JP2686844B2 - Thin-walled workpiece processing method - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for processing a thin-walled work piece which is easily deformed when gripped.

Conventional technology When turning or grinding thin-walled tubular workpieces, the gripping part deforms when gripped by a chuck, and when the gripping is released after processing in this state, the strained part elastically restores and it is difficult to obtain a good perfect circle. is there. For this reason, special chucks such as finger chucks, vacuum chucks, and electromagnetic chucks were used according to the shape of the workpiece in order to obtain a highly accurate perfect circle.

In addition, non-round machining is possible by synchronous control of the spindle and X axis.
In NC machine tools, as shown in the flow chart of Fig. 6, the standard chuck is used to grasp and machine, the error from the true circle of the product is measured outside the machine, and based on the measurement result, a machining program of non-round shape is created. A method of correcting and processing to aim for a perfect circle is performed.

Problems to be Solved by the Invention By using the dedicated chuck in this manner, the workpiece is limited and the chuck becomes expensive. In addition, since the grasping force is very weak and the machining must be performed by light cutting in order to grasp so that there is no distortion, there is a problem that the machining efficiency is extremely poor. In addition, there is a problem that the number of steps is increased because the high precision reference surface processing must be performed in the previous step. Further, in the latter method of performing non-round machining, the chucking state changes once it is removed, and accurate machining is difficult and a good circle cannot be obtained. Further, there is a problem that a laborious procedure of removing after processing, correcting measurement data, and re-mounting is required, processing is required twice, and processing efficiency cannot be improved.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to strongly grip a thin-walled work piece with a standard chuck with a gripping force at the time of machining, which is extremely efficient and safe. It is intended to provide a processing method for obtaining a perfect circular work piece.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention is a NC lathe, a grinder, or the like, in which a workpiece gripped by a chuck of a C-axis controllable spindle is hardly distorted. The error from the true circle measured by a measuring device capable of measuring the radial dimension of the workpiece when grasping at extremely low pressure and the grasping force from the grasping state The difference between the error from the true circle measured on the workpiece and the error from the true circle is used as program data to synchronously control the rotation of the spindle and the radial feed of the tool, and based on this program data, non-reducing machining is performed and the grip is released. It is a perfect circle.

Action Find the error from the true circle when weakly gripped, increase the gripping force in that state, and find the error from the true circle when strongly gripped during machining. Program the difference between the two true circles. Non-round machining is performed by NC as data.

EXAMPLE The present invention will be described below with reference to FIG.

In a well-known NC lathe or NC grinder, a measuring device 2 capable of measuring a minute dimension such as an electric micrometer is attached to a turret 1 of a tool post of a lathe (not shown) in a direction capable of measuring displacement in the X-axis direction. ing. The output of the measuring device 2 is input to an NC device (not shown). Further, the unillustrated spindle is fitted with the chuck 3 at the tip thereof and the C axis can be controlled, and the spindle is indexed to a required angular position according to a command from the NC device. And the C-axis control and the X-axis control of the tool post can be synchronized. Inside the NC device, is the data of the measuring device of the spindle indexing position stored as continuous data by the interpolation function?
The main shaft is rotated at a very low speed and the continuous displacement output of the device is stored in correspondence with the angle. It also includes a storage unit for this data, a comparison calculation unit for obtaining the difference in error from the true circle, a correction program creation unit for using this difference as program data, and a correction program storage unit.

Next, the processing procedure will be described based on the flowchart of FIG.

In step S1, the thin workpiece W is turned into the chuck 3 of the lathe.
As shown in Fig. 2, grasp strain is not generated, or even if it occurs, it is very slight and it is light and is not displaced by the measured pressure.

In step S2, the main axis is controlled by the C axis to index the measurement start position, and the tool rest 1 is controlled by the X, 2 axes to measure the measuring device 2.
Is brought into contact with the outer circumference of the work W, and the output of the measuring device 2 at each spindle indexing position is stored in correspondence with the spindle indexing angle as shown in A of FIG. To do.

In step S3, the gripping force of the chuck is increased without removing the workpiece, and the workpiece is gripped with a strong pressure in the state during processing, and the workpiece becomes the state shown in FIG.

In step S4, the workpiece W similarly gripped in this state
The error from the true circle corresponding to one rotation of the spindle is measured in accordance with the spindle indexing angle of and is stored as shown in B of FIG.

In step S5, the difference is calculated by subtracting the error A from the true circle from the error B from the true circle in the comparison operation unit in the NC device.

In step S6, the correction machining program C is created and stored with the difference between the errors from both true circles as program data. In step S7, the correction machining program C synchronously controls the rotation of the spindle and the X-axis of the tool rest to perform non-round cutting. When the grasping of the chuck 3 is released after the predetermined cutting is completed, the thin-walled work W is elastically restored and the outer diameter becomes almost a perfect circle.

Effects As described above, the present invention has the following effects.

Even for thin-walled workpieces, the standard chuck can be used, which is economical and enables strong gripping, and heavy cutting and rough finishing can be done with one chuck, making it versatile and highly efficient. Furthermore, an extremely good perfect circle can be stably realized irrespective of the grasping error due to the degree of hitting of the nail during grasping.

Further, when the distortion due to the chuck is different in the longitudinal direction, it is possible to perform good machining on both a perfect work and a cylindricity even if the work is long by measuring and programming at several places along the length by the above method.

[Brief description of the drawings]

FIG. 1 is an explanatory view of the measurement state of the workpiece, FIG. 2 is a state diagram of the workpiece with a light grasp of the chuck, FIG. 3 is a state diagram of the workpiece with a strong grasp during machining, and FIG. FIG. 5 is a diagram showing an error from a circle, FIG. 5 is a diagram showing a machining procedure, and FIG. 6 is a diagram showing a conventional machining procedure. 1 ... Turret, 2 ... Measuring device 3 ... Chuck, W ... Workpiece

Claims (1)

(57) [Claims] 1. A judgment direction dimension of a workpiece grasped at a chuck of a spindle capable of controlling C-axis such as an NC-controlled lathe and a grinder at an extremely low pressure in a state where almost no distortion occurs. Both the true circle of the error from the true circle measured by a measuring device that can measure and the error from the true circle of the workpiece when grasped by strong pressure in the state of machining where the grasping force is increased from the grasped state The difference between the error from the data is used as program data to control the rotation of the spindle and the radial feed of the tool synchronously, and based on this program data, non-round machining is performed and a thin circle is obtained after gripping is released. Method.