A binder for powder injection molding, a method and an apparatus for hot cutting in a powder injection molding mold

Abstract

The present application provides a kind of powder injection molding binder, powder injection molding in-mold hot cutting method and device, the binder includes 20~40 parts of high melting point skeleton polymer, melting point is 120~190 ℃;10~35 parts of low melting point phase, melting point is 50~80 ℃;10~25 parts of high melting point microcrystalline wax, melting point is 80~100 ℃;1~10 parts of lubricant;0.5~8 parts of self-lubricating wear-reducing modifier, form three gradient melting point ladder structure, make the gate area preferentially soften in hot cutting process and the main body of product keeps strength.In-mold hot cutting method is through monitoring cavity pressure change, combined with cutter heating and cooling control, when the gate binder is in suitable softening state, cutting is carried out, can reduce the gate residue and product deformation, improve cutter durability and forming efficiency, suitable for the manufacture of metal and ceramic powder injection molding parts.

Description

Technical Field

[0001] This invention relates to the field of powder injection molding technology, and in particular to a binder for powder injection molding, a method and apparatus for in-mold thermal cutting in powder injection molding. Background Technology

[0002] Powder injection molding (PIM) is an advanced manufacturing process that uses a mixture of powder materials and a binder to create complex-shaped parts through injection molding, debinding, and sintering. It is widely used in the manufacture of precision parts. In this technology, the binder acts as a temporary carrier, playing a crucial role in imparting flowability to the powder and maintaining the final shape during the molding process.

[0003] However, existing powder injection molding technology still has the following problems: First, in traditional processes, after the product is molded, it needs to be separated from the gate manually or by subsequent mechanical processing. This extra step significantly reduces production efficiency, especially for small and complex parts produced in batches, where efficiency losses can reach more than 30%. Second, manual separation or mechanical processing can easily lead to edge damage and dimensional deviations in the product, reducing the product qualification rate by 10%-15%. Third, gate residues require secondary treatment, which not only reduces the utilization rate of powder materials by 5%-8%, but may also generate dust pollution during the processing. Finally, existing in-mold hot cutting technology for plastics does not fully consider the high viscosity and high hardness characteristics of powder materials. When directly applied to powder injection molding, it is easy to cause problems such as cutter wear and binder residue blockage.

[0004] Therefore, there is an urgent need for an in-mold gate hot-cutting collaborative control scheme that is suitable for powder injection molding, which can reduce post-processing steps and improve production efficiency and yield while ensuring the structural strength and surface quality of the product. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a binder for powder injection molding, a method and apparatus for in-mold hot cutting in powder injection molding, to solve the problems of low production efficiency, poor product precision, material waste and insufficient compatibility in the separation process of products and gates in existing powder injection molding processes.

[0006] To achieve the above and other related objectives, the present invention provides the following technical solutions: A first aspect of the present invention provides a binder for powder injection molding, comprising the following components in parts by weight: 20-40 parts of a high-melting-point backbone polymer with a melting point of 120-190℃; 10-35 parts of the low-melting-point phase, with a melting point of 50-80℃; 10-25 parts of high-melting-point microcrystalline wax, with a melting point of 80-100℃; 1 to 10 parts of lubricant; 0.5 to 8 parts of self-lubricating friction-reducing modifier.

[0007] Furthermore, the high-melting-point backbone polymer is selected from one or more of high-density polyethylene (HDPE), polypropylene (PP), polycaprolactam (PA6), and polydodecanoic acid (PA12).

[0008] Furthermore, the low-melting-point phase is selected from low-melting-point polymers and / or low-melting-point paraffins.

[0009] Furthermore, the low-melting-point polymer is selected from one or more of polyethylene glycol (PEG), ethylene-vinyl acetate copolymer (EVA), polyvinyl butyral (PVB), and polyethylene oxide (PEO).

[0010] Furthermore, the lubricant is selected from stearic acid, zinc stearate, or a combination thereof.

[0011] Furthermore, the friction-reducing modifier is selected from boron nitride (BN), graphite, or ethylene bis-stearamide (EBS).

[0012] This invention employs a binder system with a three-stage melting point ladder structure. During the hot cutting process, the high-melting-point backbone polymer provides overall support strength, while the low-melting-point phase softens rapidly at the gate and reduces cutting force, thus achieving "soft gate and firm product". The high-melting-point microcrystalline wax migrates and accumulates more easily on the surface of the gate and runner during injection, enhancing cutability. The three gradient melting point components work synergistically to reduce cutting load by 20-30%, tool wear by 25-35%, and produce a smooth fracture without powder exposure. Soluble phases such as PEG are preferentially dissolved, reducing sintering defects, thereby significantly improving molding efficiency and product quality. It is particularly suitable for powder injection molding of metal or ceramic parts.

[0013] A second aspect of the present invention provides a method for in-mold thermal cutting in powder injection molding, comprising the following steps: S1. The molding powder and binder are put into the internal mixer and heated and mixed. The uniformly mixed feed is then passed through a granulator to obtain granules. S2. Inject the pellet feed into the mold cavity, allowing the feed to fill the cavity and solidify and set during the pressure holding stage; S3. After the pressure holding is completed, the pressure change in the cavity is obtained in real time based on the pressure sensor set inside the cavity. When the cavity pressure drops to the preset pressure threshold, the heating module is activated to preheat the cutting blade assembly to the first temperature range. S4. Move the preheated cutter assembly to a position close to the gate and stop, start the timer and maintain it for the preset time; this will allow the adhesive in the gate area to soften preferentially. S5. When the timing reaches the preset delay, the cutter assembly is driven to cut off the gate. After the cutter assembly cuts off the gate, it continues to remain at the cut-off position for a period of time, and the temperature of the cutter assembly is reduced to the second temperature range through the cooling module. Then the cutter assembly is reset and exited. S6. After the gate is cut off, open the mold and eject the product.

[0014] The first temperature range is higher than the melting point of the low-melting-point phase in the binder, but not higher than the melting point of the high-melting-point backbone polymer. This temperature setting ensures that the binder in the gate area is appropriately softened for easy cutting, without affecting the hardness and shape stability of the product body.

[0015] In step S1, the volume ratio of the molding powder in the feed is 50-65%.

[0016] In step S1, the mixing temperature is higher than the melting point of the high melting point skeletal polymer, the mixing temperature is 140-200°C, and the mixing time is 30-120 min.

[0017] In step S2, the granules are fed into the mold cavity using an injection molding machine. The injection pressure is 80~150MPa, the barrel temperature is 150~220℃, and the holding time is 5~15s.

[0018] In step S3, the preset pressure threshold is 5~12MPa.

[0019] In step S3, the first temperature range is 80~180℃, preferably 90~130℃.

[0020] In step S4, the preset delay is 0.5~2.0 s.

[0021] In step S5, the PLC controller triggers the drive unit, causing the cutter assembly to cut off the gate at a speed of 50~100mm / s. In step S5, after the cutter assembly cuts off the gate, it remains at the cut position for 0.3 to 1.0 seconds to ensure complete separation.

[0022] In step S5, the second temperature range is not higher than 80°C.

[0023] In step S6, the moving mold opens, and the product and gate are ejected by the ejection mechanism and directly enter the degreasing process without additional separation treatment.

[0024] A third aspect of the present invention provides an in-mold heat-cutting device for powder injection molding, comprising: The mold body consists of a fixed mold and a moving mold, forming a cavity between the fixed mold and the moving mold that corresponds to the shape of the product, as well as a main runner and a gate channel connecting the cavity. A pressure sensor is installed inside the cavity to collect the cavity pressure. A hot-cutting mechanism is located at the connection between the gate channel and the cavity. The hot-cutting mechanism includes a cutter assembly, a drive module, a heating module, and a cooling module. The heating module is used to heat the cutter assembly to a set temperature range. The cooling module is used to quickly reduce the temperature of the cutter. The drive module is used to drive the cutter assembly to move towards the gate. The PLC controller is used to determine the window for triggering the cutter action based on the pressure curve collected by the pressure sensor and to control the cutter temperature and stroke in a closed loop.

[0025] Furthermore, the heating module is installed circumferentially on the cutting assembly, and the heating module includes an annular resistance heating element and a thermocouple temperature controller. The temperature is monitored in real time by the thermocouple, and the temperature control range is 80~180℃ (adapted to the softening point of different adhesives).

[0026] Furthermore, the cooling module is a spiral cooling water channel arranged around the cutter assembly, which controls the working temperature of the cutter by cooling water (flow rate of 5-10L / min) to prevent the adhesive from carbonizing due to high temperature.

[0027] Furthermore, the cutting blade assembly is made of cemented carbide, such as WC-Co alloy, with a cutting edge angle of 30~45°, adapted to the high hardness characteristics of powder materials. The surface of the cutting blade has an anti-adhesion coating.

[0028] Furthermore, the drive module is a servo electric cylinder or a hydraulic cylinder, and the response time of the drive module does not exceed 50ms.

[0029] As described above, the powder injection molding binder, the powder injection molding in-mold hot cutting method and apparatus of the present invention have the following beneficial effects: 1. This invention employs a binder system with a three-stage melting point ladder structure. During the hot cutting process, the high-melting-point skeleton polymer provides overall support strength, while the low-melting-point phase softens rapidly at the gate and reduces the cutting force, thus achieving the characteristics of "soft gate and firm product". The high-melting-point microcrystalline wax migrates and accumulates more easily on the surface of the gate and runner during injection, enhancing cutability. The three gradient melting point components work synergistically to reduce the cutting load by 20-30%, reduce tool wear by 25-35%, and produce a smooth fracture without powder exposure. Soluble phases such as PEG are preferentially dissolved, reducing sintering defects, thereby significantly improving molding efficiency and product quality. It is particularly suitable for powder injection molding of metal or ceramic parts.

[0030] 2. This invention precisely adapts to the softening window, controlling the cutting temperature between the melting points of the low-melting-point phase and the high-melting-point skeleton, thus preferentially softening the gate area while maintaining the strength of the main body of the product, resulting in a smooth fracture and significantly reduced risk of deformation. Hot cutting only occurs at the easiest cutting stage, avoiding excessive friction / charring and improving tool life and mold stability. In-mold cutting eliminates the need for secondary cutting, shortening the production cycle by 20-30% and achieving a yield of ≥99%.

[0031] 3. This invention is based on real-time feedback of cavity pressure to trigger execution, automatically adapting to different feeding batches, wall thicknesses, and temperature fluctuations, improving process robustness and finished product consistency. It is suitable for injection molding of metal (such as 316L stainless steel, titanium alloy) and ceramic (such as alumina, silicon nitride) powders. The entire process is automatically controlled through a sensing and control system, reducing manual intervention and labor intensity. Attached Figure Description

[0032] Figure 1 The diagram shown is a schematic representation of the in-mold hot-cutting device for powder injection molding disclosed in an embodiment of the present invention.

[0033] Component designation explanation 1. Front mold core; 2. Product; 3. Rear mold core; 4. Sprue channel; 5. Cutter; 6. Heating element; 7. Cutting seat; 8. Cooling water channel; 9. Servo electric cylinder; 10. Thermocouple; 11. PLC controller. Detailed Implementation

[0034] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. It should be noted that, unless otherwise specified, the following embodiments and features described herein can be combined with each other.

[0035] Example 1 This embodiment provides a binder for powder injection molding, comprising the following components in parts by weight: 30 parts HDPE, melting point 130℃; 25 parts of low-melting-point paraffin wax, melting point 58℃; 10 parts of EVA have a melting point of 75°C; 20 parts of high-melting-point microcrystalline wax, melting point 88℃, viscosity 20 mPa·s; 8 parts stearic acid; 7 parts BN ultrafine powder.

[0036] The adhesive is prepared by the following method: HDPE, EVA, and microcrystalline wax were added to a mixer and mixed at 140°C and 100 rpm for 15 minutes. Then, paraffin wax and stearic acid were added and mixed at 130°C and 100 rpm for 20 minutes to ensure that all the molten phases were mixed evenly. Then, BN powder was added and mixed at 120°C and 80 rpm for 25 minutes to ensure uniform dispersion. Finally, the mixture was cooled and granulated to obtain binder particles with a particle size of 3 mm.

[0037] Example 2 This embodiment provides a method for in-mold thermal cutting in powder injection molding, including the following steps: S1. 316L stainless steel powder (D50≈10μm) with a volume ratio of 62:38 and the binder of Example 1 are put into a mixer and heated and mixed at 150°C for 45 minutes. The uniformly mixed feed is then passed through a granulator to obtain 3mm granules. S2. The pellet feed is injected into the mold cavity through the injection molding machine. The injection temperature is 150~160℃, the injection pressure is 130MPa, and the mold temperature is 45~50℃. The feed fills the cavity and solidifies and sets during the pressure holding stage. The pressure holding pressure is 80MPa and the pressure holding time is 10s. S3. After the pressure holding is completed, the pressure change in the cavity is obtained in real time based on the pressure sensor installed inside the cavity. When the cavity pressure drops to 7MPa, the heating module is activated to preheat the cutting blade assembly to 110±5℃. S4. Move the preheated cutter assembly to a position close to the gate and stop. Start the timer and hold for 1.0s to allow the adhesive in the gate area to soften preferentially. S5. After the timer reaches 1.0s, the cutter assembly (cutting speed 70mm / s) is driven to cut off the gate. After the cutter assembly cuts off the gate, it continues to stay at the cut position for 0.3s, and the temperature of the cutter assembly is reduced to below 70℃ by the cooling module (20℃ circulating water, flow rate 7L / min). Then the cutter assembly is reset and exited. S6. After the gate is cut off, open the mold and eject the product.

[0038] The product was tested and found to have a cutting load of 45N, a smooth cutting edge, a gate residual height of ≤0.08mm, and no curling or dents; the through hole position error was ≤0.05mm, which meets the assembly requirements of communication equipment. The batch production (1000 pieces) achieved a pass rate of 99.5%, which is 7.5% higher than the traditional manual separation process (pass rate 92%). The single-mold production cycle was shortened from 45s to 32s, efficiency was improved by 28.9%, and material utilization was increased by 7.2% (reduced gate waste).

[0039] Example 3 This embodiment provides a binder for powder injection molding, comprising the following components in parts by weight: 40 parts of PA12 have a melting point of 178°C; 30 parts of PEG-4000, melting point 60℃; 15 parts of high-melting-point microcrystalline wax, melting point 90℃; 5 parts stearic acid; 5 parts zinc stearate; 3 portions of EBS.

[0040] The adhesive is prepared by the following method: PA12, EBS, and microcrystalline wax were added to a mixer and mixed at 185°C and 100 rpm for 20 min. Then, PEG, stearic acid, and zinc stearate were added and mixed at 160°C and 80 rpm for 25 min to ensure that the molten phase was fully mixed. After cooling, the mixture was granulated to obtain binder particles with a particle size of 3 mm.

[0041] Example 4 This embodiment provides a method for in-mold thermal cutting in powder injection molding, including the following steps: S1. Alumina ceramic powder (D50≈2.5μm) with a volume ratio of 60:40 and the binder of Example 3 are put into a mixer and heated and mixed at 180°C for 50 minutes. The uniformly mixed feed is then passed through a granulator to obtain 3mm granules. S2. The granules are injected into the mold cavity through the injection molding machine. The injection temperature is 170~180℃, the injection pressure is 95~115MPa, and the mold temperature is 55℃. The granules fill the cavity and solidify during the holding pressure stage. The holding pressure is 70MPa and the holding time is 12s. S3. After the pressure holding is completed, the pressure change in the cavity is obtained in real time based on the pressure sensor set inside the cavity. When the cavity pressure drops to 5MPa, the heating module is activated to preheat the cutting blade assembly to 155±5℃. S4. Move the preheated cutter assembly to a position close to the gate and stop. Start the timer and hold for 1.5 seconds to allow the adhesive in the gate area to soften preferentially. S5. After the timer reaches 1.5s, the cutter assembly (cutting speed 60mm / s) is driven to cut off the gate. After the cutter assembly cuts off the gate, it continues to stay in the cutting position for 0.8s, and the temperature of the cutter assembly is reduced to below 80℃ by the cooling module (20℃ circulating water, flow rate 7L / min). Then the cutter assembly is reset and exited. S6. After the gate is cut off, open the mold and eject the product.

[0042] Testing revealed that the product has a cutting load of 39N, a smooth cutting edge, a sintering crack rate of 1.2%, a gate residual height of 0.1mm, and a material utilization rate that is 8.5% higher, making it suitable for medical implant applications.

[0043] Example 5 This embodiment provides an in-mold hot-cutting device for powder injection molding, which can be applied to the above embodiments. It includes three main parts: mold body, hot-cutting mechanism and PLC controller.

[0044] The mold body consists of a fixed mold and a moving mold. The fixed mold and the moving mold each include a front mold core 1 and a rear mold core 3 embedded within them. A cavity corresponding to the shape of the product 2 is formed between the front and rear mold cores, along with a main runner and a gate channel 4 connecting the cavity. A pressure sensor is installed inside the cavity to collect pressure changes. The pressure sensor can monitor the pressure changes inside the cavity in real time, providing a precise triggering timing for the subsequent hot-cutting process.

[0045] The hot cutting mechanism is located at the connection between the gate channel and the mold cavity, and mainly consists of four parts: a cutting blade assembly, a drive module, a heating module, and a cooling module. The cutting blade assembly includes a cutting blade 5 and a cutting seat 7. The cutting blade 5 moves along the channel within the cutting seat 7 to avoid misalignment. The cutting blade is made of cemented carbide, specifically WC-Co alloy, with a cutting edge angle designed to be 30~45°, a design particularly suitable for the high hardness characteristics of powder materials. The cutting blade surface also has an anti-adhesion coating, effectively preventing powder materials from adhering to the blade surface during cutting.

[0046] The heating module is installed circumferentially on the cutter assembly and mainly includes an annular resistance heating element 6 and a thermocouple 10. The temperature of the cutter is monitored in real time by the thermocouple 10, and the temperature control range is 80~180℃, which can be adjusted according to the softening point of different binders. In a preferred embodiment, the temperature control range is preferably 90~130℃. This temperature range ensures that the cutter temperature is higher than the melting point of the low-melting-point phase in the binder, while not exceeding the melting point of the high-melting-point backbone polymer, achieving the effect of "soft gate and firm product".

[0047] The cooling module consists of a spiral cooling water channel 8 arranged around the cutter assembly. The cooling water flow rate is controlled at 5~10L / min, and the working temperature of the cutter is controlled through cooling water circulation to prevent the binder from carbonizing due to high temperature. The cooling module can quickly reduce the temperature of the cutter to a second temperature range not exceeding 80℃ after the gate is cut off, ensuring rapid cooling and solidification of the gate area after the cut-off.

[0048] The drive module uses a servo electric cylinder 9, with a response time of no more than 50ms. The drive module can precisely control the movement speed and position of the cutter. Under the command of the PLC controller, the drive cutter cuts the gate at a speed of 50~100mm / s, and continues to maintain the cut position for 0.3~1.0s after cutting to ensure complete separation of the gate from the product.

[0049] The PLC controller 11 is the core control unit of the entire hot cutting device. It is used to determine the window for triggering the cutter action based on the pressure curve collected by the pressure sensor and to control the cutter temperature and stroke in a closed loop. The PLC controller monitors the cavity pressure change. When the pressure drops to the preset pressure threshold (5~12MPa), it starts timing. When the timing reaches the preset delay (0.5~2.0s), it controls the trigger heating module to heat the cutter to the first temperature range. Then, it drives the cutter assembly to cut off the gate. After cutting off, it starts the cooling module to reduce the cutter temperature. Finally, it controls the cutter assembly to reset.

[0050] The entire process of the device is as follows: First, the granules are injected into the mold cavity at an injection pressure of 80~150MPa and a barrel temperature of 150~220℃, with a holding time of 5~15s. After the holding time is completed, the pressure sensor monitors the cavity pressure change in real time. When the pressure drops to the preset threshold, the PLC controller starts timing. After the preset delay is reached, the PLC controller starts the heating module to preheat the cutter. After the cutter reaches the set temperature, the drive module drives the cutter assembly to cut off the gate. After cutting off, the cutter is held in the cutting position for a period of time, while the cooling module lowers the cutter temperature. Finally, the cutter assembly is reset, the mold is opened, and the product is ejected.

[0051] This hot-cutting device enables automatic thermal cutting of the gate during powder injection molding, avoiding product damage and powder exposure problems that may occur with traditional manual gate cutting, thus improving production efficiency and product quality. The temperature control of the hot-cutting mechanism preferentially softens the binder in the gate area, reducing cutting force and tool wear, while ensuring the strength of the product body and achieving perfect separation between the gate and the product.

[0052] Comparative Example 1 Compared with Example 2, the only difference is that the adhesive includes 30 parts of polyethylene, 25 parts of paraffin wax, and 8 parts of stearic acid.

[0053] The product was tested and found to have a cutting load of 62N, a residual gate height of 0.21mm, and a dimensional compliance rate of 92.3%.

[0054] Comparative Example 2 The only difference from Example 4 is that the adhesive is a commercially available polyamide adhesive.

[0055] The product was tested and found to have a cutting load of 50N, a residual gate height of 0.25mm, obvious exposed surface of the cut edge, and a sintering cracking rate of 5.6%.

[0056] In summary, this invention, by forming a three-gradient melting point ladder structure, preferentially softens the gate area during hot cutting while maintaining the strength of the main body of the product. The in-mold hot cutting method, by monitoring changes in cavity pressure and combining this with cutter heating and cooling control, cuts the gate when the binder is in a suitable softened state. This reduces gate residue and product deformation, improves cutter durability and molding efficiency, and is suitable for manufacturing metal and ceramic powder injection molded parts. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.

[0057] The terms used in this specification, such as "upper," "lower," "left," "right," "front," "back," "middle," and "one," are merely for clarity of description and are not intended to limit the scope of the invention. Any changes or adjustments to their relative relationships, without substantially altering the technical content, shall also be considered within the scope of the invention.

[0058] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. All equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this invention should still be covered by the claims of this invention.

Claims

1. A method for in-mold thermal cutting in powder injection molding, characterized in that, Includes the following steps: S1. The molding powder and binder are put into the internal mixer and heated and mixed. The uniformly mixed feed is then passed through a granulator to obtain granules. The adhesive comprises the following components in parts by weight: 20-40 parts of a high-melting-point backbone polymer, wherein the high-melting-point backbone polymer has a melting point of 120-190°C, and the high-melting-point backbone polymer is selected from one or more of HDPE, PP, PA6, and PA12; 10-35 parts of a low-melting-point phase, wherein the melting point of the low-melting-point phase is 50-80°C, and the low-melting-point phase is selected from low-melting-point polymers and / or low-melting-point paraffin; wherein the low-melting-point polymer is selected from one or more of PEG, EVA, PVB, and PEO; 10-25 parts of high-melting-point microcrystalline wax, wherein the melting point of the high-melting-point microcrystalline wax is 80-100℃; 1 to 10 parts of lubricant; 0.5 to 8 parts of a self-lubricating friction-reducing modifier, wherein the self-lubricating friction-reducing modifier is selected from boron nitride, graphite or ethylene bis-stearamide; S2. Inject the pellet feed into the mold cavity, allowing the feed to fill the cavity and solidify and set during the pressure holding stage; S3. After the pressure holding is completed, the pressure change in the cavity is acquired in real time based on the pressure sensor installed inside the cavity. When the cavity pressure drops to a preset pressure threshold, the heating module is activated to preheat the cutter assembly to a first temperature range. The preset pressure threshold is 5~12MPa, and the first temperature range is higher than the melting point of the low melting point phase and not higher than the melting point of the high melting point skeletal polymer. S4. Move the preheated cutter assembly to a position close to the gate and stop it. Start the timer and maintain the preset delay, which is 0.5~2.0s, so that the adhesive in the gate area softens preferentially. S5. When the timing reaches the preset delay, the cutter assembly is driven to cut off the gate. After cutting off the gate, the cutter assembly continues to remain at the cutting position for 0.3~1.0s, and the temperature of the cutter assembly is reduced to the second temperature range through the cooling module. The second temperature range is not higher than 80℃. Then the cutter assembly is reset and exited. S6. After the gate is cut off, open the mold and eject the product.

2. The method according to claim 1, characterized in that, The lubricant is selected from stearic acid, zinc stearate, or a combination thereof.

3. The method according to claim 1, characterized in that, In step S1, the mixing temperature is higher than the melting point of the high melting point skeletal polymer, the mixing temperature is 140-200°C, and the mixing time is 30-120 min.

4. The method according to claim 1, characterized in that, In step S3, the first temperature range is 80~180℃.

5. A powder injection molding in-mold heat cutting device, used in the powder injection molding in-mold heat cutting method as described in any one of claims 1 to 4, characterized in that, include: The mold body consists of a fixed mold and a moving mold, forming a cavity between the fixed mold and the moving mold that corresponds to the shape of the product, as well as a main runner and a gate channel connecting the cavity. A pressure sensor is installed inside the cavity to collect the cavity pressure. A hot-cutting mechanism is located at the connection between the gate channel and the cavity. The hot-cutting mechanism includes a cutter assembly, a drive module, a heating module, and a cooling module. The heating module is used to heat the cutter assembly to a set temperature range. The cooling module is used to quickly reduce the temperature of the cutter. The drive module is used to drive the cutter assembly to move towards the gate. The PLC controller is used to determine the window for triggering the cutter action based on the pressure curve collected by the pressure sensor and to control the cutter temperature and stroke in a closed loop.

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