Injection molding method of automobile lamp injection molding part

Abstract

The invention relates to an injection molding method of an automobile lamp injection molding part, a vertical injection molding machine is adopted for injection molding, the vertical injection molding machine comprises an injection molding gun, an injection mold and a centrifugal machine used for driving the injection mold to rotate, and the injection mold is provided with an injection molding opening matched with a muzzle of the injection molding gun; when injection molding operation is carried out, a muzzle of the injection molding gun is butted and communicated with the injection molding opening; and the injection mold is driven by a centrifugal machine to rotate, and the rotating speed is 300-1500 r / min. The injection molding gun comprises a gun body and a detachable gun head, the detachable gun head comprises a cone, a spherical blending cavity is formed in the cone, a plurality of oblique injection holes passing through the blending cavity are further formed in the cone, and all the oblique injection holes intersect in the blending cavity. The centrifugal machine is additionally arranged, and the structures of the existing injection molding gun and the injection mold are optimized, so that the finally obtained automobile lamp injection molding part is high in density, few in air hole defect, high in mechanical property and high in product percent of pass.

Description

Technical Field

[0001] The invention relates to an injection molding method for an automobile lamp injection molding part, belonging to the technical field of automobile injection molding. Background Art

[0002] Most of the existing automobile lamp manufacturing is to perform further processing on the automobile lamp formed after injection molding after the shell of the automobile lamp is injection molded. The most common process is to spray the coating on the lamp formed by injection molding in conjunction with the injection molding machine.

[0003] At present, in the injection molding process of automobile lamps, especially in the field of new energy vehicles, very high requirements are placed on the flame retardant performance of lamps. Usually, in order to ensure the flame retardant performance of automobile lamps, a certain proportion of flame retardant fillers (mainly aluminum hydroxide) need to be added to the plastic masterbatch.

[0004] However, for the plastic masterbatch used in existing automotive lamps, the injection molding temperature is generally 180-300°C; and the thermal decomposition temperature of aluminum hydroxide is 200-300°C; therefore, excessive addition of aluminum hydroxide is prone to thermal decomposition at an excessively high injection molding temperature, which will cause a large number of pores to appear inside the injection molded parts. Even by increasing the injection molding pressure, the pores cannot be effectively eliminated. Instead, the pores will be concentrated on the surface of the injection molded parts. Because the moisture in the plastic melt cannot be completely volatilized, such gases in the gaps cannot be discharged during injection molding. Too many internal pores will affect the mechanical properties of the injection molded part itself; and too many surface pores will affect the subsequent coating. Therefore, when spraying the coating, if the surface pore content is not serious, grinding and polishing are usually used to eliminate some of the pores, and then spraying is performed; however, this method can only treat the symptoms, because not all pores are concentrated on the surface of the injection molded part. Grinding consumes the surface pores, and a certain degree of pores may still exist in the sub-surface layer; this results in the qualified rate of injection molded products for automotive lamp injection molded parts with high flame retardancy requirements being low.

[0005] Based on this, the present invention is proposed. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention provides an injection molding method for an automobile lamp injection molding part. The specific technical solution is as follows:

[0007] A method for injection molding an automobile lamp injection molded part comprises the following steps:

[0008] A vertical injection molding machine is used for injection molding, wherein the vertical injection molding machine comprises an injection molding gun, an injection molding mold, and a centrifuge for driving the injection molding mold to rotate, wherein the injection molding mold is provided with an injection molding port matching the muzzle of the injection molding gun, and the injection molding mold is located above the injection molding gun;

[0009] When the injection molding operation is performed, the muzzle of the injection molding gun is butted against and connected to the injection molding port; the injection molding mold is driven by the centrifuge to rotate at a speed of 300 to 1500 r / min.

[0010] A further improvement is that the injection molding gun includes a gun body and a detachable gun head, a melt chamber is arranged inside the gun body, the detachable gun head includes a cone, a spherical blending chamber is arranged inside the cone, and a plurality of oblique holes are arranged inside the cone, all of which pass through the blending chamber, the upper end of the oblique hole extends to the cone surface of the cone, the lower end of the oblique hole extends to the lower end surface of the cone and the oblique hole is connected with the melt chamber, and all the oblique holes intersect at the blending chamber.

[0011] A further improvement is that the injection mold is provided with an external docking section, and the center of the external docking section is provided with a first tapered hole connected to the injection port, a circular transition hole connected to the large end of the first tapered hole, and a second tapered hole connected to the circular transition hole in sequence from top to bottom, and the large end of the second tapered hole extends to the lower end surface of the external docking section;

[0012] When the muzzle of the injection gun is butted against the injection port, the oblique holes are all communicated with the circular transition hole.

[0013] As a further improvement, the cross-section of the oblique hole is circular, and the ratio of the diameter of the mixing chamber to the diameter of the oblique hole is (3-5):1.

[0014] A further improvement is that a wax block accommodating groove is provided on the outer periphery of the external docking section, a sealing plate is installed at the notch of the wax block accommodating groove, a slope is provided on the lower side wall of the wax block accommodating groove, the upper end of the slope extends to the notch of the wax block accommodating groove, the lower end of the slope is arranged toward the second tapered hole, a circular small hole is provided between the lower end of the slope and the hole wall of the second tapered hole, the upper end of the small hole is connected to the inner cavity of the wax block accommodating groove, and the lower end of the small hole is connected to the second tapered hole; the interior of the wax block accommodating groove is filled with wax blocks.

[0015] As a further improvement, the aperture of the small hole is 1.3-2.2 mm, the angle between the plane where the inclined surface is located and the radial direction of the second tapered hole is θ, 3°≤θ≤9°; and the length direction of the small hole is perpendicular to the plane where the inclined surface is located.

[0016] As a further improvement, the cone angle of the cone is equal to the cone angle of the second cone hole, and the cone angle of the second cone hole is equal to the cone angle of the first cone hole.

[0017] In a further improvement, the actual temperature in the melt cavity is T1, the nominal temperature in the melt cavity is T0, the actual rotation speed of the injection mold is N1, the nominal rotation speed of the injection mold is N0, the actual volume of the cavity in the injection mold is V1, the nominal volume of the cavity in the injection mold is V0,

[0018]

[0019] As a further improvement, a spherical notch portion in the shape of a spherical notch is provided at the cone head of the cone.

[0020] As a further improvement, the detachable gun head is fixedly connected to the gun body by installing bolts.

[0021] Beneficial effects of the present invention:

[0022] 1. The injection molding method of automobile lamps of the present invention is to install a centrifuge and optimize the structure of the existing injection molding gun and the injection mold, so that the automobile lamps injection molding parts finally obtained have high density, few pore defects, high mechanical properties, and significantly improved product qualification rate.

[0023] 2. The injection mold used in production does not need a core, reducing the difficulty of mold processing.

[0024] 3. The present invention is particularly suitable for the injection molding of automobile lamp injection molding parts with high flame retardancy requirements, and is particularly suitable for the injection molding production of automobile lamp injection molding parts with high flame retardant filler content. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the distribution of injection guns and injection molds in the vertical injection molding machine of the present invention;

[0026] Figure 2 It is a structural schematic diagram of the injection molding gun of the present invention;

[0027] Figure 3 It is a structural schematic diagram of the injection mold of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0029] Example 1

[0030] The injection molding method of the automobile lamp injection molding part comprises the following steps:

[0031] Use vertical injection molding machine for injection molding, such as Figures 1 to 3As shown, the vertical injection molding machine includes an injection molding gun 10, an injection molding mold 20, and a centrifuge for driving the injection molding mold 20 to rotate. The injection molding mold 20 is provided with an injection port 211 that matches the muzzle of the injection molding gun 10, and the injection molding mold 20 is located above the injection molding gun 10;

[0032] When performing the injection molding operation, the muzzle of the injection molding gun 10 is connected to and communicated with the injection molding port 211; the injection molding mold 20 is driven by the centrifuge to rotate at a speed of 300 to 1500 r / min. After the injection molding is completed, the automobile lamp injection molding part is obtained.

[0033] The vertical injection molding machine further includes a lifting mechanism for driving the injection molding gun 10 to move up and down.

[0034] To facilitate installation and disassembly, the detachable gun head is fixedly connected to the gun body 11 by installing bolts.

[0035] Before the extrusion operation, the resin masterbatch is melted, stirred and pressurized in the melt cavity 12. When the injection molding operation is performed, the muzzle of the injection molding gun 10 moves upward until the muzzle of the injection molding gun 10 is connected to the injection port 211 and communicates with each other.

[0036] The injection molding gun 10 includes a gun body 11 and a detachable gun head. A melt cavity 12 is arranged inside the gun body 11. The detachable gun head includes a cone 13. A spherical blending cavity 16 is arranged inside the cone 13. A plurality of oblique holes 15 passing through the blending cavity 16 are also arranged inside the cone 13. The upper ends of the oblique holes 15 extend to the conical surface of the cone 13, and the lower ends of the oblique holes 15 extend to the lower end surface of the cone 13. The oblique holes 15 are connected to the melt cavity 12, and all the oblique holes 15 intersect at the blending cavity 16.

[0037] Since the raw materials of the automobile lamp injection molded parts contain a large amount of aluminum hydroxide, in order to avoid uneven mixing resulting in a rough surface of the injection molded parts, a mixing cavity 16 is provided, and all the oblique holes 15 intersect in the mixing cavity 16. At the same time, the axial direction of the oblique hole 15 cannot be collinear with the axial direction of the cone 13.

[0038] The injection mold 20 is provided with an external docking section 21, and the center of the external docking section 21 is provided with a first tapered hole 212 connected to the injection port 211, a circular transition hole 213 connected to the large end of the first tapered hole 212, and a second tapered hole 214 connected to the circular transition hole 213 in sequence from top to bottom, and the large end of the second tapered hole 214 extends to the lower end surface of the external docking section 21; wherein the injection port 211, the first tapered hole 212, the circular transition hole 213 and the second tapered hole 214 are interconnected to form an injection input channel.

[0039] When the muzzle of the injection gun 10 is butted against the injection port 211 , the oblique holes 15 are all connected to the circular transition hole 213 .

[0040] The cross section of the oblique hole 15 is circular, and the ratio of the diameter of the mixing cavity 16 to the diameter of the oblique hole 15 is (3-5):1, preferably 3.7:1.

[0041] In order to ensure better mixing of the melt in the injection input channel, a spherical segment 14 in the shape of a spherical segment is provided at the cone head of the cone 13 .

[0042] The cone angle of the cone 13 is equal to the cone angle of the second cone hole 214 , and the cone angle of the second cone hole 214 is equal to the cone angle of the first cone hole 212 .

[0043] In the present invention, since the melt is subjected to a huge centrifugal force during the internal cooling and solidification process of the cavity of the injection mold 20, a large number of bubbles can be concentrated to the edge. The edge of the automotive lamp injection molded part is partly burrs, and the other part is pins corresponding to the ejection mechanism. The pins are located at the outermost part of the automotive lamp injection molded part, which will accumulate more bubbles. As a result, the bubble content of the main surface and the interior of the automotive lamp injection molded part is very low. The burrs and pins can be removed later, and have no effect on the main structure of the automotive lamp injection molded part.

[0044] 20 locations on the surface of the automotive lamp injection molded parts after injection molding are randomly selected as observation areas, and an electron microscope is used to observe whether there are pores in the observation areas. If there are pores, measure and calculate the total area of ​​the pores on the surface. The porosity = total area of ​​pores / area of ​​the observation area, and take the average value.

[0045] In this embodiment, the porosity of the surface of the automobile lamp injection molded part (the rotation speed of the injection mold 20 is 700 r / min, and polycarbonate material is used for injection molding) is 0.21‰.

[0046] As a comparison, if the existing injection molding machine, the injection mold 20 does not rotate, and the polycarbonate material is used for injection molding, and the injection molding process is the same as that of Example 1; then the porosity of the surface of the final injection molded product is 7.15%.

[0047] Example 2

[0048] In Example 1, because the sizes of the automobile lamp injection molded parts are different, the centrifugal forces required are different. After many studies, it was found that:

[0049] The actual temperature in the melt cavity 12 is T1, the nominal temperature in the melt cavity 12 is T0, the actual rotation speed of the injection mold 20 is N1, the nominal rotation speed of the injection mold 20 is N0, the actual volume of the cavity in the injection mold 20 is V1, and the nominal volume of the cavity in the injection mold 20 is V0,

[0050]

[0051] For example, in this embodiment, N0 = 700 r / min, T0 = 280°C, V0 = 1060 cm 3 , which is the benchmark. T1 and V1 are known based on the parameters of actual automotive lamp injection molding parts, so the N1 value can be calculated according to the above formula.

[0052] In addition, it should be noted that the actual rotation speed of the injection mold 20 has nothing to do with the quality of the injection molded part of the automobile lamp.

[0053] For example: T1 = 280 °C, V1 = 950 cm 3 , then N1=627r / min.

[0054] According to the mass ratio, the m0 corresponding to V0 is 1678g; m0 is the mass of one type of automobile lamp injection molded parts; and the m1 corresponding to V1 is 1396g; m1 is the mass of another type of automobile lamp injection molded parts; if the following formula is used to calculate N1 (T1=280℃), then the corresponding N1=582r / min; then the final injection molded product has a surface porosity of 1.13%.

[0055]

[0056] Example 3

[0057] In Example 1 and Example 2, since the injection mold 20 is driven by the centrifuge to rotate at a high speed, in order to reduce the friction caused by the rotation between the injection gun 10 and the injection mold 20 at the contact point between the two;

[0058] The outer periphery of the outer docking section 21 is provided with a wax block receiving groove 22, a sealing plate 24 is installed at the notch of the wax block receiving groove 22, a slope 221 is provided on the lower side wall of the wax block receiving groove 22, the upper end of the slope 221 extends to the notch of the wax block receiving groove 22, the lower end of the slope 221 is arranged toward the second tapered hole 214, a circular small hole 23 is provided between the lower end of the slope 221 and the hole wall of the second tapered hole 214, the upper end of the small hole 23 is connected to the inner cavity of the wax block receiving groove 22, and the lower end of the small hole 23 is connected to the second tapered hole 214; the wax block receiving groove 22 is filled with wax blocks. In this embodiment, the wax block is preferably microcrystalline wax with a melting point of 86 to 90°C, and the wax liquid produced by it has good lubricity.

[0059] The aperture of the small hole 23 is 1.3-2.2 mm, the angle between the plane where the inclined surface 221 is located and the radial direction of the second tapered hole 214 is θ, 3°≤θ≤9°; the length direction of the small hole 23 is perpendicular to the plane where the inclined surface 221 is located.

[0060] First, when the injection gun 10 is in contact with the injection mold 20, the high temperature of the injection gun 10 itself, which exceeds 100°C, will be transmitted to the outer docking section 21. Coupled with the frictional heat generated by the high-speed rotation, the wax block in the wax block holding groove 22 will quickly melt into wax liquid. Due to the effect of centrifugal force, an inclined surface 221 must be provided. The force exerted on the wax liquid at the upper end of the inclined surface 221 is greater than that at the lower end of the inclined surface 221. Therefore, the wax liquid can flow along the inclined surface 221 toward the small hole 23, and finally flow from the small hole 23 to the hole wall of the second tapered hole 214. Since the cone 13 and the hole wall of the second tapered hole 214 will be in close contact during injection, the wax liquid flowing out of the small hole 23 can provide lubrication for the area between the cone 13 and the second tapered hole 214 during the rotation process.

[0061] In addition, after the injection molding is completed, the injection molding gun 10 needs to move downward so as to break contact with the hole wall of the second tapered hole 214; once the injection molding gun 10, the heat source, is gone, the temperature of the injection mold 20 will drop quickly. However, the injection mold 20 is still in a high-speed rotation state at this time. At this time, because there is no heat source, the wax liquid in the wax block receiving groove 22 will solidify quickly, and the trace amount of residual wax liquid, coupled with the special design of the small hole 23, will not flow out over a large area. A small amount of wax liquid flows out to the hole wall of the second tapered hole 214, and because of the structure of the second tapered hole 214, it will not move up, and will not contaminate the circular transition hole 213.

[0062] If the small hole 23 is arranged along the axial direction of the second tapered hole 214, the wax liquid will flow out more easily from the small hole 23 during the rotation, which will cause the wax liquid to gather on the wall of the second tapered hole 214. When the wax liquid solidifies, a wax block layer of more than 5 mm will be attached to the wall of the second tapered hole 214, which may contaminate the subsequent detachable gun head.

[0063] Likewise, when the length direction of the small hole 23 is perpendicular to the wall of the second tapered hole 214, the wax block layer eventually attached to the wall of the second tapered hole 214 will be more than 10 mm thick, 100% contaminating the subsequent detachable gun tip.

[0064] The present invention adopts "the angle between the plane where the inclined surface 221 is located and the radial direction of the second tapered hole 214 is θ, 3°≤θ≤9°; the length direction of the small hole 23 is perpendicular to the plane where the inclined surface 221 is located." With this arrangement, the thickness of the wax block layer attached to the hole wall of the second tapered hole 214 does not exceed 1mm, and will not contaminate the subsequent detachable gun head. In addition, the residual trace wax block layer can serve as a lubricant during the second injection molding operation.

[0065] Since the rotation speed of the injection mold 20 is 300-1500 r / min, according to the range of the rotation speed, after a large number of tests, preferably, the aperture of the small hole 23 is 1.3-2.2 mm.

[0066] If the inclined surface 221 is not provided but a flat structure is used, when the height of the wax liquid layer in the wax block containing groove 22 is lower than 5 cm, uneven lubrication will occur. When the rotation speed exceeds 1000 r / min, the wear amount will be large and friction sparks will occasionally appear.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for injection molding of automotive lamp injection molding parts, It is characterized in that The following steps are involved: A vertical injection molding machine is used for injection molding, the vertical injection molding machine comprising an injection molding gun (10), an injection molding mold (20), and a centrifuge for driving the injection molding mold (20) to rotate, the injection molding mold (20) being provided with an injection molding port (211) matching the muzzle of the injection molding gun (10), and the injection molding mold (20) being located above the injection molding gun (10); When the injection molding operation is performed, the muzzle of the injection molding gun (10) is docked with and connected to the injection molding port (211); the injection molding mold (20) is driven by the centrifuge to rotate at a speed of 300 to 1500 r / min.

2. The method for molding an automobile lamp molded part according to claim 1, Features: The injection molding gun (10) comprises a gun body (11) and a detachable gun head, wherein a melt cavity (12) is arranged inside the gun body (11), and the detachable gun head comprises a cone (13), wherein a spherical blending cavity (16) is arranged inside the cone (13), and wherein a plurality of oblique holes (15) are arranged inside the cone (13) and all of which pass through the blending cavity (16), wherein the upper ends of the oblique holes (15) extend to the conical surface of the cone (13), and the lower ends of the oblique holes (15) extend to the lower end surface of the cone (13), and the oblique holes (15) are connected to the melt cavity (12), and all of the oblique holes (15) intersect at the blending cavity (16).

3. The method for molding an automobile lamp molded part according to claim 2, Features: The injection mold (20) is provided with an external docking section (21), and the center of the external docking section (21) is provided with a first tapered hole (212) connected to the injection port (211), a circular transition hole (213) connected to the large end of the first tapered hole (212), and a second tapered hole (214) connected to the circular transition hole (213) in sequence from top to bottom, and the large end of the second tapered hole (214) extends to the lower end surface of the external docking section (21); When the muzzle of the injection gun (10) is butted against the injection port (211), the oblique holes (15) are all in communication with the circular transition hole (213).

4. The method for molding an automobile lamp molded part according to claim 2, Features: The cross section of the oblique hole (15) is circular, and the ratio of the diameter of the mixing cavity (16) to the diameter of the oblique hole (15) is (3-5):

1.

5. The method for molding an automobile lamp molded part according to claim 3, Features: A wax block receiving groove (22) is arranged on the outer periphery of the outer docking section (21), a sealing plate (24) is installed at the notch of the wax block receiving groove (22), a slope (221) is arranged on the lower side wall of the wax block receiving groove (22), the upper end of the slope (221) extends to the notch of the wax block receiving groove (22), the lower end of the slope (221) is arranged toward the second tapered hole (214), a circular small hole (23) is arranged between the lower end of the slope (221) and the hole wall of the second tapered hole (214), the upper end of the small hole (23) is communicated with the inner cavity of the wax block receiving groove (22), and the lower end of the small hole (23) is communicated with the second tapered hole (214); the wax block receiving groove (22) is filled with wax blocks.

6. The method for molding an automobile lamp molded part according to claim 5, Features: The aperture of the small hole (23) is 1.3-2.2 mm, the angle between the plane where the inclined surface (221) is located and the radial direction of the second tapered hole (214) is θ, 3°≤θ≤9°; the length direction of the small hole (23) is perpendicular to the plane where the inclined surface (221) is located.

7. The method for molding an automobile lamp molded part according to claim 5, Features: The cone angle of the cone (13) is equal to the cone angle of the second cone hole (214), and the cone angle of the second cone hole (214) is equal to the cone angle of the first cone hole (212).

8. The method for molding an automobile lamp molded part according to claim 2, Features: The actual temperature in the melt chamber (12) is T 1 The nominal temperature in the melt chamber (12) is T 0 , the actual rotation speed of the injection mold (20) is N 1 The nominal rotation speed of the injection mold (20) is N 0 The actual volume of the inner cavity of the injection mold (20) is V 1 The nominal volume of the inner cavity of the injection mold (20) is V 0 , 9. The method for molding an automobile lamp molded part according to claim 2, Features: A spherical segment-shaped spherical segment portion (14) is provided at the cone head of the cone (13).

10. The method for molding an automobile lamp molded part according to claim 2, Features: The detachable gun head is fixedly connected to the gun body (11) via mounting bolts.

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