The physical and mechanical properties of Dalian NC machined surface layer include work hardening, residual stress and metallographic structure change of surface layer. Due to the combined effect of cutting force and heat, the physical and mechanical properties of the surface metal have changed compared with the physical and mechanical properties of the basic metal. The effect of cutting heat can also change the phase transformation and grain size of the material on the surface of the workpiece.

Changes in the metallographic structure of the surface layer. Surface quality of parts is an important part of the quality of mechanical processing. Surface quality refers to the change of the micro-geometric structure of the surface layer of parts and the properties of surface metal materials after mechanical processing. The surface of machined parts is not an ideal smooth surface. It has some surface defects such as rough ripple, cold hardness, cracks and so on.

The wear, corrosion and fatigue damage of parts start from the surface of parts, especially in the direction of precision, high-speed and multi-functional development of modern industrial production, working in the condition of high temperature, high pressure, high speed and high stress. Any defect will accelerate the failure of parts.

The size of the positions of the processing parts should be measured accurately and timely after inspection. After roughing and repairing, semi-finishing or finishing can be carried out. After finishing, technicians should check the shape and size of the processing parts, mainly inspecting the vertical and inclined processing parts and the size of the base points marked on the measurement drawings.

The selection of horizontal machining centers should be based on their types and characteristics. Horizontal machining centers can be divided into fixed and movable pillar types according to whether the pillars move or not. Fixed column type worktable cross movement, worktable X, Z direction movement, spindle box Y direction movement, spindle box on the column has positive hanging, side hanging two forms. It is suitable for boring and milling of medium and complex parts. The spindle box moves in cross direction, the spindle box moves in X and Z direction, and the worktable moves in Y direction.