CN103831481B - A kind of optimization method of positive rake angle gear hob - Google Patents

Abstract

The present invention relates to the optimization method of a kind of positive rake angle gear hob, it is characterized in that: it specifically includes following steps: step 1) selects Steel material to be tungsten system high-carbon cobalt-containing super-hard type high-speed steel, and its model is W2Mo9Cr4VCo8；Step 2) according to the machined parameters of part, adjust gear hobbing equipment, increase external diameter and the aperture of hobboing cutter, select hobboing cutter chip pocket number and with hob head number without common divisor, the angle that determines reference circle radial rake；Step 3) increases hobbing cutter spade milling amount and increases hobboing cutter top relief angle；Step 4) hobboing cutter form uses positive rake angle spiral flute hob form, it is ensured that the machining condition of hobboing cutter two side edge is consistent, to reduce Forming errors；The method ensures that profile error is less than permissible value；Its positive rake angle hobboing cutter can reduce the friction on rake face of chip deformation and chip flow, such that it is able to reduce cutting force, reduces cutting temperature, improves life-span and the quality of the processed flank of tooth of hobboing cutter.Solve the 6 class precision unmanageable problems of thin-wall titanium alloy gear part.

Description

A kind of optimization method of positive rake angle gear hob

Technical field

The present invention relates to take turns hobboing cutter, the optimization method of a kind of positive rake angle gear hob.Belong to mechanical field.

Background technology

Tooth Profile Machining is the key of Gear Processing, and the principal element affecting profile accuracy is hobboing cutter precision.Owing to cutter is cut Cut bigger moment of torsion to be born and cutting force during titanium alloy, and due to during rolling cut cutter be interrupted cut, withstand shocks load, Machining condition is more severe, therefore cutter must have enough intensity and toughness；Due to titanium alloy material good toughness, add cutter in man-hour Sharp, therefore cutter material must have enough antiwear properties；Due to the poor thermal conductivity of titanium alloy, heat is concentrated mainly on cutting District, cutter must also have thermohardening.Owing to my company mainly undertakes the gear part processing of the conventional material such as 40Cr, 45 steel, Cutter for gear wheel also can only meet the processing request of conventional material.Therefore, existing general gear hob is used to be not suitable for processing Titanium alloy gear, needs design specialized hobboing cutter.

Gear hob is a kind of generating tool by helical gear theory of engagement machining cylindrical gear.In gear end cross section Profile of tooth is involute, and therefore, the basic worm of gear hob should be involute helicoid worm.When gear hob uses involute basic During worm screw, it is not straight line that the axis in its shovel face, side cuts shape, but curve, this makes manufacture and inspection hob profile the most tired Difficult.Involute helicoid worm appearance the most do not pressed by current of home make gear hob, but uses approximation appearance method to carry out design gear rolling Cutter is to replace involute hob, and the most frequently used approximation appearance method is as Archimedes' helicoid, axle using the shovel face, side of hobboing cutter It is straight line to cutting shape, manufactures and inspection is easier.But when replacing involute hob cutting with it, cause certain in theory Profile error, i.e. the molding task of profile of tooth hobboing cutter, polish hobboing cutter and standard hob are for the ease of manufacturing and measuring, the most all Use 0 ° of anterior angle.Due to this product parts precision height, thin-walled, poor rigidity, and titanium alloy material elastic modelling quantity is little, yield tensile ratio (σ S/ σ b) high, process the characteristics such as resilience, the AA level positive rake angle hobboing cutter that cutting ability is superior during design, should be used.

Production practices in recent years prove, positive rake angle hobboing cutter can reduce chip deformation and chip flow rubbing on rake face Wipe, such that it is able to reduce cutting force, reduce cutting temperature, improve life-span and the quality of the processed flank of tooth of hobboing cutter.But anterior angle is selected Selecting improper meeting makes profile error strengthen, particularly 6 class precision thin-wall titanium alloy gear parts, and required precision is high, and part thin-walled, Process yielding, simultaneously because titanium alloy belongs to unmanageable alloy material, it is ensured that the machining accuracy difficulty of part is relatively big, especially It is that tooth processed adds tool wear in man-hour soon, and working (machining) efficiency is low, and precision is difficult to reach to design requirement.Therefore, need to be to positive rake angle gear Hobboing cutter reference circle anterior angle appropriate design, it is ensured that profile error is less than permissible value.

Summary of the invention

It is an object of the invention to: provide the optimization method of a kind of positive rake angle gear hob, the method ensures that profile error is little In permissible value；Its positive rake angle hobboing cutter can reduce the friction on rake face of chip deformation and chip flow, cuts such that it is able to reduce Cut power, reduce cutting temperature, improve life-span and the quality of the processed flank of tooth of hobboing cutter.Solve 6 class precision thin-wall titanium alloy teeth The wheel unmanageable problem of part.

Technical scheme: the optimization method of a kind of positive rake angle gear hob, is characterized in that: it specifically includes as follows Step:

Step 1) selects Steel material to be tungsten system high-carbon cobalt-containing super-hard type high-speed steel, and its model is W2Mo9Cr4VCo8；

Step 2) according to the machined parameters of part, adjust gear hobbing equipment, increase external diameter and the aperture of hobboing cutter, select hobboing cutter to hold Bits groove number and with hob head number without common divisor, the angle that determines reference circle radial rake；

Step 3) increases hobbing cutter spade milling amount and increases hobboing cutter top relief angle；

Step 4) hobboing cutter form uses positive rake angle spiral flute hob form, it is ensured that the machining condition of hobboing cutter two side edge is consistent, To reduce Forming errors；

Step 5) uses Cutting-Tool Coating Technology, and after making coating, coefficient of friction and the viscosity of hobboing cutter reduce.

In described step 1) hobboing cutter external diameter be φ 63mm, chip pocket number be 16, hob head number be 3, reference circle radial rake The aperture φ 27mm of 3.5 ° of hobboing cutters of angle, in described step 3), top relief angle is 12 °；Described step 4) spiral fluted spiral side To for dextrorotation.

Advantages of the present invention: positive rake angle hobboing cutter cutting ability is superior, as long as correctly design positive rake angle and profile of tooth, can make hobboing cutter Molding task the least, fully meet the processing request of high class gear.And because the axial truncatus in shovel face, Archimedian side It is linear, radially relief grinding can be used, after refacing, still can keep profile accuracy.The present invention is improved by the design of cutter, and Use Cutting-Tool Coating Technology, solve the difficult problem that titanium alloy gear part cutting process exists, improve the durable of cutter Degree, it is ensured that the crudy of part, substantially increases production efficiency, meets the needs of batch production.

Accompanying drawing explanation

Fig. 1 is the parameters optimization calculated according to optimization method of the present invention and the hob profile schematic diagram designed；

Wherein, figure a is normal tooth profile；Figure b is axial tooth profile.

Detailed description of the invention

1, gear molding task calculates

During gear hobbing process, involute profile is mainly by keeping certain indexing to ensure between hobboing cutter and tooth base, institute With, profile error is mainly what hob profile determined.The molding task Δ f of hobboing cutter is exactly that the tooth Shape Design in path of contact direction is missed Difference, the foundation of evaluation hob profile precision is tooth Shape Design error, according to the ratio of tooth Shape Design tolerance Yu profile of tooth manufacturing tolerance (less than 1:4.5), determines tooth Shape Design tolerance.Itself AA and A level hob profile design tolerance numerical value is shown in Table 1:

Table 1AA and A level hob profile design tolerance numerical value um

The computing formula of Archimedes rear flank knife face Forming errors Δ f is:

$\mathrm{\Δ}{f}_z=\mathrm{\Δ}{f}_y=m_n\{\frac{Z_o\cos a_n}{2}({\mathrm{inva}}_y-{\mathrm{inva}}_o)-\frac{\sin a_n}{1-c_2\mathrm{tg}{\mathrm{\γ}}_o}[c_1-\frac{Z_o{c}_2\left(\mathrm{\θ}{-\mathrm{\θ}}_o\right)}{2\sin {\mathrm{\λ}}_o}\left]\right\}$

In formula: e rake face off normal value,

d_aoTip diameter；

γ_aRadial rake；

γ_oReference circle radial rake,

r_oReference radius；

θ_oValue at hobboing cutter reference circle, θ_o=-γ_o；

Value at θ hobboing cutter, $\mathrm{\θ}=\arcsin (-\frac{e}{r_y});$

r_yCalculate some radius, r_y=r_o+c₁m_n；

c₁Tooth depth coefficient, C₁Value is 1 and-1, because point is selected at the up-and-down boundary of profile of tooth active section；

r_bWorm screw base radius, $r_b=r_o\cos a_o=\frac{m_n{z}_o}{2\mathrm{tg}{\mathrm{\λ}}_b\cos {\mathrm{\λ}}_o};$

λ_bBase circle of involute helicoid worm post lead angle.Also it is the profile angle cos λ of a lateral tooth flank in basic circle incisal plane_b= cosa_ncosλ_o；

λ_oReference circle lead angle, ${\mathrm{\λ}}_o=\arcsin \left(\frac{z_o{m}_n}{2r_o}\right);$

z_oHob head number；

α_oEnd face pressure angle of graduated circle,

α_yPressure angle at any radius of involute helicoid worm end face,

K radially back-off amount, $k=\frac{\mathrm{\π}{d}_{\mathrm{ao}}}{Z_k}\cos {\mathrm{\λ}}_o\mathrm{tg}{\mathrm{\α}}_a;$

$c_2=\frac{{\mathrm{kz}}_k}{2\mathrm{\π}{r}_o};$

z_kChip pocket number；

α_aTop relief angle.

No matter hobboing cutter is spiral groove type or straight trough, and above formula is all suitable for.

2, positive rake angle gear molding task is analyzed

6 class precision titanium alloy thin wall gear part parameters are shown in Table 2:

Table 2 is by gear cutting machine parameter

The tooth Shape Design of gear hob, according to above formula calculating fraction-ness circle anterior angle and corresponding molding task, result of calculation is shown in Table 3:

Table 3 reference circle anterior angle and corresponding molding task evaluation

By the calculating of above-mentioned formula, zero anterior angle hobboing cutter, use bull can reduce designed toothform precision, but for just Anterior angle hobboing cutter, head number is the biggest, and optimal reference circle anterior angle is the biggest, selects corresponding anterior angle and head number according to different accuracy grade, can Meet the requirement of designed toothform precision.When the bigger anterior angle of needs, it is possible to increase head number.For 6 class precision titanium alloy thin wall gears The processing characteristics of part, need to design AA class precision and the superior positive rake angle hobboing cutter of cutting ability.From table 3 it can be seen that indexing Circle anterior angle γ_oBe 3.5 °, I type, head number Z_OIt is the Forming errors of 3: Δ f(+1)=-0.0394um 0.1um(AA level hob teeth Shape design tolerance numerical value), AA level hob profile design accuracy requirement, and the head number Z of hobboing cutter can be met completely_O(3) with The tooth number Z (224) of processed gear does not has common divisor, can avoid the phenomenon that processed gear tooth thickness is inconsistent, additionally, bull rolling Cutter also can significantly improve gear hobbing process efficiency.Although due to the increase of hob head number, the error of division between each bar screw thread is by shadow Ringing the precision of hobboing cutter, along with the raising of hobboing cutter manufacture level, multiple thread hob is widely used.

3, in order to ensure the machining accuracy of part, the profile error of hobboing cutter is being carried out outside appropriate design, need to be according to part Material property and required precision, the optimization method of the present invention a kind of positive rake angle gear hob, take measures as follows:

Step 1) selects Steel material to be tungsten system high-carbon cobalt-containing super-hard type high-speed steel, and its model is W2Mo9Cr4VCo8 (M42)；The Main Function of cobalt can strengthen age hardening effect, improves the hardness after thermohardening and heat treatment, and M42 has relatively simultaneously High toughness, wearability, good thermal diffusivity；

Step 2) according to the machined parameters (being shown in Table 2) of part, adjust gear hobbing equipment, increase external diameter and the aperture of hobboing cutter, from And increase the rigidity of hobboing cutter, improve cutting efficiency；Select more hobboing cutter chip pocket number and with hob head number without common divisor, determine point The angle of degree circle radial rake, the envelope error of flank of tooth when reducing cutting, reduces the cutting load of hobboing cutter monodentate, to ensure part Machining accuracy；

Step 3) increases hobbing cutter spade milling amount and increases hobboing cutter top relief angle；Make cutting edge sharp, reduce processing springback capacity And frictional force.

Step 4) hobboing cutter form uses positive rake angle spiral flute hob form, it is ensured that the machining condition of hobboing cutter two side edge is consistent, To reduce Forming errors；

Step 5) uses Cutting-Tool Coating Technology, and after making coating, coefficient of friction and the viscosity of hobboing cutter reduce；Part can be improved Processing characteristics, improves cutting wear further.And coating technology does not the most affect the dimensional accuracy of cutter, it is also possible to carry High manufacturing accuracy.Wherein, using Cutting-Tool Coating Technology is known technology.

Analyzed by gear cutting machine parameter and table 3 positive rake angle gear molding task according to table 2, calculate rolling by above-mentioned steps Parameter after cutter optimization design, the computing formula of hob profile major parameter is:

3.1, radially back-off amount k

Calculating formula for spiral flute hob radially back-off amount is:

$k=\frac{\mathrm{\π}{d}_{\mathrm{ao}}}{Z_k}\cos {\mathrm{\γ}}_z\mathrm{tg}{a}_a$

In formula: γ_zReference circle lead of screw angle,

3.2, axial tooth profile

(1) positive rake angle helicla flute Archimedes' hobbing cutter axial profile angle computing formula is:

${\mathrm{ctga}}_{\mathrm{xo}}={\mathrm{ctga}}_{\mathrm{no}}\cos {\mathrm{\γ}}_z(1-\frac{{\mathrm{kz}}_{k}e}{2\mathrm{\π}{r_o}^2\cos {\mathrm{\γ}}_o})\±\frac{{\mathrm{kz}}_k}{p_k}$

In formula, " " number is used on the left of right-hand hob, and "-" number is used for right side, and lefthand hob is the most contrary

p_kChip pocket helical pitch, p_k=π d_octgβ_k；

β_kChip pocket swing angle, β_k=γ_z

(2) axial tooth top bevel angle

3.3, normal tooth profile

(1) normal pitch P_no, P_no=π m_n

(2) normal pitch S_no,

As it is shown in figure 1, the hob profile signal that Fig. 1 is the parameters optimization calculated according to optimization method of the present invention and designs Figure；Wherein, figure a is normal tooth profile；Figure b is axial tooth profile.Parameter after optimum design of gear hob cutter is shown in Table 4: the aperture of hobboing cutter is φ 27mm

Parameter after table 4 optimum design of gear hob cutter

Positive rake angle hobboing cutter cutting ability is superior, as long as correctly design positive rake angle and profile of tooth, can make the molding task of hobboing cutter very Little, fully meet the processing request of high class gear.And it is because the axial truncatus in shovel face, Archimedian side is linear, permissible Use radially relief grinding, after refacing, still can keep profile accuracy.Improved by the design of cutter, and use Cutting-Tool Coating Technology, solve The difficult problem that titanium alloy gear part cutting process of having determined exists, improves cutting wear, it is ensured that the processing of part Quality, substantially increases production efficiency, meets the needs of batch production.

The parameters optimization of this optimization method solves the technical problem of 6 class precision thin-wall titanium alloy gear part processing, especially Being that tooth processed adds tool wear in man-hour soon, working (machining) efficiency is low, and precision is difficult to reach to design requirement.Positive rake angle hobboing cutter cutting ability is excellent More, if but anterior angle selects improper and to produce molding task excessive, can not meet the processing of high class gear.As long as correctly designing Positive rake angle and profile of tooth, the molding task that can make hobboing cutter is the least.By the appropriate design to hobboing cutter parameter, and use cutter coat skill Art, improves cutting ability and the service life of cutter, fully meets the batch machining requirement of high precision titanium alloy gear.

Claims (1)

1. an optimization method for positive rake angle gear hob, is characterized in that: it specifically includes following steps:

Step 1) selects Steel material to be tungsten system high-carbon cobalt-containing super-hard type high-speed steel, and its model is W2Mo9Cr4VCo8；

Step 2) according to the machined parameters of part, adjust gear hobbing equipment, increase external diameter and the aperture of hobboing cutter, select hobboing cutter chip pocket Number and with hob head number without common divisor, the angle that determines reference circle radial rake；

Step 3) increases hobbing cutter spade milling amount and increases hobboing cutter top relief angle；

Step 4) hobboing cutter form uses positive rake angle spiral flute hob form, it is ensured that the machining condition of hobboing cutter two side edge is consistent, to subtract Little Forming errors；

Step 5) uses Cutting-Tool Coating Technology, and after making coating, coefficient of friction and the viscosity of hobboing cutter reduce；

Described step 2) in hobboing cutter external diameter be φ 63mm, chip pocket number be 16, hob head number be 3, the angle of reference circle radial rake Spending 3.5 °, the aperture φ 27mm of hobboing cutter, in described step 3), top relief angle is 12 °；Described step 4) spiral fluted spiral side To for dextrorotation；

The method is used for thin-wall titanium alloy gear part.