Process for forming comber board by adopting polyformaldehyde plastic through secondary pre-injection

Abstract

The invention relates to a process for forming a comber board by adopting polyformaldehyde plastic through secondary pre-injection, which comprises the following steps of: 1, selecting polyformaldehyde plastic particles, and drying the polyformaldehyde plastic particles; 2, dried polyformaldehyde plastic particles are added into an injection molding machine and heated to be molten, molten plastic is injected into a primary injection mold for primary pre-injection, and the rough shape of a comber board is formed; 3, the comber board subjected to primary pre-injection and cooling shaping is put into a secondary injection mold, polyformaldehyde plastic particles are injected again so as to accurately fill the fine structure of the comber board, and secondary pre-injection is completed; by arranging a secondary pre-injection process, the size precision and the internal structure of the comber board are accurately controlled, so that fine parts such as meshes are more uniform and accurate; and through vacuum degassing and prolonging of the pressure maintaining time, gas in the raw materials escapes in a negative pressure environment, the gas content in the raw materials is reduced, and then generation of bubbles in the injection molding process is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of mesh board preparation technology, in particular to a technology of using polyoxymethylene plastic to pre-inject mesh boards for secondary pre-injection. Background Art

[0002] Generally speaking, secondary injection molding is used to integrate multiple functions into the same product and reduce the conventional process of assembly steps. In the existing mesh plate manufacturing process of jacquard looms, one-time injection molding or simple processing methods are usually used to manufacture the mesh plate. However, it is difficult to accurately control the dimensional accuracy and internal structure of the mesh plate by one-time injection molding, which leads to deformation and uneven aperture of the mesh plate during use, affecting its performance, high production cost and unstable product quality. Therefore, we proposed a process of using polyoxymethylene plastic to pre-inject mesh plates.

[0003] Patent number CN202410783716.7 is a Chinese invention patent, which discloses a secondary injection molding automatic production line and a secondary injection molding process, and relates to the technical field of injection molding equipment; it includes a transmission assembly line, and also includes a mold implantation module, a preheating module, an injection molding module, a handling robot module, an upper mold removal module, a material picking head module, a forced stripping module and a material unloading module arranged along the transmission assembly line; through this scheme, the degree of automation of secondary injection molding of small parts is improved, and production efficiency is improved, but the invention has the following problems: first, it does not have the improvement of increasing product precision, and it is difficult to accurately control the aperture precision and internal structure of the mesh plate; secondly, it does not have the improvement of product quality, and there are bubbles and gaps inside the mesh plate, which affects the strength and quality of the product. Summary of the invention

[0004] The purpose of the present invention is to address the shortcomings of the prior art. By setting a secondary pre-injection process, vacuum de-treatment and circulating water cooling, the present invention solves the technical problems that it is difficult to accurately control the dimensional accuracy and internal structure of the mesh plate in the one-time injection molding of the existing polyoxymethylene plastic mesh plate, resulting in the mesh plate being prone to deformation and uneven pore size during use, affecting its performance, high production cost and unstable product quality.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A process for secondary pre-injection of polyoxymethylene plastic into mesh panels comprises the following steps:

[0007] Step 1: Select polyoxymethylene plastic particles and dry them;

[0008] Step 2: Add the dried polyoxymethylene plastic particles into the injection molding machine, heat them to melt them, and inject the molten plastic into the primary injection mold for initial pre-injection to form the approximate shape of the mesh plate;

[0009] Step 3: Place the mesh plate after the initial pre-injection and cooling into the secondary injection mold, and inject polyoxymethylene plastic particles again to accurately fill the fine structure of the mesh plate to complete the secondary pre-injection;

[0010] Step 4: Post-process the mesh plate after secondary pre-injection.

[0011] As a preferred embodiment, in the step 1, polyoxymethylene plastic particles with a purity of more than 99% are selected and dried in an oven at 80° C. for 4 hours.

[0012] As a preferred embodiment, the polyoxymethylene plastic particles after drying in step 1 are subjected to vacuum degassing treatment and maintained at a vacuum degree of 0-0.09 MPa for about 30-60 minutes.

[0013] As a preference, in the step 2, the initial pre-injection temperature ranges from 180° C. to 220° C., the initial pre-injection pressure ranges from 70 MPa to 90 MPa, and the pressure holding time ranges from 8 seconds to 12 seconds.

[0014] As a preferred embodiment, in the step three, the cooling and shaping method is circulating water cooling, the temperature range is 40°C-60°C, and the cooling time range is 10 minutes-20 minutes.

[0015] As a preferred embodiment, the polyoxymethylene plastic particles injected in step three are subjected to thermal stability optimization treatment and fluidity enhancement treatment in advance, and their fluidity is improved by 15%-25% compared with the polyoxymethylene plastic particles injected for the first time.

[0016] As a preferred embodiment, in the step three, the secondary pre-injection pressure ranges from 50MPa to 70MPa, and the pressure holding time ranges from 6 seconds to 10 seconds.

[0017] Preferably, in step 4, the post-processing steps include grinding and polishing. The grinding is performed using sandpaper with a particle size of 800-1200 mesh, and the polishing is performed using a polishing device with a rotation speed of 150 rpm-2000 rpm.

[0018] Beneficial effects of the present invention:

[0019] (1) The present invention provides a secondary pre-injection process, which can accurately control the dimensional accuracy and internal structure of the mesh plate, making the mesh holes and other fine parts more uniform and accurate. Compared with the conventional process, the dimensional accuracy of the mesh plate after secondary pre-injection reaches ±0.05mm, and the mesh hole uniformity error is less than 0.02mm.

[0020] (2) In the present invention, vacuum degassing and prolonged pressure holding time are used to allow the gas inside the raw material to escape under negative pressure, thereby reducing the gas content inside the raw material and reducing the generation of bubbles during the injection molding process, thereby improving the quality of the finished product and ensuring the strength of the finished product.

[0021] (3) In the present invention, the cooling speed and temperature are precisely controlled through the cooling and shaping treatment and the post-treatment process, so as to avoid deformation of the mesh plate due to uneven cooling, effectively avoid deformation and surface defects of the mesh plate, and improve the quality stability of the mesh plate.

[0022] In summary, the invention has the advantages of simple process flow, high yield rate and good precision, and is particularly suitable for the field of mesh board preparation process technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0024] Figure 1 The figure is a schematic diagram of the overall process flow of the secondary pre-injection process for mesh panels. DETAILED DESCRIPTION

[0025] The technical solutions in the embodiments of the present invention are clearly and completely described below in conjunction with the accompanying drawings.

[0026] Embodiment 1

[0027] like Figure 1 As shown, the present invention provides a process for secondary pre-injection of polyoxymethylene plastic into mesh plates, comprising the following steps:

[0028] Step 1: Select polyoxymethylene plastic particles and dry them. Because polyoxymethylene plastic easily absorbs moisture, moisture will vaporize and form bubbles at high temperatures. The raw materials must be fully dried before injection molding to ensure that the moisture content of the raw materials is less than 0.1%, thereby reducing bubbles caused by moisture.

[0029] Step 2: Add the dried polyoxymethylene plastic particles into the injection molding machine, heat them to melt them, and inject the molten plastic into the primary injection mold for the first pre-injection to form the approximate shape of the mesh plate, but the internal structure of the mesh plate is not fine enough at this time;

[0030] Step 3: Place the template that has been initially pre-injected and cooled and shaped into the secondary injection mold, and inject polyoxymethylene plastic particles again to precisely fill the fine structure of the template, thereby completing the secondary pre-injection. The polyoxymethylene plastic with higher fluidity and filling property is used to precisely fill the fine structure of the template. Compared with the conventional process, the dimensional accuracy of the template after secondary pre-injection reaches ±0.05 mm, and the error of the pore uniformity is less than 0.02 mm.

[0031] Step 4: Perform post-treatment operations on the template after secondary pre-injection to remove surface defects, improve surface finish, and increase the yield rate.

[0032] Furthermore, in Step 1, polyoxymethylene plastic particles with a purity of over 99% are selected and dried in an oven at 80 °C for 4 hours. The polyoxymethylene plastic particles have excellent mechanical properties, excellent friction resistance and wear resistance. After sufficient drying, the bubbles generated by moisture can be reduced, further reducing the pores and voids inside the template during the initial pre-injection process, increasing the product quality, and reducing deformation.

[0033] Furthermore, the dried polyoxymethylene plastic particles in Step 1 are subjected to vacuum degassing treatment and maintained at a vacuum degree of 0 - 0.09 MPa for about 30 - 60 minutes, so that the gas inside the raw material escapes under a negative pressure environment, reducing the gas content inside the raw material, and thus reducing the generation of bubbles during the injection molding process.

[0034] Furthermore, in Step 2, the initial pre-injection temperature range is 180 °C - 220 °C, the initial pre-injection pressure range is 70 MPa - 90 MPa, and the holding pressure time range is 8 seconds - 12 seconds. The plastic melt is further compacted under the action of pressure to fill the voids that may be left due to the escape of gas. The holding pressure time can be adjusted according to the thickness and structural complexity of the template, generally extended by 5 - 10 seconds on the original basis, which helps to reduce bubbles and increase the product density.

[0035] Furthermore, in Step 3, the cooling and shaping method is circulating water cooling, the temperature range is 40 °C - 60 °C, and the cooling time range is 10 minutes - 20 minutes. A circulating water cooling system is adopted to precisely control the cooling speed and temperature to avoid deformation of the template due to uneven cooling.

[0036] Furthermore, the polyoxymethylene plastic particles injected in Step 3 are subjected to heat stability optimization treatment and fluidity enhancement treatment in advance. Its fluidity is 15% - 25% higher than that of the polyoxymethylene plastic particles during the initial pre-injection. Selecting a plastic solution with high fluidity can effectively reduce the appearance of flow marks on the surface of the template. At the beginning stage of the secondary pre-injection, the injection mold cavity is filled at a lower speed to allow the gas to escape; as the injection mold cavity is gradually filled, the injection speed is gradually increased to ensure that the plastic melt can quickly fill the remaining space of the cavity, reduce the formation of bubbles inside the template, increase the finished product density, and thus ensure the strength of the finished product.

[0037] Furthermore, in the step three, the secondary pre-injection pressure ranges from 50 MPa to 70 MPa, and the pressure holding time ranges from 6 seconds to 10 seconds. The pressure holding time is extended to effectively reduce the formation of bubbles.

[0038] Furthermore, in the step four, the post-processing process includes grinding and polishing. The grinding is performed using sandpaper with a particle size of 800-1200 mesh, and the polishing is performed using a polishing device with a rotation speed of 150 rpm-2000 rpm, which effectively avoids deformation and surface defects of the mesh board and improves the quality stability of the mesh board.

[0039] Working process: first, polyoxymethylene plastic particles with a purity of more than 99% are selected and dried; further, the dried polyoxymethylene plastic particles are added to the injection molding machine, heated to melt, and the molten plastic is injected into the primary injection mold for primary pre-injection to form the approximate shape of the mesh plate; further, the mesh plate after the primary pre-injection and cooling is placed in the secondary injection mold, and the polyoxymethylene plastic particles are injected again to accurately fill the fine structure of the mesh plate to complete the secondary pre-injection; further, the mesh plate after the secondary pre-injection is subjected to a post-processing process.

[0040] In the description of the present invention, it is necessary to understand that the directions or positional relationships indicated by the terms "front and back", "left and right", etc. are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the invention.

[0041] Of course, in the present technical solution, those skilled in the art should understand that the term "one" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element may be one, while in another embodiment, the number of the element may be multiple, and the term "one" should not be understood as a limitation on the quantity.

[0042] The above is only a preferred specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art under the technical guidance of the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A process for secondary pre-injection of polyoxymethylene plastic into mesh panels, characterized in that: The following steps are involved: Step 1: Select polyoxymethylene plastic particles and dry them; Step 2: Add the dried polyoxymethylene plastic particles into the injection molding machine, heat them to melt them, and inject the molten plastic into the primary injection mold for initial pre-injection to form the approximate shape of the mesh plate; Step 3: Place the mesh plate after the initial pre-injection and cooling into the secondary injection mold, and inject polyoxymethylene plastic particles again to accurately fill the fine structure of the mesh plate to complete the secondary pre-injection; Step 4: Post-process the mesh plate after secondary pre-injection.

2. The process of using polyoxymethylene plastic to pre-inject mesh panels according to claim 1 is characterized in that: In the step 1, polyoxymethylene plastic particles with a purity of more than 99% are selected and dried in an oven at 80° C. for 4 hours.

3. The process of using polyoxymethylene plastic to pre-inject mesh panels for secondary injection according to claim 1 is characterized in that: The polyoxymethylene plastic particles after drying in the step 1 are subjected to vacuum degassing treatment and maintained at a vacuum degree of 0-0.09 MPa for about 30-60 minutes.

4. The process of using polyoxymethylene plastic to pre-inject mesh panels for secondary injection according to claim 1 is characterized in that: In the step 2, the initial pre-injection temperature ranges from 180° C. to 220° C., the initial pre-injection pressure ranges from 70 MPa to 90 MPa, and the pressure holding time ranges from 8 seconds to 12 seconds.

5. The process of using polyoxymethylene plastic to pre-inject mesh panels for secondary injection according to claim 1 is characterized in that: In the step 3, the cooling and shaping method is circulating water cooling, the temperature range is 40° C.-60° C., and the cooling time range is 10 minutes-20 minutes.

6. The process of using polyoxymethylene plastic to pre-inject mesh panels for secondary injection according to claim 1 is characterized in that: The polyoxymethylene plastic particles injected in step three are treated in advance for thermal stability optimization and fluidity enhancement, and their fluidity is improved by 15%-25% compared with the polyoxymethylene plastic particles injected for the first time.

7. The process of using polyoxymethylene plastic to pre-inject mesh panels for secondary injection according to claim 1 is characterized in that: In the step three, the secondary pre-injection pressure ranges from 50 MPa to 70 MPa, and the pressure holding time ranges from 6 seconds to 10 seconds.

8. The process of using polyoxymethylene plastic to pre-inject mesh panels for secondary injection according to claim 1 is characterized in that: In the step 4, the post-processing process includes grinding and polishing. The grinding is performed using sandpaper with a particle size of 800-1200 mesh, and the polishing is performed using a polishing device with a rotation speed of 150 rpm-2000 rpm.

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