What is logical chain analysis?

     The chain of logical analysis is focused on the physical relationship of the system, but in the normal state is determined based on system physical relationship, focuses on an action system in the final completion of what conditions must have. The realization process of logical chain including a function of hydraulic devices, from the first issue of motion signals to the actuator end of each link to the state of each link in the work process, the output link can be generated, and the information and the required energy input condition. Generally speaking, for a link, only the total quantity of the output is present, that is, the relation between the quantity of input and output is the relation of "door" and "gate". If this is not the case, if the output is in relation to the quantity of the input or the gate, or when a link has several outputs at the same time, it should be explained otherwise, or expressed in logical gates. The logic chain graph is extracted from the original device graph, and the part of the original pattern is related to the functional chain. Different functions can be represented by different logical chain diagrams. The specific method of logical chain diagram is associated with a function of the various components or devices to find out from the relevant drawings, according to the energy flow relationship before and after the information flow in logical block diagram of the way together again to indicate the logical relationship between each link output lost in the work process and the input amount the situation, as shown in figure 9-17.

According to the logical chain diagram to find fault, the standard and the tracking direction is: if the output of the first link is normal, then one output link is not normal, the problem is in the middle of the transfer process. If the quantity of a part fails to meet the requirements or is insufficient, it should be further examined in the direction of the quantity of the person who has not appeared or is not required. If the role and influence of a link in the whole function chain are excluded, the system eliminates the original fault, then the fault is in this link, otherwise, the fault is independent of this link. If the necessary input of a link is normal, and the output is abnormal, the fault is out of this link. If a link still has output in the case of insufficient input, there is a fault in this link. And if a fault action logic chain, which is a logical chain overlap with other action, but other action is normal, so that the period of overlap is normal, whereas the logical chain has a section overlap with another logical chain, the system function of two logical chain representation can show the same or similar symptoms, it is likely that a failure in the overlapping.

Logical chains can be made coarsely or finely. For a hydraulic component, the corresponding logical chain can also be worked out, and the parts that are not out of order can be omitted. If the thick line logic on one link was confirmed by a fault, this part creates a logical chain of fine, for further analysis. For the whole system, a rough network logic chain can also be made, so as to understand the whole process of the transfer of energy and information and the relation of each function.

In order to find the problem of the system quickly in the abnormal condition, the logical chain of the key actions should be compiled before the occurrence of the fault, and the detailed test and record of the normal parameters of each link should be made. On the basis of comparison as fault analysis, field practice, according to the specific circumstances of the scene, the original equipment and electrical, hydraulic and mechanical drawings for further transformation, transformation, refine the full analysis of the fault is of great help, but it is not difficult to do.

Application examples of logical chain analysis

Here, the logic chain of hydraulic circuit of a VK1-2 hollow molding machine is taken as an example to illustrate the application of logical chain analysis. The machine is imported from Germany, which is composed of a die opening and closing system (hydraulic) system (mechanical device), plastic blow molding products and processing system (pneumatic actuator), moving mechanism table (motor, brake and linkage mechanism composed of several parts). Each action involves a series of switches, electric motor and hydraulic pneumatic components, these components were made in different specifications and drawings, once an action does not run properly, to find the fault very laborious, so the logical chain diagram of key action. Figure 9-18 is the closing action of the logical chain diagram, here the box indicates that link, its name and code written in the box, link between wired connection, the arrow indicates to energy and information, people lose every aspect of the output parameters (can be observed feature quantity and test) and other available information (such as sound telecommunications lights, coil pull etc.) has also been included in the. In some cases, the output of the previous link is the amount of the latter, and they are consistent on the material, such as the output pressure of the reversing valve is the amount of the hydraulic cylinder. Is the only cause of causal relation is caused between the input and the output of another situation is before and after, such as the completion of the previous action caused by the start of a subsequent action, because the relationship between input and output electrical and hydraulic, pneumatic and other mechanical devices is clear, so the logic of establishment the chain is not difficult.

     Figure 9-18 shows that the logical chain diagram lists the main links involved in the closed die process, the States and relationships of the links, the detection points and the standard parameter values. If the problem is on the part of the person who has not been listed, it can be found out in relation to the logical chain and other information. There is a logical chain diagram, is not required to check over and over the same pattern and data need not be difficult to determine if a parameter is normal and indecisive. At this time, the fault analysis can be carried forward or reverse, and a section of it can be investigated.