Cutting speed for milling, turning and other types of machining of parts

Calculation of cutting modes is the most important stage in the manufacture of any part. It is very important that it be rational. This is due to the fact that for different mechanical operations it is necessary to individually select the cutting speed, the spindle rotation frequency, the feed amount, and the thickness of the layer to be removed. Rational mode - this is such, during which the cost of production will be minimal, and the quality of the product - the most accurate.

Basic principles of calculations

In order to manufacture a part with the necessary dimensions and accuracy class, first of all execute its drawing and paint the route technology. In addition, it is very important to choose the right workpiece (forging, stamping, rolling) and the necessary material from which the product will be manufactured. Choosing a cutting tool is also a very important task. For each individual operation, the required tool (cutter, milling cutter, drill bit, countersink) is selected.

In addition, for each item written in the routing technology, a separate process is performed, even if it is applied to the same work surface. For example, you need to make a hole D = 80 mm and cut the internal metric thread in increments of P = 2 mm. For each of the operations, it is necessary to select separately such values as cutting depth, cutting speed, speed, and also to select the cutting tool.

Required surface quality

It is important to take into account also the type of processing (finishing, roughing and semi-finishing), because the choice of coefficients in the calculations depends on these parameters. As a rule, during the roughing, the cutting speed is much greater than in the finishing. This is explained in this way: the better the quality of the surface being treated, the less should be its speed. Interestingly, when turning titanium alloys, the roughness value increases at high exponents, since strong oscillations appear in the treatment zone, but it does not affect the parameters Ra and Rz at all.

Factors affecting the cutting speed during milling and other operations

A large number of factors influence the choice of calculations. All of them differ among themselves depending on the type of workpiece processing. For example, for drilling holes, you can select a feed twice as much as for drilling. In addition, this parameter, when processed without limiting factors, is chosen to be the maximum permissible, according to the strength of the tool used. _. When planing and cutting through the grooves, a coefficient is added to the basic formula of the cutting regime, which takes into account the impact load - K _{v .}

When tapping, it is very important to pay attention to the selection of the cutting tool, since using the cutter at the stop requires a manual retraction, and hence the speed should be minimal.

The cutting speed for milling depends on the diameter of the tool (D) and the width of the surface (B). Moreover, when machining steel surfaces with end mills, it is necessary to place the workpiece asymmetrically relative to the cutting tool. If you ignore this rule, then its resistance can be significantly reduced.

This is a very important indicator that affects the calculation of the cutting speed. It indicates the period of operation of the cutting tool prior to its blunting. The period of durability is increased with multi-tool processing.

Basic Formulas

The cutting speed for any operation primarily depends on the selected cutting tool, the material of the workpiece, the depth and the amount of feed. Its formula is influenced by the way of machining. The cutting speed can be determined either by a tabular method or by calculation. Thus, for boring, as well as for external, transverse and longitudinal turning, the following formula is used.

How does this calculation differ from the rest? When cutting, cutting and cutting, the depth of cut is not taken into account. But in some cases, such a value as the width of the slot can also be taken. For example, when the shaft is treated with a width, its diameter will be considered, and when the groove is turned, its depth will be considered. Due to the fact that it is quite difficult to cut the cutter at cutting, the feedrate is selected no more than 0.2 mm / rev, and the cutting speed is 10-30 mm / min. You can also calculate by another formula.

When drilling, reaming, reaming and deploying it is very important to determine the cutting speed and feed rate correctly. If the values are too large, the cutting tool may "burn" or break. For calculations during drilling, the formula given below is used.

The cutting speed for milling depends on the diameter of the cutter, the number of teeth and the width of the machined surface. The depth to be chosen is determined by the rigidity and power of the machine, as well as the allowances on the side. The value of the resistance of the mill depends on its diameter. So, if D = 40-50 mm, then T = 120 minutes. And when D is in the range of 55-125 mm, the T value is 180 minutes. The cutting speed for milling has the formula shown in the photo.

Notation:

C _v - coefficient, which depends on the mechanical properties of the surface being treated.

T - resistance of the cutting tool.

S is the feed amount.

T is the depth of cut.

B - width of milling

Z - number of teeth of the cutter.

D is the diameter of the machined hole (in some cases, the cutting tool, for example, a drill)

M, x, y are the exponents (selected from the tables), which are determined for the specific cutting conditions and, as a rule, have the values m = 0.2; X = 0.1; Y = 0.4.

K _v is the correction factor. It is necessary, since the calculations are carried out using the coefficients taken from the tables. Its use makes it possible to obtain the actual value of the cutting speed taking into account certain values of the factors mentioned above.

Table and program method

Since the calculations are a laborious process, there are special tables in specialized literature and on various Internet resources, in which the necessary parameters are already indicated. In addition, there are programs that themselves perform the calculation of cutting modes. For this purpose, the required type of machining is selected and parameters such as workpiece and cutting tool material, necessary dimensions, depth, accuracy classifications are entered. The program itself calculates the cutting speed for turning, feed and speed.