SU1400794A1 - Method of working deep holes - Google Patents

Abstract

The invention relates to metal cutting and can be used when drilling deep holes. The aim of the invention is to improve the accuracy of processing. The first hole with a length of 1 with a drill of diameter D is drilled from the face 1 of the part. Then, a hole with a diameter d is drilled from the same face by a length 1. As a result of processing errors, the hole axis is displaced from the nominal position by ij. Having turned the part, the second hole is drilled on the side of the end 2 with a drill of diameter D before meeting the smaller step 1. At the same time, the axis of the second hole is shifted by the value of J. The displacement of the axes of the parts of the holes causes an unbalanced radial force acting on the working part of the drill, which causes its elastic deformation and, consequently, the displacement of the axis of the hole in section 1 during its drilling. The drilling of a hole of a smaller step is carried out when the feeding tool is informed of a certain value. 2 hp f-ly, 4 ill. From "SP"

Description

I

About CO 4

t

 ;

The invention relates to metal cutting and can be used when drilling deep holes.

The purpose of the invention is to improve the accuracy of processing.

FIG. 1 shows a scheme for implementing the method; in FIG. 2, node I in FIG. one; in fig. 3 - diagram of loading NIN drills when reaming a hole step of a smaller diameter; FIG. 4 is a diagram of drilling a hole of a smaller diameter.

It is necessary to drill a deep hole (lo / D 7 10) with a length of 1 ° and a diameter of 1). In this case, it is necessary to ensure the alignment of the inlet and outlet parts of the hole and the straightness of the axis within Е (mm) per 1 mm of the hole length.

To do this, first drill a part of a hole of length 1, with a drill of diameter D (Fig. 1a) on the side of output end 1. Then drill a part of the hole with a drill of diameter d (d D) for a length. (Fig. 1b). A two-stage hole can be made within one transition using a two-stage drill (Fig. 1B).

Due to various errors occurring during processing (for example, inaccuracies of the tool, tool and other elements), the axis of the hole is shifted (withdrawn) from the nominal position by a certain quantity l (Fig. 15, c). Drilling can be carried out both on a core bushing and on the marking.

Turning over the part, the hole is drilled on the side of end 2 with a diameter D drill until they meet section 1 of a smaller stage. By the time the tool encounters a hole of a smaller step (Fig. 1d), the axis of the hole D with a length of 1 1 is also shifted by some value d. The greatest displacement of the axes of the parts of the holes encountered is ANL L uq. The permissible relative displacement of the axes of the parts of the hole causes the presence of an unbalanced radial force acting on the working part of the drill, which causes its elastic deformation, and consequently, the displacement of the axis of the hole in section 1. The loading diagram ffi; t: eT PiiJTb is presented as

beams, one end of which is cantilevered and the other loaded with an unbalanced radial force (Fig. 2a, on the loaded end side there is an additional support, spaced apart from C, which is explained by the support of the drill on the machined surface.

The support of the drill on the surface of the machined hole is determined by the base of the screw ribbons under the action of the unbalanced radial force Py; this is the resultant unbalanced radial and tangential components of the cutting force. Taking into account the direction of this force, LRu with respect to the plane in which the cutting edges lie (Fig. 2b) and the angle of inclination of the ribbons determine that the ribbing of the ribbons on the processed surface occurs at a distance C not exceeding 1-1.5 drill diameter. With 7 (1-1,5) D.

In the process of drilling a hole with a diameter d by a tool 3 with a diameter D, the axis of the tool 3 is offset relative to the axis of the hole d by the value yy (Fig. 3a). Denote the position of the axis of the hole d with respect to the axis of the hole D as у „(t), and the radial forces acting on the cutting edges, P and P.

Let us take the simplifying assumption that the radial forces P and P are proportional to the area of the cuts:

Р, К.4,, PJ K-d,,

where l and l square cuts;

K - coefficient of proportionality of the radial force of the area of the slice. As can be seen from FIG. Behind

D, S / 2. h ;; hi D / 2 -d / 2 + y (t);

U1 S / 2 h -I D / 2 -d / 2 - yo (t),

where S is the axial feed of the tool 3

in one turn.

Equilibrium equation of instrument 3 can be written as

P, - K,) - yjt-c) - P-I,

TO

vnp

the radial rigidity of the tool for the circuit shown in FIG. 2a, and

Wnp

- 1 to

(2)

. k - 3 EI

P -0 ()

where I is the moment of inertia of the drill;

P - single radial force. Substituting in the equilibrium equation. The values of P, and P, get

).

one

1 +

KS

to

apr

The resulting expression shows that the distance during drilling, the distance C drill 3 is displaced in this area (and consequently, the axis of the hole D is displaced) by YpCt- -) - Wo (b) and the magnitude of the displacement depends on the magnitude of

. one

1 +

those. from parameters that can be controlled.

Thus, taken in as initial conditions

- 1 -it -0;

Uo () nd y,

It is possible to determine when K p S and K are known, what should be the length 1 of the smaller step d, which will make it possible to achieve coincidence of the axes of the parts of the hole when drilling this step. To ensure a given straightness in the area of the length of the smaller step, the condition can be satisfied

y, (t-) - yo (t).,

and since yo () & y (at the beginning of drilling, fig. 3b), and yo (t)

 yc (t-c) -

1 +

K S

TO

You can then determine the tool feed to ensure the specified condition:

ten

15

When communicating to the feed tool, determined from relation (2), a predetermined value of the rectilinear axis is ensured during reaming. Thus, the drilling of section 1 can be represented as a gradual approximation of the axis of the hole being drilled to the axis of the stepped hole (Fig. Sv), that is, to the axis of the hole d.

The length of 1 hole at the same time

is done as 1T

Where

20

P

g Sy

25

It can be seen from formula (1) that at constant S, k and kf, every i decrease occurs every time by an ever smaller value. It follows from this that it is possible (if the equipment permits) in the first segment to inform the instrument of the flow

35

- J) -K

in the second section of length 1

40

TO

S.

vrrp

etc.

For the t-th plot

45

(3)

- t)

where m 1, 2, 3, ...

The length of the smaller steps

at

is defined as 17 / -C,

Taking into account the above, it can be said that during the drilling of a smaller step, it is possible to stepwise increase the feed, determined it according to the formula (3), which allows to increase the productivity of processing and reduce the .1 lower stage

When drilling a smaller step in real conditions with a tool that has auxiliary cutting edges and a small auxiliary plan angle (close to O), shown in FIG. There are no separate sections of length f, having a difference of one relative to another, the transition from one section to another is smoother, so. how they are partially trimmed with an auxiliary cutting edge (for example, when using a spiral drill).

Passing thus a portion 1 with a diameter d (fig. 3), the tool 3 goes into a hole with a diameter D, and the axes of the occurring holes coincide. The processing of the hole ends there.

The diameter of the lower stage d must be chosen from the condition

2-4y + f d rD-4y, (A)

where f is the jumper length of the tool 3 (Fig. 1g, usually does not exceed (0.1-0.3) D).

Claims (3)

Invention Formula i c. A method for processing deep holes in which a first hole is pre-drilled with a tool rotating and axially moving from one end of a part, and then a second hole is drilled with a tool whose diameter is related to the diameter of the first hole from the other end of the part to align with the first hole characterized in that, in order to increase the machining accuracy, the first hole is made two-step, and after combining the tool forming the second hole with the step of the first hole, and the smaller diameter is drilled, the holes of the said step are drilled, the diameter d los; 1 week is determined by the following relation 2 yu + (0.1 ... 0.3) D d D - ay, where D is the diameter of the hole of a greater degree; / 5 y - the maximum allowable relative displacement of the axes of the first and second holes. 2. A method according to Claim 1, characterized in that when reaming a hole of a smaller diameter, the axial flow of the tool S is limited by the following relationship: SM ".C control (-.).to - radial rigidity of the tool;  tolerance of the straightness of the axis of the hole, referred to the unit of length; - distance from the tip of the cutting edge to the base point of the tool on the machined surface; - proportionality factor of the radial cutting force to the area of the cutting layer, the steps of the smaller hole are chosen according to the following Where P 3. A method according to claim 1, characterized in that when reaming a hole of a smaller diameter, the axial feed of the tool is increased stepwise, the feed rate at each step Sfp is determined from the following relationship: TO vnp where t 1, 2, 3, ..., and the length of the 1-stage hole of a smaller diameter is chosen according to the following relationship: one li .2 Dptsvmmg Fiz.Z Fy