The causes are roughly summarized as:
● Improper clamping and excessive clamping force.
● The contact surface of the positioning chassis is not clean and the chassis is too loose.
● The clamping force is not properly relaxed before finishing, and the rough finisher does not divide.
● Before machining, the internal stress of the casting or weldment is not fully released.
● Casting material failed. For example, if there is too much free graphite in the iron, the strength and stiffness of the base are reduced, and deformation easily occurs.
● The rigidity of the base is poor. If the design does not take into account the stress on the machine frame during the cutting process is much greater than the normal operation, the design of the machine base is too weak and easily deformed.
● The error of the machine tool and the influence of the measuring temperature caused by the deformation of the spindle and the wear of the guide rail.
● If the end face is uneven or there are iron filings when the stand is placed, or the stand is not pressed, it will cause the horseshoe or the machine seat to be different from the inner crotch after machining.
How to improve the quality of the base
The precision of the motor base and the end caps of the end caps meet the design requirements, which determines the quality level and grade of the motor. The external appearance is the flexibility of the motor shaft rotation. If the motor shaft is stuck, it is undoubtedly related to the base or cover.
● End cap processing
It is easy to complete the processing of each structural dimension in one clamping and it is easy to meet the design requirements.
Generally, it is divided into two steps: first, correct the outer circle and the two ends of the machine seat blank, and process the first section end port; secondly, position the first section end port and the end surface, and process the other end port. The coaxiality of the two ends and the inner bore, the squareness of the end face of the base and the center of the base are the most difficult and must guarantee position tolerances in the turning process of the base.
It can be seen that all kinds of mechanical defects of the motor are solved, and the key is to ensure the machining quality level of the base. The following measures should be taken for the machine processing characteristics and key dimensions:
● Strict process rules are established. The clamping force of the roughing process should be large enough, and the finishing clamping force should be appropriate.
● Welded bases, cast steel stands, and high-strength cast iron stands should be annealed to eliminate internal stresses. After ordinary cast iron stands are cast, they should be placed for a suitable period of time, that is, they should naturally fail.
● Workpieces with very strict deformation restrictions must be annealed after the rough machining to relieve stress.
● Appropriately increase the wall thickness, add stiffeners or use stronger materials with better rigidity.
● Maintain the machine on a regular basis and take measures to eliminate the influence of measuring temperature.