A machining method for achieving uniform surface machining accuracy of a variable pitch screw rotor

Abstract

This invention provides a machining method for obtaining uniform surface machining accuracy of a variable pitch screw rotor, comprising the following steps: 1) Dividing the end face profile of the rotor into an involute, addendum circle, epicycloid, and dedendum circle; 2) Dividing one of the involute, addendum circle, epicycloid, and dedendum circle into N equal segments, with the connection point between each segment being the tool point; the line connecting the tool point and the origin is the extreme diameter L, and the angle between the extreme diameter L and the coordinate axis is θ; 3) For each toolpath, the tool point is used as the entry point, and the workpiece is rotated by an angle θ so that the extreme diameter is parallel to the coordinate axis; 4) The tool rotates along a direction parallel to the coordinate axis from one end of the workpiece to the other end; 5) After the tool is lifted to the outside of the workpiece, it moves to the cutting start end, and steps 1-4 are repeated until one of the involute, addendum circle, epicycloid, and dedendum circle is machined; 6) Steps 1-5 are repeated until all the involute, addendum circle, epicycloid, and dedendum circle are machined.

Description

Technical Field

[0001] This invention relates to a machining method for obtaining uniform surface machining accuracy of a variable pitch screw rotor. Background Technology

[0002] Vacuum pump rotors are already a challenge in the industry due to their complex shape. Variable pitch vacuum pump rotors, with their changing pitch causing variations in the tooth surfaces, are even more complex to manufacture, less efficient, and their tooth surface quality is highly dependent on the quality of the model. The tooth surface of variable pitch screws is a problem that urgently needs to be solved.

[0003] The machining of existing variable pitch vacuum pump screw rotors typically involves programming with CAM software followed by machining on a machine tool. However, the toolpath generated by CAM programming depends on the model quality and tool axis vector, resulting in a non-uniform and rough toolpath, leading to inconsistent tooth surface quality in the machined vacuum pump rotor. This method solves the problem of uneven and rough toolpaths generated by relying on the model and tool axis vector. Summary of the Invention

[0004] The main technical problem to be solved by the present invention is to provide a machining method for obtaining uniform surface machining accuracy of variable pitch screw rotor, so as to achieve uniform surface quality of workpiece.

[0005] To address the aforementioned technical problems, this invention provides a machining method for obtaining uniform surface machining accuracy of a variable pitch screw rotor, comprising the following steps:

[0006] 1) Divide the rotor's end face profile into involute, addendum circle, epicycloid, and dedendum circle;

[0007] 2) Divide one of the involute, addendum circle, epicycloid, and dedendum circle into N equal segments. The connection point between each segment is the tool position point. The line connecting the tool position point and the origin is the polar radius L. The angle between the polar radius L and the coordinate axis is θ.

[0008] 3) For each toolpath, the tool entry point is the tool position point, and the workpiece is rotated by an angle θ so that the extreme radius is parallel to the coordinate axis;

[0009] 4) As the tool rotates, it cuts from one end of the workpiece to the other along a direction parallel to the coordinate axis;

[0010] 5) After the tool is lifted to the outside of the workpiece, move it to the cutting start end and repeat steps 1-4 until one of the involute, addendum circle, epicycloid and dedendum circle is machined.

[0011] 6) Repeat steps 1-5 until the involute, addendum circle, epicycloid, and dedendum circle are all machined.

[0012] In a preferred embodiment: the equation of the epicycloid is:

[0013]

[0014] In a preferred embodiment: the equation for the tooth tip circle is:

[0015]

[0016] In a preferred embodiment: the equation of the involute is:

[0017]

[0018] In a preferred embodiment: the equation of the tooth root circle is:

[0019]

[0020] In a preferred embodiment: before dividing the curve into N equal segments in step 2, the length of the curve must first be calculated:

[0021]

[0022] In a preferred embodiment: The origin of the coordinate system is set to (0, 0), and the cutter point on the curve is set to (x1, y1). Then θ is represented as:

[0023]

[0024] In a preferred embodiment: the polar radius l1 corresponding to the tool position point (x1, y1) is expressed as:

[0025]

[0026] Compared with the prior art, the technical solution of the present invention has the following beneficial effects:

[0027] 1. This invention provides a machining method for obtaining uniform surface machining accuracy of a variable pitch screw rotor. This method is based on mathematical theoretical formulas and does not rely on three-dimensional models, achieving precise forming control from theory to theory.

[0028] 2. This invention provides a machining method for obtaining uniform surface machining accuracy of variable pitch screw rotor, using equal-length curve segments as a reference to ensure uniform surface quality of the workpiece. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the end face of a variable pitch screw rotor.

[0030] Figure 2 A schematic diagram of the end face parameters of a variable pitch screw rotor;

[0031] Figure 3This is a schematic diagram of the extreme diameter and rotation angle of a variable pitch screw rotor. Detailed Implementation

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0033] In the description of this invention, it should be noted that the terms "upper," "lower," "inner," "outer," "top / bottom," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0034] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installed", "equipped", "sleeved / connected", "connected", etc., should be interpreted broadly. For example, "connection" can be a wall-mounted connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0035] refer to Figures 1-3 This embodiment provides a machining method for obtaining uniform surface machining accuracy of a variable pitch screw rotor, including the following steps:

[0036] 1) Divide the rotor's end face profile into involute, addendum circle, epicycloid, and dedendum circle;

[0037] 2) Divide one of the involute, addendum circle, epicycloid, and dedendum circle into N equal segments. The connection point between each segment is the tool position point. The line connecting the tool position point and the origin is the polar radius L. The angle between the polar radius L and the coordinate axis is θ.

[0038] 3) For each toolpath, the tool entry point is the tool position point, and the workpiece is rotated by an angle θ so that the extreme radius is parallel to the coordinate axis;

[0039] 4) As the tool rotates, it cuts from one end of the workpiece to the other along a direction parallel to the coordinate axis;

[0040] 5) After the tool is lifted to the outside of the workpiece, move it to the cutting start end and repeat steps 1-4 until one of the involute, addendum circle, epicycloid and dedendum circle is machined.

[0041] 6) Repeat steps 1-5 until the involute, addendum circle, epicycloid, and dedendum circle are all machined. Before dividing the curve into N equal segments in step 2, the length of the curve must be calculated first:

[0042] Therefore, it is necessary to obtain the equations for each curve.

[0043] The equation of the epicycloid is:

[0044]

[0045] When R3 = R5, we have:

[0046]

[0047] The equation for the tooth tip circle is:

[0048]

[0049] The equation of the involute is:

[0050]

[0051] The equation for the root circle is:

[0052]

[0053] Taking the epicycloid as an example, the length of segment AB of the epicycloid is:

[0054]

[0055] make:

[0056] a = 2R³, b = 2h, u = 1 + t 2 A = (a + b) 2 B = 4ab

[0057] Then we have:

[0058]

[0059] Similarly, the length of the involute in segment CD is:

[0060]

[0061] To determine the rotation angle θ, we set the origin of the coordinate system to (0, 0) and the tool position point on the curve to (x1, y1). Then θ is expressed as:

[0062]

[0063] The polar radius l1 corresponding to the knife point (x1, y1) is expressed as:

[0064]

[0065] Taking the involute as an example, since the number of equal segments in a certain component of the involute has been determined to be n, the length of each segment is:

[0066] l eCD =l CD / n

[0067] Starting from the addendum circle, take another point along the curve, such that the curve length between the two points is l. eCD Since the angle of the starting point is known... The angle of the endpoint can be calculated using the length formula:

[0068]

[0069]

[0070] The length of the composition curve is calculated to be l. eCD After obtaining the endpoint angle value φ, the corresponding point (x1, y1) can be calculated based on the equation of the constituent curve, and then the polar radius can be calculated based on the point.

[0071] The same method can be used to calculate the other curve segments, so I won't go into details.

[0072] Therefore, the processing method in this embodiment can be expressed as:

[0073] 1) Define and assign values ​​to the parameters of each component curve, such as R3, h, and the variable range of each parameter;

[0074] 2) Express the curve equation by using various operations;

[0075] 3) Define intermediate parameters, such as the constant length value l. eCD Point parameter values wait;

[0076] 4) Calculate various intermediate parameter values, such as the equal length value l. eCD Point parameter values wait;

[0077] 5) Calculate the polar radius and the angle between the polar radius and the coordinate axis;

[0078] 6) Set up toolpath points to achieve the predetermined toolpath position.

[0079] The above description is merely a preferred embodiment of the present invention, but the design concept of the present invention is not limited thereto. Any non-substantial modifications made to the present invention by those skilled in the art within the scope of the technology disclosed in the present invention using this concept shall be deemed as an infringement of the protection scope of the present invention.

Claims

1. A machining method for obtaining uniform surface machining accuracy of a variable-pitch screw rotor, characterized by It comprises the following steps: 1) dividing the end surface profile of the rotor into an involute, a tip circle, an epicycloid and a root circle; The equation of the epicycloid is: ； Where R3 is the epicycloid fixed circle radius, R5 is the epicycloid moving circle radius, and h is the distance from the epicycloid moving point to the center of the epicycloid moving circle; The equation of the tip circle is: ； Where R4 is the tip circle radius; The equation of the root circle is: ； Where R2 is the root circle radius; 2) dividing one of the involute, the tip circle, the epicycloid and the root circle into N segments, and the connecting points between each segment are tool position points; the connecting line between the tool position points and the origin is the polar radius L, and the angle between the polar radius L and the coordinate axis is θ; Before the curve is divided into N segments in step 2, the length of the curve is calculated first: ； The coordinate origin is set as (0, 0), and the tool position points on the curve are θ is expressed as: ； Tool position The corresponding polar radius l1 is expressed as: ； 3) each tool path takes the tool position point as the feed point, and the workpiece rotates by θ angle to make the polar radius parallel to the coordinate axis; 4) the tool moves along the direction parallel to the coordinate axis from one end of the workpiece to the other end as the tool rotates; 5) after the tool is lifted to the outside of the workpiece, it is moved to the starting end of cutting, and steps 1-4 are repeated until one of the involute, the tip circle, the epicycloid and the root circle is machined completely; 6) steps 1-5 are repeated until all of the involute, the tip circle, the epicycloid and the root circle are machined completely.

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