Generally speaking, the ratio of depth to diameter of deep hole is more than 100 in most cases. Such as cylinder hole, axial oil hole of axle, rocket body and barrel of various artillery, etc. Some of these holes require high machining accuracy and surface quality, and some of the machined materials have poor machinability, which often becomes a major problem in production. Therefore, deep hole processing has attracted many people's attention, and more and more people are entering the deep hole processing industry.
Reasons and treatment methods of limit alarm in deep hole processing of CNC machine tools:
1. Damage of relevant control circuit breaking or limit switch
This causes relatively high incidence of "limit alarm". Because the external components are greatly affected by the environment, such as mechanical collision, dust deposition, corrosion, friction and other factors, it is easy to cause damage to the relevant limit switch itself and break the control circuit, while generating "limit alarm" information. It also meets the situation that the overrun switch can not be reset after being pressed. The treatment of this kind of fault is relatively direct, and the damaged switch or wire can be repaired or replaced. Careful alignment and observation are required when conductors are broken or in poor contact.
2. Non-standard operation, misoperation or out of control of machine tools
Among them, mainly to cause hard limit alarm, generally speaking, through direct remedial measures can be restored, using the machine tool itself to remove the function or short connection is the usual method of daily maintenance. In order to gain precious production time, we should firmly grasp the individual characteristics of equipment and system in the process of processing, find a reliable shortcut, and solve the problem flexibly and quickly.
1. Processing according to the structural characteristics of machine tools
Most machine tools are equipped with "over-range relief" contacts. Once a "hard limit" alarm occurs, after confirming that the hard limit switch is pressed, the contact closes and moves out of the limit position manually, that is, relieving the alarm; a few have not set the button, and should be taken at the corresponding point at this time. Effective short connection measures, that is, to force the conditions to be met, and then move the machine out of the limit position.
2. Grasp the Functional Limitation and Characteristics of CNC System
In daily maintenance, we also encounter special situations due to the limitation of CNC system design software. The deep hole processing manufacturer points out that the individual characteristics and performance of a CNC system must be comprehensively mastered in dealing with such problems. While exploring and summarizing, we should keep a good record and receive some necessary technical training when conditions permit.
(1) Due to improper operation, the lower left corner of the machine tool panel shows "hard limit" in Y direction. The Y stroke switch has been pressed, and the hard limit red indicator light is on. In manual mode, the limit position cannot be moved out in the opposite direction.
Processing methods and reasons: The usual removal and short connection methods can not eliminate the failure, because the alarm has not been cleared, the Y-axis movement operation has been invalid in manual or handwheel mode. In the absence of other possible causes, the problem of CNC system is suspected. However, at this time, the CNC system does not have any signs of crash or disorder, and other axes can move normally. We decided to shorten the Y-stroke limit switch, turn off the power supply of the machine tool and wait for a moment, then restart the machine tool, find that the alarm information disappears, the red indicator lights go out, and then move the machine tool out of the limit position, finally cancel the short connection, and everything returns to normal. In fact, after dealing with the situation when the fault occurs many times, we know that The reason for this failure is that the NC system has the function of keeping memory of the last coordinate position when it is electrified.
(2) The alarm information in the lower left corner of CRT of machine tool operation panel is displayed as "hard limit". The red indicator of hard limit is not on, and the actual position of deep hole drilling machine is far from the hard limit switch. At the same time, the numerical value of machine tool coordinates is close to the maximum value of 999999, and the axis can not be moved.
Processing method: In view of the above phenomena, it is first judged that the coordinate value has been overflowed, which exceeds the limit value of machine tool memory. In the case of increasing accumulation, all coordinate data must be cleared and processed. The steps of clearing mechanical coordinates of the system are as follows: 1) enter the "monitoring menu" under the main page; 2) the content of the page is not displayed in any kind of content, so it does not need to be ignored (hidden) and enter the second "slave monitoring"; 3) press the third "F3" next, at this time, it can be seen that the coordinates of each axis machine tool are zero, and the alarm has been cleared. Special attention should be paid to the fact that the machine tool must go back to the reference point to establish the coordinate system of the machine tool, which is due to the limitation of the functional program of the CNC system. The characteristics of point (1) above should be combined in processing.
3. Failure of the process of returning to the reference point leads to limitation
The more advanced CNC systems can usually use the convenient and flexible parameter correction function to maintain the machine tool. If the actual position of the machine tool does not exceed the limit position and there is a limit alarm, first of all, we should carefully check whether the parameters of the trip may be lost or changed. For parameters, the most typical example is that some machine tools are prone to soft limit alarm when they return to the reference point, while the actual position of the machine tool is a certain distance from the reference point. At this time, when the hard limit function of the machine tool is in good condition, the soft limit parameter value should be modified to a large extent according to the displacement of the stop point from the datum mark when the machine tool alarms (sometimes it needs to be set to the maximum or cancelled, depending on the situation), and the soft limit setting should be restored after the machine tool returns to the normal reference point. In addition, after the replacement of some equipment involved in the journey (such as motor, shaft connection, lead screw, etc.), its clearance and displacement are prone to change, there may also be a failure to return to the reference point, and a "limit alarm" will occur at the same time.
IV. Change or Loss of Machine Tool Parameters Due to External Disturbance
In this respect, soft limit parameters are the most common ones. External factors such as poor quality of workshop power supply, bad processing environment, lightning and inadequate shielding measures are very easy to cause the change or loss of various parameters of CNC machine tools. While restoring the parameters, we must find out the direct cause of the failure and take remedial measures.
5. The influence of coordinate system and numerical control program
Processing procedures must be formulated in strict consideration of the deep hole processing range of the machine tool. In the process of processing, once the tool enters the prohibited area, there will be travel limit alarm (soft travel and hard travel). One case is that the program coordinate value is increased due to improper operation (the filter check of the program does not exist through strict simulation of software), and the other is that the parameters of the machine tool processing coordinate system (G54 ~ G59) are set improperly, when walking in relative coordinates, they exceed the range of travel.