What are the main difficulties in gear machining?
The difficulties of gear processing are mainly focused on the design and implementation of several key processes. First of all, the precision design of the gear blank, the transmission accuracy of the gear is often affected by the tooth shape accuracy and the uniformity of the tooth pitch distribution, so the preparation of the precision reference is very important. This is followed by the design of the tooth profile to ensure that the gear fully meets the requirements of the drawings and can meet the tooth profile accuracy in the final precision stage. The heat treatment process of gears is also a key link, especially the quenching treatment of the tooth surface to meet the hardness requirements. Finally, the precision treatment of the tooth shape is to correct the tooth shape deformation caused by the gear quenching, and further improve the tooth shape accuracy and reduce the surface roughness to ensure that the gear reaches the final accuracy.
How do I determine the positioning datum of a gear?
The positioning datum of the gear has a direct impact on the tooth profile accuracy. Usually, the tooth profile of the gear shaft will be positioned with the center hole, while the disc gear may be positioned with the inner hole and the end face to ensure uniform accuracy. Especially for large-module shaft gears, the gear journal and end face are selected for positioning. When positioning, the inner hole can be used as a design datum, as well as a measurement and assembly datum, in line with the principle of "datum coincidence"; The outer circle and end face positioning require a small radial runout of the outer circle of the tooth blank to ensure accurate positioning.
How to design tooth end accuracy?
Tooth end machining is also crucial, with common methods such as rounding, chamfering, chamfering and deburring. Rounding and chamfering help make it easier for gears to enter the engagement as they slide axially, while chamfering removes sharp edges that can become brittle after quenching, causing the gear to crack in transmission. Tooth end machining is usually scheduled before gear quenching and often after the hobbing process.
How do I make a fine benchmark correction?
After the gear is quenched, the reference hole may be deformed, so it is necessary to correct the reference hole to ensure the quality of the tooth profile precision. For spline hole gears with outer diameter centering, spline pusher correction is generally used, while for cylindrical hole gears, it can be corrected by pushing or grinding holes. Grinding holes can provide higher accuracy, especially for gears with large inner hole deformation or high hardness after quenching. When grinding holes, the gear indexing circle is often used as a centering reference to reduce radial runout and facilitate subsequent gear grinding or honing operations.