CNC Grinding Machine
January 25, 2017 CNC Machine
CNC grinding machine is the use of abrasive on the workpiece surface grinding machine. The majority of grinders are ground using high-speed rotating grinding wheels, with a few using other abrasives and free abrasives such as whetstone, abrasive belt, and other abrasives, such as honing machines, super finishing machines, abrasive grinding machines, Machine and so on. CNC grinder and CNC surface grinder, CNC centerless grinder, CNC internal and external grinder, CNC vertical universal grinder, CNC coordinate grinder, CNC forming grinder, etc.
Table of content
CNC machine tools is the combination of information technology and machinery manufacturing technology products, representing the modern foundation of the technical level of machinery and development trends. Six mainframe: CNC lathes, machining centers, CNC grinding machines, CNC forging machine tools, CNC heavy-duty machine tools and precision CNC machine tools.
2. Processing range
Grinding machine can process high hardness materials, such as hardened steel, carbide, etc .; also can process brittle materials, such as glass, granite. Grinding machine for high precision and surface roughness of a small grinding, but also for high-efficiency grinding, such as strong grinding.
In the 1830s, grinders using natural abrasives were developed in the UK, Germany and the United States, respectively, in order to cope with the hardening of parts such as watches, bicycles, sewing machines and firearms. These grinders are at the time off-the-shelf machine tools such as lathes, planer and above the installation of grinding head from the restructuring, and their simple structure, low stiffness, grinding vibration is easy to require workers to have a high skill to grind precision Of the workpiece.
1876 at the Paris Expo on display at the American Brown – Sharp’s universal cylindrical grinder, is the first time the basic characteristics of the modern grinding machine. Its workpiece headstock and tailstock are mounted on a reciprocating table, which increases machine rigidity and comes with an internal grinding attachment. In 1883, the company made the grinding head mounted on the column, the table for reciprocating surface grinder.
1900 years ago, the development of artificial abrasives and hydraulic drive applications, the development of the grinding machine has a great role in promoting. With the development of modern industry, especially the automotive industry, a variety of different types of grinding machines have come out. For example, the early 20th century, has developed the processing of the cylinder block planetary internal grinder, crankshaft grinder, camshaft grinder and the magnetic piston with a suction cup grinding machine.
Automatic measuring devices began in 1908 applied to the grinding machine. By the 1920s, grinders, double-face grinders, roll grinders, guide grinders, honing machines and superfinishing machines were used in succession; in the 1950s, high-precision cylindrical grinders were available for mirror grinding; The end of the wheel speed has reached 60 ~ 80 m / s high-speed grinder and large depth of cut, slow feed grinding surface grinder; 70’s, the use of microprocessor digital control and adaptive control technology in the grinding machine has been widely Applications.
1, suitable for the processing of complex shaped parts.
2, to achieve computer control, excluding human error.
3, through the computer software can achieve precision compensation and optimal control.
4, machining centers, turning centers, grinding centers, electric machining center with a tool magazine and tool change function, reducing the number of clamping, improve the machining accuracy.
5, CNC machine tools to increase the flexibility of mechanical processing equipment. Flexible processing is not only suitable for many varieties, small and medium batch production is also suitable for mass production, and can alternately complete two or more different parts of the processing, an increase of automatic transformation of the workpiece function, enabling unattended operation at night. Flexible manufacturing systems (FMS) consisting of several CNC machines (machining centers) have a higher degree of flexibility in the automated manufacturing system, including processing, assembly and inspection and other links.
5.1 Spindle components
Grinding wheel speed is generally 30 ~ 60m / s, CBN wheel can be as high as 150 ~ 200m / s, the maximum spindle speed of 15000r / min. Spindle unit is the hub of the grinding machine parts, for high-speed high-precision unit system should have good rigidity, high precision, small temperature rise, chaos good, low power consumption, long life, moderate cost characteristics. Grinding wheel spindle unit bearings often use high-precision moving bearings, hydrostatic bearings, liquid dynamic pressure bearing, the message pressure bearing. More and more high-speed and ultra-high-speed grinding spindle unit components.
5.2 Feed Unit
The feed unit includes a servo drive unit, a moveable member, a position monitoring unit, and the like. Feeding unit is necessary to maintain the normal work of the wheel, grinder is to evaluate the performance of one of the important indicators. Requires flexible feed unit operation, high resolution, high positioning accuracy, fast dynamic response, it is necessary to have greater acceleration, but also have enough large driving force. Feeding unit commonly used program AC, DC servo motor with a combination of feed screw or linear servo motor directly drive the program. The transmission chain of the two schemes is very short, mainly to reduce the mechanical transmission error. Two programs are dependent on the motor to speed, commutation.
Grinding wheel frame, head frame, tail frame, table, bed, column, etc. is the basic components of CNC grinding machine, its design and manufacturing technology is to ensure the quality of the fundamental grinding machine.
5.4 Auxiliary Units
The auxiliary unit includes a workpiece fast clamping device, an efficient grinding fluid supply system, a safety guard, a spindle and grinding wheel dynamic balancing system, and a chip processing system.
6. Classification of varieties
6.1 high-end CNC machine tools
Is the processing of complex shapes of multi-axis control or process concentration, high degree of automation, highly flexible CNC grinding machine.
6.2 universal CNC machine tools
With man-machine dialogue function, wider application, affordable, usually referred to as full-featured CNC machine tools.
6.3 Economical CNC machine tools
Simple structure, medium accuracy, but the price is cheap, can only meet the general precision requirements of the processing, can shape a straight line, diagonal, arc and threaded parts.
7. Selection principles
1, practicality: refers to a clear CNC machine tools to solve which one or several production problems.
2, economy: refers to the choice of CNC machine tools to meet the processing requirements of the conditions, the price paid is the most economical or more reasonable.
3, operability: the user selects the CNC machine tools to the operation and maintenance of the enterprise level of adaptation.
4, stability and reliability: refers to the quality of the machine itself, select brand-name products to ensure stable and reliable work of CNC machine tools.
8. Common faults
As the advanced nature of CNC machine tools and fault instability, and most of the failures are in the form of integrated failure, so making the maintenance of CNC machine tools increased the difficulty of many, but the steps and methods of fault handling nothing more than the following points .
1, the full investigation of the fault site
When the failure occurs, we must first fully understand the machine failure is under what circumstances, what happens when the phenomenon occurs after the operator to take what kind of measures, such as the fault site is still, it is necessary for the contents of the CNC Carefully observe the contents of the implementation of the block and the self-diagnostic display of the alarm content, and observe the circuit board alarm light situation. And then press the system reset button to see whether the fault disappears, such as fault alarm disappears, then most of these alarms are software failures.
2, the possible causes of failure of all factors listed
NC machine tools appear the same kind of failure may be a variety of reasons, there are mechanical, electrical, control system and many other factors, so the failure analysis should be listed all the relevant factors. For example: X-axis machine will appear when moving jitter, resulting in this phenomenon may be: a, X-axis encoder connection may have poor contact; b, X-axis island rails too tight, too much damping, X-axis motor load is too large; c, X-axis servo motor and screw coupling loosening or clearance; d, X-axis servo motor drive problems; e, X-axis servo motor failure and so on.
3, to determine the causes of failure methods
Numerical control machine tool numerical control system variety but no matter what kind of numerical control system, when the breakdown may use the following several methods to carry on the comprehensive judgment to the breakdown.
(1) Intuitive method: is the use of human sensory attention to the phenomenon of failure and determine the possible location of the fault. If there is any abnormal sound when the fault occurs, the spark occurs, where there Jiaochu bit, where there is a fever anomaly, and then further observation of possible failure of each circuit board surface conditions, such as whether the circuit board Charred, smoked or electronic components at the Department have a burst, in order to further narrow the scope of inspection. This is one of the most basic, the most simple method, but requires machine maintenance personnel have a certain maintenance experience.
(2) the use of CNC system hardware alarm function: alarm indicator can determine the fault. In the numerical control system hardware circuit board has a lot of alarm indicator, which can be roughly determine the location of the fault.
(3) make full use of CNC system software alarm function: CNC system has a self-diagnostic function. During system operation, the system can be diagnosed quickly by self-diagnostic program. Once the fault is detected, the fault will be displayed in the form of the alarm screen, or light up the alarm lights, maintenance, according to the alarm content to find the machine where the fault lies.
(4) the use of state display of the diagnostic functions: CNC system not only can fault diagnosis information displayed, but also in the form of diagnostic addresses and diagnostic data to provide machine diagnosis of various states, for example, provides the interface between the system and the machine tool Input / output signal status, or the status of the input / output signals between the PC and the CNC device, and between the PC and the machine, the status display of the display screen can be used to check whether the CNC inputs the signal to the machine, or The switching information of the machine has been entered into the CNC. In short, you can distinguish the fault is on the side of the machine or CNC system side, which can reduce the scope of inspection of CNC machine tools failure.
(5) should check the failure of CNC system parameters: system parameter changes will directly affect the performance of machine tools, and even make the machine failure, the whole machine can not work. While the outside world interference may lead to changes in the individual parameters of the memory, listen to when the machine occurred some strange failure, the parameters of the NC system can be checked.
(6) Replacement of spare parts: When the failure of the machine analysis found that the circuit board may even be faulty, you can use the replacement parts board, you can quickly determine the fault circuit board. However, when using this method need to note the following two points:
① attention should be paid to the position of the circuit board on the switch, the board should be changed in exchange for the two boards to set the state to be completely consistent, otherwise the system will be unstable or not the best state, or even appear Call the police.
② After replacing some circuit boards (such as the CCU board), you need to reset or enter the parameters and programs of the machine.
(7) the use of circuit board detection terminals: on the circuit board for the measurement circuit voltage and waveform detection terminals in order to debug and repair the part of the circuit to determine whether the normal work. But in the detection of the part of the circuit should be familiar with the circuit principle and the logic of the circuit. Logical relationship in the unfamiliar case, the two can be used as the same circuit board testing, which found that the failure of the circuit board.
When the CNC machine tools in the event of failure, maintenance personnel follow the above steps and methods of detection will be able to correctly determine the cause of the fault and fault location.
9. Related issues
9.1 Background Editing
In the FANUC series oi Mate TB system, the manufacturer in order to make the operator easy processing, set the background editing function, that is, in the automatic processing process, the process can not terminate the process of editing the program to modify the current program Or perform background editing on other programs. You can also change the position of the machining point by moving the tool by shaking the handwheel until the “Handwheel mode” is selected. Background editing function to facilitate the operator in the machining process of the parts to be modified, simplifying the operation process. But this simplification, but to the safe operation of a serious risk, in the teaching practice, prone to misuse of students. When the control mode is selected to “Auto Cycle” mode, if the machine chuck is not clamped or the tailstock is not ejected (ie, the machine is not ready), the “Cycle start” key is pressed and the machine does not operate. In this case, the control mode is selected to “Manual Operation”, so that the machine chuck is clamped and the tailstock is ejected (ie the machine is ready). The “Cycle Start” command is selected and the program is executed automatically. If the operator is feeding at this time, the hand has not left the workpiece, the program has spindle start command, the operator vulnerable to hand injury, or even a serious security incident.
The solution is as follows:
1) The manufacturer adjusts the system ladder to change the start condition of the “Cycle start” key, that is, when “chuck clamping” and “tailstock tightening” are prepared, MDI “mode,” loop start “button to work, the lack of any of them are invalid.
2) “or” relationship into chuck clamping → tailstock tight → automatic mode → cycle start “side by side” relationship. However, this change will make the “background editing function” to no avail, for the operator need to change the program while processing side will be difficult, but pay more attention to safety in mechanical engineering training teaching, this change is necessary.
3) Cancel the existing command. Press the “reset” button to cancel the existing command, even if the “chuck clamping”, “tailstock tight”, “automatic mode” program does not automatically “automatic mode” press the “cycle start” key is invalid, , You need to re-operate the “Cycle Start” key. This method will eliminate the danger in the bud, it is worth promoting in the application.
9.2 Machine power supply
NC machine tool with NC system (digital control system), NC data required to save the machine when the shutdown, so the NC system has its own backup power-down protection. When the NC power supply is not enough, the need to replace the battery in time to ensure that data is not lost.
However, because the NC system has a memory function, if the operator is operating the machine for processing, other staff will be the total power off the machine, the machine pallet may not be controlled to move forward, crashed machine tools, accidents. At the same time, because the NC power instantaneous current is too large, easy to burn the machine. Therefore, CNC machine tools should have their order: the first external power supply to open the boot, and then open the total power supply machine, and finally open NC power. Power off the first NC power, and then turn off the machine’s total power, to determine the absence of other machine tools to use the case of external power off, and the boot sequence is just the opposite.
9.3 Option OK
Siemens system in the control panel operation from time to time to determine the options. When the tool operation is performed, the new data is displayed on the display after the X-axis or Z-axis tool alignment has been completed. However, if you do not press the “confirm” button, the system still does not pre-knife data for the required tool offset value, does not recognize the new value of the cutter compensation, this time as a tool for this tooling prone to playing knife event.
9.4 Data Display
If you select “Handwheel mode” in “JOG” mode, the system will ask for confirmation of X-axis or Z-axis. If you do not confirm, the tool holder will move in the previous direction, which will cause the wrong movement of knife rest. Knife situation.
9.5 Zero Offset
In the modern numerical control system operation, people often use G54 ~ G59 tape machine in a zero offset instruction to set the workpiece zero in the machine coordinate system position (workpiece zero to machine zero as the base offset). In this way, it is important to note whether the tool compensation is used or not. The setting of the tool compensation value is based on which point is set as the reference point. If the offset from the workpiece origin is the tool offset value, the coordinate system positioning error will occur if the zero offset command is used again, which will bring danger to the operation. So once the use of G54 and other zero-offset instructions should be noted that after the operation should be used in time to cancel the instruction can be set zero offset.
In the same way, in the FANUC system, there are “double-shift ball”, the so-called “work shift” refers to the program, tool offset, the workpiece coordinate system and other values unchanged, the imaginary workpiece to translate, that is equivalent to the workpiece coordinate system in the opposite direction mobile. This method can be used without moving the rough, do not rebuild the coordinate system for the case of multiple pieces of processing. The use of “work shift” should be noted that after the cancellation of its value, or other operators without the knowledge of the operation of the machine prone to the workpiece coordinate system error positioning, prone to hit the knife phenomenon, resulting in security incidents.
9.6 Wear correction
Tool wear correction is a good knife, the establishment of a good tool value, the tool wear through the use of this small amount of wear and tear through the knife on the tool wear correction. It is recommended that the tool nose wear value be placed in the wear correction, but the tool length compensation value should be placed at the tool length compensation. Because the tool change command and tool offset are specified in the program, the program executes the tool change command and then the tool length compensation. The tool wear correction is just the opposite, the program first executes the tool wear correction, after the tool change operation. If the wear correction value is too large, the tool easy to hit the machine table dangerous.
9.7 Z-axis inspection
Most CNC machine tools with a graphical verification function, but mostly two-dimensional graphics verification. In the CNC milling machine, machining centers can only X-axis, Y-axis graphics for verification, Z-axis value can not be graphic inspection. So can not believe that the correct program to correct graphics, Z-axis value also need to test the G00 or G01, G02 and other instructions to check the use, in order to avoid accidents.
9.8 Program Processing
In the Siemens system for part program processing, the need to select the corresponding program name, if the operator only click on the desired program only press the ‘open’ button, the display area of the work area shows the program just opened, But in the upper right corner of the display is still the last cycle of the selected program automatically, at this time if the press “cycle start” command, the processing program is shown in the upper right corner of the program, rather than just open the program you want to process Point with the commonly used Windows operating system used to distinguish), and there mistaken processing, and even cause security incidents.
The correct operation is the operator clicks on the program to be processed, you must press the “Select” button to confirm select the program.
10. Operational procedures
1, the operator obtained the operational license by the examination, the prospective operation, the operator should be familiar with the performance of the machine, structure, etc., and to comply with safety and shift regime.
2, the operator must be based on the requirements of a powerful grinding machine manual, a detailed understanding and memorize the lubrication parts, lubrication methods and types of lubricants, brands, according to the provisions of the grinding table lubrication, oil maintenance.
3, before the start, should be required to wear good protective equipment, the control shift record book, the various parts of the grinding machine detailed examination and found that problems should be reported in a timely manner step by step, exclusion may not drive car work.
4, before starting to deal with the following parts of the powerful grinding machine to check:
(1) Whether the oil in the oil sump of the wheel frame reaches the specified oil level.
(2) adjust the belt tightness is appropriate.
(3) shake hand wheel, table, wheel frame reciprocating motion is good.
(4) wheel shield and wheel to install a solid card, the correct position, the work table should be in contact with the dust guide carpet tight.
(5) Check the electrical system (motor, distribution box, safety light, wire, ground wire) is good, the surrounding environment is clean, no short circuit.
(6) Check the lubrication parts, the sliding surface and the transmission system, into the lubricating oil.
(7) turn on the power, turn on the oil pump, wheel frame, bedside frame of the motor, pay attention to running. Found abnormal, abnormal sound, should immediately turn off the power, after inspection and quasi-quasi-drive.
(8) Start the grinding machine, idling 2 ~ 3min, check the ministries action is normal. If the body failure, bearing overheating, oil pressure is not enough, the wheel wobble, table movement is not stable and so is not normal, should stop the power supply, take measures to deal with, prohibit users beyond self-test self-demolition of self-treatment.
(9) Check the cooling pump motor is running normally, whether the cooling fluid.
(10) Installed grinding wheel, grinding wheel and the pressure plate should be pad to 0.5 ~ 1.Omm paper pad, must use a special wrench, uniform force tightening, not allowed to use extended tube fastening, so as to avoid the wheel burst.
(11) wheel loading should be no-load operation 5min, the operator should avoid the front, to confirm the normal operation of the wheel, the prospective use.
5, the workpiece card must meet the requirements. For workpieces that have been interrupted for any reason, it is necessary to confirm that the work is in good condition and that the work is to be started.
6, the workpiece, you must clear the workpiece on the grease, black dirt and dust, etc .; according to the reasonable choice of the workpiece material grinding wheel and grinding volume, is strictly prohibited to grind the workpiece blank.
7, card and measuring the workpiece, the grinding wheel must be removed from the workpiece and parking. Workpieces and grinding wheel not left, not stop halfway. Grinding wheel in close to the workpiece, are not allowed to use the motor to give.
8, at work, to prohibit the operator to leave the grinder or trustee escrow. If power outage or other reasons must be left, the wheel should leave the workpiece after parking. Re-start the grinding machine, you should confirm that the Ministry is no exception after the quasi-driving.
9, the work of the grinding machine should pay attention to the transmission part of the state, such as oil temperature and oil pressure is normal, the coolant is smooth and accurate to the workpiece, the pump and the motor temperature is normal, whether abnormal, different sound, the operating handle Whether or not the position is correct, and whether or not the fastening members are loosely displaced.
10, prohibited in the work surface and the surface of metal objects placed on the paint.
11, prohibiting the table and the bed on the beat, disassembly, straighten the workpiece.
12, grinder after the accident, should keep the scene, cut off the power, rapid report, properly handled.
13, after work, grinding wheel should be withdrawn from the workpiece, cut off the total power, the handle placed in the vacant position, to restore the normal state of the grinder, good routine maintenance.
14, carefully fill in the shift record book and other relevant records.
12.List of CNC grinding machine manufacturers
|ANCA||Australia||CNC grinding machine. CNC system. software and automation accessories.|
|HOLLBRIT INC.||Canada||Automated welding & grinding systems for the sheet metal manufacturing industry.|
|Grand River Tool and Machine Corp.||Canada||precision machining service, surface grinding.|
|Shanghai ZZMINE Machinery Co., Ltd.||China||grinding equipment.|
|ZARO MACCHINE s.r.l.||Italy||CNC grinding machine.|
|MAS s.r.l.||Italy||mechanical grinding solutions.|
|CNC GEAR GRINDING MACHINE HOFLER NOVA 1000||Poland||CNC gear grinding hofler machine nova.|
|GER MÁQUINAS-HERRAMIENTA S.L.||Spain||grinding machine.|
|United Grinding Group AG||Switzerland||grinding systems series machines with extensive accessories for the external and internal cylindrical grinding of small and medium-sized workpieces tooling.|
|Weber Manufacturing Co||US||Centerless grinding, precision grinding.|