RU2824782C1 - Feed drive of milling machine for processing waffle shell structure - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: feed drive of milling machine for processing of waffle structure of shell contains transfer lever crank-slider mechanism. Crank of the lever transmission mechanism is made in the form of a crankshaft with two connecting rod journals with detachable heads of two identical connecting rods hinged to them, opposite non-detachable heads are pivotally connected to slides, one of which is working, and the second one serves for balancing and reduction of action of centrifugal forces created by crank.

EFFECT: enabling reduction of time for processing of rectangular pattern of waffle background cells due to multiple increase of feed rate along one coordinate.

1 cl, 3 dwg

Description

The invention relates to the field of mechanical processing of rectangular cell patterns on thin-walled body products on CNC milling machines.

When processing the waffle background, milling machines are used that implement various strategies of software-copying processing [Tyulevin S. V., Kotov A. N., Korotkov A. N., Kovalev A. M. Horizontal multi-spindle milling machine / patent RU 2465104, IPC B23C3/04, patent publication: 10/27/2012, application filing: 10/26/2011. http://www.freepatent.ru/patents/2465104 (date of access: 08/30/2023); Kotov A. N., Chuikin S. A., Milekhin E. S., Makarov Yu. N., Korotkov A. N., Volodina S. A. Metalworking machine / patent RU 2397049 IPC B23C3/00, patent publication: 20.08.2010, application filing: 29.01.2009. https://findpatent.ru/patent/239/2397049.html (accessed: 30.08.2023)]. Traditionally, ball screw transmission is used in machine tools in cutting tool feed drives.

Disadvantages: the feed drives of the machines under consideration have a significant mass, and as a consequence, inertia when moving in short sections, which is a limiting factor during high-speed processing, preventing the nominal feed and cutting speed values from being reached for the given overall dimensions of the wafer background cell. The use of ball screw transmissions in feed drives when processing wafer background cells leads to rapid depletion of the resource when moving in a narrow range. As a consequence, to a decrease in productivity and accuracy of the technological operation, as well as to significant dynamic loads on the moving units of the machine in the acceleration and braking section.

Lever transmissions based on flat four-link crank-slider mechanisms are rarely used as feed drives in metal-cutting machines, since the output link of the lever transmission, with uniform rotational movement of the crank, performs a rectilinear reciprocating motion with variable speed, and at the upper (TDC) and lower (BDC) dead points in one of the joints of the intermediate link - the connecting rod, an "explosive" increase in forces is observed.

Disadvantages: The connecting rod attached to the crank journal describes a large trajectory in a plane perpendicular to the axis passing through the top dead center (TDC) and bottom dead center (BDC), which causes a strong impact of the lateral force from the reactive torque pressing the slider to the fixed guides and high friction. This reduces the efficiency and leads to rapid wear of the mating links of the mechanism.

The closest analogue is a drive in the form of a crank-slider mechanism with a reciprocating motion of the slider and with an adjustable stroke length of the slider with the mechanism running and stopped [Gryanin V.I. drive with an adjustable stroke length of the slider with the mechanism running and stopped / patent RU 71719, IPC F16H21/20, patent publication: 20.03.2008, application filing: 30.07.2007. http://www.freepatent.ru/patents/71719 (date of access: 30.08.2023)].

The specified drive is a prototype of the proposed invention.

The drive comprises in the housing a driving worm on bearing supports, connected to the drive motor, a driven worm wheel, the hub of which is mounted on a bearing support, a crank shaft, one end of which is placed in a cylindrical hole of the hub of the worm wheel with the possibility of moving it along the axis of the hub, the other end of the crank shaft is fixed in a bearing support located in a bushing connected to the mechanism for moving it and a counting device, the middle part of the crank shaft is a body - a tenon passing through the corresponding hole of the eccentric, the tenon on the outer surface has an inclined groove in which a key is placed on a sliding fit, connecting the tenon with the eccentric, which is connected to the slider by means of a connecting rod and a pin.

A large number of movable joints of the lever transmission in the drive will create unfavourable conditions for transmitting motion at high speeds of the electric motor shaft.

The proposed invention differs from the described prototype in that the lever transmission is made in the form of a flat combined crank-slider mechanism, due to the symmetrical relative arrangement of two connecting rods and sliders with respect to the common crank, the number of links is reduced, and the influence of inertial forces on the quality of motion transmission is reduced, which is especially significant when moving at high speeds of the electric motor shaft.

The technical result of the proposed invention is a reduction in the time for processing a rectangular pattern of waffle background cells due to a multiple increase in the feed rate along one coordinate.

This result is achieved by the fact that the feed drive of the processing head of the milling machine for processing the waffle structure of the shell, containing a lever transmission and a synchronous electric motor, provides a complex law of motion of the input crank, ensuring the maximum section of uniform movement of the output slider at a speed an order of magnitude higher than the speed of the transverse feed.

Fig. 1 shows a general view of the device, Fig. 2 shows a front longitudinal sectional view, Fig. 3 shows a general view of the connection of the device with the standard elements of the machine.

Fig. 1 shows a 3D model of the drive for horizontal and vertical feed of the cutting tool of a milling machine for processing rectangular cells of the waffle background of the shells.

The working element is positioned in the vertical plane by moving the console 1 along fixed posts installed in the base of the machine. In the horizontal plane, the working element moves with the help of the standard elements of the machine: ball screw transmission 2. An additional electric drive 13 is attached to the console 1 with the help of the frame 3, on the guides and the ball screw transmission 4, transmitting rotation to the crankshaft 6 through the clutch 14. To increase rigidity, the drive for vertical movement of the cutting tool of the machine is installed in the frame 5, to the front face of which rail guides 15 are attached. Rotation of the shaft of the electric motor 13 is transmitted through the crankshaft 6 to the connecting rods 8, pivotally connected to the sliders 7. The drive 11 of the cutting head 12 is fixedly attached to one of the sliders 7 with the help of a bracket 10.

Figure 2 shows a longitudinal section of the feed drive. Front view of a longitudinal section of the crank-and-connecting rod feed drive (a - view of the mechanism, b - section of the crank-and-connecting rod drive mechanism without a spindle and counterweight).

The drive comprises an electric motor 13, fixedly secured to a plate 18 by means of a flange 19, which transmits rotation to a crankshaft 6 via a coupling 20. The plate 18 is secured to walls 21 by a screw connection with pins. Rotation from the electric motor 11 is transmitted via the crankshaft 6 to connecting rods 8, pivotally connected to sliders 7. With the help of 8 carriages 22, sliders 7 move linearly along rail guides 15, secured with bolts on the plane of the lower plate 23. A plate 10 is installed on one of the sliders 7, and a counterweight 24 is installed on the other, balancing the vibrations.

The device is installed on the supporting unit 25 in place of the standard spindle unit of the milling machine. The supporting unit of the machine has standard feed mechanisms along the Z, Y, A axes, which are used either to position the device along the specified axes or to feed the device during its operation. Thus, the feed drive 1 along the X axis is designed to move the device to a specified processing depth and to retract the device for positioning on the next cell. Standard machine systems are used to position the device and check its position with a specified frequency. The device is attached to the machine unit 25 by brackets 16.

After positioning the device in the position of the initial processing point relative to the surface of the part on which the next cell of the wafer background is to be milled, a command is received from the control system of the device, connected to the control system of the machine, to turn on the rotation of the spindle 11, the crank-slider mechanism, providing reciprocating motion of the carriage 7 with the spindle 11 along the Y axis ₁ . The movement of the crank-slider mechanism along the W axis (an additional axis that replaces the standard feed of the machine along the rotary axis A) is carried out by a mechanism with a carriage 4 equipped with guides and a ball screw pair with a drive from the motor 17. According to the technology, cell processing includes two cycles - roughing and finishing. The roughing cycle is carried out by the mechanisms of the device. The finishing cycle - processing along the contour with specified parameters for accuracy and roughness can be carried out by the standard mechanism of the machine, or in a combination of the operation of the standard mechanism and the device.

After the cell is processed by the standard mechanism of the machine, the device is moved away from the part to the position for positioning for processing the next cell. The procedure is repeated until the waffle background is processed according to the drawing.

Claims (1)

A feed drive for a milling machine for processing a waffle shell structure, comprising a transmission lever crank-slider mechanism, characterized in that the crank of the lever transmission mechanism is made in the form of a crankshaft with two connecting rod journals with detachable heads of two identical connecting rods pivotally attached to them, the opposite non-detachable heads of which are pivotally connected to the sliders, one of which is the working one, and the second serves to balance and reduce the effect of centrifugal forces created by the crank.