The servo motor is a very important component. Its quality determines the stability of the equipment directly, especially on the deformation of the machined contour. Besides its stability, there are many external factors that will directly affect the normal operation of servomotors.
For the laser cutting machine, whether the plate cutting or the pipe cutting, the key to the processing of the equipment in accordance with the established graphics is the dynamic response of each axis and the coordination between each other. If the overall response of each axis is too slow in the process of processing, or in some position, the deviation of the axis is small and the other axis is large, the problem of the deformation of the machining contour will appear. There are many reasons for this deviation, such as mechanical, external force, servo response, control system and other factors, or multifactor superposition. Therefore, the key to solve this problem lies in the good dynamic response of each axis and the coordination between each other, so that it can be processed strictly according to the established target. Servomotor, as an intermediate executing mechanism to undertake machinery and control system, can make up, optimize and coordinate the actions of each system to a certain extent, so as to achieve a more perfect control purpose.
Besides the stability of servomotor itself, the external factors that affect its normal operation
1. mechanical factors
Mechanical problems are relatively common, mainly in design, transmission mode, installation, material and mechanical wear.
2. mechanical resonance
The biggest influence of mechanical resonance on servo is that it cannot continue to improve the responsiveness of servomotor, so that the whole device runs in a relatively low response state. Such problems are more common in synchronous belt drive machinery, and long distance ball screws sometimes have such cases. The main reason is that the stiffness of the synchronous belt is low, the frequency of the resonance is low, the long distance of the rod has a larger inertia and more deformation, especially when the capacity of the motor is small. At the same time, the assembly process and the quality of the material will also affect the mechanical resonance.
3. mechanical jitter
Mechanical jitter is also a natural frequency problem of machinery. It usually appears in a single end fixed suspension structure, especially in the stage of acceleration and deceleration. The low frequency jitter will show a large wavy shape in the workpiece, and the jitter will appear in the higher frequency jitter.
4. mechanical internal stress, external force and other factors
Due to the difference of mechanical material and installation, the mechanical internal stress and static friction of each transmission shaft on the equipment may not be consistent. If the internal stress or the static friction of one axis in the two axis of the trajectory interpolation control is greater, the torque of the servo will be consumed to a certain extent, causing the acceleration of the axis to slow down, which leads to the deformation of the machining contour. Usually, we can observe the internal stress of drive shaft by feedback curve generated by servo driver.
The external force acting on the axis is similar. In general, there is no contact between the shaft and the workpiece, which may be limited by external force. But some pipe cutting machines, the feeding shaft will participate in the interpolation, while the other shaft is generally non-contact. At this time, the pipe will have a reverse force on the pipe shaft because of the influence of the fixture, so the force of the two axes in the interpolation control is not consistent, and the effect of the cutting will certainly be affected.
5.Numerical control system factors
In some cases, the debugging effect of servo is not obvious. At this time, we may have to intervene in the adjustment of control system. When laser cutting machine is processed, the line speed is usually constant, and it is the same speed on straight line and curve. This is not a problem in linear motion, but the contour deformation may be caused by too much acceleration in the machining of curves, especially for small size arcs.