In the processing of economical CNC machine tools, since the sharpening, measurement and replacement of tools are mostly done manually, which takes up a long time, 

the order of tool arrangement must be arranged reasonably. Generally, the following principles should be followed: ① Minimize the number of tools; ② After a tool is clamped, all processing steps that it can perform should be completed; ③ The tools for roughing and finishing should be used separately, even if they are tools of the 

same size; ④ Milling first and then drilling; ⑤ Surface finishing first, then two-dimensional contour finishing; ⑥ Where possible, the automatic tool change function of 

the CNC machine tool should be used as much as possible to improve production efficiency, etc.

Determination of cutting amount during processing

The principle of reasonable selection of cutting amount is: in roughing, the main focus is on improving productivity, but economy and processing cost should also be considered; in semi-finishing and finishing, cutting efficiency, economy and processing cost should be taken into account while ensuring processing quality. The specific value should be determined according to the machine tool manual, cutting amount manual, and combined with experience. The following factors should be considered specifically:

Cutting depth ap. When the rigidity of the machine tool, workpiece and tool allows, ap is equal to the machining allowance, which is an effective measure to improve productivity. In order to ensure the machining accuracy and surface roughness of the parts, a certain allowance should generally be left for finishing. The finishing 

allowance of CNC machine tools can be slightly smaller than that of ordinary machine tools.

Cutting width L. Generally, L is proportional to the tool diameter d and inversely proportional to the cutting depth. In the processing of economical CNC machine tools, the

general range of L is: L=(0.6～0.9)d.

Cutting speed V. Increasing V is also a measure to improve productivity, but v is closely related to tool durability. As v increases, tool durability drops sharply, so the choice 

of v mainly depends on tool durability. In addition, the cutting speed is also closely related to the processing material. For example, when milling alloy 30CrNi2MoVA with an end mill, v can be about 8m/min; when milling aluminum alloy with the same end mill, V can be selected to be more than 200m/min.

Spindle speed n (r/min). The spindle speed is generally selected according to the cutting speed v. The calculation formula is: V=pnd/1000. The control panel of the CNC machine tool is generally equipped with a spindle speed adjustment (multiplier) switch, which can adjust the spindle speed by integer multiples during the processing.

Feed speed Vf. vF should be selected according to the processing accuracy and surface roughness requirements of the parts as well as the tool and workpiece materials. The increase of Vf can also improve production efficiency. When the surface roughness requirements are low, Vf can be selected to be larger. During the processing, Vf can also be manually adjusted through the adjustment switch on the machine tool control panel, but the maximum feed speed is subject to the equipment stiffness and feed system performance.

With the widespread application of CNC machine tools in actual production and the formation of quantitative production lines, CNC programming has become one of the key issues in CNC processing. In the process of compiling CNC programs, it is necessary to select tools and determine cutting amounts in real time under human-computer interaction. Therefore, programmers must be familiar with the tool selection method and the principle of determining the cutting amount, so as to ensure the processing quality and efficiency of parts, give full play to the advantages of CNC machine tools, and improve the economic benefits and production level of the enterprise.