How To Choose The CNC Machining Cutting Amounts ?

- Mar 17, 2020-

Before CNC machining parts are processed, the CNC machining center equipment must be programmed.

The selection of cutting amount is a very key word, because this is an important process that directly determines whether the processed product is qualified. So how to choose the cutting amount of cnc machining?


cnc machining

(1) Determine the amount of back knife (mm)

The size of the back knife is mainly determined by the rigidity of the process system composed of machine tools, fixtures, tools and workpieces. When the system stiffness is agreed, in order to ensure that the machining allowance of the blank is removed with the minimum number of feeds, The allowance of the part determines the layered cutting depth, and a larger back-eating amount is selected to improve production efficiency. In numerical control machining, in order to ensure the necessary machining accuracy and surface roughness of the part, it is recommended to leave a small amount of allowance (0.2 to 0.5mm), and walk along the contour in the final finishing. In rough machining, in addition to leaving the necessary semi-finishing and finishing allowances, rough machining should be completed a minimum number of times under the conditions that the process system is rigid. The allowance for finishing should be greater than the amount of deformation of the part and ensure the surface integrity of the part.


(2) Determine the spindle speed n (r / min)

The spindle speed n is mainly determined according to the cutting speed VC (m / min) agreed by the tool:

Among them: VC——cutting speed.


d—Part or tool diameter (mm). Cutting speed VC is closely related to tool durability. With the increase of VC, the tool durability will decrease sharply, so the choice of VC mainly depends on the tool durability. After the spindle speed n is determined, it must be written into the CNC program in accordance with the format specified by the CNC machine control system. In actual operation, the operator can control the size of the spindle speed by appropriately adjusting the spindle speed override switch on the control panel of the CNC machine according to the actual processing conditions to determine the optimal spindle speed.


(3) Selection of feed amount or feed speed F (mm / r, mm / min)

The feed rate F is the relative displacement of the part and the milling cutter in the feed direction per unit time during cutting, and the unit is mm / r or mm / min.


When the feed amount F is selected when the cnc machining center is programming, the movement speed of the tool center is constant. When cutting in a straight line, the cutting point (cut point between the tool and the machining surface) is the feedrate given during programming. However, when performing arc cutting, the actual feed amount of the cutting point is not equal to the feed amount of the tool center selected during programming.


When programming a CNC machining center, the programmer must determine the cutting amount for each operation and write it into the program in the form of instructions. Cutting amount includes spindle speed, back-eating amount and feed speed. For different processing methods, different cutting rates need to be selected. In order to obtain the highest cutting parameters should be reasonably determined.


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