Research on cadcam system of the hottest gate valv

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Research on cad/cam system for gate valves

abstract it is proposed that the cad/cam system for gate valves should have the functions of optimization design, finite element analysis, parameter design, automatic drawing and computer-aided manufacturing. Therefore, the cad/cam system for gate valves is developed and designed. The system uses design calculation, analysis, dynamic drawing library, cam and other modules to meet the functional requirements, and uses the dynamic database with real-time data exchange function to connect each module together. In the design and calculation, the conceptual model of parameter driven is adopted in the design of each part, and the specific model is generated by the driving of series size parameters; In NC programming, the system provides three rough cutting methods according to the characteristics of parts. The correctness and effectiveness of NC program can be verified through three simulation forms

The application of CAD technology in all walks of life has completely changed the traditional design mode and created huge social and economic benefits. At present, CAD technology has moved from a simple drawing tool to an integrated cad/cam stage, supporting the whole process of product design and manufacturing. According to statistics, after the application of CAD technology in factory product design, the design cycle is shortened by 1/3 to 2/3, and the work efficiency is increased by 3 ~ 10 times. The one-time success rate of product design is significantly improved. The enterprise has made great progress in manufacturing technology and made a big step forward towards modern manufacturing industry. However, the vast majority of manufacturers in the petroleum industry and even the whole country have used the traditional design method of half experience and half theory for a long time. The product performance and delivery date can not meet the requirements of users, affecting the market competitiveness of products

function design

the cad/cam system for gate valves should be market-oriented and meet the needs of users. At the same time, it should make use of existing achievements and cad/cam system to realize the integration of design and manufacturing information flow, provide support for management information flow, and lay a foundation for CIMS to move towards small and medium-sized enterprises. Therefore, according to the future development trend [3], the designed cad/cam system for gate valves is an open system based on network, and should have the following three functions

1. Optimization design and finite element analysis function

the design of gate valve is a modular design based on the series model level. The design calculation contains complex contents, requires high precision and has a wide range of applications. Therefore, on the one hand, advanced scientific research achievements and new design and calculation theories at home and abroad in recent years are adopted to improve the overall performance of gate valve and realize the upgrading of gate valve products to meet the requirements of users; On the other hand, modern design methods such as optimization design and finite element analysis are used to establish an efficient and practical design and calculation module with optimization processing capacity and structural analysis

2. Parameter design and automatic drawing function

due to the change of connection form and pressure grade, the structural form of gate valve is also various. The structure changes at any time due to the different design parameters and requirements of users. In order to ensure the progressiveness and practicability of the CAD system, the module adopts the parametric structure form [4], which mainly includes the following contents:

(1) the structural design of the CAD system in order to improve the progressiveness of the product, reasonably allocate and utilize computer resources, and divide the gate valve into two processing methods: "variable" and "unchanged". The so-called "variable" refers to the parts that change with different design schemes, such as gate, valve seat and other non-standard parts. This part of the design and parameter drawing is automatically completed, and the computer automatically processes the new composite materials to make high-strength 3D models to determine the shape, size and size of the structure. The "unchanged" part refers to the corresponding standard graphics library to meet the needs of various design schemes

(2) the parameter drawing subsystem CAD system can not only automatically complete various required drawings, but also automatically determine the position and assembly relationship of each part in the general assembly drawing and automatically carry out dimensional inspection, and finally output a complete set of design drawings with a plotter. In this subsystem, the dynamic drawing library is the core, which includes more than 20 parts and components of different specifications such as series gate, valve seat and handle, so as to ensure that the general assembly of gate valve and the design and drawing of parts and components can be completed conveniently and reliably at any time

m function

cam module automatically generates the structure data and process information required by cam, automatically generates the NC machining code, man hour quota, production plan, resource demand, etc. while refining the part structure and generating the part production drawing. It also designs the simulation and development of the NC machining code, so as to simulate the actual cutting process and tool path before machining and avoid various damage conditions during machining, Realize the information integration of CAD/CAM

system structure on the other hand,

in order to meet the above three functions, the author divides the gate valve cad/cam system into five modules

1. The design calculation module

quotes the latest theories and advanced scientific research achievements in the world, and hangs an optimization design platform with more than 20 algorithms, which can shorten the original design cycle of more than 20 days to about 30 minutes

2. The analysis module

adopts the advanced Marc nonlinear finite element structure analysis theory and method of American Marc company to establish an advanced structure analysis module with pre-processing and post-processing functions

3. The dynamic graph library module

further improves the "three modernizations" of the product, develops intelligent products on the basis of the "three modernizations", and forms a dynamic graph library of gate valves based on parameter design and parameter drawing

m module

use NC code technology and NC simulation technology to study the post-processing program of NC machine tool and the automatic generation of NC code of main parts, and ensure the processing quality through the simulation of NC code

5. The dynamic database

connects each module into one, realizes the real-time transmission and transfer of information between each module, and forms a cad/cam system with each module

according to the specific product structure and requirements of the manufacturer, the structure of the gate valve cad/cam system is shown in Figure 1. The design and calculation module solves the optimization design and calculation of various parts of different specifications of gate valves. The drawing library module is divided into the standard part library including national standard parts and factory standard parts and the drawing library reflecting the characteristics of gate valves. The database module stores various design standards, is responsible for the management of design data and graphic data, and realizes real-time dynamic data exchange [5]

Figure 1 gate valve cad/cam system structure

the workflow and process information of the gate valve cad/cam system are linked as follows:

(1) use the optimization design module and finite element analysis module to carry out the design calculation and structural analysis of the overall optimization scheme of the gate valve, obtain the structural scheme and performance parameters of the gate valve, and store the design parameters in the database

(2) according to the structural parameters of the gate valve design scheme, the system automatically carries out the parametric structural design of the gate valve and its parts, and automatically draws and completes the drawing of the gate valve parts. In this process, the system automatically stores the structural parameters of each part into the database.

(3) complete the overall pre assembly of the gate valve and check the correctness.

(4) It can automatically refine the structure of various parts of the gate valve, automatically generate the production and processing drawings of various parts, and provide cam with the structure and process information of various parts

(5) according to the process instruction, the cam module takes out the structural process information of each part from the database, automatically generates the NC machining code of the part, and transmits the NC code to the NC machining center to complete the machining of the part. If necessary, the machining code of important parts can be simulated to check its correctness

parametric design of gate valve parts

gate valves are multi variety, multi specification and serialized products. Each kind of gate valve is divided into different series according to nominal pressure. There are 8 series, including 14, 21, 35, 70, 105, 140, 210 and 400MPa. Each series is divided into different models according to transmission mode, connection form and structural form; Each model is divided into different specifications according to the caliber; The drawings of each valve are more than 100 sets. Although the same type of gate valve has different series of products, and the products of the same series are divided into different models, the structure of each model is basically the same, but the specific dimensions are different. Standard parts account for a large proportion of specific models of gate valves. Take 355.6mm (14 inch) z40h-150 wedge gate valve as an example: there are 10 national standard parts, 11 factory standard parts, and 21 standard parts, accounting for about 75% of the total number of parts. Therefore, the design and drawing of gate valve products can be well completed by using the parametric modeling design method

under the Auto CAD R14 environment, a parametric design module which can be directly connected to the Auto CAD menu tree is developed with the secondary development language. It adopts the full parametric design method of part model independent of the Auto CAD interactive working environment. After the constraint relationship between model parameters is calculated, the Auto CAD function is called to complete the part design and drawing. During specific implementation, the user associates the size of the drawing with certain design conditions (or constraints), that is, the size of the drawing is regarded as a function of the design conditions. When the design conditions change, the size of the drawing will be updated accordingly. Therefore, only a small number of main parameters need to be input during operation (referring to the characteristic parameters that determine the graphics of gate valve parts, and other dimensional relationships in the drawing are indicated by these parameters), The computer automatically calculates the data of the dimensional relationship between the drawings, and automatically designs and draws the drawings. Figure 2 is an example of parameterized design of valve seat. In the figure, d0 is the main parameter, that is, the design parameter, R0 is the associated parameter, and other parameters can be calculated according to these two parameters. The designed valve seat diagram can be drawn by using the base point and control node technology

Figure 2 example of valve seat parametric design

NC programming and simulation

the system can automatically program NC and simulate machining according to the geometry, process and manufacturing information provided by part structure design and process design. During NC programming, the form of rough cutting should be selected according to the characteristics of parts. The system provides three methods: horizontal rough cutting cycle, vertical rough cutting cycle and contour rough cutting cycle. Users can select a rough cutting cycle according to the actual shape of the part. Some customized products include: thermoplastic pipe - balloon tube, 3-layer tube, multi cavity tube, woven tube, heat shrinkable tube, post-processing - tip, flaring, printing, etc; Silica gel products - precision extrusion, molding, impregnation molding, silica gel sheet and film, assembly and packaging. Then, the system asks the user to enter the file name of the NC program to be stored. The system recommends using * CNC。

when generating the NC program, the system will display the recommended rough cutting depth, feed rate and machining allowance for finish machining for the reference of the on-site operators. If the recommended value is not consistent with the actual situation on site, it can be modified, and then the part NC program that meets the requirements can be automatically generated

After the NC program is generated, machining simulation is required to verify the correctness and effectiveness of the NC program. In this system, the tool path of NC program is displayed on the workpiece to test the tool path, and the static and dynamic simulation before machining is realized. The system provides three simulation forms: static contour, static inspection (tool compensation track) and real-time dynamic

the static contour simulation requires the operator to input the interval time of trajectory drawing and the graph scale to control the speed and size of drawing; On the basis of the static contour simulation, for example, the tool movement composed of tool radius compensation and tool length compensation is considered

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