There are two common reasons why the machine tool moves randomly: 1. It is a problem with the metric and imperial systems. When some people enter parameter search, they press the soft key NO.SCR, but the result is INPUT, which causes the parameter No. 0 to be changed to metric and inch, causing the machine tool to move randomly. 2 means the manual absolute ABS switch is turned on. Some are in the machine tool operation panel buttons, and some are in the system's soft operation panel.
1. Advantages and disadvantages of manual absolute value on/off function
The manual absolute value switch is used to select whether to add the movement amount of manual operation (JOG feed and handwheel feed) to the current position of the workpiece coordinate system by turning the manual absolute value button ON or OFF. At the same time, a detection signal is output to indicate whether the manual absolute value in the CNC is ON or OFF.
In actual processing, the manual absolute value on/off function is often used. If used well, it can make the processing operation simpler and more convenient; if used improperly, it often causes some seemingly weird or serious problems that lead to tool collision. Problems similar to the above are often encountered during debugging and maintenance, but the factor of manual absolute value on/off is often easily ignored.
Positive impact: For example: During rough machining, sometimes it is found that the feed amount is too much/less. At this time, you can insert manual operation through this function to subtract/add the manual movement distance to the current position of the workpiece coordinate system, saving the need for re-alignment. Knife handling, etc. The negative effects are more common than the positive effects. Because manual operations are often involved in processing; some machine tool manufacturers do not directly make this function a button on the operation panel, but often use the K address or the switch on the soft operation panel to set the function signal to 0 or 1, so Manual absolute values are often turned off inadvertently, causing problems. This factor is often easily overlooked.
For example: the manual absolute value is turned off accidentally or inadvertently (the operator is not clear and presses the soft operation panel randomly). During the processing, it is necessary to check the processing condition of the workpiece, or the tool is damaged and needs to be replaced. At this time, manual operation is involved. After the operation is completed, "knife collision" accidents often occur; or if the machining continues after resetting, the coordinates will be inexplicably incorrect.
2. Manual absolute value on/off function
NO and OFF of manual absolute value are switched by 0 and 1 of *ABSM (G6#2) signal. At the same time, the signal MABSM (F4#2) can be used to detect the status of the manual absolute value signal.
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Note: *ABSM signal is active low level
1 When manual absolute value is ON When automatic operation is interrupted by manual operation:
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Figure 1 Manual absolute value ON
Before a block is finished, insert manual operation to move a certain distance. Whether it is an absolute value or an incremental command, the tool position of the machine tool in this block will be translated by the amount of manual operation.
The translated tool position in subsequent blocks will remain unchanged until the absolute value command block appears. After translation, if it is always an incremental command, the end point position will be offset by the manual movement amount, and the current position display includes this offset amount.
2 When manual absolute value is OFF, automatic operation is interrupted by manual operation.
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Figure 2 Manual absolute value OFF
During automatic operation, if manual operation is inserted before a program segment is completed or has been completed, then at the end of this program segment and the end point of the subsequent program segment, whether it is an absolute value or an incremental value instruction, The position of the machine tool will be translated by the manual movement amount. After the operation is completed, the displayed value of the current position is the programmed end point value, just as if no manual insertion was performed, but in fact, the tool position has been translated.
3. Summary:
From the above, it can be seen that when the manual absolute value is OFF, the appearance is easily misleading, and problems such as knife collision are very easy to occur. Moreover, when the ladder diagram handles this function, the conditions that trigger the G signal are often hidden and difficult to find. Therefore, it is recommended to consciously consider the factor of manual absolute value when dealing with issues such as tool collision and coordinate changes.
