The roughness of workpieces processed by CNC lathes is affected by many factors, some of the main factors include:

1. Tool selection and cutting parameters: CNC lathes use different types, materials and cutting edge geometries of tools, as well as different cutting speeds, feed speeds and cutting depths, which will directly affect the surface quality and roughness of the workpiece. Typically, the finer cutting edges and smaller feed rates of CNC lathes produce smoother surfaces.

2. Tool wear: The degree of wear of CNC lathe tools will directly affect the cutting quality and surface roughness during the cutting process. Severely worn tools on CNC lathes are prone to produce irregular surfaces and increase the roughness of the workpiece.

3. CNC program and path planning: The path planning and cutting strategy in the CNC program also have a great impact on the final roughness of the workpiece surface. Reasonable path planning and cutting strategies of CNC lathes can reduce vibration and impact, thereby improving surface quality.

4. Dynamic performance of machine tools: The dynamic performance of CNC lathes, such as rigidity, stability and shock absorption, are also very important for controlling the surface roughness of the workpiece. The more stable the CNC lathe is, the lower the surface roughness of the workpiece is usually.

5. Workpiece material properties: CNC lathes have different processing characteristics of different materials and respond differently to cutting force, cutting temperature and cutting vibration. Therefore, CNC lathes will affect the roughness of the workpiece surface.

6. Cooling and lubrication system: The performance of the CNC lathe cooling and lubrication system will affect the temperature and friction during the cutting process, which in turn affects the roughness of the workpiece surface. A good CNC lathe cooling and lubrication system can reduce cutting temperature and friction and help improve surface quality.

To sum up, the surface roughness of CNC lathe workpieces is affected by many factors, including tool selection, cutting parameters, CNC programs, machine tool performance, workpiece materials and cooling and lubrication systems. By rationally selecting cutting tools, optimizing cutting parameters, improving CNC programs, improving machine tool performance, and optimizing cooling and lubrication systems, the surface roughness of the workpiece can be effectively controlled and the accuracy of the workpiece improved.