A Parametric Modeling Method for External Threads Based on the Blanking Diameter of Thread Rolling

Abstract

The present invention provides a parametric modeling method for external threads based on the diameter of the rolling blank, comprising the following steps: picking up the outer surface of the rolling blank diameter to determine the thread specification to be modeled; establishing a major diameter cylindrical model; chamfering the thread guiding position and the thread ending position; establishing an equal-diameter helix; establishing a variable-diameter helix; establishing a thread profile cutting section and sweeping along the two helices, and using the generated solid as a tool body to perform a subtraction operation with the major diameter cylindrical model; establishing a point at the end of the complete thread near the thread ending side. Advantageous effects of the present invention: Traditional modeling methods are all based on the major diameter model of the thread. The present invention is based on the blank diameter model, which can automatically identify the blank diameter size and determine the corresponding thread major diameter; the data of each thread specification is defined by the excel file in the installation directory, which is convenient for modifying and adding thread specifications.

Description

Technical Field

[0001] The present invention belongs to the technical field of thread modeling, and in particular relates to a parametric modeling method for external threads based on the diameter of the rolling blank. Background Art

[0002] Rolled thread is a cold working method that causes plastic deformation of metal to form threads. It can roll external threads of different diameters, and has the characteristics of high production efficiency, small surface roughness of the threads, high thread strength and surface hardness, etc. It can fully ensure the mechanical properties of parts and is the most widely used thread processing method in the fastener and all mechanical industries. It is very necessary to use a refined thread model for data-driven in the production process of rolled threads. However, the existing modeling software NX can only perform thread modeling on a rod with a large diameter using the thread tool function, and cannot directly model the thread based on the diameter of the rolling blank. The leading end and the trailing end of the thread are missing, and there is a large deviation from the actual thread characteristics and the actual manufacturing process of the thread. This patent invention provides a parametric modeling method for external threads based on the diameter of the rolling blank, which has relatively complete thread structure characteristics, and the thread generation process conforms to the current processing flow of rolled threads. This thread modeling method has important significance in the manufacturing and application of fasteners. Summary of the Invention

[0003] In view of this, the present invention aims to provide a parametric modeling method for external threads based on the diameter of the rolling blank, so as to automatically identify the thread specification on the basis of identifying the size of the thread blank diameter (outer diameter) and generate a thread model with leading and trailing features.

[0004] To achieve the above object, the technical solution of the present invention is realized as follows:

[0005] A parametric modeling method for external threads based on the diameter of the rolling blank, comprising the following steps:

[0006] S1. Obtain the thread blank diameter size by picking up the outer surface of the rolling blank diameter in the NX software, and determine the thread specification to be modeled by comparing with the thread standard database;

[0007] S2. In the NX software, based on the modeling parameters, the thread specification determined in step S1, and the input effective thread length, establish a large diameter cylindrical model with the thread major diameter d as the diameter on the basis of the blank diameter model, and then perform a union operation on the large diameter cylindrical model and the blank diameter model;

[0008] S3. In the NX software, chamfer the cylinder obtained by the union operation in step S2 at the thread leading position and the thread trailing position respectively to simulate the leading and trailing features of the thread;

[0009] S4. In the NX software, starting from the bottom surface of the cylinder in step S2, an equal-diameter helical curve with a height equal to the effective thread length and a diameter equal to the major diameter of the thread is established along the cylinder center line according to the input effective thread length;

[0010] S5. In the NX software, starting from the end point of the equal-diameter helical curve, a variable-diameter helical curve with a height of two pitches is established;

[0011] S6. In the NX software, according to the selected thread profile specification, a thread profile cutting section is established, and the thread profile cutting section is swept along the two helical curves. The generated solid is used as the tool body to perform a subtraction operation with the major-diameter cylinder model;

[0012] S7. In the NX software, a point is established at the end of the complete thread near the thread ending side to mark the effective thread length.

[0013] Further, the thread specifications in step S1 have four forms, namely: medium-diameter rod type, whose thread is a half thread; large-diameter rod type, whose thread is a half thread; medium-diameter rod type, whose thread is a full thread; large-diameter rod type, whose thread is a full thread.

[0014] Further, the modeling parameters in step S2 are m, n, and v respectively. The m, n, and v are all coefficients, and their values are different in different forms of thread specifications.

[0015] Further, the cylinder diameter of the major-diameter cylinder model in step S2 is d, and the length is L + v*p.

[0016] Further, in step S3, chamfers are applied to the cylinder obtained by summing in step S2 at the thread leading position and the thread ending position respectively. Specifically, the following steps are included:

[0017] S31. Chamfer the thread ending position. Among them, the axial distance between the chamfer position and the major-diameter cylinder is: 2*m*p, and the radial distance between the chamfer position and the major-diameter cylinder is: n*(d - dm) / 2;

[0018] S32. Chamfer the thread leading position. Among them, the axial distance between the chamfer position and the major-diameter cylinder is: 2*p, and the radial distance between the chamfer position and the major-diameter cylinder is: 0.75*p.

[0019] Further, the thread profile specifications in step S6 have three thread profiles, namely M thread profile, MJ thread profile, and UNJ thread profile. When establishing the thread profile cutting section for the M thread profile, MJ thread profile, and UNJ thread profile, the assigned value of the coefficient a for the three is different. Among them, for the MJ and UNJ thread profiles, a = 0.18, and for the M thread profile, a = 0.15.

[0020] Further, the tooth profile cutting section in step S6 is swept along two spiral lines, and the generated solid is used as a tool solid to perform a subtraction operation with the large-diameter cylindrical model, including the following steps:

[0021] S61. Sweep the tooth profile cutting section along an equal-diameter spiral line to generate a tool solid within the effective thread range;

[0022] S62. Sweep the end section of the tool solid within the effective thread range along a variable-diameter spiral line to generate a tool solid within the thread finishing range;

[0023] S63. Use the large-diameter cylinder as the target solid, and perform a subtraction operation with the tool solid within the effective thread range and the tool solid within the thread finishing range to generate a thread feature.

[0024] Compared with the prior art, the parametric modeling method for external threads based on the rolled thread blank diameter of the present invention has the following advantages:

[0025] For the parametric modeling method for external threads based on the rolled thread blank diameter of the present invention, traditional modeling methods are all based on the thread major diameter model for modeling. The present invention is based on the blank diameter model, which can automatically identify the blank diameter size and determine the corresponding thread major diameter; this modeling method can model the guiding and finishing features of the thread, and the established thread features conform to standards such as HB 5829-1983, GJB 52-1985 MJ, and GJB3.1; the data of each thread specification is defined by an excel file in the installation directory, which is convenient for modifying and adding thread specifications. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0027] Figure 1 is a schematic diagram of the overall method flow described in the embodiment of the present invention;

[0028] Figure 2 is a schematic diagram of the thread rolled blank diameter model described in the embodiment of the present invention;

[0029] Figure 3 is a schematic diagram of the thread major diameter modeling and chamfering described in the embodiment of the present invention;

[0030] Figure 4 is a schematic diagram of the positions of the spiral lines in the effective thread section and the finishing section spiral lines described in the embodiment of the present invention;

[0031] Figure 5 is a schematic diagram of the completed rolled thread model described in the embodiment of the present invention;

[0032] Figure 6 Schematic diagram of the parametric modeling plug-in for rolled threads according to the embodiments of the present invention. Detailed implementation manners

[0033] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0034] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be understood as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality" is two or more.

[0035] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0036] The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0037] As Figures 1 to 6 shown, a parametric modeling method for external threads based on the rolled blank diameter includes the following steps:

[0038] Step 1: By picking up the outer surface of the rolled blank diameter in the NX software (prior art), obtain the size of the thread blank diameter, and determine the thread specification to be modeled by comparing with the thread standard database.

[0039] Step 2: In the NX software, based on the determined thread specification and the input effective thread length, establish a cylindrical model with the major diameter d of the thread as the diameter on the basis of the blank diameter model, and then sum the major diameter cylindrical model and the blank diameter model through the merge command.

[0040] Step 3: In the NX software, chamfer the cylinder obtained by summing in Step 2 at the thread leading position and the finishing position respectively to simulate the leading and finishing features of the thread.

[0041] Step 4: In the NX software, according to the input effective thread length, starting from the bottom surface of the cylinder in Step 2, establish an equal-diameter helix with a height of the effective thread length and a diameter of the major thread diameter along the cylinder center line;

[0042] Step 5: In the NX software, starting from the end point of the equal-diameter helix, establish a variable-diameter helix with a height of two pitches.

[0043] Step 6: In the NX software, according to the selected thread profile specification, establish a thread profile cutting section, sweep the section along the two helices, and use the subtract command to subtract the generated body as the tool body from the existing model.

[0044] Step 7: In the NX software, establish a point at the end of the complete thread near the thread finishing side to mark the effective thread length.

[0045] Advantages and beneficial effects of the present invention:

[0046] 1) Traditional modeling methods are all based on the major thread diameter model for modeling. The present invention is based on the blank diameter model, which can automatically identify the blank diameter size and determine the corresponding major thread diameter.

[0047] 2) This modeling method can model the leading and finishing features of the thread, and the established thread features comply with standards such as HB5829-1983, GJB 52-1985MJ, and GJB3.1.

[0048] 3) The data of each thread specification is defined by the excel file in the installation directory, which is convenient for modifying and adding thread specifications.

[0049] Example 1

[0050] Step 1: By picking up the outer surface of the blank diameter in the NX software, obtain the blank diameter size (diameter), and determine the thread specification to be modeled by comparing with the thread standard database.

[0051] According to the corresponding relationship between the blank diameter and the bolt specification in the standard of "HB6387-90 MJ blank diameter before thread rolling", considering the change of the blank diameter of different materials, establish the mapping relationship between the blank diameter range and the thread specification as shown in the following table. Therefore, after obtaining the blank diameter dm transferred from the previous process, the corresponding major thread diameter d and pitch p can be automatically determined.

[0052]

[0053]

[0054] There are four forms of thread models to be established, namely: (1) medium-diameter rod type - half thread; (2) large-diameter rod type - half thread; (3) medium-diameter rod type - full thread; (4) large-diameter rod type - full thread. Different values are assigned to the coefficients m, n, and v according to the selected rod type. These coefficients are used for parameter input during modeling.

[0055] m n v Half thread of middle diameter 1 1 2 Half thread of major diameter 0.5 1 2 Full thread of middle diameter 1 1 2 Full thread of major diameter 0.001 0.001 2.5

[0056] Step 2: Based on the blank diameter model, establish a cylindrical model with a diameter of the thread major diameter d according to the effective thread length, and then sum the major-diameter cylindrical model and the blank diameter model.

[0057] The thread needs to be obtained by subtracting on the basis of the major-diameter cylinder using the modeling method of simulated cutting. Therefore, a cylinder is established at the thread starting point using the cylinder command based on the thread major diameter and pitch. The cylinder diameter is d, and the length is L + v * p.

[0058] Step 3: Chamfer the cylinder at the thread leading position and the finishing position respectively to simulate the leading and finishing features of the thread.

[0059] Chamfer the upper end of the major-diameter cylinder (thread finishing position). The chamfering method is to create an asymmetric triangular cross-section at the upper end of the major-diameter cylinder. The axial distance of the triangular cross-section (one right-angled side), that is, the axial distance of the major-diameter cylinder, is: 2 * m * p, and the radial distance of the triangular cross-section (the other right-angled side), that is, the radial distance of the major-diameter cylinder, is: n * (d - dm) / 2;

[0060] Chamfer the lower end of the major-diameter cylinder (thread leading position). The chamfering method is that the cross-section is asymmetric. The axial distance of the cross-section is: 2 * p, and the radial distance of the cross-section is: 0.75 * p.

[0061] Step 4: Establish an equal-diameter helix within the effective thread length;

[0062] Establish an internal thread line within the effective thread length. The type is "along vector", the angle is 0; the diameter is constant at d; the pitch is constant at p; the length method is "limited", the start limit is the parameter ci, and the end limit is the parameter ci + L, where ci is the position coordinate of the thread starting position along the vector direction, automatically recognized in the plugin, L is the effective thread length, input in the plugin interface; the rotation direction is right-handed.

[0063] Step 5: Establish a variable-diameter helix within the thread finishing range.

[0064] Create a variable-diameter thread line at the thread end position, with the type "along vector" and the angle 360*(ci + L) / p; the diameter law is linear, with the starting value d and the ending value d + p*v / 2; the pitch is constant at p; the length method is "limit", the starting limit is the parameter ci + L, and the ending limit is the parameter ci + L + 2*p; the rotation direction is right-handed.

[0065] Step 6: According to the thread profile specifications, create a thread profile cutting section, sweep the section along two helical lines, and use the generated solid as the tool body to perform a subtraction operation with the existing model.

[0066] Assign different values to the coefficient a according to the selected thread profile. Among them, for the MJ and UNJ thread profiles, a = 0.18, and for the M thread profile, a = 0.15.

[0067] Create a sketch and create an equilateral triangle with a side length of 0.9*p. The vertex of the triangle ( Figure 4 point A in it) is close to the blank diameter axis direction. The axial position of this vertex is aligned with the thread starting position, and the radial distance is d / 2 - 0.757771875*p; perform a fillet on the vertex, and the fillet radius is a*p.

[0068] The closed curve in the sketch (i.e., the curve with the vertex filleted) is used as the thread profile cutting section. Sweep the section along the equal-diameter helical line to generate the tool body within the effective thread range; sweep the end section of the tool body along the variable-diameter helical line to generate the tool body within the thread end range; use the large-diameter cylinder as the target body and perform a subtraction operation with the tool body and the tool body to generate the final required thread feature.

[0069] Step 7: Create a point at the end of the complete thread near the thread end side to mark the effective thread length.

[0070] The plug-in interface is as follows Figure 6 shown.

[0071] First select the "screw" option in the plug-in interface and select the outer cylindrical surface of the blank diameter. Then select the corresponding rod type and thread profile, and finally enter the effective thread length. After clicking OK, the thread with end and lead features can be automatically generated.

[0072] The present invention can automatically identify the thread specifications according to the model blank diameter size. In the production process, there is no need to repeatedly input the thread specifications, realizing automatic thread specification identification. By continuously modeling the helical lines at the effective thread position and the end thread position, the effective thread feature and the end section thread feature can be generated using the sweep method.

[0073] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A parametric modeling method for external threads based on the diameter of the rolling blank, characterized in that: It includes the following steps: S1. Obtain the thread blank diameter size by picking up the outer surface of the thread rolling blank diameter in NX software. Determine the thread specification to be modeled by comparing it with the thread standard database. S2. In NX software, based on the modeling parameters, the thread specification determined in step S1, and the input effective thread length, establish a major diameter cylinder model with a diameter of the major diameter d on the basis of the blank diameter model. Then, perform a union operation on the major diameter cylinder model and the blank diameter model. S3. In NX software, chamfer the cylinder obtained by summing in step S2 at the thread lead position and the thread end position respectively to simulate the lead and end characteristics of the thread. S4. In NX software, starting from the bottom surface of the cylinder in step S2, establish a constant-diameter helix with a height equal to the effective thread length and a diameter equal to the major diameter of the thread along the cylinder center line according to the input effective thread length. S5. In NX software, starting from the end point of the constant-diameter helix, establish a variable-diameter helix with a height equal to two pitches. S6. In NX software, establish a thread profile cutting section according to the selected thread profile specification. Sweep the thread profile cutting section along the two helices. Use the generated body as a tool body to perform a subtraction operation on the major diameter cylinder model. S7. In NX software, establish a point at the end of the complete thread near the thread end side to mark the effective thread length.

2. A parametric modeling method for external thread based on the diameter of rolling blank according to claim 1, characterized in that: The thread specifications in step S1 have four forms, namely: medium diameter rod type, with a half thread; major diameter rod type, with a half thread; medium diameter rod type, with a full thread; major diameter rod type, with a full thread.

3. A parametric modeling method for external thread based on the diameter of rolling blank according to claim 1, characterized in that: The modeling parameters in step S2 are m, n, and v respectively. Both m, n, and v are coefficients, and their values are different in different forms of thread specifications.

4. A method for parametric modeling of external thread based on the diameter of rolling blank according to claim 3, characterized in that: The cylinder diameter of the major diameter cylinder model in step S2 is d, and the length is L + v * p.

5. A parametric modeling method for external thread based on the diameter of rolling blank according to claim 3, characterized in that: In step S3, when chamfering the cylinder obtained by summing in step S2 at the thread lead position and the thread end position respectively, it specifically includes the following steps: S31. Chamfer the thread end position. Among them, the axial distance from the chamfer position to the major diameter cylinder is: 2 * m * p, and the radial distance from the chamfer position to the major diameter cylinder is: n * (d - dm) / 2. S32. Chamfer the thread lead position. Among them, the axial distance from the chamfer position to the major diameter cylinder is: 2 * p, and the radial distance from the chamfer position to the major diameter cylinder is: 0.75 * p.

6. A parametric modeling method for external thread based on the diameter of rolling blank according to claim 1, characterized in that: The thread profile specifications in step S6 have three thread profiles, namely M thread profile, MJ thread profile, and UNJ thread profile. When establishing the thread profile cutting section for the M thread profile, MJ thread profile, and UNJ thread profile, the coefficient a needs to be introduced. The values of the coefficient a for the M thread profile, MJ thread profile, and UNJ thread profile are different. Among them, a = 0.18 for the MJ and UNJ thread profiles, and a = 0.15 for the M thread profile.

7. A parametric modeling method for external thread based on the diameter of rolling blank according to claim 6, characterized in that: When the thread profile cutting section in step S6 is swept along the two helices and the generated body is used as a tool body to perform a subtraction operation on the major diameter cylinder model, it includes the following steps: S61. Sweep the thread profile cutting section along the constant-diameter helix to generate a tool body within the effective thread range. S62. Sweep the end cross-section of the tool body within the effective thread range along a variable-diameter helix to generate the tool body within the thread finishing range. S63. Use the large-diameter cylinder as the target body and perform a subtraction operation with the tool body within the effective thread range and the tool body within the thread finishing range to generate the thread feature.

Images