1 INTRODUCTION Traditional methods for working time quotas include empirical estimation method, statistical analysis method, analogy comparison method, and technical measurement method. The use of computer-assisted quota formulation and management can overcome the shortcomings of poor accuracy, poor balance, labor intensity, and low work efficiency in these methods. It not only can improve the modernization level of enterprise's quota management, but also is one of the important links in the integration of CAD/CAPP, manufacturing (CAM) and management information (MIS/PRE/MRP). At present, although many companies have planned to introduce computers into labor time quotas, these fixed management software cannot be widely used in different companies because they are too specialized and coverage is too narrow. Therefore, the development of a general chemical time-setting system that satisfies different process environments and different production targets is of great significance.
Figure 1 Overall system structure diagram of working hour system
2 System Principle and Structure Computer-aided working hour system is based on the database of time quota formulation method, according to the different principles, can be divided into look-up table method, mathematical model method and hybrid method. The table look-up method requires that the working hours quota data under various typical and specific production organization technical conditions be stored in the database in advance. The CAPP system is based on the process design results, accesses the database according to the pre-designed logic, and performs the necessary statistical calculations. To determine the man-hours required for each step or process: The mathematical model method does not depend on a large amount of raw data, but it is calculated directly from the time-to-quota mathematical model created by the empirical formula: the hybrid method is a look-up table method and The combination of mathematical model method, it first through the look-up table method to find out the basic cutting data in the database to meet the query conditions, and then calculated according to the corresponding time-rated mathematical model, to obtain a single process or step man-hours. The system is a hybrid method. Its system functional structure is shown in Figure 1. The key to establishing working hours quotas using the hybrid method is the establishment of mathematical models for working time quotas. The general steps are: Determine the typical and specific technical conditions of the production organization, such as the model of the machine tool, processing methods, parts materials, processing batches, and parts technical requirements. This is the premise basis for establishing a time model. According to the above-mentioned selected typical conditions, search for information on working hours quotas, and analyze the relationship between working hours quota and major influencing factors (such as cutting depth, cutting speed, machining allowance, feed amount, number of passes, etc.) Typical calculation formula, establish the corresponding mathematical model. According to the various technological organizational conditions that have occurred in the actual production, as well as some influencing factors beyond the basic rules, the machine tool coefficients, material coefficients, and batch quantities were formulated separately. General chemical time quota system means that the system is suitable for different companies and different production objects. This must have the following functions: System refactoring function When a new production object appears, the user only needs to input some basic data such as the time data and mathematical model formula of the production object without modifying or adding any upper layer program. The calculation and use of the relevant work-time quota for this production object can be carried out: The format requirements for the report are different for enterprises with different report output functions, and the system should meet the requirements for various formats when the general chemical industry is used.
3 System Software Development Generalization is a technical difficulty and focus in the development of this system, and its degree determines the scope of application of the system. From the system structure diagram, we can see that the functional modules of this system mainly have the following parts. The time-to-work quota of the production object of the database creation module is mainly affected by various parameters. For example, for the vertical lathe cutting, the parameters affecting the work-time quota include the equipment model, tool material, processing object, processing method, and processing method. Different production objects have different influencing parameters. For example, for ordinary milling machine cutting, the parameters affecting work hours include machine type, tool material, machining depth, and cutter width, which are different from the time-varying parameters of vertical lathe cutting, so they are different. The production objects have different data structures. The traditional database design method adopts the multi-table method, which is to establish each table in the database according to the different structure of the basic data. As mentioned above, vertical lathe cutting and ordinary milling machine cutting need to build two different tables. This will inevitably result in: 1 Database maintenance is cumbersome. Since each table stores different data, the user must first maintain each data table in order to maintain the data: 2 Poor scalability. When a new production object appears, the user must redesign the table structure and create a new table in the database: 3 The database is redundant. Although there are differences in the work-time quota data structure of each production object, there are also similarities. Using different entities to create different data tables does not use its similarities at all, and it is bound to cause redundancy in the database. For example, the vertical turning machining time table and the normal milling cutting time table have redundant field tool materials. For the disadvantages of the multi-table database design and the requirements for system universalization, we adopted the single table design method. The basic idea is to first classify and encode the various production objects, determine the various types of data structures, and then extract the commonalities of various types, and finally determine and design the data tables. A total of two tables are used in this system: the specific data table ITEM_DATA and the parameter corresponding meaning table ITEM_MEANS. Through the summary of various forms of processing work, there are generally only two cases: one is to be able to directly give the last time data, such as a variety of auxiliary time (active, correct, unloading), quasi-final time (preparation, End), the other is to give only some cutting parameters that determine the final working hours rating, such as various cutting standards, given the cutting speed, cutting depth, number of passes and so on. We use attributes of other queries that are not related to man-hour calculations (such as width, length, etc.) to be expressed in the form of common parameters. Generally, this extraneous attribute does not exceed one, so we have designed a data table, the basic form of the table. See Table 1.
Table 1 Detailed data table: ITEM_DATA No. Field name Field type Field Meaning Description 1 TYPE_CODE VARCHAR2(4) Man-hour type number NOT NULL 2 PARA_1 VARCHAR2(50) Query parameter 1 3 PARA_2 VARCHAR2(50) Query parameter 2 4 PARA_3 VARCHAR2(50) Query parameter 3 5 PARA_4 VARCHAR2(50) Query parameter 4 6 PARA_5 VARCHAR2(50) Query parameter 5 7 PARA_6 VARCHAR2(50) Query parameter 6 8 V NUMBER(8,3) Cutting speed 9 T NUMBER(8,3) Depth of cut 10 S NUMBER(8,3) Feed 11 I NUMBER(8,3) Number of passes 12 TIME NUMBER(8,3) The time standard table contains a TYPE_CODE master code, used to represent different production objects, using four bits Coding format × × × ×, the first two represent the type of equipment, such as ordinary milling machine with MX, vertical lathe with LC: the third represents the type of work hours, such as the auxiliary time with A, cutting standards with C: fourth The bit indicates the machining type. For example, the machining plane is represented by P and the machining radius is indicated by R. In this way, we can use the coded LCCP for production objects such as the vertical lathe turning plane. The parameter correspondence meaning table refers to the specific meaning represented by the respective query parameters corresponding to different types of work hours in the specific data table. The specific table structure is shown in Table 2.
Table 2 Parameter Meaning Table ITEM_MEANS No. Field name Field type Field Meaning Description 1 TYPE_CODE VARCHAR2(4) Man-hour type number NOT NULL 2 PARA_N1 VARCHAR2(50) Parameter 1 Meaning 3 PARA_N2 VARCHAR2(50) Parameter 2 Meaning 4 PARA_N3 VARCHAR2(50) Parameter 3 Meaning 5 PARA_N4 VARCHAR2(50) Parameter 4 Meaning 6 PARA_N5 VARCHAR2(50) Parameter 5 Meaning 7 PARA_N6 VARCHAR2(50) Parameter 6 Meaning The user first classifies the specific production object, determines the codes (TYPE_CODE) of the various types, and then Determine the number and meaning of the query parameters. Enter the specific time data and code in the specific data table. If the time standard is given, enter it directly into the TIME field. Otherwise, the TIME field is empty, enter the specific V, T, S and I, at the same time in the parameter corresponding to the meaning of the table input the type of work type code and the corresponding meaning of the query conditions. This completes the creation of the underlying database. This kind of database has good universality in design, no matter how different the company's specific data table is, but because the parameters related to the working hours are basically the same, so you can use specific data tables to store data, and because the upper application is for data tables. Structural development, so it is not affected by specific data. In addition, this kind of database is very extensible. When the enterprise concludes a new form of work-time quota table, the user only needs to input its code and specific data into the data table, and input the meaning of each parameter into the meaning of the parameter. Can be used in the correspondence table. Finally, because there are only two tables in the database, data maintenance is more convenient, and the database is basically not redundant. Since the database management module is limited by the computer level, the user cannot directly operate the data table in the database. The development of the database management system is precisely to meet the user's requirements, it provides some simple, beautiful, and friendly based on the data table. Interface, and provide basic operation functions in these interfaces, such as data query, data insertion, data deletion, data modification, etc., to achieve the maintenance of the basic database, including specific data tables, parameter correspondence table, batch coefficient table, material coefficient Maintenance of tables and calculation formula files. With the development of graphical interface development tools, we can use some tools such as DEVELOPER2000, VB, Power-Builder, and Delphi based on ORACLE database. In addition to the above-mentioned functions, this module also needs to have another important function: user level management. Because the working time quota basic data is the standard that the whole enterprise establishes the work time quota, not all users have the right to modify the data, some are just a data access role, so the user needs to be graded and can be divided into two levels: advanced users and general user. Advanced users can perform all operations, such as data modification and deletion, which usually correspond to the factory's working time standard setter: while ordinary users can only perform data query operations, usually corresponding to the factory's working time fixed number. Work time quota formulation module For machining, the working time quota for each process consists of basic time Tb, auxiliary time Ta, layout working time Ts, resting and physiological time required Tr, preparation and termination time Te, etc. The formula can be expressed as Tc = Tb + Ta + Ts + Tr + Te/n (1) where n is the number of pieces per batch, because Te is the time for each batch to be prepared and completed, so it is allocated to each part. The final time is Te/n. Ta, Ts, Tr, and Te can be directly obtained by querying the specific data table ITEM_DATA through the work type number TYPE_CODE, and the basic time Tb needs to be obtained through calculation. The formulation process can be expressed by the following formula: Tb=SmSqF(x1,x2,...,xn ) (2)
Figure 2 Working hours development flow chart
In the above formula, Sm denotes the material correction coefficient, which is obtained by querying the material coefficient table: Sq represents the batch correction coefficient, and the query results in: x1, x2,... xn The cutting parameters affecting the working time quota can be obtained by querying the specific data table ITEM_DATA: F The calculation formula for this production object can be read from the calculation formula file. The main function of this module is to complete the above work. It accesses the basic database and calculation formula files through the input work time quota number, inquires out the basic data that meets the conditions, and calculates the man-hours corresponding to the selected procedure in conjunction with the specific working hour calculation formula. The program flow is shown in Figure 2. Report Generation Printing Modules For a time system, the main reports are Process Timesheets and Timesheets. Process time sheet is also the production ticket, which is used directly for the processing of parts and components and the arrangement of workers' work. Its production is generally based on the assembly or part of the unit, that is, the production of the selected assembly or all the parts of the process time sheet : Timesheet is a sort of summary of parts production and processing hours and manual labor hours. It is an important basis for cost accounting, and its production is usually in units or products. The traditional method of using a program to generate a table format has a lot of deficiencies, mainly as follows: (1) The program is complex and the format of the table is completely drawn by the program: (2) The print preview capability is poor due to the limitation of the screen. The generated table usually does not have a preview function. (3) The generality is poor. Since the format of the table is solidified in the program, the generated format is certain and cannot meet the needs of various formats. This module uses a method based on the WORD template to generate and print a table. It first creates a template directory on the user's local machine, and stores the process timesheets and timesheet templates created in accordance with certain rules. When the program is running, it opens the corresponding In the template file, the contents of the process timesheet or the timesheet are written on the template, thus completing the report generation and printing in the WORD environment. For reports in different formats, simply copy the report template to the template directory, which ensures the versatility of the system.
4 Concluding remarks For a long time, the strong specificity and poor generality were the key factors that led to the lack of promotion of computer-assisted work-hours software in the enterprise sector. However, as the social and professional circles have continued to deepen their research in theory and practice in recent years, the market has appeared one after another. In some general-purpose chemical software, more and more companies have introduced computer-aided work-time fixed-rate formulation techniques to achieve time-consuming fixed-item management from empirical management methods to advanced scientific management methods and to improve the comprehensive competitiveness of modern enterprises.
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