An optimization method to improve the injection molding precision of optical components

Abstract

The invention discloses an optimization method for improving the injection molding precision of optical elements. Under the premise that injection molding process parameters and the like are all optimal, an injection molding process that takes into account the melt material and the surface roughness of a mold core is proposed, different mold core surface roughness intervals are selected according to different melt materials, and the mold core processing process is optimized based on an existing ultra-precision machining quality prediction model. Compared with the extremely high quality requirements for the mold core surface in traditional methods, the optimization method for improving the injection molding precision of optical elements in the invention improves the molding precision of optical elements and reduces their surface roughness on the basis of improving the mold core processing efficiency, which is helpful for optimizing the micro-injection molding process of optical elements and improving the optical performance of the elements.

Description

Technical Field

[0001] The invention relates to the technical field of micro-injection molding, and in particular to an optimization method for improving the injection molding precision of optical elements. Background Art

[0002] At present, micro injection molding technology: through more advanced equipment, strict control of process parameters, environmental variables and dimensional control, etc., to process optical components with high surface quality (surface roughness, shape accuracy) and optical performance. The biggest feature is that the injection volume is small, the core and molded parts have small geometric dimensions, and the requirements for injection molding process parameter control and core quality are high.

[0003] At present, the research on micro injection molding mainly stays on the exploration of its injection molding process, such as injection speed, melt temperature, holding pressure, mold temperature, holding time, etc. The order of influence is generally considered to be cooling time>melt temperature>injection speed>holding time>mold temperature>holding pressure. Its theoretical research mainly focuses on the scale effect and convection heat transfer behavior of polymer melts. It is necessary to consider the properties of injection molding materials, gravity, adhesion, surface tension, etc. during the injection molding process, which will have a certain impact on micro injection molding parts due to size effects.

[0004] Existing technologies generally focus on the optimization of the injection molding process. It is generally believed that the following requirements need to be met to control the injection molding process:

[0005] Higher injection speed: Higher injection speed can improve filling rate and reduce shrinkage. But the higher the better, there is an injection speed with the best filling rate.

[0006] Higher injection pressure: ensures the filling rate of the microstructure inside the melt cavity. High injection pressure can make the shear stress of the melt in the channel and cavity much higher than the critical shear stress of the polymer material for wall slip. It can increase the slip of the melt and the wall in the channel and core, which can increase the filling rate in the channel on the one hand, but on the other hand, it will cause the surface roughness of the injection molded part to increase.

[0007] Higher mold temperature: Before and during injection molding, the mold is quickly processed to a certain temperature. For amorphous polymers (such as ABS, PMMA, PC, PSU, etc.), the temperature standard is higher than the glass transition temperature of the material. For crystalline polymers (such as POM, PA, etc.), the mold temperature needs to reach the melting point of the material. After the injection is completed, it is slowly cooled to the demolding temperature.

[0008] Therefore, the existing method for controlling the injection molding accuracy of optical components is:

[0009] Step 1: Optical component design: Optical design is carried out according to the required optical performance, including: component geometric feature design, optical performance design and component accuracy requirements determined by the performance; molded parts accuracy requirements are proposed based on optical performance, including geometric errors and surface roughness.

[0010] Step 2: Processing, including core processing and injection molding:

[0011] (1) Ultra-precision machining of mold cores: Select the mold core material, select the ultra-precision machining method according to the geometric characteristics and accuracy requirements of the optical design, and then plan the ultra-precision machining process of the mold core based on the selected machining method and the existing ultra-precision machining accuracy model (surface roughness model and geometric accuracy model) to obtain the mold core with the smallest surface roughness and geometric error.

[0012] (2) Micro injection molding process: After obtaining the mold core, select the melt material, control the injection molding process, mold closing - polymer pre-molding - rapid increase of mold temperature - precise measurement of injection volume - high-speed high-pressure injection filling - pressure holding - rapid cooling of mold temperature - mold opening and ejection;

[0013] Step 3: Optical performance measurement: Measure the optical performance of the optical component and optimize the component design.

[0014] In the field of injection molding, it is generally believed that the lower the surface roughness of the mold core, the higher the surface quality of the molded part. Therefore, in order to obtain injection molded parts that meet the optical performance requirements, the existing method generally requires the mold core to be processed to the best surface roughness, and then controls the injection molding process parameters, such as injection speed, mold temperature, injection pressure, mold temperature, holding time, etc. to improve the molding accuracy. This method of excessively high requirements for the surface quality of the mold core will cause low efficiency and high processing costs, and the control of injection molding process parameters has a very limited effect on improving the quality of injection molded parts.

[0015] On the one hand, in the micro-injection molding process, the mold core used has a nanoscale surface roughness, so it is necessary to consider the influence of the microscale effect on the molding accuracy of the molded part. The microscale effect is mainly reflected in the slip phenomenon between the melt and the wall under high injection pressure during the injection molding process. On the other hand, due to the nonlinear relationship between the mold core surface roughness and the demolding force, different melt materials have different optimal surface roughness. Therefore, for different melt materials, controlling the process parameters of the ultra-precision machining of the mold core to obtain the optimal surface roughness of the mold core close to the melt material can improve the geometric accuracy of the injection molded parts. Summary of the invention

[0016] The purpose of the present invention is to provide an optimization method for improving the injection molding accuracy of optical components, so as to solve the problems existing in the above-mentioned prior art, improve the processing efficiency of the mold core, enhance the molding accuracy of the optical component and reduce its surface roughness, thereby optimizing the micro-injection molding of the optical component and greatly helping to improve the optical performance of the optical component.

[0017] To achieve the above object, the present invention provides the following solutions:

[0018] The present invention provides an optimization method for improving the injection molding precision of an optical element, comprising the following steps:

[0019] Step 1: Optical component design: Optical design is performed based on the required optical performance, including: component geometric feature design, optical performance design and component accuracy requirements determined by the performance; precision requirements for molded parts are proposed based on optical performance, including geometric error and surface roughness;

[0020] Step 2: Processing, including core processing and injection molding;

[0021] (1) First, the melt material for micro injection molding is selected according to the performance and precision requirements of the optical components. Based on the selected melt material, the influence of the surface roughness of the mold core based on the melt material on the geometric accuracy and surface roughness of the molded parts during the injection molding process is analyzed;

[0022] (2) Performing ultra-precision machining of the mold core: Based on the characteristics of the optical element to be machined and the precision injection molding process, comprehensively considering the influence of the surface roughness of the mold core based on the melt material on the geometric accuracy and surface roughness of the molded part, selecting the ultra-precision machining method, then selecting the mold core material, and then planning the mold core ultra-precision machining process based on the selected machining method and the existing ultra-precision machining accuracy model to obtain a mold core that meets the optimal microscopic morphology mode and whose surface roughness is within the optimal surface roughness range;

[0023] (3) After the core processing is completed, the injection molding process is planned based on the established method for controlling the geometric accuracy of the molded part with the best surface roughness of the core. The process steps are: mold closing, polymer pre-plasticization, rapid increase of mold temperature, precise injection volume measurement, high-speed and high-pressure injection filling, pressure holding, rapid cooling of mold temperature and mold opening and ejection, so as to obtain injection molded parts with good molding accuracy and surface roughness;

[0024] Step 3: Optical performance measurement: Measure the optical performance of the optical component and optimize the component design.

[0025] Preferably, the influence of the surface roughness of the mold core based on the melt material on the geometric accuracy and surface roughness of the molded part includes the influence of the surface roughness of the mold core based on the melt material on the demolding force, establishing the optimal surface roughness range of the mold core for different melt materials, and studying the control method of the melt and wall slip phenomenon during the injection molding process under the nano-scale surface roughness of the mold core, and establishing the optimal surface micromorphology mode of the mold core with controllable slip phenomenon.

[0026] Preferably, the ultra-precision machining method is single-point diamond turning or fast tool / slow tool servo diamond turning or micro milling or fly cutter milling.

[0027] Preferably, the existing ultra-precision machining accuracy model includes a surface roughness model, a geometric accuracy model and a micro-morphology model.

[0028] Preferably, the characteristics of the optical element to be processed and the precision injection molding process include the optimal surface roughness range of the core of the molten material, the optimal surface microscopic morphology mode of the core with controllable slip phenomenon, and a comprehensive consideration of the geometric characteristics and precision requirements of the optical element to be processed.

[0029] Preferably, the process planning for ultra-precision machining of the mold core based on the selected machining method and the existing ultra-precision machining accuracy model includes calculating the ultra-precision machining geometric error prediction of the mold core according to the existing machining process parameters, and comparing it with the geometric error required by the molded part accuracy: if it is greater than the molded part geometric error, the ultra-precision machining process planning is re-performed; if it is less than the molded part geometric error, the process is used to machine the mold core, thereby obtaining a mold core that meets the micro-morphology pattern and has a surface roughness within the optimal surface roughness range.

[0030] Preferably, the injection molding process planning includes a method for controlling the geometric accuracy of molded parts based on the established optimal surface roughness of the mold core and a method for comprehensively controlling process parameters, surface roughness and geometric accuracy of molded parts.

[0031] Compared with the prior art, the present invention has achieved the following beneficial technical effects:

[0032] In the exploration of the molding process of micro-injection molding parts, the influence of melt material, core surface roughness, etc. on the molding accuracy of molded parts is often not considered. Therefore, it is generally believed that the higher the surface quality requirements for the core, the better. On the one hand, this puts too high requirements on the processing technology, resulting in its processing efficiency being too low; on the other hand, the geometric accuracy and surface accuracy of the molded parts often fail to meet expectations. A large part of the reason is that the slippage between the melt and the wall is easy to occur due to the overly smooth surface, and the excessive demolding force after the melt is molded leads to poor quality. The control of injection molding process parameters has a very limited effect on improving the quality of injection molded parts.

[0033] Therefore, under the premise that the injection molding process parameters are optimal, the present invention proposes an injection molding process that takes into account the melt material and the surface roughness of the core, selects different core surface roughness ranges according to different melt materials, and optimizes the core processing technology based on the existing ultra-precision machining quality prediction model. Compared with the extremely high quality requirements for the core surface in traditional methods, the optimization method for improving the injection molding accuracy of optical components in the present invention improves the molding accuracy of optical components and reduces their surface roughness on the basis of improving the core processing efficiency, which is helpful to optimize the micro-injection molding process of optical components and improve the optical performance of the components. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0035] Figure 1 The present invention is a process flow chart of a method for controlling the injection molding precision of an optical element in the prior art;

[0036] Figure 2 The present invention is a process flow chart of the optimization method for improving the injection molding accuracy of optical components. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] The purpose of the present invention is to provide an optimization method for improving the injection molding accuracy of optical elements to solve the problems existing in the prior art.

[0039] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0040] This embodiment involves the processing of the mold core. In microstructure injection molding, a certain surface roughness of the mold core surface can prevent the slippage of the melt and the wall, which can improve the surface quality (roughness) of the molded part. On the other hand, the demolding force of the molded part will increase with the increase of the surface roughness. However, at the nanometer level, due to the existence of capillary force and van der Waals force, too low surface roughness will cause the demolding force to rise sharply, thus causing great harm to the demolding of the molded part. This is because the increase of demolding force will cause the molded part to deform and crack during demolding, resulting in a decrease in the geometric accuracy of the molded part. Each material has a minimum demolding force of different sizes.

[0041] Therefore, for different optical components, optical design is carried out according to the required optical performance, the melt material for micro injection molding is selected according to the performance and precision requirements of the optical components, and the optimal surface roughness range of the mold core is established based on the selected melt material. At the same time, the relationship between surface roughness and demolding force is analyzed, and ultra-precision machining and injection molding process planning are carried out in combination with the existing ultra-precision machining model to improve the geometric accuracy of optical components and reduce their surface roughness.

[0042] Therefore, this embodiment provides an optimization method for improving the injection molding precision of optical components, such as Figure 2 As shown, the following steps are included:

[0043] Step 1: Optical component design: Optical design is performed based on the required optical performance, including: component geometric feature design, optical performance design and component accuracy requirements determined by the performance; molded part accuracy requirements are proposed based on the optical performance, including geometric errors and surface roughness.

[0044] Step 2: Processing, including core processing and injection molding;

[0045] (1) First, the melt material for micro injection molding is selected according to the performance and precision requirements of the optical components. Based on the selected melt material, the influence of the surface roughness of the mold core based on the melt material on the geometric accuracy and surface roughness of the molded parts during the injection molding process is analyzed;

[0046] (2) Performing ultra-precision machining of the mold core: Based on the characteristics of the optical element to be machined and the precision injection molding process, comprehensively considering the influence of the surface roughness of the mold core based on the melt material on the geometric accuracy and surface roughness of the molded part, selecting the ultra-precision machining method, then selecting the mold core material, and then planning the mold core ultra-precision machining process based on the selected machining method and the existing ultra-precision machining accuracy model to obtain a mold core that meets the optimal microscopic morphology mode and whose surface roughness is within the optimal surface roughness range;

[0047] (3) After the core processing is completed, the injection molding process is planned based on the established method for controlling the geometric accuracy of the molded part with the best surface roughness of the core. The process steps are: mold closing, polymer pre-plasticization, rapid increase of mold temperature, precise injection volume measurement, high-speed and high-pressure injection filling, pressure holding, rapid cooling of mold temperature and mold opening and ejection, so as to obtain injection molded parts with good molding accuracy and surface roughness;

[0048] Step 3: Optical performance measurement: Measure the optical performance of the optical component and optimize the component design.

[0049] In this specific embodiment, the influence of the surface roughness of the core based on the melt material on the geometric accuracy and surface roughness of the molded part, including the influence of the surface roughness of the core based on the melt material on the demolding force, establishes the optimal surface roughness range of the core for different melt materials, and studies the control method of the melt and wall slip phenomenon during the injection molding process under the nano-scale surface roughness of the core, and establishes the optimal surface micromorphology mode of the core with controllable slip phenomenon.

[0050] In this specific embodiment, the ultra-precision machining method is single-point diamond turning or fast tool / slow tool servo diamond turning or micro milling or fly cutter milling.

[0051] In this specific embodiment, the existing ultra-precision machining accuracy model includes a surface roughness model, a geometric accuracy model and a micro-morphology model.

[0052] In this specific embodiment, the optical element characteristics and precision injection molding process that need to be processed include the optimal surface roughness range of the core of the molten material, the optimal surface micromorphology mode of the core with controllable slip phenomenon, and a comprehensive consideration of the geometric characteristics and precision requirements of the optical element that needs to be processed.

[0053] In this specific embodiment, the process planning for ultra-precision machining of the mold core based on the selected machining method and the existing ultra-precision machining accuracy model includes calculating the ultra-precision machining geometric error prediction of the mold core according to the existing machining process parameters, and comparing it with the geometric error required by the molded part accuracy: if it is greater than the molded part geometric error, the ultra-precision machining process planning is re-performed; if it is less than the molded part geometric error, the process is used to process the mold core, thereby obtaining a mold core that meets the micro-morphology pattern and has a surface roughness within the optimal surface roughness range.

[0054] In this specific embodiment, the injection molding process planning includes a molding part geometric accuracy control method based on the established optimal surface roughness of the mold core and a comprehensive control method of process parameters, molding part surface roughness and geometric accuracy.

[0055] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scopes. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. An optimization method for improving the injection molding accuracy of optical components, characterized in that: The following steps are involved: Step 1: Optical component design: Optical design is performed based on the required optical performance, including: component geometric feature design, optical performance design and component accuracy requirements determined by the performance; precision requirements for molded parts are proposed based on optical performance, including geometric error and surface roughness; Step 2: Processing, including core processing and injection molding; (1) First, the melt material for micro injection molding is selected according to the performance and precision requirements of the optical components. Based on the selected melt material, the influence of the surface roughness of the mold core based on the melt material on the geometric accuracy and surface roughness of the molded parts during the injection molding process is analyzed; (2) Perform ultra-precision machining of the mold core: Based on the characteristics of the optical component to be machined and the precision injection molding process, comprehensively consider the influence of the surface roughness of the mold core based on the melt material on the geometric accuracy and surface roughness of the molded part, select the ultra-precision machining method, then select the mold core material, and then plan the ultra-precision machining process of the mold core based on the selected machining method and the existing ultra-precision machining accuracy model to obtain a mold core that meets the optimal microscopic morphology pattern and has a surface roughness within the optimal surface roughness range; (3) After the core processing is completed, the injection molding process is planned based on the established method for controlling the geometric accuracy of the molded part with the best surface roughness of the core. The process steps are: mold closing, polymer pre-plasticization, rapid increase of mold temperature, precise injection volume measurement, high-speed and high-pressure injection filling, pressure holding, rapid cooling of mold temperature and mold opening and ejection to obtain injection molded parts with good molding accuracy and surface roughness. Step 3: Optical performance measurement: measure the optical performance of the optical component and optimize the component design; The influence of the surface roughness of the mold core based on the melt material on the geometric accuracy and surface roughness of the molded part, including the influence of the surface roughness of the mold core based on the melt material on the demolding force, establishes the optimal surface roughness range of the mold core for different melt materials, and studies the control method of the melt and wall slip phenomenon during the injection molding process under the nano-scale surface roughness of the mold core, and establishes the optimal surface microscopic morphology mode of the mold core with controllable slip phenomenon.

2. The optimization method for improving the injection molding precision of optical components according to claim 1, characterized in that: The ultra-precision machining method is single-point diamond turning, fast-tool / slow-tool servo diamond turning, micro-milling or flying-cut milling.

3. The optimization method for improving the injection molding precision of optical components according to claim 1, characterized in that: Existing ultra-precision machining accuracy models include surface roughness model, geometric accuracy model and micro-morphology model.

4. The optimization method for improving the injection molding precision of optical components according to claim 1, characterized in that: The characteristics of the optical components to be processed and the precision injection molding process, including the optimal surface roughness range of the core of the molten material, the optimal surface micro-morphology mode of the core with controllable slip phenomenon, and comprehensive consideration of the geometric characteristics and precision requirements of the optical components to be processed.

5. The optimization method for improving the injection molding precision of optical components according to claim 1, characterized in that: The process planning for ultra-precision machining of the mold core based on the selected machining method and the existing ultra-precision machining accuracy model includes calculating the ultra-precision machining geometric error prediction of the mold core according to the existing machining process parameters, and comparing it with the geometric error required by the molded part accuracy: if it is greater than the molded part geometric error, the ultra-precision machining process planning is re-performed; if it is less than the molded part geometric error, the process is used to machine the mold core, thereby obtaining a mold core that meets the micro-morphology pattern and has a surface roughness within the optimal surface roughness range.

6. The optimization method for improving the injection molding precision of optical components according to claim 1, characterized in that: The injection molding process planning includes a molding part geometric accuracy control method based on the established optimal surface roughness of the mold core and a comprehensive control method of process parameters, molding part surface roughness and geometric accuracy.

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