RU2412785C1 - Method of turning shaped surfaces - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: proposed method comprises turning the cutting tool about its axis. Said axis is displaced along trajectory formed by equal-length perpendiculars dropped from turning center to tangential line to turned surface at cutting tool apex point.

EFFECT: reduced roughness, uniform roughness over entire surface.

2 dwg, 1 ex

Description

The invention relates to the processing of materials by cutting and can be used in the processing of shaped surfaces of workpieces on lathes with high requirements for surface quality.

In the known method of turning external spherical surfaces according to the copyright certificate 1094671, B23B 5/40, published in 1983, BI No. 20, the processing is carried out with the rotation of the cutter around a given axis. The device comprises a transverse caliper and a rotary mechanism with a tool holder and a mechanism for moving it, mounted on a transverse caliper, the rotation mechanism being made in the form of circular guides in which the tool holder is mounted rotatably, the free end of which is provided with a finger interacting with its movement mechanism mounted on longitudinal support and made in the form of two elastically connected parts. This design of the device expands the technological capabilities of the method, since the axis of rotation of the cutter is perpendicular to the plane of the path of movement of the cutter and passes through the center of the processed sphere. However, when machining complex-profile surfaces other than spherical, the machining accuracy decreases sharply. In addition, due to a change in the kinematic principal angle in terms of φ, the roughness of the machined surface changes during processing. Also, the use of the device reduces the useful volume of the working field of the layout of the machine.

In the known method of machining shaped surfaces by turning according to RF patent No. 2266175 B23B 1/00, published in 2005, BI No. 35, adopted by the authors as a prototype, as the closest in its technical essence and the achieved effect, the method includes stabilization of temperature in the cutting zone moreover, temperature stabilization is carried out by changing the kinematic principal angle φ in plan by turning the cutter around an axis passing through the center of the radius section at its apex. In addition, the cutter is rotated together with the upper support of the machine.

The known method, compared with typical technological processes, can significantly increase the productivity of the process by changing the kinematic principal angle in terms of φ and stabilizing the temperature in the processing zone.

A significant disadvantage of this method is the large thermal inertia of the object, which limits the speed of the control system and reduces the quality of surface treatment. In addition, when the kinematic principal angle in terms of φ changes during the control process, the quality of the treated surface deteriorates.

The objective of the invention is to reduce the roughness of the processed surface of the workpiece and the creation of its equal value over the entire surface.

The problem is solved in that in the known method of machining shaped surfaces by turning with the rotation of the cutter around the axis, the axis of rotation of the cutter is moved along a path formed by perpendiculars of equal length, omitted from the center of rotation on a tangent to the surface being machined at the point where the tip of the cutter is located.

The invention is illustrated by drawings, where figure 1 shows a diagram of the processing of shaped surfaces on the workpiece; figure 2 - kinematics of the movement of the tool holder with a cutter.

The processing method is as follows: in the initial position, on the machine bed 1, there is a front headstock 2 with a spindle, in the cartridge 3 of which the workpiece 7 is fixed. A longitudinal support 4 is moved along the guides of the frame 1, along the guides of which the transverse support 5 is moved. Tool holder 6 with fixed the cutter 8 is installed on the axis C located on the transverse support 5, and rotates around this axis. The movement of the longitudinal support 4 and the transverse support 5 is transmitted by the engines 9, 10, respectively. The rotary movement of the tool holder 6 is transmitted by the engine 11. The engines 9, 10, 11 are controlled by a program control system 12.

The coordinate system of part 7 is denoted by X _∂ 0 _∂ Z _∂ , the coordinate system of the center of rotation of the tool holder 6 is X _p 0 _p Z _p . The top of the cutter 8 is located at point M and has the coordinates Z _kts and X _kts in the coordinate system of the center of rotation of the _{tool holder} 6. The center of rotation of the _{tool holder} 6 is at point C (0 _p ). Curve MM 'is the desired profile of the workpiece surface 7. The curve CC' is the trajectory of the center of rotation of the tool holder 6.

During processing, the tool holder 6 is rotated around the center C in proportion to the angle of inclination of the tangent profile of the part to the longitudinal axis 0 _∂ Z _∂ at a given processing point. Synchronously, it is linearly moved along the coordinate axes so that the tip of the cutter 8 always remains on the contour of the workpiece 7 and moves with a given constant contour speed.

To process the workpiece 7 installed in the chuck 3 of the spindle of the headstock 2 on the bed 1, the control system 12 enters: the values of the contour processing speed, the geometric parameters of the workpiece profile - curve MM ', the position of the tip of the cutter 8 in the coordinate system of the tool _holder 6 - Z _kts and X _kts . Based on these data, the control system calculates the trajectory of the tool holder 6 — curve CC ', the speed of the tool holder 6 in linear coordinates, the rotation angles and the angular speed of the tool holder 6. During processing of the workpiece, the control system 12 gives signals to the engines 9, 10, 11, which transmit the movement to the longitudinal support 4, the transverse support 5 and the tool holder 6, respectively. As a result of the complex movement of the tool holder 6 along the path CC ', the tip of the cutter 8 will move along the path MM'.

As a rule, in areas with different angle of inclination of the profile, the allowance is not the same. When using the prototype method, this leads to a change in temperature in the processing zone. The system reacts to a change in temperature by changing the kinematic principal angle in the plan. Changing the angle in turn leads to a change in surface roughness along the machined contour. In the proposed method, the magnitude of the main angle in the plan does not depend on the temperature in the cutting and stock zone, and therefore remains constant, which leads to a constant roughness on the entire contour of the surface being machined.

An example of the method

A batch of blanks of 10 pieces was processed. The blanks had a cylindrical and conical surface. A cylindrical surface with a length of 50 mm and a diameter of 88.2 mm was mated with a conical surface with a length of 40 mm, the angle of inclination of the generatrix of the cone to the axis of the part was 145 °. Processing of blanks was carried out on a CNC lathe.

The workpiece material is 30G steel.

Tool: cutter with replaceable plate. The plate has a trihedral shape, with an apex angle of 60 °. Plate material - T30K4 alloy.

Geometrical parameters of the cutter:

- the main angle in the plan is 75 °;

- auxiliary angle in the plan - 45 °;

- back angle - 8 °;

- rake angle - 15 °;

- the shape of the front surface is flat with a bevel;

- bevel width along the main cutting blade - 0.3 mm;

- the radius of the rounding of the cutting edge is 0.03 mm;

- the radius of the tip of the cutter is 1 mm.

Cutting modes:

- cutting speed - 200 m / min;

- feed - 0.11 mm / rev.

The size of the removed allowance is 0.4 mm.

The obtained parts had a roughness on the cylindrical surface on average Ra = 1.6 μm. On the conical surface, the roughness varied on average from Ra = 1.6 μm to Ra = 1.8 μm.

Thus, the roughness in the present method is more stable and less than in the prototype.

Claims (1)

A method of machining shaped surfaces by turning, including turning the cutter about an axis, characterized in that the axis of rotation of the cutter is moved along a path formed by perpendiculars of equal length, omitted from the center of rotation on a tangent to the surface being machined at the point where the tip of the cutter is located.

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