CN102500765B - Numerical control spherical lathe - Google Patents

Abstract

The invention discloses a numerical control spherical lathe, which comprises a base. A servo motor is arranged in the base, a spindle assembly is arranged on the base and connected with the servo motor through a speed reducing transmission device, and a workpiece clamping unit is installed at the front end of the spindle assembly. A Z-axle circle center locating unit is arranged on the base, a Y-axle rotating unit is installed on the Z-axle circle center locating unit, an X-axle radius feeding unit is installed on the Y-axle rotating unit, and the upper portion of the radius feeding unit is provided with a knife rest and a knife rest converting unit. The numerical control spherical lathe adopts a multiple-axle lathe system with a single coordinate system controlled by five shafts and the normal cutting principle. A cutting tool always aligns at the circle center like the fact that a compass describes a circle around a point, and accordingly the roundness is very high. When the numerical control spherical lathe performs processing, a cutting edge cutting error and an interpolation error which are caused by quadrant left-and-right cutting when an ordinary numerical control lathe cuts a round sphere do not occur, wherein the errors include tool marks of program translation and pause in quadrant passing process.

Description

A CNC spherical lathe

technical field

The invention relates to a machine tool, in particular to a numerically controlled spherical lathe, which can be widely used in processing spherical joint bearings, various ball pins and connecting rod ball pins of automobile chassis, ball cores of ball valves in the plumbing valve industry, and human bodies. Bone joints made of bones, spherical injection pumps in hydraulic pumps, optical molds and lamps, etc.

Background technique

At present, the lathes used to process spherical surfaces mainly come from two sources: existing lathe modification and imported special equipment, among which:

1. The modification of the existing lathe is to modify the cross carriage of the original lathe on the general machine tool, add a turntable to the cross carriage and hang it on the semi-automatic tool feed of the X axis to complete the work of normal arc processing; the turntable is fixed A tool holder or a pair of small pallets for manual compensation in the X direction; currently it is widely used in the field of water valve ball and optical mold processing.

2. The imported special equipment is mainly hydraulic machine tools from Taiwan. The principle of this machine tool is to use one or two turntables, which are respectively concentric with the main axis through hydraulic control. The turntable is driven by one-way or two-way linear oil cylinders, and the turntable is driven by rack and pinion to achieve the purpose of rotary cutting, that is, normal work. Semi-fine cutting and fine cutting can be done by changing different turntables. In addition, there are also double turntables fixed on the X carriage for heart-changing cutting.

The above two devices have the following problems:

1. Disadvantages of modified equipment

a. The main body of the machine tool is a general-purpose lathe equipment, the spindle accuracy is >0.01, the speed is low <1600 rpm, and the box is driven by a stepped gear, which cannot cut at a constant linear speed.

b. The modified turntable uses radial bearings and plane bearings. The shaft diameter of the turntable is short, the rigidity and precision are poor, and the surface roughness of the cutting workpiece is poorer than Ra>1.6um.

c. The turntable transmission is a multi-stage mechanical transmission with large gaps and semi-automatic control. The operator needs to be very skilled in operation.

d. The tool cutting in the R radius direction is controlled by manual compensation, and the cutting consistency is poor, so automatic compensation control cannot be performed.

e. Multi-tool automatic tool change cannot be performed.

f. The protection ability is weak, wet cutting is not possible, and the production environment is very poor.

2. Disadvantages of imported spherical special equipment

a. Disadvantages of hydraulic presses

(1) Lack of multi-tool replacement processing, only semi-finishing and finishing cutting.

(2) The tool wear needs to be artificially determined with a dial gauge to determine the compensation amount, and the scrap rate is high.

(3) Repeated positioning of the double turntable will cause the center of the circle to deviate, and the sphericity will be unstable.

(4) Poor protection ability. The water and cutting cannot be handled, and the environment is poor.

b Disadvantages of CNC lathe X-axis carriage plus double turntable machine

(1) The R radius direction of the turntable cannot be automatically controlled by the program, and has the same disadvantages as the hydraulic machine.

(2) The cost of equipment is high, the return rate of function is low, and the automatic compensation of the tool in the R direction cannot be achieved, and the polar coordinate processing and multi-continuous variable-diameter ball processing cannot be performed.

(3) Because the turntable needs to be switched, as the wear gap of the X-axis screw becomes larger, the ellipticity will also increase greatly.

Contents of the invention

The technical problem to be solved by the present invention is to provide a single-coordinate system with 5-axis control and a multi-axis spherical lathe system. The lathe has high machining accuracy and can achieve a spherical processing true roundness of ≤5um; the roughness can reach a mirror surface of 0.2um﹤Ra <0.4um accuracy requirements.

In order to solve the above technical problems, the present invention provides a CNC spherical lathe, which includes a base, a servo motor is arranged in the base, a main shaft assembly is arranged on the base, and the main shaft assembly is connected with the servo motor through a reduction transmission device. The workpiece clamping unit is installed at the front end of the spindle assembly; the Z-axis center positioning unit is installed on the base, and the Y-axis rotation unit is installed on it. The X-axis radius feed unit is installed on the Y-axis rotation unit. The upper part of the radius feed unit A knife holder and its conversion unit are installed.

The reduction transmission device can have three forms: one is a planetary gear reducer connected to a servo motor, and the planetary gear reducer is directly driven by the rotating shaft of the main shaft assembly.

The second is to include a synchronous belt connected to the servo motor, and the synchronous belt is connected to the rotating shaft of the main shaft assembly through a planetary gear reducer.

The third is the worm gear reducer connected with the servo motor, and the worm gear reducer is then connected with the rotating shaft of the main shaft assembly.

The above workpiece clamping unit may be a collet pulled by a hydraulic rotary cylinder.

The Z-axis circle center positioning unit includes a screw rod and a supporting plate installed on the screw rod, the Y-axis rotating unit is installed on the supporting plate, and the installation position of the screw rod is parallel to the axis of the main shaft assembly.

The above-mentioned Y-axis rotation unit includes a turntable and its driving mechanism.

On the edge of the Z-axis circle center positioning unit, there is a rotary hinge for routing the X-axis radius feed unit, the tool holder and its conversion unit.

Working principle of the present invention:

The parts to be processed are installed on the workpiece clamping unit of the spindle assembly (C-axis), that is, in the collet (or on the chuck), and the servo motor drives the spindle of the spindle assembly to rotate through the reduction transmission device, and the speed is 0 -Controllable between 5000 rpm. The Z-axis center positioning unit walks to the downward projection of the center of the part according to the position of the center of the circle specified by the program (that is, the center of the circle coincides with the projection), and the Y-axis rotation unit sets the program and turns the turntable according to the cut angle required by the actual object. Execute to this angle; then the X-axis radius feed unit goes to the center of the circle according to the program to the position of the first rough cutting, the Y-axis rotation unit starts to rotate, and controls the tool on the tool post to complete the cutting angle according to the program; then the X-axis radius The feed unit will carry forward to the semi-finishing position again according to the program, and the Y-axis rotation unit will reversely rotate the angle to complete the semi-finishing. Afterwards, the X-axis radius feed unit moves back to the tool change position, the tool holder conversion unit replaces the finishing tool in place, the X-axis radius feed unit feeds the tool again to the tool finish cutting position, and the Y-axis rotation unit rotates this angle again to complete the finish cutting. At this time, according to the product demand, the tool can be retracted to the tool change point again, replace the super-finishing tool and return to the finishing point to complete super-finishing; finally retract the tool and replace it with a rough turning tool. The servo motor stops, the hydro-pneumatic of the workholding unit releases the collets and removes the part. This continuous process is exactly the working principle of the present invention. If mutual interpolation is adopted, more complex normal cutting can be done to realize curved surface parts processing.

Beneficial effects of the present invention:

1. The one-time clamping and forming of the workpiece is realized with general-purpose equipment, and rough, semi-finishing, finishing, and super-finishing are realized, which reduces the process and turnover storage; improves efficiency, changes from manual operation to digital, quantitative control operation , It can be completed without skilled lathe workers. Therefore, the processing cycle of the product is greatly improved, the precision of the product can be within ±0.01mm, and the CPK value is greater than 1.33. The roughness of the product can be increased from 1.6um in the original technology to 0.8um, and the roughness can reach 0.2um (mirror effect) when equipped with a super precision knife. The roundness has risen from the original 0.02mm to within 0.005mm now.

2. Using frequency conversion and servo control, the energy consumption is greatly reduced. The first pass rate has been fully reflected in the performance index of CPK. The fully enclosed casing and iron filings collection unit have greatly improved both environmental protection and labor safety. Due to the use of full protection, it is possible to change from dry cutting to wet cutting, which improves the life of the tool, reduces wear and tear, reduces replacement time, and improves the quantity and quality of finished products.

Description of drawings

Fig. 1 is the front view of embodiment 1;

Fig. 2 is the left view of embodiment 1;

Fig. 3 is the top view of embodiment 1;

Fig. 4 is the back view of embodiment 1;

Fig. 5 is the right view of embodiment 1;

Fig. 6 is the front view of embodiment 2;

Fig. 7 is the left view of embodiment 2;

Fig. 8 is the top view of embodiment 2;

Fig. 9 is the back view of embodiment 2;

Fig. 10 is a right side view of Embodiment 2.

Detailed ways

The present invention will be further described below in conjunction with two embodiments. Wherein Fig. 1-Fig. 5 is the schematic diagram of embodiment 1, Fig. 6-10 is the schematic diagram of embodiment 2.

As shown in the figure, the CNC spherical lathe of the present invention has a main structure including a base 1, a servo motor 2 is arranged in the base 1, a main shaft assembly 3 is arranged on the base 1, and the main shaft assembly 3 communicates with the servo motor through a reduction transmission device. 2 connection, a workpiece clamping unit 8 is installed at the front end of the main shaft assembly 3; it is characterized in that a Z-axis center positioning unit 4 is provided on the base 1, a Y-axis rotation unit 5 is installed on it, and a Y-axis rotation unit 5 is installed on the Y-axis rotation unit 5. The X-axis radius feed unit 6 is equipped with a tool rest and a conversion unit 7 on the upper part of the X-axis radius feed unit 6 .

The present invention defines the main shaft assembly 3 as the C axis, that is, the rotation axis of the workpiece to be processed; there are two control methods for the servo motor 2, one is frequency conversion control, and the other is servo control. The servo can control the main shaft assembly 3 to perform rotation positioning and angle control.

The radius feed unit 6 is used to control the radius change of the ball machining, that is, the program control can be carried out from the blank of the part during cutting, and the diameter can be changed continuously, from rough machining to finishing machining of the blank, and superfinishing.

The Y-axis rotation unit 5 is a rotation axis that changes the normal angle, and is also the most frequently used cutting axis.

The Z-axis center positioning unit 4 is a displacement axis between the center of the turntable and the axis of the main shaft, and is mainly used for changing the position of the center of the circle, positioning the position of the center of the circle or continuously changing the axis of the center of the circle.

The tool rest and its conversion unit 7 is the tool rest control axis (D axis). According to the design needs, electric tool rest, servo power tool rest or power head can be considered for spherical drilling, milling, grinding and engraving.

The working signal source of the diameter feeding unit 6 and the tool holder and its conversion unit 7 is transmitted through the rotating hinge 9, and can follow up at high speed when rotating, and the working range is 0°-180° or +90°--90°.

The mechanical structure of the turntable of the present invention is a wrist joint design, wherein the axes of the Z-axis circle center positioning unit 4, the Y-axis rotation unit 5 and the radius feed unit 6 are combined, such as: the X-axis radius feed unit 6 and the Y-axis rotation unit 5 Interpolation work can be performed, and continuous arc-shaped surfaces, spheres, and ellipsoids can be processed in polar coordinates in the normal direction; the servo control of the spindle assembly 3, the X-axis radius feed unit 6 and the Y-axis rotation unit 5 jointly participate in the three-axis Interpolation, the tool rest and its conversion unit 7 are electric spindles, which can be used for engraving and milling control on spherical surfaces, and can also be used for spherical threads.

The numerically controlled spherical lathe of the present invention adopts a single coordinate system controlled by 5 axes, a multi-axis lathe system, and its principle is the principle of normal cutting. When cutting, the cutting tool always draws a circle to the center of the circle, just like a compass draws a circle around a point, so Its true roundness is very high. The present invention does not appear cutting error and interpolation error of the cutting edge when the ordinary numerical control car cuts the ball, including cutting tool marks and stoppage of time-limited program conversion.

The characteristics of each component of the present invention:

1. Main shaft assembly 3 (C-axis) adopts angular contact bearing structure, with DBD (a sorting method of multi-row bearings) in the front and DB (a sorting method of multi-row bearings) in the back. The workpiece clamping unit 8 pulls the collet for the hydraulic rotary cylinder to complete the clamping of the workpiece to be processed. The spindle motor starts to rotate under the condition of asynchronous frequency conversion servo control, and the speed range can be selected from 0-5000 rpm according to different parts.

2. The cross carriage of the Z-axis circle center positioning unit 4 carries the Y-axis rotation unit 5 and the axis radius feed unit 6. Driven by the servo motor of the Z-axis circle center positioning unit 4, the Z-axis screw rotates to make the cross carriage Move to the bottom of the part and make the center of the part coincide with the center of the turntable. Because during mechanical assembly, the distance between the center of the turntable of the Y-axis rotating unit 5 and the axis of the main shaft has been adjusted to zero, so that it coincides with the projection line of the axis of the main shaft, and the positioning pin ensures the accuracy of the center of the circle.

3. The structure of the Y-axis rotation unit 5 is an upper and lower angular contact bearing and is preloaded in DB mode. Simultaneously adopts three transmission modes

(1) The servo motor is directly connected to the rotating shaft through the planetary gear reducer to complete the angle control. The relative model is shown in Figure 6-10 of Embodiment 2.

(2) The servo motor is internally connected to the rotating shaft through the synchronous belt and then through the planetary gear reducer to achieve the method of controlling the precise movement of the Y-axis. See Figure 1-5 of Example 1 for details.

(3) The servo motor is connected to the rotating shaft through the worm gear to achieve rotation control.

4. The control axis of the X-axis radius feed unit 6 carries the tool post of the D-axis and its conversion unit 7. Driven by the ball screw of the servo motor, the radius position control and the tool change position control of the tool post are completed.

5. The tool holder and its conversion unit 7 are horizontal electric tool holders, which are automatically controlled by the program to realize the tool change of 4-8 eight stations, or the control of the electric spindle for engraving, milling and grinding.

6. The drive motor of the X-axis radius feed unit 6, the tool post and the control line of the conversion unit 7 pass through the rotary hinge 9, protected by a sealed high-temperature resistant bellows, and control the X-axis and the tool post axis motor in the electrical cabinet. The signal power and the X-axis initial origin position signal are sent back to the electrical box and the numerical control system through the rotary hinge 9. Simple and low-cost, it solves the problem of safe transportation and protection of electrical rotation control, and the problem of lubrication of the X-axis screw and guide rail.

The above-mentioned embodiments are only used to illustrate the present invention, but do not limit the scope of the present invention. After reading the present invention, those skilled in the art can modify the various equivalent forms of the invention within the scope of the appended claims of the application. limited range.

Claims (9)

1. A CNC spherical lathe, comprising a base (1), a servo motor (2) is provided in the base (1), a spindle assembly (3) is provided on the base (1), and the spindle assembly (3) passes through The reduction transmission device is connected with the servo motor (2), and the workpiece clamping unit (8) is installed at the front end of the main shaft assembly (3); it is characterized in that the base (1) is provided with a Z-axis circle center positioning unit (4). A Y-axis rotation unit (5) is installed on the Z-axis center positioning unit (4), and an X-axis radius feed unit (6) is installed on the Y-axis rotation unit (5). The upper part of the radius feed unit (6) A knife rest and its conversion unit (7) are installed, and the knife rest and its conversion unit (7) are automatically controlled by a program. 2. The CNC spherical lathe according to claim 1, characterized in that the reduction transmission device includes a planetary gear reducer connected to the servo motor (2), and the planetary gear reducer is directly connected to the rotating shaft of the main shaft assembly (3). linked drive. 3. The CNC spherical lathe according to claim 1, characterized in that the reduction transmission device includes a synchronous belt connected to the servo motor, and the synchronous belt is connected to the rotating shaft of the main shaft assembly (3) via a planetary gear reducer. 4. The numerical control spherical lathe according to claim 1, characterized in that the reduction transmission device is a worm gear reducer connected with a servo motor, and the worm gear reducer is then connected with the rotating shaft of the main shaft assembly (3). 5. The numerical control spherical lathe according to any one of claims 1 to 4, characterized in that the workpiece clamping unit (8) is a collet pulled by a hydraulic rotary cylinder. 6. The numerically controlled spherical lathe according to any one of claims 1 to 4, characterized in that the Z-axis circle center positioning unit (4) includes a screw and a supporting plate mounted on the screw, and the Y-axis rotation unit (5 ) is installed on the supporting plate, and the installation position of the screw rod is parallel to the axis of the main shaft assembly (3). 7. The numerically controlled spherical lathe according to any one of claims 1 to 4, characterized in that the Y-axis rotation unit (5) includes a turntable and its driving mechanism. 8. The numerical control spherical lathe according to claim 6, characterized in that the Y-axis rotation unit (5) includes a turntable and its driving mechanism. 9. The CNC spherical lathe according to any one of claims 1 to 4, characterized in that on the edge of the center positioning unit (4) of the Z axis, a unit (6) for feeding the radius of the X axis and a tool holder and its The rotary hinge (9) for the wiring of the conversion unit (7).

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