RU2429950C2 - Procedure for milling screw grooves with alternative twist and radius of profile - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: table with blank is turned at angle of screw groove ascent. The blank is imparted with uniform progressive motion along its axis together with the machine table and with rotating motion corresponding to progressive transfer of the table. Complex rotating motion of the blank is obtained by summing uniform and alternate motions by specified law of rotation. Also, angle of table turn corresponds to the biggest twist of a screw groove, while gradually increasing radius of profile of the screw groove is produced by progressive transfer of a conic cutter along its axis.

EFFECT: expanded process functionality.

3 cl, 2 dwg

Description

The invention relates to the field of metal processing by cutting and can be used when milling helical grooves with a variable pitch and radius profile of the grooves on universal milling machines.

A known method of processing helical surfaces of variable pitch on milling machines, which uses a device [1] containing the spindle of the product, a mechanism for changing the pitch of the helical surface, including a master element, a variable speed motion transmission unit in the form of a cardan gear and a removable gear guitar located between the motion transmission unit and the product spindle.

The disadvantages of this method are the insufficient processing quality due to the low rigidity of the kinematic chain from the table lead screw to the product spindle, the difficulty of adjusting to the given law of changing the pitch of the screw surface and the inability to process screw surfaces with a variable profile radius.

The claimed invention is aimed at achieving a technical result, which consists in providing the possibility of milling helical grooves with any law of step change and with an increasing radius of the profile.

The inventive method of milling helical grooves with a variable pitch and radius of the profile is that the table of the universal milling machine with the workpiece is pre-rotated by the angle of the helix of the workpiece corresponding to the largest step; then rotation is reported to the milling cutter, a uniform translational movement along the axis of the workpiece is reported to the table with the workpiece. The workpiece is informed by a complex movement coordinated with the movement of the table, which is the sum of the uniform rotation and variable rotation coming from the table drive through the cam speed adjustment guitar; cam defining the law of change of step; rack and pinion transmission; power steering; pitch increment correction guitar. The summation of the uniform and variable rotation is carried out using the differential mechanism. In order to gradually increase the radius of the profile of the helical groove, a conical cutter is used, which, together with the slider of the machine, makes an axial feed movement.

Figure 1 shows a diagram of the milling of a helical groove, top view; figure 2 shows the kinematic diagram of the rotation of the workpiece.

The method can be applied on universal milling machines equipped with a longitudinal table on a rotary plate and a slider for axial feed of the cutter.

To implement the method requires a table 1 mounted on a turntable 2. The table must be moved from the drive 3 of the machine. The workpiece 4 is set using a dividing head 5. On the mechanism of the dividing head, rotation is transmitted from the table drive shaft 6 via two kinematic chains. The first chain provides a uniform rotation of the workpiece 4 and includes a removable gears guitar 7. The second chain provides a variable rotation of the workpiece and includes a replaceable gears guitar 8, a cam 9 with a pusher 10, a gear rack 11 mounted on the pusher 10, a gear wheel 12, a power steering 13 , the guitar of the interchangeable gears 14. The summation of the rotations from the two kinematic chains is carried out by the differential mechanism 15, which includes a drive wheel 16, a carrier 17 and a driven wheel 18. To implement the method conical cutter 19, which is mounted on the mandrel 20. The mandrel 20 is set in the spindle 21 and the slider 22 is supported earring.

The workpiece 4 is installed on the table 1 of the milling machine using a dividing head 5. Table 1 is rotated using the rotary plate 2 at the angle of elevation of the helical groove corresponding to the largest step:

where t _max - the largest step of the helical groove,

D is the diameter of the workpiece.

The conical cutter 19 receives rotation with a frequency of n _fr .

Table 1 with the workpiece 4 performs a uniform translational movement along the axis of the workpiece with a speed S _zag from the drive 3 of the machine. From the shaft 6 of the machine drive, the rotation is transmitted to the guitar of the removable gears 7 with a gear ratio i _beg , which is adjusted to the value of the initial pitch of the helical groove in the following ratio:

t ₀ mm displacement of the table with the workpiece → 1 turn of the workpiece.

Thus, uniform rotation of the workpiece n _{0 is} ensured.

To ensure the cutting of a helical groove with a variable pitch, uniform rotation is superimposed on the uniform rotation of the workpiece, providing an increase in the pitch Δt _{i of the} helical groove compared to the initial value t ₀ :

where t _i is the current value of the pitch of the helical groove.

Δt _i is a variable value, therefore, to ensure it, it is necessary to create an additional variable rotation of the workpiece Δn, which will be summed up with the main n ₀ . To ensure variable rotation of the workpiece, movement from the shaft 6 through the guitar of the interchangeable gears 8 is transmitted to the cam 9. The cam profile is constructed taking into account the specified law of change in the pitch of the helical groove. The gear ratio i _{to the} interchangeable gear guitars 8 is adjusted so that when moving the workpiece to the full length of the cut helical groove L, the _zag cam rotates through the angle θ _{p of} its working profile:

оборот кулачка,L _zag mm table movement →

cam rotation

where θ _p is the working angle of the cam profile in degrees.

The rack-and-pinion mechanism converts the translational movement of the cam follower 10 into the rotational movement of the gear 12. From the rack-and-pinion mechanism, the rotation is transmitted to the hydraulic booster 13, which increases the value of the torque in order to ensure sufficient cutting force. From the hydraulic booster 13, the rotation is transmitted to the guitar of the interchangeable gears 14 with the gear ratio i _у . The guitar 14 serves to correct the magnitude of the increment of the pitch and is adjusted so that when the pusher 10 moves by the difference in the radii Δr of the cam working section, the increment of the pitch Δt along the entire length of the helical cutting section is ensured:

The summation of the rotations along the two branches of the kinematic chain is carried out on the differential mechanism 15. Uniform rotation comes from the guitar 7 to the central drive wheel 16 of the differential mechanism. Variable rotation comes from guitar 14 to carrier 17 of the differential mechanism. The total rotation is removed from the driven gear 18 and enters the mechanism of the dividing head 5, in the spindle of which the workpiece is fixed.

Thus, the total variable rotation of the workpiece is carried out n _zag = n ₀ + Δn, which, in accordance with the uniform movement of the workpiece along its axis, ensures cutting of a helical groove with a variable pitch.

To ensure a gradual increase in the radius of the profile of the helical groove, the conical cutter 19 together with the slider 21 makes a feed movement S _fr along its axis. The feed rate S _fr is selected so that during the movement of the workpiece along its axis by the length of the section of the helical groove L, the _zag mill will move along its axis by the length of its working section L _fr .

L _zag mm table movement 1 with the workpiece →

→ L _fr mm moving slider 21 with cutter.

Information sources

1. USSR author's certificate No. 1528625, cl. B23C 3/32 dated 12/15/1989, bull. No. 46.

Claims (3)

1. The method of milling helical grooves with a variable pitch and radius of the profile, including turning the milling table with the workpiece at the angle of elevation of the helical grooves, message to the workpiece of uniform translational movement along its axis with the machine table and rotational movement corresponding to the translational movement of the table, characterized in that carry out a complex rotational movement of the workpiece by summing uniform and variable according to a given law of rotation, while the angle of rotation of the table corresponds to shemu step helical groove, to give a gradually increasing radius of helical profile groove bevel cutter translational movement along its axis. 2. The method according to claim 1, characterized in that the alternating rotation is set by a guitar for adjusting the speed of rotation of the cam, cam mechanism, rack and pinion transmission, power steering, guitar increment correction. 3. The method according to claim 1, characterized in that the summation of the uniform and variable rotations is carried out by means of a differential mechanism.

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