For electric motor products, the whole machine involves processing datum and installation datum. The motor base foot surface and flange end cover installation plane are the most common installation datum planes. In the machining process of parts , any part that affects the installation accuracy and matching accuracy has the problem of datum selection before machining. How to select the machining datum, or how to select the clamping position, is directly related to the machining accuracy of parts and the installation accuracy of the whole machine product and supporting equipment.

For small and medium-sized motors, cast iron bases are mostly used. The more common processing technology is to first process the stopper at one end of the base, and use this as a reference to process the stopper and inner bore of the other end of the base, release the clamping stress, and then complete the finishing process for the second time, and finally process the base foot surface. The characteristic of this process is that the stopper at one end is used as the initial processing reference, which can ensure the universality of the early process of the base with various installation methods.

In order to ensure that the installation accuracy and external interface size of the whole machine meet the requirements under different installation methods, the fixed end holes at both ends of the machine base should be processed based on the foot surface and the stopper to avoid the influence of the position error of the fastening screw holes on the assembly accuracy. Especially for the B35 installation motor, the flange stopper of the flange end cover and the plane of the machine base foot are the dual positioning references of the external interface. The position requirements between the flange fixing hole and the machine base foot hole are very high. Without reliable process guarantee measures, the proportion of unqualified motors in on-site acceptance will be the biggest hidden danger of losing customers.

For large high-voltage motors, due to the differences in processing technology, the base foot surface is often used as the reference, and the base stop, inner bore and other dimensions are processed through a one-cut process. In particular, since the base foot surface of a large motor is a combination of multiple planes and the workpiece is subjected to force during the processing, this method of base selection is more conducive to the compliance requirements of the entire machine installation.

The size of the motor end cover involves the radial and axial control requirements during the installation process. Using the end cover bearing chamber as a reference to process the end cover and the inner and outer covers of the bearing as well as the through holes connected to the machine base is the key to ensuring the radial size during the assembly process. It should be emphasized that for the B35 installation end cover, the drilling process must also take into account the installation requirements of the entire machine.

From the perspective of the accumulation of processing deviations and the relationship between dimension chains, datum sharing is an important means to reduce accumulated errors. When designing motor components and determining processing technology, the selection of datums should be considered an important factor.