Injection mold device and injection molding method for inner side buckle position type precise plastic product

Abstract

The invention belongs to the technical field of injection molding, and discloses an injection mold device and an injection molding method.The injection mold device comprises a rear mold part, a first-pulling part and an ejection system.The injection molding method mainly comprises the steps that a first-pulling supporting plate is static in the whole process, and the rear mold part is guided by a guide column to move front and back relatively; the template opening control block is provided with a 50 + / -5-degree guide inclined plane, the small elastic block is provided with a matched inclined plane, and the small elastic block is mechanically separated from the ejection block through inclined plane contact. Aiming at demolding operation in manufacturing of a small-size precise plastic product with a plurality of inner side buckle positions and an inverted buckle groove, a complete technical system of'equipment structure-material type selection-parameter design-method steps' is mainly constructed, and comprehensive optimization from hardware to a process is carried out; the demolding problem of a small-size plastic product with an inner side buckling position and an inverted buckling groove in the buckling position demolding direction is solved, the structure is compact and reliable, the cost is low, the precision is high, and the application range is wide.

Description

Technical Field

[0001] This invention relates to the field of plastic mold manufacturing technology, specifically to an injection mold device and injection method for precision plastic products with internal snap-fit ​​features. Background Technology

[0002] In the field of injection mold technology, for a class of plastic products with internal snap-fit ​​parts, especially small-sized precision plastic products, such as automotive interior functional parts, internal snap-fit ​​parts for OA printers, etc. (see appendix) Figure 10 Due to its internal undercut structure and the high requirements for space and precision, demolding has always been a technical challenge. Currently, there is a prevailing industry perception that "demolding with internal undercuts must use sliding / sloping ejectors + external drive." Existing demolding methods mainly include: 1. Slide core pulling structure: such as the secondary slide core pulling and unhooking structure disclosed in CN 220261852 U, requires a complex transmission mechanism and drive equipment. It has a complex structure, high cost, and large space occupation, and is not suitable for small-sized products.

[0003] 2. Inclined ejector mechanism: such as the inclined ejector spring linkage mechanism disclosed in CN 113815204 A, requires external drive such as a stepper motor, has a complex structure, poor reliability, and is prone to generating clamping lines on the surface of plastic products, affecting the appearance quality of the products.

[0004] 3. Forced release structure: such as the internal forced release mold disclosed in CN 204997889 U, which relies on spring force to achieve demolding. The spring force is difficult to control precisely, which can easily lead to product deformation or damage and has poor reliability.

[0005] 4. Front mold core pulling mechanism: such as the front mold inner core pulling mechanism disclosed in CN 108656470, is mainly applicable to the outer snap-fit ​​of the front mold, but not applicable to the demolding of the inner snap-fit ​​of the rear mold.

[0006] These existing technical solutions all have their own shortcomings, including: complex structure, need for external power, poor reliability, high cost, and unsuitability for precision small-sized products, thus failing to meet industry needs. Summary of the Invention

[0007] The technical problem to be solved by the present invention is to provide an injection mold device and injection method for small-sized precision plastic products with multiple internal snap-fits and undercut grooves in the demolding direction of the snap-fits. Through the coordinated improvement of the mold and process, the structure is compact, the reliability is high, the cost is low, and no external power is required to meet the needs of the industry.

[0008] This invention provides the following technical solution: An injection mold device for precision plastic products with internal snap-fit ​​features, comprising: a rear mold portion, a pre-extraction portion, and an ejection system; The rear mold part includes a rear mold core located on the B plate by positioning pins, a rear mold insert embedded in the rear mold core by H7 / m6 transition fit, guide pins vertically installed at the four corners of the B plate, and balance blocks symmetrically distributed on both sides of the rear mold core. The first-draw section includes a first-draw support plate fixed to the moving mold fixing plate, a first-draw insert and a template opening control block fixedly assembled to the first-draw support plate, a small spring block elastically installed on the B plate by a spring, and a pressure block that limits the movement range of the small spring block. The ejection system includes a flat ejector pin and an ejector block fixed to the ejector plate, and an ejector plate pressure plate fastened to the bottom of the ejector plate; The first ejector plate remains stationary throughout the demolding process, while the rear mold part moves back and forth relative to the first ejector plate through the guide pillars. The template opening control block is provided with a guide slope with an angle of 50°±5°. The small elastic block is provided with a slope that matches the guide slope. When the ejector block pushes the small elastic block to contact the guide slope, the small elastic block slides inward along the slope to separate from the ejector block.

[0009] A method for injection molding precision plastic products with internal snap-fit ​​mechanisms, comprising the following steps, using the aforementioned injection mold device for demolding: Step S1: Separate the front and rear molds: After the plastic product is fully injection molded, the front mold and the rear mold are separated, and the plastic product remains in the rear mold part; Step S2: Core pulling action: The ejection system is activated, the ejector block pushes the small spring block, which drives the rear mold part to move forward along the guide post. The first insert moves backward relative to the rear mold part and disengages from the outer side of the plastic product's snap-fit. Step S3: Separation of small spring block: The small spring block contacts the 50° guide slope of the mold opening control block of the template, slides inward along the slope, and separates from the ejector block; Step S4 Strong Demolding Action: The flat ejector pins eject, and the snap-fit ​​parts of the plastic product first deform outward elastically, and then the whole thing moves forward to achieve complete demolding; Step S5 Reset: The ejection system is reset, and the rear mold part returns to its initial position.

[0010] Beneficial effects Compared with the prior art, the injection mold device for precision plastic products with internal snap-fitting mechanism of the present invention has the following advantages: 1. Deep Synergy Between Equipment and Method: This invention successfully solves the demolding problem of small-sized precision plastic products with internal snap-fit ​​parts and undercut grooves in the demolding direction by synergistically improving the injection mold device and demolding method. This breaks the inherent perception of the industry and fills the technical gap of traditional demolding methods in this field. The "first pull the support plate static + the mold moves relative to each other" and "sloping mechanical separation" structure of the mold equipment design corresponds one-to-one with the "first pull the core - separation - strong demolding" steps of the method, forming a closed-loop design with no redundant parts or steps, resulting in a compact structure and efficient process. 2. Compact and reliable structure: It adopts a pure mechanical structure, avoiding complex transmission components and control systems. It has a compact structure, high reliability, and long service life. It is a pure mechanical solution without external power. It relies entirely on the self-movement of mold opening / ejection, without the need for hydraulic systems, stepper motors, or other external drives. It solves the problems of "high energy consumption, complex maintenance, and response delay" of traditional technologies (energy consumption is reduced from 10kWh / hour to 5kWh / hour, and response time is reduced from 0.8-1.2 seconds to instant response).

[0011] 3. Fully parameterized and precise control: From the equipment's fit clearance, material hardness, and inclined plane angle, to the method's movement distance and deformation, a complete parameter system is formed to ensure a comprehensive improvement in demolding accuracy, consistency, and mold life; through the guiding effect of the guide pillars and precise relative motion control, the product's positioning accuracy and dimensional consistency are improved, significantly enhancing processing precision.

[0012] 4. Significantly reduced costs: The mold making process and procedures have been simplified, reducing the difficulty and cost of mold making, while also reducing reliance on external equipment and lowering energy consumption and maintenance costs; 5. High versatility: By changing the pre-draw insert (three-section / four-section / five-section), it can adapt to a variety of small-sized products (diameter 10-50mm) such as round, square, and irregular shapes, covering multiple scenarios such as automotive interior parts and printer clips, significantly expanding the application range of plastic molds. It can be used for various small-sized plastic products with internal snap-fit ​​positions and undercut grooves in the demolding direction of the snap-fit ​​positions. Attached Figure Description

[0013] Figure 1 is a three-dimensional structural diagram of the overall shape of the injection mold device according to an embodiment of the present invention; Figure 2 is a top view of the injection mold device according to an embodiment of the present invention; Figure 3 shows an embodiment of the present invention. Figure 2 Schematic diagram of the cross-sectional structure of AA; Figure 4 is a schematic diagram of the internal structure of the injection mold device according to an embodiment of the present invention; Figure 5 is a schematic diagram of the injection mold device in the separated state of the front and rear molds according to an embodiment of the present invention; Figure 6 is a schematic diagram of the state in which the first insert of the injection mold device of the present invention moves backward relative to the first insert and leaves space for the snap-fit ​​to move outward. Figure 7 is a schematic diagram of the injection mold device according to an embodiment of the present invention, showing the state of the flat ejector pin ejection and the outward deformation and movement of the plastic product fastener. Figure 8 is a schematic diagram of the state in which the flat ejector pin of the injection mold device according to an embodiment of the present invention continues to eject and the plastic product moves forward and separates from the rear mold structure; Figure 9 shows an embodiment of the present invention. Figure 7 A magnified schematic diagram of the partial structure of B in the diagram; Figure 10 is a schematic diagram of the main structure of an injection-molded precision plastic product with inner snap-fit ​​mechanism in an embodiment of the present invention.

[0014] In the diagram: 1. Plastic product; 2. First-release insert; 3. Rear mold core; 4. Guide pillar; 5. B plate; 6. First-release support plate; 7. Positioning pillar; 8. Balance block; 9. Rear mold insert; 10. Flat ejector pin; 11. Small spring block; 1101. Angled surface; 12. Spring; 13. Pressure block; 14. Template opening control block; 1401. Guide angled surface; 15. Ejector block; 16. Ejector plate; 17. Ejector plate pressure plate; 18. Undercut groove; 19. Clip. Detailed Implementation

[0015] The technical solutions of 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.

[0016] Basic Implementation See appendix Figure 1-10 The injection mold device for precision plastic products with internal snap-fit ​​provided in this embodiment of the invention includes a rear mold part, a pre-extraction part, and an ejection system. The relative movement between the pre-extraction part and the rear mold part enables the pre-extraction of the plastic product, and the ejection system then enables strong demolding of the plastic product. Specifically: The rear mold part includes a rear mold core 3 precisely located on the B plate 5 by positioning post 7, a rear mold insert 9 that is embedded in the rear mold core 3 by transition fit of H7 / m6, guide posts 4 vertically installed at the four corners of the B plate 5, and balance blocks 8 symmetrically distributed on both sides of the rear mold core 3. The first-draw section includes a first-draw support plate 6 fixed to the moving mold fixing plate, a first-draw insert 2 fixedly assembled to the first-draw support plate 6 and a template opening control block 14, a small spring block 11 elastically installed on the B plate 5 by a spring 12, and a pressure block 13 that limits the movement range of the small spring block 11. The ejection system includes a flat ejector pin 10 and an ejector block 15 fixed to the ejector pin plate 16, and an ejector plate pressure plate 17 fastened to the bottom of the ejector pin plate 16. The first ejector plate 6 remains stationary throughout the demolding process, while the rear mold part moves back and forth relative to the first ejector part through the guide post 4. The template opening control block 14 is provided with a guide slope 1401 with an angle of 50°±5°. The small spring block 11 is provided with a slope 1101 that matches the guide slope 1401. When the ejector block 15 pushes the small spring block 11 to contact the guide slope 1401, the small spring block 11 slides inward along the slope to separate from the ejector block 15.

[0017] In one specific embodiment, the first-draw insert 2 can adopt a three-segment arc structure, with a quantity of 3, evenly distributed along the circumference of the plastic product at 120°; the first-draw insert 2 is precisely fitted with the rear mold insert 9 and the rear mold insert hole, with the fitting gap controlled at 0.01-0.015mm.

[0018] In the second specific embodiment, the first-draw insert 2 adopts a four-segment square structure, and there are 4 of them, which are evenly distributed along the 90° perimeter of the plastic product. In the third specific embodiment, the first insert 2 adopts a five-segment irregular structure, with a quantity of 5, which are evenly distributed along the circumference of the plastic product at 72°.

[0019] The guide slope 1401 has an angle of 50° and a length of 18-20 mm; the matching slope of the small spring block 11 has a fit of ≥95% with the guide slope 1401, and the surface roughness Ra of the slope is ≤0.05 μm.

[0020] The top of the flat ejector pin 10 avoids the fastening area of ​​the plastic product and contacts the surface of the plastic product. The cross-sectional dimensions of the flat ejector pin 10 are 8×3mm. The initial engagement gap between the ejector block 15 and the small spring block 11 is 0.02-0.03 mm.

[0021] The movement distance of the rear mold part relative to the first drawing part is 8-10mm, and the movement speed is 8-12mm / s; combined with the angle parameter of 50°±5° of the guide slope, the sliding distance of the small spring block 11 along the guide slope 1401 is calculated to be 2.5-3.5mm, and the compression of the spring 12 during the sliding process is adapted to be 2-3mm. The rear mold part moves forward a distance of 8-10mm at a speed of 8-12mm / s; the first insert 2 moves backward relative to the rear mold part a distance that is the same as the distance the rear mold part moves forward.

[0022] The rear mold core 3 and the rear mold insert 9 are made of S136 hardened steel with a hardness of HRC45-48; the pre-drawing insert 2 is made of NAK80 pre-hardened steel with a hardness of HRC37-41, which is easy to replace when the mold wears out during mass production; the guide post 4 is made of SUJ2 bearing steel with a diameter of 20mm and a length of 120mm.

[0023] More specifically, the components, their positional relationships, coordination relationships, and interactions are as follows: 1. Rear mold section The rear mold portion includes a rear mold core 3, a rear mold insert 9, guide pillars 4, a B plate 5, positioning pillars 7, and balance blocks 8. The rear mold core 3 is fixedly mounted on the B plate 5 and precisely positioned by the positioning pillars 7. The rear mold insert 9 is embedded in the rear mold core 3, forming the inner snap-fit ​​shape of the plastic product 1 together with the first-draw insert 2. The guide pillars 4 are vertically mounted at the four corners of the B plate 5 for guiding the movement of the rear mold portion. The balance blocks 8 are symmetrically distributed on both sides of the rear mold core 3 for balancing the movement of the rear mold portion.

[0024] 2. Draw a portion first. The pre-extraction section includes a pre-extraction insert 2, a pre-extraction support plate 6, a small spring block 11, a spring 12, a pressure block 13, and a template opening control block 14. The pre-extraction insert 2 is fixedly installed on the pre-extraction support plate 6 and evenly distributed around the perimeter of the plastic product 1. The pre-extraction support plate 6 is fixedly installed on the mold's fixed mold plate and remains stationary throughout the demolding process. The small spring block 11 is elastically installed in plate B 5 via the spring 12 and can slide within the mounting holes of plate B 5. The pressure block 13 limits the movement range of the small spring block 11. The template opening control block 14 is fixedly installed on the pre-extraction support plate 6 of the mold and is used to control the movement of the small spring block 11.

[0025] 3. Ejection System The ejection system includes a flat ejector pin 10, an ejector block 15, an ejector plate 16, and an ejector plate pressure plate 17. The flat ejector pin 10 is fixedly installed on the ejector plate 16, and its top end contacts the plastic product 1. The ejector block 15 is fixedly installed on the ejector plate 16 and is used to push the small spring block 11. The ejector plate pressure plate 17 is installed at the bottom of the ejector plate 16 and is used to fix the ejector plate 16. In the injection mold device for precision plastic products with internal snap-fitting mechanism of the present invention, the motion relationship between the components is as follows: relative motion between the first extraction part and the rear mold part: The first ejector plate 6 is fixedly installed on the fixed mold plate of the mold by four M10 hexagon socket screws, and remains absolutely still and fixed throughout the demolding process. The first ejector insert 2 remains still along with the first ejector plate 6. The rear mold section, guided by the guide post 4, can move back and forth relative to the first part. When the rear mold moves forward, since the first pull plate 6 is fixed, the first pull insert 2 moves backward relative to the rear mold, disengaging from the outer snap-fit ​​of the plastic product 1, leaving space for the snap-fit ​​of the plastic product 1 to deform outward. The motion relationship between the small spring block and the ejected block: The small spring block 11 is held in its initial position by the action of the spring 12 and is in contact with the ejector block 15; When the ejector block 15 moves forward, it pushes the small spring block 11, which in turn drives the rear mold part to move forward. When the small spring block 11 contacts the 50° guide slope 1401 of the mold opening control block 14, it moves inward under the action of the slope of the mold opening control block 14 and separates from the ejector block 15. The relationship between the ejection system and the movement of the plastic product: The flat ejector pin 10 moves forward under the action of the ejector plate 16; After the flat ejector pin 10 contacts the plastic product 1, under the action of the ejection force, the buckle 19 of the plastic product 1 first elastically deforms outward, and the amount of deformation is controlled within the elastic limit of the material, and then the whole thing moves forward.

[0026] The injection molding method for precision plastic products with internal snap-fit ​​mechanisms provided in this embodiment uses the aforementioned injection mold device for demolding and includes the following steps: Step S1: Separate the front and rear molds: For precision plastic products with side snap-fit ​​parts 1 (see structure) Figure 10 After the overall injection molding is completed, the front and rear molds are separated, leaving the plastic product 1 in the rear mold part; After the plastic product 1 is injection molded, the injection molding machine drives the front mold and the rear mold to separate in preparation for demolding. At this time, the insert 2 is still in contact with the snap-fit ​​19 and the undercut groove 18 to prevent the plastic product 1 from moving with the front mold. Step S2 First core pulling action: The ejection system is activated, the ejector block 15 pushes the small spring block 11, which drives the rear mold part to move forward along the guide post 4. The insert 2 is pulled out and moves backward relative to the rear mold part, disengaging from the outside of the plastic product 1 snap-fit, leaving space for the product snap-fit ​​to deform outward. The rear mold part moves forward a distance of 8-10mm at a speed of 8-12mm / s. After the ejection system is started, the ejector plate 16 moves forward, and the ejector block 15 pushes the small spring block 11 to drive the rear mold part to move forward along the guide post 4. At this time, since the first ejector plate 6 is fixed, the first ejector insert 2 moves backward relative to the rear mold part and gradually gets away from the outside of the snap-on position of the plastic product 1, which can leave space for the snap-on position 19 of the plastic product 1 to move outward for demolding. Step S3: Separation of the small spring block: The small spring block 11 contacts the 50° guide slope 1401 of the mold opening control block 14, slides inward along the slope, and separates from the ejector block 15; when the rear mold part moves forward to the position where the slope 1101 of the small spring block 11 contacts the guide slope 1401 of the mold opening control block 14, it slides inward under the action of the guide slope 1401 of the mold opening control block 14, and separates from the ejector block 15; the distance that the small spring block 11 moves inward is 2-3mm; In this step, when the rear mold part moves forward to the predetermined position, the small spring block 11 contacts the 50° guide slope 1401 of the mold opening control block 14. Under the action of the slope of the mold opening control block 14, the small spring block 11 overcomes the elastic force of the spring 12 and moves inward, separating from the ejector block 15. At this time, the ejection system continues to eject, but the rear mold part no longer moves forward.

[0027] Step S4 Strong demolding action: The flat ejector pin 10 continues to eject, and the snap-fit ​​of the plastic product 1 first elastically deforms outward, then moves forward as a whole, finally causing the plastic product 1 to detach from the rear mold and achieve complete demolding; the amount of outward elastic deformation of the snap-fit ​​of the plastic product 1 is controlled to be 0.3-0.8mm. In this step, the ejector plate 16 continues to move forward. Under the ejection force of the flat ejector pin 10, the snap-fit ​​part 19 of product 1 first deforms outward elastically, and the amount of deformation is controlled within the elastic limit of the material. Then, the whole thing moves forward, and finally the plastic product 1 is separated from the rear mold.

[0028] Step S5 Reset: After demolding, the robot arm removes the plastic product 1, the ejection system resets, and the rear mold returns to its initial position (mold closing position), completing the entire injection molding cycle of the product and preparing for the next injection molding demolding operation.

[0029] The relative motion principle of this invention is as follows: Core pulling is achieved by fixing the first part while the second part moves, avoiding the complex transmission mechanism required by traditional sliding core pulling structures; Pure mechanical control is employed: the separation of the second part from the ejection system is achieved using a purely mechanical structure of a template mold opening control block and small spring blocks, eliminating the need for a complex control system; Step-by-step demolding is performed: the step-by-step demolding method of first pulling the core and then forcefully demolding solves the demolding problem for products with undercut grooves in the demolding direction; The mold device has a compact structure: the overall structure is compact with high space utilization, suitable for demolding small-sized products; Reliable guidance: the guiding effect of guide pillars ensures the smoothness and accuracy of the movement of the second part.

[0030] The following describes the process in detail with reference to several specific embodiments.

[0031] Example 1 The injection mold device and injection method for precision plastic products with internal snap-fit ​​provided in this embodiment adopt a three-section arc-shaped pre-extraction insert structure for demolding of plastic automotive interior functional parts, which is a further specific application based on the basic embodiment.

[0032] In this embodiment, the pre-drawing insert adopts a three-segment arc structure, with three inserts evenly distributed along the circumference of the product at 120°. The pre-drawing insert precisely fits with the rear mold insert and the rear mold insert hole, with the fitting gap controlled within 0.01-0.015mm.

[0033] See appendix Figure 10 The plastic product is a cylindrical automotive interior functional component with a diameter of 30mm. It has three inner snap-fit ​​positions 19 around its circumference, and there is a 1.0mm deep undercut groove 18 in the demolding direction of the snap-fit ​​positions. The product material is PC+ABS alloy, and the shrinkage rate is 1.005.

[0034] The structural components of an injection mold assembly include: Rear mold core 3: NAK80 pre-hardened steel, HRC37-41, 140×105×50mm, center cavity diameter 30mm; Rear mold insert 9: NAK80 pre-hardened steel, 30×15×12mm, quantity 3, evenly distributed at 120°; Guide post 4: SUJ2 bearing steel, diameter 20mm, length 120mm, roundness tolerance ≤0.001mm; Positioning pin 7: SUJ2 bearing steel, diameter 10mm, length 30mm, fit accuracy H7 / r6; Plate B 5: S50C carbon steel, 140×105×50mm, parallelism tolerance ≤0.01mm; Balance weight 8: S50C carbon steel, 20×20×20mm, quantity 2; Pre-extraction section: Pre-extraction insert 2 adopts a three-segment arc structure, with a quantity of 3, evenly distributed along the circumference of the product at 120°, and its inner forming surface is completely fitted with the buckle 19 and undercut groove 18 of product 1; Pre-extraction support plate 6 is made of S50C carbon steel with a thickness of 20mm; Small spring block 11 is made of hard alloy material with a surface hardness of HRC55-58; Template opening control block 14 has a 50° guide slope 1401; Ejection system: Flat ejector pin 10 is made of SKD61 hot work mold steel, with a rectangular cross section, a size of 8×3mm, and a quantity of 6; Ejector block 15 is made of S50C carbon steel with a size of 20×15×30mm. The main demolding process after injection molding, based on the basic embodiment, also includes: When the ejection system is activated, the ejector block 15 pushes the small spring block 11, causing the rear mold part to move forward by 3mm. The insert 2 moves backward relative to the ejector block, and its protruding part comes out of the undercut groove 18. The small spring block 11 contacts the 50° guide slope 1401 of the mold opening control block 14 of the template, slides inward by 2mm, and separates from the ejector block 15. The flat ejector pin 10 ejects, and under the action of the ejection force, the snap part 19 of the product 1 first elastically deforms outward by 1.0mm, and then moves forward as a whole.

[0035] This embodiment features precise matching, ensuring that each pre-extracted insert corresponds precisely to an inner snap-fit ​​position, guaranteeing accurate demolding. The three-section design improves structural strength and stability, extending the mold's lifespan from the traditional 250,000 cycles to over 500,000 cycles. The relatively simple arc-shaped structure facilitates processing and manufacturing, reducing manufacturing costs by 30%. The yield rate of produced plastic products can reach 99.5%. Production efficiency is increased by more than 20% compared to existing technologies. Positioning accuracy can reach ±0.02mm. The undercut groove 18 of the plastic product is scratch-free, and the snap-fit ​​position 19 retains 96% of its strength.

[0036] Example 2 This embodiment specifically provides an injection mold device and injection method for producing internal fasteners for Class A printers. Based on Embodiment 1, the difference is that a four-segment square pre-draw insert structure is adopted. The plastic product is an internal fastener for Class A printers. The overall outline is square, with dimensions of 40×40×20mm. It has four inner fastening positions 19, and there are undercut grooves 18 with a depth of 0.8mm in the demolding direction of the fastening positions. The product material is POM, and the shrinkage rate is 1.02%.

[0037] The main structural components of the injection mold device are: Rear mold section: The rear mold core 3 is made of S136 stainless steel with a hardness of HRC48-52 and external dimensions of 160×160×60mm; the rear mold insert 9 is made of the same material and has dimensions of 40×10×15mm; the guide post 4 is made of SUJ2 bearing steel with a diameter of 25mm and a length of 150mm; Pre-draw section: The pre-draw insert 2 adopts a four-segment structure, with 4 pieces evenly distributed around the product circumference at 90°, and its inner forming surface is completely fitted with the snap-fit ​​19 and undercut groove 18 of the product 1; the pre-draw support plate 6 is made of S50C carbon steel with a thickness of 25mm; the small spring block 11 is made of SKD11 mold steel with a surface hardness of HRC58-62; the template opening control block 14 has a 50° guide slope 1401; Ejection system: The flat ejector pin 10 is made of SKH51 high-speed steel, with a rectangular cross section, a size of 10×4mm, and a quantity of 8; the ejector block 15 is made of S50C carbon steel, with a size of 25×20×35mm. The main demolding process after injection molding, based on the basic embodiment, also includes: When the ejection system is activated, the ejector block 15 pushes the small spring block 11, causing the rear mold part to move forward by 4mm. The insert 2 moves backward relative to the ejector block, and its protruding part comes out of the undercut groove 18. The small spring block 11 contacts the 50° inclined surface of the mold opening control block 14 of the template and moves inward by 2.5mm, separating from the ejector block 15. The flat ejector pin 10 ejects, and the snap-fit ​​part 19 of product 1 first elastically deforms outward by 0.8mm, and then moves forward as a whole. This embodiment is designed for square products. The pre-draw inserts adopt a four-segment square structure, with four inserts evenly distributed along the 90° circumference of the product. The inner molding surface of the pre-draw inserts completely fits the product's snap-fit ​​positions and undercut grooves. It has the following advantages: 1. Wide applicability, suitable for products of various shapes such as square and rectangular; 2. Good demolding effect, the four-segment structure can better adapt to the inner snap-fit ​​distribution of square products; 3. Stable structure, the square structure has better structural stability and is not easily deformed.

[0038] The plastic product qualification rate of this embodiment can reach over 99%, the production efficiency can be increased by 20%, the mold service life can reach over 400,000 times, the positioning accuracy reaches ±0.03mm, the undercut groove 18 is free of scratches, and the snap-fit ​​19 has a strength retention rate of 95%.

[0039] Example 3 This embodiment specifically provides an injection mold device and injection method for producing irregularly shaped plastic products. Based on Embodiments 1 and 2, it adopts a five-segment irregularly shaped pre-drawing insert structure, with a quantity of 5 inserts evenly distributed along the circumference of the product at 72°. The specific pre-drawing inserts can be adjusted according to the actual shape of the product, supporting various customized designs.

[0040] This embodiment can adapt to the inner fastener distribution of various irregularly shaped products; it has excellent demolding effect, and the five-segment structure can better wrap the inner fastener of irregularly shaped products; it has strong versatility, and through the customized design of the pre-extracted inserts, it can be applied to products of various complex shapes.

[0041] This invention application further tested the structural reliability and service life of the injection mold device to verify the performance changes of the mold during long-term use. The specific solution is as follows: (a) Test conditions Injection molding machine model: 100T electric injection molding machine; Product material: PC (polycarbonate, shrinkage rate 1.004%). Product dimensions: Diameter 30mm, Height 25mm; Fastening force: 85-95N (design requirement 80-100N); Demolding force: 120-150N (design requirement ≤200N); Test environment: Temperature 25±2°C, Humidity 50±10%; Testing cycle: Continuous testing, 24 hours a day, 7 days a week.

[0042] (II) Testing Items Dimensional accuracy: The tolerance requirement for critical dimensions of the product is ±0.02mm; Motion accuracy: The motion accuracy of the rear mold section is required to be ±0.01mm; Surface roughness: The surface roughness of the product must be Ra 0.8 μm; Parts wear: Wear condition of key components; Reliability: Failure conditions during continuous production.

[0043] (iii) Testing equipment Coordinate measuring machine: accuracy ±0.001mm, used for measuring product dimensional accuracy; Surface roughness meter: accuracy ±0.001μm, used to measure surface roughness; Universal testing machine: accuracy ±0.1N, used to measure snap-fit ​​force and demolding force; Roundness tester: accuracy ±0.0001mm, used to measure the roundness of guide posts; Vibration monitor: Used to monitor vibration during mold operation; Temperature monitor: Used to monitor changes in mold temperature.

[0044] (iv) Test Results 1. Results of 300,000 tests Dimensional accuracy: ±0.025mm (meets requirements); Surface roughness: Ra0.9μm (meets requirements); Motion accuracy: ±0.015mm (meets requirements); Part wear: Wear is present. The wear of the insert is 0.002mm and the wear of the guide post is 0.001mm, which are still within the allowable range. Reliability: Fault-free, continuous production of 300,000 cycles without downtime.

[0045] 2. Results of 400,000 tests Dimensional accuracy: ±0.028mm (meets requirements); Surface roughness: Ra1.0μm (meets requirements); Motion accuracy: ±0.018mm (meets requirements); Parts wear: Significant wear. The wear of the insert is 0.003mm and the wear of the guide post is 0.002mm. It is recommended to replace the wear parts after 500,000 cycles. Reliability: Fault-free, continuous production of 400,000 cycles without downtime.

[0046] 3. Results of 500,000 tests Dimensional accuracy: ±0.03mm (meets requirements); Surface roughness: Ra1.2μm (meets requirements); Motion accuracy: ±0.02mm (meets requirements); Parts wear: Severe wear, the wear of the insert is 0.005mm and the wear of the guide post is 0.003mm, and the vulnerable parts need to be replaced; Reliability: Fault-free, continuous production of 500,000 cycles without downtime.

[0047] Therefore, through 500,000 long-term reliability tests, it has been verified that the injection mold device for precision plastic products with internal snap-fit ​​provided in the above embodiments of the present invention has good reliability and service life. The mold device can still maintain good working performance after 500,000 cycles, the wear of key components is within the allowable range, the product quality is stable, and it can fully meet the requirements of mass production.

[0048] The injection mold device and injection method provided by this invention have been tested in actual production under confidential conditions, verifying that they can be widely used for products with a diameter of 10-50mm, filling the gap in demolding technology for small-sized products with internal snap-fits. They are applicable to various engineering plastics such as PC, ABS, PEEK, and POM, and can handle plastic products with 3-6 internal snap-fits, successfully demolding undercut grooves with a depth of 0.5-1.5mm.

[0049] In summary, the embodiments of the present invention focus on constructing a complete technical system encompassing "equipment structure, material selection, parameter design, and method steps," and have comprehensively optimized from hardware to process. The injection mold device mainly consists of a rear mold section, a pre-extraction section, and an ejection system. The pre-extraction support plate remains stationary throughout the process, while the rear mold section achieves relative forward and backward movement through guide pillars. The mold opening control block of the template is equipped with a 50±5° guide slope, and the small spring block is equipped with a matching slope. Mechanical separation from the ejection block is achieved through the contact of the slopes. This successfully solves the demolding problem of small-sized plastic products with internal snap-fits and undercut grooves in the demolding direction. It has advantages such as compact structure, reliable operation, low cost, high precision, and wide application range. It can significantly improve product quality and production efficiency, reduce production costs, and has significant practical value and broad application prospects.

[0050] 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. An injection mold device for a precision plastic product with an inner side buckle, characterized in that, It comprises: a back mold part, a first extraction part, and an ejection system; the back mold part comprises a back mold core (3) precisely positioned on the B plate (5) through positioning columns (7), a back mold insert (9) embedded in the back mold core (3), guide columns (4) vertically installed on the four corners of the B plate (5), and balance blocks (8) symmetrically distributed on both sides of the back mold core (3); the first extraction part comprises a first extraction support plate (6) fixed on the moving mold fixed plate, a first extraction insert (2) fixedly assembled on the first extraction support plate (6), a mold plate opening control block (14), a small elastic block (11) elastically installed on the B plate (5) through a spring (12), and a pressing block (13) limiting the movement range of the small elastic block (11); the ejection system comprises flat ejector pins (10) and ejection blocks (15) fixed on the ejector pin plate (16), and an ejector pin plate pressing plate (17) tightly fixed on the bottom of the ejector pin plate (16); the first extraction support plate (6) remains stationary during the whole demolding process, and the back mold part moves forward and backward relative to the first extraction part through the guide columns (4); the mold plate opening control block (14) is provided with a guide inclined surface (1401) with an angle of 50°±5°, and the small elastic block (11) is provided with a matching inclined surface (1101) matching the guide inclined surface (1401), when the ejection block (15) pushes the small elastic block (11) to contact the guide inclined surface (1401), the small elastic block (11) slides inwards along the inclined surface, realizing the separation from the ejection block (15).

2. The injection mold apparatus for a precision plastic product with an inner side buckle as claimed in claim 1, wherein The first extraction insert (2) adopts a three-section arc structure, the number is 3, and is uniformly distributed along the 120° of the plastic product circle; the first extraction insert (2) is accurately fitted with the back mold insert (9) and the back mold insert hole.

3. The injection mold apparatus for the inner side buckle type precision plastic product according to claim 1, wherein, The first extraction insert (2) adopts a four-section square structure, the number is 4, and is uniformly distributed along the 90° of the plastic product circle; or the first extraction insert (2) adopts a five-section special-shaped structure, the number is 5, and is uniformly distributed along the 72° of the plastic product circle.

4. The injection mold apparatus for the inner side buckle type precision plastic product according to claim 1, wherein, The angle of the guide inclined surface (1401) is 50°, and the length of the inclined surface is 18-20mm; the matching degree of the matching inclined surface of the small elastic block (11) and the guide inclined surface (1401) is ≥95%, and the surface roughness Ra of the inclined surface is ≤0.05μm.

5. The injection mold apparatus for a medial side post precision plastic product of claim 1, wherein, The top end of the flat ejector pin (10) avoids the buckle position area of the plastic product and contacts the surface of the plastic product, and the cross-sectional size of the flat ejector pin (10) is 8×3mm.

6. The injection mold apparatus for a precision plastic product with an inner side buckle as claimed in claim 1, wherein The initial matching gap between the ejection block (15) and the small elastic block (11) is 0.02-0.03mm.

7. The injection mold apparatus for a precision plastic product with an inner side buckle as claimed in claim 1, wherein The movement distance of the back mold part relative to the first extraction part is 8-10mm, and the movement speed is 8-12mm / s; based on the angle parameter of the guide inclined surface 50°±5°, the sliding distance of the small elastic block (11) along the guide inclined surface (1401) is 2.5-3.5mm, and the compression amount of the spring (12) during the sliding process is adaptively adjusted to 2-3mm; The forward movement distance of the back mold part is 8-10mm, and the movement speed is 8-12mm / s; the backward movement distance of the first extraction insert (2) relative to the back mold part is the same as the forward movement distance of the back mold part.

8. The injection mold apparatus for an inner side catch type precision plastic product according to claim 1, wherein The back mould core (3) and the back mould insert (9) are made of S136 hardened steel material, with a hardness of HRC45-48; the first core pulling insert (2) is made of NAK80 pre-hardened steel material, with a hardness of HRC37-41, and is easy to replace when the mould is worn; the guide column (4) is made of SUJ2 bearing steel material, with a diameter of 20mm and a length of 120mm.

9. A method for injection molding an inside snap-fit precision plastic product, characterized in that, It is demoulded by using the injection mould device of any one of claims 1-8, comprising the following steps: Step S1: separating the front mould and the back mould: after the overall injection moulding of the plastic product is completed, the front mould and the back mould are separated, and the plastic product is left in the back mould part; Step S2: first core pulling action: the ejection system is started, the ejector block (15) pushes the small elastic block (11), the back mould part is driven to move forward along the guide column (4), and the first core pulling insert (2) moves backward relative to the back mould part and is separated from the outside of the buckle of the plastic product (1); Step S3: separating the small elastic block: the small elastic block (11) contacts the 50° guide slope (1401) of the mould plate opening control block (14) and slides inwards along the slope, and is separated from the ejector block (15); Step S4: strong demoulding action: the flat ejector pin (10) is ejected, the buckle of the plastic product (1) is first elastically deformed outward, and then moves forward as a whole to realize complete demoulding; Step S5: resetting: the ejection system is reset, and the back mould part returns to the initial position.

10. The injection molding method of claim 9, wherein In step S2, the distance that the back mould part moves forward is 3-5mm, and in step S3, the distance that the small elastic block (11) moves inwards is 2-3mm; in step S4, the amount of elastic deformation of the buckle of the plastic product outward is 0.3-0.8mm.

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