part is called the base point. The base point can be directly used as the starting point or end point of its motion trajectory.
2. The content of direct calculation
According to the requirements of filling in the processing program sheet, the content of the direct calculation of the base point includes: the coordinates of the start and end points of each motion track in the selected coordinate system, and the center coordinates of the arc motion track.
The method of direct calculation of the base point is relatively simple, and can generally be completed manually according to the known conditions given by the part drawing. That is to use the relevant knowledge of algebra, trigonometry, geometry or analytic geometry according to the given size on the part drawing to directly calculate the value. When calculating, pay attention to leave enough digits after the decimal point to ensure sufficient accuracy.
Calculation of node coordinates
For some plane contours composed of non-circular equation curve Y=F(X), such as involutes, Archimedes spirals, etc., they can only be approximated by straight lines and arcs that can be machined. At this time, the task of numerical calculation is to calculate the coordinates of the node.
1. Definition of node
When the non-circular curve contour parts are processed by the numerical control machine tool that does not have the non-circular curve interpolation function, in the preparation of the processing program, multiple straight line segments or arcs are often used to approximate the non-circular curve. This is called fitting deal with. The intersection or tangency of the fitted line segments is called a node.
2. Calculation of node coordinates
The calculation of node coordinates is difficult and workload is relatively large, so it is often completed by computer, if necessary, it can also be calculated manually. Commonly used are straight line approximation method (equal spacing method, equal step length method, and equal error method) and arc approximation method .
The development of science and technology has led to the acceleration of product upgrading and the diversification of people’s needs, and the production of products has also tended to diversify in variety and small in batches. In order to adapt to this change, numerical control (NC) equipment plays an increasingly important role in enterprises. As a national key vocational school, our school has purchased BIEJING-FANUC Power Mate O CNC lathes in order to conform to the trend of the times and focus on the construction of CNC majors. Compared with ordinary lathes, it has a significant advantage: strong adaptability to parts changes, replacement parts only need to change the corresponding program, simple adjustments to the tool can make qualified parts, and win the opportunity to save costs. . However, to give full play to the role of CNC machine tools, not only good hardware (such as high-quality tools, machine accuracy, etc.), but also software: programming, that is, programming is reasonable and efficient according to the characteristics of different parts. Processing procedures. Through many years of programming practice and teaching, I have explored some programming skills.
Although the processing flexibility of CNC lathes is superior to that of ordinary lathes, there is still a certain gap between the production efficiency of a certain kind of parts and ordinary lathes.
Therefore, improving the efficiency of CNC lathes has become the key, and the reasonable use of programming skills to compile high-efficiency machining programs often has unexpected effects on improving the efficiency of machine tools.
1. Flexible setting of reference points
BIEJING-FANUC Power Mate O CNC lathe has two axes, namely spindle Z and tool axis X. The center of the bar is the origin of the coordinate system. When each tool approaches the bar, the coordinate value decreases, which is called feed; otherwise, the coordinate value increases, which is called retract. When retreating to the position when the tool started, the tool stops. This position is called the reference point. The reference point is a very important concept in programming. Every time an automatic cycle is executed, the tool must return to this position to prepare for the next cycle. Therefore, before executing the program, the actual positions 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 quantity of the tool used, and shorten the idle stroke of the tool. Thereby improving efficiency.
2. Turn zero into a whole method
In low-voltage electrical appliances, there are a large number of short-pin shaft parts whose length-to-diameter ratio is about 2 to 3, and the diameter is mostly below 3mm. Due to the small geometric size of the parts, it is difficult to clamp on ordinary instrument lathes and the quality cannot be guaranteed. If you program according to the conventional method, only one part is processed in each cycle. Due to the short axial dimension, the machine tool spindle slide block frequently reciprocates in the bed guide rail part, and the spring chuck clamping mechanism moves frequently.
After working for a long time, it will cause local excessive wear of the machine tool rails, affect the machining accuracy of the machine tool, and even cause the machine tool to be scrapped. Frequent actions of the clamping mechanism of the spring chuck will cause damage to the control electronics. To solve the above problems, it is necessary to increase the feed length of the spindle and the action interval of the spring chuck clamping mechanism without reducing productivity. From this, it is conceived whether it is possible to process several parts in one machining cycle, the feed length of the spindle is several times the length of a single part, and it can even reach the maximum travel distance of the spindle, and the action time interval of the spring chuck clamping mechanism is correspondingly extended. Several times the original. More importantly, the original auxiliary time of a single part is divided among several parts, and the auxiliary time of each part is greatly shortened, thereby improving production efficiency. In order to realize this idea, the concept of the main program and subprograms in computer-to-computer programming, if the command fields related to the geometric dimensions of the parts are placed in a subprogram, the command fields related to machine tool control and the command fields for cutting off parts Put it in the main program, each time a part is processed, the main program calls the subprogram once by calling the subprogram command. After the processing is completed, it jumps back to the main program. Calling several subroutines when several parts need to be processed is very helpful to increase or decrease the number of parts processed in each cycle. The processing program compiled in this way is also relatively simple and clear, which is easy to modify and maintain. It is worth noting that since the parameters of the subroutine remain unchanged every time it is called, and the coordinates of the spindle are changing all the time, in order to adapt to the main program, relative programming statements must be used in the subroutine.
3. Reduce the idle stroke of the tool
In the BIEJING-FANUC Power Mate O CNC lathe, the movement of the tool is driven by a stepping motor. Although there is a fast point positioning command G00 in the program command, it is still inefficient compared with the feed mode of the ordinary lathe. high. Therefore, in order to improve the efficiency of the machine tool, the operating efficiency of the tool must be improved. The idle travel of the tool refers to the distance traveled by the tool when it approaches the workpiece and returns to the reference point after cutting. As long as the idle stroke of the tool is reduced, the operating 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 path of the tool relative to the workpiece is irrelevant.) In terms of machine tool adjustment, the initial position of the tool should be arranged as much as possible. It may be close to the bar. In terms of program, according to the structure of the part, use as few tools as possible to process the parts so that the tools are dispersed as much as possible during installation, and they will not interfere with each other when they are very close to the bar. On the other hand, due to the actual initial The position has changed from the original. The reference point position of the tool must be modified in the program to make it consistent with the actual situation. At the same time, with the fast point positioning command, the empty stroke of the tool can be controlled within the minimum range. Thereby improving the machining efficiency of the machine tool.
4. Optimize parameters
Optimize parameters, balance tool load and reduce tool wear
Tool selection Method
Because CNC lathe processing is a high-precision work, and its processing procedures are concentrated and the number of parts clamping is small, so higher requirements are put forward for the CNC tools used. The following Dongguan PTJ Metal Products Co., Ltd. will introduce you .
When choosing tools for CNC machine tools, the following issues should be considered
- ① The type, specification and accuracy grade of CNC tools should be able to meet the requirements of CNC lathe processing.
- ②High precision. In order to meet the high precision and automatic tool change requirements of CNC lathe processing, the tool must have high precision.
- ③High reliability. To ensure that there will be no accidental damage and potential defects of the tool in the CNC machining, which will affect the smooth progress of the machining, the tool and the accessories combined with it must have good reliability and strong adaptability. Precision metal processing
- ④High durability. The tools processed by CNC lathes, whether in roughing or finishing, should have higher durability than those used in ordinary machine tools, so as to minimize the number of times of changing or grinding tools and tool setting, thereby improving the processing of CNC machine tools. Efficiency and guarantee processing quality.
⑤Good chip breaking and chip removal performance. In CNC lathe processing, chip breaking and chip removal are not handled manually like ordinary machine tools. Chips are easy to wrap around the tool and workpiece, which will damage the tool and scratch the machined surface of the workpiece, and even cause injury and equipment accidents. , Which affects the processing quality and the safe operation of the machine tool, so the tool is required to have better chip breaking and chip removal performance.
Application Of Frequency Converter
When the CNC lathe is started, the current of the motor will be 5-6 times higher than the rated value, which will not only affect the service life of the motor but also consume more power. The system will have a certain margin in the motor selection during the design. The speed of the motor is fixed, but in actual use, it sometimes needs to run at a lower or higher speed, so it is very necessary to carry out frequency conversion transformation. The frequency converter can realize the soft start of the motor, achieve the purpose of energy saving and speed regulation by changing the input voltage frequency of the equipment, and can provide the equipment with protection functions such as overcurrent, overvoltage, and overload.
If the ordinary lathes used and the long-used lathes are not modified, and only new CNC lathes are purchased, it will increase the equipment cost of many manufacturers. Therefore, it is the only way for manufacturers to carry out numerical control transformation of ordinary lathes and long-used lathes.
As the numerical control transformation is more complicated and messy for the transformation manufacturers, how to control the quality of the transformed CNC machine tools is a problem that we have always needed to discuss. Here, we will talk about how to carry out the quality control of the transformed CNC lathes.
The CNC transformation of ordinary lathes is divided into new machine transformation and old machine transformation. The new machine transformation is when the user purchases an ordinary lathe or an ordinary light machine (referring to a lathe with only a headbox and longitudinal and transverse guides), and the transformation manufacturer performs numerical control according to its requirements Transformation. Old machine transformation means that the user refurbishes the used ordinary lathe or numerical control lathe and carries out numerical control transformation.
The old machine transformation includes the overhaul of the lathe and the user’s old machine parts transformation. Here, I will talk about the quality control method, focus on control points and inspection process of the transformation of CNC lathes in mechanical aspects.
Both the new machine transformation and the old machine overhaul lathe transformation must undergo the same transformation as follows
- ① Replace the X-axis and Z-axis screw rods, bearings, and motors.
- ②Add electric tool post and spindle encoder.
- ③Increase the drive device of the axial motor, limit the overtravel travel switch, install the frequency converter (customer needs) and the electrical parts required for processing and safety.
- ④Scrape the supporting surfaces of the X-axis and Z-axis screw rods at both ends, the ball screw bracket and the saddle, and the bed and the saddle rail pair.
- ⑤Add protective facilities as needed, such as protective covers for all-directional screw rods, safety protective doors, and protective devices for travel switches.
The difference between the new machine transformation and the old machine overhaul lathe transformation
- ① The main shaft and tailstock of the new machine have not been modified, and the main shaft and tailstock do not need to be modified.
- ②The old machine overhaul lathe has worn out the guide rails after long time use. In order to ensure that it can be used for a long time without deformation after the overhaul, it must undergo a quenching process and then grind the guide rails. After grinding the guide rails, the hardness of the guide rails must be ≥HRC47.
- ③The old machine overhaul lathe should modify and adjust the main shaft part and tailstock part according to customer needs.
Accuracy inspection of new machine transformation and overhaul machine tool transformation is an important item of inspection
Accuracy inspection implements JB/T8324.1-1996 “Accuracy of Simple CNC Horizontal Lathe”.
The accuracy and quality control of the new lathe transformation is as follows
- ① Shoveling inspection. The transformation of the new lathe includes the matching and scraping of the supporting surfaces of the X-axis and Z-axis screw rods, the matching and scraping of the ball screw bracket and the saddle, and the matching and scraping of the bed and the saddle rail pair. The main shaft and tailstock of the lathe have not been dismantled. The inspection method is as follows: paint with the mating surface, combine the mating surfaces, and rub against each other, then check the number of scraping points on the scraping surface, and check the degree of bonding with a feeler gauge at the joint.
- ② Inspection of the parallelism between the screw rod and the guide rail: When assembling the screw rod, the parallelism between the screw rod and the guide rail must be ≤ 0.02mm.
- ③In the G1 item of the accuracy test, the straightness of the guide rail in the vertical plane (only convex) should be guaranteed by the ordinary lathe manufacturer, not as a key inspection item.
- ④In the accuracy test, the accuracy of the spindle part G4, G5, and G6 should also be guaranteed by the ordinary lathe manufacturer, not as a key inspection item.
- ⑤The heights of the two centers of the head and tailstock of item G11 are guaranteed by ordinary lathe manufacturers, and are not regarded as key items for quality control of the transformation manufacturer.
Accuracy inspection of user overhaul lathe transformation
Since the guide rail has been ground and the reference level has changed, all items in the accuracy test must be inspected and strictly controlled to ensure the performance after the transformation.
Other important quality control points for the transformation of overhaul lathes and the transformation of new machines
1. Corrosion inspection: each horizontal and vertical rail surface, main shaft, main shaft flange, and hollow sleeve of tailstock.
2. Anti-rust measures must be taken on all exposed non-painted surfaces. For example, after cleaning, use lubricating grease for anti-rust inspection: the scraping surface, screw rod and bearing must be cleaned before assembling, and there must be no red lead powder, Iron shavings and other dirty materials; there is no dust or dirt inside the electric box and inside the protective cover.
3. Leakage inspection: the main shaft bearings and gears of the overhaul lathe must be kept lubricated, and the axial screw and bearings of the overhaul lathe and the new lathe must be lubricated, and there must be a cooling device, and the above lubrication and cooling of the joints , There should be no leakage in oil and water tanks.
4. Machine tool noise, temperature rise, speed, dry running test:
- ①The main shaft runs continuously for 4 minutes at various speeds, and the running time at the highest speed is not less than 2 hours. The dry running time of the whole machine is ≥16h, and the cyclic turning of arcs, threads, outer circles, end faces, etc. are carried out to simulate dry running tests.
- ②After the spindle bearing temperature is stable, measure the bearing temperature and temperature rise. Rolling bearings: temperature ≤70℃, temperature rise ≤40℃; sliding bearing: temperature ≤60℃, temperature rise ≤30℃.
- ③The noise pressure level of the machine tool is ≤83dB(A) under dry running conditions, and whether the machine tool has abnormal screaming or impact noise. The feed movement in each axis direction should be smooth, without obvious vibration, chattering and crawling.
- ④The continuous dry-running test of the machine tool has no failure, reliable and stable operation within the specified continuous dry-running time.
5. Transformation of user replacement parts (including maintenance of machine tool parts): As there are many transformation projects for lathe replacement parts, the main ones are replacement of spindle bearings, axial screws, axial motors, axial bearings and systems.
- ①Replace the spindle bearing: Since the replacement of the spindle bearing is to ensure the accuracy of the outer circle and end face, it is necessary to check the noise of the spindle first after the bearing is replaced. If there is no abnormality, the noise sound pressure level of the whole machine should not exceed 83dB (A) , And then inspect the processing accuracy and inspect the surface roughness of the processed workpiece.
- ②Replace the axial screw rod inspection: check the position accuracy of all directions to ensure that the treadmill runs within the specified range and there is no abnormal impact sound and noise in the axial operation. Replacement of the axial motor: As other items have not been modified, the inspection only checks the noise of the running machine, and there is no abnormal impact sound and noise in the axial operation. Check the axial reverse clearance to prevent the reverse difference caused by the assembly from not meeting the requirements during assembly.
- ③ Replacing the axial bearing: In the case of replacing the axial bearing, it is necessary to ensure that the axial reverse difference meets the requirements, and check for abnormal noise.
- ④Replacement system inspection: In the case of replacing the system, only check the system function, check whether the system has alarms, and check whether the test thread is normal (for lathes with encoders).
In hardware processing, all rotating parts that can be clamped on ordinary lathes can be processed on CNC lathes. However, CNC lathes have the characteristics of high machining accuracy, linear and arc interpolation, and automatic speed change during hardware processing. Its process range is much wider than ordinary machine tools.
The CNC lathe has good rigidity, high precision in manufacturing and tool setting, and can easily and accurately enter manual compensation and automatic compensation, so it can process parts with high dimensional accuracy. In addition, the tool motion of CNC turning is realized by high-precision interpolation motion and servo drive. In addition, the rigidity of the machine tool and the high manufacturing accuracy are high, so it can process the shape accuracy of the bus line straightness, roundness, cylindricity, etc. Highly demanding parts. For arcs and other curved contours, the degree of closeness between the processed shape and the geometric shape required on the drawing is much higher than that of the profiling lathe.
The CNC lathe has a constant linear speed cutting function, so the best linear speed can be selected to cut the conical surface and the end surface, so that the surface roughness value after turning is small and consistent, and the surface roughness value is small and uniform.
The CNC lathe can not only turn any straight, tapered and end-face threads of equal lead, but also can turn the threads with a smooth transition between variable lead and variable lead. When the CNC lathe is turning the thread, the spindle rotation does not need to be alternately changed like an ordinary lathe. It can cycle one knife after another without stopping until it is completed, so the efficiency of the CNC lathe’s thread is very high.
Conditions Of Use
The normal use of CNC lathes must meet the following conditions: the power supply voltage fluctuation at the location of the machine tool is small, the ambient temperature is less than 30 degrees Celsius, and the relative temperature is less than 80%.
The location of the machine tool should be far away from the vibration source, direct sunlight and thermal radiation, and humidity and airflow should be avoided. If there is a vibration source near the machine tool, an anti-vibration trench should be set around the machine tool. Otherwise, it will directly affect the machining accuracy and stability of the machine tool, and cause poor contact of electronic components, failures, and affect the reliability of the machine tool.
Generally, CNC lathes are installed in machining workshops, not only because of the large environmental temperature changes and poor use conditions, but also various electromechanicalequipment, resulting in large fluctuations in the power grid. Therefore, the location where the CNC lathe is installed requires strict control of the power supply voltage. The power supply voltage fluctuation must be within the allowable range and remain relatively stable. Otherwise it will affect the normal operation of the CNC system.
The ambient temperature of the CNC lathe is less than 30 degrees Celsius, and the relative temperature is less than 80%. Generally speaking, an exhaust fan or air cooler is arranged inside the numerical control electric control box to keep the electronic components, especially the central processing unit’s working temperature constant or the temperature difference changes very small. Excessive temperature and humidity will reduce the life of control system components and cause more failures. The increase in temperature and humidity and the increase in dust will cause adhesion on the integrated circuit board and cause short circuits.
Standard use of machine tools
When using the machine tool, the user is not allowed to change the parameters set by the manufacturer in the control system at will. The setting of these parameters is directly related to the dynamic characteristics of each part of the machine tool. Only the value of the gap compensation parameter can be adjusted according to the actual situation.
The user cannot replace the machine tool accessories at will, such as using a hydraulic chuck that exceeds the specification. When setting up accessories, the manufacturer fully considers the matching of various link parameters. Blind replacement causes mismatch of various link parameters, and even causes unexpected accidents.
The pressure of the hydraulic chuck, hydraulic tool rest, hydraulic tailstock, and hydraulic cylinder should be within the allowable stress range, and any increase is not allowed.
The CNC lathe is a high-precision and high-efficiency automatic machine tool. Equipped with a multi-station turret or power turret, the machine tool has a wide range of processing capabilities, and can process linear cylinders, oblique cylinders, arcs and various threads, grooves, worms and other complex workpieces. It has linear interpolation and arcs. Interpolate various compensation functions, and play a good economic effect in the mass production of complex parts. The maintenance of the inclined bed CNC lathe is analyzed as follows:
In order to ensure the working accuracy of the inclined bed CNC lathe and prolong its service life, reasonable maintenance work must be carried out on the self-use inclined bed CNC lathe. The maintenance of the lathe directly affects the processing quality and production efficiency of the workpiece. When the Taiwan Taiyu Precision CNC lathe runs for 500 hours, the first level maintenance is required.
The maintenance work of the inclined bed CNC lathe is mainly carried out by the operator, and the maintenance worker cooperates. During maintenance, you must first cut off the electric probe, and then perform maintenance according to the maintenance content and requirements.
CNC lathe preparation function G code (JB3208-83), G code (or G command) is a process command that needs to be pre-defined before interpolation operation of the CNC machine tool system to prepare for the interpolation operation, such as: coordinate plane selection, interpolation The designation of the compensation method, the designation of the fixed cycle functions such as hole machining, etc. The G code is composed of address G followed by two digits, commonly used G00~G99, and some modern CNC machine tools have been extended to three digits. G codes are divided into modal codes and non-modal codes according to function categories. 9 groups of a, c, d,…j, k, etc. The corresponding G code in the same group is called modal code, which means that once a certain G code in the group (such as G17 in group c) is designated, the function remains until it appears Any other code in the same group (such as G18 or G19) is invalid, otherwise it continues to be valid. So when editing the next block, if you need to use the same G code, you can omit it, which can simplify the processing program. The non-modal code is only valid in this block.
- 1. All G codes indicated by lowercase letters a, b, c, d, … are the same group of codes, which are called modal commands;
- 2. “#” means that if it is selected for special purpose, it must be stated in the program format description;
- 3. The letter (d) in the brackets in the second column can be cancelled or replaced by the letter d without brackets in the same column, or it can be cancelled or replaced by the letter (d) with brackets in the same column;
- 4. The codes of “no designation” and “never designation” respectively indicate that new functions can be designated and functions will never be designated when the standard is revised in the future;
- 5. When the CNC system does not have G53 to G59, G63 functions, it can be designated for other purposes.
China is a big manufacturing country, and the domestic market for CNC lathes is huge. Domestic CNC lathe manufacturers also have their own characteristics and compete in the market. This has formed two general types, one is a large manufacturer, which is characterized by high quality and high price; the other is a small manufacturer, which is characterized by high quality and low price.
With the continuous improvement of China’s R&D and manufacturing capabilities, China has gradually moved from importing CNC lathes to exporting, indicating the strong momentum of the development of my country’s CNC industry.
Programmable Logical Controller (PLC) is also a general-purpose automatic control device based on the Ao processor, which is used to complete various logical operations and sequential control of CNC machine tools, such as machine start and stop, workpiece Auxiliary actions such as clamping, tool replacement, coolant switch, etc. The PLC also accepts instructions from the machine tool operating panel: on the one hand, it directly controls the actions of the machine tool; on the other hand, it sends related instructions to the CNC for processing control and creation. The PLC in the CNC system has a built-in type and an independent type.
The operation of the CNC machine tool is realized through the man-machine operation panel, which is composed of the CNC panel and the machine tool panel.
The numerical control panel is the operation panel of the numerical control system, which is composed of a display and a manual data input (Manual Data Input, referred to as MDI) keyboard, which is also called an MD panel. The lower part of the display is often provided with a menu selection key, which is used to select a menu. In addition to various symbol keys, number keys, and function keys, the keyboard can also be set with user-defined keys. The operator can realize the system management through the keyboard and the display, and input, store, edit and modify the numerical control program and related data. During processing, the screen can dynamically display system status and fault diagnosis reports. In addition, the numerical control program and data can also be imported through the disk or the communication interface box.
The machine tool operation panel is mainly used for the operation of the machine tool in manual mode, and the operation of the machine tool in automatic mode or pre-sets. There are various buttons and selection switches on it, which are used for the start and stop of the machine tool and auxiliary equipment, the selection of processing methods, the selection of speed and override, etc.; there are also digital tubes and signal display. The operation panel of medium and small CNC machine tools is often integrated with the CNC panel, but there is a clear boundary between the two. The communication interface of the numerical control system, such as a serial interface, is permanent and located on the machine operation panel.
Since entering the 21st century, with the continuous development of CNC technology and the expansion of application fields, it has played an increasingly important role in the development of some important industries (IT, automobiles, light industry, medical, etc.) of the national economy and people’s livelihood, because these industries The digitization of required equipment has become a major trend of modern development. In general, CNC lathes present the following three development trends:
High speed and precision are the eternal goals of machine tool development. With the rapid development of science and technology, the renewal of mechanical and electrical products has accelerated, and the requirements for precision and surface quality of parts processing have become higher and higher. In order to meet the needs of this complex and changeable market, the current machine tools are developing in the direction of high-speed cutting, dry cutting and quasi-dry cutting, and the machining accuracy is constantly improving. On the other hand, the successful application of electric spindles and linear motors, ceramic ball bearings, high-precision large-lead hollow internal cooling, low-temperature high-speed ball screw pairs with strong cooling of ball nuts, and linear guide pairs with ball cages, and other machine tool functional components The market launch also created conditions for the high-speed and precise development of machine tools.
The CNC lathe adopts an electric spindle, which eliminates belts, pulleys and gears, greatly reduces the moment of inertia of the main drive, improves the dynamic response speed and working accuracy of the spindle, and completely solves the problem of belt and pulley transmission when the spindle is running at high speed. Vibration and noise issues. The electric spindle structure can make the spindle speed reach more than 10000r/min.
The linear motor has high driving speed, good acceleration and deceleration characteristics, superior response characteristics and following accuracy. The linear motor is used as the servo drive, eliminating the intermediate transmission link of the ball screw, eliminating the transmission gap (including backlash), the movement inertia is small, the system rigidity is good, and it can be accurately positioned at high speed, thus greatly improving Servo accuracy.
The linear rolling guide pair has zero clearance and very small rolling friction, low wear, negligible heat generation, very good thermal stability, and improves the positioning accuracy and repeat positioning accuracy throughout the entire process. Through the application of linear motor and linear rolling guide pair, the rapid movement speed of the machine tool can be increased from 10-20m/mim to 60-80m/min, up to 120m/min.
The reliability of CNC machine tools is a key indicator of the product quality of CNC machine tools. Whether the CNC machine tool can play its high performance, high precision and high efficiency, and obtain good benefits, the key depends on its reliability.
CNC lathe design CAD, structural design modularization
With the popularization of computer applications and the development of software technology, CAD technology has been extensively developed. CAD can not only replace the manual completion of tedious drawing work, but more importantly, it can carry out design plan selection and analysis, calculation, prediction and optimization of the static and dynamic characteristics of the large whole machine, and can carry out dynamic simulation and simulation of the working parts of the whole machine. . On the basis of modularization, the three-dimensional geometric model and lifelike colors of the product can be seen in the design stage. The use of CAD can also greatly improve work efficiency and increase the first-time success rate of design, thereby shortening the trial production cycle, reducing design costs, and improving market competitiveness.