For motor products, the whole machine product involves processing and installation datum. The foot surface of the motor base and the flange end cover installation plane are the most common installation datum planes. How to choose the machining datum, directly affects the machining accuracy of parts and components and the installation accuracy of the complete product and supporting equipment.

* 01 Selection of base machining standards 

For small and medium-sized motors, cast iron frame is mostly used.The common processing technology is to first process the end stop of the machine base, based on this, the other end of the frame stop and inner bore are machined. After releasing the clamping stress, finish machining is
completed on the second car, Finally, the base foot surface is processed. The feature of this process is that it takes one end stop as the initial processing benchmark, which can ensure installation mode is universal.

In order to ensure that the installation accuracy of the whole machine and the size of external interface meet the requirements, the fixed end holes at both ends of the machine base should be processed based on the bottom foot and stop,Especially for B35 motor installation, the position between flange fixing hole and base foot hole is very high, and there is no reliable process guarantee , so the proportion of unqualified motor in on-site acceptance will be the biggest hidden danger of losing customers.
 
For large-scale high-voltage motors, the base foot is often used as the benchmark, Especially, because the base foot of large-scale motor is a combination of  multiple planes, and the force of the processed parts， The benchmark selection of this method is more conducive to the  compliance requirements of the whole machine installation.
 
* 02 End cover machining datum control
The size of motor end cover is related to the radial and axial control requirements during the installation process. Via hole is the key to ensure the radial dimension in the assembly process, For the installation of B35 end cover, the drilling process must also take into account the installation requirements of the whole machine. Datum sharing is to reduce the accumulation. Error is an important means, motor parts design and processing technology should be determined.The choice of benchmark is an important factor.