The gear rack is a mechanical device that transforms rotational motion into linear movement. It is an important component in conveying systems and can also be found in extrusion and lifting/lowering applications.
The pinion is the circular gear that rotates and moves most about the gear rack. When the pinion and the gear rack mesh together, they transfer rotational motion to a linear motion system. The pinion and the rack are both used in applications that require high precision.
Common types of racks include round, square and rectangular. Rectangular racks have a cross section that is the same as a normal gear. This makes them strong, but they also need suitable bearings to prevent the rack from rotating.
These bearings are primarily made of steel, but they may be made from stainless steel or plastic materials depending on the application. The shape of the pinion gear and the rod are also important.
Unlike a ball screw, which has a straight tooth axis parallel to the axis of rotation, gear racks have a series of teeth that are twisted along a helical path in the axial direction. They are quieter and more efficient than straight tooth gears.
KHK stocks the following types of racks for use in high precision linear motion applications:
Module 0.5 to 10 (with metric or module pitch) * These racks are manufactured for a range of precision levels and feature a high level of accuracy. They are available in lengths up to 2000 mm and can be butted or mounted with mounting screws for easier assembly.
Note: Products with a module less than 0.8 are thermal refined. They do not have their gear teeth induction hardened, but are still precision grade.
2.Chamfering at the top land of the gear tooth for reducing noise is patented by KHK. This chamfering reduces vibration, increases strength and improves noise reduction.
3.Round chamfering at the corners of the top land of the gear tooth is a product characteristic of KHK stock racks; this reduces vibration, increases strength and improves quietness.
4.Pitch error – The exact amount of dimensional tolerance in the rack varies between modules, and the value can be measured at the end of production using a linear measuring machine. Pitch error is usually used in conjunction with other dimensional tolerances to create an “assembly map” that helps to minimize the total cumulative pitch error on the axis.
5.Pitch line control is important when connecting two racks or making gear connections. The accuracy of these connections will be affected by the bottom surfaces machining, so it is important to ensure that they are not drilled before connecting them.
6.Thermal refinement is not recommended for racks with their gear teeth in. This is because the heat treatment can deform the gear teeth and cause them to lose their precision.
In addition to the standard features listed above, racks with a module of 0.8 or higher are manufactured for high precision and feature an applied black oxide coating that protects them from rust.