Abstract: Embodiments of the present disclosure provide a datum selection method for minimizing hole position errors in group hole machining of large components, comprising: 1) determining a type of a computer numerical control (CNC) machine tool and establishing a topological structure of the CNC machine tool; 2) establishing a theoretical postural model of a tool center point during a motion; 3) establishing a hole position error model; 4) establishing an average error model of hole positions in group hole machining; and 5) obtaining a machining datum for group holes of corresponding components. For the skeleton and skinned group hole machining of aircraft components, different principles of datum selection are provided respectively, which can effectively improve the positional accuracy of the skeleton or skinned group hole machining, at the same time provides a more scientific and reasonable approach for the datum selection in group hole machining of large components.

Abstract: The present disclosure provides a circuit board. The circuit board may include a number of stacked core boards each having a top surface. At least part core boards of the number of stacked core boards may include circuit layers at top surfaces thereof. A groove may be defined through the at least part core boards. A conductive material may be received in the groove configured to couple to the circuit layers of at least two core boards. A cross section of the groove may include a length in a first direction and a length in a second direction, and the length in the first direction may be greater than the length in the second direction. Electroplating solution may capable of contacting any portions of the groove to electroplate, to form the conductive material.

Abstract: The present disclosure provides a circuit board. The circuit board may include a number of stacked core boards each having a top surface. At least part core boards of the number of stacked core boards may include circuit layers at top surfaces thereof. A groove may be defined through the at least part core boards. A conductive material may be received in the groove configured to couple to the circuit layers of at least two core boards. A cross section of the groove may include a length in a first direction and a length in a second direction, and the length in the first direction may be greater than the length in the second direction. Electroplating solution may capable of contacting any portions of the groove to electroplate, to form the conductive material.