Abs and pom plastic resin double-layer hitting ball for fascia gun and preparation method thereof

Abstract

This invention relates to the field of massage equipment accessories technology, and discloses a double-layered ABS and POM plastic resin striking ball for fascia guns and its preparation method. The striking ball includes a rigid polyoxymethylene core and a partially covered ABS resin coating layer. The rigid polyoxymethylene core includes a spherical core and an exposed connecting rod. The outer surface of the spherical core has inverted trapezoidal wedge-shaped interlocking grooves. During preparation, dried polyoxymethylene resin is injected into a primary mold to form the core with the aforementioned interlocking grooves. The core is then placed in a secondary coating mold for positioning and sealing of the connecting rod. Molten ABS resin containing color masterbatch is smoothly injected into the cavity to fill the interlocking grooves. After cooling, curing, demolding, and trimming and polishing, the finished product is obtained. This invention uses the interlocking groove structure to create a physical interlock between the inner and outer materials, compensating for insufficient bonding force caused by polarity differences and reducing slippage and peeling of the outer coating layer under high-frequency stress.

Description

Technical Field

[0001] This invention relates to the field of massage equipment accessories technology, specifically to a double-layered ABS and POM plastic resin striking ball for fascia guns and its preparation method. Background Technology

[0002] As a deep muscle relaxation tool, the fascia gun mainly relieves muscle soreness by impacting the target area of ​​the human body with high-frequency vibration. As an accessory of the fascia gun that comes into direct contact with the human body, the structural strength and surface characteristics of the hitting ball have a direct impact on the product's service life. In order to balance the impact resistance and rigidity of the internal structure with the smooth and wear-resistant properties of the external surface, some high-quality hitting balls have begun to be produced using a double-layer composite rubber coating molding process.

[0003] In practical material selection, polyoxymethylene (POM) resin is often used as an internal skeleton component due to its high mechanical strength and fatigue resistance; ABS resin has good surface gloss and scratch resistance, making it suitable as an outer coating material. However, due to the difference in polymer polarity between POM and ABS resin, these two materials are difficult to chemically cross-link during conventional injection molding, resulting in weak molecular bonding at the interface. When the hitting ball is used with a fascia gun for a long time under high-frequency alternating stress and dynamic impact, stress concentration will occur at the interface between the inner core and the outer coating layer. This complex stress state will gradually cause relative slippage between the inner and outer layers, leading to peeling, detachment, or fall off of the outer ABS coating layer. In addition, the structural design of the connecting rod of existing double-layer hitting balls often lacks consideration for stress distribution. When users frequently plug and unplug massage heads or devices for high-frequency vibration transmission, fatigue fracture may occur at the joint of the rod and the material due to uneven stress, which shortens the actual service life of the product to some extent. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a double-layered ABS and POM plastic resin striking ball for fascia guns and its preparation method. This solves the problems of insufficient interfacial bonding force caused by the difference in polarity between the inner and outer layer materials in existing double-layered massage heads, which leads to interlayer slippage and peeling under high-frequency impact, as well as fatigue fracture at the connection and insertion parts.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] In a first aspect, the present invention provides a double-layered ABS and POM plastic resin striking ball for fascia guns, comprising a rigid polyoxymethylene core and an ABS resin coating layer covering the outside of the rigid polyoxymethylene core; the double-layered striking ball is made of the following raw materials in parts by weight: 60.0 to 80.0 parts of polyoxymethylene resin; 20.0 to 40.0 parts of ABS resin; and 0.2 to 0.4 parts of color masterbatch; the rigid polyoxymethylene core comprises a spherical core and a connecting rod integrally formed with the spherical core, and an inverted trapezoidal wedge-shaped interlocking groove is formed on the outer surface of the spherical core.

[0007] By adopting the above technical solution, polyoxymethylene resin, as the core skeleton material, has the physical properties of high crystallinity, high rigidity and fatigue resistance. When subjected to high-frequency dynamic impact from the fascia gun, it can better maintain the dimensional stability of the sphere and reduce the risk of overall macroscopic deformation.

[0008] The ABS resin used for the outer coating layer has high surface gloss and scratch resistance, providing a smooth external contact surface. Considering the different polymer polarities of polyoxymethylene and ABS, it is often difficult for the two to undergo chemical cross-linking reaction at the injection molding interface to form covalent bonds.

[0009] To this end, an inverted trapezoidal wedge-shaped interlocking groove is opened on the outer surface of the polyoxymethylene spherical core. When the flowing ABS melt fills into the interlocking groove during the injection molding process and shrinks after cooling and solidification, the two materials form a physical nested shape in space.

[0010] Preferably, the connecting rod portion serves as an insertion area for connection with the fascia gun body, and the outer surface of the connecting rod portion is exposed and not covered by the ABS resin coating layer; the ABS resin coating layer only covers the spherical area of ​​the spherical core, and the junction of the spherical core and the connecting rod portion has a smooth spherical parting line that has been polished.

[0011] By adopting the above technical solution, since the connecting rod needs to be directly and strongly inserted into the power output hole of the fascia gun body, the connecting rod of the polyoxymethylene material is directly exposed. This can utilize the high shear resistance of polyoxymethylene itself to reduce the probability of fatigue fracture during repeated insertion and removal and high-frequency vibration. At the same time, this also helps to avoid the ABS coating layer from peeling and deforming due to compression at the junction. In addition, the smooth spherical parting line helps to weaken the micro-stress concentration points at the interface.

[0012] Furthermore, the angle between the inverted trapezoidal wedge-shaped interlocking groove and the outer surface of the spherical core is 15° to 30°.

[0013] By adopting the above technical solution, the included angle of the sidewall inclination of the undercut groove largely determines the flow resistance of injection filling and the pull-out resistance after molding. When the included angle is less than 15°, the difference in width between the groove opening and the groove bottom is small, the normal interlocking resistance is insufficient, and the ABS material in the groove will be cut and damaged during demolding. Conversely, when the included angle is greater than 30°, the space at the bottom of the groove becomes larger, which will cause air to be trapped inside during secondary overmolding injection, resulting in cavitation defects. Setting it to 15° to 30° can promote the structure to achieve mechanical balance between melt filling and solidification mechanical anchoring.

[0014] Secondly, the present invention also provides a method for preparing a double-layered ABS and POM plastic resin striking ball for a fascia gun, comprising the following steps:

[0015] S1. Heat and dry the polyoxymethylene resin for later use; mix the ABS resin and color masterbatch evenly and then heat and dry them for later use.

[0016] S2. The dried polyoxymethylene resin in S1 is heated and melted, and then injected into the cavity of a primary mold to fill it to form the spherical core and connecting rod. After pressure holding, cooling and solidification, the mold is opened and ejected to obtain a rigid polyoxymethylene core with the inverted trapezoidal wedge-shaped interlocking groove on the outer surface.

[0017] S3. Fix the rigid polyoxymethylene core obtained in S2 into the positioning position of the secondary overmolding mold, and lock and seal the non-overmolding area where the connecting rod is located; heat and melt the ABS resin material containing color masterbatch after drying in S1, and then inject the melt into the overmolding cavity at a low and stable injection speed to completely and evenly cover the outer surface of the spherical core and completely fill the inverted trapezoidal wedge-shaped interlocking groove. After holding pressure, cooling and solidifying, open the mold and demold to obtain the semi-finished hitting ball.

[0018] S4. Trim and remove sprues from the semi-finished hitting ball after demolding in S3, then grind and polish to obtain a complete double-layered ABS and POM plastic resin hitting ball for fascia guns.

[0019] By adopting the above technical solutions, considering that polyoxymethylene and ABS raw materials will undergo molecular chain hydrolysis and degradation due to trace amounts of moisture in the high-temperature melt state, the drying treatment in S1 can reduce the adverse interference of moisture vaporization on the density of the injection molded entity. S2 uses one-time molding to obtain a rigid inner core skeleton with grooves, which determines the basic dimensions for subsequent overmolding. In S3, by locking and sealing the non-overmolding area where the connecting rod is located, the ABS resin area is avoided. The filling mechanism is that a low and stable injection speed is used to allow the high-viscosity ABS melt wavefront to advance slowly, which is conducive to promoting the orderly discharge of gas inside the mold cavity and the undercut groove, thereby reducing the probability of air entrapment caused by high-speed injection, and allowing the ABS melt to have sufficient thermal conduction contact with the surface of the polyoxymethylene substrate. The subsequent cooling and solidification freezes the macromolecular chains, locking the physically interlocked shape. Combined with the finishing process in S4, the finished product is finally completed.

[0020] Preferably, in S1, the drying temperature of the polyoxymethylene resin is 80 to 90°C and the drying time is 2 to 4 hours; the drying temperature of the uniformly mixed ABS resin and color masterbatch material is 80 to 85°C and the drying time is 2 to 4 hours.

[0021] By adopting the above technical solution, polyoxymethylene has a high degree of crystallinity. The heating environment of 80 to 90°C combined with a duration of 2 to 4 hours helps the heat penetrate into the interior of the particles, causing the internal moisture to be converted into vapor and dissipated. ABS resin has hygroscopic properties. Controlling the drying temperature at 80 to 85°C aims to avoid the pigment components in the masterbatch from undergoing early thermal oxidation and discoloration due to excessively high temperatures, while promoting complete evaporation of moisture.

[0022] Furthermore, in S2, the temperature of the first stage of the barrel of the first injection molding machine is 170 to 190°C, the temperature of the second stage is 180 to 200°C, the temperature of the third stage is 190 to 210°C, and the nozzle temperature is 195 to 215°C; the melt injection speed of the first injection molding machine is 40 to 80 mm / s.

[0023] By adopting the above technical solution and setting a progressively increasing barrel temperature profile, the polyoxymethylene particles undergo a thermodynamic phase transition process of preheating, gradual melting, and complete plasticization during screw propulsion, reducing the occurrence of formaldehyde gas precipitation and decomposition due to local shear overheating; the nozzle temperature of 195 to 215°C maintains the low viscosity characteristics of the melt; and the injection speed of 40 to 80 mm / s facilitates the rapid filling of large-volume inner core mold cavities, thus avoiding the problem of premature crystallization and solidification of the melt at the leading edge, forming cold spots.

[0024] Preferably, in S2, the injection pressure of the first injection molding machine is 70 to 120 MPa, the holding pressure is 50 to 90 MPa, and the holding time is 3 to 10 s; the surface temperature of the primary mold is 60 to 80°C; the circulating water cooling temperature used for cooling and curing is 20 to 30°C, and the water cooling treatment time is 15 to 25 s.

[0025] By adopting the above technical solution, the injection molding machine provides a pressure of 70 to 120 MPa to overcome the flow resistance of the mold cavity. After the mold cavity is filled, the material is continuously replenished using a holding pressure of 50 to 90 MPa. Since the macromolecular chains undergo an ordered crystallization process during the molding of polyoxymethylene, resulting in volume shrinkage, the sufficient holding pressure can compensate for the volume shrinkage caused by crystallization, thereby maintaining the dimensional accuracy of the undercut groove feature. The mold temperature of 60 to 80°C is conducive to the generation of polyoxymethylene crystal nuclei and crystal growth, thereby reducing the internal stress of molding. The forced heat exchange is achieved by using circulating water cooling at 20 to 30°C, which allows the solidified structure to freeze and solidify quickly.

[0026] Furthermore, in S3, the temperature of the first stage of the second injection molding machine barrel is 190 to 210°C, the temperature of the second stage is 200 to 220°C, the temperature of the third stage is 210 to 230°C, and the nozzle temperature is 215 to 235°C; the low-speed stable injection speed is 20 to 40 mm / s.

[0027] By adopting the above technical solution, the ABS melt is given a higher initial temperature, which enhances the thermal activity of the polymer chain segments. At this time, the ABS melt contacts the cold polyoxymethylene core surface, and the highly active melt helps to achieve physical micro-wetting on its surface. The injection speed of 20 to 40 mm / s limits the flow rate and avoids the melt from jetting at the complex geometric features of the undercut groove, so that the filling mode presents a laminar flow propagation state and minimizes the interfacial air gap as much as possible.

[0028] Preferably, in S3, the injection pressure of the second injection molding machine is 50 to 90 MPa, the holding pressure is 40 to 70 MPa, and the holding time is 3 to 8 s; the surface temperature of the secondary overmolding mold is 40 to 60°C; the water cooling temperature used for cooling and curing is 20 to 30°C, and the water cooling treatment time is 15 to 20 s.

[0029] By adopting the above technical solutions, the secondary overmolding needs to overcome the filling resistance of the narrow undercut groove area. A pressure of 50 to 90 MPa is required to promote cavity filling. The secondary overmolding mold temperature of 40 to 60°C can reduce the temperature gradient between the inner and outer materials, causing the ABS overmolding layer to generate centripetal wrapping stress when it cools, solidifies, and shrinks, thereby better clamping the undercut groove structure. Water cooling treatment removes heat to shorten the molding cycle.

[0030] Furthermore, in S4, the semi-finished striking ball is trimmed and de-sprued to remove the sprue head and flash from the mold closing process; the parting line and fine seams of the spherical surface generated during demolding are finely polished using polishing equipment.

[0031] By adopting the above technical solutions, waste materials and burrs that generate stress concentration during the molding process are removed by physical cutting, and visual defects of the parting line are eliminated by grinding and polishing, thereby improving the smoothness of the ABS outer layer and reducing the potential for rough seams to become the starting point of structural cracks during use.

[0032] This invention provides a double-layered ABS and POM plastic resin striking ball for fascia guns and its preparation method. It has the following beneficial effects:

[0033] 1. This invention overcomes the limitation that these two polymer materials with different polarities are difficult to chemically crosslink by opening inverted trapezoidal wedge-shaped interlocking grooves on the surface of the polyoxymethylene inner core and covering it with an ABS resin layer. During the injection molding process, the ABS melt fills the interlocking grooves and cools and solidifies, forming a nested morphology of physical space. This mechanical interlocking structure transforms the shear stress generated during external operation into local compressive stress, thereby reducing the risk of slippage and peeling of the inner and outer layers when the ball is hit at high frequency.

[0034] 2. In this invention, the connecting rod, which serves as the force-bearing insertion area, is directly exposed without being coated with glue. This preserves the inherent rigidity and fatigue resistance of the polyoxymethylene material, reducing the likelihood of fatigue fracture of the massage head during frequent insertion and removal and power transmission. At the same time, a smooth spherical parting line is used at the junction of the spherical core and the connecting rod to weaken the stress concentration points at the interface and prevent peeling and warping defects at the edge of the ABS coating layer when subjected to pressure.

[0035] 3. The preparation process of this invention adopts a low and stable injection speed in the secondary injection molding overmolding stage, combined with specific multi-stage barrel temperature and mold temperature control, so that the high viscosity ABS melt is slowly advanced in a laminar flow state and fills the complex undercut groove structure. This parameter setting promotes the orderly discharge of gas in the cavity and groove, reduces the probability of air entrapment or cold spot caused by high-speed injection, and thus improves the bonding density of the double-layer injection molding structure and the product yield. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the spectrum of the control sample, pure polyoxymethylene resin particles, of the present invention.

[0037] Figure 2 This is a schematic diagram of the spectrum of ABS resin granules, the control sample of this invention;

[0038] Figure 3This is a schematic diagram of the spectrum of the composite interface material scraped from the interface of the present invention.

[0039] Figure 4 This is a schematic diagram of the test spectrum of the spline energy storage modulus as a function of frequency according to the present invention;

[0040] Figure 5 This is a schematic diagram of the test spectrum of the spline damping loss factor as a function of frequency according to the present invention.

[0041] Figure 6 This is a schematic diagram of the tensile-displacement test of a representative sample of the present invention;

[0042] Figure 7 This is a schematic diagram of the torque-torsion angle test of a representative sample of the present invention;

[0043] Figure 8 This is a schematic diagram showing the change of the transmission force of the sample of the present invention over time in a drop hammer impact test;

[0044] Figure 9 This is a schematic diagram showing the change in the mass gain rate of the sample of the present invention over time in an artificial sweat immersion test. Detailed Implementation

[0045] 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.

[0046] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0047] Polyoxymethylene resin is a commercially available injection molding grade engineering plastic with a melt flow rate of 9.0 g / 10 min.

[0048] The ABS resin, CAS number 9003-56-9, is a commercially available injection molding grade ABS resin.

[0049] In this invention, the units of measurement for all materials and solvents are uniformly referred to as parts by weight.

[0050] Example 1:

[0051] This embodiment provides a method for preparing a double-layered ABS and POM plastic resin striking ball for a fascia gun, including the following steps:

[0052] S1. Place 70.0 parts of pre-prepared polyoxymethylene resin into a hot air drying oven and dry at 85°C for 3 hours for later use; separately, put 30.0 parts of ABS resin and 0.3 parts of color masterbatch into a mixer and mix evenly, then put them into a hot air drying oven and dry at 82°C for 3 hours for later use.

[0053] S2. The dried polyoxymethylene resin is added to the barrel of the first injection molding machine and heated to melt. The single injection volume of the first injection molding machine is set to 70.0 parts by weight of polyoxymethylene resin. The temperature of the first injection molding machine is set to 180°C for the first stage, 190°C for the second stage, 200°C for the third stage, and 205°C for the nozzle. Then, the melt is injected into the cavity of the primary mold at an injection speed of 60 mm / s to fill the ball core. The structure is as follows: the injection pressure is set to 90MPa, the holding pressure is set to 70MPa, the holding time is set to 6s, the mold surface temperature is maintained at 70℃, and after 20s of 25℃ circulating water cooling and curing, the mold is opened and ejected to obtain a spherical rigid monolithic core with a 22° angled inverted trapezoidal wedge-shaped interlocking groove. The rigid monolithic core includes a spherical core and a connecting rod integrally formed with the spherical core. The inverted trapezoidal wedge-shaped interlocking groove is set on the outer surface of the spherical core.

[0054] S3. Fix the obtained rigid polyoxymethylene core into the positioning position of the secondary overmolding mold and lock and seal the non-overmolding area (the connecting rod serves as the insertion area for connection with the fascia gun body, and is protected by the mold during the secondary overmolding process, preventing it from being covered by ABS resin). Add the dried ABS resin material containing color masterbatch into the barrel of the second injection molding machine and heat and melt it until it reaches a uniform flow state. Set the single injection volume of the second injection molding machine to 30.3 parts by weight, calculated based on the total amount of ABS resin and color masterbatch. The temperature of the first stage of the two injection molding machines is set to 200℃, the second stage to 210℃, the third stage to 220℃, and the nozzle temperature to 225℃. Then, the melt is injected into the overmolding cavity at a low and stable injection speed of 30mm / s, completely and evenly covering the outer surface of the sphere and completely filling the interlocking undercut groove. The injection pressure is set to 70MPa, the holding pressure is set to 55MPa, the holding time is set to 5s, and the mold surface temperature is maintained at 50℃. After 18s of water cooling and solidification at 25℃, the mold is opened and demolded to obtain the semi-finished striking ball.

[0055] S4. Trim and remove the sprue from the demolded semi-finished ball, removing the sprue head and flash from the mold closing. Then, use polishing equipment to finely grind and polish the parting line and minor seams on the ball surface. After surface dust removal, assemble it with other external connecting parts such as silicone parts. Finally, after passing the full quality inspection of appearance, size and performance, a complete ABS and POM plastic resin double-layered hitting ball for fascia guns is obtained.

[0056] Example 2:

[0057] This embodiment provides a method for preparing a double-layered ABS and POM plastic resin striking ball for a fascia gun, including the following steps:

[0058] S1. Place 80.0 parts of the pre-prepared polyoxymethylene resin into a hot air drying oven and dry at 80°C for 2 hours for later use; separately, put 20.0 parts of ABS resin and 0.2 parts of color masterbatch into a mixer and mix evenly, then put them into a hot air drying oven and dry at 80°C for 2 hours for later use.

[0059] S2. The dried polyoxymethylene resin is added to the barrel of the first injection molding machine and heated to melt. The single injection volume of the first injection molding machine is set to 80.0 parts by weight of polyoxymethylene resin. The temperature of the first injection molding machine is set to 170°C for the first stage, 180°C for the second stage, 190°C for the third stage, and 195°C for the nozzle. Then, the melt is injected into the cavity of the primary mold at an injection speed of 40 mm / s to fill the ball core. The structure is as follows: the injection pressure is set to 70MPa, the holding pressure is set to 50MPa, the holding time is set to 3s, the mold surface temperature is maintained at 60℃, and after 15s of 20℃ circulating water cooling and curing, the mold is opened and ejected to obtain a spherical rigid monolithic core with a 15° angled inverted trapezoidal wedge-shaped interlocking groove. The rigid monolithic core includes a spherical core and a connecting rod integrally formed with the spherical core. The inverted trapezoidal wedge-shaped interlocking groove is set on the outer surface of the spherical core.

[0060] S3. Fix the obtained rigid polyoxymethylene core into the positioning position of the secondary overmolding mold and lock and seal the non-overmolding area (the connecting rod part serves as the insertion area for connection with the fascia gun body, and is protected by the mold during the secondary overmolding process, preventing it from being covered by ABS resin). Add the dried ABS resin material containing color masterbatch into the barrel of the second injection molding machine and heat and melt it until it reaches a uniform flow state. Set the single injection volume of the second injection molding machine to the injection volume corresponding to 20.2 parts by weight of the total amount of ABS resin and color masterbatch. The temperature of the first stage of the two injection molding machines is set to 190℃, the second stage to 200℃, the third stage to 210℃, and the nozzle temperature to 215℃. Then, the melt is injected into the overmolding cavity at a low and stable injection speed of 20mm / s, completely and evenly covering the outer surface of the sphere and completely filling the interlocking undercut groove. The injection pressure is set to 50MPa, the holding pressure is set to 40MPa, the holding time is set to 3s, and the mold surface temperature is maintained at 40℃. After 15s of water cooling and solidification at 20℃, the mold is opened and demolded to obtain the semi-finished striking ball.

[0061] S4. Trim and remove the sprue from the demolded semi-finished ball, removing the sprue head and flash from the mold closing. Then, use polishing equipment to finely grind and polish the parting line and minor seams on the ball surface. After surface dust removal, assemble it with other external connecting parts such as silicone parts. Finally, after passing the full quality inspection of appearance, size and performance, a complete ABS and POM plastic resin double-layered hitting ball for fascia guns is obtained.

[0062] Example 3:

[0063] This embodiment provides a method for preparing a double-layered ABS and POM plastic resin striking ball for a fascia gun, including the following steps:

[0064] S1. Place 60.0 parts of pre-prepared polyoxymethylene resin into a hot air drying oven and dry at 90°C for 4 hours for later use; separately, put 40.0 parts of ABS resin and 0.4 parts of color masterbatch into a mixer and mix evenly, then put them into a hot air drying oven and dry at 85°C for 4 hours for later use.

[0065] S2. The dried polyoxymethylene resin is added to the barrel of the first injection molding machine and heated to melt. The single injection volume of the first injection molding machine is set to 60.0 parts by weight of polyoxymethylene resin. The temperature of the first injection molding machine is set to 190°C for the first stage, 200°C for the second stage, 210°C for the third stage, and 215°C for the nozzle. Then, the melt is injected into the cavity of the primary mold at an injection speed of 80 mm / s to fill the spherical core. The injection pressure is set to 120MPa, the holding pressure is set to 90MPa, the holding time is set to 10s, the mold surface temperature is maintained at 80℃, and after 25s of 30℃ circulating water cooling and curing, the mold is opened and ejected to obtain a spherical rigid monolithic core with a 30° angled inverted trapezoidal wedge-shaped interlocking groove. The rigid monolithic core includes a spherical core and a connecting rod integrally formed with the spherical core. The inverted trapezoidal wedge-shaped interlocking groove is set on the outer surface of the spherical core.

[0066] S3. Fix the obtained rigid polyoxymethylene core into the positioning position of the secondary overmolding mold and lock and seal the non-overmolding area (the connecting rod part serves as the insertion area for connection with the fascia gun body, and is protected by the mold during the secondary overmolding process, preventing it from being covered by ABS resin). Add the dried ABS resin material containing color masterbatch into the barrel of the second injection molding machine and heat and melt it until it reaches a uniform flow state. Set the single injection volume of the second injection molding machine to the injection volume corresponding to 40.4 parts by weight of the total amount of ABS resin and color masterbatch. The temperature of the first stage of the two injection molding machines is set to 210℃, the second stage to 220℃, the third stage to 230℃, and the nozzle temperature to 235℃. Then, the melt is injected into the overmolding cavity at a low and stable injection speed of 40mm / s, completely and evenly covering the outer surface of the sphere and completely filling the interlocking undercut groove. The injection pressure is set to 90MPa, the holding pressure is set to 70MPa, the holding time is set to 8s, and the mold surface temperature is maintained at 60℃. After 20s of water cooling and solidification at 30℃, the mold is opened and demolded to obtain the semi-finished striking ball.

[0067] S4. Trim and remove the sprue from the demolded semi-finished ball, removing the sprue head and flash from the mold closing. Then, use polishing equipment to finely grind and polish the parting line and minor seams on the ball surface. After surface dust removal, assemble it with other external connecting parts such as silicone parts. Finally, after passing the full quality inspection of appearance, size and performance, a complete ABS and POM plastic resin double-layered hitting ball for fascia guns is obtained.

[0068] Example 4:

[0069] This embodiment provides a method for preparing a double-layered ABS and POM plastic resin striking ball for a fascia gun, including the following steps:

[0070] S1. Place 75.0 parts of pre-prepared polyoxymethylene resin into a hot air drying oven and dry at 85°C for 3 hours for later use; separately, put 25.0 parts of ABS resin and 0.3 parts of color masterbatch into a mixer and mix evenly, then place them into a hot air drying oven and dry at 82°C for 3 hours for later use.

[0071] S2. The dried polyoxymethylene resin is added to the barrel of the first injection molding machine and heated to melt. The single injection volume of the first injection molding machine is set to 75.0 parts by weight, which is the equivalent of the amount of polyoxymethylene resin fed. The temperature of the first injection molding machine is set to 180°C for the first stage, 190°C for the second stage, 200°C for the third stage, and 205°C for the nozzle. Then, the melt is injected into the cavity of the primary mold at an injection speed of 60 mm / s to fill the ball core. The structure is as follows: the injection pressure is set to 90MPa, the holding pressure is set to 70MPa, the holding time is set to 6s, the mold surface temperature is maintained at 70℃, and after 20s of 25℃ circulating water cooling and curing, the mold is opened and ejected to obtain a spherical rigid monolithic core with a 25° angled inverted trapezoidal wedge-shaped interlocking groove. The rigid monolithic core includes a spherical core and a connecting rod integrally formed with the spherical core. The inverted trapezoidal wedge-shaped interlocking groove is set on the outer surface of the spherical core.

[0072] S3. Fix the obtained rigid polyoxymethylene core into the positioning position of the secondary overmolding mold and lock and seal the non-overmolding area (the connecting rod serves as the insertion area for connection with the fascia gun body, and is protected by the mold during the secondary overmolding process, preventing it from being covered by ABS resin). Add the dried ABS resin material containing color masterbatch to the barrel of the second injection molding machine and heat and melt it until it reaches a uniform flow state. Set the single injection volume of the second injection molding machine to 25.3 parts by weight, calculated based on the total amount of ABS resin and color masterbatch. The temperature of the first stage of the two injection molding machines is set to 200℃, the second stage to 210℃, the third stage to 220℃, and the nozzle temperature to 225℃. Then, the melt is injected into the overmolding cavity at a low and stable injection speed of 30mm / s, completely and evenly covering the outer surface of the sphere and completely filling the interlocking undercut groove. The injection pressure is set to 70MPa, the holding pressure is set to 55MPa, the holding time is set to 5s, and the mold surface temperature is maintained at 50℃. After 18s of water cooling and solidification at 25℃, the mold is opened and demolded to obtain the semi-finished striking ball.

[0073] S4. Trim and remove the sprue from the demolded semi-finished ball, removing the sprue head and flash from the mold closing. Then, use polishing equipment to finely grind and polish the parting line and minor seams on the ball surface. After surface dust removal, assemble it with other external connecting parts such as silicone parts. Finally, after passing the full quality inspection of appearance, size and performance, a complete ABS and POM plastic resin double-layered hitting ball for fascia guns is obtained.

[0074] Comparative Example 1:

[0075] Compared with Example 1, the difference is that the cavity surface of the primary mold in S2 is designed as a smooth spherical surface, so that the surface of the polyoxymethylene rigid monolithic core after molding does not have an inverted trapezoidal wedge-shaped interlocking groove. All other aspects are the same.

[0076] Comparative Example 2:

[0077] Compared with Example 1, the difference is that the outer layer material ABS resin in S1 and S3 is replaced with an equal part by weight of foamed polyurethane soft resin, and all other aspects are the same.

[0078] Comparative Example 3:

[0079] Compared with Example 1, the difference is that the outer layer material ABS resin in S1 and S3 is replaced with traditional high-porosity EVA foam material, while the rest are the same.

[0080] Comparative Example 4:

[0081] Compared with Example 1, the difference is that in S3, the injection pressure of the second injection molding machine is set to a very low 30MPa, and the holding pressure is set to 20MPa, while the rest are the same.

[0082] Test Example 1:

[0083] Take the double-layer hitting ball prepared in Example 1, cut open the finished ball, and scrape off the interface peeling layer material at the junction of the inner polyoxymethylene core and the outer ABS resin coating layer with a blade to collect the composite interface test sample. At the same time, take pure polyoxymethylene resin particles and pure ABS resin particles as control samples respectively.

[0084] The collected composite interface test samples, polyoxymethylene resin particles, and ABS resin particles were placed in a liquid nitrogen environment for freezing treatment for 15 minutes, and then crushed in a cryogenic grinder to obtain powder with a particle size in the range of 10 to 20 micrometers.

[0085] At a mass ratio of 1:100, the pulverized sample powders of each group were mixed with potassium bromide powder, ground evenly in an agate mortar, and then pressed into test slices in a tablet press mold under a pressure of 20 MPa. The slices were then placed in the test chamber of a Fourier transform infrared spectrometer, and the scanning wavenumber range was set to 4000 cm⁻¹. -1 Up to 400cm -1 Spectral resolution of 4 cm -1 Each test involved 32 scans, with transmission mode scans performed to record the infrared spectrum and the wavenumber of characteristic absorption peaks.

[0086] Table 1: Record of Infrared Characteristic Absorption Peak Wavenumber Tests for Pure Polyoxymethylene, Pure ABS, and Interface Composite Materials

[0087] Test sample <![CDATA[Wavenumber of the absorption peak of the ether bond (C-O-C) / cm -1 > <![CDATA[Wave number of nitrile group (-C≡N) absorption peak / cm -1 > <![CDATA[Wavenumber of benzene ring skeleton vibration absorption peak / cm -1 > <![CDATA[Wavenumber of aliphatic (C-H) absorption peak / cm -1 > Does it produce new characteristic absorption peaks? Pure polyoxymethylene resin 1091.2 Not detected Not detected 2898.42931.7 - ABS resin pure material Not detected 2238.5 1602.81493.6 2845.12924.3 - Composite interface materials 1088.7 2241.1 1604.21495.0 2848.62901.52929.8 no

[0088] According to Table 1 and Figures 1 to 3It can be seen that the pure polyoxymethylene resin sample has a diameter of 1091.2 cm⁻¹. -1 The characteristic peak of COC ether bond stretching vibration is present at 2238.5 cm⁻¹, while that of the ABS resin pure sample is at 2238.5 cm⁻¹. -1 A nitrile absorption peak is present at 1602.8 cm⁻¹. -1 and 1493.6cm -1 The table shows an absorption peak for the vibration of the benzene ring skeleton. The test results for the specific group absorption peaks of the pure material sample are not detected. This is because the polyoxymethylene molecular skeleton itself does not contain nitrile groups or benzene ring structures, and the ABS molecular structure does not contain COC macromolecular ether bonds, which is consistent with the intrinsic chemical composition of these two resins. At the same time, the pure material sample is only used as a basic reference in this test, so the column for whether new characteristic absorption peaks are generated is marked as -.

[0089] The spectrum of the composite interface material also contains the corresponding COC ether bond vibration peak of polyoxymethylene (1088.7 cm⁻¹). -1 ) and the corresponding nitrile characteristic peak of ABS (2241.1 cm⁻¹). -1 ) and the characteristic peak of benzene ring vibration (1604.2 cm⁻¹) -1 1495.0cm -1 The spectral characteristics of the composite interface material, as can be seen from the comparison of the spectral morphology, are mainly the superposition of the original characteristic peaks of polyoxymethylene and ABS. Due to the influence of local mixing state and interfacial stress, the wavenumbers of some characteristic peaks appear to be 1 to 4 cm⁻¹. -1 The shift was observed, but no absorption peaks characterizing other novel covalent bonds were detected in the full spectrum scan.

[0090] The above test results show that, under the injection molding processing conditions of the embodiment, the ABS resin in the molten state did not undergo obvious chemical cross-linking reaction during the process of covering the interface of the polyoxymethylene substrate. This data indicates that it is difficult for polyoxymethylene and ABS resin to form a chemically compatible bond with structural strength under thermodynamic injection molding conditions. Without the presence of interfacial chemical bonding, if a spherical structure without geometric features is used, the interface will experience relative slippage and peeling under repeated external forces. Based on this, the inverted trapezoidal wedge-shaped interlocking groove constructed on the inner core surface in this embodiment allows the high-temperature melt injected in the second injection to fill inward during the injection and holding pressure stages, and forms an interlocking spatial nesting morphology after cooling and solidification.

[0091] Test Example 2:

[0092] The double-layered hitting balls prepared in Example 1 and Comparative Example 2 were cut along the cross-sectional direction of the ball. Composite structural strips containing an inner polyoxymethylene core and an outer rubber layer were cut out respectively. The cut surfaces were polished flat to obtain rectangular composite test strips with a length of 35 mm, a width of 10 mm, and a thickness of 3 mm.

[0093] The composite test strip was installed in the test fixture of the dynamic thermomechanical analyzer and a three-point bending test mode was adopted, with the support span set to 20mm.

[0094] The test environment temperature was set at 30℃, and the applied dynamic alternating strain amplitude was 50μm.

[0095] The test frequency scanning range was set to 10Hz to 80Hz. Frequency scanning tests were performed on the two sets of samples. The energy storage modulus and damping loss factor of the samples at different frequencies were recorded. Three samples were tested in parallel for each set of samples. The data listed in Table 2 are the average values ​​of the test results of the three samples. The relative standard deviation of each test point does not exceed 5%.

[0096] Table 2: Dynamic mechanical property test data of composite spline of Example 1 and Comparative Example 2 at different frequencies

[0097] Test frequency / Hz Example 1 Energy storage modulus / MPa Example 1 Damping Loss Factor (tanδ) Comparative Example 2: Storage Modulus / MPa Comparative Example 2 Damping Loss Factor (tanδ) 15.3 2451.7 0.0241 815.3 0.1684 27.8 2489.2 0.0275 832.9 0.1842 42.6 2516.5 0.0298 859.1 0.2057 59.1 2552.4 0.0336 887.6 0.2291 75.4 2573.8 0.0382 911.4 0.2458

[0098] According to Table 2 and Figure 4 and Figure 5 It can be seen that the storage modulus of the composite specimen in Example 1 is distributed between 2451.7MPa and 2573.8MPa in the test frequency range of 10Hz to 80Hz, while the storage modulus of Comparative Example 2 is distributed between 815.3MPa and 911.4MPa. The damping loss factor of Example 1 is distributed between 0.0241 and 0.0382. The above data are the average values ​​of the test results of parallel samples. The test results show a continuous trend of change with increasing frequency, indicating that the sample did not show sudden structural instability or abnormal test fluctuations in the frequency scanning range. The damping loss factor of Comparative Example 2 is distributed between 0.1684 and 0.2458. In polymer dynamic mechanical analysis, the storage modulus reflects the material's ability to store elastic deformation energy under alternating stress, while the damping loss factor reflects the ratio of energy consumed by internal friction to stored energy.

[0099] The test results above show that Comparative Example 2, which replaced the outer covering layer with foamed polyurethane flexible resin, exhibited data characteristics of lower storage modulus and higher damping loss factor under the set high-frequency test conditions. This suggests that the structure containing the flexible foam layer may produce relatively obvious viscoelastic deformation when subjected to alternating stress. Some of the work done by the external load is absorbed by the friction within the material and converted into heat energy. Example 1 uses a polyoxymethylene core and an ABS outer layer composite, which maintains a relatively high storage modulus in the same frequency band and keeps the damping loss factor at a low level. This data characteristic shows that when the composite structure of Example 1 is subjected to high-frequency stress, the internal viscous flow response is somewhat limited, and the deformation is mainly concentrated in the elastic range. The lower internal dissipation ratio reduces the heat conversion loss when the input mechanical energy is conducted within the structure.

[0100] Test Example 3:

[0101] The finished double-layer hitting balls prepared in Examples 1 to 4, Comparative Example 1 and Comparative Example 4 were used as test objects. The end of the polyoxymethylene connecting rod of the sample was fixed in the lower clamp of the universal testing machine. The upper ring clamp that matched the outer contour of the outer ABS coating layer was used for fixation. The tensile speed was set to 5 mm / min. Tensile load was applied along the sample axis. The maximum tensile force value when the coating layer and the inner core separated or were damaged was recorded. The tensile force-displacement response curve was recorded by the system.

[0102] Take samples from the same batch, fix their connecting rods in the fixed end clamp of the torsion testing machine, use a clamp to fix the outer ABS coating layer, set the torsion angular velocity to 10° / min, apply torsional torque along the plane perpendicular to the axis of the connecting rod, record the maximum torque value when the interface slips or breaks, and record the torque-torsion angle response curve by the system.

[0103] Samples from the same batch were installed on a fatigue testing bench. The impact frequency was set to 50 Hz, the impact amplitude to 10 mm, and the impact object was a silicone target plate simulating the damping characteristics of human muscle. The number of continuous cycle tests was set to 1,000,000. After the test, the relative bonding state between the rubber layer and the inner core was observed and recorded. Three samples were tested in parallel for each group of test samples. The maximum breaking tensile force and maximum breaking torque listed in Table 3 are the average values ​​of the three samples. After failure, the interface failure morphology was observed simultaneously to distinguish failure modes such as interface slippage, local loosening, rubber layer tearing, or material failure near the undercut groove.

[0104] Table 3: Mechanical damage and fatigue test data of composite samples from the examples and comparative examples

[0105] Test sample Maximum breaking tensile force / N Maximum breaking torque / N·m Fatigue test results (after 1,000,000 impacts) Example 1 2154.6 18.2 No obvious relative displacement was observed, and the adhesive layer did not peel off. Example 2 2087.3 17.5 No obvious relative displacement was observed, and the adhesive layer did not peel off. Example 3 2210.1 19.1 No obvious relative displacement was observed, and the adhesive layer did not peel off. Example 4 2135.8 18.6 No obvious relative displacement was observed, and the adhesive layer did not peel off. Comparative Example 1 245.2 2.1 After approximately 150,000 cycles, the coating layer begins to slip. Comparative Example 4 856.4 6.8 The interface became loose after approximately 480,000 cycles.

[0106] According to Table 3 and Figure 6 and Figure 7 It can be seen that the maximum breaking tensile force of the samples in Examples 1 to 4 in the axial tensile test ranged from 2087.3 N to 2210.1 N, and the maximum breaking torque ranged from 17.5 N·m to 19.1 N·m. After undergoing fatigue testing with one million high-frequency impacts, no obvious loosening or detachment was observed in the appearance. In contrast, Comparative Example 1, which did not have a groove structure on the inner core surface, had a maximum tensile force and torque of only 245.2 N and 2.1 N·m, respectively, and slipped in the early stage of the fatigue test. Comparative Example 4, which had a lower molding pressure, had a failure index between the two examples, and the interface loosened in the middle of the fatigue test.

[0107] The above test results indicate that the surface structure of the inner core and the secondary injection molding process parameters affect the macroscopic load-bearing capacity of the composite interface. The bonding strength of Comparative Example 1 mainly depends on the physical adhesion between the heterogeneous polymer interfaces and the normal clamping force generated by molding shrinkage. Under the action of external shear force, interface slippage will occur relatively. In Comparative Example 4, due to insufficient injection pressure, the melt failed to fully vent and fill the internal space of the undercut groove. The micro gaps left at the interface joint caused stress concentration when subjected to force, thus resulting in early structural yielding. Examples 1 to 4 constructed inverted trapezoidal wedge-shaped interlocking undercut grooves on the surface of the polyoxymethylene inner core. Under suitable injection pressure parameters, the outer overlay material filled the groove. After curing, the two formed a spatial nested fit. Among them, there are differences in the undercut groove angle and some injection molding process parameters in Examples 1 to 4. The test results are used to illustrate that a high interface load-bearing capacity can be obtained within the angle range and process window, rather than attributing the difference in a single mechanical index solely to the change in the undercut groove angle.

[0108] Test Example 4:

[0109] Double-layered impact balls prepared in Examples 1 and 2, as well as Comparative Examples 2 and 3, were used as test objects. The connecting rod of the sample was fixed on the force sensor fixture of the drop hammer impact tester base. The test environment temperature was maintained at 25°C. A flat-bottomed steel drop hammer with a mass of 2.0 kg was dropped freely from a height of 150 mm to impact the top of the sample. The transmitted impact force-time history curve collected by the force sensor was recorded. The system was used to integrate and convert the response curve to obtain the energy transmittance during the impact process.

[0110] Samples from the same batch were placed in a constant temperature drying oven and treated until their mass was constant. The initial mass was weighed, and a simulated sweat solution containing 2 wt% sodium chloride and a small amount of water-soluble red pigment was prepared as the soaking medium.

[0111] The sample was completely immersed in artificial sweat maintained at 37°C and left to soak for 24 hours.

[0112] Remove the sample, wipe off the free liquid adhering to the surface with a lint-free cloth, weigh the sample after testing, and calculate the mass increase rate. Weighing is performed using an electronic balance with an accuracy of 0.1 mg. Before weighing each sample, remove the free liquid from the surface by wiping in the same way. Three samples are tested in parallel for each group. The data listed in Table 4 are the average values ​​of the three samples. Observe and record the pigment residue on the sample surface under natural light.

[0113] Table 4: Impact Transmission and Surface Permeability Test Data of Examples and Comparative Samples

[0114] Test sample Peak transmitted impact force / N Energy transmittance / % Mass increase rate after soaking for 24 hours / % Surface pigment residue appearance observation Example 1 1485.6 89.4 0.02 No obvious pigment adhesion was observed on the surface. Example 2 1462.3 88.1 0.05 No obvious pigment adhesion was observed on the surface. Comparative Example 2 512.8 32.7 1.84 Visible light red penetration marks are present on the surface. Comparative Example 3 684.5 41.3 9.52 The surface and shallow pores are red.

[0115] According to Table 4 and Figure 8 and Figure 9 It can be seen that the peak transmitted impact force of Examples 1 and 2 in the drop hammer impact test is between 1462.3N and 1485.6N, and the energy transmittance is greater than 88%; the mass increase rate after 24 hours of immersion is not higher than 0.05%, and no obvious pigment residue is observed on the surface. In contrast, the peak transmitted impact force of Comparative Examples 2 and 3 is between 512.8N and 684.5N, the energy transmittance is between 32.7% and 41.3%, the mass increase rate after immersion is distributed in the range of 1.84% to 9.52%, and visible pigment penetration is present on the surface after wiping.

[0116] The above physical performance tests reflect the correlation between the dynamic mechanical response and macroscopic physical structure of polymer materials. The energy transfer law of materials under short-term impact loads is related to the viscoelastic modulus. The polyoxymethylene and ABS resin used in the example form a double rigid structure with high initial stiffness. The instantaneous deformation generated when subjected to a drop hammer impact is relatively small. This characteristic limits the large-scale slippage of polymer chain segments inside the material and reduces the hysteresis dissipation caused by internal friction. This allows a large proportion of the input mechanical kinetic energy to be transferred to the connecting rod and the bottom force sensor through the composite structure. In contrast, the foamed polyurethane or EVA material in the comparative example has a lower modulus and will undergo greater compressive deformation during the impact. Some of the input energy is converted into heat energy to overcome intermolecular friction, which is reflected in the test data as a decrease in the peak value of the transmitted force and an increase in the pulse response time.

[0117] On the other hand, the water absorption and permeation behavior of materials is affected by the degree of surface micro-density. The foamed structure or soft porous coating layer contained in the comparative example has a certain free volume or micropores. Under capillary action, water and pigment molecules are more likely to diffuse into the matrix. The ABS resin used in the example exhibits a relatively continuous and dense surface morphology after injection molding, which limits the penetration path of liquid media under normal environmental pressure.

[0118] 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 double-layered striking ball made of ABS and POM plastic resin for a fascia gun, characterized in that, The double-layer hitting ball includes a rigid polyoxymethylene core and an ABS resin coating layer covering the outside of the rigid polyoxymethylene core. The double-layered hitting ball is made from the following parts by weight of raw materials: 60.0 to 80.0 parts of polyoxymethylene resin; 20.0 to 40.0 parts of ABS resin; 0.2 to 0.4 parts of color masterbatch; The rigid polyoxymethylene core includes a spherical core and a connecting rod integrally formed with the spherical core. The outer surface of the spherical core is provided with an inverted trapezoidal wedge-shaped interlocking groove.

2. The ABS and POM plastic resin double-layer striking ball for the fascia gun according to claim 1, characterized in that, The connecting rod portion serves as the insertion area for connection with the fascia gun body. The outer surface of the connecting rod portion is exposed and not covered by the ABS resin coating layer. The ABS resin coating layer only covers the spherical area of ​​the spherical core, and the junction of the spherical core and the connecting rod portion has a smooth spherical parting line that has been polished.

3. The ABS and POM plastic resin double-layer striking ball for the fascia gun according to claim 1, characterized in that, The angle between the inverted trapezoidal wedge-shaped interlocking groove and the outer surface of the spherical core is 15° to 30°.

4. A method for preparing a double-layered ABS and POM plastic resin striking ball for a fascia gun according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Heat and dry the polyoxymethylene resin for later use; mix the ABS resin and color masterbatch evenly and then heat and dry them for later use. S2. The dried polyoxymethylene resin in S1 is heated and melted, and then injected into the cavity of a primary mold to fill it to form the spherical core and connecting rod. After pressure holding, cooling and solidification, the mold is opened and ejected to obtain a rigid polyoxymethylene core with the inverted trapezoidal wedge-shaped interlocking groove on the outer surface. S3. Fix the rigid polyoxymethylene core obtained in S2 into the positioning position of the secondary overmolding mold, and lock and seal the non-overmolding area where the connecting rod is located; heat and melt the ABS resin material containing color masterbatch after drying in S1, and then inject the melt into the overmolding cavity at a low and stable injection speed to completely and evenly cover the outer surface of the spherical core and completely fill the inverted trapezoidal wedge-shaped interlocking groove. After holding pressure, cooling and solidifying, open the mold and demold to obtain the semi-finished hitting ball. S4. Trim and remove sprues from the semi-finished hitting ball after demolding in S3, then grind and polish to obtain a complete double-layered ABS and POM plastic resin hitting ball for fascia guns.

5. The method for preparing the double-layered ABS and POM plastic resin striking ball for the fascia gun according to claim 4, characterized in that, In S1, the drying temperature of the polyoxymethylene resin is 80 to 90°C, and the drying time is 2 to 4 hours; the drying temperature of the uniformly mixed ABS resin and color masterbatch material is 80 to 85°C, and the drying time is 2 to 4 hours.

6. The method for preparing the double-layered ABS and POM plastic resin striking ball for the fascia gun according to claim 4, characterized in that, In S2, the temperature of the first stage of the barrel of the first injection molding machine is 170 to 190°C, the temperature of the second stage is 180 to 200°C, the temperature of the third stage is 190 to 210°C, and the nozzle temperature is 195 to 215°C; the melt injection speed of the first injection molding machine is 40 to 80 mm / s.

7. The method for preparing the double-layered ABS and POM plastic resin striking ball for a fascia gun according to claim 4, characterized in that, In S2, the injection pressure of the first injection molding machine is 70 to 120 MPa, the holding pressure is 50 to 90 MPa, and the holding time is 3 to 10 s; the surface temperature of the primary mold is 60 to 80 ℃; the circulating water cooling temperature used for cooling and curing is 20 to 30 ℃, and the water cooling treatment time is 15 to 25 s.

8. The method for preparing the double-layered ABS and POM plastic resin striking ball for the fascia gun according to claim 4, characterized in that, In S3, the temperature of the first stage of the second injection molding machine barrel is 190 to 210°C, the temperature of the second stage is 200 to 220°C, the temperature of the third stage is 210 to 230°C, and the nozzle temperature is 215 to 235°C; the low-speed stable injection speed is 20 to 40 mm / s.

9. The method for preparing the double-layered ABS and POM plastic resin striking ball for a fascia gun according to claim 4, characterized in that, In S3, the injection pressure of the second injection molding machine is 50 to 90 MPa, the holding pressure is 40 to 70 MPa, and the holding time is 3 to 8 seconds; the surface temperature of the secondary overmolding mold is 40 to 60°C; the water cooling temperature used for cooling and curing is 20 to 30°C, and the water cooling treatment time is 15 to 20 seconds.

10. The method for preparing the double-layered ABS and POM plastic resin striking ball for a fascia gun according to claim 4, characterized in that, In S4, the semi-finished striking ball is trimmed and de-sprued to remove the sprue head and flash from the mold closing process; the parting line and fine seams of the spherical surface generated during demolding are finely polished using polishing equipment.

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