SU1757801A2 - Method of machining helical surfaces - Google Patents

Abstract

Usage: machining blade products, in particular, propellers, turbines, etc. SUMMARY OF THE INVENTION: The treatment of the helical surface of the blade is carried out by a rotating tool, profiled along the radius, by longitudinal lines. The tool is informed about the rotation with variable frequency and the feed movement along the generatrix of the screw surface with variable speed based on the condition of the cutting speed stabilized. The rotational speed of the tool is determined from a mathematical expression. 2 Il.

Description

The proposed method relates to the machining of blades, for example, propellers, turbines and the like. and is an improvement of the method of processing the screw surfaces of the blades: along. CCCPtvfe 1180241. According to this method, the processing is carried out by longitudinal lines of a radially shaped cutting tool. During processing, the circle is moved in a plane passing through the axis of the product and forming the screw surface of the blade to be machined, and the part is moved in the direction of the circle and rotated around its axis (1).

The disadvantage of the known method is that during the machining process the cutting speed changes continuously, since the tool contacts the blade with points on its working surface located at different radii from its axis of rotation. Due to this drawback, machining is not possible at optimum cutting conditions, which negatively affects the productivity and quality of processing. This disadvantage is increasingly manifested as the diameter of the tool decreases.

The purpose of this proposal is to eliminate the noted deficiency, i.e. increase in productivity and quality of processing due to stabilization of cutting speed. -;WITH :,,.-.:- /-; ; :

This goal is achieved by the fact that, in contrast to the known method, the frequency of rotation of the tool is determined from the relation

   - u. : / .-: -. -

Lt

2 l (g cos arctg - + y - g cos ymin)

where n is the frequency of rotation of the tool; V- cutting speed; H - pitch of the helical surface of the blade; . D is the diameter of the tool;

P -

Vj

SL VJ 00 About

.Yu

R is the distance between the axis of the screw surface and the tool;

g is the tool profiling radius;

h is the tool width;

Ut1p - the minimum angle of elevation of the helix bounding the surface of the blade.

The tool feed is carried out at a variable speed proportional to the frequency of its rotation.

Figure 1 shows the processing scheme, figure 2 - shows the interaction of the tool with different parts of the screw surface of the blade.

A blade 1, for example, a propeller, processes the mode with a tool 2 (a mill, a grinding wheel), the axis 3 of which is crossed at a right angle with the axis 4 of the screw surface. The working surface of the instrument is shaped along the radius g (Fig. 2), the magnitude of which is given according to the information from A.S. № 1180241 dependencies

 hm

Sin Ears-Sin ymin l

where h is the width of the tool; Utah and ut | P are the maximum and minimum angles of elevation of the screw lines bounding the surface of the blade and remote from the axis 4, respectively, at Rmin and Rmax.

The blades are processed by longitudinal lines, for which the tool is told to move S along the screw surface forming 5 and displaced along the axis 4 displaced with it. To go to each subsequent line, the blade is rotated by -4 width around axis 4.

When moving tool 2 along generatrix 5, the distance R from axis 3 continuously changes to the point of contact of the working surface of the tool with the blade, since the elevation angles of the helical lines of the surface are different and are in the range ymjn. Therefore, to stabilize the cutting speed, the rotation frequency of the tool change and set, depending on the current value of the distance R between the axes of the screw surface and the tool by the ratio

V,

H d

2 l: (g cos arctg jjTR + 2 g cos mln

(2)

where V is the cutting speed; H - pitch of the helical surface of the blade;

P

D is the diameter of the tool;

R is the distance between the axis of the screw surface and the tool;

g - radius of the grinding wheel profiling;

h is the tool width;

Corners. ymin, respectively, the maximum and minimum angles of elevation of the screw lines bounding the surface of the blade to be machined.

Dependence (2) is obtained as follows. The frequency n of the rotation of the instrument is determined by the relation

n TYAR 0)

where V is the cutting speed; p - the current value of the radius of the instrument at its point of contact with the blade (helix, having an angle of inclination y). From figure 2

p G -SOP + S-GNSS. (4)

where r is the tool profile radius, defined by expression (1); D is the diameter of the tool;

Ushsh - the minimum angle of inclination of the helix of the helical surface distant from the axis 4 to the distance Rmax,

for arctg N / 2 and R (5) is the angle of inclination of the helix, remote from axis 4 to distance R, with which the cutting tool contacts at the considered time instant;

H - pitch of the helical surface of the blade.

Based on the dependence (3) - (5), the relation (2) takes place.

The tool is fed along the generatrix of the screw surface with a variable speed Vs proportional to the frequency n of its rotation:

V, -S0-n, (6)

where So is the feed per one revolution of the tool.

Improving the quality of processing is achieved by maintaining a constant value of the cutting speed when machining the entire surface.

Since the stabilization of the cutting speed

carried out by continuously increasing the tool rotation frequency, it is possible to proportionally increase the feed rate, thereby achieving an increase in

performance.

Claims (1)

The invention of the method of processing the screw surfaces of the blades on add.st. No. 1180241, characterized in that, in order to increase productivity and quality of processing by stabilizing the cutting speed, the frequency and the rotation of the tool are determined from the relation: P V TG Bg 2 l (g cos arctg - + - g cos ymm) where n is the frequency of rotation of the tool; V - cutting speed; LX H - pitch of the helical surface of the blade; D is the diameter of the tool; R is the distance between the axis of the screw surface and the tool; g - tool profiling radius; h is the tool width; ymin is the minimum elevation angle of the helix bounding the machined surface of the blade.