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(2) The axial pitch of the worm wheel, if the axial modulus (ie the worm wheel end modulus) is taken as the standard, on the general lathe, the modulus can be used to drive out, which is now changed to the normal modulus, the worm The axial pitch is replaced by a suitable amount of cutting that is already available on the lathe, or by the method of preparing the hanging wheel.
2 Design calculation 21 unrestricted center distance This situation is used for the newly designed worm drive, the center distance is determined by the designer. The design steps are as follows: (1) Find a suitable worm axial pitch Pa1 on the lathe and calculate the helix angle.
Cos=Tn/Ta=mn/Pa1(1) where: mn is the normal modulus of the gear hob; Ta is the initial amount of the cutter, that is, the axis guide of the worm; Tn is the guide course; Pa1 is The axial pitch of the worm; if the value is too large or too small, it is not required, and Ta can be selected. To increase the helix angle, select a larger Ta; if you want to reduce the helix angle, change the smaller Ta.
(2) Calculate the end face modulus of the worm gear (ie the axial modulus of the worm) msms=mn/cos(2) The end face modulus ms must be at least four to five digits after the decimal point to avoid excessive calculation of the center distance and tooth thickness error. .
(3) Calculate the diameter of the worm index circle d1tan=a/d1=Z1Pa1/d1 where Pa1 and Z1 are fixed values, so the value of d1 cannot be arbitrary, and it should be calculated by the above formula, ie d1=Z1Pa1/tan
(4) Calculate the diameter of the worm wheel index circle d2d2 = msZ2 (4) The calculation of the diameter size is at least three decimal places, so as to avoid excessive calculation error of the center distance.
(5) Calculate the center distance of the worm drive a0=(d1/2) (d2/2) (5) The center distance on the box is machined according to this size. As for other sizes, the calculations for the same general worm drive are the same.
It should be pointed out that the worm gear meshed with the multi-head worm by a single-head gear hob has a large tooth shape error. When engaging with the working worm, only the middle portion can contact each other. The more the number of working worms, the contact The smaller the area. However, it does not affect the correct meshing drive, and only has a certain impact on the service life and load carrying capacity of the worm drive.
When machining, the tool should be moved at an angle, the value should be equal to the spiral angle of the multi-head worm minus the spiral angle of the single-head hob. Note that the worm and worm gear should be in the same direction of rotation.
22 The central distance is limited. This situation mainly refers to repairing the old worm drive or using the old one. The design method is the same as before. Since the center distance has been determined, when the worm gear is machined with a gear hob, the spiral angle of the original worm drive, the diameter of the worm and the worm wheel must be changed, and the displacement worm drive is used to match the center distance, but the displacement coefficient cannot be too large. Or too small, otherwise re-select Ta for calculation.
3 application examples are provided with a worm drive, the main parameters are Z1=3, Z2=40, q=11, ms=4mm, a=102mm, d1=44mm, d2=160mm,=1518, now damaged, ready to adopt mn = 4mm gear hob machining worm gear, try to determine the main parameters and dimensions.
4 Conclusion When there is no worm gear hob, the gear hobbing machine is used to machine the worm gear. This is an economical and time-saving method for single-piece small-volume worm drive or repairing the old worm drive. The worm drive manufactured by this method can fully meet the requirements of general design. However, for important worm drives (especially heavy loads) and mass-produced worm drives, special worm gear hobs must be designed.
Calculation of manufacturing worm gear by using gear blade
1 Design principle (1) The end mold is the standard, and the gear hob is based on the normal modulus. Therefore, the other dimensions of the worm drive should be calculated based on the standard normal modulus of the gear hob.