A water gap milling process for injection molded parts

Abstract

The present application relates to injection molding production and processing technology field, especially to a kind of injection molding water gap milling process, including the following steps: fixed step, pre-weakening step, stress guided fracture step and edge finishing step.The present application is through the fixed jig in water gap milling separation machine, milling assembly, multi-axis drive mechanism, posture adjusting mechanism and separation mechanism, executes pre-weakening, stress guided fracture and edge finishing step, fundamentally eliminates regenerative chatter stress wave, avoids product edge collapse and vibration whitening.It solves the problem of edge collapse and vibration whitening caused by cutting force fluctuation during water gap milling separation of high polymer thin-walled injection molded parts.

Description

Technical Field

[0001] This invention relates to the field of injection molding production and processing technology, and in particular to a sprue milling process for injection molding parts. Background Technology

[0002] In existing technologies, when removing sprues from injection molded parts, CNC milling equipment is typically used to directly mill the connecting area, that is, the sprue is completely cut off and separated from the product in one go by a rotating milling cutter.

[0003] However, for the thin-walled polymer injection molded parts (such as PC, PMMA, etc.) used in head-up displays, they have physical characteristics such as low stiffness, high mechanical damping and temperature sensitivity. During direct through milling, the cutting force between the tool and the workpiece is prone to slight fluctuations, which can trigger severe regenerative chatter stress waves. At the same time, the high and uneven internal residual stress remaining at the edge after injection molding will be redistributed under the action of cutting force, resulting in defects such as edge chipping, vibration whitening and dimensional deviations, which seriously affect the light transmission performance and appearance quality of the head-up display.

[0004] Therefore, how to avoid edge chipping and vibration whitening caused by cutting force fluctuations during the milling and separation process of thin-walled polymer injection molded parts is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a sprue milling process for injection molded parts. Through a sprue milling separator comprising a fixed fixture, milling components, a multi-axis drive mechanism, a posture adjustment mechanism, and a separation mechanism, pre-weakening, stress-guided fracture, and edge finishing steps are performed. This fundamentally eliminates regenerative chatter stress waves and prevents edge chipping and vibration whitening of the product. It solves the problem of edge chipping and vibration whitening caused by cutting force fluctuations during the sprue milling separation process for thin-walled polymer injection molded parts.

[0006] To achieve the above objectives, the present invention provides a sprue milling process for injection molded parts. The injection molded parts include a product and a sprue. The sprue milling process is performed using a sprue milling separator. The sprue milling separator includes a base with a processing position, a fixed fixture on the base, a milling assembly in the processing position, a multi-axis drive mechanism rigidly connected to the base and used to drive the base to perform multi-axis spatial displacement, an attitude adjustment mechanism between the base and the fixed fixture, and a separation mechanism on one side of the base.

[0007] The sprue milling process includes the following steps: The fixing step involves clamping and fixing the product using the fixing fixture, and exposing the connection area between the product and the sprue component to the processing position. In the pre-weakening step, the multi-axis drive mechanism drives the machine base to move the injection molded part relative to the milling assembly. The rotating milling assembly mills and thins the connection area, forming a prestress concentration zone in the connection area, and retaining a residual support thin wall at the bottom of the prestress concentration zone. In the stress-guided fracture step, while keeping the product clamping state unchanged, the separation mechanism applies a separation force to the sprue component, causing the residual support thin wall to fracture along the prestress concentration zone, thereby separating the product from the sprue component and causing the sprue component to detach. In the edge finishing step, after the product is separated from the sprue, the multi-axis drive mechanism drives the machine base to move the product relative to the milling assembly, and the milling assembly is used to chamfer and finish the broken edge of the product. During the finishing process, the control cabinet receives the cutting force signal collected by the spindle force sensor, and controls the attitude adjustment mechanism to adjust the spatial relative attitude of the product driven by the fixed fixture in real time according to the cutting force signal.

[0008] The beneficial effects of this invention are as follows: By using the fixed fixture, milling assembly, multi-axis drive mechanism, attitude adjustment mechanism and separation mechanism in the sprue milling separator, the pre-weakening, stress-guided fracture and edge finishing steps are performed, thereby fundamentally eliminating regenerative flutter stress waves and avoiding edge chipping and vibration whitening of products. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the structure of a sprue milling and separating machine according to the present invention.

[0010] Figure 2 This is a schematic diagram of the structure of the fixing fixture and posture adjustment mechanism of the present invention.

[0011] Figure 3 This is a schematic diagram of the separation mechanism of the present invention.

[0012] The reference numerals in the figures include: 1. Machine base; 11. Machining station; 2. Fixture; 3. Milling assembly; 4. Multi-axis drive mechanism; 5. Attitude adjustment mechanism; 51. First mounting plate; 52. Second mounting plate; 53. Magnetorheological damping elastic element; 54. Excitation coil; 55. Flexible force-controlled direct drive driver; 6. Separation mechanism; 61. Multi-axis drive assembly; 611. Fixed gripping end; 62. Vibrator. Detailed Implementation

[0013] The present invention will now be described in detail with reference to the accompanying drawings.

[0014] like Figures 1 to 3As shown, the present invention discloses a sprue milling process for injection molded parts. The injection molded parts include a product and sprue parts. The sprue milling process is performed using a sprue milling separator. The sprue milling separator includes a base 1 with a processing position 11, a fixing fixture 2 disposed on the base 1, a milling assembly 3 disposed within the processing position 11, a multi-axis drive mechanism 4 rigidly connected to the base 1 and used to drive the base 1 to perform multi-axis spatial displacement, an attitude adjustment mechanism 5 disposed between the base 1 and the fixing fixture 2, and a separation mechanism 6 disposed on one side of the base 1. The fixing fixture 2 can be a mechanical clamping fixture or a negative pressure adsorption fixture.

[0015] By setting a base 1 with a machining position 11, a structural bearing benchmark and machining space limit are provided for the sprue milling separator, so that the fixed fixture 2, milling component 3, multi-axis drive mechanism 4, attitude adjustment mechanism 5 and separation mechanism 6 can be assembled and operated in a defined relative spatial position, thus realizing the overall structural stability of the sprue milling separator and the precise positioning of the machining area space.

[0016] By setting the fixing fixture 2 on the machine base 1, the product is clamped and fixed using the fixing fixture 2, so that the connection area between the product and the sprue part is stably exposed in the processing position 11, thus achieving fixed position of the injection molded part during processing and avoiding relative displacement.

[0017] By setting the milling component 3 within the machining station 11, the rotating milling component 3 is used to perform milling, thinning, and chamfering finishing on the connecting area, thereby achieving material removal and edge forming processing of the connecting area.

[0018] The multi-axis drive mechanism 4 is rigidly connected to the base 1 and drives the base 1 to perform multi-axis spatial displacement, so that the fixed fixture 2 fixed on the base 1 drives the injection molded part to produce controllable relative movement with respect to the milling assembly 3, thereby realizing precise control of the milling thinning trajectory and edge finishing trajectory of the connecting area.

[0019] By setting the attitude adjustment mechanism 5 between the machine base 1 and the fixed fixture 2, the attitude adjustment mechanism 5 can adjust the spatial relative attitude of the product driven by the fixed fixture 2 in real time during the edge finishing process, thereby realizing the dynamic adaptation of the product spatial attitude to the cutting state of the milling component 3.

[0020] By setting the separation mechanism 6 on one side of the base 1, the separation mechanism 6 can apply a separation force to the nozzle after pre-weakening, thereby achieving the fracture of the residual support thin wall along the prestress concentration zone and the separation of the product from the nozzle.

[0021] The sprue milling process includes the following steps: In the fixing step, the product is clamped and fixed by the fixing fixture 2, and the connection area between the product and the sprue is exposed at the processing position 11. The product is clamped and fixed by the fixing fixture 2, and the connection area between the product and the sprue is exposed in the processing position 11, so that the connection area is within the processing range of the milling component 3, thus achieving stable positioning of the injection molded part and full exposure of the processing area.

[0022] In the pre-weakening step, the multi-axis drive mechanism 4 drives the base 1 to move the injection molded part relative to the milling assembly 3. The rotating milling assembly 3 mills and thins the connection area, forming a prestress concentration zone in the connection area, and retaining residual support thin wall at the bottom of the prestress concentration zone. The multi-axis drive mechanism 4 drives the base 1 to move the injection molded part relative to the milling assembly 3. The rotating milling assembly 3 mills and thins the connection area to form a prestress concentration zone and retains a residual support thin wall at the bottom of the prestress concentration zone. The geometric stress concentration effect of the prestress concentration zone is used to predefine the fracture path to the connection area. At the same time, the residual support thin wall is used to maintain the structural connection between the product and the sprue before separation. This achieves controllable fracture path and avoids regenerative chatter stress waves caused by direct through milling.

[0023] In the stress-guided fracture step, while keeping the product clamping state unchanged, the separation mechanism 6 applies a separation force to the sprue component, causing the residual support thin wall to fracture along the prestress concentration zone, thereby separating the product from the sprue component and causing the sprue component to fall off. Under the premise that the product's clamping state remains unchanged, the separation mechanism 6 applies a separation force to the sprue component, causing the residual support thin wall to fracture along the prestress concentration zone, thereby separating the product from the sprue component and causing the sprue component to fall off. The geometric stress concentration effect of the prestress concentration zone reduces the external force required for fracture, and the separation force of the separation mechanism 6 replaces the continuous cutting force of the milling component 3 to complete the cutting. This fundamentally eliminates the excitation source of regenerative chatter stress waves and avoids edge chipping and vibration whitening of the product.

[0024] In the edge finishing step, after the product is separated from the sprue, the multi-axis drive mechanism 4 drives the base 1 to move the product relative to the milling assembly 3. The milling assembly 3 is used to chamfer and finish the edge of the product after it breaks. During the finishing process, the control cabinet receives the cutting force signal collected by the spindle force sensor and controls the attitude adjustment mechanism 5 to adjust the spatial relative attitude of the product driven by the fixed fixture 2 in real time according to the cutting force signal.

[0025] After the product is separated from the sprue, the multi-axis drive mechanism 4 drives the machine base 1 to move the product relative to the milling assembly 3. The milling assembly 3 is used to chamfer and finish the broken edges of the product. During the finishing process, the control cabinet receives the cutting force signal collected by the spindle force sensor. Based on the cutting force signal, the attitude adjustment mechanism 5 is controlled to adjust the spatial relative attitude of the product driven by the fixed fixture 2 in real time. The real-time feedback of the cutting force signal forms a force control closed loop, which enables the attitude adjustment mechanism 5 to dynamically compensate for the impact of cutting force fluctuations on the product. This achieves stable and controllable cutting force during the finishing process and avoids secondary chipping and dimensional deviations at the product edges.

[0026] During operation, the base 1 of the sprue milling and separating machine supports the fixing fixture 2, milling assembly 3, multi-axis drive mechanism 4, attitude adjustment mechanism 5, and separation mechanism 6. The fixing fixture 2 clamps and fixes the product, exposing the connection area between the product and the sprue part to the processing position 11. The multi-axis drive mechanism 4 drives the base 1 to move the injection molded part relative to the milling assembly 3. The rotating milling assembly 3 mills and thins the connection area to form a prestress concentration zone, leaving a residual support thin wall at the bottom of the prestress concentration zone. The separation mechanism 6 applies a separation force to the sprue part, causing the residual support thin wall to break along the prestress concentration zone, thus separating the product from the sprue part. The multi-axis drive mechanism 4 drives the base 1 to move the product relative to the milling assembly 3. The milling assembly 3 performs chamfering and finishing on the broken edges of the product. The control cabinet receives the cutting force signal collected by the spindle force sensor and controls the attitude adjustment mechanism 5 to adjust the spatial relative attitude of the product driven by the fixing fixture 2 in real time based on the cutting force signal.

[0027] like Figure 2 As shown, the sprue milling separator of this embodiment also includes a photoelastic polarization imaging detection system and a spindle three-dimensional force sensor integrated at the end of the milling assembly 3; By adding a photoelastic polarization imaging detection system to the sprue milling separator, online detection and characterization of the residual stress distribution within the connecting area were achieved. Furthermore, by adding a three-dimensional spindle force sensor integrated into the end of milling assembly 3 to the sprue milling separator, accurate three-dimensional acquisition of the cutting force vector was realized.

[0028] The attitude adjustment mechanism 5 is a force-controlled attitude adjustment mechanism 5, which includes: The first mounting plate 51 is used to support the fixing fixture 2; The second mounting plate 52 is fixed on the base 1; Magnetorheological damping elastic element 53 is arrayed between the first mounting plate 51 and the second mounting plate 52; Excitation coil 54 is disposed around magnetorheological damping elastic element 53; The flexible force-controlled direct drive driver 55 is fixed on the second mounting plate 52 and is used to drive the first mounting plate 51 to deflect in order to change the spatial relative posture of the product on the fixed fixture 2. The control cabinet includes a microprocessor, a memory, and a mechanical calculation module, which is used to change the current of the input excitation coil 54 to adjust the damping ratio and stiffness of the magnetorheological damping elastic element 53. During the edge finishing process, the control cabinet performs the following linkage control: The first mounting plate 51 is driven to deflect in the spatial rotational degree of freedom by the flexible force-controlled direct drive driver 55, so as to finely adjust the spatial relative posture of the product on the fixed fixture 2 in real time. Meanwhile, based on the time-domain fluctuation characteristics of the cutting force signal collected by the spindle three-dimensional force sensor, the current of the input excitation coil 54 is dynamically changed to adjust the damping ratio and stiffness of the magnetorheological damping elastic element 53 in real time. The attitude deflection of the flexible force-controlled direct drive driver 55 and the damping adjustment of the magnetorheological damping elastic element 53 are controlled by the control cabinet in coordination with the cutting force signal to form a force-position coupling closed loop. The magnetorheological damping elastic element 53 is in a first stiffness and first damping state when the excitation coil 54 is not energized or when the foundation maintenance current is applied. When a set saturation current is applied, a rheological phase change occurs and it switches to a second stiffness and second damping state where both stiffness and damping increase.

[0029] In practical industrial applications, the photoelastic polarization imaging detection system of this invention can preferably use a commercially available full-field polarization stress analyzer (such as the LSM-9100 series from LUCEO Corporation of Japan or the SVA-2000 series from Strainoptics Corporation of the United States). Through a standard polarization and analysis optical architecture, full-field digital high-resolution imaging of the edge of the injection-molded part for the vehicle head-up display within processing position 11 is performed. Those skilled in the art can directly utilize the API interface of this conventional product to stream the output two-dimensional birefringence phase difference parameter matrix to the memory of the control cabinet (6) in real time, using it as the dynamic constraint boundary condition for the mechanical calculation engine program, without any inventive effort. In other parallel embodiments, an ultrasonic acoustoelastic detection device, a micro-focal X-ray diffractometer, or a Raman spectroscopy frequency shift analyzer can also be used as alternatives, which can also achieve digital quantization output of the stress field within the edge of the injection-molded part, and are within the protection scope of this invention.

[0030] The milling assembly 3 of this invention includes a spindle and a slide servo motor that drives the spindle to lift. The three-dimensional force sensor of the spindle is preferably a piezoelectric quartz multi-axis sensor. However, without departing from the core concept of this invention, the physical force sensor can also be removed, and a current state observer of the spindle and slide servo motor of the milling assembly 3 built in the control cabinet can be used instead. By collecting the operating current and electromagnetic torque of the slide servo motor in real time, the equivalent instantaneous cutting force vector can be calculated in reverse. This is an equivalent substitution that can be achieved by those skilled in the art without creative effort.

[0031] In practical commercial applications, the magnetorheological damping elastic element 53 of this invention can preferably be a commercially available industrial-grade linear magnetorheological damper (e.g., the RD-8040-1 or RD-8041-1 series monotube magnetorheological damper from LORD Corporation). The industrial-grade linear magnetorheological damper is filled with a magnetorheological fluid with high saturation magnetization, and is connected to the rheological current output terminal of the control cabinet via an excitation coil 54 wound inside or around it. However, those skilled in the art should understand that the magnetorheological damping elastic element 53 is not limited to a liquid damper architecture. In other parallel preferred embodiments, to prevent liquid leakage and improve the intrinsic elasticity of the structure, the magnetorheological damping elastic element 53 can also employ a magnetorheological elastomer (MRE) smart composite support. The intelligent composite support is assembled by alternating and shearing layers of anisotropic magnetorheological solid rubber blocks and high-permeability silicon steel sheets. In the unenergized state, it relies on the viscoelasticity of the polymer matrix to provide the first stiffness and first damping state. Upon receiving a set saturation current value input from the control cabinet, the internal microparticles instantaneously recombine along magnetic lines of force due to magnetic polarization, thereby macroscopically forcing a sudden increase in its shear stiffness and damping coefficient, transiently switching to a second stiffness and second damping state. Furthermore, those skilled in the art can use magnetorheological extrusion film limiters, electromagnetic damping actuators, or electrorheological (ER) adaptive vibration damping sandwich layers as equivalent hardware replacements. All of these can achieve selective hardening vibration control in anisotropic directions under the same sequential current drive, and all fall within the equivalent protection scope of this invention.

[0032] The flexible force-controlled direct drive actuator 55 of the present invention can be used, but is not limited to, an integrated intelligent voice coil motor actuator (such as the LAL series or CBL series intelligent axial electric cylinders from SMAC Corporation of the United States, or the AVM series voice coil direct drive actuators from Akribis Corporation of Singapore). The flexible force-controlled direct drive actuator 55 integrates a coreless voice coil direct drive coil, a high-resolution grating displacement feedback element, and a precision digital force sensor. Through a built-in current-torque linear mapping control loop, it can generate a micro-amplitude multidimensional deflection torque with millisecond-level response under the drive of the target attitude control current sent from the control cabinet. However, those skilled in the art should understand that the flexible force-controlled direct drive actuator 55 is not limited to the aforementioned integrated voice coil actuator. In other parallel equivalent embodiments, a split architecture can also be adopted, such as a force control closed-loop system constructed by rigidly cascading a coreless industrial linear motor (or a direct-drive torque motor) and a high-frequency multi-axis voltage / torque sensor (such as the Mini series six-dimensional force sensor from ATI, USA); or an active floating actuator (such as the ACF series active force control actuator from FerRobotics, Austria).

[0033] The microprocessor integrated inside the control cabinet of this invention can be, but is not limited to, a high-performance industrial-grade digital signal processor (e.g., Texas Instruments' TMS320F2837xD chip or an STM32H743 microcontroller based on the ARM Cortex-M7 core). The memory includes high-speed static random access memory (SRAM) that is rigidly connected to the microprocessor via a high-speed bus and serial peripheral interface flash memory (SPI NOR Flash). The mechanical solution program / module embedded in memory can preferably be a matrix iterative solver built on the ARM-CMSIS-DSP standard library, or a hardware-level dynamic parallel acceleration hardware module embedded in a programmable logic chip (such as the FPGA logic layer of the Xilinx Zynq-7000 series SoC chip).

[0034] By specifically configuring the attitude adjustment mechanism 5 as a force-controlled attitude adjustment mechanism 5, and making the force-controlled attitude adjustment mechanism 5 include a first mounting plate 51, a second mounting plate 52, a magnetorheological damping elastic element 53, an excitation coil 54, a flexible force-controlled direct drive driver 55, and a control cabinet, the first mounting plate 51 carries the fixed fixture 2, the second mounting plate 52 is fixed to the base 1, the magnetorheological damping elastic element 53 is arrayed between the first mounting plate 51 and the second mounting plate 52, the excitation coil 54 is arranged around the magnetorheological damping elastic element 53, and the flexible force-controlled direct drive driver 55 is fixed on the second mounting plate 52 and drives the first mounting plate 51 to deflect, the active drive and passive damping coordinated adjustment of the spatial attitude of the fixed fixture 2 is realized.

[0035] By incorporating a microprocessor, memory, and mechanical calculation module into the control cabinet, integrated computation of cutting force signal processing, mechanical calculation, and control command generation is achieved.

[0036] By changing the current of the input excitation coil 54 in the control cabinet to adjust the damping ratio and stiffness of the magnetorheological damping elastic element 53, the damping and stiffness characteristics of the magnetorheological damping elastic element 53 are electrically adjustable.

[0037] In the edge finishing step, the flexible force-controlled direct drive driver 55 is controlled by the control cabinet to drive the first mounting plate 51 to deflect in the spatial rotational degree of freedom, so as to finely adjust the spatial relative posture of the product on the fixed fixture 2 in real time, thereby realizing the active and fine adjustment of the product's spatial posture.

[0038] Meanwhile, the control cabinet dynamically changes the current of the input excitation coil 54 according to the time-domain fluctuation characteristics of the cutting force signal collected by the spindle three-dimensional force sensor, thereby adjusting the damping ratio and stiffness of the magnetorheological damping elastic element 53 in real time, realizing the real-time adaptive adjustment of system damping and stiffness according to the cutting force fluctuation.

[0039] By having the attitude deflection of the flexible force-controlled direct drive driver 55 and the damping adjustment of the magnetorheological damping elastic element 53 be coordinated and controlled by the control cabinet according to the cutting force signal to form a force-position coupling closed loop, the time-domain coordination of attitude adjustment and damping vibration suppression is realized, and the abnormal fluctuation of cutting force during the finishing process is avoided, which leads to secondary damage to the product edge.

[0040] By placing the magnetorheological damping elastic element 53 in a first stiffness and first damping state when the excitation coil 54 is not energized or when a base sustaining current is applied, and then switching it to a second stiffness and second damping state with increased stiffness and damping when a set saturation current is applied, the magnetorheological damping elastic element 53 can switch between a low-damping compliant attitude adjustment state and a high-damping rigid vibration suppression state.

[0041] Upgrading the single attitude adjustment function to a force-controlled attitude adjustment function with force-position coupling closed loop enables attitude adjustment and damping vibration suppression to work synergistically during edge finishing, significantly improving the anti-chatter capability and dimensional accuracy stability of polymer thin-walled injection molded parts during finishing.

[0042] In the edge finishing step of this embodiment, when the spindle three-dimensional force sensor detects that the fluctuation rate of the cutting force signal exceeds a preset safety threshold, the control cabinet performs spatial relative attitude adjustment and adaptive transient hardening locking. The calculation and driving of the spatial attitude compensation vector includes the following steps: The microprocessor performs real-time subtraction calculation between the instantaneous cutting force vector acquired online by the spindle three-dimensional force sensor and the preset target ductile cutting force vector in the memory to construct a three-dimensional mechanical deviation matrix; The microprocessor calls the physical augmented neural network mechanical calculation program in the memory, and combines it with the internal residual stress birefringence phase distribution parameters of the injection molded part that are pre-acquired and stored in the memory to perform online inverse demapping of the three-dimensional mechanical deviation matrix in order to calculate the angular displacement compensation amount required by the first mounting plate 51 in the spatial rotational degree of freedom, and reconstruct the spatial attitude compensation vector based on the angular displacement compensation amount. The control cabinet generates attitude control current based on the spatial attitude compensation vector and outputs the attitude control current to the flexible force control direct drive driver 55 to drive the first mounting plate 51 to perform multi-dimensional micro-amplitude deflection, thereby realizing real-time compensation and fine adjustment of the spatial relative attitude of the product carried on the fixed fixture 2.

[0043] By setting a trigger condition in the edge finishing step that the control cabinet performs spatial relative attitude adjustment and adaptive transient hardening lock when the spindle three-dimensional force sensor detects that the fluctuation rate of the cutting force signal exceeds a preset safety threshold, active compensation and hardening lock are activated only when the cutting force fluctuates abnormally, thus avoiding continuous high-frequency response of the system.

[0044] By enabling the microprocessor to perform real-time subtraction calculation between the instantaneous cutting force vector acquired online by the spindle three-dimensional force sensor and the preset target ductile cutting force vector in the memory to construct a three-dimensional mechanical deviation matrix, a three-dimensional quantitative characterization of the cutting force deviation is realized.

[0045] By having the microprocessor call the physical augmented neural network mechanical solution program in memory, and combining it with the birefringence phase distribution parameters of the internal residual stress of the injection molded part that are pre-acquired and stored in memory, the three-dimensional mechanical deviation matrix is ​​inversely mapped online to calculate the angular displacement compensation amount required by the first mounting plate 51 in the spatial rotational degree of freedom. This realizes intelligent mechanical inverse solution and accurate compensation amount calculation that takes into account the internal residual stress distribution of the material.

[0046] By having the control cabinet generate an attitude control current based on the spatial attitude compensation vector and output the attitude control current to the flexible force-controlled direct drive driver 55, thereby driving the first mounting plate 51 to perform multi-dimensional micro-amplitude deflection, real-time compensation and fine-tuning of the spatial relative attitude of the product carried on the fixed fixture 2 is achieved, and edge chipping of the product caused by excessive cutting force is suppressed.

[0047] Based on the force-position coupling closed loop, an intelligent mechanical inverse solution and over-limit triggering compensation mechanism based on physical reinforcement neural network is introduced, so that the attitude compensation not only responds to the instantaneous cutting force fluctuation, but also comprehensively considers the internal residual stress distribution of the injection molded part, which significantly improves the accuracy and pertinence of attitude compensation.

[0048] In this embodiment, when the control cabinet drives the first mounting plate 51 to deflect according to the spatial attitude compensation vector and implements adaptive transient hardening lock on the first mounting plate 51, the following cooperative control timing is satisfied in the time domain: During the T0 to T1 time domain, the magnetorheological damping elastic element 53 maintains a first stiffness and a first damping state under the basic sustaining current of the excitation coil 54. The control cabinet controls the magnetorheological current of the excitation coil 54 to monotonically increase from the basic sustaining current to the set saturation current value. During the increase of the magnetorheological current, the control cabinet maintains the drive current of the input flexible force-controlled direct drive driver 55 constant so that the flexible force-controlled direct drive driver 55 maintains the current mechanical output posture position. At time T1 in the time domain, when the rheological current reaches the set saturation current value, the excitation coil 54 excites the target magnetic field, causing the magnetorheological damping elastic element 53 to undergo a rheological phase transition, so that the magnetorheological damping elastic element 53 switches from the first stiffness and the first damping state to the second stiffness and the second damping state. During the T1 to T2 phase in the time domain, when the magnetorheological damping elastic element 53 is in the second stiffness and second damping state, the control cabinet releases the current maintenance state of the flexible force-controlled direct drive driver 55 and outputs the attitude adjustment drive current to drive the first mounting plate 51 to deflect under the rigid vibration suppression constraint provided by the second stiffness and second damping state. The time interval between the moment T0 when the rheological current begins to monotonically increase and the moment T1 when the first mounting plate 51 actually begins to deflect is defined as the micro-phase transition delay window, and the duration of the micro-phase transition delay window is controlled between 1.5 milliseconds and 3 milliseconds, and the duration matches the rheological response time constant of the magnetorheological damping elastic element 53.

[0049] By setting the control cabinet to follow the timing sequence of first increasing the rheological current and maintaining the constant drive current of the flexible force-controlled direct drive driver 55 in the T0 to T1 stage when implementing adaptive transient hardening lock on the first mounting plate 51, the flexible force-controlled direct drive driver 55 can maintain the current mechanical output posture position unchanged during the phase transition of the magnetorheological damping elastic element 53, thereby achieving stable maintenance of the posture position during the phase transition and avoiding the introduction of additional position disturbances during the phase transition process.

[0050] By exciting the target magnetic field through the excitation coil 54 at time T1, the magnetorheological damping elastic element 53 undergoes a rheological phase transition and switches to the second stiffness and second damping state, thus realizing the deterministic switching of the magnetorheological damping elastic element 53 from a low-damping compliant state to a high-damping rigid state.

[0051] By releasing the current maintenance state of the flexible force-controlled direct drive driver 55 and outputting the attitude adjustment drive current in the T1 to T2 stage, the first mounting plate 51 is driven to deflect under the rigid vibration suppression constraint provided by the second stiffness and second damping state. This enables the attitude fine adjustment to be performed under the hardened constraint environment, and makes the attitude adjustment process have both motion compliance and vibration suppression capabilities.

[0052] By controlling the duration of the micro-phase transition delay window between the moment T0 when the rheological current begins to monotonically increase and the moment T1 when the first mounting plate 51 actually begins to deflect to between 1.5 milliseconds and 3 milliseconds, and matching the duration with the rheological response time constant of the magnetorheological damping elastic element 53, the magnetorheological damping elastic element 53 is able to fully complete the rheological phase transition before starting the attitude drive, thus avoiding stiffness abrupt changes and attitude overshoot caused by incomplete phase transition.

[0053] Based on intelligent compensation calculation, by introducing a microscopic phase transition delay window and a phased collaborative control timing, the contradiction between the rheological response delay of magnetorheological materials and the immediacy of attitude driving is resolved, enabling the hardening lock and attitude deflection to be precisely connected in the time domain, which significantly improves the reliability and control accuracy of adaptive transient hardening lock.

[0054] In this embodiment, during the deflection of the first mounting plate 51 under the hardening constraint of the second stiffness and second damping state, the adaptive transient hardening locking direction-selective hardening includes the following steps: The control cabinet calculates the dominant normal direction of the cutting chatter online based on the cutting force signal collected by the spindle three-dimensional force sensor; According to the dominant normal direction, the control cabinet groups the excitation coils 54 distributed in the array according to the vertical distance between each excitation coil 54 and the dominant normal direction, and outputs different independent phase change current values ​​independently and asymmetrically for the excitation coils 54 in different groups. The independent phase change current values ​​received by the excitation coils 54 in each group decrease in a gradient along the direction away from the dominant normal direction. Each magnetorheological damping elastic element 53 generates differentiated rheology under the local magnetic field excited by asymmetric current, so as to improve the translational degree of freedom of the first mounting plate 51 in the direction parallel to the rotation axis of the milling assembly 3, and the spatial motion resistance in the two rotational degrees of freedom perpendicular to the rotation axis, so that the shear stiffness of each corresponding magnetorheological damping elastic element 53 in the flutter direction corresponding to the translational degree of freedom and the two rotational degrees of freedom is hardened and increased to the second stiffness. At the same time, the control cabinet locks the target deflection direction of the flexible force-controlled direct drive driver 55 currently performing spatial attitude compensation, and maintains a low shear resistance state by controlling the corresponding magnetorheological damping elastic element 53 in the target deflection direction, so as to maintain the motion compliance of the first mounting plate 51 in the target deflection direction.

[0055] By enabling the control cabinet to calculate the dominant normal direction of cutting chatter online based on the cutting force signal collected by the spindle three-dimensional force sensor, real-time identification and directional suppression of the main excitation direction of cutting chatter are achieved.

[0056] By having the control cabinet group the array of excitation coils 54 according to the vertical distance between each excitation coil 54 and the normal dominant direction, and independently and asymmetrically output different independent phase change current values ​​for the excitation coils 54 in different groups, and make the independent phase change current values ​​decrease in a gradient along the direction away from the normal dominant direction, the asymmetrical distribution and gradient control of the magnetic field strength in the flutter dominant direction are realized.

[0057] By causing the various magnetorheological damping elastic elements 53 to generate differentiated rheology under the local magnetic field excited by asymmetric current, the spatial motion resistance of the first mounting plate 51 in the direction of translational freedom parallel to the rotation axis of the milling assembly 3 and in the two rotational freedoms about the rotation axis perpendicular to the milling assembly 3 is improved. The shear stiffness of the corresponding magnetorheological damping elastic elements 53 in the translational freedom and the two rotational freedoms corresponding to the flutter direction is hardened to the second stiffness, thereby achieving targeted stiffness enhancement in the flutter-dominant direction and maintaining moderate compliance in the non-flutter direction.

[0058] By locking the control cabinet to the target deflection direction of the flexible force-controlled direct drive driver 55 currently performing spatial attitude compensation, and by controlling the corresponding magnetorheological damping elastic element 53 in the target deflection direction to maintain a low shear resistance state to maintain the motion compliance of the first mounting plate 51 in the target deflection direction, the decoupling of the attitude compensation drive direction and the stiffness hardening direction is achieved, and the hardening constraint is avoided from hindering the necessary attitude adjustment.

[0059] Based on the time-series collaborative control, a direction-selective hardening mechanism based on the dominant identification of the cutting chatter method is further introduced, which enables the stiffness distribution of the magnetorheological damping elastic element 53 to be asymmetrically adaptively configured according to the real-time chatter direction, maximizing the vibration suppression efficiency while retaining the motion freedom required for attitude compensation.

[0060] In this embodiment, the prestress concentration zone formed in the pre-weakening step is composed of multiple blind holes cut along the connection area and a continuous linear weakening groove. The multiple blind holes are arranged at intervals along the extension direction of the connection area, and the continuous linear weakening groove extends continuously along the extension direction and penetrates the area between adjacent blind holes. The prestress concentration strip is only formed on one side of the connection area surface; The continuous linear weakening groove is an asymmetric V-shaped pre-cut groove. The groove angle of the asymmetric V-shaped pre-cut groove facing the product side is larger than the groove angle facing the sprue side, so that the fracture crack at the prestress concentration zone is driven by the asymmetric stress field to deflect and extend towards the sprue side, inhibiting the extension of the crack towards the product side.

[0061] By combining multiple blind holes and continuous linear weakening grooves cut along the connection area to form the prestress concentration zone in the pre-weakening step, and by arranging the multiple blind holes at intervals along the extension direction of the connection area and the continuous linear weakening grooves extending continuously along the extension direction and penetrating the area between adjacent blind holes, the combined structure of blind holes and continuous linear weakening grooves creates a superposition effect of multiple stress concentrations in the connection area, thereby improving the stress concentration coefficient of the prestress concentration zone and precisely defining the fracture path.

[0062] By creating the prestress concentration band only on one side of the connection area, the excessive weakening of the product's structural strength due to double-sided slotting in the connection area is avoided. This ensures the effectiveness of single-sided stress concentration while maintaining the structural stability of the product before separation from the sprue.

[0063] By transforming the continuous linear weakening groove into an asymmetric V-shaped pre-cut groove, and making the groove angle of the asymmetric V-shaped pre-cut groove facing the product side larger than the groove angle facing the sprue side, the fracture crack is driven to deflect and propagate towards the sprue side using an asymmetric stress field, thereby suppressing the extension of the crack towards the product side and protecting the integrity of the product edge.

[0064] Preferably, the equivalent stress concentration factor of the prestressed concentration zone is determined by weighted superposition of the stress concentration factor of the blind hole and the stress concentration factor of the V-shaped pre-cut groove through dynamic evolution coefficient; The mechanical calculation module adjusts the dynamic evolution coefficient within the range of 0.3 to 0.6 based on the real-time machining deformation rate and tool wear status. In the initial stage of machining, the dynamic evolution coefficient is set within the range of 0.5 to 0.6 to increase the weight of the stress concentration factor of the blind hole. As tool wear increases, the dynamic evolution coefficient gradually decreases to the range of 0.3 to 0.4 to increase the weight of the stress concentration factor of the V-groove. Equivalent stress concentration factor The evolution equation is:

[0065] in, For dynamic evolution coefficients; Blind hole stress concentration factor The expression is:

[0066] Where d is the diameter of the blind hole, and W is the connection width. For correction functions, The triaxiality factor for stress concentration on a three-dimensional arc surface; The controller uses the equivalent stress concentration factor obtained from the solution. The multi-axis drive mechanism 4 is controlled to operate, thereby controlling the machining thickness of the residual support thin wall.

[0067] By weighting the equivalent stress concentration factor of the prestressed concentration zone by the stress concentration factor of the blind hole and the stress concentration factor of the V-shaped pre-cut groove through a dynamic evolution coefficient, and by adjusting the dynamic evolution coefficient within the range of 0.3 to 0.6 according to the real-time machining deformation rate and tool wear state, the dynamic adaptive calculation of the equivalent stress concentration factor of the prestressed concentration zone is realized.

[0068] By setting the dynamic evolution coefficient within the range of 0.5 to 0.6 during the initial stage of machining to increase the weight of the stress concentration coefficient in blind holes, and gradually reducing the dynamic evolution coefficient to the range of 0.3 to 0.4 as tool wear increases to increase the weight of the stress concentration coefficient in V-grooves, the weight of stress concentration contribution is dynamically optimized according to the machining stage and tool condition, thus maintaining fracture controllability.

[0069] By controlling the action of the multi-axis drive mechanism 4 according to the calculated equivalent stress concentration coefficient, the processing thickness of the residual support thin wall is controlled, thus achieving closed-loop matching between the thickness of the residual support thin wall and the equivalent stress concentration coefficient, and avoiding the residual support thin wall being too thick or too thin.

[0070] Based on the pre-weakening step, by introducing a prestress concentration zone structure combining blind holes and asymmetric V-shaped pre-cut grooves, and with the dynamic evolution calculation of the equivalent stress concentration coefficient and closed-loop control of the residual thin wall thickness, the precise guidance capability of the fracture path is upgraded from static geometric guidance to dynamic process parameter adaptive guidance, which significantly improves the process robustness to different processing stages and tool wear states.

[0071] like Figure 3 As shown, the separation mechanism 6 in this embodiment includes a multi-axis drive assembly 61 and a vibrator 63. The end of the multi-axis drive assembly 61 is provided with a fixed gripping end 62. In the stress-guided fracture step, the separation force is a pulse resonance separation force. The application process of the pulse resonance separation force includes: The multi-axis drive assembly 61 drives the fixed gripping end 62 to apply static prestress to the sprue part. During the maintenance of the static prestress, the vibrator 63 synchronously injects alternating energy into the injection molded part. The frequency of the alternating energy is equal to the current first-order natural frequency of the injection molded part under the action of static prestress. The static prestress and the alternating energy are superimposed in the time domain to form a pulse resonance separation force. The pulse resonance separation force can be applied in one or a combination of the following ways: In the torsion form, the fixed gripping end 62 is driven by the multi-axis drive assembly 61 to rotate around the central axis of the connection area to apply a static torque, while the exciter 63 injects a shear stress wave along the tangential direction around the central axis, which superimposes to form a pulse torsion torque, the pulse torsion torque being 0.5 N·m to 2 N·m; In the bending form, the fixed gripping end 62 is driven by the multi-axis drive assembly 61 to move along the normal direction perpendicular to the product surface to apply a static bending force. At the same time, the vibrator 63 injects bending stress waves along the thickness normal direction of the connection area, which are superimposed to form a pulse bending force. The pulse bending force is 5N to 20N. In the tensile breaking mode, the fixed gripping end 62 is driven by the multi-axis drive assembly 61 to move in a horizontal tangential direction away from the product to apply a static tensile force. At the same time, the vibrator 63 injects tensile-compression type ultrasonic longitudinal waves in a horizontal tangential direction, which are superimposed to form a pulse tensile breaking force, which is 10N to 50N.

[0072] The exciter 63 can be a mechanical piezoelectric exciter 63, a non-contact electromagnetic induction pulse exciter 63, or a high-energy focused acoustic shockwave generator.

[0073] By including a multi-axis drive assembly 61 and an exciter 63 in the separation mechanism 6 and setting a fixed gripping end 62 at the end of the multi-axis drive assembly 61, an integrated separation action execution of static prestress application and dynamic alternating energy injection is realized.

[0074] By setting the separation force in the stress-guided fracture step as a pulse resonance separation force, and driving the fixed gripping end 62 to apply static prestress to the sprue component by the multi-axis drive assembly 61, and simultaneously injecting alternating energy equal to the current first-order natural frequency of the injection molded part under the action of static prestress into the injection molded part by the exciter 63 during the maintenance of static prestress, the static prestress and alternating energy are superimposed in the time domain to form a pulse resonance separation force. By utilizing the resonance effect to generate stress amplification at the residual support thin wall, it is possible to achieve efficient fracture of the residual support thin wall induced by a lower static prestress and avoid excessive separation force directly impacting the product body and causing edge chipping.

[0075] By providing three pulse resonance separation force application methods—torsion, bending, and tension—the multi-axis drive assembly 61 and the exciter 63 can select static torque and shear stress wave superposition, static bending force and bending stress wave superposition, or static tensile force and tension-compression type ultrasonic longitudinal wave superposition, according to the geometric characteristics and material properties of the connection area. This achieves flexible adaptation and multiple modes of separation force application.

[0076] Example of a broken form: This embodiment provides an example of applying a torsional pulse resonance separation force in the sprue milling process of injection molded parts.

[0077] The injection-molded part is the head-up display (HUD) front windshield housing, which is injection molded from polycarbonate material. The average wall thickness of the HUD front windshield housing is 2.0 mm. The product is the transparent viewing window area of ​​the HUD front windshield housing, and the sprue is the annular gate remnant at the edge of the HUD front windshield housing. The connection area between the product and the sprue is an annular connecting strip surrounding the outer edge of the product, with a connection width of 3.0 mm and a connection thickness of 2.0 mm.

[0078] In the pre-weakening step, the multi-axis drive mechanism 4 drives the base 1 to move the injection molded part relative to the milling assembly 3. The rotating milling assembly 3 cuts blind holes at intervals on the outer surface of the connecting area along the extension direction of the connecting area. The diameter of the blind holes is 0.8 mm, and the spatial distance between adjacent blind holes is 2.5 mm. At the same time, the rotating milling assembly 3 cuts continuous linear weakening grooves between adjacent blind holes. The continuous linear weakening grooves are asymmetrical V-shaped pre-cut grooves. The groove angle of the asymmetrical V-shaped pre-cut groove facing the product side is 120 degrees, and the groove angle of the asymmetrical V-shaped pre-cut groove facing the sprue side is 60 degrees. The groove depth of the asymmetrical V-shaped pre-cut groove is 0.6 mm. The prestress concentration zone is composed of blind holes and continuous linear weakening grooves, and a residual support thin wall with a thickness of 0.15 mm is retained at the bottom of the prestress concentration zone.

[0079] In the stress-guided fracture step, the separation mechanism 6 includes a multi-axis drive assembly 61 and a vibrator 63. The end of the multi-axis drive assembly 61 is provided with a fixed gripping end 62, which is a pneumatic clamping end. The multi-axis drive assembly 61 drives the fixed gripping end 62 to move to the sprue and clamp and fix the sprue. Subsequently, the multi-axis drive assembly 61 drives the fixed gripping end 62 to rotate about the central axis of the connection area to apply a static torque of 0.8 N·m.

[0080] During the maintenance of the static torque, the phase-locked loop (PLL) frequency tracking circuit in the control cabinet initiates frequency tracking. The phase comparator of the PLL frequency tracking circuit compares the phase of the vibration response signal collected by the accelerometer mounted on the fixed fixture 2 with the output phase of the voltage-controlled oscillator (VCO) of the PLL frequency tracking circuit, and controls the output frequency of the VCO based on the phase difference signal. Before the static torque is applied, the first natural frequency of the injection molded part is 120 Hz; under the prestress maintenance state of a static torque of 0.8 N·m, the overall structural stiffness of the injection molded part decreases, and the first natural frequency of the injection molded part shifts to 118 Hz. The output frequency of the VCO is locked at 118 Hz after real-time adjustment by the PLL frequency tracking circuit. The exciter 63 is a piezoelectric ceramic exciter 63, which synchronously injects a shear stress wave with a frequency of 118 Hz into the injection molded part, and the amplitude of the shear stress wave corresponds to the alternating energy input.

[0081] The static torque and alternating energy superimpose in the time domain to form a pulsed breaking torque of 0.8 N·m. Under the continuous application of the pulsed breaking torque, the residual support thin wall, under the combined effect of stress concentration and resonance amplification at the prestress concentration zone, undergoes controlled fracture along the prestress concentration zone within 0.3 seconds, achieving separation of the product from the sprue and causing the sprue to detach. After fracture, the fixed gripping end 62 releases the sprue, and there are no chipped edges or vibration whitening marks at the connection point after separation of the product and the sprue.

[0082] Example of a bent form: This embodiment provides an example of applying a bending-type pulse resonance separation force in the sprue milling process of injection molded parts.

[0083] The injection-molded part is a head-up display (HUD) reflector bracket, which is injection molded from polymethyl methacrylate (PMMA) material. The average wall thickness of the HUD reflector bracket is 1.5 mm. The product is the lens support frame of the HUD reflector bracket, and the sprue is the rectangular gate remnant on the side of the HUD reflector bracket. The connection area between the product and the sprue is a rectangular planar connecting strip with a connection width of 2.5 mm and a connection thickness of 1.5 mm.

[0084] In the pre-weakening step, the multi-axis drive mechanism 4 drives the base 1 to move the injection molded part relative to the milling assembly 3. The rotating milling assembly 3 cuts blind holes at intervals on the outer surface of the connecting area along the extension direction of the connecting area. The diameter of the blind holes is 0.6 mm, and the spatial distance between adjacent blind holes is 2.0 mm. At the same time, the rotating milling assembly 3 cuts continuous linear weakening grooves between adjacent blind holes. The continuous linear weakening grooves are asymmetrical V-shaped pre-cut grooves. The groove angle of the asymmetrical V-shaped pre-cut groove facing the product side is 110 degrees, and the groove angle of the asymmetrical V-shaped pre-cut groove facing the sprue side is 55 degrees. The groove depth of the asymmetrical V-shaped pre-cut groove is 0.5 mm. The prestress concentration zone is composed of blind holes and continuous linear weakening grooves, and a residual support thin wall with a thickness of 0.12 mm is retained at the bottom of the prestress concentration zone.

[0085] In the stress-guided fracture step, the separation mechanism 6 includes a multi-axis drive assembly 61 and a vibrator 63. The multi-axis drive assembly 61 has a fixed gripping end 62 at its end, which is a vacuum adsorption end. The multi-axis drive assembly 61 drives the fixed gripping end 62 to move to the sprue and applies vacuum adsorption to fix the sprue. Subsequently, the multi-axis drive assembly 61 drives the fixed gripping end 62 to move along a direction perpendicular to the product surface to apply a static bending force of 12 Newtons.

[0086] During the maintenance of the static bending force, the phase-locked loop (PLL) frequency tracking circuit in the control cabinet initiates frequency tracking. The phase comparator of the PLL frequency tracking circuit compares the phase of the vibration response signal collected by the accelerometer mounted on the fixed fixture 2 with the output phase of the voltage-controlled oscillator (VCO) of the PLL frequency tracking circuit, and controls the output frequency of the VCO based on the phase difference signal. Before the application of the static bending force, the first natural frequency of the injection molded part is 85 Hz; under the prestressed state of a static bending force of 12 N, the overall structural stiffness of the injection molded part decreases, and the first natural frequency of the injection molded part shifts to 82 Hz. The output frequency of the VCO is locked at 82 Hz after real-time adjustment by the PLL frequency tracking circuit. The exciter 63 is an electromagnetic exciter 63, which synchronously injects a bending stress wave with a frequency of 82 Hz into the injection molded part, and the amplitude of the bending stress wave corresponds to the alternating energy input.

[0087] Static bending force and alternating energy are superimposed in the time domain to form a pulsed bending force of 12 Newtons. Under the continuous application of the pulsed bending force, the residual support thin wall, under the combined effect of stress concentration and resonance amplification at the prestress concentration zone, undergoes controlled fracture along the prestress concentration zone within 0.5 seconds, achieving separation of the product from the sprue and causing the sprue to detach. After fracture, the sprue is released by the vacuum adsorption end. There is no chipping or whitening at the edge after separation of the product and the sprue, and the dimensional accuracy of the product meets the assembly requirements of the head-up display.

[0088] Example of a breakage pattern: This embodiment provides an example of applying a pull-off pulse resonance separation force in the sprue milling process of injection molded parts.

[0089] The injection-molded part is a head-up display (HUD) projector lens frame, which is injection molded from a polycarbonate and polymethyl methacrylate composite material. The average wall thickness of the HUD projector lens frame is 2.5 mm. The product is the annular lens barrel body of the HUD projector lens frame, and the sprue is the arc-shaped gate residue on the side of the HUD projector lens frame. The connection area between the product and the sprue is an arc-shaped connecting strip with a connection width of 4.0 mm and a connection thickness of 2.5 mm.

[0090] In the pre-weakening step, the multi-axis drive mechanism 4 drives the base 1 to move the injection molded part relative to the milling assembly 3. The rotating milling assembly 3 cuts blind holes at intervals on the outer surface of the connecting area along the extension direction of the connecting area. The diameter of the blind holes is 1.0 mm, and the spatial distance between adjacent blind holes is 3.0 mm. At the same time, the rotating milling assembly 3 cuts continuous linear weakening grooves between adjacent blind holes. The continuous linear weakening grooves are asymmetrical V-shaped pre-cut grooves. The groove angle of the asymmetrical V-shaped pre-cut groove facing the product side is 130 degrees, and the groove angle of the asymmetrical V-shaped pre-cut groove facing the sprue side is 65 degrees. The groove depth of the asymmetrical V-shaped pre-cut groove is 0.8 mm. The prestress concentration zone is composed of blind holes and continuous linear weakening grooves, and a residual support thin wall with a thickness of 0.20 mm is retained at the bottom of the prestress concentration zone.

[0091] In the stress-guided fracture step, the separation mechanism 6 includes a multi-axis drive assembly 61 and a vibrator 63. The end of the multi-axis drive assembly 61 is provided with a fixed gripping end 62, which is a servo-driven electric gripper. The multi-axis drive assembly 61 drives the fixed gripping end 62 to move to the sprue and clamp it in place. Subsequently, the multi-axis drive assembly 61 drives the fixed gripping end 62 to move in a horizontal tangential direction away from the product to apply a static tensile force of 30 Newtons.

[0092] During the maintenance of the static tensile force, the phase-locked loop (PLL) frequency tracking circuit in the control cabinet initiates frequency tracking. The phase comparator of the PLL frequency tracking circuit compares the phase of the vibration response signal collected by the accelerometer mounted on the fixed fixture 2 with the output phase of the voltage-controlled oscillator (VCO) of the PLL frequency tracking circuit, and controls the output frequency of the VCO based on the phase difference signal. Before the static tensile force is applied, the first natural frequency of the injection molded part is 90 Hz; under the prestressed state of a static tensile force of 30 N, the overall structural stiffness of the injection molded part decreases, and the first natural frequency of the injection molded part shifts to 87 Hz. The output frequency of the VCO is locked at 87 Hz after real-time adjustment by the PLL frequency tracking circuit. The exciter 63 is an electromagnetic ultrasonic longitudinal wave exciter 63, which synchronously injects a tension-compression type ultrasonic longitudinal wave with a frequency of 87 Hz into the injection molded part. The amplitude of the tension-compression type ultrasonic longitudinal wave corresponds to the alternating energy input.

[0093] Static tensile force and alternating energy are superimposed in the time domain to form a pulse breaking force of 30 Newtons. Under the continuous application of the pulse breaking force, the residual support thin wall, under the combined effect of stress concentration and resonance amplification at the prestress concentration zone, undergoes controlled fracture along the prestress concentration zone within 0.4 seconds, achieving separation of the product from the sprue and causing the sprue to detach. After fracture, the servo-electric gripper releases the sprue. The joint between the product and the sprue is smooth and crack-free, extending towards the product side, and no vibration whitening defects are observed on the optical surface of the product.

[0094] Specifically, during the application of the pulsed resonant separation force, the natural frequency shift of the injection molded part is monitored by a sensor mounted on the fixed fixture 2. The natural frequency shift of the injection molded part satisfies the following equation:

[0095] in The overall structural stiffness decreases continuously over time. For system quality, the system includes injection molded parts, a fixed fixture 2, and a fixed gripping end 62; the control cabinet of the sprue milling separator is equipped with a phase-locked loop frequency tracking circuit, which includes a phase comparator and a voltage-controlled oscillator. The phase comparator compares the phase of the collected vibration response signal with the output phase of the voltage-controlled oscillator, and controls the output frequency of the voltage-controlled oscillator according to the phase difference signal, so that the superposition frequency of the pulse resonance separation force is kept synchronized with the current natural frequency after the offset in real time.

[0096] By incorporating a phase-locked loop (PLL) frequency tracking circuit into the control cabinet of the sprue milling separator, and by including a phase comparator and a voltage-controlled oscillator in the PLL frequency tracking circuit, automatic tracking and real-time adjustment of the pulse resonance separation force frequency are achieved.

[0097] By having the phase comparator compare the phase of the acquired vibration response signal with the output phase of the voltage-controlled oscillator and control the output frequency of the voltage-controlled oscillator according to the phase difference signal, the superposition frequency of the pulse resonance separation force is kept synchronized with the current natural frequency after the offset in real time. This achieves real-time tracking of the resonance frequency and ensures the continuous stability of the resonance separation efficiency during the continuous decay of structural stiffness.

[0098] Based on the stress-guided fracture process, a pulse resonance separation mechanism based on real-time tracking of the structure's natural frequency is introduced. This upgrades the traditional single static separation force into a composite separation force that combines static prestress and dynamic resonance energy. This allows the residual support thin wall to achieve controllable fracture with extremely low external force under the resonance amplification effect, fundamentally avoiding product edge damage caused by excessive separation force.

[0099] Specifically, the multi-axis drive mechanism 4 is a multi-axis CNC slide. In the pre-weakening step, the milling assembly 3 uses an asymmetric V-shaped milling cutter mounted on it to cut a continuous linear weakening groove on one side of the connecting area as the multi-axis CNC slide drive base 1 moves along the multi-axis linkage trajectory. The multi-axis linkage trajectory is determined based on the three-dimensional curved surface profile and equivalent stress concentration factor of the connecting area. The real-time calculation results are generated, which enables the asymmetric V-shaped end mill to maintain a constant cutting depth along the extension direction of the connecting area.

[0100] In this embodiment, the separation mechanism 6 is a robotic arm separation mechanism 6, the multi-axis drive assembly 61 is a multi-axis robotic arm, the fixed gripping end 62 is a negative pressure suction head, and the vibrator 63 is integrated inside the fixed gripping end 62 or disposed on the outer wall of the fixed gripping end 62 so that the alternating energy output by the vibrator 63 is directly coupled and transmitted to the sprue component through the fixed gripping end 62.

[0101] By specifically configuring the separation mechanism 6 as a robotic arm separation mechanism 6, and making the multi-axis drive assembly 61 a multi-axis robotic arm, specifically a six-degree-of-freedom industrial robotic arm (e.g., FANUC's LR Mate 200iD series robot, or KUKA's KR AGILUS series small six-axis robot). Those skilled in the art should understand that the mechanical topology and brand of the multi-axis robotic arm are not limited to the aforementioned conventional six-axis industrial robots. In other parallel embodiments, the multi-axis robotic arm can also preferably be a six-degree-of-freedom or seven-degree-of-freedom intelligent collaborative robotic arm with joint torque self-sensing capability (e.g., Universal Robots' UR5e collaborative robot, or KUKA's LBR iiwa lightweight seven-axis collaborative robot). Furthermore, in simplified application scenarios requiring only single torsional or shear fracture separation, those skilled in the art can also use a horizontal multi-joint robot (SCARA robotic arm, such as Epson's G6 series robot), or a multi-axis CNC linear slide combination based on serial-parallel cascade (Cartesian coordinate robot) as an equivalent drive source replacement.

[0102] The fixed gripping end 62 is a negative pressure suction head. Utilizing the multi-degree-of-freedom motion capability of the multi-axis robotic arm, the spatial orientation of the fixed gripping end 62 can be flexibly adjusted and multi-directional separation force can be applied. The negative pressure suction head grips the sprue component with negative pressure, facilitating the application of alternating energy output from the vibrator 63 to the sprue component. In practical industrial applications, the negative pressure suction head can preferably be a commercially available industrial vacuum gripping assembly, which includes an integrated intelligent electric vacuum gripper fixed to the flange at the end of the robotic arm (such as the VGC10 electrically controlled negative pressure gripper from OnRobot in Denmark, or the piCOBOT integrated vacuum gripper module from Piab in Sweden); or it can adopt a split structure, consisting of a high-rigidity metal suction head frame and an automotive-grade non-marking elastomer bellows suction cup rigidly mounted at its bottom (such as the SAB series or FSGA series accordion-style vacuum suction cups from SCHMALZ in Germany). In the stress-guided fracture step, the negative pressure suction head applies a high negative pressure of not less than -0.6 bar to -0.85 bar to the surface of the injection molded part's sprue through its external Venturi vacuum generating pipeline. Utilizing the strong adsorption surface generated by the atmospheric pressure difference as a load transfer medium, the static prestress output by the multi-axis robotic arm is rigidly transferred to the sprue without mechanical scratches. In other embodiments, the structure of the fixed gripping end 62 is not limited to the aforementioned negative pressure adsorption architecture. In other parallel equivalent embodiments, for irregular shapes with large holes or severe geometric unevenness on the sprue surface, the negative pressure suction head can also be equivalently replaced with an adaptive large-area foam vacuum gripper (e.g., Schmeiss's FMC series foam suction head). Furthermore, the fixed gripping end 62 can also use a pneumatic contour gripper, pneumatic fingers (such as SMC's MHF2 / MHZ2 series pneumatic grippers), or an electromagnetic / permanent magnet gripping mechanism based on magnetic adsorption principles as equivalent hardware replacements for the end of the multi-axis drive assembly 61.

[0103] By integrating the vibrator 63 into the fixed gripping end 62 or setting it on the outer wall of the fixed gripping end 62, the alternating energy output by the vibrator 63 is directly coupled and transmitted to the sprue component through the fixed gripping end 62, avoiding the attenuation and scattering of alternating energy in the transmission path, realizing the efficient directional transmission of alternating energy to the sprue component, and improving the energy utilization rate of pulse resonance separation force.

[0104] Based on the pulse resonance separation force application method, by integrating the exciter 63 into the fixed gripping end 62 at the end of the multi-axis robotic arm, the direct coupling and transfer of alternating energy from the exciter 63 to the sprue component is realized, which significantly improves the resonance energy transfer efficiency and the spatial flexibility of the separation action.

[0105] Before the pre-weakening step, this embodiment also includes the following steps: The detection process involves acquiring the characteristic distribution parameters of the connection region using a photoelastic polarization imaging detection system. These parameters include the geometric contour, connection width, connection thickness, and the internal residual stress birefringence phase distribution parameter matrix. The parameter calculation step involves inputting the characteristic distribution parameters into the mechanical calculation module of the control cabinet to calculate the processing parameters of the prestress concentration zone. The processing parameters include the weakening structure aperture, spatial hole spacing, residual thin wall thickness, linear weakening groove angle and groove depth. The residual thin wall thickness is determined based on the stress gradient distribution along the thickness direction of the connecting area in the internal residual stress birefringence phase distribution parameter matrix. The trajectory generation step involves reconstructing and generating the CNC relative machining trajectory of the multi-axis drive mechanism 4 based on the machining parameters.

[0106] By adding a detection step before the pre-weakening step, the geometric contour, connection width, connection thickness, and internal residual stress birefringence phase distribution parameter matrix of the connection region are acquired using a photoelastic polarization imaging detection system, thus realizing online non-destructive testing of the geometry of the connection region and the internal residual stress distribution.

[0107] By adding a parameter calculation step, the characteristic distribution parameters are input into the mechanical calculation module of the control cabinet to calculate the processing parameters of the prestress concentration zone, including the weakening structure aperture, spatial hole spacing, residual thin wall thickness, linear weakening groove angle and groove depth. The residual thin wall thickness is determined according to the stress gradient distribution along the thickness direction of the connecting area in the internal residual stress birefringence phase distribution parameter matrix, thus realizing the personalized matching between the pre-weakening processing parameters and the internal residual stress distribution of the material.

[0108] By adding a trajectory generation step, the CNC relative machining trajectory of the multi-axis drive mechanism 4 is reconstructed and generated based on the machining parameters, realizing the digital precise planning and automated execution of the pre-weakened milling path.

[0109] Based on the photoelastic polarization imaging detection system and mechanical calculation module, a pre-processing closed-loop process of detection-calculation-trajectory generation is introduced. This allows the processing parameters of the pre-weakening step to be customized according to the actual residual stress distribution of each batch of injection molded parts. This avoids the risk of uncontrollable fracture caused by using uniform fixed processing parameters and significantly improves the adaptability of the process to the differences in materials of different batches and the reliability of fracture separation.

[0110] The above description is only a preferred embodiment of the present invention. For those skilled in the art, there will be changes in the specific implementation and application scope based on the ideas of the present invention. The content of this specification should not be construed as a limitation of the present invention.

Claims

1. A sprue milling process for injection molded parts, the injection molded parts comprising a product and sprue components, characterized in that, The sprue milling process is performed using a sprue milling separator, which includes a base (1) with a processing position (11), a fixed fixture (2) on the base (1), a milling assembly (3) in the processing position (11), a multi-axis drive mechanism (4) rigidly connected to the base (1) and used to drive the base (1) to perform multi-axis spatial displacement, an attitude adjustment mechanism (5) between the base (1) and the fixed fixture (2), and a separation mechanism (6) on one side of the base (1). The sprue milling process includes the following steps: In the fixing step, the product is clamped and fixed by the fixing fixture (2), and the connection area between the product and the sprue is exposed at the processing position (11). In the pre-weakening step, the multi-axis drive mechanism (4) drives the base (1) to move the injection molded part relative to the milling assembly (3), and the rotating milling assembly (3) mills and thins the connection area to form a prestress concentration zone in the connection area, and retains a residual support thin wall at the bottom of the prestress concentration zone. In the stress-guided fracture step, under the premise that the product's clamping state remains unchanged, the separation mechanism (6) applies a separation force to the sprue component, causing the residual support thin wall to fracture along the prestress concentration zone, thereby separating the product from the sprue component and causing the sprue component to fall off. In the edge finishing step, after the product is separated from the sprue, the multi-axis drive mechanism (4) drives the machine base (1) to move the product relative to the milling assembly (3), and the milling assembly (3) is used to perform chamfer finishing on the broken edge of the product; during the finishing process, the control cabinet receives the cutting force signal collected by the spindle force sensor, and controls the attitude adjustment mechanism (5) to adjust the spatial relative attitude of the product driven by the fixed fixture (2) in real time according to the cutting force signal.

2. The sprue milling process for injection molded parts according to claim 1, characterized in that, The sprue milling separator also includes a photoelastic polarization imaging detection system and a spindle three-dimensional force sensor integrated at the end of the milling assembly (3); The attitude adjustment mechanism (5) is a force-controlled attitude adjustment mechanism (5), which includes: The first mounting plate (51) is used to support the fixing fixture (2); The second mounting plate (52) is fixed to the base (1); Magnetorheological damping elastic elements (53) are arrayed between the first mounting plate (51) and the second mounting plate (52); The excitation coil (54) is disposed around the magnetorheological damping elastic element (53); A flexible force-controlled direct drive driver (55) is fixed on the second mounting plate (52) and is used to drive the first mounting plate (51) to deflect in order to change the spatial relative posture of the product on the fixed fixture (2). The control cabinet includes a microprocessor, a memory and a mechanical calculation module, used to change the magnitude of the current input to the excitation coil (54) to adjust the damping ratio and stiffness of the magnetorheological damping elastic element (53); During the edge finishing step, the control cabinet performs the following linkage control: The first mounting plate (51) is driven to deflect in spatial rotational degrees of freedom by the flexible force-controlled direct drive driver (55) to finely adjust the spatial relative posture of the product on the fixed fixture (2) in real time. Meanwhile, based on the time-domain fluctuation characteristics of the cutting force signal collected by the spindle three-dimensional force sensor, the magnitude of the current input to the excitation coil (54) is dynamically changed to adjust the damping ratio and stiffness of the magnetorheological damping elastic element (53) in real time. The attitude deflection of the flexible force-controlled direct drive driver (55) and the damping adjustment of the magnetorheological damping elastic element (53) are controlled by the control cabinet in coordination according to the cutting force signal, forming a force-position coupling closed loop; The magnetorheological damping elastic element (53) is in a first stiffness and first damping state when the excitation coil (54) is not energized or when a basic sustaining current is applied. When a set saturation current is applied, a rheological phase change occurs, and it switches to a second stiffness and second damping state where both stiffness and damping increase.

3. The sprue milling process for injection molded parts according to claim 2, characterized in that, In the edge finishing step, when the spindle three-dimensional force sensor detects that the fluctuation rate of the cutting force signal exceeds a preset safety threshold, the control cabinet performs spatial relative attitude adjustment and adaptive transient hardening locking. The calculation and driving of the spatial attitude compensation vector includes the following steps: The microprocessor performs real-time subtraction calculation between the instantaneous cutting force vector acquired online by the spindle three-dimensional force sensor and the preset target ductile cutting force vector in the memory to construct a three-dimensional mechanical deviation matrix. The microprocessor calls the physical augmented neural network mechanical calculation program in the memory, and combines the internal residual stress birefringence phase distribution parameters of the injection molded part that are pre-acquired and stored in the memory to perform online inverse demapping of the three-dimensional mechanical deviation matrix in order to calculate the angular displacement compensation amount required by the first mounting plate (51) in the spatial rotational degree of freedom, and reconstruct the spatial attitude compensation vector according to the angular displacement compensation amount. The control cabinet generates an attitude control current based on the spatial attitude compensation vector and outputs the attitude control current to the flexible force-controlled direct drive driver (55) to drive the first mounting plate (51) to perform multi-dimensional micro-amplitude deflection, thereby realizing real-time compensation and fine-tuning of the spatial relative attitude of the product carried on the fixed fixture (2).

4. The sprue milling process for injection molded parts according to claim 3, characterized in that, When the control cabinet drives the first mounting plate (51) to deflect according to the spatial attitude compensation vector and implements adaptive transient hardening lock on the first mounting plate (51), the following cooperative control timing is satisfied in the time domain: During the T0 to T1 time domain, the magnetorheological damping elastic element (53) maintains a first stiffness and a first damping state under the basic sustaining current of the excitation coil (54). The control cabinet controls the magnetorheological current of the excitation coil (54) to monotonically increase from the basic sustaining current to a set saturation current value. During the increase of the magnetorheological current, the control cabinet maintains the drive current input to the flexible force-controlled direct drive driver (55) constant so that the flexible force-controlled direct drive driver (55) maintains the current mechanical output posture position. At time T1 in the time domain, when the rheological current reaches the set saturation current value, the excitation coil (54) excites the target magnetic field to cause the magnetorheological damping elastic element (53) to undergo a rheological phase transition, so that the magnetorheological damping elastic element (53) switches from the first stiffness and the first damping state to the second stiffness and the second damping state. During the T1 to T2 phase in the time domain, when the magnetorheological damping elastic element (53) is in the second stiffness and second damping state, the control cabinet releases the current maintenance state of the flexible force-controlled direct drive driver (55) and outputs the attitude adjustment drive current to drive the first mounting plate (51) to deflect under the rigid vibration suppression constraint provided by the second stiffness and second damping state. The time interval between the moment T0 when the rheological current begins to monotonically increase and the moment T1 when the first mounting plate (51) actually begins to deflect is defined as the micro-phase change delay window, and the duration of the micro-phase change delay window is controlled between 1.5 milliseconds and 3 milliseconds. The duration is matched with the rheological response time constant of the magnetorheological damping elastic element (53).

5. The sprue milling process for injection molded parts according to claim 4, characterized in that, During the deflection of the first mounting plate (51) under the hardening constraints of the second stiffness and second damping state, the adaptive transient hardening lock direction-selective hardening includes the following steps: The control cabinet calculates the dominant normal direction of the cutting chatter online based on the cutting force signal collected by the spindle three-dimensional force sensor; The control cabinet groups the arrayed excitation coils (54) according to the vertical distance between each excitation coil (54) and the normal dominant direction, and outputs different independent phase change current values ​​independently and asymmetrically for the excitation coils (54) in different groups, wherein the independent phase change current values ​​received by the excitation coils (54) in each group decrease in a gradient along the direction away from the normal dominant direction; Each of the magnetorheological damping elastic elements (53) generates differentiated rheology under the local magnetic field excited by asymmetric current, so as to improve the translational degree of freedom of the first mounting plate (51) in the direction parallel to the rotation axis of the milling assembly (3) and the spatial motion resistance in the two rotational degrees of freedom perpendicular to the rotation axis, so that the shear stiffness of each of the corresponding magnetorheological damping elastic elements (53) in the flutter direction corresponding to the translational degree of freedom and the two rotational degrees of freedom is hardened to the second stiffness; Meanwhile, the control cabinet locks the target deflection direction of the flexible force-controlled direct drive driver (55) currently performing spatial attitude compensation, and maintains a low shear resistance state by controlling the corresponding magnetorheological damping elastic element (53) in the target deflection direction, so as to maintain the motion compliance of the first mounting plate (51) in the target deflection direction.

6. The sprue milling process for injection molded parts according to claim 2, characterized in that, The prestress concentration zone formed in the pre-weakening step is composed of a plurality of blind holes cut along the connection area and a continuous linear weakening groove. The plurality of blind holes are arranged at intervals along the extension direction of the connection area, and the continuous linear weakening groove extends continuously along the extension direction and penetrates the area between adjacent blind holes. The prestress concentration strip is only formed on one side surface of the connection area; The continuous linear weakening groove is an asymmetric V-shaped pre-cut groove. The groove angle of the asymmetric V-shaped pre-cut groove facing the product side is larger than the groove angle facing the sprue side, so that the fracture crack at the prestress concentration zone is driven by the asymmetric stress field to deflect and extend towards the sprue side, and inhibits the extension of the crack towards the product side.

7. The sprue milling process for injection molded parts according to claim 1, characterized in that, The separation mechanism (6) includes a multi-axis drive assembly (61) and a vibrator (62). The end of the multi-axis drive assembly (61) is provided with a fixed gripping end (611). The separation force in the stress-guided fracture step is a pulse resonance separation force. The application process of the pulse resonance separation force includes: The fixed gripping end (611) is driven by the multi-axis drive assembly (61) to apply static prestress to the sprue. During the maintenance of the static prestress, the vibrator (62) synchronously injects alternating energy into the injection molded part. The frequency of the alternating energy is equal to the current first-order natural frequency of the injection molded part under the action of the static prestress. The static prestress and the alternating energy are superimposed in the time domain to form the pulse resonance separation force. The pulse resonance separation force is applied in one or a combination of the following ways: In the torsion form, the fixed gripping end (611) is driven by the multi-axis drive assembly (61) to rotate around the central axis of the connection area to apply a static torque, while the exciter (62) injects a shear stress wave tangentially around the central axis, which superimposes to form a pulse torsion torque, the pulse torsion torque being 0.5 N·m to 2 N·m; In the bending form, the fixed gripping end (611) is driven by the multi-axis drive assembly (61) to move in the normal direction perpendicular to the product surface to apply a static bending force, while the vibrator (62) injects a bending stress wave in the thickness normal direction of the connection area, which superimposes to form a pulse bending force, the pulse bending force being 5N to 20N. In the tensile breaking mode, the fixed gripping end (611) is driven by the multi-axis drive assembly (61) to move along the horizontal tangential direction away from the product to apply a static tensile force, while the vibrator (62) injects tensile-compression type ultrasonic longitudinal waves along the horizontal tangential direction to form a pulse tensile breaking force, which is 10N to 50N.

8. The sprue milling process for injection molded parts according to claim 7, characterized in that, The separation mechanism (6) is a robotic arm separation mechanism, the multi-axis drive assembly (61) is a multi-axis robotic arm, the fixed gripping end (611) is a negative pressure suction head, and the vibrator (62) is integrated inside the fixed gripping end (611) or disposed on the outer wall of the fixed gripping end (611) so that the alternating energy output by the vibrator (62) is directly coupled and transmitted to the sprue component through the fixed gripping end (611).

9. The sprue milling process for injection molded parts according to claim 2, characterized in that, Prior to the pre-weakening step, the following steps are also included: The detection step involves acquiring the characteristic distribution parameters of the connection region using the photoelastic polarization imaging detection system. These characteristic distribution parameters include the geometric contour, connection width, connection thickness, and internal residual stress birefringence phase distribution parameter matrix. The parameter calculation step involves inputting the characteristic distribution parameters into the mechanical calculation module of the control cabinet to calculate the processing parameters of the prestress concentration zone. The processing parameters include the weakening structure aperture, spatial hole spacing, residual thin wall thickness, linear weakening groove angle, and groove depth. The residual thin wall thickness is determined based on the stress gradient distribution along the thickness direction of the connecting region in the internal residual stress birefringence phase distribution parameter matrix. The trajectory generation step involves reconstructing and generating the CNC relative machining trajectory of the multi-axis drive mechanism (4) based on the machining parameters.

Images