The consequences of machine collision accident in CNC machining are very serious. Once the tool or tool holder collides with the workpiece or machine tool, the light one will cause damage to the tool and scrap the machined parts, and the heavy one will damage the parts of the machine tool, resulting in inaccurate accuracy and even failure to work normally. What's more, the collision may cause personal injury accidents. Therefore, in the process of NC machining, machine collision is absolutely a kind of machining accident to avoid. This requires the operator to develop a careful working habit, operate the machine tool in the correct way, and reduce the occurrence of tool collision.
There are many different reasons that may cause a crash. Let's make a summary below. Only by understanding the reasons that may cause a crash, can we carry out targeted prevention. The reasons for the collision mainly include the following nine points:
Programming error
First of all, there are errors in the preparation of the processing program, specifically including errors in process arrangement, inadequate consideration of the process undertaking relationship, and errors in the setting of processing parameters. For example, the top of the actual workpiece is coordinate 0 point, but its bottom is set as coordinate 0 point in machining; The set safety height is not enough, so that the tool does not completely leave the workpiece when it is lifted; The allowance setting of secondary roughening is less than that of the previous knife, which may cause a collision accident. Therefore, after the program is written, the path of the program must be analyzed and checked. Only when there is no problem can it be started and run.
Program sheet remarks error
If there are no comments, incorrect comments or incomplete comments on some similarities that need to be noted in the procedure, it may cause a collision. For example, the one-sided collision number is written as the four sided median; Mark the clamping distance of the vise or the protruding distance of the workpiece incorrectly; Unclear or incorrect remarks on the extension length of the tool will lead to machine collision. In order to avoid the occurrence of the above situations, the program sheet should be noted in detail as much as possible, and the principle of replacing the old with the new should be adopted during the design change, and the old program sheet should be destroyed and no longer used.
Tool measurement error
If the size measurement of the tool is wrong, for example, the length of the tool bar is not taken into account when inputting the tool data; Too short tool loading and relatively long extension of the tool will also cause the tool to collide with other equipment or workpieces. Therefore, accurate instruments should be used to measure the tool, and scientific methods should be adopted. The length of the tool should be 2 to 5 mm longer than the actual depth.
Program transfer error
If the program number call is wrong or the program is modified, but the modified program is not called, but the old program is still used for processing, it will cause a collision due to the program transmission error. In order to avoid these situations, the detailed data of the program must be checked before processing, including the time and date of program writing, and the simulation must be carried out first. The simulation can be officially run only when there is no accident.
Knife selection error
Improper tool size selection or inconsistent with the tool with parameters set in the program will also cause machine collision.
Blank exceeds expectation
The blank size exceeds the size set by the program, which hinders the operation of equipment and tools, and it is easy to cause machine collision accidents.
Problem of workpiece material itself
For example, the workpiece itself has defects, or the hardness of the workpiece is too high, which is also a major reason for the collision.
Clamping factors
Cushion blocks are often used in clamping, because the use of cushion blocks will lead to changes in the actual position and size of the workpiece. If the influence of the cushion block is not taken into account when programming, there may be a machine collision phenomenon.
Machine failure
Sudden power failure, lightning and other accidents will also cause a crash. With the continuous humanization of machine tool functions, anti-collision machine detection technology began to appear and put into use, which played a certain guarantee for preventing collision.