Overview of commutator manufacturers on surface finishing of motor commutators

The commutator is a component of the DC motor and the AC series motor as the current commutation. The commutator manufacturer calls it a commutator to keep the motor running. The voltage amplitude between the brushes fluctuates between zero and extreme values, but always maintains the same polarity. The commutator consists of segments, which are insulated from each other. When the brush is passed from one segment to another, there is a moment when the brush touches both segments at the same time, which is called the neutral plane. At this time, the induced voltage is zero. Otherwise the brushes will short the ends of the coil and cause sparks due to high voltage.

Commutator surface requirements: In order to make the carbon brushes run fast and smoothly on the commutator surface, the commutator surface needs to have a certain peak and valley height. The peak-to-valley height of the commutator surface measured in the axial direction is 6-10 m, which avoids excessive friction coefficient. Under the premise of this height, the more lines the lathe has, the better. At the same time, the shaft of the commutator should run smoothly over the entire length of the copper sheet. If the surface of the commutator is too smooth, the friction coefficient of the carbon brushes running on the surface of the commutator will increase, and even crawling and abnormal noise will occur. In this case, the electric spark will make the color of the commutator surface uneven, and the normal metal oxide film contact layer cannot be formed on the surface of the commutator, thereby increasing the wear of the carbon brushes.

Commutator surface processing characteristics: In the motor industry, the commutator materials are oxygen-free copper and silver-copper alloy, and its main component is copper. Because copper is a typical plastic material, it is tough and soft in texture, with low strength and hardness. The linear expansion coefficient is large, the processing is easy to heat up, the dimensional accuracy is difficult to control, and it is easy to produce copper sheet adhesion. In addition, the working surface of the commutator is processed with an undercut insulating groove, and the fine turning is intermittent cutting, which is easy to cause flashing or stretching of the edge of the notch. During the cutting process, when the cutting stress reaches and exceeds the yield strength of the workpiece material, plastic deformation begins to occur, resulting in shear slip deformation. Then, when the scissors are pressed against the material, filamentous or ribbon-like chips are formed and flow out along the rake face. The machined surface is squeezed and rubbed by the rounded portions of the cutting edge and flank, resulting in deformation and springback, resulting in fibrillation and work hardening. In the process of finishing the commutator, the commutator manufacturer should select appropriate tool geometric parameters, tool materials and cutting parameters to control the cutting temperature rise, the deformation and rebound of the machined surface, and ensure the finishing of the commutator surface. quality.

Selection of finishing tool for commutator: PCD material has the advantages of wear resistance, high hardness, low friction coefficient and low surface roughness. Commutator manufacturers use this material tool to select the appropriate tool geometry angle and Cutting parameters The fine turning commutator avoids the drawbacks of cleaning the notch after the traditional hook cutter fine turning, and can fully guarantee the product quality requirements, thereby effectively improving the motor commutation.