Technical improvement of cement packaging machine

For enterprises, the technical improvement of cement packaging machines, the improvement of bag weight control level and the reduction of sample standard deviation have significant economic benefits.

First, the type of cement packaging machine:

1. Bag weight control principle and characteristics of various types of cement packaging machines Cement packaging machines can be divided into mechanical and electronic types according to weighing methods.

1) Mechanical packaging machine: The weighing mechanism is manufactured according to the principle of leverage. The end of the lever is equipped with a weight, the other end is the scale, and the middle is the fulcrum. The weight of the bag is controlled by the up and down rotation of the lever mechanism. The bag weight control performance of the mechanical packaging machine is very poor for two reasons: one is that the weight, the frictional resistance of the fulcrum, the falling ash on the bag seat are all brought into the metering, causing the zero deviation of the scale, and in the cement packaging process In the middle, the ash is unavoidable; the second is that in the dust environment, the flexibility of the lever fulcrum is easily affected.

2), electronic packaging machine: rely on the spring piece to support the scale frame, the weighing sensor detects the bag weight, the controller measures the cylinder, and the cylinder (or electromagnet) is the actuator. The electronic control system can remove the scale to zero before each bag of cement is loaded, ensuring the accuracy of the zero point of the scale, while the cylinder (or electromagnet) is less affected by the environment and the action is reliable and rapid.

2. According to the movement of the loading unit, it can be divided into fixed type and rotary type.

1), the fixed packaging machine often has a single mouth, double mouth, four mouths, the operator is sitting in front of the scale frame to operate, because the operator's hands and feet can touch the scale frame at any time to change the bag smoke, so this package Bag weight control is easily interfered by human factors, and the fixed packaging machine has low labor productivity and is suitable for small and medium-sized cement plants.

2) Rotary packaging machines are commonly used in six nozzles, eight nozzles, fourteen nozzles, etc., during the rotation process, the operator can not interfere with the weight of the bag, and the rotary packaging machine labor productivity is much higher than the fixed type. Due to its high output and excellent bag weight index, it is more and more widely used.

3. Bag weight control and practice of rotary electronic weighing cement packaging machine Domestically produced domestically produced machines made in Tangshan, Huangshi and Wuxi, as well as imported German HAVER machines, have the same working principle and process, mainly during maintenance. The scale is required to be clean and flexible, and the actuator is quick and reliable.

Second, the technical improvement of cement packaging machine:

1. The secondary charging technology has a constant speed during the filling process of the packaging machine (may be called one-time filling). Some adopt the secondary charging technology, that is, the fast-slow charging method, which reduces the filling speed when approaching the target bag weight (such as about 45kg) to improve the accuracy. On the packaging machine using the secondary charging technology, the opening degree of the fine charge is adjusted to the maximum, and the standard deviation of the sample is sharply increased.

2. The closed-loop control system installs the conveyor roller and the calibration scale after the belt, and forms a closed-loop control system with the central controller of the control room and the controller on the packaging machine to continuously correct the bag weight. It is important to note that in the closed-loop control system, the bag weight is based on the calibration scale. The calibration scale detects the total weight of each bag including the tare weight. There is no automatic skin removal function, and it is impossible to adjust the tare change of the tare. Therefore, the ash should be cleaned up in time during the production process, and the zero point of the calibration scale is always kept stable.

3, the transformation of the primary filling and packaging machine controller secondary loading technology can significantly reduce the bag weight error, but compared to a single filling, increase the controller output points, increase the solenoid valve and three cylinders (using electromagnets), Reduced production time and increased manufacturing costs, so some packaging machines did not adopt secondary charging technology. Through the exploration, the author does not need to add any equipment on the packaging machine that drives the impeller and the cylinder (electromagnet) to drive the shutter. The stop signal of the motor is only slightly advanced from the target bag, for example, set to 50kg, and the cylinder The closing signal of the (electromagnet) is still 50.5 kg, so that the inertia of the motor constitutes a secondary charge.

4. The understanding of secondary filling technology may be due to cost considerations. Some packaging machine manufacturers have objections to secondary charging technology and consider it unnecessary. However, HAVER, a veteran manufacturer of packaging machines, believes that secondary charging is essential, and the time for fine charging should be greater than 2 s. In practice, the author also realizes that the secondary charging technology is essential for improving the measurement accuracy, and in practice, the original one-time loading is changed to the secondary charging without adding hardware or increasing the cost. The solution works well.

5. Practice on the three-time filling technology On the packaging machine that has adopted the secondary charging technology, the secondary charging time can be shortened without increasing the hardware or increasing the cost, and the charging motor is stopped in advance, relying on the motor. The inertia constitutes three times of loading, which is beneficial to the machine work. The metering accuracy can be further improved without affecting the output of the packaging machine. The three charging times depend on the inertia time of the motor stop. The motor on the HAVER packaging machine has energy consumption braking, so the parking is fast. At present, the secondary charging conversion point set is 47kg (HAVER original setting 42kg), and the three charging conversion point is 49.5kg. These setting values ​​need to be based on the user's own charging motor for braking, bag weight index requirements, and machine. The actual conditions such as Taiwan's production requirements and cement flow performance are determined. Bag weight accuracy requirements are strict, it is necessary to reduce the secondary and tertiary loading transition points, while the machine table production is reduced; cement flow performance is poor, it is necessary to increase the secondary and tertiary loading transition points. A unit of HAVER 6RS (FE), HAVER 6RSMECII packaging machine has been practicing for a long time, for the purpose of cost reduction, developed a controller, in June 2007 in HAVER 6RS (FE) packaging machine No. 5 Trial on the nozzle, normal debugging in mid-August. From August to now, the bag weight setting has not been adjusted, and the bag weight is checked several times, and the effect is satisfactory (data is omitted). Practice has proved that the controller works reliably, and three loading techniques are feasible.

6. The improved closed-loop control system of the open-loop control system can greatly reduce the error, but it needs to increase the calibration scale, the central controller, etc., and the cost increases a lot, especially because the calibration scale does not have automatic peeling function, if the production process falls The ash cannot be cleaned up in time, but it causes serious bag weight errors. After the calibration scale of a unit packaging machine system is damaged, the design of the packaging machine controller is improved during the localization of the accessories, so that the open-loop system realizes the function of closed-loop control. The control principle is: we detect the bag weight again and compare it with the preset value, and adjust the preset value according to the comparison result, thus forming a closed-loop control system, which has proved to be feasible.