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Research on the application of PDM in cost control in product design stage

at present, there are many technologies for cost control However, there is no effective and comprehensive technology to reduce and control the cost of management products. Based on the research of cost control in collaborative product design, the author puts forward a method of using PDM to control product cost in an all-round way. Cost control is to control the specific or total cost consumption within the specified range through setting goals, systematic material and human resources, interest and debt cancellation, guidance and adjustment and other procedural links in the process of cost formation. In the highly competitive and turbulent market demand environment of modern society, the cost control in the design stage is based on the collaborative environment PDM has become an indispensable technology integration platform for collaborative product design. With product model as the core, PDM can effectively manage the information of target cost setting and decomposition, cost estimation and cost optimization in the field of cost control through product structure management, configuration management, report management and so on

1. PDM and related technology

PDM is a technology that manages all product related information and processes. PDM integrates all CAX information islands, provides a data support platform for collaborative product design, and uniformly manages various databases to ensure the unity, integrity and version correctness of data at any time. In the design stage, the cost control based on PDM can be carried out by effectively cooperating with all aspects of data, technology and personnel, so as to greatly improve the work efficiency, shorten the design cycle, and quickly and effectively complete the product development task

pdm centrally manages the product geometric information, technical information and management information generated by CAD, CAPP, cam and other systems. CAD system is mainly used for engineering design of products The product structure, part information and basic processing information determined by it are registered in the PDM system through the cad/pdm interface, and the PDM system establishes the part master record - drawing master record - engineering drawing object chain to manage it. CAPP system carries out process planning, and the management principle of PDM for its generated process, station, brief tooling and other information is similar to that of CAD information. Cam system generates process route, man hour plan, material quota, parts assembly process and related manufacturing tools

2. Export of cost related information in PDM

2.1 establish the main model of parts and components

the main model of parts and components uses some key parameters to describe the shape of parts and the relationship between sizes, including two closely related components: the geometric model of parts and components, that is, the three-dimensional model and its corresponding thing characteristic table

2.1.1 feature modeling. Feature modeling is to establish a model based on dynamic information model based on the characteristics of materials, precision, shape, technology, assembly, processing and other aspects related to parts. The expression of dynamic information is completed by CAD system. The operation process is as follows:

1) use the project management function of H Peng to decompose the task, establish the initial structure tree, and issue the task at the same time

2) according to the attachments given in the project task, the designers browse the product structure tree to find the parts node that needs to be designed, select and click "3D model design"

3) the PDM system generates corresponding XML files according to the attribute information of the part node, including part code, name, component code, component name, etc., and stores them in the installation directory of the feature modeling subsystem

4) start the feature modeling subsystem, read the contents of the XML file, and save the attribute information of the moldy parts to the database

5) open the three-dimensional model interface, design the three-dimensional chess shape of parts, and add the cost information of parts with the design of the three-dimensional model, and save the design results to the feature modeling subsystem first

6) call the "save to PDM" function, the feature modeling subsystem generates the corresponding XML file, and reads the XML file through the web service published by the PDM system According to the content given in the document, the part attribute information is stored in the PDM database

7) create the description document of the part object, and upload the 3D model of the part to the PDM file warehouse The scope of document management has undergone the change process of version control and life cycle

add cost information together with feature modeling to obtain the cost feature model of parts. Cost feature model is a set of information that uses features to describe product cost. It is composed of feature description information, model feature parameters, feature volume, processing time, unit time wage, manufacturing cost, material cost and other information

2.1.2 list of characteristics of things. The characteristics of things are a collection of information that represents the geometric characteristics, functional characteristics and manufacturing characteristics of products, components and military parts. Through these characteristics, a product, component and part can be described. The object characteristic table specifies the representation format of characteristic data, so that the characteristic data of parts can be easily exchanged between different systems, which is the basis of product modeling. The main purpose of building this table is to build a modular system that can be modified to support effective retrieval and variant design

the geometric model of parts and components is combined with the corresponding thing characteristic table to form the main model of moldy parts. After processing the main model of parts in different ways, different forms of main documents can be formed, such as part or component engineering drawings, main process planning and main procedures

2.2 Guoli product model

complete products need all kinds of information to describe, such as the geometry and structure of products need CAD models, simulation models, engineering drawings, and 18 new chemical materials in the field of high-performance fibers and composites, rare earth functional materials and new energy materials are listed in the BOM of key strategic materials; The manufacturing characteristics of products need to be described by process planning, NC procedure, inspection plan and installation instructions. The product model is the logical integration of all the above product information, which is structurally integrated by all the data of geometry, technology and management related to the product. It is the result of the product development and design process, and is completed under the control of PDM workflow management system to guide the production of physical products

product modeling based on PDM is based on product structure. Through the abstraction and extraction of product data objects, a bare class tree is formed, including product classes, data classes and relational classes. The process of product modeling is the process of reasonable hierarchical organization and extraction of product data. The established product model is composed of part master record, document master record, drawing master record and model master record. Each part is linked through the part master record. PDM establishes the relationship between the master records of various parts and components through the object identification number. The hierarchical product structure is obtained by encapsulating the hierarchical folders of the part master record, document master record and drawing master record of each component. The part master record describes the basic attributes of the part, such as the identification number, name, material, drawing number, etc. of the part, and the product structure describes the relationship between the moldy parts. Any BOM can be derived by combining the part master record with the product structure It is used to guide the manufacturing and assembly of products and their components

3. Cost control mode and Implementation Based on PDM

3. 1 cost control model based on PDM

the cost control principle in the design stage is: first, determine the selling price according to the market demand After considering the appropriate profit, determine the target cost of the product, and decompose the target cost layer by layer to the component layer, part layer and feature layer; Then, the cost of each level is estimated according to various methods and data. Finally, the estimated cost of each level is compared with its target cost, and the corresponding measures that can be taken are considered according to the comparison results to achieve the target cost

PDM based cost control is to integrate CAx and various chess building tools with PDM under the collaborative development environment to carry out information processing and information exchange and sharing, so as to realize the collaborative exchange of multiple cities and disciplines to jointly complete the cost control in the design stage

according to the above principles, the author establishes a cost control model based on PDM, as shown in Figure 1

3.2 PDM based cost control process

3.2.1 PDM is used for setting and decomposition of target cost

1) setting of target cost. Through the customer service module of the collaborative design system, customers' demands for products that cannot be naturally degraded, and the enterprise will enter the products that meet customers' needs and their geometric characteristics and performance requirements into the order management system. The enterprise determines the product war path through market analysis and actual situation, and considers the technology and information management strategies to realize the product strategy. Combined with the analysis of customers and market demand, the determined products and their geometric characteristics and performance requirements are input into the PDM system as the guidance of product cost design

the first step in setting the target cost is to determine the selling price of new products This requires enterprises to conduct a lot of technical and market analysis to determine. Technical analysis includes the technological advantages of the enterprise and the technological changes faced by the industry. Market analysis focuses on how the overall market environment will affect consumer behavior. PDM stores a large amount of historical information about all aspects of products. Relevant personnel shall extract relevant information for analysis as required

determine the total target cost of the product after considering the appropriate profit according to the price saving determined in the first step

2) decomposition of target cost. Check out the product structure that initially meets the requirements of the products to be sold in the PDM product database According to the product structure and considering appropriate changes, the total cost is decomposed into various parts to obtain the target cost of the part level and the part level According to the component attributes at each end of the product structure tree, the target cost of the part layer is decomposed to each feature through the feature cost inverse mapping, and the target cost of the feature layer is obtained. At this time, the setting and decomposition of the target cost in the first design stage are completed

3.2. The fixture is made of metal 2pdm. The product structure management module used for cost calculation

PDM manages the product structure. The cost estimation at what stage is mainly completed according to this module. Designers can consult the material price, processing cost (mainly man hour information), assembly process cost and other information in the PDM system at any time as a reference to estimate the cost of new products

for the parts and components required by the enterprise's existing production products, the cost of the parts and components can be obtained through the location search parts and components historical database. For broken design parts The geometric feature information of the parts designed by the CAD system is checked out and combined with Xing to guide the calculation of the cost of each part. The material cost is determined from two aspects: first, the technical documents provided by the engineering department provide various raw material basins (including consumption discs and normal consumption) required for manufacturing unit products ; The second is the standard unit price of each material provided by the supply department It mainly includes freight and miscellaneous expenses and purchase price. Multiply the standard consumption of various raw materials by their standard unit price to obtain the cost of product standard materials. The parts on each side are processed from blanks, and the geometric characteristics of the blanks used to process different parts are different. Take giant shaft parts as an example If the part is added, it indicates that it produces a partial bar blank If the square handle of the blank sub category under the material holding blank category is used for processing, the rectangular material with a cube bottom shall be used according to the diameter and shaft length of the circular section of the circular shaft parts. At this time, the gross weight of a single piece is calculated by the bottom edge length x Height x the specific gravity of the material. The order of a single piece of material is obtained after the gross weight of a single piece x the consumption coefficient, and the cost of the part can be obtained after considering the unit cost. Generally speaking, the consumption coefficient is determined by the enterprise based on historical experience or

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