# Determination of cutting data in CNC machining

24 August 2021

The principle of reasonable selection of cutting dosage is that rough machining, generally to improve productivity, but also should consider the economy and processing costs; In semi-finishing and finishing, cutting efficiency, economy and processing cost should be taken into account on the premise of ensuring the processing quality. The specific value should be based on the machine tool manual, cutting manual, and combined with experience.

⑴ Cutting depth (T)

In the case of machine tool, workpiece and tool stiffness allowed, T 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 parts, a certain amount of allowance should be left for finishing. The finishing allowance of nc machine tools can be slightly less than that of ordinary machine tools.

⑵ Cutting width( L)

Generally L is proportional to the tool diameter D and inversely proportional to the cutting depth. In economic NC machining, the value range of L is generally: L= (0.6 ~ 0.9) d.

⑶ Cutting speed(V)

Improving V is also a measure to improve productivity, but V is closely related to tool durability. With the increase of V, tool durability decreases sharply, so the choice of V mainly depends on tool durability. In addition, the cutting speed and processing material also has a great relationship, such as the end milling cutter milling alloy just 30CrNi2MoVA, V can be used about 8m/min; And with the same end milling cutter milling aluminum alloy, V can choose more than 200m/min.

⑷ Spindle speed (n-r/min)

The spindle speed is generally selected according to the cutting speed V. The calculation formula is:

Where, D is the diameter of the tool or workpiece (mm).

CNC machine tool control panel is generally equipped with spindle speed adjustment (ratio) switch, can be in the process of machining spindle speed adjustment multiple.

⑸ Feed speed (VF)

VF shall be selected according to the machining accuracy and surface roughness requirements of the parts as well as the tool and workpiece material. Increasing vF can also improve production efficiency. Machining surface roughness requirements are low, vF can be selected to be larger. During machining, the vF can also be manually adjusted through the machine tool control panel repair switch, but the maximum feed speed is limited by equipment stiffness and feed system performance.