Spur bevel gear is mainly used for transmission of two axis, the Angle between the two axis usually is 90 °, can also be less than 90 °. Bevel gear is in commonly cone gear shaver on special machine tool processing, such as in the case of lack of special bevel gear machine tool, can use bevel gear cutter in milling machine processing, it USES is forming cutters and dividing device on the milling machine for processing. Because of dividing and cutting tool installation errors, normally only the 9 ~ 10 machining precision of gear. In addition, to do multiple discrete points in the manufacturing process of tooth, productivity is low, only for single piece and small batch production and replacement work of gear machining accuracy is not high.

1. The spur bevel gear sample

Spur bevel gear parameters as shown in table 1, the structure and technical requirements as shown in figure 1.

2. The processing method and steps of straight bevel gear

(1) select bevel gear cutter. Due to the big end and small end diameter bevel gears are not equal, so big, small end diameter is not equal, big end of involute tooth profile is flat, small end is bent. With forming cutter milling spiral bevel gear tooth, to conform to the big end can't conform to the small side. With bevel gear milling cutter in milling machine processing, therefore, bevel gear, the tooth profile is impossible all accurate, so the precision is low.

Bevel gear is standard to carry on the design of the parameters of the big end, therefore the bevel gear cutter tooth profile curve should according to the big end. In addition, because of the small bevel gear, the tooth is relatively narrow, small standard bevel gear side groove width for two-thirds of the big end, so the thickness of the bevel gear cutter should be made according to the small end, and should also be a little thinner than the small end tooth. Bevel gear cutter, unlike ordinary cylindrical gear milling cutter, to prevent wrong, with the bevel gear cutter's profile "" tag.

For bevel gear tooth is in on the surface of the cone, so the bevel gear tooth profile curve of the milling cutter should be vertical to dividing the conical surface and cross section on the tooth profile of the same. Bevel gear cutter also like cylindrical gear milling cutter, each module according to the tooth profile curve of bending degree is divided into eight knife, as shown in table 2. The difference is to choose according to the equivalent number of teeth. This case is not choose by 25 gear milling cutter, 4 but should first calculate the equivalent number of teeth that should be at 35 pitch selection module for 3 mm 6 bevel gear cutter.

(2) the workpiece clamping and adjustment. Before the workpiece clamping, should check gear billet, with universal protractor check tooth Angle and back Angle; Check the datum to the distance of the cylindrical; Check the gear billet diameter, etc.

The clamping workpiece. The different shapes of the structure, method of the clamping used bevel gear is mandrel and clamping nut, spindle petiole Morse taper and dividing head spindle taper hole suitable, and tighten the screw fastening on dividing head. Cylindrical part of the work piece in shaft with a dial indicator to align with the nut after compression (see figure 2).

For small diameter and cone Angle is larger or smaller slot bottom and inner hole is very close to the surface of the bevel gear (see figure 3), in order to avoid milling gear when the nut spindle damage, even can use taper is 1:8 000 ~ 1:1, 000 micro taper spindle clamping, concrete should be based on factors such as pore size tolerance level to determine.

The cone Angle and the end with larger diameter, the steps or larger aperture was to be part of the workpiece, such as can be directly used to dividing head of three jaw self centering chuck clamping.

When the clamping workpiece alignment. If the bevel gears using special clamping of spindle or spring clip and general alignment is not required. If use micro taper spindle clamping, generally do not have to be looking for is, when necessary for bevel gear of the big end face do inspection and alignment. With chuck and clearance fit spindle clamping, you need to find is beating big end and small end radial circular workpiece, and the big end face round.

The adjustment of the dividing head. Dividing head is installed on the workbench, must make the spindle axis and the direction of feed, and then the dividing head spindle on a cutting Angle, its size is equal to the cone Angle f.

The milling depth adjustment. Artifacts and dividing head, adjust good, after the split of the milling cutter first adjust to through the workpiece axis (tool), then make the brush cutter contact to the big end cone (based on big end), and exit the artifacts, workbench rise will be a big end whole depth (2.2 m), you can begin to central milling tooth. Modulus of the workpiece, in depth can be divided into several feed milling.

In order to prevent cutting of the dividing head spindle caused by sudden accidents, feeding direction is from the big end milling best towards the small end.

(3) partial milling principle and method. Bevel gear tooth and tooth groove are deflating, namely narrow width, small end on the big end. In processing when dividing head although have pull up a root cone Angle f, make bevel gear of the outside cone face big end slightly higher than the small end, while milling large end slightly darker than the small end, space width big end is slightly wider than the end, but this difference also cannot meet the requirements, needs to be on both sides of the big end tooth milling to some more. On milling machine milling of bevel gear, the first feed milling after middle tooth, big end of tooth profile has been, but the groove width size do not meet the requirements, therefore, each tooth is typically three milling knife, to make the big end tooth groove on both sides of the milling to some more, the purpose of a spiral bevel gear milling tooth groove on both sides of the process is called partial milling allowance. The principle of partial milling is: on the one hand, make the workpiece deflection; On the other hand moving workbench, small end tooth on the milling cutter again. Using the workpiece in the vertical deflection big end and small end't give direction (horizontal) on the deflection difference, make the milling allowance from the small to the big end, will go to some more big end milling.

The milling of bevel gear partial milling method are many, but because the cone distance and the ratio of the tooth width (R/b), and pitch cone Angle and the tooth number of different parameters, such as, any kind of method can apply to all the bevel gear processing, therefore, can only be chosen according to the specific case, and try to correct them. Often adopt the method of rotary volume combined with offset milling, as shown in figure 4.

The first method. Calculating the offset S first, amount of rotary workpiece axis around itself be determined by trial cut. The calculation method of S value also has several, introduce one of the kind of calculation formula, T is the thickness of the milling cutter in the pitch diameter (mm); X for migration coefficient (see table 3).

 

In 4 bevel gear as an example, if use gear caliper measured T = 2.58 mm from the milling cutter, Chad from table 3 x = 0.266, it S = T / 2 - mx = 2.58 present 2-3 x 0.266 = 0.492 (mm).

Processing, middle tooth groove milling, the lateral displacement worktable S = 0.492 mm, to shake the dividing handle, make small end tooth on the milling cutter, again to write down the handle rotation amount of N, milling teeth on one side of the tank. When the other side of the milling tooth, should make workbench reverse move 2 s = 0.984 mm, the amount of reverse rotation handle to 2 n.

The second method. To count the amount of rotary indexing head handle N, workbench offset S determined by trial cut. The calculation method of the value of N also has several, introduce one type of z for bevel gear teeth, teeth when take 4 / z; Teeth long take 5 / z.

The third method. Is the dividing head deflection Angle and the offset in the plane of the method of combining the milling. First calculate dividing head and the deflection Angle of alpha in the plane of the workpiece, the workbench of transverse offset S determined by trial cut. Available the following approximation formula

 

Type, R for bevel gear cone distance (mm).

Again to 4 bevel gear as an example, the deflection Angle alpha is zero

The pieces as part of the revolving body parts, module 6 mm, teeth is 24, tooth profile Angle of 20 °, 35 ° spiral Angle, precision grade five. Cylindrical workpiece including phi 80 js6 two, phi 75 h6 cylindrical main dimensions, requirements from 80 js6 round two, 75 h6 cylindrical coaxial degree is 0.008 mm, each other and tooth top cone and phi 80 js6 benchmark A run-out tolerance in 0.02 mm, the cylindrical spiral bevel gear tooth of quenching heat treatment. Its tooth department for the hard tooth face, is not easy to meet the accuracy requirement.

Parts processing scheme

Hard tooth surface finishing of spiral bevel gear YouYan gear and gear grinding two main methods. Lapping method is one of the traditional technology, high production efficiency, under the condition of the heat treatment deformation is not big, lapping can change effective tooth surface roughness and the contact position, and slightly modified tooth profile and tooth to error. But for eliminating radial circular runout, circular pitch error, the tooth profile error and other errors due to the heat treatment deformation, lapping is powerless. Gear grinding process can obtain high machining accuracy, the past is only used for precision gear transmission and aviation and other special occasions. According to the technical requirements of the parts, made the machining of two kinds of schemes. One way is by heat treatment after hard tooth surface of spiral bevel gear lapping, specific methods by numerical control car CKA6150 by half, finish machining spiral bevel gear nc program of front and back cone, cone and work out two end center hole for benchmark process. Universal grinding machine with center hole as a benchmark, cylindrical grinding phi 80 js6 two, phi 75 h6 cylindrical main dimensions, to ensure its alignment requirements; CNC arc tooth milling YKD2280 employing five cutting processing, can make the contact of tooth area and the surface quality is better. Gear after heat treatment, grinding teeth. Scheme 2 is a spiral bevel gear heat treatment after the hard tooth face gear grinding. Specific methods by numerical control car CKA6150 by half, finish machining of spiral bevel gear nc program before cone and cone back and phi 110 mm cylindrical as looking for is a benchmark, and work out two end center hole for process benchmark; Universal grinding machine with center hole as a benchmark, cylindrical grinding phi 80 js6 two, phi 75 h6 cylindrical main dimensions, and external circular grinding phi 110 mm as looking for is a benchmark, ensure the 0.008 mm with the above cylindrical coaxial degree requirements, phi 110 mm outer circle circle degree in 0.008 mm; CNC arc tooth milling YKD2280 by a single number of the single side method processing tooth, tooth surface grinding both sides remain amount of 0.3 mm. Gear after heat treatment, grinding teeth of gear grinding machine.

To sum up, with CNC arc tooth taper gear grinding machine of promotion and grinding head of power increase, gear cutting and grinding efficiency have efficiency, such as machinery, automobile and aerospace industry for a wide range of applications, suitable for mass production of high efficiency, low cost and high quality processing technology. So the parts processing scheme USES the scheme 2.

Parts are the key working procedure

1) according to the current situation of the artifacts and material, forging blank choice, workpiece is heat treatment after forging, to refine grain internal organization, improve the cutting performance of the workpiece.

2) rough machining of workpiece, conditioning treatment after rough machining, improve the strength and toughness, make it has better comprehensive mechanical properties, and eliminate the internal stress of workpiece.

3) benchmark, installation datum and find is the benchmark to determine. Numerical control car hit central hole on the surface of the ends as a benchmark, universal grinding with central hole on both ends of the top jacking, cylindrical grinding phi 80 js6 two and 75 cylindrical h6, phi phi 110 mm cylindrical guarantee its alignment, by grinding the right end face of the 61.97 mm size in figure 1 to ensure its beating within 0.005 mm. Will the phi 110 mm cylindrical as looking for is a benchmark, and the cylindrical phi 80 js6 right end face of the 61.97 mm size as the install base. Franklin berg gear grinding machine grinding teeth before, will and the cylindrical workpiece with phi 80 js6 right end face of the 61.97 mm size installation as a benchmark, and gear grinding fixture installation, alignment phi 110 mm after external cylindrical grinding teeth. Gear grinding fixture structure as shown in figure 2, the composed of a number 1 locating sleeve and package number 2 artifacts cooperate with installation; Package number 3 for franklin berg gear grinding machine with intermediate set, after assembly and package number 1 positioning fit, use a number 2 artifacts back-end M10 threaded hole, M10 and gear grinding machine after clamping screw connection.

 

4) numerical control process. Centering on the surface of workpiece length at both ends and jacking according to nc program fine car out of the top cone and cone back, the rest of the amount set aside the cylindrical heat treatment after finishing mill.

5) nc arc tooth milling process: CNC arc gear milling machine tool adjustment calculation, determine the project parameters needed for processing, this piece is based on the gleason single cutting method of calculating the project parameters, calculation formula can refer to the manual gear such as reference books. The main project parameters are shown in table 1. CNC arc tooth milling tooth, arc tooth on the fixture, and the cylindrical js6 phi 80 right end face of the 61.97 mm size for installation, milling each gear tooth thickness to keep grinding amount of 0.3 mm.

6) universal grinding process. In the tooth department before and after heat treatment have a universal grinding process, cylindrical grinding phi 80 js6 two and 75 cylindrical h6, phi phi 110 mm cylindrical guarantee its alignment, by grinding the right end face of the 61.97 mm size to ensure its beating within 0.005 mm.

7) kling berg gear grinding machine process: using KIMoS 5 software adopts five knife method 2, Trace grinding method, optimized can get the most reasonable value, so as to calculate arc tooth wimble gear machining process. According to calculate the spiral bevel gear machining procedure, grinding the teeth. Machine tool online detection, after a komet, eliminate the error between calculating program, so as to obtain ideal contact region.

 

The choice of the finishing tool

1. The cylindrical, cone and processing

Sandvik tooling, knife body DCLNR 3225 p 12, blade model CNMG12 04 08 - WF. Cutting parameters are shown in table 2.

 

2. The tooth surface grinding tool

Choose NORTON NORTON grinding wheel, type 5 sg60 - JVS, size 13.8 * 3.5 * 12 ". Cutting parameters are shown in table 3.

 

conclusion

After using the machining method, the level DIN2 for spiral bevel gear, the gear meshing, contact area can completely satisfy the requirements of users. To provide users with the mass production of high quality and low noise of arc tooth wimble gear.

 

More knowledge about the spiral bevel gear: http://www.www.xiqiye.com

 

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