Design method of rubber part mold with metal insert and vulcanization molding process method of rubber part mold

Abstract

The invention discloses a mold design method for a rubber part with a metal insert and a vulcanization molding process method thereof.The mold preparation method comprises the steps that firstly, a three-body type mold is designed according to the rubber part and comprises an upper mold, a middle mold and a lower mold, the middle mold, the upper mold and the lower mold are jointly positioned, and the middle mold and the lower mold are provided with glue overflowing grooves; 2, calculating the size of a mold cavity; step 3, mold preparation; the upper die, the middle die and the lower die are all made of 45 # steel, and the heat treatment hardness is 35-40 HRC; the roughness of the mold cavity part is 0.4, and the roughness of the matched part of the mold is 0.8. The vulcanization molding process method comprises the steps of rubber remilling, vulcanization molding, burr cleaning and inspection. Aiming at a rubber product containing an embedded metal ring, the problems of position control of an embedded part and difficulty in mold design are solved, and the problem of batch production is solved; the optimal product performance is ensured by the optimized vulcanization forming process; the environment-friendly effect is improved, and the waste rate is reduced.

Description

Technical Field

[0001] This invention relates to the field of rubber seal preparation technology, and in particular to a method for designing a mold for a rubber part with a metal insert and a vulcanization molding process thereof. Background Technology

[0002] Rubber possesses high elasticity, wear resistance, excellent fatigue strength, and excellent electrical insulation, airtightness, water impermeability, good molding processability, and chemical stability. Rubber vulcanization refers to the process by which raw rubber undergoes a chemical reaction under specific temperature, pressure, and time conditions, resulting in cross-linking and transforming the unvulcanized rubber compound into vulcanized rubber. This process converts the chain structure into a stable network structure, achieving superior physical properties.

[0003] Rubber molds are essential process equipment for producing rubber parts. The structure, materials, dimensional tolerances, surface roughness of the cavity, and service life of rubber product molds directly affect various aspects of the rubber parts, including dimensional accuracy, product quality, and product qualification rate. Therefore, when designing molds, it is crucial to first carefully analyze and study the structural characteristics of the parts, and select a reasonable mold structure that meets the design requirements, production process requirements, and operational requirements of the mold.

[0004] A certain sealing component is made of nitrile rubber test 5171 (GJB-250A) uniformly wrapped around a metal ring with an inner diameter less than φ5, which is then vulcanized and assembled with other metal parts to achieve a good sealing and protection function. Summary of the Invention

[0005] The technical problem solved by this invention is to provide a mold design method for rubber parts with metal inserts and a vulcanization molding process method, which can efficiently and accurately realize the manufacturing of rubber parts with metal inserts.

[0006] The technical solution adopted in this invention is a method for preparing a rubber part mold with a metal insert, comprising the following steps: Step 1: Design a three-part mold based on the rubber parts, including an upper mold, a middle mold, and a lower mold. The middle mold is positioned together with the upper and lower molds, and the middle mold and the lower mold are equipped with overflow grooves. Step 2: Calculate the mold cavity dimensions. D—Dimensions of the rubber ring component; S—average vulcanization shrinkage rate of rubber (%); △—Dimensional tolerance of the finished product parts; δ—Manufacturing tolerance of the mold cavity; Let D be the mold cavity size; Then D = [ (1+S)×D ± ] ±δ (2-1) When the tolerance of the manufactured part is unidirectionally distributed and the tolerance value is positive, then take (+); When the tolerance of the manufactured part is unidirectionally distributed and the tolerance value is negative, then take (-). When the tolerance range of the manufactured parts has both positive and negative values ​​and is symmetrically distributed, then take 0; When the tolerance range of the manufactured parts has both positive and negative values ​​and is asymmetrically distributed, half of the two-way tolerance value is taken. The sign of the tolerance value is determined by the larger absolute value. δ represents the manufacturing tolerance of the mold cavity. Based on experience, δ is ±0.01 for φ3 and below; ±0.02 for φ15~φ50; ±0.03 for φ50~φ100; and ±0.01 for non-diameter dimensions.

[0007] Step 3: Mold making The dimensions of the mold cavity are controlled according to the dimensions calculated in step two; the upper mold, middle mold and lower mold are all made of 45# steel, and the heat treatment hardness is 35~40HRC; the roughness of the mold cavity is 0.4, and the roughness of the mold mating parts is 0.8.

[0008] A vulcanization molding process for rubber parts with metal inserts, using the mold prepared above, includes the following steps: rubber remelting, vulcanization molding, burr removal, and inspection. Rubber reprocessing: During reprocessing, first adjust the roller gap of the rubber rolling mill to 3mm-5mm. After the rubber material passes through the rollers four to six times and softens, adjust the roller gap to 1mm-2mm and let the rubber material pass through the rollers in a wrapping state four to six times. Then adjust the roller gap to the minimum roller gap and start thin-passing three to five times. Finally, adjust the roller gap to the required thickness and reprocess three to five times until the surface color and state of the rubber material are uniform and there are no air bubbles. Vulcanization molding: Cut the recycled rubber sheet to a width of 1mm-2mm, evenly wind it around a metal ring, place it in the mold cavity, then fill the sheet evenly, close the mold, and use a vulcanizing machine to pressurize and heat it. Within a set time, the rubber material in the cavity is formed and vulcanized. Burr removal: Use professional medical scissors to remove excess burrs; Inspection: The surface of the part should be smooth, flat and free of burrs.

[0009] The beneficial effects of this invention are that it solves the problems of controlling the position of the embedded metal ring and the difficulty of mold design for rubber products containing embedded metal rings, and solves the problem of mass production of rubber products containing embedded metal rings; it optimizes the vulcanization molding process, formulates the optimal vulcanization parameters, and ensures the best product quality and performance; it improves environmental protection efficiency, increases the first-pass yield of products, and reduces the waste rate. Attached Figure Description

[0010] Figure 1 This is a general structural diagram of the sealing component mold.

[0011] Figure 2 This is a structural diagram of the upper mold.

[0012] Figure 3 This is a structural diagram of the intermediate model.

[0013] Figure 4 This is a diagram of the lower mold structure.

[0014] Figure 5 This refers to the size and structure of the sealing assembly.

[0015] The diagram is labeled as follows: 1-Upper mold, 2-Middle mold, 3-Lower mold. Detailed Implementation

[0016] The invention will now be further described with reference to the accompanying drawings.

[0017] This application discloses a mold tooling for a rubber product containing an embedded metal ring. Due to the complex structure of the sealing component, the mold closing and opening designs are strict, and exploring the rubber shrinkage rate of the rubber product containing the embedded metal ring is of great significance.

[0018] The key processes for the vulcanization molding of rubber products with embedded metal rings in this application are: rubber remelting, vulcanization molding, and burr removal.

[0019] Re-rolling: During re-rolling, first adjust the roller gap of the rubber rolling roller to 3mm-5mm. The roller gap can be adjusted according to the amount of rubber material. After the rubber material passes through the rubber roller four to six times and softens, adjust the roller gap to (1-2)mm and let the rubber material pass through the rubber roller in a wrapped state four to six times. Then adjust the roller gap to the minimum roller gap and start thinning three to five times. Finally, adjust the roller gap to the required thickness and re-roll three to five times until the surface color and state of the rubber material are uniform and there are no air bubbles. Since the size of the sealing component is small, the rubber sheet needs to be rolled to the thinnest and without air bubbles before use.

[0020] Vulcanization molding: The process involves manually cutting the recycled rubber sheet into 1mm-2mm wide sheets, evenly winding them around a metal ring, placing them in a mold cavity, uniformly filling the sheet, and then directly using a vulcanizing machine to apply pressure and heat the material within a certain time to form and vulcanize the rubber material in the cavity, thereby obtaining a rubber product with good performance.

[0021] Burr removal: Use professional medical scissors to remove excess burrs.

[0022] I. Design of molds for sealing components Design a mold that is easy to unload, fill, and open, consisting of three parts: upper mold 1, middle mold 2, and lower mold 3. Figure 1 As shown. Specific requirements are as follows: Figure 2 For the upper mold, 45# steel is selected, with a heat treatment hardness of 35 HRC ~ 40 HRC. It includes a sealing component as the main body of the mold and a positioning and guiding structure. The design dimensions of the cavity need to be combined with the size requirements of the sealing component. Figure 3 The middle mold is made of 45# steel, which serves as the bearing and positioning material for the metal ring of the sealing component. It is positioned together with the upper and lower molds. The middle mold is equipped with an overflow groove to facilitate vulcanization molding.

[0023] Figure 4 The lower mold is made of 45# steel with a heat treatment hardness of 35 HRC ~ 40 HRC. The middle mold and the lower mold play a role in positioning and guiding. The lower mold is equipped with an overflow groove to facilitate vulcanization molding.

[0024] II. Cavity Dimension Calculation (1) The following conditions must be met for vulcanization molding to produce qualified products: 1) Ensure the finished product dimensions are within the allowable tolerance range; 2) During vulcanization, deformation and cross-linking reactions occur within the molecular chains of the rubber compound, generating thermal expansion stress. Once vulcanization is complete and the rubber compound cools, this thermal expansion stress tends to dissipate, and the linear dimensions of the rubber product shrink proportionally. The metal ring influences the rubber's shrinkage force, causing the rubber to shrink along the metal direction. Therefore, to obtain the correct dimensions of the rubber product, it is necessary to determine the machining allowance at mold opening based on the shrinkage rate, thereby determining the mold dimensions.

[0025] (2) The following factors should be considered in the design of rubber molds: 1) Rubber vulcanization shrinkage rate, hardness, rubber properties, vulcanization conditions, etc.

[0026] 2) The shape and structure of the product parts and whether there are any internal inserts.

[0027] 3) The working surface location of the product parts and their functions and requirements.

[0028] 4) Production batch requirements for finished parts.

[0029] 5) Mold structure characteristics and the size of the flash formed.

[0030] 6) Methods for filling the adhesive material and methods for demolding and removing parts, etc.

[0031] In summary, based on actual production conditions and product dimensions, the following methods are used for dimension calculation and labeling.

[0032] D=[(1+S)×D±]±δ (2-1) Where D is the mold cavity size (mm); D—Dimensions of the rubber ring component (mm); S—average vulcanization shrinkage rate of rubber (%); △—Dimensional tolerance of the finished part (mm); δ—Manufacturing tolerance of the mold cavity.

[0033] a. When the tolerance of the product part is unidirectionally distributed and the tolerance value is positive, then take (+); when the tolerance value is negative, then take (-).

[0034] b. If the tolerance range of the product parts has both positive and negative values ​​and is symmetrically distributed, then take 0.

[0035] c. If the tolerance range of the product parts has both positive and negative values ​​and is asymmetrically distributed, then half of the two-way tolerance value is taken. Its positive and negative signs are determined by the larger absolute value.

[0036] d.δ—Manufacturing tolerance of mold cavity. According to experience, δ is ±0.01 for φ3 and below, ±0.02 for φ15~φ50, and ±0.03 for φ50~φ100, which makes it easier to form and process.

[0037] For non-diameter dimensions, δ is ±0.01.

[0038] III. Tooling Dispatch The mold material is 45# steel with a hardness of 35~40HRC.

[0039] Given the dimensions of a certain sealing component as follows Figure 5 As shown, there are 5 key dimensions: dimension 1 is φ6.5, dimension 2 is 4.1, dimension 3 is 2.7, dimension 4 is 3, and dimension 5 is 0.81. All units are in mm, and the units are the same below, so they will not be specified again.

[0040] The rubber compound used is nitrile rubber test 5171 (GJB-250A), which is then applied to formula (2-1). D = [ (1 + S) × D ± ] ± δ D①=[ (1+1.8%)×(6.5)+0]±0.02 =φ6.62±0.02 (rounded to two decimal places) Similarly, we can obtain: D② = φ4.17 ± 0.02 D③=φ2.75±0.01 D④=3.05±0.01 D⑤=0.18±0.01 Workwear distribution: The upper mold, lower mold, and middle mold are made of 45# steel with a hardness of 35~40HRC. All materials are wear-resistant, corrosion-resistant, and high-hardness metals. The mold cavity roughness is 0.4, the fit of each part of the mold is 0.8, and the rest is 3.2. (The last sentence appears to be incomplete and possibly refers to a different process.) Figure 2 , Figure 3 and Figure 4 Machining of the upper mold, middle mold, and lower mold. The dimensions shown in the drawing are critical dimensions; other dimensions are determined according to the principle of matching with the finished product parts.

[0041] IV. Vulcanization Molding Process 1) Vulcanization is a complex chemical process involving multiple components, encompassing a series of chemical reactions between rubber molecules and vulcanizing agents and other compounding agents. The vulcanization molding process involves the formation of a network structure from a chain structure by rubber macromolecules under specific pressure and temperature within a certain time, thereby achieving optimal performance. The vulcanization process of this invention is as follows: rubber reprocessing → vulcanization molding → deburring → inspection.

[0042] Based on the vulcanization process of rubber and the tensile strength and tear strength properties of nitrile rubber, the vulcanization parameters of nitrile rubber test 5171 (GJB-250A) were determined as follows: (151±3)℃, 40~42min, 2~4MPa. Because the size of the metal ring has a low tolerance for mismatch with the size of the rubber part of the sealing component, the position of the metal ring is difficult to control. Therefore, during rubber remelting, the rollers of the open mill should be adjusted to the lowest position to ensure the thinnest sheet is produced. A 1-2mm thin strip is cut and wound around the metal ring, which is then placed in the middle and lower molds for matching. After filling, the molds are closed for vulcanization molding.

[0043] V. Visual inspection Inspect the surface quality of the sealing components; they should be smooth, flat, and free of burrs.

[0044] The sealing component has precise dimensions, and the fit between the embedded metal ring and the sealing component dimensions is limited, making it difficult to control the position of the metal ring. Because aerospace precision rubber products have extremely strict requirements for machining appearance standards and dimensional tolerances, the requirements for mold machining accuracy and appearance are also even more stringent. This patented mold design uses an upper-middle-lower structure. The upper mold facilitates mold opening and overflow, while the middle mold is used for positioning the metal ring and supporting the rubber part of the sealing component. This solves the problem of controlling the position of the embedded component and the difficulty of mold design for rubber products containing embedded components, and also solves the challenge of mass production of rubber parts with embedded metal rings.

Claims

1. A method for preparing a mold for a rubber part with a metal insert, comprising the following steps: Step 1: Design a three-part mold based on the rubber parts, including an upper mold, a middle mold, and a lower mold. The middle mold is positioned together with the upper and lower molds, and the middle mold and the lower mold are equipped with overflow grooves. Step 2: Calculate the mold cavity dimensions. D—Dimensions of the rubber ring component; S—average vulcanization shrinkage rate of rubber (%); △—Dimensional tolerance of the finished product parts; δ—Manufacturing tolerance of the mold cavity; Let D be the mold cavity size; Then D = [(1+S)×D±] ±δ (2-1) When the tolerance of the manufactured part is unidirectionally distributed and the tolerance value is positive, then take (+); When the tolerance of the manufactured part is unidirectionally distributed and the tolerance value is negative, then take (-). When the tolerance range of the manufactured parts has both positive and negative values ​​and is symmetrically distributed, then take 0; When the tolerance range of the manufactured parts has both positive and negative values ​​and is asymmetrically distributed, half of the two-way tolerance value is taken. The sign of the tolerance value is determined by the larger absolute value. δ represents the manufacturing tolerance of the mold cavity, and based on experience, δ is taken as ±0.01 within φ3. For φ15~φ50, δ is ±0.02; for φ50~φ100, δ is ±0.03; for non-diameter dimensions, δ is ±0.

01. Step 3: Mold making The dimensions of the mold cavity are controlled according to the dimensions calculated in step two; the upper mold, middle mold and lower mold are all made of 45# steel, and the heat treatment hardness is 35~40HRC.

2. The method for preparing a rubber part mold with a metal insert as described in claim 2, characterized in that: In step three, the roughness of the mold cavity is 0.4, and the roughness of the mating parts of the mold is 0.

8.

3. A vulcanization molding process for rubber parts with metal inserts, using the mold prepared in claim 1, comprising the following steps: rubber remelting, vulcanization molding, burr removal, and inspection; Rubber reprocessing: During reprocessing, first adjust the roller gap of the rubber rolling mill to 3mm-5mm. After the rubber material passes through the rollers four to six times and softens, adjust the roller gap to 1mm-2mm and let the rubber material pass through the rollers in a wrapping state four to six times. Then adjust the roller gap to the minimum roller gap and start thin-passing three to five times. Finally, adjust the roller gap to the required thickness and reprocess three to five times until the surface color and state of the rubber material are uniform and there are no air bubbles. Vulcanization molding: Cut the recycled rubber sheet to a width of 1mm-2mm, evenly wind it around a metal ring, place it in the mold cavity, then fill the sheet evenly, close the mold, and use a vulcanizing machine to pressurize and heat it. Within a set time, the rubber material in the cavity is formed and vulcanized. Burr removal: Use professional medical scissors to remove excess burrs; Inspection: The surface of the part should be smooth, flat and free of burrs.

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