RU2779438C1 - Method and device for drilling a workpiece in an elastically stressed state. - Google Patents

Abstract

FIELD: mechanical engineering.

SUBSTANCE: invention relates to mechanical engineering and can be used for drilling holes. The workpiece is installed in a device with a conductor bushing. Subjected to elastic deformation by a load equal to the limit of proportionality of the workpiece material. Under the action of the hydraulic cylinder, the movable plate with the installed workpiece is brought together along the guides in the form of four columns to the fixed plate until the limit switches actuate. The drilling process is performed. After drilling, the force on the hydraulic cylinder is removed. The movable plate returns to its original position under the action of springs.

EFFECT: increases tool life.

2 cl, 3 dwg, 1 tbl, 1 ex

Description

The invention relates to mechanical engineering and can be used for drilling holes.

There is a known method of high-speed drilling and a device for its implementation, including the insertion of a cutting tool with a movably mounted drill bushing, giving it an axial feed (Patent RU, https://new.fips.ru/registers-doc-view/fips_servlet?DB=RUPAT&DocNumber=2534176&TypeFile =htmlC1, November 27, 2014, Bulletin No. 33).

The disadvantages of the known device is the low tool life.

The technical task is to increase tool life.

The technical problem is achieved due to the fact that the method of drilling a workpiece in an elastically stressed state consists in the fact that the workpiece is subjected to elastic deformation by a load equal to the proportionality limit of the workpiece material by installing the workpiece on a movable plate, which, under the action of a hydraulic cylinder, approaches along four columns, as if along guides. , to the fixed plate until the limit switches are activated, which are set to the size to create an elastically stressed state of the workpiece, after the end of the drilling process, the force on the hydraulic cylinder is removed, and the movable plate returns to its original position under the action of the springs.

The task is also achieved by the fact that the device for drilling the workpiece in an elastically stressed state consists of a base, which is mounted on the machine table, on which, in turn, four columns are fixed, a fixed plate and a movable plate are located on the columns, driven by a hydraulic cylinder, which is installed on a fixed plate, limit switches are also located on it, and a workpiece and springs are installed between the plates.

The technical essence and principle of operation of the proposed method and device are illustrated by the drawings of FIG. 1 which shows a diagram of a device for drilling a workpiece in an elastically stressed state, Fig. 2 - distribution in the workpiece of lines of maximum values of the main stress (MPa) at the initial moment of time, fig. 3 - distribution in the workpiece of lines of maximum values of the main stress (MPa) during drilling, at a depth of: a) 1.5 mm; b) 5 mm; c) 8 mm; d) 9.5 mm.

The method of drilling a workpiece in an elastically stressed state consists in the fact that the sample is subjected to elastic deformation by a load equal to the limit of proportionality of the workpiece material, that is, when the load is removed, the dimensions of the workpiece remain the same, and during processing the workpiece is in a stressed state, which helps to reduce cutting forces, spent on the destruction of the material in the cutting zone, which in turn increases tool life.

In this case, the device consists of a base 1, which is mounted on the machine table, on which four columns 2 are fixed, on which a movable plate 3 and a fixed plate 4 are located, driven by a hydraulic cylinder 5, while a workpiece is installed between the movable plate 3 and the fixed plate 4 6 under the replaceable conductor 7. When drilling, the movable plate 3 under the action of the hydraulic cylinder 5 approaches along four columns 2, as if along guides, to the fixed plate 4 until the limit switches 8 are activated, which are set to a size that allows creating an elastically stressed state of the workpiece 6. After the process drilling, the force on the hydraulic cylinder 5 is removed, and the movable plate 3 returns to its original position under the action of the springs 9.

The device operates as follows, the workpiece 6 is installed on the movable plate 3 and by means of the hydraulic cylinder 5 along the four guide columns 2 is pressed against the fixed plate 4, until the limit switches 8 actuate. equal to the limit of proportionality of the material of the workpiece, that is, when the load is removed, the dimensions of the workpiece remain the same, and during processing the workpiece is in a stressed state, which helps to reduce the cutting forces expended on the destruction of the material in the cutting zone, which in turn increases tool life. After removing the load, the workpiece is removed and the process is repeated again.

To describe the change in the zone of the preliminary elastically stressed state of the material being processed at different drilling depths, without taking into account the stresses created by the drill during operation, it was performed on the basis of modeling the process of drilling a through hole with a diameter of 3 mm in the DEFORM-3D finite element analysis environment. Aluminum alloy AL-3003 (AMts according to GOST 4784-97) was used as the workpiece material, the outer diameter of the workpiece and its height were taken equal to 10 mm. The elastically stressed state of the workpiece was carried out by moving the upper conductor plate down by 0.2 mm.

The figure 2 shows the distribution of lines of maximum values of the principal stresses (MPa) after the creation of a preliminary elastically stressed state in the workpiece material. The highest values of maximum principal stresses (>90 MPa) are achieved in the workpiece in the area of the conductor hole at a depth of up to 0.5 mm, where the drill will contact the workpiece during its insertion and subsequent work, as well as on the opposite side of the workpiece at the place of the future exit drill. Thus, it can be argued that by deforming the workpiece with a jig with a hole, it is possible to create a preliminary elastically stressed state of the material being processed at the initial stage in the processing zone.

The figure 3 shows the distribution in the workpiece lines of maximum values of principal stresses (MPa) at the drilling depth: 1.5; 5; 8 and 9.5 mm.

It can be seen that in the process of moving the drill into the depth of the workpiece, the zone of the highest values of the maximum principal stress, with a depth of up to 0.5 mm, will also move into the depth of the material and be located behind the surface of the bottom of the hole being formed. This is primarily due to the fact that the bottom of the hole, which has a conical shape, acts as a stress concentrator.

Based on the results obtained, it can be argued that when drilling holes of small diameter, the elastically stressed state of the material being processed will remain in the cutting zone throughout the entire processing time, ensuring a decrease in the axial component of the cutting force during drilling and thereby increasing tool life.

In order to study the effect of the preliminary elastically stressed state of workpieces made of non-ferrous metals and alloys on the durability of drills, a number of experiments were carried out, in which one group of drills drilled workpieces from L59 brass in the normal state, and another group of drills drilled in forgings after being created in the material. preliminary elastically stressed state. Drills with a diameter of 1.3 mm were used, the thickness of the blanks was 10 mm. Processing was carried out on a Wabeco CC-F1200 milling wall in the following modes: speed 2100 rpm; feed 100 mm/min (0.048 mm/rev). The durability of the drills was evaluated by the number of holes that the drill will process before it breaks.

The results of an experimental study of the effect of a preliminary elastically stressed state of workpieces made of non-ferrous metals and alloys on the durability of drills are shown in Table. one

Table 1
Results of the pilot study Without load With load #1 #2 Number 3 #1 #2 Number 3 9 ten ten fourteen fifteen fifteen

An analysis of the obtained data shows that the creation of a preliminary elastically stressed state when drilling holes in workpieces made of non-ferrous metals and alloys makes it possible to increase the durability of drills by an average of 50%.

This invention helps to reduce the cutting forces expended on the destruction of the material in the cutting zone, which in turn increases tool life.

Claims (2)

1. A method for drilling a workpiece in an elastically stressed state, including cutting a cutting tool with an installed conductor bushing, imparting axial feed to it, characterized in that the workpiece is subjected to elastic deformation by a load equal to the proportionality limit of the workpiece material by placing the workpiece on a movable plate, which, under the action of a hydraulic cylinder they are brought together along the guides in the form of four columns to the fixed plate until the limit switches are activated, which are set to the size to create an elastically stressed state of the workpiece, after the end of the drilling process, the force on the hydraulic cylinder is removed, and the movable plate is returned to its original position under the action of the springs. 2. A device for drilling a workpiece in an elastically stressed state, containing a cutting tool and a jig bushing, characterized in that it is equipped with a base, made with the possibility of mounting on the machine table and having four columns fixed on it, located on the columns with a fixed plate and a movable plate, a hydraulic cylinder , to actuate the movable plate, mounted on the base on the fixed plate, by limit switches located on the movable plate, and springs for returning the movable plate to its original position, installed between the movable plate and the base.

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