A CNC milling method and system for cycloidal wheels

Abstract

This invention provides a CNC milling method and system for cycloidal gears. The method includes: constructing a coordinate system based on the cycloidal gear structure; planning the tool path; designing the tool approach / retract mechanism, cutting method, and cutting direction; constructing a first curve equation for the cycloidal gear profile; constructing a second curve equation for a conjugate pinwheel based on the first curve equation; constructing an offset curve equation for the second curve equation, wherein the offset curve equation is the single-tooth tool trajectory equation for milling the cycloidal gear profile; obtaining the coordinates of each tool position point on the single tooth groove of the cycloidal gear based on the tool path and the tool trajectory equation; designing milling rules based on the tool path and the coordinates of each tool position point; milling the cycloidal gear according to the milling rules; and performing one-time positioning and installation machining based on the characteristics of the cycloidal gear. This invention enables macro-program parameterized machining of cycloidal gears, which is simple, flexible, efficient, and expands the application scope of domestic CNC systems.

Description

Technical Field

[0001] This invention relates to the field of cycloidal wheel machining technology, and in particular to a CNC milling method and system for cycloidal wheels. Background Technology

[0002] Reducers centered around cycloidal pinwheel pairs are widely used in industrial fields, especially in industrial robots, due to their advantages such as high rigidity, large speed ratio, high efficiency, high precision, and compact structure. However, despite recent breakthroughs in domestic robot research, significant obstacles remain in core technologies, particularly in manufacturing equipment and processes. Mastering key technologies for high-precision components is difficult. The high precision and complex machining of core components, such as reducers, have made domestic production a bottleneck hindering the industry's development. Independent proprietary technologies are essential, and the cycloidal pinwheel is a core component of these reducers; its machining is of paramount importance.

[0003] Cycloidal wheels are generally disc-shaped structures, with the outer side being the cycloidal wheel tooth profile and the inner side being the cycloidal wheel hole system. Here, CNC milling of cycloidal wheels refers to using a milling cutter to mill the cycloidal wheel profile circumferentially on a CNC machine tool, and then using drilling, reaming, boring, or milling to machine the hole system on the cycloidal wheel. The main processing requirements and difficulties are as follows:

[0004] 1. Due to limitations in tool size, the tool is prone to deformation during machining;

[0005] 2. To mitigate the impact of tool marks, the tool entry (exit) point and entry (exit) method should be set according to the working characteristics of the cycloidal wheel;

[0006] 3. Cycloidal wheel machining requires efficient programming and easy modification of structural and process parameters. Macro programs have advantages in this regard, but the cycloidal equation is complex and macro programs are difficult to write.

[0007] 4. CAD / CAM can reduce programming difficulty, but it is difficult to adjust process parameters, has low programming efficiency, large data volume, and poor readability.

[0008] 5. The cycloidal profile and internal hole system require high concentricity, making it difficult to complete the machining of the cycloidal profile and all internal hole systems in a single clamping operation to ensure concentricity. Summary of the Invention

[0009] The purpose of this invention is to provide a CNC milling method and system for cycloidal wheels, aiming to solve the problems of difficult programming, difficult machining, difficulty in concentricity between the cycloidal contour and the internal hole system, low machining accuracy, and easy deformation of cutting tools in existing cycloidal wheel machining methods.

[0010] In a first aspect, the present invention provides a CNC milling method for cycloidal gears, the method comprising:

[0011] A coordinate system is constructed based on the structure of the cycloidal wheel, and the zero point of the coordinate system is set at the center of the cycloidal wheel. z The zero point is set on the surface along the thickness direction of the cycloidal wheel. The Z-axis is perpendicular to the plane where the cycloidal wheel is located, and the positive direction is away from the cycloidal wheel. The Y-axis passes through the midpoint of the cycloidal wheel tooth groove and is perpendicular to the Z-axis. The positive direction is away from the cycloidal wheel. The X-axis is determined according to the right-hand Cartesian principle.

[0012] The tool path is planned according to the coordinate system, including the design of the tool approach and retraction methods, cutting methods, and cutting directions.

[0013] Construct the first curve equation of the cycloidal wheel profile, let the variable t be, the variable t vary from 0 to 1, and construct the second curve equation of the conjugate pinwheel with the cycloidal wheel based on the first curve equation;

[0014] Construct the offset curve equation of the second curve equation, wherein the offset curve equation is the tool trajectory equation for milling a single tooth groove of a cycloidal wheel profile;

[0015] With variables t The stepping parameters are used to obtain the coordinates of each tool position point for machining the single tooth groove of the cycloidal wheel based on the tool path and the tool trajectory equation.

[0016] The milling rules are designed based on the tool path and the coordinates of each tool position point, and the cycloidal wheel is milled according to the milling rules.

[0017] In some embodiments, planning the toolpath according to the coordinate system includes designing the tool approach / retract mode, cutting mode, and cutting direction; including:

[0018] The tool advance and retraction method is as follows: circular arc tangential advance and circular arc tangential retraction are adopted, and the cutting start point and cutting end point of the cycloidal profile are set at the apex of the cycloidal gear tooth profile, while the starting point of the circular arc tangential advance and the retraction point of the circular arc tangential retraction are set on the radial extension line of the apex of the cycloidal gear tooth profile.

[0019] The cutting method is as follows: milling the cycloidal wheel profile using a layered contour cutting method;

[0020] The cutting direction is as follows: the milling cutter starts from the starting point of the tangential infeed of the circular arc, moves along the circular arc tangent to the tooth profile to the vertex of the cycloidal profile tooth profile, and the vertex of the tooth profile serves as the starting point of the cycloidal profile cutting. Then, it cuts each of the remaining tooth profiles in sequence until it returns to the starting point of the cutting. Then, it overlaps one tooth gap to reach the vertex of the tooth profile, and the vertex of the tooth profile serves as the ending point of the cycloidal profile cutting. Finally, it cuts out from the vertex of the tooth profile along the circular arc tangent to the tooth profile and reaches the retraction point of the tangential retraction of the circular arc.

[0021] In some embodiments, the first curve equation for constructing the cycloidal wheel profile includes:

[0022] Based on the coordinate system, the equation of the first curve is constructed using the following formula:

[0023] ;

[0024] in, , ; The radius of the circle at the center of the needle teeth. The number of teeth on the cycloidal wheel. = +1 represents the number of teeth on the pinwheel. The amplitude coefficient, The radius of the needle teeth. X represents the relative rotation angle of the pinwheel, and X and Y represent the coordinates of points on the cycloidal wheel profile curve.

[0025] In some embodiments, constructing a second curve equation for the conjugate pinwheel of the cycloidal wheel based on the first curve equation includes:

[0026] make Then the equation of the second curve is:

[0027] ;

[0028] in, , Let t be the coordinates of the single tooth groove curve point at time t, representing the second curve equation of the conjugate pinwheel of the cycloidal wheel.

[0029] In some embodiments, the construction of the offset curve equation for the second curve equation, wherein the offset curve equation is a single-tooth groove tool trajectory equation for milling a cycloidal wheel profile, includes:

[0030] Depend on ,but:

[0031] ;

[0032] make , , The expression for the tool trajectory equation is as follows:

[0033] ;

[0034] in, , The coordinates of the tool position point for the cycloidal profile single-tooth groove tool trajectory. e is the tool offset distance. Let be the tool radius and 'a' be the machining allowance.

[0035] In some embodiments, the step of designing milling rules based on the tool path and coordinates of each tool position point, and milling the cycloidal wheel according to the milling rules, includes:

[0036] Step S01: Assign values ​​to the machining parameters of the cycloidal wheel;

[0037] Step S02: Assign values ​​to the layer thickness of the cycloidal wheel, including the starting layer, the ending layer, and the layer step;

[0038] Step S03: Initialize the program, move the tool to the safe plane, start the spindle, and turn on the coolant.

[0039] Step S04: Assign the variable t to 0, obtain the cutting start point coordinates and tool start point coordinates of the cycloidal tooth profile, move the tool to the X and Y coordinate positions of the tool start point, and prepare for cutting;

[0040] Step S05: Use the G01 command to move the tool to the current cutting layer thickness position;

[0041] Step S06: Use the circular interpolation command to make the tool cut into the cutting starting point of the cycloidal gear tooth profile in an arc manner;

[0042] Step S07: Assign values ​​to the cycloidal wheel tooth count parameters, which include the starting tooth count, the ending tooth count, and the tooth count step value;

[0043] Step S08: Set the coordinate rotation angle according to the number of teeth to be processed, and reassign values ​​to the variable t, including the initial value, the final value, and the step value;

[0044] Step S09: Calculate the coordinates of the single-tooth groove tool trajectory point of the cycloidal wheel based on the current t value;

[0045] Step S10: Use the G01 command to perform linear interpolation machining on the calculated point coordinates to form the machining path of the cycloidal wheel profile;

[0046] Step S11: Perform a step operation on variable t and determine whether the value of t after the step has reached the final value. If the final value has been reached, the tool is now at the current machining tooth profile vertex, and then proceed to step S12. If the final value has not been reached, return to step S09.

[0047] Step S12: Perform a step operation on the number of teeth and determine whether all teeth have been processed. If all teeth have not been processed, return to step S07. If all teeth have been processed, proceed to step S13.

[0048] Step S13: Reassign the variable t to 1, and obtain the coordinates of the end point of the cycloidal profile cutting and the coordinates of the retraction point of the circular arc tangential retraction;

[0049] Step S14: Use the G01 command to cut the tool to the cutting endpoint of the cycloidal profile;

[0050] Step S15: Using the circular interpolation command, the tool moves from the cutting endpoint of the cycloidal profile to the retraction point of the circular tangential retraction.

[0051] Step S16: Lift the tool, cancel coordinate rotation, perform step operation on the layer thickness, and determine whether the current layer thickness meets the requirements; if it does not meet the requirements, return to step S04; if it meets the requirements, the cutting ends.

[0052] In some embodiments, the tool position point includes the starting point of the circular arc tangential infeed, the starting point of the cycloidal profile cutting, each tooth profile point, the ending point of the cycloidal profile cutting, and the retraction point of the circular arc tangential retraction.

[0053] In some embodiments, the method further includes: using the internal hole system of the cycloidal wheel blank for rough positioning, clamping the outer periphery of the cycloidal wheel, then removing the rough positioning element, machining the internal hole system of the cycloidal wheel, then clamping the internal hole system portion of the cycloidal wheel again, loosening the outer periphery of the cycloidal wheel, and milling the cycloidal contour.

[0054] Secondly, the present invention provides a CNC milling system for cycloidal wheels, the system comprising:

[0055] The coordinate system construction module is used to construct a coordinate system based on the cycloidal wheel structure, setting the zero point of the coordinate system at the center of the cycloidal wheel. z The zero point is set on the surface along the thickness direction of the cycloidal wheel. The Z-axis is perpendicular to the plane where the cycloidal wheel is located, and the positive direction is away from the cycloidal wheel. The Y-axis passes through the midpoint of the cycloidal wheel tooth groove and is perpendicular to the Z-axis. The positive direction is away from the cycloidal wheel. The X-axis is determined according to the right-hand Cartesian principle.

[0056] The path planning module is used to plan the tool path according to the coordinate system, including designing the tool approach and retraction methods, cutting methods, and cutting directions.

[0057] The curve equation construction module is used to construct the first curve equation of the cycloidal wheel profile. Let the variable t be a variable that varies from 0 to 1, and construct the second curve equation of the conjugate pinwheel with the cycloidal wheel based on the first curve equation.

[0058] The offset curve equation construction module is used to construct the offset curve equation of the second curve equation, wherein the offset curve equation is the tool trajectory equation for milling a cycloidal wheel profile with a single tooth groove.

[0059] The tool position coordinate calculation module is used to calculate the coordinates of the tool position points using variables. t The stepping parameters are used to obtain the coordinates of each tool position point for machining the single tooth groove of the cycloidal wheel based on the tool path and the tool trajectory equation.

[0060] The milling execution module is used to design milling rules based on the tool path and the coordinates of each tool position point, and to mill the cycloidal wheel according to the milling rules.

[0061] Compared with the prior art, the present invention has the following advantages:

[0062] This invention combines the characteristics of cycloidal wheel CNC milling with those of domestically produced CNC systems. Based on the conjugate pinwheel curve equation of the cycloidal wheel, a macro-program mathematical calculation model (offset curve equation) is established. A macro-programming method (milling rules) for cycloidal wheel CNC milling that perfectly matches this calculation model is designed. Utilizing a concise, flexible, and easily adjustable macro-program, the requirements for adjusting the cycloidal wheel's structure and process parameters are effectively met, while reducing programming difficulty and improving programming efficiency. The proposed layered contour milling tool path and tool entry / exit methods effectively alleviate tool deformation and tool mark problems in cycloidal wheel contour machining. The proposed cycloidal wheel machining positioning and installation method effectively ensures the concentricity of the internal hole system and the cycloidal contour. This invention enables macro-program CNC milling of cycloidal wheels using a domestically produced CNC system, expanding the application scope of domestically produced CNC systems. Attached Figure Description

[0063] Figure 1 This is a flowchart of a CNC milling method for cycloidal wheels according to an embodiment of the present invention;

[0064] Figure 2 This is a schematic diagram of the cutting path for contour milling.

[0065] Figure 3 This is a schematic diagram of the profile curve of a single-toothed cycloidal wheel;

[0066] Figure 4 The offset curve for the profile curve of a single-toothed cycloidal wheel;

[0067] Figure 5 This is a schematic diagram of a cycloidal wheel CNC milling system according to an embodiment of the present invention.

[0068] The following detailed description, in conjunction with the accompanying drawings, will further illustrate the present invention. Detailed Implementation

[0069] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical or scientific terms used herein should have the ordinary meaning understood by those skilled in the art. The terms "comprising" and similar expressions used herein mean that the element or object preceding the word covers the element or object listed after the word and its equivalents, but does not exclude other elements or objects.

[0070] like Figure 1 As shown, the first embodiment of the present invention provides a CNC milling method for cycloidal gears, the method comprising steps S101 to S106, wherein:

[0071] Step S101: Construct a coordinate system based on the cycloidal wheel structure, and set the zero point of the coordinate system at the center of the cycloidal wheel. z The zero point is set on the surface along the thickness direction of the cycloidal wheel. The Z-axis is perpendicular to the plane where the cycloidal wheel is located, and the positive direction is away from the cycloidal wheel. The Y-axis passes through the midpoint of the cycloidal wheel tooth groove and is perpendicular to the Z-axis. The positive direction is away from the cycloidal wheel. The X-axis is determined according to the right-hand Cartesian principle.

[0072] Step S102: Plan the tool path according to the coordinate system, including designing the tool approach and retraction methods, cutting methods, and cutting directions;

[0073] It should be noted that cycloidal wheel profile milling is essentially a 2D profile peripheral milling process. Profile machining typically requires tangential feed and retraction, and the start and end points of the cut should overlap to mitigate tool marks. Due to the cycloidal wheel's profile modification, the cycloidal wheel and the pin teeth maintain conjugate meshing in the meshing section, leaving gaps at the tooth tips and roots. Therefore, both the start and end points of the cut should be located at the apex of the tooth profile. For this reason, distributing the start and end points on the tips of two adjacent tooth profiles, although overlapping by one tooth profile machining step, minimizes the impact of tool marks from profile machining on the cycloidal wheel.

[0074] Specifically, in some embodiments, for the convenience of subsequent macro program tool position calculation, the tool entry and exit method is as follows: circular arc tangential entry and circular arc exit are adopted, the cutting start point and cutting end point of the cycloidal profile are set at the tooth profile apex, and the cutting start point and exit point are set on the radial extension line of the tooth profile apex.

[0075] Furthermore, the cutting direction is as follows: the milling cutter starts from the tangential entry point of the circular arc, moves along the circular arc tangent to the tooth profile to the vertex of the cycloidal profile tooth profile, and this vertex serves as the starting point for cutting the cycloidal profile. Then, it sequentially cuts each of the remaining tooth profiles until it returns to the starting point, overlaps one tooth space to reach the vertex of the tooth profile, and this vertex serves as the ending point for cutting the cycloidal profile. Finally, it cuts out from this vertex along the circular arc tangent to the tooth profile, reaching the retraction point of the tangential retraction point of the circular arc. For example, in this step, as... Figure 2 As shown, during the milling of the cycloidal gear profile, the milling cutter starts from point A and moves along arc AB, which is tangent to the tooth profile, to the cutting starting point B of the cycloidal gear profile (B is the vertex of the cycloidal gear tooth profile and also the point of tangency between arc AB and the tooth profile, while point A is on the extension line of the tooth tip radial direction OB). Then, it cuts sequentially to C, D, D1, D2, ..., returning to point B, and then overlapping one tooth. Finally, it cuts out from the tooth profile vertex (tooth profile cutting endpoint D) along arc DE, which is tangent to the tooth profile (point D is the point of tangency, and point E is on the extension line of the tooth tip radial direction OD), reaching the retraction point E.

[0076] Furthermore, in some embodiments, cutter deformation is also a significant issue in contour milling. Therefore, a layered contour cutting method is used to mill the cycloidal wheel contour. By reducing the layer height, cutter deformation is limited, thereby improving machining accuracy and tooth surface quality. Another characteristic of contour cutting is that the cutting parameters are uniform, resulting in uniform machining quality of the cycloidal wheel tooth profile.

[0077] Step S103: Construct the first curve equation of the cycloidal wheel profile, let the variable t be, the variable t ranges from 0 to 1, and construct the second curve equation of the conjugate pinwheel with the cycloidal wheel based on the first curve equation;

[0078] It should be noted that the calculation of the contour tool position point is generally based directly on the contour curve equation. However, due to the complexity of the cycloidal wheel contour curve equation, it is difficult to write a macro program directly based on this equation. Therefore, in this embodiment, the first curve equation is constructed according to the following formula:

[0079]

[0080] in, ;

[0081] ;

[0082] The radius of the circle at the center of the needle teeth. The number of teeth on the cycloidal wheel. = +1 represents the number of teeth on the pinwheel. The amplitude coefficient, The radius of the needle teeth. X represents the relative rotation angle of the pinwheel, and X and Y are the coordinates of points on the cycloidal wheel profile curve.

[0083] Considering that the cycloidal wheel and the pin wheel have conjugate tooth profiles, let the variable t be... If J represents the change in the relative rotation angle between the pins of the cycloidal wheel. Therefore, the equation of the second curve is:

[0084] ;

[0085] in, , Let be the coordinates of the point on the single-tooth groove curve at time t, representing the second curve equation of the conjugate pinwheel of the cycloidal wheel.

[0086] Step S104: Construct the offset curve equation of the second curve equation, wherein the offset curve equation is the tool trajectory equation for milling a single tooth groove of a cycloidal wheel profile.

[0087] After obtaining the equation of the second curve, the single-tooth pinwheel curve is generated using UG. The single-tooth pinwheel curve is equidistant from the radius of the offset pin teeth, thus obtaining the profile curve of the single-tooth cycloidal wheel, as shown below. Figure 3 As shown; this curve is arrayed around the center circumference of the cycloidal wheel to obtain the cycloidal wheel profile curve. The milling tool path for the cycloidal wheel profile is also the result of offsetting the tool radius and machining allowance from the cycloidal wheel profile curve; that is, the cycloidal wheel profile tool path is also an offset curve of the single-tooth cycloidal wheel profile curve, as shown... Figure 4 As shown. Based on this principle, it can be explained that the offset curve equation is the tool trajectory equation for a single tooth of the cycloidal wheel profile. Therefore, arraying the single-tooth tool trajectory around the center of the cycloidal wheel yields the entire cycloidal wheel tool trajectory. Thus, the second curve equation is used as the basis for calculating the tool position point, thereby simplifying the macro program's tool trajectory calculation.

[0088] Construct the bias curve equation:

[0089] Depend on ,but:

[0090] ;

[0091] make , , The expression for the tool trajectory equation is as follows:

[0092] ;

[0093] in, , The coordinates of the tool position point for the cycloidal profile single-tooth groove tool trajectory. e is the tool offset distance. Let be the tool radius and 'a' be the machining allowance.

[0094] Step S105: Using variables t The stepping parameters are used to obtain the coordinates of each tool position point for machining the single tooth groove of the cycloidal wheel based on the tool path and the tool trajectory equation.

[0095] It should be noted that the toolpath is calculated based on the toolpath planning and offset curve equations described above. Only one tooth groove needs to be calculated; then, the remaining tooth grooves are machined using the coordinate rotation of the CNC system. (The last sentence appears to be incomplete and possibly refers to a variable.) By using a stepping motion, the tool position points on the single-tooth curve of the cycloidal wheel can be calculated; reducing the stepping motion densifies the tool position points. Furthermore, the tool trajectory starting point A and retraction point E are respectively set on the radial extension line of the tooth profile apex, which is actually the result of offsetting the tooth tip normal by 2R+e, where R is the radius of arc AB(DE). Therefore, the coordinates of points A and E can also be calculated using the aforementioned offset curve equation.

[0096] In addition, it should be noted that the tool position points include the starting point A, the cycloidal profile cutting start point B, each tooth profile point, the cycloidal profile cutting end point D, and the retraction point E. Essentially, the cutting start point B and the cutting end point D belong to the tooth profile vertices, but for ease of understanding, the cutting start point is separated and explained separately in this embodiment.

[0097] Step S106: Design milling rules based on the tool path and coordinates of each tool position point, and mill the cycloidal wheel according to the milling rules.

[0098] It should be noted that the milling rule corresponds to the underlying logic of the macro program. Before designing the milling rule, it should also be noted that: 1) Although the tooth profile of the single-tooth cycloidal wheel is symmetrical and can be mirrored, the machining of the remaining tooth profile requires the use of coordinate rotation of the CNC system. The mirroring and rotation functions are difficult to use simultaneously in a CNC system (e.g., 8 V2.4), so the mirroring function is not used and the variable t is calculated throughout the process; 2) Although the above offset curve equation is used many times in the calculation process, it is difficult to use subroutines in the macro program loop, so subroutines are not used.

[0099] Furthermore, in some embodiments, the milling rules are as follows:

[0100] Step S01: Assign values ​​to the machining parameters of the cycloidal wheel;

[0101] Step S02: Assign values ​​to the layer thickness of the cycloidal wheel, including the starting layer, the ending layer, and the layer step;

[0102] Step S03: Initialize the program, move the tool to the safe plane, start the spindle, and turn on the coolant.

[0103] Step S04: Assign the variable t to 0, obtain the cutting start point coordinates and tool start point coordinates of the cycloidal tooth profile, move the tool to the X and Y coordinate positions of the tool start point, and prepare for cutting;

[0104] Step S05: Use the G01 command to move the tool to the current cutting layer thickness position;

[0105] Step S06: Use the circular interpolation command to make the tool cut into the cutting starting point of the cycloidal gear tooth profile in an arc manner;

[0106] Step S07: Assign values ​​to the cycloidal wheel tooth count parameters, which include the starting tooth count, the ending tooth count, and the tooth count step value;

[0107] Step S08: Set the coordinate rotation angle according to the number of teeth to be processed, and reassign values ​​to the variable t, including the initial value, the final value, and the step value;

[0108] Step S09: Calculate the coordinates of the single tooth groove cutter position of the cycloidal wheel based on the current t value;

[0109] Step S10: Use the G01 command to perform linear interpolation machining on the calculated point coordinates to form the machining path of the cycloidal wheel profile;

[0110] Step S11: Perform a step operation on variable t and determine whether the value of t after the step has reached the final value. If the final value has been reached, the tool is now at the vertex of the current machined tooth profile, and then proceed to step S12. If the final value has not been reached, return to step S09.

[0111] Step S12: Perform a step operation on the number of teeth and determine whether all teeth have been processed. If all teeth have not been processed, return to step S07. If all teeth have been processed, proceed to step S13.

[0112] Step S13: Reassign the variable t to 1, and obtain the coordinates of the end point of the cycloidal profile cutting and the coordinates of the retraction point of the circular arc tangential retraction;

[0113] Step S14: Use the G01 command to cut the tool to the cutting endpoint of the cycloidal profile;

[0114] Step S15: Using the circular interpolation command, the tool moves from the cutting endpoint of the cycloidal profile to the retraction point of the circular tangential retraction.

[0115] Step S16: Lift the tool, cancel coordinate rotation, perform step operation on the layer thickness, and determine whether the current layer thickness meets the requirements; if it does not meet the requirements, return to step S04; if it meets the requirements, the cutting ends.

[0116] In summary, by adopting macro programming of domestic CNC systems, parameter adjustments can be adapted, programming efficiency can be improved, and the application of domestic machine tools can be expanded; multiple feeds can help to approach the accuracy requirements; circular arc tangential feed (retraction) can effectively reduce the influence of tool marks; layered equal-height cutting can help control the layer height and alleviate tool deformation; and by establishing a mathematical model (offset curve equation) suitable for cycloidal wheel machining, the difficulty of tool position calculation can be reduced.

[0117] Furthermore, in some embodiments, the conventional clamping method for CNC milling of cycloidal wheels typically involves using a mandrel that mates with the through hole of the cycloidal wheel's input shaft as a positioning element. A pressure plate is then placed on the positioning mandrel to clamp the mandrel before machining the other holes and the cycloidal wheel profile. While this ensures the positional accuracy of all holes except the through hole of the cycloidal wheel's input shaft relative to the cycloidal wheel profile, the machining of the through hole of the cycloidal wheel's input shaft is not completed in a single clamping operation. This makes it difficult to guarantee the positional accuracy of the through hole and the cycloidal wheel profile, which are the most critical requirements for cycloidal wheel machining.

[0118] To perform a single-position machining of the cycloidal wheel, the clamping method was changed: First, a blank was prepared, and the hole system on the blank was used as a rough reference (two pins on one side) for initial positioning. Then, a pressure plate was placed on the outside of the cycloidal wheel to press down the part close to the cycloidal wheel contour. The initial positioning element of the cycloidal wheel was removed, and the hole system of the cycloidal wheel was machined. Then, a disc-shaped pressure plate and bolts passing through the hole system of the cycloidal wheel were used to clamp the middle of the cycloidal wheel. The pressure plate on the outside of the cycloidal wheel was removed, and the contour of the cycloidal wheel was machined.

[0119] In addition, in some embodiments, regarding the design of the cycloidal wheel process, a blank is prepared first, and then the two sides of the cycloidal wheel are ground with each other as references to determine the thickness of the cycloidal wheel and improve the parallelism accuracy of the two sides.

[0120] In addition, in some embodiments, after the fixture is installed on the machine tool table, the mating surface between the fixture body and the cycloidal wheel is first "self-aligned" to minimize the positional error between the fixture and the machine tool.

[0121] In the middle of the fixture body, there are three layers of stepped holes with the same number as the cycloidal wheel hole system (the upper layer is for milling cutter clearance, the lower layer is for bolt connection, and the middle layer is for positioning); two initial positioning pins (round pin and flat pin, forming a two-pin face with the mating surface of the cycloidal wheel and the fixture body) are set, which pass through the pressure plate and the cycloidal wheel blank, and cooperate with the middle hole of the three-layer stepped holes of the fixture body for initial positioning; after initial positioning, the pressure plate and the cycloidal wheel blank are pressed onto the fixture body with ordinary bolts.

[0122] A tooth profile pressure plate is evenly distributed around the circumference on the outer side of the cycloidal wheel blank. The pressure plate is mounted above a floating fixture via springs, studs, and nuts, and can rotate around the studs. To increase the contact area between the pressure plate and the cycloidal wheel, the head of the pressure plate is arc-shaped. The pressure plate has two positions: pressing against the circumference of the cycloidal wheel and idle. When the cycloidal wheel blank is fixed to the fixture and the pressure plate is idle, the tooth profile can be machined; when the pressure plate presses against the circumference of the cycloidal wheel and the clamping bolts, initial positioning pins, and pressure plate are removed, the cycloidal wheel hole system can be machined. Therefore, the machining of the cycloidal wheel tooth profile and all holes can be completed in one positioning operation.

[0123] In summary, the above-described CNC milling method for cycloidal gears has the following advantages:

[0124] 1. By establishing a macro-program mathematical calculation model, simplified mathematical calculations are performed, and an effective contour milling cycloidal wheel contour tool path is proposed to alleviate the problems of milling cutter deformation and tool marks in contour machining.

[0125] 2. By providing a macro programming design method that is adapted to domestic CNC systems and simplifies calculations, the application scope of domestic CNC systems can be expanded.

[0126] 3. Based on the machining characteristics of cycloidal wheels, a clamping method is proposed that enables the cycloidal wheel profile and the cycloidal wheel hole system to be positioned once and clamped twice, which is particularly beneficial to improving the relative positional accuracy of the cycloidal wheel profile and the hole system.

[0127] like Figure 5 As shown, the second embodiment of the present invention proposes a CNC milling system for cycloidal wheels, the system comprising:

[0128] Coordinate system construction module 10 is used to construct a coordinate system based on the cycloidal wheel structure, and sets the zero point of the coordinate system at the center of the cycloidal wheel. z The zero point is set on the surface along the thickness direction of the cycloidal wheel. The Z-axis is perpendicular to the plane where the cycloidal wheel is located, and the positive direction is away from the cycloidal wheel. The Y-axis passes through the midpoint of the cycloidal wheel tooth groove and is perpendicular to the Z-axis. The positive direction is away from the cycloidal wheel. The X-axis is determined according to the right-hand Cartesian principle.

[0129] Path planning module 20 is used to plan tool paths according to the coordinate system, including designing the tool approach and retraction methods, cutting methods, and cutting directions;

[0130] The curve equation construction module 30 is used to construct the first curve equation of the cycloidal wheel profile, with variable t, the variable t ranging from 0 to 1, and construct the second curve equation of the conjugate pinwheel with the cycloidal wheel based on the first curve equation;

[0131] The offset curve equation construction module 40 is used to construct the offset curve equation of the second curve equation, wherein the offset curve equation is the tool trajectory equation for milling a cycloidal wheel profile with a single tooth groove.

[0132] Tool position coordinate calculation module 50, used to calculate variable t The stepping parameters are used to obtain the coordinates of each tool position point for machining the single tooth groove of the cycloidal wheel based on the tool path and the tool trajectory equation.

[0133] The milling execution module 60 is used to design milling rules based on the tool path and the coordinates of each tool position point, and to mill the cycloidal wheel according to the milling rules.

[0134] While embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations fall within the scope and spirit of the invention as set forth in the claims. Furthermore, the invention described herein may have other embodiments and can be implemented or carried out in various ways.

Claims

1. A CNC milling method for cycloidal gears, characterized in that, The method includes: A coordinate system is constructed based on the structure of the cycloidal wheel, and the zero point of the coordinate system is set at the center of the cycloidal wheel. z The zero point is set on the surface along the thickness direction of the cycloidal wheel. The Z-axis is perpendicular to the plane where the cycloidal wheel is located, and the positive direction is away from the cycloidal wheel. The Y-axis passes through the midpoint of the cycloidal wheel tooth groove and is perpendicular to the Z-axis. The positive direction is away from the cycloidal wheel. The X-axis is determined according to the right-hand Cartesian principle. The tool path is planned according to the coordinate system, including the design of the tool approach and retraction methods, cutting methods, and cutting directions. Construct the first curve equation of the cycloidal wheel profile, let the variable t be, the variable t vary from 0 to 1, and construct the second curve equation of the conjugate pinwheel with the cycloidal wheel based on the first curve equation; Based on the coordinate system, the equation of the first curve is constructed using the following formula: ； in, , ; The radius of the circle at the center of the needle teeth. The number of teeth on the cycloidal wheel. = +1 represents the number of teeth on the pinwheel. The amplitude coefficient, The radius of the needle teeth. X represents the relative rotation angle of the pinwheel, and X and Y are the coordinates of points on the cycloidal wheel profile curve. make Then the equation of the second curve is: ； in, , The second curve equation of the cycloidal wheel and its conjugate pinwheel is given by the coordinates of the single tooth groove curve point at time t. Construct the offset curve equation of the second curve equation, wherein the offset curve equation is the tool trajectory equation for milling a single tooth groove of a cycloidal wheel profile; Depend on ,but: ； make , , The expression for the tool trajectory equation is as follows: ； in, , The coordinates of the tool position point for the cycloidal profile single-tooth groove tool trajectory. e is the tool offset distance. Where is the tool radius, and 'a' is the machining allowance; With variables t The stepping parameters are used to obtain the coordinates of each tool position point for machining the single tooth groove of the cycloidal wheel based on the tool path and the tool trajectory equation. The milling rules are designed based on the tool path and the coordinates of each tool position point, and the cycloidal wheel is milled according to the milling rules. The cycloidal wheel blank is roughly positioned by its internal hole system. The outer periphery of the cycloidal wheel is then clamped. The rough positioning element is then removed, the internal hole system of the cycloidal wheel is machined, the internal hole system of the cycloidal wheel is clamped again, the outer periphery of the cycloidal wheel is loosened, and the cycloidal contour is milled.

2. The CNC milling method for cycloidal gears according to claim 1, characterized in that, The toolpath planning according to the coordinate system includes designing the tool approach and retraction methods, cutting methods, and cutting directions; including: The tool advance and retraction method is as follows: circular arc tangential advance and circular arc tangential retraction are adopted, and the cutting start point and cutting end point of the cycloidal profile are set at the apex of the cycloidal gear tooth profile, while the starting point of the circular arc tangential advance and the retraction point of the circular arc tangential retraction are set on the radial extension line of the apex of the cycloidal gear tooth profile. The cutting method is as follows: milling the cycloidal wheel profile using a layered contour cutting method; The cutting direction is as follows: the milling cutter starts from the starting point of the tangential infeed of the circular arc, moves along the circular arc tangent to the tooth profile to the vertex of the cycloidal profile tooth profile, and the vertex of the tooth profile serves as the starting point of the cycloidal profile cutting. Then, it cuts each of the remaining tooth profiles in sequence until it returns to the starting point of the cutting. Then, it overlaps one tooth gap to reach the vertex of the tooth profile, and the vertex of the tooth profile serves as the ending point of the cycloidal profile cutting. Finally, it cuts out from the vertex of the tooth profile along the circular arc tangent to the tooth profile and reaches the retraction point of the tangential retraction of the circular arc.

3. The CNC milling method for cycloidal gears according to claim 2, characterized in that, The step of designing milling rules based on the tool path and coordinates of each tool position point, and milling the cycloidal wheel according to the milling rules, includes: Step S01: Assign values ​​to the machining parameters of the cycloidal wheel; Step S02: Assign values ​​to the layer thickness of the cycloidal wheel, including the starting layer, the ending layer, and the layer step; Step S03: Initialize the program, move the tool to the safe plane, start the spindle, and turn on the coolant; Step S04: Assign the variable t to 0, obtain the cutting start point coordinates and tool start point coordinates of the cycloidal tooth profile, move the tool to the X and Y coordinate positions of the tool start point, and prepare for cutting; Step S05: Use the G01 command to move the tool to the current cutting layer thickness position; Step S06: Use the circular interpolation command to make the tool cut into the cutting starting point of the cycloidal gear tooth profile in an arc manner; Step S07: Assign values ​​to the cycloidal wheel tooth count parameters, which include the starting tooth count, the ending tooth count, and the tooth count step value; Step S08: Set the coordinate rotation angle according to the number of teeth to be processed, and reassign values ​​to the variable t, including the initial value, the final value, and the step value; Step S09: Calculate the coordinates of the single-tooth groove tool trajectory point of the cycloidal wheel based on the current t value; Step S10: Use the G01 command to perform linear interpolation machining on the calculated point coordinates to form the machining path of the cycloidal wheel profile; Step S11: Perform a step operation on variable t and determine whether the value of t after the step has reached the final value. If the final value has been reached, the tool is now at the current machining tooth profile vertex, and then proceed to step S12. If the final value has not been reached, return to step S09. Step S12: Perform a step operation on the number of teeth and determine whether all teeth have been processed. If all teeth have not been processed, return to step S07. If all teeth have been processed, proceed to step S13. Step S13: Reassign the variable t to 1, and obtain the coordinates of the end point of the cycloidal profile cutting and the coordinates of the retraction point of the circular arc tangential retraction; Step S14: Use the G01 command to cut the tool to the cutting endpoint of the cycloidal profile; Step S15: Using the circular interpolation command, the tool moves from the cutting endpoint of the cycloidal profile to the retraction point of the circular tangential retraction. Step S16: Lift the tool, cancel coordinate rotation, perform step operation on the layer thickness, and determine whether the current layer thickness meets the requirements; if it does not meet the requirements, return to step S04; if it meets the requirements, the cutting ends.

4. The CNC milling method for cycloidal gears according to any one of claims 1-3, characterized in that, The tool position points include the starting point of the circular arc tangential infeed, the starting point of the cycloidal profile cutting, each tooth profile point, the ending point of the cycloidal profile cutting, and the retraction point of the circular arc tangential retraction.

5. A CNC milling system for cycloidal gears, used to implement the CNC milling method for cycloidal gears as described in any one of claims 1-4, characterized in that, The system includes: The coordinate system construction module is used to construct a coordinate system based on the cycloidal wheel structure, setting the zero point of the coordinate system at the center of the cycloidal wheel. z The zero point is set on the surface along the thickness direction of the cycloidal wheel. The Z-axis is perpendicular to the plane where the cycloidal wheel is located, and the positive direction is away from the cycloidal wheel. The Y-axis passes through the midpoint of the cycloidal wheel tooth groove and is perpendicular to the Z-axis. The positive direction is away from the cycloidal wheel. The X-axis is determined according to the right-hand Cartesian principle. The path planning module is used to plan the tool path according to the coordinate system, including designing the tool approach and retraction methods, cutting methods, and cutting directions. The curve equation construction module is used to construct the first curve equation of the cycloidal wheel profile. Let the variable t be a variable that varies from 0 to 1, and construct the second curve equation of the conjugate pinwheel with the cycloidal wheel based on the first curve equation. The offset curve equation construction module is used to construct the offset curve equation of the second curve equation, wherein the offset curve equation is the tool trajectory equation for milling a cycloidal wheel profile with a single tooth groove. The tool position coordinate calculation module is used to calculate the coordinates of the tool position points using variables. t The stepping parameters are used to obtain the coordinates of each tool position point for machining the single tooth groove of the cycloidal wheel based on the tool path and the tool trajectory equation. The milling execution module is used to design milling rules based on the tool path and the coordinates of each tool position point, and to mill the cycloidal wheel according to the milling rules.

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