JPS6234765A - Machining for non-cylindrical workpiece - Google Patents

Abstract

PURPOSE:To keep condition of a machining tool constant and perform accurate machining by controlling that the direction of machining action at the tool/ workpiece contact point becomes definite and that the passing speed of the contact point on the periphery of the workpiece becomes constant. CONSTITUTION:A table 1 reciprocating in X-axis direction, a table 2 placed on the table 1 reciprocating in the direction of Y-axis perpendicular to the X-axis, and a rotary table 3 placed on the table 2 and rotating at a slow speed with the center of the table 2 as the center of rotation are equipped. With this simultaneous three-axis control mechanism M, the rotary speed of a workpiece W and its rotary form are controlled so that the machining action of a grindstone T at its contact point on the workpiece W is made definite and that the passing speed Vc at the contact point becomes constant. In this way, the machining condition of the tool is always kept constant and machining of high accuracy can be made.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of machining the circumferential surface of a non-circular workpiece by bringing it into contact with a rotating processing tool while rotating the workpiece.

(Prior Art) Conventionally, when grinding or cutting the inner peripheral surface of a non-circular workpiece, such as the rotor housing of a vane oil pump, as shown in FIG. Workpiece W whose rotation center 0 is fixed while rotating
A processing tool movement method that revolves around the circumferential surface of the
As shown in the figure, two machining methods are generally adopted: a workpiece movement method in which the circumferential surface of the workpiece W is machined while rotating and moving the workpiece W with respect to a processing tool T rotating at a predetermined position. . Note that both of the above methods can also be employed when grinding or cutting the outer circumferential surface of a non-circular workpiece W.

(1! Problem that Ming attempts to solve) However, in the above conventional methods, both methods
Since the peripheral surface shape of is not a perfect circle, as the contact point between the processing tool T and the circular surface of the workpiece W changes to PI-P4, the passage of the processing tool T against the peripheral surface of the workpiece W changes. Contact point P2 where the speed is no longer constant and the radius of curvature of the circumferential surface of the workpiece W is large
, P4, the passing speed is slow and excessive machining is required, while the contact point P+, where the radius of curvature is small,
At P3, the passing speed becomes faster and sufficient machining cannot be achieved. As a result, there was a problem that the workpiece W could not be processed with high precision.

Further, the decrease in the processing accuracy of the workpiece W is also caused by another cause. That is, since the direction in which the processing tool T acts on the workpiece W constantly changes depending on the position of each contact point P+ to P4, the direction of the reaction force that the processing tool T receives from the workpiece W also changes accordingly. As a result, the deflection direction of the rotation axis of the processing tool T is not determined, and as a result, the workpiece W cannot be processed with high precision.

The present invention has been made in view of these points, and its purpose is to provide a processing method using the above-mentioned workpiece movement method by appropriately controlling the rotational speed and rotation form of the workpiece. To accurately process a non-circular workpiece circumference by keeping the machining radius 1 by a processing tool constant on the circumference of the workpiece.

(Means for Solving the Problems) In order to achieve the above object, the solution of the present invention is to machine the peripheral surface of a non-circular workpiece while rotating it with respect to a rotating processing tool. At the point of contact of the processing tool with the workpiece, the workpiece is moved so that the machining action direction is in one specific direction, and the passing speed of the workpiece circumferential surface at the contact point is constant. The peripheral surface of the workpiece is machined by controlling the rotational speed and rotational form of the machine.

(Function) With the above configuration, in the present invention, when processing the peripheral surface of a non-circular workpiece while rotating it with respect to a rotating workpiece, the workpiece at the contact point between the workpiece and the workpiece is By controlling the rotation speed of the workpiece so that the passing speed of the circumferential surface is constant, the rotation speed of the workpiece becomes relatively faster in areas where the radius of curvature of the workpiece circumference is large, while On the contrary, the rotational speed of the workpiece decreases where the radius of curvature of the surface is small. For this reason, over-machining and under-machining will not occur on the circumferential surface of the workpiece having a non-perfect circular shape, and the workpiece will be machined with high precision.

Moreover, by controlling the rotation form of the workpiece so that the direction of machining action at the point of contact between the workpiece and the workpiece is in one specific direction, the direction of the reaction force acting on the workpiece from the workpiece is constant. As a result, the direction of deflection of the rotation axis of the processing tool is always in the same direction, and as a result, the peripheral surface of a non-round workpiece can be machined with even higher precision without over- or under-machining. becomes.

(Example) Embodiments of the present invention will be described below based on the drawings.

Figure 1 shows the simultaneous three-axis control mechanism M, and Figure 2 shows the principle of machining a non-circular workpiece W. The case of a rotor housing will be exemplified. The inner circumferential surface of the workpiece W is ground by being rotated relative to a grindstone T, which is a processing tool that is fixed in a fixed position and rotates at high speed. Furthermore, the simultaneous three-axis control mechanism M is as follows.

An X-axis table 1 that reciprocates in the X-axis direction, a Y-axis table 2 that is provided on the top surface of the X-axis table 1 and that reciprocates in the Y-axis direction perpendicular to the X-axis direction, and the top surface of the Y-axis table 2. and a rotary table 3 that rotates at a low speed with the center of the Y-axis table 1 as the center of rotation, and the operation of these X-axis table 1, Y-axis table 2, and rotary table 3 changes the rotation form of the workpiece W. Control! ll'1J-
It is designed so that Then, by this simultaneous three-axis control mechanism M, the machining action direction at the contact point P of the grinding wheel T with the workpiece W is in one specific direction, and the contact point P on the inner peripheral surface of the workpiece W Passing speed [f V c
The rotational speed ω and rotational form of the workpiece W are controlled so that the rotational speed ω and the rotational form of the workpiece W are kept constant, and the grinding process is performed on the inner circumferential surface of the workpiece W.

That is, specifically, in order to keep the passing speed Vc at the contact point P of the inner peripheral surface of the workpiece W constant, the workpiece W
In areas where the radius of curvature of the inner peripheral surface is large, the rotational speed ω of the workpiece W is increased (
On the other hand, where the radius of curvature of the inner peripheral surface of the workpiece W is small, the passing speed V at the contact point P of the inner peripheral surface of the workpiece W is
This is done by controlling the rotational speed of the rotary table 3 according to the rotational speed φ of the workpiece W so as to slow down the rotational speed ω of the workpiece W in order to avoid insufficient grinding due to an increase in G.

In order to maintain the direction of machining action at the contact point P of the grindstone T on the inner circumferential surface of the workpiece W in one specific direction, the rotation angle φ of the workpiece W must be adjusted according to the rotation form of the X-axis table This is done by controlling the amount of movement of the Y-axis table 2. In the figure, A indicates the movement locus of the center O of the workpiece W.

In this way, the workpiece W is ground while its rotational speed ω and rotational form are controlled by the simultaneous three-axis control mechanism M. The procedure of the grinding method is shown in FIG. To explain based on this, first, a numerical control command value is created in order to give a predetermined operation to the simultaneous three-axis control mechanism M. That is, in step S1, the workpiece W
data of the ideal form, that is, the center 0 of the workpiece W is the origin, and the position coordinates at the contact point P for the ideal form on the inner circumferential surface are the angle 0 that changes at intervals of 1 degree, and the angle 0 of this angle 0. When the above contact point P and the center O of the workpiece W
Find the distance R connecting the coordinate component and J as a polar coordinate,
This is input into the numerical control command value creation system. Then, in step Sλ, based on the input ideal form data, the relational expression 〇-g (φ) between the rotation angle φ of the workpiece W and the above angle θ, and the XY coordinate values of the center O of the workpiece W and the above Relational expression with rotation angle φ: X=F+ (φ), Y
−F+ (φ), and the relational expression L=G(φ) between the arc goodness of the rotation form of the workpiece W and the rotation angle φ,
Based on these relational expressions, the rotational speed ω of the workpiece W (angular velocity of the rotation angle φ) such that the passing speed Vc of the inner circular surface of the workpiece W at the contact point P is constant ω=dφ/dt =Vc/ (d[G(φ)]/dφ) is determined. The relationship between the rotational angle φ and the rotational speed ω obtained in this way is stored in the machining system as a command value, and in step $3, the inner circumferential surface of the test piece is ground based on this command value. Further, in step S4, the grinding data at this time is measured, and in step Ss, the measured data is compared with the command value of the ideal form to determine whether the error is within a predetermined tolerance range. If this error is within the allowable range (YES), the process proceeds to step S6, and the grinding process of the inner circumferential surface of the workpiece W is started using the machining system based on the stored command value.

On the other hand, if the error is not within the allowable range in step S5, NO
In this case, in step S7, the correction form creation system creates correction form data according to the above-mentioned error. Then, returning to step S2, this correction form data is given to the numerical control command value creation system to correct the command value based on the ideal 7 ohm data of step S1, and the step is repeated based on this corrected command value. S
In step 3, grind the inner peripheral surface of the other chest piece.

Thereafter, as explained above, the error of the grinding data with respect to the ideal 7 ohm data is measured with the tap s4, and it is determined in step S5 whether this error is within the allowable range, and until the error is within the allowable range, step S7 , 82 to S4 are repeated, and when the error falls within the allowable range □, the process proceeds to step S6, where the workpiece W is ground.

Furthermore, as mentioned above (grinding errors occur with respect to ideal form data, for example, when processing a workpiece W using simultaneous three-axis loss value control, the main reasons are control errors due to response delays in the control system and grinding errors). This is due to the error caused by the error, and the correction procedure for this error will be explained based on Fig. 4. In the figure, the solid line indicates the inner periphery of the test piece when ground according to the ideal 7-ohm data. If the shape shown by the broken line is the shape of the actually ground inner circumferential surface, then the area surrounded by both inner circumferential shapes will be the grinding error with respect to the ideal form data.Therefore, find the correction data. In order to achieve this, the grinding error can be added or subtracted from the ideal form data as a correction amount.In other words, the grinding error should be added or subtracted from the ideal form data as a correction amount. The grinding process will be performed using the specified command value.

Therefore, in the above embodiment, the workpiece W has its rotational speed ω and rotational form such that the machining action direction at the contact point P to the grindstone T is in one specific direction, and Since the grinding process is performed while the passing speed VG at the contact point P is controlled to be constant, the reaction force from the workpiece W to the grindstone T always acts in a constant direction during grinding, causing the rotation axis of the grindstone T to deflect. The direction becomes constant, and the grinding conditions are always constant regardless of changes in the radius of curvature of the inner circumferential surface of the workpiece W. As a result, the inner circumferential surface of the non-round shaped workpiece W after processing is processed with high precision without causing excessive or insufficient grinding.

Moreover, the grinding error with respect to the ideal form of the workpiece W is detected using the test piece, the command value of the initial ideal 7 ohm data is corrected based on the error, and the workpiece W is ground based on the corrected command value. Because of the processing, the workpiece W does not always deviate from the allowable range of the ideal form (the workpiece W is ground and processed with even higher precision).
can be obtained.

In addition, although the case where the inner circumferential surface of the workpiece W is ground is explained in the above embodiment, the present invention is not limited to this, and the workpiece W
Needless to say, the present invention can also be applied to the case of grinding a non-perfectly circular outer peripheral surface. Moreover, it can of course be applied not only to grinding but also to other machining such as cutting.

(Effects of the Invention) As explained above, according to the method for processing a non-circular workpiece of the present invention, the peripheral surface of the non-circular workpiece is machined while rotating the non-circular workpiece with respect to a rotating processing tool. When doing so, the rotational speed of the workpiece is adjusted so that the working direction at the contact point of the workpiece with the workpiece is in one specific direction, and the passing speed of the workpiece circumferential surface at the contact point is constant. Since the rotation form is controlled, the machining conditions of the machining tool on the circumferential surface of the workpiece are always kept constant, and the workpiece can be machined with high precision without over-machining or under-machining.

[Brief explanation of drawings]

Figures 1 to 4 show embodiments of the present invention, Figure 1 is a schematic diagram of the simultaneous three-axis control mechanism, Figure 2 is an explanatory diagram explaining the principle of machining the workpiece, and Figure 3 is the machining process. FIG. 4 is an explanatory diagram showing the concept of correcting the form of the workpiece from the processed form to the ideal form. FIG. 5 and FIG. 6 are explanatory diagrams of the conventional method, respectively. P...Contact point, T...Wheelstone, Vc,...Passing speed at the contact point on the circumferential surface of the workpiece, W...Workpiece, ω...
・Rotation speed of workpiece, φ...Rotation angle of workpiece. Figure 1 Figure 2 Figure 3 Figure 5 Figure 4 Figure 6

Claims (1)

[Claims] (1) A method of machining the circumferential surface of a non-circular workpiece while rotating it with respect to a rotating processing tool, in which the direction of machining action at the point of contact of the processing tool with the workpiece is in a specific direction. The method is characterized in that the peripheral surface of the workpiece is machined by controlling the rotational speed and rotation form of the workpiece so that the rotational speed and rotation form of the workpiece are oriented in the same direction and the passing speed at the contact point of the workpiece peripheral surface is constant. Processing method for perfectly circular workpieces.