A post-processing method for milling a rotary feature part

Abstract

The application discloses a kind of rotary feature parts milling post-processing methods, comprising: obtaining cutting track and non-cutting track;Obtain rotary feature track and non-rotary feature track;For the non-rotary feature track and non-cutting track, using RTCP tool tip follow-up mode processing;For the rotary feature track, the first tool position is handled using RTCP tool tip follow-up mode, and the tool position in subsequent rotary feature track is not output and shaft, only output shaft and the movement of shaft;Step 5: if any tool position in any rotary feature track meets the omission condition except the first tool position and the last tool position, ignore the movement of the tool position, and finally obtain the track after post-processing;The application avoids the reciprocating micro-motion of multi-axis when machining rotary features, increases the processing efficiency of numerical control system and milling rigidity, and improves the machining quality of part surface.

Description

Technical Field

[0001] This invention belongs to the field of multi-axis CNC machining, and particularly relates to a post-processing method for milling rotary feature parts. Background Technology

[0002] Rotating feature parts are among the most challenging key components to form and manufacture in high-end equipment such as aircraft engines and gas turbines. With the development of industries such as aerospace and shipbuilding, the processing quality requirements for their main functional structural parts are becoming increasingly stringent.

[0003] Rotary parts are typically machined on five-axis machine tools with rotary tables. Post-processing of their machining programs often employs a tool-tip tracking method (using RTCP tool-tip following mode). This means that only the tool axis rotation is calculated based on the tool axis vector, while the linear axis motion is tracked and interpolated by the CNC system itself. The biggest drawback of this method is that the CNC system's tracking and interpolation during machining can cause tool tip jumps, leading to machining vibrations, tool chipping, and other phenomena, significantly impacting the surface quality of the parts. This is particularly pronounced on machine tools with poor tracking performance. The main reason is that most machine tool control systems lack intelligent optimization when processing programs with tool-tip tracking; they can only transform them according to predetermined rules. What was originally a single-axis movement becomes a series of reciprocating micro-movements across multiple axes after machine interpolation. Furthermore, to ensure the interpolation accuracy of the CNC program, the line segments between tool points are usually very short, resulting in densely packed tool points and a large post-program size, leading to low system processing efficiency. Summary of the Invention

[0004] The purpose of this invention is to provide a post-processing method for milling rotary feature parts, which solves the problems of tool tip jump during machining caused by existing general post-processing methods, resulting in machining vibration and tool chipping.

[0005] This invention adopts the following technical solution: a post-processing method for milling rotary feature parts, comprising: Step 1: Using the cutting feed command line and the retraction feed command line in the tool position file as trajectory segmentation markers, the tool trajectory is divided for the first time, and the cutting trajectory and non-cutting trajectory are obtained; Step 2: Convert each tool position point in the tool position file to obtain the machine tool motion coordinates corresponding to each tool position point; Step 3: Based on the coordinate change value of the machine tool linear axis corresponding to each tool position point in each cutting trajectory, divide each cutting trajectory a second time to obtain the rotary characteristic trajectory and the non-rotational characteristic trajectory; Step 4: For the non-rotational characteristic trajectory and non-cutting trajectory, the RTCP tool tip following mode is used for processing; For the aforementioned rotary characteristic trajectory, the first tool position point is processed using the RTCP tool tip following mode, and subsequent tool position points in the rotary characteristic trajectory are not output. and The movement of the axis only outputs shaft and The movement of the axis; Step 5: If any tool point in any of the aforementioned rotary characteristic trajectories, excluding the first and last tool point points, satisfies the omission condition, the motion of that tool point point is ignored, and the post-processed trajectory is finally obtained; wherein, the omission condition is that the difference between the C-axis coordinates of any tool point point and the previous non-omitted tool point point is <90 degrees, and The axes are equal; in, The axis is the left-right direction of the machine tool spindle; The axis is the front-to-back direction of the machine tool spindle; The axis is the vertical direction of the machine tool spindle; The axis is around A rotating shaft.

[0006] Furthermore, the second division method is based on the following conditions: the knife point locations are continuous and the number is greater than 5: ; in, and These are the linear axis motion coordinates of the machine tool corresponding to the current cutting point. and The first tool position coordinates where the X and Y axes remain unchanged are recorded. This is the set comparison error.

[0007] The beneficial effects of this invention are: This invention can establish a machine tool motion transformation chain according to the machine tool structure type, and determine the rotational feature trajectory by post-conversion of the tool position file, thereby achieving targeted conversion processing of the rotational feature trajectory, avoiding multi-axis reciprocating micro-motion when the machine tool is machining rotational features, increasing the processing efficiency of the CNC system and milling rigidity, and improving the surface machining quality of the parts. This invention is applicable to any five-axis machine tool with a rotary table. For the machining of rotating parts, it maximizes the dynamic performance of the rotary axis of the five-axis CNC machine tool, increases milling rigidity, improves the surface quality of milling, and avoids phenomena such as machining pauses and tool vibration, thus solving the problem of efficient and precise machining on five-axis machine tools. Attached Figure Description

[0008] Figure 1 This is a tool path diagram for a certain rotary feature part; Figure 2 This is a partial toolpath file for a certain rotary feature part; Figure 3 This is a comparison of the post-processing results between the conventional method and the method in this embodiment; Figure 4 This is a comparison chart of the post-processing effects of the conventional method and the method in this embodiment. Detailed Implementation

[0009] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0010] This invention discloses a post-processing method for milling rotary feature parts, comprising: Step 1: Read the toolpath file to obtain all information of the machining program, including tool position information, speed information, tool information, etc. Use the cutting feed command line and the retraction feed command line in the toolpath file as trajectory segmentation markers to divide the tool trajectory for the first time and obtain the cutting trajectory and non-cutting trajectory. Step 2: Convert each tool position point in the toolpath file to obtain the machine tool motion coordinates corresponding to each tool position point; specifically: Based on the machine tool structure type, a machine tool motion transformation chain is established, which transforms the tool position and direction vector to obtain the motion information of the machine tool's linear and rotary axes.

[0011] The format of a single tool position point in the tool position file is as follows: The workpiece origin is installed at a distance from the center of the C-axis of the worktable. At this location, the machine tool motion coordinates are... At this time, the formula for calculating the angle of the rotation axis A is: (1) The calculation method for angle C is as follows: (2) In equation (2), when In theory, the C angle can take any value, and a reasonable angle value can be given according to the C angle situation before and after the actual machining process.

[0012] The transformation matrix for the tool position point from the workpiece's programming coordinate system to the machine tool's set coordinate system is: The tool position point rotates around the worktable - C transformation matrix is: Tool position point merged A-axis offset and The transformation matrix is Tool point around A Axis rotation - A Angle transformation matrix Knife point removal A The axis offset transformation matrix is Knife point removal A Axis offset and The transformation matrix is The details are as follows: , , , , The motion transformation relationship from tool position coordinates to machine tool coordinates is as follows: (3) Considering the structural characteristics of rotating parts, the workpiece's rotation center must be concentric with the worktable. Therefore, the following conditions must be met. , The final coordinate information in the machine tool coordinate system is as follows: (4) in, , This is an inherent property of the machine tool, and is a constant value. It is only related to the part's mounting position and remains a constant during processing. To facilitate subsequent difference comparisons, formula (4) is further simplified to: (5) Step 3: Based on the coordinate change value of the machine tool linear axis corresponding to each tool position point in each cutting trajectory, each cutting trajectory is divided a second time to obtain the rotary characteristic trajectory and the non-rotational characteristic trajectory; In this invention, the machine tool can be a double rotary table CNC machine tool or a swivel head rotary table CNC machine tool. The rotation axis of the rotary table is not limited, but the part needs to be installed in a way that ensures that it is aligned with the center of the machine tool rotary table and is coaxial.

[0013] Step 4: For non-rotational characteristic trajectories and non-cutting trajectories, the RTCP tool tip following mode is used for processing; For the rotary feature trajectory, the first tool position point is processed using the RTCP tool tip following mode. Subsequent tool position points in the rotary feature trajectory do not output X-axis and Y-axis motion; only the X-axis and Y-axis motion is output. shaft and The movement of the axis; Step 5: If any tool point in any rotary feature trajectory, excluding the first and last tool point points, satisfies the omission condition, the motion of that tool point point is ignored, and the post-processed trajectory is finally obtained; where the omission condition is that the difference between the C-axis coordinates of any tool point point and the previous non-omitted tool point point is <90 degrees, and The axes are equal.

[0014] in, The axis is the left-right direction of the machine tool spindle; The axis is the front-to-back direction of the machine tool spindle; The axis is the vertical direction of the machine tool spindle; The axis is around A rotating shaft.

[0015] The second division method is based on the following conditions: the knife point locations are continuous and the number is greater than 5: (6); in, and These are the linear axis motion coordinates of the machine tool corresponding to the current cutting point. and The first tool position coordinates where the X and Y axes remain unchanged are recorded. This is the set comparison error.

[0016] Example In this embodiment, a five-axis machine tool with two rotary tables is used for illustration. The rotation axis of one rotary table is based on the coordinate system of the machine tool. The A-axis rotates, and the other rotary table is in the machine tool coordinate system. Rotation of axis Rotation axis, wherein rotation axis A rotates within the range of -120° to +120°. The rotating shaft can rotate infinitely within a 360° range.

[0017] After reading the entire toolpath file information, the feed rate command "FEDRAT" in the toolpath file is identified, and the lines with feed rate and exit rate values ​​are set as start and end marker lines. The toolpath file is then divided into cutting paths and non-cutting paths based on these marker lines. Set the feed rate and exit rate to f1 and f2 respectively. and Let f1 and f2 be the row numbers (m=1,2,…) where the m-th detection of velocities f1 and f2 is performed. lines and All motion statements between lines form the m-th cutting trajectory, which can be used to identify all cutting trajectories. Motion trajectories outside the cutting trajectories are non-cutting trajectories.

[0018] Figure 1 For the rotary feature part in this embodiment, a typical toolpath is used for calculation and verification. The selected toolpath file is as follows: Figure 2 As shown, the feed rate is “FEDRAT / 120.0000” and the exit rate is “FEDRAT / 7800.0000”. The cutting path and non-cutting path are divided according to this speed.

[0019] Based on the established machine tool motion transformation chain, each tool position point in the tool position file is... The conversion is performed to obtain the machine tool motion coordinates corresponding to each tool position point. First, calculate each tool position using formulas (1) and (2). Corresponding machine tool rotary axis motion coordinate values Then, calculate using formula (5) Set the machine tool motion coordinates corresponding to all tool positions. Store the data according to the cutting trajectory lines.

[0020] For a single cutting path, based on the changes in the X and Y coordinates of the machine tool's linear axes corresponding to each tool position point in the cutting path, the cutting path is divided into rotary characteristic paths and non-rotational characteristic paths. Typical paths are as follows: Figure 1 As shown in the trajectory.

[0021] Starting from the first tool position point of a single cutting trajectory, the system traverses all rotary and non-rotational feature trajectories by determining the first and last points of the rotary features. A single cutting trajectory line may contain multiple rotary feature trajectories.

[0022] For non-rotational characteristic trajectories and non-cutting trajectories, the processing is carried out in the manner of tool tip tracking, that is, the coordinate values ​​of the machine tool rotary axis motion are calculated by formula (1) and formula (2). Machine tool linear axis motion coordinate values Location of the blade point To maintain consistency, the post-processing output is... During machine tool execution, the actual motion coordinate values ​​of the linear axes of the machine tool are calculated in real time by the coordinate transformation inside the CNC system. .

[0023] For rotary characteristic trajectories, the actual machine tool motion axis coordinates are obtained through transformation, and by comparing point positions, the unchanging machine tool motion axis coordinates are omitted from the output. For rotary characteristic trajectories, during the machining process... A Generally, this is a constant value, meaning the angle between the tool axis vector and the machine tool's C-axis is constant, and the projection of the tool tip trajectory onto the xy-plane of the programming coordinate system is a circle. During post-processing, the first tool position point is first output as... The tool position points in the subsequent trajectory will not be output. and Axis, only output shaft and The movement of the axis. The first and last points of the rotary feature trajectory are mandatory output points. For the midpoint of the trajectory, if the difference between the C-axis coordinates of the current tool position point and the previous tool position point (not omitted) is less than 90 degrees, and... The axes are equal.

[0024] All the completed post-processing trajectories are merged sequentially, and the corresponding CNC instructions are refined according to the CNC system to obtain a complete post-processing program, such as... Figure 3 As shown.

[0025] The cutting effect of the post-processing program completed by the conventional method is compared with that of the post-processing program completed in this embodiment. The cutting parameters, machining equipment, and machining conditions are completely consistent, and the machining results are as follows: Figure 4 As shown, the left side shows the actual effect after processing by the conventional method, with obvious transverse vibration marks on the surface of the part. The right side shows the actual effect after processing by the method of this embodiment, with no marks on the surface of the part and good consistency.

[0026] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A post-processing method for milling rotary feature parts, characterized in that, include: Step 1: Using the cutting feed command line and the retraction feed command line in the tool position file as trajectory segmentation markers, the tool trajectory is divided for the first time, and the cutting trajectory and non-cutting trajectory are obtained; Step 2: Convert each tool position point in the tool position file to obtain the machine tool motion coordinates corresponding to each tool position point; Step 3: Based on the coordinate change value of the machine tool linear axis corresponding to each tool position point in each cutting trajectory, divide each cutting trajectory a second time to obtain the rotary characteristic trajectory and the non-rotational characteristic trajectory; Step 4: For the non-rotational characteristic trajectory and non-cutting trajectory, the RTCP tool tip following mode is used for processing; For the aforementioned rotary characteristic trajectory, the first tool position point is processed using the RTCP tool tip following mode, and subsequent tool position points in the rotary characteristic trajectory are not output. shaft and The movement of the axis only outputs shaft and The movement of the axis; Step 5: If any tool point in any of the aforementioned rotary characteristic trajectories, excluding the first and last tool point points, satisfies the omission condition, the motion of that tool point point is ignored, and the post-processed trajectory is finally obtained; wherein, the omission condition is that the difference between the C-axis coordinates of any tool point point and the previous non-omitted tool point point is <90 degrees, and The axes are equal; in, The axis is the left-right direction of the machine tool spindle; The axis is the front-to-back direction of the machine tool spindle; The axis is the vertical direction of the machine tool spindle; The axis is around A rotating shaft.

2. The method for post-processing of milling of rotary feature parts according to claim 1, characterized in that, The second division method is based on the following conditions: the knife point locations are continuous and the number is greater than 5: ； in, and These are the linear axis motion coordinates of the machine tool corresponding to the current cutting point. and The first tool position coordinates where the X and Y axes remain unchanged are recorded. This is the set comparison error.

Images