First, the basic concept of tool radius compensation
1. Why is tool radius compensation?
CNC machine tool in the contour processing process, it controls the tool center of the trajectory, and the user programming is based on the contours of the parts compiled, so in order to process the required parts, in the contour processing, the tool center must be offset Tool radius value.
CNC device according to the profile of the program and the pre-set tool radius parameters, can automatically generate the tool center center track function is called the tool radius compensation function.
2. The main purpose of the tool radius compensation function
① to achieve according to the programming track on the tool center track control.
② to achieve tool radius error compensation.
③ reduce the rough, finishing the workload of the preparation process.
3. Tool radius compensation of the commonly used method
Tool radius compensation principle
(1) B knife fill
Advantages:
√ The algorithm is simple and easy to implement
Tool radius compensation principle
Disadvantages:
× in the contours of the outer contour processing, due to the contour corners, always in the cutting state, sharp angle processing technology is poor.
When the contours are machined, the programmer must insert an arc with a radius greater than the tool radius in the part contour to prevent overcuts.
Tool radius compensation principle
(2) C knife fill
By the numerical control system and the actual contour exactly the same programming trajectory, directly calculate the intersection of the center of the adjacent tool, and then the original center of the track for the elongation or shortening of the amendment.
Good angle
√ In the contour processing, in order to avoid over-cutting.
Tool radius compensation principle Tool radius compensation principle
(3) B knife fill and C knife to make up
Difference: B knife fill method to determine the tool center trajectory, a processing track, using a read, calculate a section, and then take a section of the treatment. In this way, it is impossible to predict the influence of the machining path on the machining trajectory of the next section due to the tool radius compensation.
Tool radius compensation principle Tool radius compensation principle
Differences: C knife repair method is used to deal with two sections, that is, the first pre-treatment of this paragraph, and then according to the direction of the next paragraph to determine the center of the tool path between the transition state, thus completing the paragraph of the knife Arithmetic processing.
Second, the working principle of tool radius compensation
1. Tool radius compensation work process
The process of tool radius compensation is generally divided into three steps:
(1) knife repair to establish
(2) knife to make up
(3) knife off the revocation
Tool radius compensation principle
Use the tool radius compensation function
1, must be established in the movement and cancel the knife to make up, G41 / G42 did not make the tool movement function;
2, can not be established in the circular block and cancel the knife; tool radius compensation function can only take effect in the contour interpolation plane, and in addition to the interpolation plane outside the other axis does not work;
3, in the process of the implementation of the knife can not have two consecutive instructions for the non-interpolation plane movement of the instructions, otherwise produce a cut.
2.C tool compensation of the transfer form and transition mode
(1) Transfer form
In the general CNC device, there are two functions of circular and linear interpolation. As a result of the use of straight-line C knife transition, the actual processing process, with the front and rear two programming trajectory of different lines, will have a different transfer situation:
Tool radius compensation principle Tool radius compensation principle
(2) the transition mode
The angle of the vector α refers to the angle α of the two programming tracks at the non-processing side (the workpiece side) at the intersection
Tool radius compensation principle Tool radius compensation principle
According to the two procedures trajectory vector angle α and the difference between the direction of the knife, there are several following transition mode:
Shortened: Vector angle 180 ° ≤α <360 °
The tool center track is shorter than the transition path of the programming track.
Elongation type: vector angle 90 ° ≤ α <180 °
The tool center track is longer than the transition path of the programming track.
Insertion: Vector angle α <90 °
Insert a straight line transition between the two tool center trajectories.
Shortened
Vector angle 180 ° ≤α <360 °
The tool center track is shorter than the transition path of the programming track.
Elongation type
Vector angle 90 ° ≤α <180 °
The tool center track is longer than the transition path of the programming track.
Insertion type:
Vector angle α <90 °
Insert a straight line transition between the two tool center trajectories.
Third, the process of cutting the cut
When the contour is processed straight line, if the tool radius selection is too large, it will produce the phenomenon of cutting.
When reading the programming track CD, the upper tool center path B'C 'is corrected to determine that the tool center should be moved from point B' to point C '. Obviously, this will produce the cutting as shown in the shaded section.
Tool radius compensation principle
1. Straight-line processing of the cut method
It is possible to discriminate the positive and negative of the scalar product of the correction vector corresponding to the programming vector. In the above figure, BC is the programming vector, the correction vector corresponding to BC, and α is the angle between them. Then: Scalar tool radius compensation principle
Obviously, when the tool radius compensation principle (that is, 90o <α <270o), the tool will move back to the programming track, resulting in cutting. In the above figure α = 180o, so must produce cutting.
2. Arc cutting when the cutting of discrimination
If the tool radius rD is too large for the machining of the circular arc machining (G41G03 or G42G02), the over-cutting will occur if the radius R of the machining is exceeded.
Tool radius compensation principle Tool radius compensation principle
The over-cutting phenomenon occurs in the transitional form of the shortened type, and thus the principle of cutting can be judged on the basis of this principle, and the cutting discrimination program is designed accordingly.
Set the tool start position 50mm above the workpiece surface, cutting depth of 8.
When the N05 block processing AB contour, while reading N06 and N07 two, because these two for the auxiliary function instructions, can not make the vertical contour along the BC contour, and directly to the S point, resulting in over-cutting phenomenon.
