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Main Contents of Gear Finishing Processes

Time: 2021-07-01 Hits: 57

   The finishing is the last step of a gear processing. The finishing process mainly includes two parts: the selection of benchmarks and the processing of gear blanks.

1. Selection of benchmarks
   The benchmark selection of gear processing often differs due to different structure and shape of a gear. Gears with shafts are mainly located by apex holes. For hollow shafts, after drilling a central inner hole, the inclined surfaces of the holes at both ends for positioning is used. When the diameter of the hole is large, taper plugs are used. The accuracy of vertex positioning is high and the reference can be overlapped and unified. For gears with holes, the following two positioning and clamping methods are often used during tooth surface processing.

   (1) Positioning on outer circle and end face. When the matching gap between the workpiece and the aggravating mandrel is large, use a dial gauge to correct the outer circle to determine the position of the center, and use the end face for axial positioning, and clamp from the other end face. This positioning method has low productivity because each workpiece needs to be calibrated. At the same time, it requires greatly for the inner and outer circle coaxially of the tooth blank, but not high requirements for the accuracy of the fixture. Thus it is suitable for single-piece and small-batch production.

   (2) Positioning with inner hole and end face. This positioning method is to locate the inner hole of the workpiece, determining the positioning position, and then using the end surface as the axial positioning reference and clamping the end surface. In this way, the positioning datum, design datum, assembly datum and measurement datum can be overlapped. The positioning accuracy is high, which is suitable for mass production. However, the manufacturing accuracy of the fixture is relatively high.

2. Processing of gear blanks
   The gear blank processing before tooth surface processing occupies a very important position in an entire gear processing process. Since the benchmarks used for tooth surface machining and testing must be processed at this stage and the proportion of man-hours for gear blank processing is relatively large, we must pay attention to the processing of gear blanks no matter from improving productivity or ensuring gear processing quality angle. For the technical requirements of the gear pattern, attention should be paid to the accuracy requirements of the addendum circle if it is specified that the tooth thickness reduction of the index circle is used to determine the tooth side clearance, because the detection of the tooth thickness is measured by the addendum circle benchmark. The accuracy of the addendum circle is too low, which will inevitably makes the measured tooth thickness unable to accurately reflect the size of the tooth side clearance. Therefore, the following three issues should be paid attention to during this processing:

   (1) When the addendum circle is used as the measurement reference, the dimensional accuracy of the addendum circle should be strictly controlled.

   (2) Ensure the verticality between the positioning end face and the positioning hole or outer circle.

   (3) Improve the manufacturing accuracy of the inner hole of the gear and reduce the clearance with the fixture mandrel.

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