RU2243864C2 - Complex surfaces machining method - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention relates to machining of cellular fillers on five-coordinate numerically-controlled machine tools. Method comes to setting plane of rotation cutting tool at angle to surface to be machined. To improve accuracy owing to corresponding space orientation of cutting tool in process of machining of machining, alignment of axis of cutting tool with plane determined by straight line connecting point of touch with following support point and vector of normal to machined surface are provided by additionally turning axis of cutting tool around vector of its linear displacement. Disk cutter can be used as cutting tool.

EFFECT: improved accuracy of machining.

2 cl, 3 dwg

Description

The invention relates to mechanical processing and can be used mainly in the processing of light aggregates of complex shape in products of a multilayer honeycomb structure with a flat disk knife on five-coordinate machine tools with program control. The processed material is polystyrene, polymersotoplast, fiberglass, etc. Scope - machining of aircraft and helicopter parts.

A known method of horizontal volumetric processing of shaped surfaces with a milling cutter with an internal touch, which is continuously rotated relative to the longitudinal axis of the part by an angle determined from the condition that the radius of curvature of the processed cross section coincides with the radius of curvature of the cross section of the forming cylinder (see ed. Certificate No. 450657, V 23 From 3/16 for 1974).

This method is applicable only for a very limited class of parts having large curvature (aerodynamic models of aircraft assemblies, conoids, volumetric cams, turbine blades, etc.) and is not applicable for a large class of parts having small curvature and significant dimensions (for example, parts coming out on external bypass surfaces in the aircraft industry, stamping volumetric equipment, etc.).

A known method of milling concave shaped surfaces using cylindrical or disk cutters, in which the plane of the cutter is located at some constant or variable angle to the surface to be machined (see ed. Certificate. No. 132953, 49 5/05 for 1960).

This method is not accurate and makes it possible to obtain only an approximate shape of a concave surface.

The closest in technical essence is the method of processing complex surfaces with a face-mounted rotary cutter, which is informed of a longitudinal and periodic transverse feed with the installation of the cutter axis at an angle α to the surface to be machined, which is determined from the conditions for stabilizing the interline ridges (see ed. Certificate No. 1255303, B 23 C 3/16 for 1986).

The disadvantage of this method is the impossibility of processing complex surfaces having double curvature.

The present invention solves the problem of accurate shaping of complex surfaces having double curvature due to the corresponding spatial orientation of the cutting tool during processing, taking into account two angular coordinates.

To achieve this technical result, in a method for processing complex surfaces with a rotary cutting tool, including arranging the plane of the cutting tool at an angle α to the surface to be machined, an additional rotation of the axis of the cutting tool around its linear displacement vector by angle β is determined, which is determined relative to the perpendicular to the base plane of the part according to the formula

where A, B, C are the coefficients of the plane defined by the normal to the surface at the point of contact of the tool and the displacement vector, which are calculated from the equalities:

A = Cosβ ₁ Cosγ ₂ -Cosβ ₂ Cosγ ₁ ,

B = Cosα ₂ Cosγ ₁ -Cosα ₁ Cosγ ₂ ,

C = Cosα ₁ Cosβ ₂ -Cosα ₂ Cosβ ₁ ,

α ₁ , β ₁ , γ ₁ are the values of the angles that make up the normal vector to the workpiece at the point of contact of the tool with the axes X, Y and Z, respectively

α ₂ , β ₂ , γ ₂ are the values of the angles that make up the linear displacement vector with the X, Y, and Z axes, respectively.

The proposed method for processing complex surfaces is illustrated by the drawings shown in figures 1-3.

Figure 1 shows the position of a flat circular knife relative to the work surface at the moment of its contact with reference point A.

Figure 2 shows the position of the edge of the circular knife in the plane defined by the normal vector at point A and the straight line connecting the touch point with the subsequent reference point.

Figure 3 presents the cross-section MM in a plane perpendicular to the line that connects the point of tangency with the subsequent reference point.

In these drawings, the essence of the processing method is explained. When processing the surface of the part 1 (Fig. 1), a circular knife 2, rotating around axis 3, is moved along straight lines connecting the reference points C, A, B, etc. in series. according to route technology, with touching the edge of the disk knife 2 of each reference point (point A in figure 1). At each reference point (Fig. 2), the axis of rotation 3 is tilted by an angle α in the direction of movement relative to perpendicular 4 to the straight line 5 connecting the point of contact with the subsequent reference point, in the plane 6 defined by the indicated line and the normal vector 7 to the surface to be machined at the point A. Thus, the plane of the disk knife 2 will also be tilted at an angle α to the direct displacement 5. The directions of the normal vectors 7 and the direct displacement 5 are characterized by the values of the angles α ₁ , β ₁ , γ ₁ and α ₂ , β ₂ , γ ₂ , which these vectors form respectively with about X, Y, and Z (FIG. 1). In Fig. 3 (cross-section along MM), the axis of rotation 3 coincides with the trace of plane 6. Thus, the second angular coordinate of the axis of rotation of the tool will be determined by the angle between the trace of plane 6 and perpendicular 8 to the reference plane of the part.

When the disk knife moves to the next reference point, the linear coordinates of its center O and the angular coordinates of the axis of rotation 3 change in proportion to the change in the length of line 5.

In figure 2, the curve line 9 is the intersection of the plane 6 with the surface of the part 1. The distance between adjacent reference points determining the route of movement of the knife during processing is found from the condition of ensuring the necessary shaping accuracy, characterized by the deflection arrow δ between curve 9 and line 5.

The angle β is calculated using analytical geometry methods; the values of the direction cosines of the normal vector at the point of contact of the cutting tool with the surface of the part (Cosα ₁ , Cosβ ₁ , Cosγ ₁ ) are determined on the mathematical model of the part, and the values of the direction cosines of the unit displacement vector for the straight line AB are calculated by the formulas: Cosα ₂ = (X _B -X _A ) / S, Cosβ ₂ = (Y _B -Y _A ) / S, Cosγ ₂ = (Z _B -Z _A ) / S,

- длина прямой AB. Если точку A принять за начало системы координат, в которой X_A=0, У_A=О, Z_a=0, то уравнение плоскости, определяемой нормалью 7 и прямой 5, может быть записано в следующем виде:Where

- the length of the line AB. If point A is taken as the origin of the coordinate system in which X _A = 0, Y _A = 0, Z _a = 0, then the equation of the plane defined by normal 7 and line 5 can be written in the following form:

AX + BY + CZ = 0,

Where

The direction of the perpendicular to the reference plane usually coincides with the direction of the Z axis of the machine coordinate system; and for the Z axis, the values of the guide cosines are equal

The angle between the line and the plane is determined by the well-known formula

Substituting into this formula the values of the coefficients from equalities (1) and (2), we find from it the value of the angle β.

Based on the described processing method, software has been developed that performs automated preparation of programs for a five-coordinate machine with programmed control of the RFP-6, that is, it allows you to calculate the linear coordinates of the center and the angular coordinates of the axis of rotation of the disk knife, and form the knife movements taking into account the dynamic characteristics of the specified machine; while the gradual change in linear and angular coordinates during the transition to each subsequent reference point is performed by the control system of the machine "Neuron".

At the Kazan Aviation Production Association named after S.P. Gorbunov conducted industrial tests on the processing of compartments of parts included in the wing control system of the aircraft. The processing was carried out with a flat circular knife of diameter D = 50 mm with a constant angle of inclination of the end plane of the tool to the direction of movement α = 1 °. The spindle speed was 9000 rpm with a feed of 3000 mm / min. The permissible deviation from the theoretical surface was taken equal to δ = 0.02 mm, that is, it was equal to the discreteness of the positioning of the machine. Processing in these modes ensured high accuracy and good quality of the treated surface.

In the I quarter of 2003 at the Kazan Aviation Production Association. S.P. Gorbunov is scheduled to introduce the proposed method for processing complex surfaces.

Claims (2)

1. The method of processing complex surfaces with a rotating cutting tool, including the location of the plane of the cutting tool at an angle to the surface to be machined, characterized in that during the processing, the axis of the cutting tool is combined with the plane defined by the straight line connecting the touch point with the subsequent reference point and the normal vector to the machined surface, by additional rotation of the axis of the cutting tool around the vector of its linear movement. 2. The method according to claim 1, characterized in that as a cutting tool using a circular knife.

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