10 operations to avoid safety risks in the CNC Machining processing|easoar-soon.com
By jett NG | 16 August 2021 | 0 Comments

10 operations to avoid safety risks in the CNC Machining processing|easoar-soon.com

10 operations to avoid safety risks in the CNC Machining processing|easoar-soon.com

CNC machining center is people's trust in the modern processing equipment, processing of high precision, high efficiency, saving manpower, but to the quality requirement of the operator and programmer is very high, in the operation of the CNC machining center by the height of the programming and operating personnel serious attitude, to many of CNC machining center operation to avoid safe hidden trouble, For our own safety and work safety has a great guarantee.


The following aspects of the introduction, I hope to give you some help, let us healthy and happy work:


1. Programmers and operators should be more careful with the decimal point when writing programs.

FANUC system is the minimum setting unit when the decimal point is omitted, while most domestic systems and some European and American systems, when the decimal point is omitted, it is mm, that is, the calculator input mode. If you are used to the calculator input, you will have problems on the FANUC system. Many programmers and operators may use both systems to prevent problems with the decimal point.


In order to make the decimal point stand out, the isolated decimal point is often written as "0" in the form of programming. Of course, when the system is executed, zeros after the decimal point of the value are ignored.


2. When the operator adjusts the coordinate system of the workpiece, the reference point should be located outside the physical (geometric) length of the cutter, at least on the knife point of the longest cutter.


For the workpiece coordinate system on the workpiece mounting diagram, the operator obtains it on the machine tool by setting the machine tool coordinate system offset. In other words, the operator sets a reference point on the machine tool, and finds the size between this reference point and the zero of the workpiece coordinate system set by the programmer, and sets this size as the offset of the workpiece coordinate system.


On a lathe, the reference point may be set at the center of rotation of the tool rest, at the point of the reference tool, or elsewhere. If no additional motion is attached, the zero of the programmer's instruction, the reference point of the tool rest (machine tool), is moved to the programming position. At this point, if the reference point is located in the tool rest rotation center, the tool rest will collide with the workpiece. To ensure that there is no collision, the reference point on the machine tool should be located not only outside the tool rest, but also outside all tools. In this way, the reference point will not collide with the workpiece even if the tool is mounted on the tool rest.


In a milling machine, the X - and Y-axis reference points are on the spindle axis line. However, the reference point of the Z axis can be set at the principal end or at some point outside the principal end. Want to learn UG programming can add Q group: 45867470 can help you. If at the spindle end, when the instruction is zero, the spindle end will reach the zero position specified in the coordinate system. At this time, the end key of the spindle end will collide with the workpiece: if the spindle is equipped with a tool, it will collide with the workpiece. To ensure no collision, reference points on the Z axis should be located beyond all tool lengths. Even if no additional motion is attached, the reference point will not hit the workpiece.

3. When adjusting the cutter length bias, the operator should ensure that the bias value is negative.


Programmers in the tool length compensation instruction, turning with the T code instruction, and milling with the G43 instruction, that is, the length of the tool offset value added to the instruction value. In the direction of the coordinate axis of the machine tool, the direction of the movement of the tool away from the workpiece is positive, and the direction of the tool moving towards the workpiece is negative. The operator adjusts the cutter offset value to a negative value to instruct the cutter to move to the workpiece. Program instruction tool to the workpiece approach, in addition to the instruction value, but also additional tool bias value, this additional value is moved to the workpiece. At this point, if this value is omitted, the tool will not reach the target point.


3. The workpiece size differs from the actual size by a few millimeters, or there is a great change in an axial direction


Cause of failure: the speed of fast positioning is too fast, the drive and the motor can not respond; After the long-term friction loss of the mechanical drag plate screw and bearing too tight stuck; The tool holder is too loose after changing the tool, and the lock is not tight. Edit the program error, the head, tail no echo or cancel the knife to fill the end; The electronic gear ratio or step Angle of the system is set incorrectly.


Solution: fast positioning speed is too fast, then adjust the GO speed, cutting speed and time to make the drive and motor work normally at the rated operating frequency; In case of machine tool wear and tear, drag plate and screw crane bearing are too tight and stuck, it must be readjusted and repaired.


After the tool rest is too loose, check whether the tool rest reversal time is satisfied, check whether the turbine worm inside the tool rest is worn, whether the clearance is too large, whether the installation is too loose, etc.; If it is caused by the program, the program must be modified, according to the requirements of the workpiece drawings to improve, choose a reasonable processing technology, in accordance with the instructions of the manual to write the correct program;


If the size deviation is too large, check whether the system parameters are set reasonably, especially whether the electronic gear and step Angle parameters are destroyed. This phenomenon can be measured by a dial indicator.


4. The effect of arc processing is not ideal, and the size is not in place


Fault cause: vibration frequency overlap leads to resonance; Processing technology; The parameter setting is unreasonable, and the feed speed is too large, which makes the arc machining out of step. Loosening caused by large clearance of lead screw or loss of step caused by over-tightening of lead screw; Synchronization belt wear.


Solution: find out the resonant parts, change its frequency, to avoid resonance; Considering the processing technology of the workpiece material, reasonable programming; For stepping motor, the processing rate F can not be set too large; Whether the machine tool is firmly installed and placed smoothly, whether the drag plate is too tight after wear, clearance increases or the tool carrier is loose, etc.; Replace the timing belt.


6. There is a change in the processing of one working procedure of the workpiece, and the size of other working procedures is accurate


Cause of failure: whether the parameters of the program are reasonable, whether the program is in the predetermined trajectory, whether the programming format meets the requirements of the manual.


Solution: when the thread program section appears disorderly teeth, screw pitch is not right, then immediately associated with the peripheral configuration of processing thread (encoder) and the objective factors of the function.


8. Each process of the workpiece has the phenomenon of increasing or decreasing


Fault cause: programming error; System parameter setting is unreasonable; Incorrect configuration setting; Mechanical transmission parts have regular periodic change fault.


Solution: check whether the instructions used by the program according to the specification of the requirements of the track execution, can be judged by playing the dial table, the dial table positioned at the beginning of the program after the end of the program whether the drag board back to the starting point position, and then repeat execution even if the observation of the results, grasp the law;


Check whether the system parameters are properly set or are considered modified; The related machine tool configuration in the connection calculation of coupling parameters on the single calculation meets the requirements, pulse equivalent is accurate; Check whether the transmission part of the machine tool is damaged, whether the gear coupling is uniform, check whether the existence of periodic, regular fault phenomenon, if so, check the key part and give elimination.




9. Unstable size changes caused by the system


Cause of failure: unreasonable setting of system parameters; The working voltage is not stable; The system is out of step due to external interference. Capacitance has been added, but the impedance between the system and the driver does not match, resulting in loss of useful signal; The signal transmission between the system and the driver is not normal; System failure or internal failure.


Solution: whether the speed, acceleration time is too large, spindle speed, cutting speed is reasonable, whether the operator's parameter modification leads to system performance change; Install voltage stabilizing equipment; The grounding wire and make sure that it has been reliably connected, and add anti-interference absorption capacitor at the driver pulse output contact;


Select the appropriate capacitance model; Check whether the signal connection line between the system and the driver is shielded, whether the connection is reliable, check whether the system pulse signal is lost or increased; Send to the factory for repair or replacement of the motherboard.


10. How does the workpiece shift affect the accuracy?


Fault cause: machining the workpiece on the three-axis CNC machining center sometimes appears to be processed workpiece internal structure position movement, dimensional accuracy is poor and other problems, the cause of this kind of problem is often caused by the secondary clamping alignment accuracy is not high.




1) Leverage Percentage Table Method


Leverage dial indicator method is sucked the leverage dial indicator on the main shaft of CNC machining center, let the dial indicator is in close to a horizontal position, but the dial indicator fell to fine datum correction, using a CNC numerical control system of the handwheel moving workbench, turn the shaft by hand at the same time, make the dial indicator to fine datum and present a maximum, which can adjust the workpiece. At the same time, the relative coordinate values of CNC machining center CNC system related directions are cleared to zero.


2) pad method


The pad method requires the use of auxiliary tools such as standard pad to translate the precision datum surface of the work piece. On the knife between instrument and artifacts in the standard block, in main shaft of CNC machining center with the photoelectric edge finder, low-speed rotation axis, photoelectric edge finder directly touch the left and right side of the pad, time difference is the error value, can be adjusted according to the difference between workpiece, however, due to the gap between block and workpiece, this method is better than using leverage dial indicator of high precision.


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