A non-equal interval milling method for the inner cavity rib plate of an injection molding machine mold plate casting

Abstract

The application relates to the technical field of metal cutting, and discloses a non-equal-interval milling method for an inner cavity rib plate of an injection molding machine mold plate casting, which comprises the following steps: establishing a polar coordinate system with the geometric center of the casting as the origin, dividing a feeding path into a first feeding sub-path and a second feeding sub-path which are centrally symmetrical; controlling a milling cutter to alternately cut between the two sub-paths and jump after a preset stroke ends, and utilizing heat energy to alternately conduct and offset the thermal micro-displacement of a processing area; collecting a main shaft driving current signal and extracting real-time torque characteristic values, calculating a machine tool letting-in vector caused by stress release according to the torque deviation of mirror-symmetrical points, and then generating a vector compensation instruction to correct the milling cutter coordinates, through the load balancing mechanism of the mirror-image feeding path, the asymmetric release of the residual stress in the casting is balanced, the machine tool letting-in deviation is reduced, and the geometric precision of a complex inner cavity rib plate cutting track is ensured.

Description

Technical Field

[0001] This invention belongs to the field of metal cutting technology, and particularly relates to a non-equidistant milling method for the inner cavity rib plate of an injection molding machine template casting. Background Technology

[0002] In the current manufacturing process of injection molding machine template castings, milling is often used to finish the internal ribs to ensure that the template has the preset dynamic stiffness and stress distribution characteristics. The internal ribs of the injection molding machine template casting exhibit non-equidistant distribution characteristics based on mechanical topology optimization, and the machining points are usually located in the deep cavity region with a large length-to-diameter ratio. The existing milling path selects constant radial cutting width and constant feed rate as the process standard. When the long shank end mill cuts into the transition area of ​​the non-equidistant ribs, the wrap angle of the cutting tool suddenly increases due to the nonlinear reduction of the rib spacing. QT500 ductile iron material has the characteristics of high strength, high toughness, high hardness and low thermal conductivity, which leads to severe heat accumulation at the cutting part and induces local micro-thermal expansion. As the cutting torque increases instantaneously with the sudden change of the wrap angle, the system generates phase lag type regenerative chatter, causing fatigue chipping of the cutting edge and elastic deflection deviation of the low stiffness long shank tool.

[0003] Conventional improvement schemes attempt to maintain process stability by globally reducing the cutting speed or increasing the finishing allowance. However, reducing the speed significantly weakens the efficiency of finishing operations, while increasing the allowance makes it more difficult to control the cutting load in subsequent processes. Because the existing path planning logic ignores the differentiated contribution of non-equidistant ribs to the local equivalent stiffness of the workpiece, a mismatch occurs between the tool force vector and the workpiece stiffness field, causing the release process of anisotropic internal stress in the casting to lose symmetry, resulting in microscopic deflection deformation of the entire template. Optimizing the stress state is often achieved by improving the template geometry. For example, Chinese invention patent application CN116330589A discloses a lightweight template structure for injection molding machines. By symmetrically distributing hollow designs on the template front plate, reinforcing ribs, and tie rod seats, stress concentration is alleviated from a structural topology perspective. This scheme focuses on reducing weight through static structural design of the workpiece. However, it cannot solve the thermal accumulation drift caused by the asymmetry of the cutting trajectory and the trajectory deviation caused by the asymmetric release of residual stress in the casting during the dynamic milling process.

[0004] Therefore, how to establish a dynamic mapping relationship between cutting parameters, path topology and workpiece local stiffness and thermal deformation, and use path reconstruction to counteract dynamic instability and physical yielding errors in the cutting process, has become the technical problem to be solved by this invention. Summary of the Invention

[0005] This invention discloses a method for milling non-equidistant rib plates in the inner cavity of injection molding machine template castings, comprising the following steps:

[0006] Step S1: Establish a polar coordinate system with the geometric center of the injection molding machine template casting as the origin. Divide the preset non-equal spacing feed path into a mirror feed path that is 180° rotationally symmetrical about the origin. The mirror feed path includes a centrally symmetrical first feed sub-path and a second feed sub-path.

[0007] Step S2: Drive the milling cutter to perform periodic alternating cutting between the first feed sub-path and the second feed sub-path. Control the milling cutter to jump to the corresponding other feed sub-path after performing a fixed length of preset stroke L in each feed sub-path to perform the same step length. Use the milling heat energy of the mirror feed path in the symmetrical dimension to alternately accumulate and counteract the thermal micro-deformation of the inner cavity of the injection molding machine template casting.

[0008] Step S3: Acquire the drive current signal during the milling cutter cutting process through the milling machine spindle drive system, and extract the fundamental frequency component of the drive current signal to obtain the real-time torque characteristic value that characterizes the instantaneous change in cutting resistance;

[0009] Step S4: Extract the real-time torque deviation at the symmetrical sampling points of the first feed sub-path and the second feed sub-path. Based on the real-time torque deviation, calculate the machine tool deflection vector caused by the asymmetric release of residual stress in the injection molding machine template casting. The machine tool deflection vector represents the microscopic offset of the milling cutter from the preset non-equal interval feed path in the polar coordinate system.

[0010] Step S5: Generate feed vector compensation value based on machine tool deflection vector, correct the three-dimensional coordinates of the feed axis of the milling cutter in the next cutting cycle, and compensate for machining drift by adjusting axial depth of cut and radial offset to maintain the geometric accuracy of the cutting trajectory of the inner cavity rib plate of the injection molding machine template casting.

[0011] Preferably, the preset stroke L in step S2 is set based on the local stiffness of the rib and the thermal diffusivity of the material: the local section modulus of the rib in the area where the first feed sub-path and the second feed sub-path are located is extracted, and combined with the thermophysical parameters of the ductile iron material, a step constraint model with the goal of minimizing thermally induced displacement is established; the maximum limit value of the preset stroke L is calculated according to the step constraint model, and the preset stroke L is set to 5mm to 50mm.

[0012] Preferably, while performing step S2, a dynamic stiffness compensation step for the cutting system is also included: extracting the dynamic response frequency of the contact interface between the milling cutter and the rib plate based on the spacing evolution data of the mirror feed path; superimposing a micro-compensation trajectory on a preset non-equal spacing feed path based on the dynamic response frequency, wherein the fluctuation frequency of the micro-compensation trajectory is non-harmonic with the natural frequency of the milling cutter system to increase the damping of the cutting process.

[0013] Preferably, the three-dimensional coordinates of the feed axis of the milling cutter in the next cutting cycle in step S5 include: establishing a residual stress distribution mapping table for the injection molding machine template casting, mapping the real-time torque characteristic value to the cutting resistance increment of the ductile iron material; comparing the resistance deviation at the symmetrical position in the mirror feed path, and calculating the machining offset of the injection molding machine template casting caused by the asymmetrical release of stress.

[0014] Preferably, the distribution of the mirror feed path is arranged according to the stress symmetry axis of the injection molding machine template casting, so that the thermal expansion vectors generated by the first feed sub-path and the second feed sub-path during milling are orthogonal or opposite to each other in the polar coordinate system, so as to maintain the stability of the geometric reference of the machined surface during alternating cutting.

[0015] Preferably, the compensation amplitude A of the micro-compensation trajectory satisfies the following quantization relationship: ,in, Here, ΔI is the preset response adjustment coefficient, and ΔI is the instantaneous fluctuation value of the drive current signal. The natural frequency of the milling cutter system is used to compensate for the amplitude A, which is adjusted in real time according to the change of cutting load. When the milling cutter enters the high-rigidity region, it introduces interference displacement and disrupts the chatter feedback chain in the machining process.

[0016] Preferably, in the narrow spacing region of the preset non-equal spacing feed path, the linear feed trajectory is replaced with a spiral undulating feed trajectory, and the rotation direction of the spiral undulating feed trajectory is consistent with the rotation direction of the chip removal groove of the milling cutter; the centrifugal airflow generated by the rotation of the milling cutter is used to discharge the cutting chips to the adjacent wide spacing region.

[0017] Preferably, the helix angle of the spiral undulating feed trajectory is inversely proportional to the width of the narrow spacing region. The helix angle is increased when the milling cutter penetrates deep into the bottom of the injection molding machine template casting cavity to increase the airflow's chip removal pressure at the bottom of the deep cavity.

[0018] Preferably, the method further includes a feed density zoning control step: dividing the preset non-equal spacing feed path into a high path density segment and a low path density segment, driving the milling cutter to switch feed speeds between different density segments; using a constant power mode for machining in the low path density segment, and switching to a constant load mode for finishing in the high path density segment.

[0019] Preferably, in the last alternating feed after the completion of the full path machining, the milling cutter is controlled to perform a reverse stress balancing finishing step. The feed direction of the reverse stress balancing finishing step is opposite to the initial milling direction of the preset non-equal spacing feed path, and the tensile stress remaining on the surface of the stiffener is offset by the reverse shearing action.

[0020] Compared with existing technologies, the non-equidistant milling method for the inner cavity ribs of injection molding machine template castings of the present invention has the following advantages:

[0021] 1. In the inner cavity stiffener of the injection molding machine template casting, by acquiring the spatial distribution characteristics of the inner cavity stiffener and establishing a local stiffness mapping model, the feed path is divided into a forced vibration sensitive area and a regenerative chatter sensitive area. The center distance between adjacent tool paths is reduced as the stiffener spacing increases. This reverse mapping mechanism between the path topology and the local stiffness of the workpiece enables the rate of change of cutting torque and the rate of change of local stiffness of the workpiece to physically cancel each other in phase. This changes the pulse-like step of cutting load caused by the reduction of spacing in traditional equal-spacing milling, eliminates the regenerative chatter induced by the sudden change of cutting wrap angle in the deep cavity machining of QT500 ductile iron, and reduces the amplitude of alternating thermal stress cycle of the cutting insert under variable stiffness conditions.

[0022] 2. Extract the radial retraction vector of the tool caused by the change in the cutting wrap angle at the end node of the non-equal spacing step path, and superimpose a micro-cycloidal compensation path with the opposite direction of the radial retraction vector. By mapping the trajectory radius of the micro-cycloidal path with the hardness of the casting material and the tool overhang length, the dynamic reverse force of the cutting resistance is used to counteract the static elastic retraction of the long shank end mill, eliminate the residual steps caused by the tool retraction phenomenon at the root of the deep cavity, realize the arc transition at the junction of the side wall and bottom surface of the rib plate, ensure that the machined rib plate entity accurately reproduces the dynamic stiffness distribution of the topology design, and avoid stress concentration caused by machining errors.

[0023] 3. The feed path is arranged into a mirror path group that is rotationally symmetrical about the geometric center of gravity of the injection molding machine template casting. During the milling process, the tool is controlled to alternately switch feed between two sub-paths in each mirror path group. By utilizing the physical counterbalance of the residual stress inside QT500 ductile iron during the release process in different directions, the timing of the removal of surface metal of the casting is symmetrically balanced in space. Through the topological reconstruction of the path timing, deformation self-compensation during the machining process is achieved, which solves the problem of asymmetric deformation caused by thermal coupling in the finishing of large castings and ensures the mathematical accuracy of the non-equidistant milling logic throughout the entire path cycle. Attached Figure Description

[0024] Figure 1 This is a flowchart of the non-equal spacing milling and dynamic compensation process for injection molding machine templates according to the present invention;

[0025] Figure 2 This is a diagram of the control module and data flow architecture of the milling system of the present invention. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0027] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, bottom, transverse, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0028] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection of 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.

[0029] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0030] A method for milling non-equidistant rib plates in the inner cavity of an injection molding machine template casting includes the following steps:

[0031] Step S1: Establish a polar coordinate system with the geometric center of the injection molding machine template casting as the origin. Divide the preset non-equal spacing feed path into a mirror feed path that is 180° rotationally symmetrical about the origin. The mirror feed path includes a centrally symmetrical first feed sub-path and a second feed sub-path.

[0032] Step S2: Drive the milling cutter to perform periodic alternating cutting between the first feed sub-path and the second feed sub-path. Control the milling cutter to jump to the corresponding other feed sub-path after performing a fixed length of preset stroke L in each feed sub-path to perform the same step length. Use the milling heat energy of the mirror feed path in the symmetrical dimension to alternately accumulate and counteract the thermal micro-deformation of the inner cavity of the injection molding machine template casting.

[0033] Step S3: Acquire the drive current signal during the milling cutter cutting process through the milling machine spindle drive system, and extract the fundamental frequency component of the drive current signal to obtain the real-time torque characteristic value that characterizes the instantaneous change in cutting resistance;

[0034] Step S4: Extract the real-time torque deviation at the symmetrical sampling points of the first feed sub-path and the second feed sub-path. Based on the real-time torque deviation, calculate the machine tool deflection vector caused by the asymmetric release of residual stress in the injection molding machine template casting. The machine tool deflection vector represents the microscopic offset of the milling cutter from the preset non-equal interval feed path in the polar coordinate system.

[0035] Step S5: Generate feed vector compensation value based on machine tool deflection vector, correct the three-dimensional coordinates of the feed axis of the milling cutter in the next cutting cycle, and compensate for machining drift by adjusting axial depth of cut and radial offset to maintain the geometric accuracy of the cutting trajectory of the inner cavity rib plate of the injection molding machine template casting.

[0036] Preferably, the preset stroke L in step S2 is set based on the local stiffness of the rib and the thermal diffusivity of the material: the local section modulus of the rib in the area where the first feed sub-path and the second feed sub-path are located is extracted, and combined with the thermophysical parameters of the ductile iron material, a step constraint model with the goal of minimizing thermally induced displacement is established; the maximum limit value of the preset stroke L is calculated according to the step constraint model, and the preset stroke L is set to 5mm to 50mm.

[0037] Preferably, while performing step S2, a dynamic stiffness compensation step for the cutting system is also included: extracting the dynamic response frequency of the contact interface between the milling cutter and the rib plate based on the spacing evolution data of the mirror feed path; superimposing a micro-compensation trajectory on a preset non-equal spacing feed path based on the dynamic response frequency, wherein the fluctuation frequency of the micro-compensation trajectory is non-harmonic with the natural frequency of the milling cutter system to increase the damping of the cutting process.

[0038] Preferably, the three-dimensional coordinates of the feed axis of the milling cutter in the next cutting cycle in step S5 include: establishing a residual stress distribution mapping table for the injection molding machine template casting, mapping the real-time torque characteristic value to the cutting resistance increment of the ductile iron material; comparing the resistance deviation at the symmetrical position in the mirror feed path, and calculating the machining offset of the injection molding machine template casting caused by the asymmetrical release of stress.

[0039] Preferably, the distribution of the mirror feed path is arranged according to the stress symmetry axis of the injection molding machine template casting, so that the thermal expansion vectors generated by the first feed sub-path and the second feed sub-path during milling are orthogonal or opposite to each other in the polar coordinate system, so as to maintain the stability of the geometric reference of the machined surface during alternating cutting.

[0040] Preferably, the compensation amplitude A of the micro-compensation trajectory satisfies the following quantization relationship: ,in, Here, ΔI is the preset response adjustment coefficient, and ΔI is the instantaneous fluctuation value of the drive current signal. The natural frequency of the milling cutter system is used to compensate for the amplitude A, which is adjusted in real time according to the change of cutting load. When the milling cutter enters the high-rigidity region, it introduces interference displacement and disrupts the chatter feedback chain in the machining process.

[0041] Preferably, in the narrow spacing region of the preset non-equal spacing feed path, the linear feed trajectory is replaced with a spiral undulating feed trajectory, and the rotation direction of the spiral undulating feed trajectory is consistent with the rotation direction of the chip removal groove of the milling cutter; the centrifugal airflow generated by the rotation of the milling cutter is used to discharge the cutting chips to the adjacent wide spacing region.

[0042] Preferably, the helix angle of the spiral undulating feed trajectory is inversely proportional to the width of the narrow spacing region. The helix angle is increased when the milling cutter penetrates deep into the bottom of the injection molding machine template casting cavity to increase the airflow's chip removal pressure at the bottom of the deep cavity.

[0043] Preferably, the method further includes a feed density zoning control step: dividing the preset non-equal spacing feed path into a high path density segment and a low path density segment, driving the milling cutter to switch feed speeds between different density segments; using a constant power mode for machining in the low path density segment, and switching to a constant load mode for finishing in the high path density segment.

[0044] Preferably, in the last alternating feed after the completion of the full path machining, the milling cutter is controlled to perform a reverse stress balancing finishing step. The feed direction of the reverse stress balancing finishing step is opposite to the initial milling direction of the preset non-equal spacing feed path, and the tensile stress remaining on the surface of the stiffener is offset by the reverse shearing action.

[0045] Example 1: When the system faces the finishing condition of non-uniformly spaced ribs inside the deep cavity of a 2000T large injection molding machine template casting, the non-uniformly spaced milling method for the ribs inside the injection molding machine template casting is executed. The long shank milling cutter cuts from the wide-spacing area into the narrow-spacing transition area, causing a non-linear abrupt change in the cutting wrap angle. The high strength, high toughness, high hardness, and low thermal conductivity of QT500 ductile iron material cause an instantaneous heat accumulation at the cutting part, inducing local thermal expansion. The metal removal sequence caused by unidirectional continuous tool feed is spatially asymmetrical, resulting in an asymmetrical release of residual stress inside the workpiece. Conventional path planning logic struggles to match the differences in cutting dynamics parameters and the distribution of the local equivalent stiffness field of the casting, leading to overall deflection deformation of the mold template and elastic deflection deviation of the long-shank tool at the deep cavity root. A polar coordinate system is established with the geometric center of the injection molding machine mold casting as the origin. The preset non-equidistant feed path is divided into mirror feed paths that are 180° rotationally symmetrical about the origin. Each mirror feed path includes a centrally symmetrical first feed sub-path and a second feed sub-path. The end mill is driven to perform periodic alternating cutting between the first and second feed sub-paths, controlling the end mill's position in each... After a fixed-length preset stroke L is executed in one feed subpath, the process jumps to the corresponding other feed subpath and executes the same step length. The local section modulus of the ribs in the areas where the first and second feed subpaths are located is extracted. Combined with the thermophysical parameters of QT500 ductile iron material, the preset stroke L is set to 5mm to 50mm. This alternating cutting sequence allows the heat energy of adjacent cutting areas to be conducted and diffused through the casting body. The alternating accumulation of milling heat energy in the symmetrical dimension of the mirror feed path offsets the thermally induced micro-displacement of the inner cavity of the injection molding machine template casting, suppressing local thermal stress concentration. During operation, the control system limits the duration of a single continuous cut for the first and second feed subpaths to no more than 1500ms. Combined with a preset stroke of 5mm to 50mm, it ensures that the dwell time of the cutting heat source at each machining point is below the material's thermal saturation threshold. Utilizing the 0.012 cm² / s thermal diffusivity of QT500 ductile iron material, heat is conducted and diffused into the depth of the casting matrix within a 4000ms idle heat dissipation period. This controls the local instantaneous temperature rise in the machining area to below 5℃ and limits the static displacement deviation caused by thermal expansion to within 0.004mm.

[0046] The driving current signal during the milling cutter cutting process is collected, the fundamental frequency component of the driving current signal is extracted, and the real-time torque characteristic value representing the instantaneous change in cutting resistance is obtained. The real-time torque deviation at the symmetrical sampling points of the first and second feed sub-paths is extracted. Based on the real-time torque deviation, the machine tool deflection vector caused by the asymmetric release of residual stress in the injection molding machine template casting is calculated. Based on the machine tool deflection vector, a feed vector compensation value is generated to correct the three-dimensional coordinates of the feed axis of the milling cutter in the next cutting cycle. According to the spacing evolution data of the mirrored feed path, the dynamic response frequency of the contact interface between the milling cutter and the rib plate is extracted. Based on the dynamic response frequency, a micro-compensation trajectory is superimposed on the preset non-equidistant feed path. The compensation amplitude A of the micro-compensation trajectory satisfies the formula... Where A is the compensation amplitude of the micro-compensation trajectory. Here, ΔI is the preset response adjustment coefficient, and ΔI is the instantaneous fluctuation value of the drive current signal. The natural frequency of the milling cutter system and the fluctuation frequency of the micro-compensation trajectory are non-harmonic distributions of the natural frequency of the milling cutter system. In the narrow spacing region of the preset non-equal spacing feed path, the linear feed trajectory is replaced with a spiral fluctuation feed trajectory consistent with the rotation direction of the milling cutter chip flute. The centrifugal airflow generated by the rotation of the milling cutter is used to discharge the cutting chips to the adjacent wide spacing region. The stable symmetrical thermal field eliminates the thermal drift interference in the current feature extraction process. The spatial symmetry of the alternating cutting path is established based on the coordinate correction amount calculated by the driving current signal, maintaining the trajectory geometric accuracy in the deep cavity discontinuous cutting environment. The milling cutter is controlled to perform a reverse stress balancing finishing step in the last alternating feed after the end of the full path machining. The feed direction of the reverse stress balancing finishing step is opposite to the initial milling direction of the preset non-equal spacing feed path. The reverse shearing action cancels the tensile stress remaining on the surface of the rib plate, physically eliminating the machining offset caused by the asymmetric release of stress at the root of the deep cavity. The junction of the side wall and bottom surface of the rib plate after machining is a continuous arc surface, and the geometric dimensions of the solid structure match the dynamic stiffness distribution parameters of the topology optimization design.

[0047] Example 2: A milling dynamics test platform was established, using a five-axis CNC machining center with a positioning accuracy of 0.001mm. The machining object was a 40t solid 2000T large injection molding machine template casting made of QT500 ductile iron. The spindle drive module was connected to a high-frequency current sensor with a sampling rate of 10kHz to collect raw drive current data. The data processing module was configured with a sliding sampling window of 1024 points and a window overlap rate of 50%. In each interpolation cycle, the raw drive current signal was subjected to weighted average filtering and noise reduction. A digital bandpass filter was used to lock the frequency range from 15Hz to 450Hz. The effective load frequency band is used to extract the fundamental frequency component, which is then used as the physical input data for calculating the cutting resistance fluctuation. Gaussian white noise with a signal-to-noise ratio of 20dB is injected into the spindle control system and superimposed with power frequency harmonic interference of 50Hz. The parameter value of the preset stroke L is set, which balances the cutting heat energy diffusion efficiency and the machine tool non-cutting idle time consumption. The local section modulus and thermal diffusivity restrict the heat energy conduction. When the local section modulus decreases, the heat accumulated in a single cut leads to an increase in deformation. The lower limit of the preset stroke L is set, and the parameter range of the preset stroke L is established as 5mm to 50mm based on the thermo-mechanical coupling finite element analysis model.

[0048] A multidimensional experimental control group was set up. Control group one used a unidirectional continuous tool path without alternating jumps or compensation; control group two used a periodic alternating cutting path with a preset stroke L of 25 mm without micro-compensation trajectory; control group three, which exceeded the range, had a preset stroke L of 3 mm; and control group four, which exceeded the range, had a preset stroke L of 60 mm. The sample group of this invention had a preset stroke L of 25 mm and a response adjustment coefficient. The value is 0.15 mm·Hz / A, and the natural frequency of the milling cutter system is measured. The frequency is 850Hz; the CNC machine tool is driven to execute each group of machining programs, and the original drive current signal is collected. The unprocessed signal shows a fluctuating amplitude between 15.2A and 28.6A. The power frequency interference masks the cutting resistance characteristics. The fundamental frequency component of the original drive current signal is extracted, Gaussian white noise and power frequency harmonic interference are filtered out, and a smooth real-time torque characteristic curve is obtained. The instantaneous current fluctuation value ΔI at the symmetrical sampling point of the first feed sub-path and the second feed sub-path of the sample group of this invention is extracted to be 1.85A. Based on the extracted difference, the machine tool deflection vector at the current cutting node is calculated to be 0.012mm.

[0049] The dimensional accuracy and local deformation residuals of the casting stiffeners after machining were measured in each group of experiments. The deformation residual of the sample group of this invention was 0.018 mm and the surface roughness of the sidewall was 1.25 μm. The deformation residual of control group one was 0.085 mm and showed a unidirectional thermal deflection. The deformation residual of control group two was 0.042 mm. The out-of-range control group four had a non-linear inflection point and reached 0.076 mm because the preset stroke L reached 60 mm, which caused the accumulated heat of a single cut to exceed the local heat conduction threshold of the casting, resulting in thermal stress concentration in the material. The deformation residual of the control group three had a deformation residual of 0.021 mm. The overall machining time increased by 45% compared with the sample group of this invention. The time loss cost was introduced when the lower limit of 5 mm was lowered. The data shows that the symmetrical thermal field constructed by the periodic alternating cutting and the micro-compensation trajectory calculated based on the real-time torque deviation have a superposition effect. Combined with the offsetting of the machining drift caused by the asymmetric release of residual stress inside the casting, the preset stroke L of 5 mm to 50 mm constitutes the parameter range for maintaining the cutting thermal balance and machining efficiency.

[0050] Example 3: When the system faces the initial working condition of planning a cutting path for a specific injection molding machine template casting, the controller extracts the three-dimensional model data of the area to be processed. The system extracts the geometric contour of the spacing evolution interval along the preset non-equal spacing feed path, calculates the local section modulus distribution gradient of adjacent stiffeners, and establishes a three-dimensional transient heat conduction equation based on the obtained local section modulus and the physical parameters of specific heat capacity and thermal conductivity of QT500 ductile iron material. This equation takes the contact area between the cutting edge and the workpiece as the moving heat source and sets the boundary conditions as natural air convection and isothermal conduction at the bottom of the workpiece. The system sets the maximum allowable temperature rise threshold of the cutting area, which is lower than the critical temperature for solid-state phase transformation of QT500 ductile iron material. The calculation engine iteratively solves the equation, and calculates the heat source along the first feed path while ensuring that the temperature rise of each calculation node does not exceed the maximum allowable temperature rise threshold. The maximum allowable distance for continuous path movement is established as the parameter benchmark for the preset stroke L. The numerical calibration is completed in the range of 5mm to 50mm to eliminate the risk of thermal runaway caused by empirically set stroke. The preset stroke L determination scheme in step S2 is as follows: Before formal milling, QT500 ductile iron test sample is selected. A thermocouple sensor with a range of 0 to 200℃ and a sampling frequency of not less than 50Hz is installed on the simulated stiffener sidewall. Different continuous cutting displacement process experiments are carried out to obtain the mapping data of temperature rise value ΔT and stiffener thermal displacement δ. Under the condition that δ does not exceed 0.01mm, the corresponding maximum feed length is extracted as the critical input boundary of the step constraint model. The step frequency of the mapping stroke is discretized, and the preset stroke L is calibrated in the range of 5mm to 50mm so that the heat accumulation rate of the first feed sub-path and the second feed sub-path is lower than the heat dissipation rate of the injection molding machine template casting body.

[0051] When the machine tool spindle enters the actual cutting stage, the current sensor acquires the drive current signal at a fixed sampling rate. The system constructs a sliding data sampling window with a fixed time period to receive discrete current data. The data processing module applies the Fast Fourier Transform algorithm to convert it from the time domain to the frequency domain. In the frequency domain spectrum, high-frequency harmonic components with amplitudes lower than the preset background electromagnetic noise threshold are filtered out, and the fundamental frequency interval corresponding to the spindle rotation frequency is locked. Within this fundamental frequency interval, the system finds the peak and extracts the maximum energy spectral density. The fundamental frequency signal is reconstructed back to the time domain through inverse Fourier transform to generate a smooth real-time torque feature value sequence. Based on the interpolation position coordinates of the feed axis, two real-time torque feature values ​​at the centrally symmetrical coordinate points on the first and second feed sub-paths are extracted. The absolute difference between the two is calculated to generate the real-time torque deviation and the instantaneous fluctuation value ΔI of the drive current signal. This end-to-end processing logic filters out random electromagnetic interference and high-frequency machine tool vibration noise in the industrial environment and establishes a monotonic physical mapping relationship between the real-time torque deviation and the machine tool deflection vector.

[0052] To determine the preset response adjustment coefficient in the calculation formula of the compensation amplitude A of the micro-compensation trajectory. Before formal machining, the system initiates a cutting dynamics calibration procedure, driving the milling cutter to cut multiple sets of samples with fixed depth of cut in the scrap area. Simultaneously, it records the instantaneous fluctuation value ΔI of the driving current signal generated by each cutting step and the actual tool deflection measured by the machine tool spindle laser interferometer. The calculation engine applies least squares linear fitting to the recorded instantaneous fluctuation value ΔI and the offset scatter data, extracts the slope of the fitted line, and compares this slope with the natural frequency of the milling cutter system. The product of these two components is set as the preset response adjustment coefficient. The only input value is the instantaneous fluctuation value ΔI of the measured drive current signal, which is substituted into the calculation formula when the micro-compensation trajectory is formally generated. The output micro-compensation trajectory compensation amplitude A is superimposed in the feed control loop through the coordinate offset register at the bottom layer of the 5-axis CNC system on the reverse coordinate offset corresponding to the compensation amplitude A, covering the execution path from parameter calibration to the bottom layer action response to physically offset the machining drift deviation under the deep cavity intermittent cutting environment; the residual stress distribution mapping table construction scheme in step S5 is as follows: the initial stress vector at different polar coordinate positions is measured by X-ray diffractometer in the injection molding machine template casting blank stage. The stress values ​​and corresponding spatial coordinates are stored in the global lookup table of the control system. During the calibration of the tool path, the reference amplitude of the drive current signal under a constant cutting depth is recorded. A proportional mapping function is established between the real-time torque characteristic value increment ΔI and the cutting resistance change ΔF. When the milling cutter alternates between the first and second feed sub-paths, the data processing module extracts the real-time torque deviation at symmetrical sampling points. The deviation is converted into a disturbance torque generated by the asymmetric release of residual stress through the proportional mapping function. Based on the pre-collected dynamic stiffness coefficient of the milling machine spindle end... The computerized tool deflection vector magnitude is used to correct the trajectory offset caused by stress gradient in the three-dimensional coordinate compensation of the feed axis.

[0053] Example 4: When a CNC machine tool faces the on-site deployment of a new batch of injection molding machine template castings, the main control unit initiates the pre-calibration procedure for the dynamic stiffness of the milling cutter system before the actual cutting. The drive module controls the clamped long shank milling cutter to hover in an interference-free coordinate position and applies a step pulse excitation force to the spindle. The vibration sensor collects the ringing signal of the milling cutter during the free decay phase and extracts the initial fundamental frequency peak value through fast Fourier transform. The main control unit writes this initial fundamental frequency peak value into the underlying register as the natural frequency of the milling cutter system. The reference input value is used to synchronously scan the three-dimensional point cloud of the blank allowance distribution in the inner cavity of the current batch of injection molding machine template casting. The main control unit compares the theoretical three-dimensional model with the actual geometric boundary deviation at each node. Based on this, the initial cross-sectional modulus parameters of the regions where the first feed sub-path and the second feed sub-path are located are reconstructed. The initial physical boundary conditions of the thermo-coupled finite element analysis model are updated using the reconstructed parameters.

[0054] When milling a pre-set non-uniform feed path, the computation module periodically updates the inherent frequency in the underlying register based on the frequency shift of the spindle drive current signal, as the amount of metal removed increases and the tool mass distribution changes due to cutting edge wear. The numerical value is determined by the instantaneous fluctuation ΔI of the drive current signal caused by the cutting edge entering the narrow-pitch transition region. The coordinate offset register then retrieves the latest updated natural frequency. Combined preset response adjustment coefficient Substitute into the formula The system outputs the compensation amplitude A of the micro-compensation trajectory within the current interpolation cycle. The CNC system drives the feed axis to generate corresponding coordinate displacement based on this compensation amplitude A. The micro-compensation trajectory generated by the drive milling cutter follows the dynamic impedance change of the tool-workpiece contact interface in real time in the time domain, physically offsetting the spatial tool deflection deviation caused by the decay of the tool's dynamic stiffness parameters over time. The direction of the tool deflection vector is the same as the normal direction of the current feed direction. The calculation of its magnitude is achieved by querying a hexadecimal mapping table pre-stored in the main control unit. This table has a minimum current deviation step of 0.1A. For a 5-axis machine tool with a static stiffness calibration of 150N per micrometer, the real-time torque deviation is mapped to the corresponding physical displacement compensation amount. When the detected real-time torque deviation is 1.5A, the corresponding axial compensation increment output of the mapping table is 0.012mm.

[0055] Example 5: Before the injection molding machine template casting machining task is officially started, in order to establish the response benchmark of the micro-compensation trajectory and establish an abnormal intervention mechanism, the system needs to execute the parameter offline calibration and damping adaptive tuning procedure. The main control unit controls the machine tool to set the gradient cutting test matrix in the process allowance area of ​​the casting. This matrix contains multiple discrete combination parameters of spindle speed and preset stroke L. The machine tool executes the cutting action under each parameter combination in sequence. The current sensor synchronously records the instantaneous fluctuation value ΔI of the drive current signal generated under each working condition. The laser interferometer mounted on the spindle synchronously measures the corresponding machine tool deflection vector. The data processing module extracts the fluctuation value data when the machine tool deflection vector is maintained at the upper limit of the 0.02mm tolerance. This data is established as the start threshold for triggering the micro-compensation trajectory superposition link. This setting procedure anchors the activation condition of the compensation mechanism to the solid machining accuracy requirements.

[0056] The system uses the real-time torque characteristic value sequence accumulated during the previous processing of similar castings as a training dataset to construct an autoregressive integral moving average model. It then calculates the damping correction coefficient, which includes the material hardness fluctuation factor, using the maximum likelihood estimation method. This damping correction coefficient is then compared with the calculation formula. The response adjustment coefficient in A multiplication mapping is established to generate an adaptive parameter matrix and store it in local memory. In the online milling process, when the data monitoring module determines that the amplitude of the fundamental frequency component of the drive current signal exceeds 20% of the upper limit predicted by the autoregressive integral moving average model within five consecutive sampling cycles, the main control system issues a feed hold command. The machine tool suspends the cutting feed axis displacement and keeps the spindle idling to accelerate the natural convection cooling of the cutting area. After the cooling sensor detects that the local temperature of the workpiece has dropped below the phase transformation critical point of QT500 ductile iron, the main control system reduces the preset stroke L of the subsequent cutting path to 50% of the current set value and drives the machine tool to resume alternating cutting actions. This online fault-tolerant mechanism compensates for the limitations of a single geometric correction in perceiving extreme physical disturbances and establishes a thermodynamic safety boundary under complex working conditions.

[0057] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the scope of protection of this application.

Claims

1. A method for milling non-equidistant rib plates in the inner cavity of an injection molding machine template casting, characterized in that, Includes the following steps: Step S1: Establish a polar coordinate system with the geometric center of the injection molding machine template casting as the origin. Divide the preset non-equal spacing feed path into a mirror feed path that is 180° rotationally symmetrical about the origin. The mirror feed path includes a centrally symmetrical first feed sub-path and a second feed sub-path. Step S2: Drive the milling cutter to perform periodic alternating cutting between the first feed sub-path and the second feed sub-path. Control the milling cutter to jump to the corresponding other feed sub-path after performing a fixed length of preset stroke L in each feed sub-path to perform the same step length. Use the milling heat energy of the mirror feed path in the symmetrical dimension to alternately accumulate and counteract the thermal micro-deformation of the inner cavity of the injection molding machine template casting. Step S3: Acquire the drive current signal during the milling cutter cutting process through the milling machine spindle drive system, and extract the fundamental frequency component of the drive current signal to obtain the real-time torque characteristic value that characterizes the instantaneous change in cutting resistance; Step S4: Extract the real-time torque deviation at the symmetrical sampling points of the first feed sub-path and the second feed sub-path. Based on the real-time torque deviation, calculate the machine tool deflection vector caused by the asymmetric release of residual stress in the injection molding machine template casting. The machine tool deflection vector represents the microscopic offset of the milling cutter from the preset non-equal interval feed path in the polar coordinate system. Step S5: Generate feed vector compensation value based on machine tool deflection vector, correct the three-dimensional coordinates of the feed axis of the milling cutter in the next cutting cycle, and compensate for machining drift by adjusting axial depth of cut and radial offset to maintain the geometric accuracy of the cutting trajectory of the inner cavity rib plate of the injection molding machine template casting.

2. The non-equidistant milling method for the inner cavity ribs of an injection molding machine template casting according to claim 1, characterized in that, The preset stroke L in step S2 is set based on the local stiffness of the stiffener and the thermal diffusivity of the material: the local section modulus of the stiffener in the area where the first feed sub-path and the second feed sub-path are located is extracted, and combined with the thermophysical parameters of the ductile iron material, a step constraint model with the goal of minimizing thermally induced displacement is established; the maximum limit value of the preset stroke L is calculated according to the step constraint model, and the preset stroke L is set to 5mm to 50mm.

3. The non-equidistant milling method for the inner cavity ribs of an injection molding machine template casting according to claim 1, characterized in that, While performing step S2, a dynamic stiffness compensation step for the cutting system is also included: extracting the dynamic response frequency of the contact interface between the milling cutter and the rib plate based on the spacing evolution data of the mirror feed path; superimposing a micro-compensation trajectory on the preset non-equal spacing feed path based on the dynamic response frequency, the fluctuation frequency of the micro-compensation trajectory is non-harmonic with the natural frequency of the milling cutter system to increase the damping of the cutting process.

4. The non-equidistant milling method for the inner cavity rib plate of an injection molding machine template casting according to claim 1, characterized in that, The three-dimensional coordinates of the feed axis of the corrected end mill in the next cutting cycle in step S5 include: establishing a residual stress distribution mapping table for the injection molding machine template casting, mapping the real-time torque characteristic value to the cutting resistance increment of the ductile iron material; comparing the resistance deviation at the symmetrical position in the mirror feed path, and calculating the machining offset of the injection molding machine template casting caused by the asymmetrical release of stress.

5. The non-equidistant milling method for the inner cavity rib plate of an injection molding machine template casting according to claim 1, characterized in that, The distribution of the mirror feed path is arranged according to the stress symmetry axis of the injection molding machine template casting, so that the thermal expansion vectors generated by the first feed sub-path and the second feed sub-path during milling are orthogonal or opposite to each other in the polar coordinate system, so as to maintain the stability of the geometric reference of the machined surface during alternating cutting.

6. The non-equidistant milling method for the inner cavity rib plate of an injection molding machine template casting according to claim 3, characterized in that, The compensation amplitude A of the micro-compensation trajectory satisfies the following quantization relationship: ,in, Here, ΔI is the preset response adjustment coefficient, and ΔI is the instantaneous fluctuation value of the drive current signal. The natural frequency of the milling cutter system is used to compensate for the amplitude A, which is adjusted in real time according to the change of cutting load. When the milling cutter enters the high-rigidity region, it introduces interference displacement and disrupts the chatter feedback chain in the machining process.

7. The non-equidistant milling method for the inner cavity rib plate of an injection molding machine template casting according to claim 1, characterized in that, In the narrow-spacing region of the preset non-equal-spacing feed path, the linear feed trajectory is replaced with a helical undulating feed trajectory, and the rotation direction of the helical undulating feed trajectory is consistent with the rotation direction of the chip flute of the milling cutter; the centrifugal airflow generated by the rotation of the milling cutter is used to discharge the cutting chips to the adjacent wide-spacing region.

8. A method for milling non-equidistant rib plates in the inner cavity of an injection molding machine template casting according to claim 7, characterized in that, The helix angle of the spiral undulating feed trajectory is inversely proportional to the width of the narrow spacing region, and the helix angle increases when the milling cutter penetrates to the bottom of the inner cavity of the injection molding machine template casting.

9. A method for milling non-equidistant rib plates in the inner cavity of an injection molding machine template casting according to claim 1, characterized in that, It also includes a feed density zoning control step: dividing the preset non-equal spacing feed path into high path density segments and low path density segments, driving the milling cutter to switch feed speeds between different density segments; using constant power mode for machining in low path density segments, and switching to constant load mode for finishing in high path density segments.

10. A method for milling non-equidistant rib plates in the inner cavity of an injection molding machine template casting according to claim 9, characterized in that, In the last alternating feed after the completion of the full path machining, the milling cutter is controlled to perform the reverse stress balancing finishing step. The feed direction of the reverse stress balancing finishing step is opposite to the initial milling direction of the preset non-equal spacing feed path, and the tensile stress remaining on the surface of the stiffener plate is offset by the reverse shearing action.

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