RU2298458C1 - Method for milling screws with round screw surface at small distance between apex and recess - Google Patents

Abstract

FIELD: machine engineering, working screws of screw pumps of hard-to-form materials.

SUBSTANCE: method is realized with use of tool such as milling cutters. Milling cutter is subjected to independent rotation around its own axis and blank is subjected to rotation matched with lengthwise feed of tool equal to pitch of worked screw. In order to enlarge manufacturing possibilities and to enhance working accuracy, tool in the form of set including three equally spaced one from other in cross plane shaped milling cutters and mutually spaced in axial direction by distance equal to 1/3 of pitch. Rotation axes of milling cutters are inclined relative to blank axis by angle equal to leading angle of screw surface turns. Milling cutters may have separate drive units or common drive unit.

EFFECT: enlarged manufacturing possibilities, enhanced working accuracy.

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Description

The invention relates to mechanical engineering in the field of machine tool engineering and mechanical engineering technology, can be used in the processing of milling of screw surfaces of the screws of screw pumps from difficult to process materials.

A known method of cutting cylindrical worms with disk cutters, in which the cutter is set so that its axis of rotation is inclined by the angle of elevation of the turn of the worm, and the midpoint is located at the same height as the axis of the worm [1, 2]. With this installation of the cutter, the worm is profiled in a normal section along the cavity.

Significant disadvantages of this method are low productivity in the manufacture of long screws and poor accuracy due to the unilateral action of the cutting forces and the large deflection of non-rigid long screws.

The objective of the proposed method for milling screws with a round helical surface with a large pitch and a small distance between the top and the bottom is to expand technological capabilities, increase process productivity through the use of a tool kit consisting of three disk shaped cutters, and increase the accuracy of processing and profiling due to the fact that A set of three cutters, evenly spaced in the circumferential direction, is a lunette.

The problem is solved by the proposed method of milling screws with a round helical surface with a large pitch and a small distance between the top and bottom of the shaped milling cutters, in which the milling cutter informs independent rotation about its own axis, and the workpiece is rotationally adjusted, consistent with the longitudinal feed of the tool, equal to the pitch of the machined screw moreover, the processing is carried out simultaneously by a set of tools consisting of three shaped mills and uds equally spaced from each other in the transverse plane axially separated from each other at a distance of one third of the step, and the axis of rotation of the cutters are located at an angle to the axis of the workpiece, equal to the angle of elevation of the turns of the screw surface, while the cutters have an independent individual or common drive.

The essence of the method is illustrated by drawings.

Figure 1 presents a diagram of the implementation of the proposed method on a lathe; figure 2 is a diagram of the relative position of the cutters and the workpiece screw, cross section aa in figure 1.

The proposed method is intended for milling of screws 1 with a round helical surface with a large pitch and a small distance between the top and bottom of the shaped cutters 2, in particular, for processing screws of the screw pumps EVN5-25-1500 oil wells, which have the following dimensions: total length 1282 mm , the length of the screw part is 1208 mm, the cross-sectional diameter of the screw is ⌀27 ^-0.05 mm, the eccentricity e ₁ = 1.65 mm, e = 3.3 mm, the pitch t = 28 ^{± 0.01} mm (Fig. 1) .

The tool - disk shaped milling cutter 2 - informs independent rotation with a frequency of V _and relative to its own axis, and the workpiece is rotational movement with a frequency of V _s consistent with the longitudinal feed S _pr tool equal to the pitch t of the machined screw.

Processing is carried out simultaneously by a set of tools consisting of three shaped milling cutters 2 equally spaced from each other in the transverse plane and axially spaced apart from each other at a distance t / 3 - one third of the step, where t is the pitch of the screw being machined, mm.

The axis of rotation of the milling cutters 2 are located at an angle α _Ф to the axis of the workpiece 1, equal to the angle α _{in the} lifting of the turns of the screw surface, t, e. α _Ф = α _century The cutters have an independent individual or general drive and are mounted in a special head 3.

Processing according to the proposed method is carried out on a lathe using the above-described head, which is installed instead of the tool holder on the transverse support, as follows. The screw blank with pre-machined base surfaces is installed in a three-jaw self-centering chuck 4 in spindle 5 of the headstock 6 of the machine. A free end face the workpiece is introduced into the Central hole of the head and is pressed by the center 7 of the tailstock 8, while the cutters in the head are radially separated. Turns on the rotational movement of the spindle with a frequency of V _s , the rotational movement of the milling cutters with a frequency of V _and gives a radial feed S _p , with each mill being set to a cutting depth of h / 3, where h is the total allowance left for milling taking into account the distance between the top and bottom of the helical surface. Dividing the total allowance into three tools allows you to evenly load each tool and exert equal forces of the impact of the cutters on a non-rigid workpiece. After each cutter is set to its depth, the longitudinal feed S _ol equal to

S _ol = t mm / rev

where t is the pitch of the machined screw, mm

Thus, the accuracy of processing and profiling is increased due to the fact that the head in a set of three cutters arranged uniformly in the circumferential direction is a movable lunette.

Example. The left screw H41.1016.01.001 of the screw pump EVN5-25-1500 was processed, which has the following dimensions: total length 1282 mm, length of the screw part 1208 mm, screw cross-section diameter ⌀27 ^-0.05 mm, eccentricity e ₁ = 1, 65 mm, e = 3.3 mm, pitch t = 28 ^{± 0.01} mm, roughness R _a = 3.2 μm; single-helical screw surface, left direction; material - steel 18HGT GOST 4543-74, hardness HB 207-228, weight 5.8 kg. The allowance on the side for subsequent grinding 0.25 mm. Billet - hot-rolled round steel (GOST 2590-71) with a diameter of 34 mm. Processing was carried out on a modernized mod screw-cutting lathe. 16K20, the milling head with a tool mounted on a support, a three-disk shaped cutters of R6M5 material, the width of cutters B ₌ = 32 mm, diameter 50 mm cutters, cutter speed V _u = 31.42 m / min, n = 200 _and rev / min, the circumferential speed _of the workpiece V = 320 mm / min, n _s = 3.8 / min, traverse Snp = 28 mm / v, the inclination angle α of the screw surface coil _in = 24 ° 48 ', the required accuracy of the screw the surface was reached after T _m = 12.2 min (against T _m ^bases = 36.5 min according to the base case with traditional turning with a cutter on a modernized lathe 1K62 at JSC Liveg idromash "). The control was carried out by an indicator bracket with an indicator ICh 10 B cells. 1 GOST 577-68. The accumulated error between any non-adjacent steps was not more than 0.1 mm, the clearance during the control by the straightedge of the protrusions forming in diameter was not more than 0.4 mm, which is permissible according to the technical specifications for preliminary processing.

Thanks to the application of the proposed method of milling screws with a round helical surface with a large pitch and a small distance between the top and bottom, the technological capabilities have expanded, the process productivity has increased due to the use of a tool kit consisting of three disk shaped mills, and the accuracy of processing and profiling has increased due to the fact that a set of three cutters, evenly distributed in the circumferential direction, is a lunette, and the tool life has also increased.

Information sources

1. Danilevsky V.V. Engineering Technology: Textbook for technical schools. - 5th ed., Revised. and add. - M., Higher. school., 1984. - S.290-292, Fig. 224 - prototype.

2. Engineering technology (special part). M., Mechanical Engineering. 1973. P.360, Fig. 185.

Claims (1)

A method of milling screws with a round helical surface with a large pitch and a small distance between the tip and the trough of the tool in the form of milling cutters, in which the milling cutter informs independent rotation about its own axis, and the workpiece rotational movement consistent with the longitudinal feed of the tool equal to the pitch of the machined screw, characterized in that they use the tool in the form of a kit consisting of three shaped mills equally spaced from each other in the transverse plane and axially spaced from each other and at a distance of one third of the step, and the axis of rotation of the cutters are located at an angle to the axis of the workpiece, equal to the angle of elevation of the turns of the screw surface, while the cutters have an independent individual or common drive, and they are machined simultaneously.

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