Through the introduction of typical examples, SolidWorks is used to realize the three-dimensional modeling process of spiral surface machine parts, and concrete solutions to some gradual changes of helicoidal surface are proposed.
1 Spiral Mechanical Parts Modeling Analysis
The helical part of the cylindrical spiral surface mechanical part consists of a spiral body and a spiral groove, and is cut by a plane passing through the axis of the spiral surface mechanical component, and the spiral entity and the spiral groove respectively obtain its cross section. The cross section outline is called "axis cross section outline". . The section of the spiral body and the spiral groove can be obtained by cutting the plane perpendicular to the axis of the spiral mechanical component, and the profile of the cross section is called the “draw profileâ€.
The spiral solid part of the spiral surface mechanical part can be considered as the trajectory of the spiral scan along the axis section or the vertical section of the spiral entity. The spiral groove can also be considered as the trajectory of the spiral groove axial section or the vertical section scanned along the spiral line.
SolidWurks is feature-based 3D software. Its modeling features are based on the outline of the graphics. In the process of generating spiral features, it is necessary to set some elements of the spiral and the outline of the scan section and the generation method. The elements of the helix include the definition (pitch and number of turns, height and number of turns, height and pitch), direction of rotation (left-handed, right-handed), direction of generation, and it is also possible to generate a conical, equal-pitch helix. There are two types of cross-sectional profiles, namely the axial section profile and the vertical section profile. Generating methods include 2 kinds, scanning stretching and scanning resection.
By using the scanning features in SolidWorks, according to the characteristics of the spiral surface mechanical parts, reasonable settings, you can generate the required three-dimensional solid model.
2 Method of Modeling Spiral Mechanical Parts
Through concrete spiral mechanical parts, the method of modeling using the scanning features in SolidWorks was described.
2.1 Three-dimensional modeling of threaded parts
Figure 1 shows the pattern of an ordinary thread. The axial section of the thread part is shown in the partial sectional view of Figure 1. It is an equilateral triangle cut off the top (the actual situation is that the top of the equilateral triangle is rounded, mainly due to tool wear). It becomes a trapezoid. The profile of the vertical section is more complex, so the axis section profile should be used as the profile of the scanning section, and the spiral is used as the scan path for scanning and stretching (scanning and cutting) to generate the thread feature.
The main operation steps of the scanning and stretching with the axial section profile as the scanning profile (taking M=20·2.5) are taken as examples.
(1) Using a tensile feature command, generate a cylindrical substrate whose diameter is equal to the thread diameter d1=17.294 mm, h=30 mm;
(2) The helical pitch P = 2.5 mm is generated on the cylindrical surface, and the spiral diameter is 17.294 mm;
(3) The profile of the axial section of the thread made on a plane passing through the axis requires that the section of the thread axis (the long base of the trapezoid) be coincident with the intersection of the cylinder with the plane where the section of the axis lies;
(4) Using the scan-compression feature command, the profile of the threaded shaft is used as the scan profile, and the spiral is used as the scan path to generate three-dimensional modeling of the thread.
The use of scan cuts to generate, the main steps are as follows:
1 Use a stretching feature command to generate a cylindrical body with D = 20 mm, h = 30 mm; 2 Create a spiral with a pitch of p = 2.5 mm on the cylinder with a spiral diameter of 17.294 mm; 3 Make a plane through the axis The profile of the axial section of the thread groove requires that the axial section of the groove (the long base of the trapezoid) be coincident with the intersection of the axis of the cylinder and the plane where the section of the shaft intersects; 4 the scanning cut feature command is used, and the thread groove section profile is the scanning profile. The spiral is a scan path, generating a three-dimensional model of the thread.
The above two methods produce the same result. However, some structures, such as screw tails of threaded parts, groove tails of twist drills, and retraction parts of shaft gears, etc., are shallowly tapered. When generating the tail, you need to change the way the spiral is generated.
General screw with screw tail (take M=20·2.5 as an example, when P=2.5 mm, finish x=6.3). The modeling steps are as follows:
(1) Generate a cylindrical matrix with D = 20 mm, h = 40rnrn using the Extrude feature command; (2) Create a spiral with a pitch of P = 2.5 mm on the cylinder with a spiral diameter of 17.294. ;3 generates a conical helix at the end of the helix (taper extension, a = 12.10, p = 2.5 mm, h = 6.3 mm), the starting diameter of the cone spiral d two 17.294InIn, starting angle and the former spiral The end angle of the line is the same, and the rest of the parameters are the same. Use the combined curve tool to merge the two spiral lines into a new spiral combination curve. 4 The axial section profile of the thread groove is made on a plane passing through the axis, and the axial section profile of the groove is required. (long trapezoidal base) and the line of intersection of the cylinder and the plane where the shaft section lies; 5 using the method of scanning and cutting to generate the thread and the tail of the thread, the axis profile of the thread groove is the scanning profile, and the spiral combination curve is used as the scanning path. Generate three-dimensional modeling of threads (see Figure 2).
With 2 scans, the steps are as follows:
1 Thread part is generated, as described above; 2 The spiral helix is ​​generated at the end of the helix. As mentioned above, the starting angle of this cone spiral is required to be the same as the ending angle of the preceding helix; The medium transformation entity reference tool converts the groove shape of the thread groove into a sketch, and the sketch is a scanning contour. The taper spiral is a scanning path, and a trailing portion of the thread is generated by the command of the sweeping cut feature.
2.2 Cylindrical Shaking Gear Blowing 3D Modeling
Taking an involute helical gear as an example (see Figure 3), the tooth surface of the gear is helical. The tooth profile of the helical gear is involute, and the end face tooth profile can be used to calculate the corresponding parameters by the relevant calculation formula of the helical gear. However, the axial cross-section profile is difficult to draw, so the face profile is used as the profile profile. There are three methods for three-dimensional modeling: 1 Make a cylindrical base of the gear (diameter is the diameter of the root circle), then scan and stretch with a tooth profile, and then perform the array; 2 Make a cylindrical base of the gear (diameter is the diameter of the addendum circle) ), and then use a slot to scan and cut, and then perform the array; 3 to make the end face profile, and then scan and stretch. The third kind of hair is better.
Face modeling, scanning the three-dimensional model of the cylindrical helical gear, the main steps are as follows (example: helical gear parameters mn = 2 mm, z = 25, han* = 1, cn* = 0.25, αn = 20°, β = 15°:
(1) Calculate the pitch circle diameter d = zmn/cos β = 51.7638mm according to the given normal modulus mn, tooth number z, helix angle β, pressure angle αn, and the helix pitch P = πd/tanβ = 606.909mm.
(2) As a spiral, helical pitch P = 606.909 mm, helix diameter d = 51.7638 mm, introduction of the end profile profile (this step is explained below);
(3) With the scan and stretch feature command, the end face profile is used as the scanning section, and the spiral line is used as the scan path to generate a three-dimensional model. Then, the axis hole and the keyway are generated by the stretched cutting feature command.
For the shaft gear with the retracting structure, the groove of the retracting part gradually becomes shallow, and the three-dimensional modeling of the retracting groove can be accomplished by the same method of generating the threaded thread tail. The main steps are as follows (example: mn=2 mm, z=10, han*=1, cn*=0.25, αn=20°, β=20°):
(1) Calculate the diameter of the index circle d=zmn/cosβ=21.284 mm according to the given parameters of the surface modulus mn, the number of teeth z, the helix angle β, the pressure angle an, and the lead of the helix P=πd/tan β =183.712 two, the diameter of the addendum circle da = d + 2mnhmn * = = 25.284, using a stretch feature command to generate a cylinder with a diameter of 25.284 mm;
(2) Guide the vertical cross-section of a single shaft gear groove on the bottom surface of the cylinder and generate a spiral with a pitch of 183.712 mm and a helical diameter of 21.284 mm on the underside of the cylinder. The helix scans and removes the path;
(3) At the end of the helix, a conical helix is ​​generated (tapering outside angle a=15°). The remaining parameters are the same as the previous helix. The starting angle is the same as the ending angle of the preceding helix.
(4) Use the transformation entity reference tool in sketching to convert the slot end slot shape into a sketch, and use this sketch as the outline of the scanning resection, and use the taper spiral as the path for scanning and resection to obtain the tail of the shaft gear. Knife section
(5) The array of cogging and retracting parts, you can get the required three-dimensional shaft gear modeling (see Figure 4).
You can also use the combined curve tool to combine 2 spirals into 1 curve for scanning and resection.
3 Call CAXA to draw tooth profile graphics
CAXA electronic drawing board is a CAD software system that is currently copyrighted in China. It is easy to learn, easy to operate, supports a variety of standard data interfaces, and can easily exchange files with AutoCAD. The steps for adjusting the tooth profile are as follows:
(1) Generate a complete face profile (or a single tooth profile) in CAXA using the commands generated by the gear, and then output this image in the "*.dwg" format;
(2) In the SolidWorks implementation of the "open" command, in the dialog box that appears, select "*. Dwg", and then open the "*.dwg" file CAXA output, input to the part, in the input data unit Select "mm". This complete end profile map is completed.
4 Conclusion
Through examples, using the SolidWorks feature modeling function, the three-dimensional model of spiral surface mechanical parts was quickly drawn, and feasible processing techniques were proposed for the gradual parts of the spiral surface, providing technical support for the establishment of a three-dimensional mechanical standard parts library. Practical value.
The key to drawing helicoids with SolidWorks is to choose a good contour. According to the characteristics of the part, it is necessary to determine whether to use a vertical section profile or an axial section profile to make the outline drawing of the drawn section as simple as possible. This not only facilitates drawing, but also provides techniques for parametric design. reference.