Selection of the machining plan of the tooth blank
For the tooth blanks of shaft gears and sleeve gears, the machining process is basically similar to that of general shafts and sleeves. Now we mainly discuss the machining process of disc gear blanks. The processing plan of the gear blank mainly depends on the wheel structure and production type of the gear.
1. Machining of gear blanks for mass production
When a large number of medium-sized tooth blanks are processed in large quantities, the process of "drilling, pulling, and multi-tool turning" is often used.
(1) Drilling or reaming is performed by positioning the outer circle and end face of the blank.
(2) Pull holes.
(3) Use holes to locate the outer circle, end face, grooving and chamfering on a multi-tool semi-automatic lathe.
This kind of technological scheme adopts high-efficiency machine tools to form an assembly line or an automatic line, so the production efficiency is high.
2. Tooth blank processing for mass production
When producing gear blanks in batches, the process of "car-pulling-carriage" is often used
(1) Position the outer circle, end face and inner hole of the tooth blank or wheel.
(2) The pull hole (or spline hole) is supported by the end face.
(3) Use holes to locate the outer circle and end face of the precision turning.
This kind of scheme can be realized by horizontal lathe or turret lathe and broaching machine. It is characterized by stable processing quality and high production efficiency.
When the tooth blank hole has a step or the end face has a groove, the multi-tool on the turret lathe can be fully utilized for multi-station processing, and the tooth blank can be processed at one time on the turret lathe.
Gear tooth processing method
The tooth profile processing of the gear ring is the core of the entire gear processing. There are many processes in gear processing, all of which serve for tooth profile processing, and the purpose is to obtain gears that meet the accuracy requirements in the end.
According to the processing principle, the tooth profile can be divided into forming method and generating method. The forming method is a method of cutting the tooth surface with a forming tool that matches the shape of the tooth groove of the gear to be cut, such as tooth milling, tooth pulling, and forming tooth grinding.
The generative method is a method in which the gear cutter and the workpiece perform a generative motion to cut out the tooth surface according to the meshing relationship of the gear pair, such as gear hobbing, gear shaping, gear shaving, gear grinding and honing.
The choice of tooth profile machining plan mainly depends on the gear's precision grade, structure shape, production type and production conditions. For gears of different precision grades, the commonly used tooth profile machining plans are as follows:
(1) Gears with accuracy below grade 8
Hardened and tempered gears can meet the requirements with gear hobbing or gear shaping. For hardened gears, a machining plan of rolling (shaping) teeth-tooth end processing-quenching-correction hole can be used. However, the machining accuracy of the tooth profile should be improved by one level before quenching.
(2) 6-7 grade precision gear
For hardened gears, the following can be used: rough hobbing-fine hobbing-tooth end machining-fine shaving-surface hardening-calibration reference-honing.
(3) Gears with accuracy above grade 5
Generally used: rough gear hobbing-fine gear hobbing-tooth end machining-quenching-calibration reference-rough grinding gear-fine grinding gear. Gear grinding is the machining method with the highest precision in tooth profile machining and the smallest surface roughness value. The highest precision can reach 3-4.
1. Tooth milling
Gear accuracy grade: Below grade 9
Tooth surface roughness Ra: 6.3~3.2μm
Scope of application: processing low-precision external cylindrical gears, racks, bevel gears, and worm gears in the production of single-piece repairs
2. Pull teeth
Gear accuracy grade: Level 7
Tooth surface roughness Ra: 1.6~0.4μm
Scope of application: mass production of 7-level internal gears, external gear broaches are complicated to manufacture, so use less
3. Hobbing
Gear accuracy grade: 8~7
Tooth surface roughness Ra: 3.2~1.6μm
Scope of application: processing medium-quality external cylindrical gears and worm gears in various mass production
4. Gear shaper
Gear accuracy grade: 8~7
Tooth surface roughness Ra: 1.6μm
Scope of application: processing medium-quality internal and external cylindrical gears, multiple gears and small racks in various mass production
5. Rolling (or inserting) teeth-quenching-honing
Gear accuracy grade: 8~7
Tooth surface roughness Ra: 0.8~0.4μm
Scope of application: gears used for tooth surface quenching
6. Gear hobbing-gear shaving
Gear accuracy grade: 7~6
Tooth surface roughness Ra: 0.8~0.4μm
Scope of application: mainly used for mass production
7. Hobbing-shaving-quenching-honing
Gear accuracy grade: 7~6
Tooth surface roughness Ra: 0.4~0.2μm
Scope of application: mainly used for mass production
8. Rolling (inserting) teeth—quenching—grinding
Gear accuracy grade: 6~3
Tooth surface roughness Ra: 0.4~0.2μm
Scope of application: used for tooth surface processing of high-precision gears, with low productivity and high cost
9. Rolling (inserting) teeth-grinding teeth
Gear accuracy grade: 6~3
Tooth surface roughness Ra: 0.4~0.2μm
Scope of application: used for tooth surface processing of high-precision gears, with low productivity and high cost
Tooth end processing
The tooth end of the gear can be processed with rounding, chamfering, chamfering and deburring, as shown in the figure below. The rounded and inverted gears are easy to enter the meshing state when shifting gears, reducing impact. Chamfering can remove the sharp edges and burrs of the tooth end.
Gear tooth end processing
Tooth end processing
a) rounded b) inverted point c) chamfered
The following figure is a schematic diagram of rounding the tooth end with a finger milling cutter. When rounding, the milling cutter rotates at a high speed and swings along an arc. After processing one tooth, the workpiece moves away from the milling cutter, and after indexing, the milling cutter quickly approaches the tooth end of the next tooth to be machined. Tooth end processing must be carried out before gear quenching, usually after gear rolling (shaping) and before gear shaving.
