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CNC machining accuracy of the abnormal fault diagnosis and treatmentProduction often encounter unusual precision CNC machining of the fault. Such failure concealed strong, and the diagnosis more difficult. Such a failure of the main reasons there are five areas: (1) machine tool unit to be altered or changed. (2)-axis machine tools all the 0.1 bias NULL OFFSET anomaly. (3) axial reverse the gap BACK LASH anomaly. (4) abnormal motor running, electrical and control of the anomaly. (5) mechanical failure, such as the screw, bearings, shaft and other components for the. In addition the establishment of procedures for processing, tool selection and human factors, may also lead to abnormal processing accuracy1. System parameters change or alterationSystem parameters including machine feeding units, 0.1 bias, such as reverse gap. For example, SIMENS, FANUC system, feeding its metric and English units of two. Machine repair in certain treatment, often affecting 0.1 gap and offset the change, fault should be disposed of after timely adjustments and amendments on the other hand, due to mechanical wear or link may also be caused by loose parameters measured the changes , The parameters need to be revised accordingly to meet the requirements of precision machining.2. Mechanical failure caused by abnormal processing precisionTHM6350 a vertical machining centers, used SIMENS 840D system. Die-processing in the process, suddenly found Z-axis feed anomaly, at least one millimeter of error of cutting (Z to the cut-off). In that survey: the fault is all of a sudden. Machine tools to move in, MDI (manual data input method) mode of operation under normal operation of the shaft, and the reference point back to normal without any warning tips, electrical control of the hard rule out the possibility of failure. Analysis, the main one by one the following aspects should be checked1 check accuracy of abnormal machine is running at the processing procedures, the length of particular tool compensation, processing coordinates (G54-G59) the proof-reading and computing. 2 to move in the way, the Z-axis movement repeatedly, through visual, touch, listen to their campaign of state, found that the noise Z to the abnormal movement, in particular to move fast, noise more pronounced. This judgement, machinery possible hidden dangers3 Z-axis precision machine tool inspection. Using hand-cranked generator mobile Z-axis, (its rate set at the Shift 1 X100, which is in step, the electrical feed 0.1 mm), with Bai Fenbiao observe the movement of Z-axis. In a one-way movement to maintain normal accuracy of the positive movement as a starting point, every change in pulse-step machine Z-axis movement of the actual distance d = dl = d2 = d3 .= 0.1 mm, that motor running well and also positioning accuracy Good. Back to the actual movement and displacement of the machine changes, can be divided into four stages: machine movement distance d1 d = 0.1mm (slope greater than 1); show for d1 = 0.1 d2 d3 (slope less than 1); machine actually did not move bodies, showing the most standard reverse gap ; movement from the machine and pulse for a given numerical equivalent (slope equal to 1), return to the normal movement of the machineNo matter how the reverse gap (parameters 1851) compensation to their performance characteristics: In addition to stage to compensation, all of the other changes still exist, especially stage seriously affect the accuracy of the processing machine. Compensation found that the greater the compensation gap, stage of moving from the greaterAnalysis of the inspection that there may be a few reasons: First, motor abnormalities and the other is in a mechanical fault; three screw there is space. In order to further diagnose problems, and the screw will be fully undocked from the electrical, mechanical and electrical were part of the inspection. Inspection results of the electrical operating normally in the diagnosis of the mechanical parts that move hand-screw, to return to the initial campaign have a very clear sense of vacancy.And under normal circumstances, should be able to feel bearing orderly and smooth movement. After the demolition inspection found that it really damaged bearings, and the ball is falling. After the replacement machine back to normal3. Machine did not optimize the electrical parameters of abnormal motor runningBeijing has a capacity of vertical milling machine, equipped with SIMENS840D system. In the process, we found abnormal X-axis precision. X-axis inspection found that there are certain gaps, and the motor of instability at the start of the phenomenon. A hand touching the X-axis motor, sensory motor jitter relatively powerful, and stop dithering is not obvious, especially under way to move more obvious. Analysis of that failure for two reasons, First, screw reverse big gap and the other is abnormal X-axis electrical work. SIMENS system using the parameters of function, the motor debugging. First on the compensation gap, adjusting the servo gain parameters and pulse suppression parameters, X-axis motor to eliminate the jitter, precision machining back to normal4. Central location of machine control logic is nothing wrong or unusualTH61140 a processing center, the system is FANUC18I, closed-loop control the whole way. In the process, found that the Y-axis precision machine tools abnormal, the smallest error for the accuracy of 0.006 mm, the largest to 1.4 mm. During the inspection, and machine tools have been set up G54 in accordance with the requirements of the workpiece coordinates. In MDI (manual data input method) mode, the G54 to coordinate procedures for running a section that is G00G90G54Y80F100; M30;, machine tool operation to be displayed on the monitor after the end of the mechanical coordinates for the -1046.605, a record of the numerical.Then in the manual mode, the machine will be to move to any other location, again running under way in the last MDI procedures, the question following the cessation of machine tools, machine tools found at this time numerical mechanical coordinates displayed as -1046.992, with the first After the implementation of the numerical difference compared to the 0.387 mm. In accordance with the same methods, will move the Y-axis to a different location and repeatedly monitor the implementation of the program displayed on the numerical uncertain. Bai Fenbiao with the Y-axis to double-check and found that mechanical error with the actual location of the show was basically the same error, the reasons for that failure to repeat Y-axis positioning error too large.Y-axis on the reverse gap and positioning accuracy check and re-do of compensation, no effects. Therefore suspected grating device and system parameters such as a problem. But why have such a large error, the alarm has not been a corresponding information? Further inspection found that the vertical axis of the shaft, when the Y-axis release me down when the spindle out, causing the error.The PLC logic of the machine tool control program made changes, that is, in the Y-axis release, the first Y-axis can be loaded, then release the Y axis and in clamping, the first axle clamp, then Y-axis can be removed. After adjusting machine fault is resolved.
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