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Optimizing the outer diameter of the hob The outer diameter of the hob is an important parameter of the design of the hob. The selection of the size directly affects the rationality of other structural parameters (such as the number of holes, the number of slots, etc.), the smoothness of the cutting process, and the hob. Accuracy and durability, the craftsmanship of the hob manufacturing and the surface quality of the machined gears.
In the design, the production system is used to intelligently select the outer diameter size with the highest frequency of use. The basic elements of a production system include a comprehensive database (ie, a fact base), a rule base, and an inference engine, the structure of which is shown.
The fact library in the production system structure diagram is a known condition fact, intermediate fact or final result input by the user. According to the condition of determining the outer diameter size of the gear hob, the initial facts in the dynamic database of the system are expressed as follows: Knife (modulus, accuracy level).
The rule base is divided into three parts: the first part is the rule number, the second part is the condition part, and the third part is the conclusion part. Example of rules in the rule base: rule 1: if precision level = 5or6, then outer diameter = 40 rule 2: if precision level = 7, then outer diameter = 40or32or25 rule 3: if precision level = 8, then outer diameter = 32or25 rule 4: if modulus = 10-08, then outer diameter = 25 The system uses the reasoning method of forward reasoning. When the pattern is matched, the condition part of each rule is matched with the fact in the fact library. If it is completely matched, the rule is taken out. . Due to the ambiguity of rule reasoning and the non-uniqueness of the outer diameter of the tool, the result is not unique. Since the most frequently occurring results can satisfy the most conditions, it is recommended to select the result.
At the same time, the basic principle of the production system is also applied to the surface smoothness, tolerance and material selection of the hob. The system intelligently applies existing or newly added rules and has the ability of self-learning.
The hob feature model is built by integrating the information required for hob design and manufacturing, including description of the geometry of the hob and its topological information, design information about hob materials, precision tolerances, and tool management information. At the same time, the following principle of tool division is followed: functional analysis principle: according to the function realized by the product, the product is decomposed into a set of multiple sub-component features with independent sub-functions, and then the sub-component features are decomposed into a set of meta-featured part features; Least principle: According to the characteristics of the model, considering the convenience of modeling and the speed of computer processing, the model is decomposed into as few models as possible; consistent with the CAD software modeling method: Pro/E can be used to establish the feature model.
Based on the above principles, while considering the modeling ability of Pro/E, the characteristics of the small modulus gear hob are divided as follows: (1) The default datum feature is first established. The default datum feature is the three mutually perpendicular planes produced by the system at the default position.
(2) Establish the main features of the hob. The tooth profile is the base cylinder feature, the outer diameter and the full length of the hob are determined, and other auxiliary features are established as the main feature; the axis feature is established by a user-defined feature (UDF), including the pillow block, the hole, and the inner hole. Three parts feature.
(3) Establishing an auxiliary feature in the tooth profile. Firstly use the spiral scan (HelicalSweep) in the advanced feature to establish the axial tooth shape, the axial pitch is the pitch; then use the cutting method (Cut) to cut out the chip flute, and the cutting part and the normal tooth are reflected in the sketching surface. Shape size, using the array pattern (determine the array parameters according to the number of chip pockets), a single chip pocket surrounds the base cylinder array, that is, the formation of the cutting portion, the normal tooth shape, and the chip pocket feature.
(4) Establish auxiliary features in the axis feature. Cut the hole and the inner hole using Cut, and use the chamfer to establish the abutment chamfer.
Characteristic Decomposition of Small Modulus Gear Hobs 4 Small Modulus Gear Hob Feature Model Parameterization The characteristic information of the hob is stored in the internal engineering database of the supporting software after the model is established. After parameterization, the user selects through the interactive interface. The tool to be modeled is regenerated by each part of the feature to obtain a specific model.
First, there is the Parameters option in the Pro/E drop-down menu Setup, which stores the size parameters in the hob into the parameter list, paying attention to the consistency of the parameter names. Then in the Relation option, the size of the graphic is represented as a variable parameter, and variables that are independent of the graphic size are allowed to be used as intermediate operation parameters for variable operations. The Relation option provides the basis for parameterizing the hob. Many of the parameters in the hob modeling process are set in Relation, such as hob outer diameter, slot number, aperture, and so on.
There are two kinds of traditional parametric design: one is realized by the family table in Pro/Engineer. With this feature, you can use a single reference part (GeneralPart) and a family table (FamilyTable) to represent countless similar parts. To make changes or create new parts, modify the parts list or add new data. Pro/E will automatically modify and generate the model under the driving of a single database.
Another method is implemented by the PROGRAM module in Pro/E. Each designed model has a list of main design steps and parameters in the PROGRAM module. The design list of the model can be edited to work as a program for parameterization. The input of the parameters is entered by the user through the system interface.
Due to the complex features of the small modulus gear hob and the need to define too many parameters, the above two methods may cause confusion in the operation of the user. In order to avoid the mistakes and inconvenience caused by excessive manual operation and enhance the intelligence, the system establishes the design parameters and relational formula according to the parameter function of Pro/Engineer, and develops the Pro/Toolkit application in the VC environment to retrieve the model. The design parameters are regenerated and the 3D model is regenerated according to the design parameters stored in the database. The feature is that the human-computer interaction interface is intelligent, and the user can select the modeling tool or select the tool feature to realize the parameter driving with the feature as a unit.
First, the parameter pointer is initialized, and the pointer of the parameter extracted from the database (SQLServer) is stored in the ProParameter pointer array using ProParameterInit; the structure variable of type ProParamvalue can be obtained by calling ProParametervalueGet by the pointer of each parameter. Call the function ProParametervalueSet to complete the value of the set parameter. The type of the parameter value is still the structure of ProParavalue. After the parameter is given a new value, the 3D model is updated with ProSolidRegenerate to complete the automatic creation of the hob model.
Saving the graph: The function ProMdlCopy is called to save. The name of the 3D graph automatically calls the name of the current hob model in the database.
Using feature modeling technology, the design work of the hob is not only based on the underlying geometric information, but based on the functional elements of the hob, the design work is carried out at a higher level, and the reference of the feature directly reflects the design intent, thus The problem of expression of the example is effectively solved; using the parameterized drive, the modeling problem of the multi-model small modulus gear hob is solved.
Small-module gear hob CAD system structure analysis The small-modulus gear hob CAD system is mainly composed of two parameters: tool parameter calculation and graphic parameterization. Each function module also contains corresponding sub-modules.
(1) Tool parameter calculation module The main function of this module is to intelligently select the outer diameter and basic size of the hob, and calculate the other structural dimensions of the hob with the basic element as the basic element, and select the surface finish, main tolerance and material. The object-oriented analysis method is used to analyze the hob CAD system, and the object-oriented programming language (C) is used to interpret the relationship between the object and the object.
(2) Graphic parameterization module In this module, the parameterized drive characteristics and the function of the entire tool are realized on the small modulus gear hob based on feature modeling.
Independent parameter-driven programming for each feature, and corresponding trigger mechanism.
Conclusion (1) Applying the production rule to select the outer diameter of the hob, etc., improve the selection efficiency, avoid the labor and defects caused by the user's inexperience, and retain and make full use of the precious value of the previous selection of the outer diameter of the hob. experience. (2) Using feature modeling technology to focus on the more complete expression of the technology and production organization, plan management and other multi-stage information of the small-module gear hob life cycle, and better implement the design intention of the tool to each subsequent link. Promote the development of intelligent CAD systems and intelligent manufacturing systems, and create basic conditions for the establishment of CAD/CAM/CAPP integrated systems based on unified product information models. The system applies the principle of production system and feature modeling to the design of small modulus gear hob, which improves the design efficiency and accuracy. The design idea can be extended to the design of other tools.