Two basic methods of starting and returning to zero for CNC machining centers and solutions to common problems

Author: MULAN -Plastic Molding Manufacturer

For CNC numerical control machine tool equipment, it is an essential part to perform a zero return operation before each start-up operation. The function of this zero return operation is mainly to re-determine the origin and coordinates of the machine tool, and at the same time perform various operations on the machine tool. Item errors are compensated. 1. Two basic methods of machine tool zero return operation. Boot zero return is an operation that our machining personnel often use. However, some people may not know what is boot zero return. Return to the starting position of Z, and then use this coordinate point as a reference point to realize subsequent processing operations and task control. At the same time, it can also provide a reference point to facilitate the adjustment and setting of tool compensation and gap compensation in the second half of machining.

According to the classification of the implementation method and detection device, there are two main methods of zero return: the grid method and the magnetic switch. As the most important two methods of returning to zero on the machining center, their effects and execution methods are completely different. Among them, in the case of magnetic switch zero return, due to the defect of its own positioning drift phenomenon, its zero return accuracy and effect are very poor, so this method is only used in early machining centers. Now High-precision machining centers are basically extinct.

The principle of grid method zero return is to realize the effective zero return of the machine tool through the two components of grating ruler and pulse encoder. This zero return method has high precision and good flexibility, and is the mainstream zero return method of CNC machine tools at present; And this method is divided into two parts: absolute grid method and incremental grid method. The absolute grid method means that after the machine tool completes the zero return operation in the first debugging process, it can always store the zero point position, and there is no need to perform this step after that. In the incremental grid method, the setting of the coordinate axis needs to be completed manually. In addition, the signal control of the machine tool control device must be controlled by pulses, so that the switch position of the zero point can be queried instead, so as to complete the process of returning to zero.

2. Problems and countermeasures that often occur in the machine tool zero return operation. When the machining center is returned to zero, even if the system parameters have not been changed, there will still be zero return failures occasionally. In our use, there are two kinds of failures that often occur. One is that the steps of returning to zero are correct but the zero position is wrong; the other is that the zero return system is normal but the zero position cannot be found. 1. Faults where the steps of returning to zero are correct but the position of the zero point is incorrect. The reasons for this type of fault can be summarized into three aspects: one is that the parameters of the zero offset are improperly considered during design; the other is that when returning to zero The deceleration time is too short and the zero position is far beyond the actual range; the third is that the mechanical structure in the zero return system causes the zero position to deviate.

After knowing these three possible reasons, we can eliminate the possible problems that may cause the machining center to return to zero according to the actual situation. 2. The zero return system is normal but the zero point position cannot be found. There are three main reasons for this type of fault: one is that the internal components of the operation control system are damaged; the other is the signal receiving system and the zero point switch. The circuit is damaged; the third is caused by the damage of the relevant switch at the zero point. After knowing the above possible reasons, we can leave according to the actual situation on site to eliminate the reasons that may cause the machining center to return to zero.