Model design of sheet metal quotation system


5.1 The functional module structure of the system
Product quotation refers to the requirements of the inquired company for the product specified by the customer and its special materials, craftsmanship, delivery date and other requirements based on factors such as product technical requirements, its own business management status, market environment, and customer characteristics. The quoted price. Product quotation is a complex and important economic activity. Its speed and reasonableness will help both parties to quotation sit face-to-face, and after repeated discussions, determine the transaction price of the product, specific trade details, and finally reach an agreement and sign a contract. Like the quotation of many products, the quotation of sheet metal products requires the coordination of various departments, such as technology, finance, business, etc., and various factors must be considered comprehensively. Through the previous analysis of sheet metal parts cost estimation and quotation process, this paper establishes a sheet metal part quotation model.

5.1.1 Overall functional module structure
According to the research on the cost composition and cost estimation of sheet metal parts, in order to make the sheet metal parts quotation system meet the actual situation of sheet metal manufacturing enterprises and better meet customer needs, the system needs to focus on solving the following problems:

(1) Reasonable arrangement of the technological process of sheet metal processing;

(2) Estimation of working hours and working hours quota for sheet metal processing;

(3) More accurate cost estimation and quick quotation for sheet metal products.

Therefore, the system can mainly set up four modules, namely, auxiliary manufacturing module, man-hour quota module, quick quotation module and database management module.

The auxiliary manufacturing module mainly completes two functions: process planning and processing simulation. First, use the basic principles of group technology to classify the sheet metal parts, and use the expression method based on feature elements to describe the various features of the parts, that is, use the part description method of Tsuen Yu coding. The user only needs to select the corresponding according to the graphics or text prompts. The parts can be expressed more accurately by entering the necessary parameters in the project well, which is the prerequisite for process planning. The parameters of parts mainly include two types: one is the overall characteristic parameters, such as materials, heat treatment requirements, topological shape and size, etc., which can be selected through text prompts; the second is geometric parameters, including the type, size, and location of each component Relations, accuracy, etc. can be obtained from sheet metal CAD drawings.

Process planning can be composed of two parts: pretreatment and process route generation. Preprocessing is to obtain the local process information of each element through calculation, analysis, and reasoning based on the parameter information of the characteristic elements, such as the positioning of each element, dimensional accuracy requirements, tooling conditions, etc., and then conduct a comprehensive induction to obtain the overall information of the part, and then according to The partial and overall information of the parts obtained by reasoning, combined with the basic principles of process planning, such as the principle of process concentration, the principle of benchmark coincidence, etc., generate specific processes, machining residuals and tooling equipment, generate processing technology cards and sheet metal unfolded drawings, and apply CAD/ CAM technology adds simulation to sheet metal parts.

In the man-hour quota module, first set the threshold, retrieve a number of qualified and matching case parts from the case library, and estimate the processing man-hours of the parts. If it is difficult to retrieve matching cases, calculate the processing man-hours section by section through the processing route obtained from the process planning module, determine the lead man-hours of the parts after comprehensively considering the relaxation time and various coefficients, and estimate the production period at the same time, It creates favorable conditions for the enterprise's optimal management, the realization of cost estimation and the determination of the delivery date.

The quick quotation module mainly achieves two purposes: the cost estimation of sheet metal parts within the enterprise and the quick quotation of customers outside the enterprise. First, use the activity-based costing method to divide the sheet metal parts manufacturing process into five operation centers, determine the cost driver rate of the five activity cost libraries, and calculate the sheet metal parts according to the number of cost drivers of each activity cost library consumed by the sheet metal parts Accumulate the various costs consumed in each cost library, plus other expenses such as the salary, office expenses and benefits of the company's administrative, financial, personnel and other management personnel to estimate the manufacturing cost of sheet metal parts. Then, comprehensive product technology, business status, market environment, customer characteristics and other price-influencing factors, use appropriate goals, strategies and methods in quotation decision-making to make fast and reasonable quotations to customers.

Of course, the system must have a unified database management structure to support the operation of each system, and unify information such as user permissions, customer information, various technical parameters, query of working hours quota, and history of cost estimates and quotations. Efficient management. The functional modules of the entire system are shown in Figure 5-1.

Among the four modules of the sheet metal quotation system, the database management module is the basis for the operation of the entire system. After obtaining the sheet metal engineering drawing, various data in the database management module must be called to perform various types of engineering drawings in order. Processing to obtain various data that is conducive to processing and quotation, especially for auxiliary manufacturing modules, only to make full use of various processing technology information, to transform the geometric information in the sheet metal CAD engineering drawing into process information, and to choose various intelligently After processing the parameters, the processing simulation is realized for the whole processing process, and the efficient integration of CAD/CAM is truly realized.

Relative to enterprise users, the two modules of working hours quota and quick quotation mainly realize internal and external functions. The working-hour quota module internally realizes the estimation of the working hours of parts and the scheduling of the working hours of the approved parts, creating conditions for the company to formulate the main production plan and quantitative management, and realizes the production time estimation externally, creating an accurate and timely response to the customer’s delivery date Conditions: The quick quotation module can realize the cost estimation, analysis and management of various costs of parts internally. After selecting various quotation decisions and methods, it can externally realize timely and reasonable quotations to customers with different characteristics in different market environments.

5.1.2 Quick quotation function module structure
According to the principle of cost accounting, the cost of manufacturing products mainly consists of three parts, namely production cost, product profit and taxes. Combined with the specific conditions of sheet metal manufacturing, the following factors are mainly considered in the quick quotation module:

(1) Estimation of working hours. According to the sheet metal CAD engineering drawing, the part is described based on the code, the process flow planning is carried out, and the feature information is extracted at the same time, the processing time of each process is estimated, and the cost of the sheet metal processing operation is calculated through the labor time rate of each unit.

(2) Other operating costs. According to the information in the sheet metal CAD engineering drawing and the reservation form, estimate the total cost of each other operation cost. By obtaining the cost driver rate of other operations other than the processing operation, the cost of other operations of the metal parts can be estimated. The sum of it and the cost of processing operations is the production cost of sheet metal parts.

(3) Fixed costs such as office expenses, financial expenses and various benefits; various influencing factors for quotation decisions; taxes and fees. These costs or factors need to be determined according to the specific circumstances of the company, market, policy and order. Therefore, the structure of the quick quotation function module is shown in Figure 5-2.

5.2 System information model and basic data flow
5.2.1 Information model of the system
The rapid quotation system for sheet metal parts is carried out on the basis of product information sharing with the support of the overall technology of concurrent engineering. Quick quotation includes several processes such as receiving customer inquiry information, product technical scheme design, production cost estimation and quotation document output. The information flow is shown in Figure 5-3.

After the enterprise receives the customer’s inquiry information, in order to respond quickly to the customer, the sales department, production technology department, finance department, project management department and other departments coordinate their work and work in parallel with the support of the computer network and product data management system. . The sales department passes the customer’s product technical performance requirements, delivery time and method, quality requirements and other inquiry information to the production technology department, and at the same time, the customer’s acceptable price requirements and product characteristics, market prices of similar products, and customer characteristics Information such as type is passed to the project management department.

According to the needs and various requirements of customers, the production technology department conducts feasibility analysis of product manufacturing, formulates product technical solutions, and estimates the shortest completion time and manufacturing cost of the product, and then forwards the product technical solution, shortest delivery time and other information to sales Department, and pass the estimated manufacturing cost to the Finance Department. The finance department calculates the cost of sales of the product and passes it to the project management department based on factors such as manufacturing costs, office expenses, financial expenses, welfare fees, profits, and tax rates.

After receiving the cost of sales of the product, the project management department will compare the price acceptable to the customer with the cost of sales. If the cost of sales is higher, it will feed back the information to the production technology department, which will reduce the cost of sales by improving product technical solutions. After satisfaction, the project management department will formulate product prices based on comprehensive market environment conditions, product characteristics, competitive prices, customer characteristics, and other information, and feed them back to the sales department. The sales department feeds back information such as product technical solutions, sales prices, delivery time and methods to customers.

5.2.2 Basic data flow of the system
During the operation of this system, a large number of various types of data are involved, whether it is man-hour estimation, processing simulation, cost estimation or quick quotation. These data must be managed and maintained. The database can organize a large amount of data in the information system according to a certain model, and provide the functions of storing, maintaining, and retrieving data, so that the information system can easily, timely and accurately obtain all the data from the database. Required information. The design of the database is the foundation for the establishment of the database and its application system, and is the core technology in the development and construction of the information system. The system uses SQL Server database, which is a client/server relational database management system (RDBMS), which uses Transact-SQL to send requests between the client and SQL Server.

For the sheet metal quotation system, the main work of the database includes the basic information of the sheet metal CAD engineering drawings extracted by the user, query and related calculations required processing parameter database, working hours quota database, etc. to estimate the cost of sheet metal parts, and at the same time according to customers Information database, quotation decision method database, quotation history database, etc. get profits. Through detailed analysis of system requirements, the basic data flow chart of the system is obtained, as shown in Figure 5-4.

Through this basic data flow chart, you can clearly see the flow of all the databases required by the system and all the basic data used in the system.

5.3 Process parameter database design
When applying the activity-based costing method to estimate the various costs consumed in the operating cost library of sheet metal parts, the estimation of the total cost driver is a key point, which is related to the accuracy of the estimation. Among the five activity cost libraries, processing activity cost drivers are always the most important, that is, the estimation of the processing man-hours of sheet metal parts is the top priority. The processing technology parameter database with reasonable design structure and convenient auto inquiry and application is an important basis for sheet metal processing man-hour estimation. The following takes the sheet metal CNC cutting process parameter database as an example to illustrate the design concept of the sheet metal process parameter database.

5.3.1 Establishment of the database
After extracting the geometric information in the sheet CNC cutting agent engineering drawing, in order to obtain the cutting hours, it is necessary to determine the appropriate cutting speed of the processing equipment. The cutting speed has many influencing factors, which are determined by many factors such as processing equipment, workpiece material and specific processing parameters. For example, for laser cutting, there are the laser power of the laser cutting machine, the diameter of the nozzle, the surface reflectivity of the sheet, the thickness of the sheet, the type of auxiliary gas, the air pressure, and so on. Due to the changes in the processing objects and various conditions, the combination of these parameters is quite complicated, the data of the process parameters is the largest, and the selection of the process parameters is very difficult.

A workpiece material has several plates with different thicknesses, and each thickness of the plate has many sets of processing parameters. Therefore, each set of processing parameters is related to a certain material and a certain thickness. In order to avoid a lot of redundant information, it is necessary to store the processing parameters separately from the material properties of the workpiece to which they belong. According to their affiliation, we divide the storage mode into two layers: the workpiece material properties are stored in the first layer, and the processing parameters are stored in the first layer. The second floor. Between layers, the method of introducing the keywords of the previous layer's record into the next layer's related records is adopted, so that the processing technology parameter database has the storage mode of a relational database. The specific format is shown in Table 5-1 and Table 5-2.

In the record format 1 material attribute record, assign a system unique material code as a key to each material. Use the recorded material melting point and the degree of easy oxidation to select the oxygen flow in gas cutting and the auxiliary gas type in plasma and laser cutting, and use the recorded material hardness to select the water pressure and abrasive type in water jet cutting. For example, for workpieces with low melting points, oxygen flow should be appropriately reduced during gas cutting. Oxygen should not be used as auxiliary gas in plasma and laser cutting, otherwise it will produce more sticky slag, and inert gas should be used as auxiliary gas for materials that are easy to oxidize; For workpieces with high material hardness, chromium silicate or emery should be selected as abrasives in water jet cutting. In the record of record format 2 cutting parameters, the workpiece material code and material thickness are used as joint keywords to store a large number of processing conditions, which is the main part of the processing technology database.

The information contained in database records is stored in various fields. Defining the database structure involves creating several fields to store the information collected by users for each record in the database table, so as to effectively manage the database, including determining database fields and defining fields Type and its length. The following aspects should be paid attention to when determining database fields:

(1) Increase the completeness of the database
The purpose of the database system is to create useful output information and information that users can use for summary and analysis. Therefore, before establishing a processing parameter database, each useful data should be carefully analyzed. For example, different sheet materials, sheet thickness and cutting quality are the most demanding. Since the types and contents of the processing parameters involved are quite different, the structure should be designed to make the record content as comprehensive as possible, and the system should be able to carry out effective queries and judgments.

(2) Database resources adapt to shared needs
In most cases, a database does not exist in isolation. It may call other data resources, or may be called by other databases. Therefore, when establishing a database, it must be beneficial to data sharing.

(3) Reduce data redundancy
When there are many fields, multiple tables can be created at the same time, and they can be connected according to the common field, but be careful to remove the information items that can be found in other files in each table to avoid redundancy. That is, the database organization should not include repeated redundant fields. For this reason, various data should be processed in an orderly manner in order to establish a suitable data structure.

(4) Field naming is simple and clear
Before establishing a database, a set of naming rules should be established for each field. These rules should be simple and easy to understand, easy to remember, easy to understand when modifying the system, and avoid unnecessary puzzling abbreviations.

Taking laser cutting as an example, Table 5-3, Table 5-4 and Table 5-5 are the material name table, input parameter table and cutting parameter table established in the cutting process parameter database.

5.3.2 Data query and application
In the actual processing parameters, there are only a limited number of values ​​for certain parameters, such as auxiliary gas types, nozzle shapes, etc. Their reasonable selection only requires certain process knowledge and logical reasoning, while for other parameters, such as The laser power, the pressure and flow of the water jet are the most equal. Their values ​​are intervals, not selectable sequences. The determination of such parameters requires not only logical reasoning, but also model calculations. According to this feature, the laser cutting process parameters can be divided into two categories: qualitative data and fixed minimum data.

(1) Qualitative data
This type of data determines the nature of the processing conditions. Data with different values ​​is essentially different. They generally do not have a transitional state. It is very important to choose them correctly. Their changes make the processing technology change significantly. For example, the shape and diameter of the nozzle in gas cutting. The nozzle is used to spray auxiliary gas to the cutting agent area, and its structure and shape have a significant impact on cutting efficiency and cutting quality. The shape of the gas cutting nozzle generally has two types: ring and quincunx. The diameters are 1, 2, 3, and 4.

For another example, in plasma cutting or laser cutting, the choice of auxiliary gas type mainly depends on the chemical characteristics of the workpiece material and the processing quality required by the user. According to experience, only inert gases such as nitrogen or hydrogen can be used for flammable materials, not oxygen. When encountering a variety of auxiliary gases that can be selected, the auxiliary gas should be selected according to the best processing quality under the action of different auxiliary air, and on the premise of meeting the user's processing quality requirements, the auxiliary gas that can make the processing efficiency the highest. The optional sequence of this type of data can be represented by a set, which is more convenient to process.

(2) Quantitative data
This kind of data is taken in a limited area and can be continuously changed, and the changed value has a certain influence on other processing parameters, such as the thickness of the workpiece material, laser power, water jet pressure, etc., although their values ​​are An interval, not an optional sequence, but it should still be directly accessible in the database.

In the actual processing process, a lot of user experience cannot be found in this process database. For example, the plate does not have a specific thickness, and the cutting quality does not have relevant data for good evaluation. Therefore, it is necessary to introduce the concept of "fuzziness" into the database. Corresponding process data can be obtained for any processing conditions within the effective range, which is convenient for actual operation.

Fuzzy relational databases are based on traditional relational databases, which can express and process inaccurate and fuzzy information. Such as workpiece thickness, machining accuracy requirements, etc. When there are workpiece material thickness, machining accuracy requirements and other parameters in the process database, it is convenient to select a set of recommended parameters from the process library as the current machining parameters, or make some small The adjustment. When there are no parameters such as workpiece material thickness and machining accuracy requirements in the process database, the required parameters need to be deduced fuzzy.

Applying fuzzy relational database theory to modify and expand the process parameter database can better solve the problem of no selectable sequence for fixed emblem data. In establishing fuzzy relational data, the two practical aspects of workpiece thickness and machining accuracy should be considered. The continuous quantity in the processing is blurred, the attribute values ​​of the workpiece thickness are very thick, thick, medium, thin, and very thin, and the attribute values ​​of the workpiece processing accuracy are high, medium, and low. It can be seen from Figure 5-5 that for each point with a degree of membership of 1, the corresponding attribute value is each open point corresponding to the process data, and the process of querying the model period is based on the theory of fuzzy relations. The arbitrary processing conditions in the universe of discourse are attributed to these discrete points, and the final output is obtained.

In the specific database implementation process, the extended structured query language SQL for the fuzzy relational database can be used. By extending the SQL language, it is possible to establish a laser cutting process parameter database based on the fuzzy relational model. In this database, the query process is to fuzzify the user's input first, then perform fuzzy inference and search, and finally refine the output results to obtain certain processing parameters.

When the user uses the process database for cutting processing, its input is a certain amount, and the database output is also an accurate value. Therefore, the fuzzy relational process database actually performs fuzzy inference on the query process by establishing a fuzzy processing condition table, so as to obtain the input from the user. The closest process data. Such a fuzzy relational database has a unique output for any input in the application range, which solves the problem that the actual processing condition input is difficult to obtain the corresponding output, can automatically select the processing parameters, and make sufficient preparations for the automatic control of processing.

5.4 System workflow
The workflow of this system mainly includes the following four aspects:

(1) The user accepts the customer's inquiry and logs into the system safely within the scope of authority.
The system first confirms the different identities of the users. Only the super users with the authority of the super administrator can use all the functions of the authority management module. They can add, delete, assign and modify the access and operation authority of each user to the database, and all of the system The database is managed and maintained, and other users are given limited operation rights depending on the nature of their work.

There are two types of users in the system: ordinary users and administrators. Ordinary users can perform operations such as inputting information, querying information, quotation, etc., but cannot make any changes to the system data. All information submitted by ordinary users must be reviewed by the administrator before it can be determined whether to enter the system database; the administrator can perform all operations on the system The operations include determining user rights, reviewing information submitted by users, managing, modifying, and maintaining all databases. With user management, the system will ask the user to enter a user name and password when logging in to ensure the security of the system in use and prevent commercial opponents from obtaining product or customer information.

(2) Carry out the definition of the basic parameters of sheet metal parts, process planning and selection of processing machine tools.
After obtaining the sheet metal CAD engineering drawing, the system first automatically generates the quotation number serial code, and at the same time defines the basic parameters of the sheet metal parts, such as part number, drawing number, quantity, BOM material, specifications, production plan, etc., and stores them in In the customer information database, the process flow of the sheet metal parts is planned based on the coding description of the parts through the group technology, the process route of the parts is generated according to the feature extraction technology, and the processing machine tool is selected from the machine tool database according to the production scale, power, model, etc. Types, and finally processing simulation is performed on the basis of determining various processing parameters.

(3) Estimate working hours and costs, and make working hours quota.
Extract related processing information in sheet metal CAD drawings, such as using ARX technology to extract many geometric information such as straight line segments, arcs, perimeters, etc. in AutoCAD cutting drawings, and at the same time call the information in the work-hour quota knowledge base, and consider preparing man-hours And relax the time to make a more accurate and rapid estimation of the processing man-hours of each section of the sheet metal parts. Then based on the estimated working hours, apply the activity-based costing method, first estimate the cost of the processing operation, and then estimate the cost of other operations, and generate a cost estimate report. At the same time, the estimated working hours are exchanged with the knowledge base of the working hours quota, and the sheet metal parts Carry out working hours quota.

(4) Calculate the cost price of product sales, comprehensively analyze various factors, and respond to customer inquiries.
First, analyze and summarize the manufacturing costs affected by processing hours. After considering other costs such as office expenses, financial expenses, benefits, profits, tax rates, etc., use quotation decisions to determine product characteristics, market environment, customer characteristics, competitors and other information Comprehensive analysis, relatively accurate and rapid positioning of product prices, form a quotation, send it to the customer, and import the quotation history database at the same time. If the customer is satisfied with the quoted price and other needs, the system will output a quotation after receiving the information. At this time, the company can draw up a production contract with the customer and generate an order at the same time, and then send it to the production workshop for processing and production; if the customer is not satisfied, the system The processing technology will be revised and the quotation will be re-quoted. The overall workflow of the system is shown in Figure 5-6.

5.5 System and ERP system integration
Many links in the operation of an enterprise, including market analysis, product design, processing and production, marketing tungsten, and after-sales service, are a unified and indivisible margin that requires comprehensive consideration of the overall situation. In order to achieve the goals of high quality, low cost, fast delivery and good service, the quotation system must be integrated with the enterprise ERP system. Its structure is shown in Figure 5-7. Four aspects of the interface need to be considered in the integration process:

(1) Interface with production subsystem;

(2) Interface with the design subsystem, because the product model database on which the quotation is based is the product model in product data management (PDM);

(3) Interface with customer relationship management (CRM) subsystem, CRM feedback customer information, reflecting the company's quotation strategy to customers;

(4) Interface with the main production planning subsystem, because the product BOM generated by the quotation system needs to be submitted to the production planning department, based on which the detailed production plan can be made.

The integration of the quotation system and the ERP system can ensure the validity of various data sources and the consistency of product data in the product quotation. Figure 5-7 Integration of quotation system and ERP system.