【CNC Machine Tool】Common problems in wire cutting

2021/05/27

【CNC Machine Tool】Common problems in wire cutting

How is the straightness of X and Y motion guaranteed?

First of all, it should be clear that the straightness of a certain axis refers to its straightness in two planes. For example, the straightness of the X axis refers to the straightness on the X and Y planes and the X and Z planes.
The pallet of the machine tool is carried on the guide rail, so the straightness of the guide rail determines the straightness of the movement. There are two reasons for the loss of straightness, one is the flatness of the guide rail itself, and the other is the flatness of the guide rail installation reference surface. High-precision and stable guide rails, the combination of the pallet and the bed are the fundamental conditions to ensure straightness. The purpose of the high and low temperature and aging treatment of the guide rail, pallet and bed is also here.
It is also obvious that the inconsistency of the rollers (steel balls) will result in fewer stress points or pry plates.
It should be noted that the irregular movement of the lead screw will also affect the guide rail. For example, the axial direction of the lead screw is not parallel to the guide rail, the center height of the lead screw and the screw nut is inconsistent, and the lead screw and the screw nut bear a torsion force and the screw The bending of the screw will interfere with the linear motion of the guide rail when the screw is moving. This is what we emphasize to make the screw, screw nut, screw seat and nut seat accurately. The basic reason for the specification.
Regardless of the "V" shape or the "one" shape, the guide rail and raceway must not be contaminated with any dirt or impurities, which not only affects the straightness of the guide rail movement, but also leads to damage and deformation of the guide rail. The guide rail is required to be spotless, which is one of the rules for maintaining and maintaining machine tools and maintaining long-term accuracy.

How is the verticality of X and Y motion guaranteed?

The perpendicularity of the two axes is established on the basis of their respective straightness. The error of the straight line will be reflected in the perpendicularity measurement. The result of the superposition of the values makes the perpendicularity measurement inaccurate, so the first to ensure the respective straightness, Then ensure mutual perpendicularity.
The verticality of the two axes depends entirely on the verticality of the two sets of guide rails on the middle pallet. When assembling, one set of guide rails is fixed on the reference, and the other set of guide rails are measured and adjusted until the other set of guide rails are perpendicular to the reference. Punch the pin holes to fix the verticality of the two sets of guide rails on the middle pallet. This assembly and measurement process is to pursue a safe and effective operation, and it should also deliberately increase the accuracy by one level. The control of this intermediate process index is very important, because whether it is installation, repair or actual results for a period of time, this accuracy will be achieved. Worse, if the allowable error value is fully used in the initial installation, the accuracy will be overvalued in the future. For example, if the accuracy standard of a machine tool is 0.02, the internal control accuracy during the first assembly should be below 0.012. The first installation of important parts is strictly controlled and the pins are stable and effective. In addition to the straightness and accuracy of the guide rail itself, the verticality of the two axes is guaranteed.
Like straightness, the working state of the lead screw is also an important factor affecting verticality. Any external force that forms a certain angle with the positioning surface of the guide rail will cause abnormal movement of the guide rail, because the guide rail is only a guide rail and is not clamped. Therefore, once the verticality of the X and Y axes is found to exceed the standard, it is necessary to carefully judge whether it is caused by the deformation or misalignment of the guide rail itself or the movement interference of the screw. If it is caused by the guiding effect of the guide rail, repeat the fitting process of loosening and tightening the lead screw and the nut at several positions respectively, and the direction and value of the over-standard should be generally stable. If it is caused by the interference of the movement of the screw and the screw nut, the direction and the regularity of the value will be lost. Never loosen the fixing of the guide rail blindly and remove the pins. Any operation that loses judgment is useless. Once the fixing and loosening nails of the guide rail are removed, the whole process of the first assembly and adjustment described above must be repeated.
Any measurement adjustment must be carried out after the guide rail moves smoothly. If sudden jumps and irregular twists are caused by the guide rail is too dirty or foreign matter, it must be resolutely wiped off and lubricated before making adjustments. This must be kept in mind.