Due to the wide variety of CNC systems of machine tools, different forms and equipment structures, various design methods and extremely different defect phenomena, the maintenance of CNC equipment is quite difficult. While mastering the principles of mechanical structure and electrical control, you must analyze reasonably, apply in a flexible way and be good to summarize, so that you can achieve the result with half of the effort twice. Based on the principle, we will restrict the scope of the easy to difficult flaw and eliminate it. In order to ensure the safety of the functioning of the machine tool, the linear axis of the machine tool is generally equipped with two protective “defense lines”: setting limit of the parameter) and hard limit (line switching limit ). The limiting problem is one of the current defects in CNC machine tools, and there is little related information mentioned. Here are some analyzes and explanations of the main reasons for “Limit Alarm”.
1. The relevant control circuit is broken or the limit switch is damaged
This reason causes a relatively high impact of “limit alarm”. and control circuits. He also met the situation where the switch within range cannot be reset after being in a hurry. This type of defect is more direct and damaged switches and wires can be repaired or replaced. When the wire is broken or the contact is poor, the wires must be carefully settled and observed.
2. Operation, dysfunction or essential machine-tool
Among them, the main objective is to cause hard limit alarms. interview. In order to save precious production time, we must firmly grasp the individual characteristics of equipment and system during the processing process, find reliable shortcuts and solve problems in a flexible and rapid manner.
1. Process according to the characteristics of the structure of the machine tool
Most machine tools are equipped with “overtaking release” contacts. The position of the position means that the alarm is canceled; And the tool-tool is moved from the limit position.
2. Enter the limitations and functional characteristics of the CNC system
In daily maintenance, we also meet special situations due to the limits of the CNC system design software. To deal with such problems, we must fully grasp the individual characteristics and the performance of a CNC system. By exploring and summarizing, we must keep registers and receive necessary technical training if possible.
(1) Due to an inappropriate operation, the lower left corner of the machine-tool panel is displayed in the form of a “hard limit”. In manual mode, the limit position cannot be moved in the opposite direction.
Method and reason for treatment: The defect cannot be eliminated using the usual withdrawal and short-circuit methods. Without finding other possible causes, a problem with the CNC system has been suspected. Decided to short-circuit the limit switch of the race y, turn off the supply of the tooltip and wait for a certain time, then restart the tooltip, note that the alarm information disappears, the red light S ‘Extinct, then move the tooltip from the limit position, and finally cancel the short circuit, everything comes back to normal, in fact, after the processing of faults several times, we realize that this defect is due to the fact that the CNC system has the function of maintaining memory when the previous coordinates The position is on.
(2) Alarm information in the lower left corner of the operating panel of the tool-machine is displayed as “hard limit”. Hard limit switch. At the same time, the digital display value of the coordinates of the machine tool is close to the maximum value of 99999999, and this axial direction cannot be moved.
Treatment method: Given the above phenomenon, it is first determined that the coordinate value has overflowed, exceeding the limit value of the machine’s memory. The steps to erase the mechanical coordinates of the system are as follows: ① Enter the “Search” menu under the main page; Element “Surveillance of slaves”; ③ Then press the third “F3” element, and we can see that the coordinates of each axis are zero and the alarm has been erased. Pay particular attention to the tool-tool must return to the reference point to establish the coordinates system of the tool-tool. During treatment, the characteristics of the point (1) above must be combined.
3. The return process to the point of reference has failed, causing the limit
More advanced CNC systems can generally use practical and flexible parameters correction to maintain the machine tool. can be lost or modified. Regarding parameters, the most typical example is that some machine tools are subject to flexible limit alarms when returning to the point of reference, and the real position of the machine tool is a certain distance from the point reference. Currently, when the hard limit function of the machine is intact, the value of the limit limit parameter maximum or canceled, and it must be considered as) once the monitoring tool normally returns to the point Reference, the soft limit parameter must be restored. In addition, after having replaced certain equipment involving a race (such as engines, tree couplings, lead screws, etc.), gaps and trips are likely to change, and there can be non-non-non Back to the point of reference and an “limit” an alarm “can occur.
4. The parameters of the machine tool are modified or lost due to an external interference.
In this regard, the soft limit parameters are mainly common. External factors such as poor quality of energy in the workshop, poor treatment environment, lightning and inadequate shielding measures are likely to cause changes or loss of various parameters of CNC machine tools. When restoring the parameters, it is necessary to discover the direct cause of failure and take repair measures.
V. The influence of the coordinate system and the CNC program
The machining program must strictly consider the machining range of the machine tool. One situation is that the value of the program’s coordinates is increased due to inappropriate operation (the program filtering method does not exist thanks to a strict simulation of the software). And the relative contact details are moved.
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