The influence of the shape R angle, the small details between PCB design and production.
Careful partners can easily find that the right angle of the original design is 90 degrees. When the board comes back, it turns into a R angle, which directly affects the accuracy of the shape. When it is serious, it will cause the device's position to be insufficient or unable to fit or fit with the shell.
Circuit board R angle
The formation of the R angle of the circuit board: when the PCB is used in forming, the Gong knife is round to the high speed rotating the PCB edge and inner groove of the Gong mill. The Gong knife can not turn the remaining sharp corners off, thus generating the R angle. The bigger the diameter of the Gong knife, the bigger the R angle is.
PCB slot file
Suggestion 1: when placing orders, remark the order with accuracy requirement, and add the "angle clearance hole" at the angle of the form note in the order note column.
Suggestion 2: in the design of PCB outer frame, the shape is concave a little (see the figure below), and the arc of concave is directly greater than 0.8mm. 
