New type of software is applied in the data integration of open-type cylindrical gears


1InventorAPI secondary development technology 1.1InventorAPI development features The technical foundation of InventorAPI is Microsoft's automation technology. This kind of automation interface is the same in the application under the Windows platform. Users can access Inventor's various objects and related properties and methods through the InventorAPI in a high-level language that supports Automation (OLEAutomation) technology for secondary development.
Compared with other three-dimensional modeling software secondary development technology, the significant advantage of InventorAPI technology is that it can be written in almost any popular programming language, such as VBA, VB, VC, Delphi, Perl and Java. At the same time, because the functionality of the application is exposed in an object-oriented way, once the general concepts of object-oriented programming are understood and mastered (for example, an object-oriented API works), this API is easier to learn than a process-oriented API. use. The object hierarchy model of InventorAPI is shown in Figure 1.
This model exposes the various functions of Inventor and the associations and inheritance relationships between objects, from which you can find access to any one object.
1.2 Development Method Comparison InventorAPI provides three development methods: Add-in, Standalone EXE, and ApprenticeServer.
Plugins can be loaded automatically, which is a very useful feature for programs, so most applications that integrate seamlessly with Inventor need to be plug-in. The plugin can choose to generate the DLL when it is generated, so it runs in the same processing space of Inventor, and it runs efficiently. It can also choose to generate EXE type plugin. The main advantage is that debugging is convenient.
Stand-alone EXEs run in a processing space outside of Inventor, have their own program interface and do not require users to interact with Inventor.
Apprentice servers are essentially a subset of Inventor, without their own user interface, primarily providing access to Inventor document information for other applications.
1.3 Developing Key Technologies InventorVBA is a specific development tool provided by Microsoft and integrated into Inventor. On the one hand it is common to VBA and can be customized to meet the requirements of a particular program.
By customizing, you can embed a program into an Inventor file to bind the program to the data; you can also store the program as independent. An IVB file that allows other users to share the file.
InventorAPI exposes Inventor's internal objects in an object-oriented way, so development involves two main processes: the declaration of an object and the assignment of an object instance. The format of the object declaration is: Dim object variable name As object name; the format of the object instance assignment is: Set object instance = .... For example: Declare the Inventor sketch arc object variable: DimoArcAsSketchArc draws an arc in the sketch environment. The center of the arc is (0,0), the starting point is (10,0), the ending point is (0,10), and the drawing direction is counterclockwise (such as clockwise, the last parameter should be changed to False): SetoArc=oSketch .SketchArcs.AddByCenterStartEndPoint(oTransGeom.CreatePoint2d(0,0),oTransGeom.
CreatePoint2d(10,0), oTransGeom.CreatePoint2d(0,10), True)
2 Involute standard gear parametric modeling program implementation Although the involute profile and related solid modeling are not necessary in the design process, it is necessary for the mechanism demonstration and the lower CNC machining. Gear design parameters can also be appropriately simplified under this demand. In this paper, the tooth profile correction parameters such as the height displacement coefficient, the angular displacement coefficient, and the tooth thickness thinning amount are not considered.
2.1 Basic parameters and expression of the tooth profile According to the standard gear design rules, there is a reference map for the calculation of the groove profile as shown in 2.
The following basic parameters are used in the calculation process: Pi (pi): not directly provided in Inventor, the more accurate value can be taken as Pi=4 Atn(1); the pressure angle Gylj: 0.34906585 radians (20 degree radians); the number of teeth Gz : given (integer); modulus Gm = 0.1Gm (InventorAPI uses centimeter as the unit of length, and creates grass like millimeter, here directly preprocesses the modulus involving length); index circle radius Gfr=0.5 Gz Gm; base circle radius Gjr=Gfr Cos(Gylj);
2.2 The creation of the involute part of the tooth profile does not provide the function of establishing a curve according to the equation in Inventor. Therefore, the process of creating the involute part is: first calculate the control point on the involute according to the previous formula, and then store it in the array. Finally, the involute curve is approximated by creating a spline curve.
According to the figure, the coordinates of a point on the involute:
XP=rPCos(wp)YP=rPSin(wp) where:rP=the radius at which the point is calculated (mm)wP=(Pi-4tg(Gylj))/(2Gz) ((invGax)-(invGylja)) Calculate the point angle Where: Inv(a)=sin(a)/cos(a)aGax=arcCos(rP/Gjr)
2.3 Some details of the involute creation Because two involute objects are created and referenced later, all the data structures are two sets, each set can fully stabilize the involute according to 10 control points. Shape and meet the accuracy requirements. All control points are calculated from the individual radii calculated from the radius of the starting point of the involute to the radius of the end point.
In addition, under different parameters, the starting point of the involute has two possibilities: when the (base circle - tooth root arc) result is larger than the root circle, the involute start point is on the base circle; when (base circle - tooth root) The result of the arc is smaller than the root circle, and the starting point of the involute is on the root circle. The end of the involute always ends on the crest circle.
2.4 Graph processing of the root portion In the reference map of the 2-toothed groove calculation, P1-P3 is the involute portion, and P3-P4 is a straight line, which is the transition between the involute and the root structure. There are two cases in the P3-P4 part:
(1) When the base circle is larger than the root circle, the transition arc is a single arc, which is a portion below the intermeshing limit engagement point and an arc tangent to the root circle tangent, and the radius Gr is determined; (2) When the base circle + transition arc radius still does not reach the root circle, the straight line transition portion P2-P3 is added, which is tangent to the transition arc and the root circle, and the oblique line angle Ga is determined by 1.
In fact, the tooth groove coefficient Gk determines the radius Gr of the root radius and the straight line angle Ga. According to the relationship between the basic parameters of each gear, Gk is calculated from the displacement coefficient f (here constant 0) and the number of teeth Gz. Out: Gk=f+0.03Gz, which is Gz=0.03Gz.
2.5 Modeling Results Verification According to the above principle, the VBA programming environment is applied, and the three-dimensional parametric modeling program of the involute spur gear in the Inventor environment is realized by calling the InventorAPI function. It is the application of the method to obtain the tooth number meshing relationship diagram. It can be seen that although the tooth profile portion is simplified, the accuracy is still high.
3 Conclusions Using the above principle to realize the three-dimensional parametric modeling of the involute gear, the parametric design of the standard involute gear with different tooth number z and modulus m can be easily realized, eliminating a lot of repetitive work and realizing the secondary development of InventorAPI. . Applying this method for gear modeling not only meets the requirements of the demonstration, but also provides the necessary optimization, and can also serve the dynamic simulation, interference inspection, finite element analysis and NC machining of the subsequent gear mechanism in the case of low requirements.

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