Manufacturing process of obdurability dust collector injection molding part body

Abstract

The invention relates to the technical field of injection molding, and discloses a manufacturing process of a tough dust collector injection molding part body, which comprises the following steps: firstly, injecting a main thermoplastic material into a cavity of a preheated rapid temperature change mold, and after the main thermoplastic material is filled, switching to a zero pressure maintaining state or a near-zero pressure maintaining state; meanwhile, the rapid temperature change mold is rapidly cooled, so that a low-stress cured surface layer is formed on the outer surface of the dust collector injection molding part body, and a melting core is formed in the cured surface layer; and a pressure sensor is arranged in the cavity. After filling of the main thermoplastic material is completed, the main thermoplastic material is immediately switched to the zero pressure maintaining state or the near-zero pressure maintaining state for skin curing, the dust collector injection molding part body can be formed in the molecular chain loose state through the technology, the brittleness of the part is greatly reduced, and the service life of the part is prolonged. And the overall toughness and the environmental stress cracking (ESCR) resistance of the dust collector injection molding part body are remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of injection molding technology, specifically to a manufacturing process for a tough vacuum cleaner injection molded part body. Background Technology

[0002] As a core component of household appliances, the injection-molded body of a vacuum cleaner must meet stringent requirements for both strength and high appearance quality in its manufacturing process. In high-end vacuum cleaner designs, the surface quality of components has reached the A-grade mirror high-gloss standard. However, to ensure structural strength and installation stability, components inevitably need to have complex structures such as thick-walled areas, reinforcing ribs, and snap-fit ​​mechanisms. This leads to an inherent technical contradiction that is difficult to reconcile during the manufacturing process.

[0003] Current mainstream injection molding processes have inherent flaws in resolving this contradiction. On the one hand, to eliminate surface shrinkage marks in thick-walled areas, traditional injection molding processes must apply high holding pressure for a long time after filling. However, this high-pressure holding process "freezes" huge tensile and shear stresses inside the plastic part, especially in areas with abrupt geometric changes and melt convergence. The resulting high residual internal stress is the root cause of brittle cracking and significant strength reduction in vacuum cleaner injection molded parts when dropped, impacted, or in contact with stress cracking agents (ESCR). This makes it impossible to guarantee the toughness of the parts.

[0004] On the other hand, although processes such as rapid temperature change (RHCM) can effectively improve the surface finish and weld line strength, they still rely on subsequent holding pressure steps to eliminate shrinkage marks. If high holding pressure is not used (such as choosing zero or low holding pressure), the molten core in the thick-walled area will inevitably collapse inward when it cools and shrinks, causing the outer solidified skin layer to collapse inward, resulting in unacceptable severe surface shrinkage marks, making it impossible to meet the Class A appearance quality requirements. Even if traditional gas-assisted injection molding (GAIM) or microcellular foaming (MuCell) technologies are used to replace part of the holding pressure, although shrinkage marks can be eliminated to some extent, GAIM has a complex air channel layout and is prone to producing shrinkage cavities in non-air channel areas. While microcellular foaming technology reduces the weight of the part and eliminates shrinkage marks, the air mark defects such as silver streaks it produces will directly destroy the Class A high-gloss surface quality pursued by the vacuum cleaner injection molded part. This process increases the brittleness of the part, thereby reducing the overall strength and toughness of the vacuum cleaner injection molded part. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a manufacturing process for a high-toughness vacuum cleaner injection molded part body, solving the problem that the manufacturing process of vacuum cleaner injection molded parts bodies in existing technologies results in products with low overall strength and toughness.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a manufacturing process for a tough vacuum cleaner injection molded part body, comprising the following steps:

[0007] S1. First, inject the main thermoplastic material into the cavity of the preheated rapid temperature change mold. After the main thermoplastic material is filled, switch to zero pressure or near-zero pressure state and simultaneously cool the rapid temperature change mold quickly, thereby forming a low-stress cured skin layer on the outer surface of the vacuum cleaner injection molded part body, and forming a molten core inside the cured skin layer.

[0008] S2. By using a pressure sensor installed in the cavity, the cavity pressure drop caused by the cooling and shrinkage of the molten core is monitored in real time; when the cavity pressure drops to a preset compensation trigger pressure lower limit, a compensating agent masterbatch containing a chemical foaming agent is injected into the molten core. The chemical foaming agent is activated and foamed by heating to generate internal compensation pressure, thereby offsetting the cooling and shrinkage of the molten core.

[0009] S3. When the cavity pressure is detected to rise to the preset compensation stop pressure limit, stop injecting the compensation agent masterbatch. After compensation in all areas has been completed (according to closed-loop feedback), the plastic part continues to cool in the mold until the near-zero stress skin layer and the internal micro-foaming compensation core layer are completely solidified. Finally, open the mold and eject the processed vacuum cleaner injection molded part.

[0010] Preferably, the step of injecting the main thermoplastic material into the cavity of the preheated rapid temperature change mold specifically involves: preheating the cavity of the rapid temperature change mold to a temperature of 120~150°C; and injecting the main thermoplastic material at a high speed of 100~300mm / s.

[0011] Preferably, the switching to zero or near-zero holding pressure state and the simultaneous rapid cooling of the rapid temperature change mold specifically involves: switching the injection pressure to a zero or near-zero holding pressure state of 0~1.0MPa; and simultaneously cooling the cavity of the rapid temperature change mold to a temperature of 60~90℃.

[0012] Preferably, the pressure thresholds on which the real-time monitoring, injection, and stopping of injection are based are set as follows: the lower limit of the compensation trigger pressure is in the range of 0.5~2.0MPa; the upper limit of the compensation stop pressure is in the range of 1.0~5.0MPa, and the upper limit of the compensation stop pressure is greater than the lower limit of the compensation trigger pressure.

[0013] Preferably, the main thermoplastic material is a PC / ABS alloy; the substrate of the compensator masterbatch is the same as or compatible with the main thermoplastic material.

[0014] Preferably, the chemical foaming agent in the compensator masterbatch has a mass fraction of 5% to 15%.

[0015] Preferably, the compensator masterbatch includes at least two types: a first compensator containing a high-temperature slow-release chemical foaming agent with an activation temperature range of 190~220 ℃; and a second compensator containing a medium-temperature rapid-release chemical foaming agent with an activation temperature range of 160~190 ℃.

[0016] Preferably, the injection of compensating agent masterbatch containing chemical foaming agent into the molten core is performed in sections and asynchronously, wherein: the first compensating agent is injected into the preset thickest wall area of ​​the vacuum cleaner injection molded part body; and the second compensating agent is injected into the preset second thickest wall area of ​​the vacuum cleaner injection molded part body.

[0017] Preferably, the process parameters for injecting the compensator masterbatch containing a chemical foaming agent into the molten core are: the injection temperature is set to 210~240 ℃, and the injection speed is 10~50 mm / s.

[0018] Preferably, the process is performed by a dual-injection molding machine, wherein the main injection unit is used to inject the main thermoplastic material, and the auxiliary injection unit is used to inject the compensator masterbatch; and the main thermoplastic material and the compensator masterbatch are respectively delivered to different gates of the cavity through a multi-channel sequential valve needle hot runner system.

[0019] This invention provides a manufacturing process for a high-strength, tough vacuum cleaner injection molded part body. It offers the following advantages:

[0020] 1. This invention fundamentally avoids the high residual internal stress introduced by traditional high holding pressure processes by immediately switching to zero or near-zero holding pressure for skin curing after the main thermoplastic material is filled. This process allows the vacuum cleaner injection molded part to be formed in a relaxed molecular chain state, which greatly reduces the brittleness of the part and significantly improves the overall toughness and environmental stress cracking (ESCR) resistance of the vacuum cleaner injection molded part.

[0021] 2. This invention utilizes a rapid temperature change mold and high-speed injection to obtain a high-gloss cured skin layer; subsequently, without applying external high pressure, compensating agent masterbatch is injected into the internal molten core, and the internal compensation pressure generated by its activation and foaming is used to counteract cooling shrinkage. This mechanism of separating surface molding and internal compensation allows the vacuum cleaner injection molded part to obtain a perfect A-grade high-gloss appearance while completely eliminating surface shrinkage defects in thick-walled areas.

[0022] 3. In the manufacturing process of this invention, the cavity of the rapid temperature change mold is preheated to a high temperature before the main thermoplastic material is injected. This high temperature mold wall environment ensures that the melt maintains extremely high temperature and fluidity at the flow end (merging point), which promotes the full diffusion and entanglement of polymer chains at the weld line interface. Therefore, the weld line strength of the vacuum cleaner injection molded body manufactured by this process is significantly enhanced, improving the structural reliability of the part under stress and further ensuring toughness.

[0023] 4. This invention uses a pressure sensor installed within the mold cavity to monitor the shrinkage process of the molten core in real time. The process employs a closed-loop control logic based on pressure lower limit trigger compensation and pressure upper limit stop compensation. This adaptive compensation mechanism, combined with a strategy of independent asynchronous injection into different areas, ensures a precise match between the compensation amount and the actual shrinkage amount, avoiding local undercompensation or overcompensation. This guarantees that the vacuum cleaner injection molded part has excellent dimensional stability and low warpage.

[0024] 5. This invention achieves differentiated compensation for different structural parts by precisely injecting compensator masterbatch with specific properties into the molten core region that matches its cooling rate, greatly improving the adaptability of the manufacturing process to complex structural parts. Attached Figure Description

[0025] Figure 1 This is one of the method flowcharts of the present invention;

[0026] Figure 2 This is the second flowchart of the method of the present invention;

[0027] Figure 3 This is the third flowchart of the method of the present invention;

[0028] Figure 4 This is the fourth flowchart of the method of the present invention. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Please see the appendix Figure 1 -Appendix Figure 4 This invention provides a manufacturing process for a tough vacuum cleaner injection molded part, comprising the following steps:

[0031] S1. First, inject the main thermoplastic material into the cavity of the preheated rapid temperature change mold. After the main thermoplastic material is filled, switch to zero or near-zero holding pressure and simultaneously rapidly cool the rapid temperature change mold. This forms a low-stress cured skin layer on the outer surface of the vacuum cleaner injection molded part, and a molten core is formed inside the cured skin layer. Then, inject the main thermoplastic material into the cavity of the preheated rapid temperature change mold. Specifically, preheat the cavity of the rapid temperature change mold to a temperature of 120~150℃ and inject at a high speed of 100~300mm / s. For the main thermoplastic material, switch to zero or near-zero holding pressure state, and simultaneously rapidly cool the rapid temperature change mold. Specifically, switch the injection pressure to 0~1.0MPa at zero or near-zero holding pressure; and simultaneously cool the cavity of the rapid temperature change mold to a temperature of 60~90℃. The pressure thresholds for real-time monitoring, injection, and stopping injection are set as follows: the lower limit of the compensation trigger pressure is 0.5~2.0MPa; the upper limit of the compensation stop pressure is 1.0~5.0MPa, and the upper limit of the compensation stop pressure is greater than the lower limit of the compensation trigger pressure.

[0032] Specifically, the RHCM system is first started to instantly heat the surface of the mold cavity to a first temperature, which is preferably set to [temperature value missing]. This temperature is higher than the heat distortion temperature of the main thermoplastic material (PC / ABS). This ensures that the melt maintains extremely low viscosity and high fluidity upon contact with the mold wall. After the mold surface reaches the preset first temperature, the main injection unit... High-speed injection of the primary thermoplastic material allows the cavity to be formed in a very short time (e.g., Fill to The combination of high-temperature mold walls and high-speed injection ensures that the melt maintains a high temperature at the flow end (merging point), greatly promoting the full diffusion and entanglement of polymer chains at the weld line, forming a high-strength weld line. Simultaneously, the high-temperature melt perfectly replicates the mirror finish of the mold, resulting in a Grade A appearance. The main injection unit immediately stops applying pressure and switches to [other injection methods] the instant the main thermoplastic material is filled. The zero or near-zero holding pressure state and rapid cooling cause the outer surface of the plastic part in contact with the mold wall to solidify rapidly, "freezing" the high-gloss surface morphology and relaxed molecular chain structure, thus forming a low-stress cured skin layer. When the cured skin layer is formed, due to the low thermal conductivity of plastic, the interior of the vacuum cleaner injection molded part (especially the thick-walled area) is still in a high-temperature molten core state.

[0033] S2. A pressure sensor installed inside the mold cavity monitors in real time the decrease in cavity pressure caused by the cooling and shrinkage of the molten core. When the cavity pressure drops to a preset lower limit of the compensation trigger pressure, a compensator masterbatch containing a chemical foaming agent is injected into the molten core. The chemical foaming agent is activated and foamed upon heating to generate internal compensation pressure, thereby offsetting the cooling and shrinkage of the molten core. The main thermoplastic material is a PC / ABS alloy. The base material of the compensator masterbatch is the same as or compatible with the main thermoplastic material. The mass fraction of the chemical foaming agent in the compensator masterbatch is 5%~15%. The first compensator contains a high-temperature slow-release chemical foaming agent with an activation temperature range of 190~220 ℃; the second compensator contains a chemical foaming agent with an activation temperature range of 160~190 ℃. The injection of a medium-temperature, fast-release chemical foaming agent at ℃ into the melt core, along with the injection of a compensator masterbatch containing the chemical foaming agent, is performed in sections and asynchronously. Specifically: the first compensator is injected into the preset thickest wall area of ​​the vacuum cleaner injection molded part body; the second compensator is injected into the preset second thickest wall area of ​​the vacuum cleaner injection molded part body. The process parameters for injecting the compensator masterbatch containing the chemical foaming agent into the melt core are: injection temperature set at 210~240 ℃, and injection speed at 10~50 mm / s.

[0034] Specifically, in step S1, since no high holding pressure is applied, the molten core will inevitably undergo severe volume shrinkage during the cooling process. If left untreated, this will cause the solidified skin layer to collapse inward, forming severe surface shrinkage marks. This step initiates real-time monitoring of this shrinkage. The pressure sensor installed in the cavity begins high-frequency monitoring of the cavity pressure. When the molten core begins to shrink, the pressure in the cavity will drop rapidly. The system presets a compensation trigger pressure lower limit. The preferred range is 0.5–2.0 MPa, and this threshold represents the point at which the molten core has begun to shrink irreversibly.

[0035] When any pressure sensor (e.g.) The system detected a decrease in cavity pressure in its region, which then reached a preset threshold. At that moment, the control system immediately recognizes that contraction in that specific area has begun and instantaneously triggers the auxiliary injection unit to open the corresponding compensation valve needle. ), auxiliary injection unit with At a medium to low speed, the corresponding compensator masterbatch (B1 or B2) is injected into the still-molten core through the compensator gate. The injection temperature of the compensator masterbatch is set to... This temperature ensures it is higher than the activation temperature of the chemical foaming agents in B1 and B2. After the compensator masterbatch enters the high-temperature molten core, the chemical foaming agent (CBA) it carries is immediately decomposed by heat, releasing trace amounts of gas (such as...). , The molten core forms a dense microporous structure. The expansion force of these micropores generates a gentle, uniform, and isotropic internal compensating pressure within the plastic part. This pressure holds the cooling, solidified skin layer in place, keeping it flat and thus counteracting the cooling contraction of the molten core. However, for vacuum cleaner bodies with complex structures and large differences in wall thickness, the contraction timing and amount differ in different areas. Pressure sensors located in the thickest wall area (e.g., The control system triggers the injection of a first compensator (B1, high-temperature slow-release type) to match its slow cooling and contraction process, and pressure sensors located in the sub-thick-walled region (e.g.) ), possibly Only then is it triggered that the control system will trigger the injection of a second compensator (B2, medium-temperature rapid-release type) to match its faster cooling and shrinkage process. This partitioned, asynchronous, gradient compensation based on real-time feedback and different materials ensures that the shrinkage of each area is accurately compensated, avoiding local undercompensation (still shrinkage marks) or overcompensation (stress generation).

[0036] S3. When the cavity pressure is detected to rise to the preset compensation stop pressure limit, stop injecting the compensation agent masterbatch. After compensation in all areas has been completed (according to closed-loop feedback), the plastic part continues to cool in the mold until the near-zero stress skin layer and the internal micro-foamed compensation core layer are completely solidified. Finally, open the mold and eject the processed vacuum cleaner injection molded part.

[0037] Specifically, the foaming of the compensating agent causes the cavity pressure to rise, and the system presets a compensation stop pressure upper limit ( The preferred range is 1.0. 5.0 MPa (and must be greater than) , It is a much lower pressure value than traditional holding pressure, set solely to ensure that shrinkage is completely offset without imposing new residual stress on the plastic part, when the pressure sensor... Pressure was detected to rise to When this happens, the control system immediately closes the corresponding compensation valve needle ( Stop the compensation injection in that area. After compensation in all areas has been completed (based on closed-loop feedback), the plastic part continues to be held under pressure and cooled in the mold (total cooling time preferably 20 minutes). (45s) until the low-stress cured skin layer and the internal micro-foaming compensation core are completely cured. Finally, the mold is opened and ejected to obtain a tough vacuum cleaner injection molded part body with an A-grade mirror appearance, no shrinkage marks, extremely low internal stress and high weld line strength.

[0038] The process is performed by a dual-injection stage injection molding machine, where the main injection unit is used to inject the main thermoplastic material and the auxiliary injection unit is used to inject the compensator masterbatch; and the main thermoplastic material and compensator masterbatch are delivered to different gates of the cavity through a multi-channel sequential valve needle hot runner system.

[0039] Specifically, the mold adopts an injection mold with rapid temperature change (RHCM) capability, such as heating with high-temperature steam or heat transfer oil and cooling with circulating cooling water. The hot runner system adopts a multi-channel sequential valve needle (SVG) hot runner system, in which the main injection unit is connected to the main runner gate for filling the cavity; the auxiliary injection unit is connected to an independent compensation gate with the gate position set in the preset thick-walled area of ​​the vacuum cleaner injection part body (such as the root of the handle, the area with dense reinforcing ribs).

[0040] To verify the innovation and advantages of this invention in terms of strength and toughness (internal stress and impact resistance), a comparative example is prepared to be compared with this embodiment. The comparative example and embodiment are as follows:

[0041] Comparative Example 1: Compared with Example 1, the difference is that a conventional high-pressure injection molding process is used. Specifically, the RHCM preheating, zero holding pressure switching and rapid cooling in step S1 are not used, nor is closed-loop compensation injection performed. Instead, a constant mold temperature (e.g., 80 °C) is used, and after the main thermoplastic material is filled, a high holding pressure of 50~80 MPa is applied and maintained for 5~10 s. All other aspects are the same.

[0042] Comparative Example 2: Compared with Example 1, the difference is that zero holding pressure was performed but shrinkage compensation was not performed. Specifically, step S1 (RHCM preheating, high-speed injection, zero holding pressure switching, rapid cooling) was fully performed. However, after step S1 was completed, subsequent monitoring and compensation injection were not performed, and the final curing and demolding were directly performed. The rest were the same.

[0043] Comparative Example 3: Compared to Example 1, the difference is that open-loop (timing) compensation is used instead of closed-loop (pressure feedback) compensation; specifically, it is not based on a pressure sensor ( Instead of triggering a compensation injection, the auxiliary injection unit performs a one-time open-loop compensation injection according to a preset fixed injection volume 0.5 seconds after the main thermoplastic material is filled, without using... The signal stops; everything else remains the same.

[0044] Comparative Example 4: Compared with Example 1, the difference is that a gradient compensation system was not used. Specifically, for all the preset thick-walled areas and the second thick-walled areas of the vacuum cleaner injection molded part body, the same compensating agent masterbatch was used (for example, only the second compensating agent B2, i.e., the medium-temperature fast-release type was used), and the rest were the same.

[0045] Comparative Example 5: Compared with Example 1, the difference is that the content of chemical foaming agent in the compensator masterbatch is lower than the lower limit defined by the present invention. Specifically, in the first compensator (B1) and the second compensator (B2) used, the mass fraction of chemical foaming agent (CBA) is 1% (lower than the range of 5% to 15%), and the rest are the same.

[0046] Comparative Example 6: Compared with Example 1, the difference is that the content of chemical foaming agent in the compensator masterbatch is higher than the upper limit specified in this invention. Specifically, in the first compensator (B1) and the second compensator (B2) used, the mass fraction of chemical foaming agent (CBA) is 25% (higher than the range of 5% to 15%), and the rest are the same.

[0047] Comparative Example 7: Compared with Example 1, the difference is that a conventional microfoaming process is used instead of the post-compensation process of the present invention. Specifically, the chemical foaming agent (CBA) is premixed with the main thermoplastic material (PC / ABS) and injected in one go by the main injection unit; no auxiliary injection unit is used and no closed-loop compensation is performed, but everything else is the same.

[0048] The following are the specific experimental instructions and data tables for evaluating mechanical properties (strength and toughness):

[0049] 1. Take 10 vacuum cleaner injection molded parts each from Example 1 and Comparative Examples 1-7.

[0050] Sample pretreatment: All test samples were conditioned for at least 24 hours in a standard laboratory environment at 23±2 ℃ and 50±5%RH (relative humidity).

[0051] Testing equipment: a dedicated drop test machine, with the impact surface being a steel plate (or standard concrete floor) with a thickness of not less than 20mm.

[0052] Test procedure: First, fix the test sample on the clamping arm of the drop tester, adjust the clamping posture so that the "handle end" of the sample faces the impact surface, simulate the posture most susceptible to impact during use, set the drop height to 1.0m, release the sample and let it fall freely to impact the impact surface, each sample is dropped only once.

[0053] Results Record: After the drop test, visually inspect the samples. If there are no visible cracks, breaks or fragments, and the samples show any form of cracks, breaks or component separation, count the number of "pass" samples in each group (10 pieces) and record it as the "pass rate" (X / 10).

[0054] 2. Experimental Procedure: Impact Strength Test of Izod Cantilever Beam with Weld Line Notch

[0055] Test standard: Refer to ASTM D256 (Standard Test Method for Impact Strength of Plastic Izod Pendulum).

[0056] Sample preparation: Standard impact test specimens were cut from the vacuum cleaner injection molded parts prepared in Example 1 and Comparative Examples 1-7 along the main weld line area (i.e. the final fusion point of the melt). Five specimens were prepared for each group. Precision wire cutting or CNC machining was used to ensure that the weld line was accurately located on the central axis of the specimen. A standard A-type notch was machined at the center of the weld line of the specimen.

[0057] Sample pretreatment: All cut and notched specimens were conditioned for at least 24 hours in a standard laboratory environment at 23±2℃ and 50±5%RH.

[0058] Testing equipment: Izod pendulum impact testing machine.

[0059] Test procedure: Clamp the specimen vertically in the vise of the impact testing machine, ensuring that the notched surface faces the impact direction of the pendulum. Release the pendulum to impact and break the specimen. Read and record the energy consumed by the pendulum to break the specimen.

[0060] Results Recording: Record the energy absorbed in each impact, divide the energy value by the thickness of the notch in the specimen (i.e., the specimen width), calculate and record the impact strength in J / m (joules per meter). Record 5 data points for each group. The experimental data are shown in the table below:

[0061] Test group Whole machine drop simulation test (1.0m height) (Number of passes / Total number of tests) Izod impact strength of weld line notch (J / m) (n=5, record data points) Example 1 9 / 10 48.2, 51.5, 49.9, 53.0, 50.7 Comparative Example 1 (Traditional High Voltage) 1 / 10 15.1, 12.9, 14.4, 16.0, 13.8 Comparative Example 2 (Zero Holding Pressure, No Compensation) 3 / 10 22.5, 20.1, 21.7, 19.9, 23.0 Comparative Example 3 (Open-Loop Compensation) 5 / 10 25.8, 38.1, 29.9, 35.4, 30.7 Comparative Example 4 (Non-gradient compensation) 6 / 10 35.6, 38.2, 36.1, 39.0, 37.5 Comparative Example 5 (Insufficient Compensation) 4 / 10 24.3, 26.8, 25.1, 23.9, 26.0 Comparative Example 6 (Excessive Compensation) 4 / 10 28.9, 31.5, 30.1, 27.7, 29.4 Comparative Example 7 (Traditional Microfoaming) 5 / 10 30.5, 28.8, 31.9, 32.5, 30.1

[0062] (Strength and Toughness) Assessment Results Table

[0063] Based on the mechanical performance evaluation results in the table above, the inherent mechanism of the process of this invention in achieving "strength and toughness" can be analyzed. The data of Comparative Example 1 (traditional high-pressure holding pressure) shows that the high residual internal stress locked under high holding pressure (e.g., 50~80MPa) is the root cause of the extreme brittleness of the vacuum cleaner body, manifested as an extremely low drop pass rate (1 / 10) and a weld line impact strength of only about 14J / m. In contrast, the process step (S1) used in Example 1, which utilizes the high-temperature mold wall of RHCM and high-speed injection to ensure weld line strength, and immediately switches to a "zero holding pressure" state for rapid cooling after filling, this "zero-stress skin curing" mechanism allows the plastic shell and weld line to be formed in a relaxed molecular chain state, fundamentally eliminating high residual stress. Therefore, the drop pass rate (9 / 10) and weld line impact strength (about 50J / m) of Example 1 are much higher than those of Comparative Example 1, proving that this low-stress molding step is the basis for achieving "strength and toughness".

[0064] Data from Comparative Example 2 (zero holding pressure but no compensation) shows that although high stress was avoided, the lack of subsequent pressure compensation to counteract the cooling shrinkage of the molten core led to defects (such as voids or shrinkage) inside the plastic part, resulting in a low drop pass rate (3 / 10) and impact strength (approximately 21 J / m). The closed-loop compensation step introduced in Example 1, which involves injecting compensating agent masterbatch into the molten core after the low-stress skin has solidified, actively counteracts the cooling shrinkage of the molten core through the "internal compensation pressure" generated by chemical foaming, ensuring the internal density of the part. This decoupling mechanism makes the performance of Example 1 far superior to that of Comparative Example 2, and also superior to that of Comparative Example 7 (traditional microfoaming), because the post-compensation of this invention avoids the damage of the foaming agent to the Class A surface and weld line strength.

[0065] Furthermore, the accuracy of compensation is crucial for maintaining a low-stress state. Data from Comparative Example 3 (open-loop compensation) and Comparative Example 4 (non-gradient compensation) show that inaccurate (timing) or mismatched (non-gradient) compensation results in toughness (5 / 10-6 / 10 drop pass rate) inferior to Example 1. This indicates that an incorrect compensation strategy can introduce new local stresses or lead to insufficient compensation. Data from Comparative Example 5 (insufficient foaming agent content) and Comparative Example 6 (excessive foaming agent content) (both with a 4 / 10 drop pass rate) further confirm this: insufficient compensation cannot solve the shrinkage problem (results are close to Comparative Example 2), while excessive compensation will generate internal expansion stress in the opposite direction. The closed-loop control used in Example 1 (based on...) trigger, The synergistic effect of the stop and gradient materials (B1 / B2) ensures that the compensating pressure can accurately offset the shrinkage without exceeding the threshold of introducing new stress, thereby maximizing the retention of the low stress advantage obtained in step S1 and ultimately achieving the goal of strength and toughness.

[0066] In summary, this invention provides a manufacturing process for a high-toughness vacuum cleaner injection molded part. By immediately switching to zero or near-zero holding pressure for skin curing after the main thermoplastic material is filled, the vacuum cleaner injection molded part can be formed in a relaxed molecular chain state, greatly reducing the brittleness of the part and significantly improving the overall toughness and environmental stress cracking (ESCR) resistance of the vacuum cleaner injection molded part. Furthermore, a high-gloss cured skin layer is obtained by using a rapid temperature change mold and high-speed injection. Subsequently, without applying external high pressure, compensating agent masterbatch is injected into the internal molten core. The internal compensating pressure generated by its activation foaming is used to offset cooling shrinkage, so that the vacuum cleaner injection molded part achieves a perfect Grade A high-gloss appearance while completely eliminating surface shrinkage defects in thick-walled areas.

[0067] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A manufacturing process for a high-toughness vacuum cleaner injection molded part body, characterized in that, Includes the following steps: S1. First, inject the main thermoplastic material into the cavity of the preheated rapid temperature change mold. After the main thermoplastic material is filled, switch to zero pressure or near-zero pressure state and simultaneously cool the rapid temperature change mold quickly, thereby forming a low-stress cured skin layer on the outer surface of the vacuum cleaner injection molded part body, and forming a molten core inside the cured skin layer. S2. By using a pressure sensor installed in the cavity, the cavity pressure drop caused by the cooling and shrinkage of the molten core is monitored in real time; when the cavity pressure drops to a preset compensation trigger pressure lower limit, a compensating agent masterbatch containing a chemical foaming agent is injected into the molten core. The chemical foaming agent is activated and foamed by heating to generate internal compensation pressure, thereby offsetting the cooling and shrinkage of the molten core. S3. When the cavity pressure is detected to rise to the preset compensation stop pressure limit, stop injecting the compensation agent masterbatch. After compensation in all areas has been completed (according to closed-loop feedback), the plastic part continues to cool in the mold until the near-zero stress skin layer and the internal micro-foaming compensation core layer are completely solidified. Finally, open the mold and eject the processed vacuum cleaner injection molded part.

2. The manufacturing process of a high-toughness vacuum cleaner injection molded part body according to claim 1, characterized in that, The process of injecting the main thermoplastic material into the cavity of a preheated rapid temperature-change mold specifically involves: preheating the cavity of the rapid temperature-change mold to a temperature of 120~150℃; and increasing the flow rate to 100~300mm / s. The main thermoplastic material is injected at high speed.

3. The manufacturing process of a high-toughness vacuum cleaner injection molded part body according to claim 1, characterized in that, The switching to zero or near-zero holding pressure state, and simultaneously rapidly cooling the rapid temperature change mold, specifically involves: switching the injection pressure to a zero or near-zero holding pressure state of 0~1.0MPa; and simultaneously cooling the cavity of the rapid temperature change mold to a temperature of 60~90℃.

4. The manufacturing process of a tough vacuum cleaner injection molded part body according to claim 1, characterized in that, The pressure thresholds used for real-time monitoring, injection, and stopping injection are set as follows: the lower limit of the compensation trigger pressure is in the range of 0.5~2.0MPa; the upper limit of the compensation stop pressure is in the range of 1.0~5.0MPa, and the upper limit of the compensation stop pressure is greater than the lower limit of the compensation trigger pressure.

5. The manufacturing process of a high-toughness vacuum cleaner injection molded part body according to claim 1, characterized in that, The main thermoplastic material is a PC / ABS alloy; the substrate of the compensator masterbatch is the same as or compatible with the main thermoplastic material.

6. The manufacturing process of a tough vacuum cleaner injection molded part body according to claim 5, characterized in that, In the compensator masterbatch, the mass fraction of the chemical foaming agent is 5% to 15%.

7. The manufacturing process of a high-toughness vacuum cleaner injection molded part body according to claim 5, characterized in that, The compensator masterbatch includes at least two types: a first compensator containing a high-temperature slow-release chemical foaming agent with an activation temperature range of 190~220 ℃; and a second compensator containing a medium-temperature rapid-release chemical foaming agent with an activation temperature range of 160~190 ℃.

8. The manufacturing process of a high-toughness vacuum cleaner injection molded part body according to claim 7, characterized in that, The injection of compensating agent masterbatch containing chemical foaming agent into the molten core is performed in sections and asynchronously, wherein: the first compensating agent is injected into the preset thickest wall area of ​​the vacuum cleaner injection molded part body; and the second compensating agent is injected into the preset second thickest wall area of ​​the vacuum cleaner injection molded part body.

9. The manufacturing process of a high-toughness vacuum cleaner injection molded part body according to claim 8, characterized in that, The process parameters for injecting the compensator masterbatch containing chemical foaming agent into the molten core are as follows: the injection temperature is set to 210~240 ℃, and the injection speed is 10~50 mm / s.

10. The manufacturing process of a tough vacuum cleaner injection molded part body according to claim 1, characterized in that, The process is performed by a dual-injection molding machine, wherein the main injection unit is used to inject the main thermoplastic material and the auxiliary injection unit is used to inject the compensator masterbatch; and the main thermoplastic material and the compensator masterbatch are respectively delivered to different gates of the cavity through a multi-channel sequential valve needle hot runner system.

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