When CNC machining spherical surface, especially quadrants of the ball, surface, due to improper adjustment, it is easy to produce shoulder, shovel back and so on. The main reasons are as follows:

1. System clearance

In the drive pair of CNC machining equipment, there is a certain gap between the lead screw and the nut. With the increase of the equipment's operation time, the gap gradually increases due to wear and tear. Therefore, the corresponding gap compensation during the reverse movement is the main factor to overcome the manufacturing surface shoulder. The gap measurement is usually carried out by a dial indicator method, and the error is controlled within 0.01 ~ 0.02mm. Here to point out that table seat and table rod should not extend too high and too long, because the measurement due to the cantilever is longer, table seat easy to force to move, resulting in inaccurate counting, compensation value is not real.

2. Uneven machining allowance

Before the realization of CNC machining parts design surface, whether the machining surface to be processed is uniform is also an important reason for the forming surface can meet the design requirements, because the uneven machining allowance is easy to cause "reflection" error. Therefore, the surface shape of the parts with higher requirements, should be as far as possible to achieve the processing allowance uniformity or through a multi-machining method to meet the design requirements.

3. Improper tool selection

CNC machining tools are used to remove materials through the main cutting edge. However, after the arc is processed through the quadrant, the arc is tangent to the cutting edge of the tool (the intersection line between the back of the tool and the base plane), then the cutting edge may participate in the cutting (that is, the back of the shovel). Therefore, in the choice or repair tool, must consider the tool wedge Angle.