1、 Cause analysis of workpiece over cutting
1. Deviation or error of workpiece edge seeking
(1) Negligence of site personnel;
(2) The dimensions of the drawing are not clear, and X, y and Z are not marked in the usual way;
(3) The processing origin of program sheet does not coincide with the origin of drawing.
2. Wrong tool use or wrong program list (this error often occurs when the program is copied)
Preventive measures:
(1) Fill in the program sheet while writing the program;
(2) After the program is finished, the tool size must be checked one by one;
(3) Manually add the program number and tool size to the beginning of the program NC code.
3. When rough milling, the allowance is too small or the diameter of tool is not accurate
Preventive measures:
(1) The programmer should have a deep understanding of the cutting performance and material of the tool, and make allowance according to the actual situation;
(2) The tool must be measured accurately before clamping.
4. The cutting tool is not clamped firmly or extended too long, resulting in over cutting
Preventive measures:
(1) The clamping tool should be firm;
(2) The tool elongation generally does not exceed 2 / 3 of the total length of the tool;
(3) Under special circumstances, the tool must be extended (more than 2 / 3). The cutting amount must be reduced accordingly, and the speed and speed must also be reduced;
5. Excessive cutting amount causes broach over cutting
In cutting, the processor should consider the material and hardness of the workpiece, the rigid feed rate of the cutting tool and the machine and the rotation speed.
6. Over cutting caused by wrong adjustment procedure on site
Preventive measures:
(1) The site shall carry out the procedure according to the path specified in the procedure sheet;
(2) The site shall understand the operation sequence and coding principle of program code of the programming class;
Program code = two codes after mold number + workpiece code (two codes) + electrode serial number (if electrode is used) + program number.
7. Program writing error (for example: input error of boundary allowance floor surface)
2、 Causes of Tool Collision
1. NC code writing error;
For example, the zero point of the work piece is at the bottom or the center of the work piece, but not on the top surface of the workpiece. After the program is finished, the post processing program has a fixed height of = 50.0. When the distance between the required point of the workpiece and the top of the height is 50.0, the workpiece may collide with the cutter.
2. Inaccurate tool measurement;
Preventive measures: the tool measurement should be carried out with a more accurate tool as far as possible.
3. Program garbled code (knife collision caused by transmission error);
Program number call error or program has been modified, but still using the old program processing and writing date;
When the program sheet is changed, the principle of replacing the old one with the new one should be adopted to destroy the old drawings and the program list;
The on-site processor should check the detailed data of the program below as much as possible.
4. Wrong tool use or wrong tool writing in program list;
Prevention: add the program number and tool diameter to the program head.
5. The safety plane setting is not high enough, and the tool does not move when it is opened, resulting in knife collision;
For example: In order to save the time of tool lifting, two safety planes (the higher safety plane is greater than the high point of the workpiece, and the lower safety plane is lower than the high point of the workpiece and higher than the part to be processed) in order to save the time for lifting the tool on site. When the tool finishes machining a part, it is raised to the lower safety plane (due to the limitation of software) When preparing to process a part, the middle lifting tool passes over the boss, and the height is lower than the boss, resulting in knife collision.
prevention:
(1) After the program is written, the path of the program should be modeled;
(2) In view of the above question, in order to shorten the on-site processing time, it is necessary to write the processing procedures of each part separately, and then post them together;
(3) The distance between the tool and the workpiece is not enough, so that the tool can be directly inserted into the workpiece;
Prevention and reference standard: the length of tool feed and pull out should be greater than half shank of cutter.
6. The remarks of the procedure are not well considered;
Examples: (1) the height of the workpiece protruding from the vice is not enough;
(2) The swing range of clamping screw is smaller than that of tool path when lifting screw, which results in the tool hitting the surrounding screw;
(3) When the tool is noted, the tool collision will be caused when the elongation remarks are ominous or wrong.
7. Uneven residue;
8. The workpiece material itself has defects or hardness is too high;
The position of clamping block is not considered in the procedure;
10. If the residual material is not uniform enough to cause the tool collision, it is not considered whether the residual material distribution is uniform when compiling the processing program; it is easy to hit the knife when changing the small knife, because once the thick material is cut in a row under the condition of constant feed and rotation speed during processing, the impact force will increase, which will cause the cutter to hit.
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