The teeth shape error that angrily of hard tooth flank processes is analysed

Time:2023-06-15 13:10:06
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source:ASEM CNC Machining

Summary: The main error element to precision of tooth form of the influence in gear cutting of hard tooth flank (include cutting tool to make error of motion of machine tool of sum of errors) had theoretical analysis and consideration, put forward to reduce the relevant measure of teeth shape error. The theoretical calculation formula of 1 teeth shape error is in when columnar to involute of hard tooth flank gear undertakes angrily is machined, the main source of teeth shape error can divide the sum of errors that causes for gear cutting tool to process the error that the machine tool causes, namely teeth shape error can express to be Dff=[(Df cutting tool) 2+(Df machine tool) 2]½ among them, the error Df cutting tool that gear cutting tool causes includes cutting tool again Dfa0 of error of horn of primitive tooth form, before installation of cutting tool of Df of mounting error of knife of DfS of error of corkscrewed yarn of knife of Dft of error of pitch of axial of Dfg of error of sex of radial of knife face blame, hob, edge, cutting tool; Flexibility of motion of Df of error of machine tool motion, machine tool is included to be out of shape error Df is out of shape again in machining the error Df machine tool that the machine tool causes, installation of workpiece of Df of workpiece mounting error. Accordingly, rise to be machined to age the main measure of precision of form of teeth of a cogwheel is to raise cutting tool to make precision; 2 it is to raise precision of machine tool motion (especially) of workbench circumgyrate precision. Pursue 1 before blade face pursues for the horn of primitive tooth form of 0 ° 2 before blade face is - the horn of primitive tooth form of 30 ° pursues appearance of 3 razor blade pursues 4 workpiece teeth shape error pursues workbench of 5 machine tools turns round graph of oscillatory error computation the teeth shape error that production error of 2 cutting tool causes is used at processing oil. Hard tooth flank rolls razor before blade face is - 30 ° (standard hob is 0 ° ) , age number is hob of standard of 30 ～ 40(to be 10) about about, accordingly, the side edge that hard tooth flank rolls razor cannot be shovelled grind, use diamond to emery wheel grinds law grinding by helicoid and be become normally, be in in order to make sure every edge all distributings the basic worm of cutting tool apparently. In project of production error of a lot of cutting tool, dfa0 of error of horn of primitive tooth form and knife of DfS of error of edge corkscrewed yarn are controlled the hardest, analyse as follows respectively: A0 of horn of primitive tooth form of Dfa0 of error of horn of primitive tooth form is a basis principle of cutting tool modelling is calculated accurately and get, to before the hob that blade face is 0 ° , its are primitive tooth form horn is worth A0 surely for two left, A0 is right (1) seeing a picture. Hard tooth flank rolls razor before blade face is - 30 ° , it and basic worm surface intersect the blade body that make is one curve, the part of primitive tooth form that orders each on the curve each are not identical (2) seeing a picture. When making hard tooth flank roll razor, above all bit beforehand wear is straight, leave at the same time piece from the back (3a seeing a picture, D) , next form of wear of essence of life (3b seeing a picture, C) . First flank of the razor blade after figuration turns into by F F, than original broaden severalfold. Because blade grinds surplus not all, the razor blade after essence of life is ground will produce teeth shape error, create bit tooth form mid cut too, the work that because this uses this kind of hard tooth flank,rolls razor treatment is real tooth form is mid it is more raised (4) seeing a picture. Hard tooth flank of knife of DfS of error of edge corkscrewed yarn rolls razor to use solder type construction. The position of each razor blade after soldering should happen fluctuant, the mental allowance when causing essence of life to grind not all, assure the treatment precision of the requirement not easily. In addition, the linearity that essence of life grinds the place when rolling razor to use diamond emery wheel is poorer (about 0.

015mm) also is one of main reasons that cause cutting tool to make an error. The place on put together is narrated, make an error by cutting tool (determine error value is made an appointment with 0.

015 ～ 0.

The workpiece teeth shape error that 020mm) causes is: =0 of Df cutting tool.

015 ～ 0.

020mm. The teeth shape error that error of motion of 3 machine tools causes is in gear cutting of hard tooth flank, the athletic error that processes a machine tool is bigger to the influence of teeth shape error of workpiece. Undertake detecting through cutting the work after to trying, the teeth shape error that discovers gear cutting of hard tooth flank and photograph of common gear cutting are older than wave motion, show rolling cut of hard tooth flank machines precision quite sensitive to gear hardness, the dynamic character that processes a system has conclusive effect to teeth shape error. In error of machine tool motion, before affecting the biggest is machine tool workbench to turn round machine tool of oscillatory sum of errors to teeth shape error, rear column is in the displacement error of gear radial direction. Of the workbench of machine tool of gear cutting of teeth shape error that machine tool workbench turns round vibration to cause turn round oscillatory will immediate impact to be machined the teeth shape error of gear. This error is undertake detecting on the tangent direction of gear, its computation graph sees a picture 5. Workpiece of the R in the graph is by treatment gear diameter, =[(Dfs)2+(DS1)2]½=[(0 of DaDf machine tool.

014)2+(0.

032)2]½=0.

The workpiece teeth shape error that 035mm causes by error of motion of machine tool of cutting tool production sum of errors is Dff=[(Df cutting tool) 2+(Df machine tool) 2]½=(0.

0202+0.

0352)½=0.

041mm pursues before 6 machine tools, rear column is in of gear radial direction be out of shape pursue structure of chamfer of fixed position of 7 razor blade pursues 8 be pursued by Dao Wen appearance of treatment tooth flank axis of 9 gear installation uses in cutting master piece turn round angle 4 reduce, must raise hard tooth flank to roll the production precision of razor, for this, can take the following step: ① raises the prefab precision of bit semifinished product; The structure that ② takes bit instead fixed position chamfer (7) seeing a picture; ③ computation gives edge curve, before opening those who give edge by approximate curve, hind knife face. In reducing rolling cut of hard tooth flank of error of machine tool motion to machine condition judgement to machine a process in rolling cut of hard tooth flank, if machine a machine tool athletic error is too big, can affect the on the rails of cutting badly. It is normal to can pass observation to be judged cutting by grain of knife of treatment tooth flank commonly. If Dao Wen is orderly and successive (8a) seeing a picture, show cutting is normal; Show when the concealed when be like Dao Wen and have crowded scratch mark (8b) seeing a picture, show cutting of partial the crucial point is abnormal; If disorder or grain of tooth flank knife is essential,lose sight of Dao Wen, show cutting is abnormal. The dynamic error in the process of treatment of rolling cut of computational hard tooth flank of error of system of machine tool campaign basically behaves those who be a machine tool to twist brace up reach corresponding bearing be out of shape. When using gear of rolling cut of hard alloy cutting tool, treatment moves the feed span of qualitative tine to be F=0 commonly.

1 ～ 0.

2mm/r, span is corresponding cutting force 15 ～ 22kg. And when treatment hardness is more than the oil hard gear of 60HRC, corresponding at F=0.

The cutting force of 1mm/r is 150kg; Corresponding at F=0.

The cutting force of 2mm/r can amount to 200kg. Feed of rolling cut of general hard tooth flank is F=0.

2 ～ 0.

4mm/r, because this can press the cutting force computer of 200kg of the bed twist brace up quantity and the bearing that cause be out of shape. Cutting force causes twist brace up the quantity is shown 9 times like the graph, gear installation axis is met below action of cutting force F(F=200kg) generation turns round angle Y, its computation formula is Ymax=(Mnmax/GIp)(180 ° / in P) type: Mnmax -- place of gear installation axis suffers the biggest torque, mnmax=Fd/2=1.

Mm G of · of 725 × 105N -- cut stretch model amount, take G=79.

4GPa Ip -- of gear installation axis extremely quadrature of be used to, ip=pd04/32=1.

27 × 106mm4 D -- gear diameter, d=176.

25mm pursues axis of 10 gear installation suffers force model D0 -- diameter of gear installation axis, d0=60mm generation can get Ymax=0 into parameter.

98 ° / M, what axial 150mm is in is install to turn round horny Ymax=0 in gear.

15 ° . From this calculable the gear installation axis that gives cutting force to cause is twisted brace up quantity DS=d/2tanYmax=176.

25/2tan0.

15 ° =0.

23mm. By computation the result is knowable, below action of cutting force F, gear installs an axis (of Ø60mm) reverse part (Ymax=0.

15 ° ) bigger, caused error of bigger system of machine tool campaign from this. To solve this one problem, those who install a Ø120mm can be add to cover on gear installation axis, turn round horny Ymax=0 by what this computation gets.

0098 ° , can reduce error of system of machine tool campaign greatly. The gear installation axis that cutting force causes bends be out of shape cutting force F conversion is action the active force P at gear radial, p=F/tan β , take ° of =20 of β of tooth form horn, criterion P=200/tan20 ° =550kg. When the radial deflection that computational gear issues in P=550kg action is measured, gear installation axis state getting power simplifies for the graph 10 show a model, in can begging those who give gear to install an axis to curve deflection to be Yc=Yc1-Yc2 type accordingly: Yc1 -- the deflection that active force P causes in C dot, yc1=Pa3/3EI Yc2 -- the deflection that raises the PB that return power to be caused in C dot, yc2=PBa2(3L-a)/6EI I -- quadrature of sectional be used to, i=pd4/64 E -- stretch model quantity of the axis, e=206GPa L -- total length of the axis, l=660mm A -- cutting master piece uses bit of C to the distance that secures upright A, a=380mm D -- axial diameter, d=60mm PB -- B nods return power, PB=Pa2(3L-a)/2L3=221kg pursues 11 rear column suffer force model to join each numeric generation to enter type in, calculable the gear installation axis that gives cutting force to cause curves deflection Yc=0.

117mm. The rear column that cutting force causes curves those who be out of shape rear column is caused below cutting strength effect to curve deflection to be able to press a plan 11 show model getting power to have consideration, namely in YB=PBa3/3EI type: PB -- B nods return power, PB=221kg A -- the distance that fixed end goes to between pedestal aperture, a=660mm E -- the stretch model quantity of pillar, e=135GPa I -- the quadrature of sectional be used to of pillar, i=(BH3-bh3)/12=9.

7 × 108mm4 B, h -- pillar is sectional dimension, b=550mm, h=335mm T -- the wall of pillar is large, t=32mm B=B-2t=550-2 × 32=486mm, 32=271mm will join H=H-2t=335-2 × each in counting value generation to enter type, calculable the rear column that gives cutting force to cause curves deflection YB=0.

0016mm. Calculate by afore-mentioned analysises knowable, the gear that machines a machine tool installs axis and pillar stiffness to have bigger effect to gear cutting precision. Accordingly, be machined to be reduced effectively the teeth shape error of gear, must raise gear to install the stiffness of axis and pillar, avoid as far as possible or reduce system of machine tool campaign to be in what arise below cutting strength effect to twist brace up reach bearing the position changes. After using hard alloy to roll razor to age face of teeth of a cogwheel undertakes semifinishing machining forcedly to temper by dipping in water, still need to undertake essence of life grinds treatment, in order to assure gear cutting precision. Pass pair of machining complex (machine tool, clamping apparatus, cutting tool, workpiece) undertake accurate installation and debug, can make sure the treatment of hard tooth flank of temper by dipping in water asks. CNC Milling