1. Electrical control principle and common fault classification of dynamic balancing machine
(1) electrical control principle of dynamic balancing machine
Compared with ordinary machine tools, the core function of dynamic balancing machine is to detect, filter, analyze and calculate the unbalance produced by rotating parts, and finally remove the unbalance by cutting or drilling to realize the dynamic balance of parts. The realization of this special function is mainly controlled by a special industrial computer and a special dynamic balance software. Other auxiliary actions of machine tools are generally handled by another set of PLC.
Figure 2? Electrical control principle of dynamic balancing machine
Fig. 2 shows the electrical block diagram of the control system. Among them, the computer control system is a special industrial computer, which not only has the functions of ordinary industrial computers, but also includes data detection, filtering, analysis and calculation of part unbalance and sending feed instructions to the cutting feed system. It is also the core functional unit of the dynamic balancing machine control system.
Vibration sensor is used to detect the vibration and phase angle of unbalanced system, which provides the only effective data source for computer control system and is also one of the most critical components of dynamic balancing machine.
The spindle speed control system realizes the accurate control of the spindle and parts' rotating speed, and changes the parts' rotating speed as needed. Servo system is used to accurately control the unbalanced cutting of parts; Logical relationship between PLC management and control of all actions of machine tools.
Some functional components of Japanese KOKUSAI dynamic balancing machine are shown in Figure 3.
(2) PLC unit for classifying common faults of dynamic balancing machine
The faults of dynamic balancing machine can be roughly divided into two categories: control faults and error faults. Control failures are mainly hardware failures of electrical and mechanical executive components, such as computer control system, operation display unit, PLC, speed control system, servo system, servo motor and rotary oil cylinder, and other mechanical executive components such as swing frame. Among them, computer control system failures include computer hardware failures and software failures. Error fault mainly shows that the calibration, measurement and weight removal of dynamic balance system have large errors or cannot be carried out normally.
The treatment method of control fault is similar to that of ordinary CNC machine tools, mainly hardware diagnosis, replacement or adjustment. However, because there is no alarm, it is often necessary to track the analysis process and deal with it by fine-tuning control parameters, process parameters and static characteristics of machine tools. This paper mainly introduces the analysis and treatment methods of fault.
Figure 3? Japan KOKUSAI Dynamic Balancing Machine Group Diagram
2. Handling of errors and faults of dynamic balancing machine
Error faults of dynamic balancing machine mainly include calibration faults, measurement faults, cutting control faults and cutting curve faults of dynamic balancing system.
Analysis and treatment of (1) calibration detection fault
The so-called calibration failure refers to the failure of the machine tool in calibrating the detection system, which is mainly manifested as: the machine tool can not complete the calibration of the dynamic balancing machine detection system according to the process specified by the manufacturer. The probability of calibration failure is not high, and the general problems appear in the following aspects:
① Vibration sensor failure: The main cause of failure is vibration sensor looseness, damage or poor line contact. As the vibration sensor is the direct detection element of vibration quantity of dynamic balancing machine and the data source of computer processing system, its performance and fastening state will directly affect the accuracy of data acquisition of dynamic balancing machine.
(2) Clamping failure of calibration parts (or parts): the workpiece is not clamped, and the parts (standard parts) swing when rotating, resulting in extra imbalance, which makes it impossible for the machine tool to effectively calibrate or measure parts, and obviously leads to errors.
(3) The swing frame of the machine tool is loose, which makes the rotating mechanism unbalanced and unable to calibrate. Looseness of swing frame will not only cause measurement error, but also cause error of parts weight removal, which is often ignored.
(4) The machine bed is not horizontal due to the loose base: because the machine bed is not horizontal, the machine tool vibrates when the parts or standard parts rotate, which interferes with the data acquisition of vibration sensors, resulting in errors in system calibration or measurement.
⑤ The improper rotating speed of parts leads to abnormal data acquisition, which is also the most easily overlooked. Different rotational speeds of parts or workpieces will produce different vibration quantities. When calibrating the system, it is required that the rotating speed of the measuring part is within the specified range, otherwise the calibration data will have great errors. Similarly, if the calibration is not accurate, there will be great errors in the calculation of the unbalance of the machined parts.
⑥ Rusting of standard parts or counterweight leads to calibration deviation, which is also easily overlooked. Therefore, attention should be paid to calibration and weight preservation.
(2) The machine tool detects a new imbalance in the processed parts.
This kind of fault is also the fault with the highest probability. After this kind of fault occurs, it is necessary to judge whether the imbalance appears in the same direction or in the opposite direction. Different treatment methods are different for different phenomena. The reasons for this failure are as follows:
① The cutting allowance is insufficient, and the original imbalance has not been eliminated. This imbalance will appear in the same direction, which can be quickly solved by improving the cutting feed ratio coefficient or recalibrating.
(2) The cutting allowance is too large, which leads to imbalance in the opposite direction. In this case, it is necessary to calibrate the system first, and then reduce the cutting feed by reducing the cutting feed ratio coefficient. In this case, the phase angle of the unbalanced point is generally symmetrical, indicating that there is no problem in phase angle detection.
③ The fault of vibration sensor leads to large measurement error. See the analysis and treatment methods in the previous article.
(4) Abnormal phase calculation of unbalance leads to new unbalance. If the phase angle of the new unbalanced point changes continuously through repeated rework, it may be an error in the phase detection of the system. Check or replace the sensor, and fine-tune the phase angle parameters of the system if necessary.
⑤ Uneven distribution of blank particles leads to duplicate removal errors: Uneven distribution of single blank particles and mismatch of duplicate removal calculation directly lead to duplicate removal errors.
3. System program or calibration curve failure.
The early control software of dynamic balancing machine generally belongs to DOS version. Every calculation of weightlessness is approximately determined according to the "cutting curve". "Cutting curve" is a preset curve generated by simulating 5 ~ 10 different unbalance quantities corresponding to different weightlessness. The curve can be adjusted according to the change of the particle distribution of the blank. If the product blank is replaced in batches, the blank particles will change greatly, and the original "cutting curve" is no longer applicable, so it is necessary to adjust the "cutting curve", otherwise a large number of parts will be unqualified. In addition, it is necessary to adjust the "cutting curve" when the life of the machine tool is long and the unbalance of the rotating parts such as the spindle increases and it is impossible to calibrate.