A large-size optical mold rapid and low-cost manufacturing method

Abstract

The present application relates to a kind of large size optical mold fast low-cost manufacturing method, comprising the following steps: obtaining the machining number module of mold, grinding and polishing.The large size optical mold fast low-cost manufacturing method of the present application, by mechanical arm small grinding head, the optical mold with mold steel as base material is directly processed to the required surface shape precision and surface roughness, without surface nickel-phosphorus modification, single-point diamond turning, artificial grinding and polishing and other process links, simplify manufacturing process flow and improve manufacturing efficiency.Compared with the optical surface after nickel-phosphorus modification, the optical surface of mold steel base is more capable of resisting wear and tear and scratch, prolongs the service life of mold, and reduces manufacturing cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of advanced optical manufacturing technology, in particular to a large-size optical mold rapid and low-cost manufacturing method. BACKGROUND

[0002] Large-size optical molds are used to produce various high-precision optical components, which are applied to lenses, prisms, vehicle HUDs and optical instruments, etc. These components have a wide range of applications in consumer electronics, automobiles, medical and communication fields, and the manufacturing precision directly affects the final performance of the products. Large-size high-end optical molds need to achieve extremely high surface roughness and face shape precision. The traditional manufacturing method is machine tool milling, followed by manual grinding and polishing. This manual grinding and polishing process has a long manufacturing cycle, high cost and poor process consistency.

[0003] With the advancement of technology, numerical control machining (CNC) and electric spark machining (EDM) have become the mainstream optical mold manufacturing technology. However, both of the above-mentioned machining technologies have shortcomings in the manufacturing of large-size high-end optical molds: the numerical control machining (CNC) and electric spark machining (EDM) equipment has a large investment, low processing efficiency and high technical level requirements for the operator. At the same time, the traditional machine tool milling is affected by process errors, and the precision and surface quality of the processed mold cannot directly meet the use requirements, and the final surface roughness and face shape precision of the optical mold cannot be directly achieved. It is necessary to modify the processed surface with nickel-phosphorus, and then use single-point diamond turning (SPDT) and manual grinding and polishing to obtain the final surface roughness and face shape precision. The specific steps include: first, use different numbers of oil stones for rough grinding, then use multiple types of sandpaper for fine grinding, then use different types of grinding paste and polishing paste for polishing process, and finally modify the nickel-phosphorus surface after reaching a certain precision. This process is complicated, has high cost, low manufacturing efficiency, strong dependence on manual experience, and poor wear resistance and scratch resistance of the nickel-phosphorus modified surface. SUMMARY

[0004] The present application solves the technical problems in the prior art and provides a large-size optical mold rapid and low-cost manufacturing method.

[0005] To solve the above technical problems, the technical scheme of the present application is as follows:

[0006] A large-size optical mold rapid and low-cost manufacturing method, comprising the following steps:

[0007] Step i: obtaining the machining numerical model of the mold;

[0008] Point coordinates are extracted by using MATLAB, a mold surface is fitted by using Zernike polynomials, a three-coordinate detection path is generated according to the fitted theoretical surface to obtain the surface error data of the mold, and a machining path of the machining equipment is designed based on the three-coordinate detection result and the position of the machined optical element;

[0009] Step ii: grinding;

[0010] The surface of the mold steel is ground to a roughness of less than 100 nm and a surface accuracy PV value of less than 2 microns;

[0011] Step iii: polishing;

[0012] First, the surface of the mold steel is coarsely polished in the coarse polishing stage to a roughness of less than 20 nm and a surface without scratches;

[0013] Then, the surface of the mold steel is finely polished in the fine polishing stage to a roughness of less than 5 nm, a surface accuracy PV value of less than 1 micron, and a surface without scratches.

[0014] In the above technical solution, in step ii, the air pressure during grinding is 0.15 MPa, and the spindle speed is 300 r / min.

[0015] In the above technical solution, in step ii, the polishing pad uses polished leather, and the abrasive uses 14-18 micron diamond powder.

[0016] In the above technical solution, in step iii, the abrasive used in the coarse polishing stage is 3 micron alumina polishing paste.

[0017] In the above technical solution, in step iii, the abrasive used in the fine polishing stage is 0.05 micron alumina polishing paste.

[0018] In the above technical solution, in step iii, the polishing pressure in the coarse polishing stage is 0.1 MPa, and the speed is 250 r / min.

[0019] In the above technical solution, in step iii, the polishing pressure in the fine polishing stage is 0.06 MPa, and the speed is 200 r / min.

[0020] The present application has the following advantages:

[0021] The large-size optical mold rapid low-cost manufacturing method of the present application directly processes the optical mold with mold steel as the base material to the required surface accuracy and surface roughness by a mechanical arm small grinding head, without the need for surface nickel-phosphorus modification, single-point diamond turning, manual grinding and polishing, etc. process links, simplifying the manufacturing process and improving manufacturing efficiency. Compared with the optical surface after nickel-phosphorus modification, the optical surface of the mold steel base has stronger anti-wear and anti-scratch ability, prolongs the service life of the mold, and reduces the manufacturing cost. Attached Figure Description

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0023] Figure 1 A schematic diagram of the overall structure of the small grinding head robot.

[0024] Figure 2 This is a schematic diagram of a polishing disc.

[0025] Figure 3 This is a schematic diagram of the manufacturing process for high-end optical molds.

[0026] Figure 4 This is a schematic diagram of the roughness results after grinding.

[0027] Figure 5 This is a schematic diagram of the surface roughness results after polishing. Detailed Implementation

[0028] The inventive concept of this invention is as follows:

[0029] The present invention provides a rapid and low-cost manufacturing method for large-size optical molds. It uses a robotic arm with a small grinding head as a processing tool system to grind and polish the surface of the mold steel that has been roughly formed by CNC machining. The surface shape error is fed back by contour detection. By changing different polishing fluids, the required accuracy can be directly achieved. The nickel-phosphorus modification process is omitted, the manufacturing cost is reduced, and the service life of the mold is increased.

[0030] The present invention provides a rapid and low-cost manufacturing method for large-size optical molds. By using the surface shape error obtained from contour detection as the processing input, the surface of the mold steel is directly processed to the required surface quality and surface shape accuracy through grinding, rough polishing and fine polishing.

[0031] The present invention provides a rapid and low-cost manufacturing method for large-size optical molds, which directly achieves mirror surface quality and roughness indicators by polishing the mold steel without the need for nickel-phosphorus surface modification.

[0032] The present invention will now be described in detail with reference to the accompanying drawings.

[0033] The system applicable to the rapid and low-cost manufacturing method for large-size optical molds of this invention includes: a six-degree-of-freedom industrial robot, a small grinding head polishing module, polishing tools, abrasives, and a white light roughness meter. The six-degree-of-freedom robot is low-cost, highly flexible in operation, and can handle the processing of complex surface molds. Its structure is as follows... Figure 1 As shown, the small grinding head polishing module is integrated at the end of the spindle of a six-DOF industrial robot. The polishing tool is connected to the end of the small grinding head polishing module.

[0034] The polishing tool is divided into three parts, from top to bottom, including a polishing pad, a pitch layer and a base. The base is made of aluminum alloy, the pitch layer is a polishing pitch commonly used for processing mirrors, and the polishing pad is made of different types of polishing leather or cloth, such as Figure 2 as shown.

[0035] The abrasive includes diamond micro powder and alumina abrasive of different particle sizes, which are used for grinding and polishing, respectively. The white light roughness instrument is mainly used for measuring the roughness of the surface of the optical mold.

[0036] The large-size optical mold rapid and low-cost manufacturing method, as shown in Figure 3 includes the following steps:

[0037] Step i: obtaining the processing numerical model of the mold.

[0038] Point coordinates are extracted using MATLAB, the surface shape of the mold is fitted using Zernike polynomial, three-coordinate detection path is generated according to the fitted theoretical surface shape to obtain the surface error data of the mold, and the machining path of the machining equipment is designed based on the three-coordinate detection result and the position of the machined optical element.

[0039] Step ii: grinding.

[0040] The polishing disc is prepared during the grinding process, that is, a layer of grinding pad is attached to the pitch layer of the polishing tool. The grinding pad is made of polishing leather, and the abrasive is made of 14-18 micron diamond micro powder.

[0041] The entire grinding process includes a rough grinding stage and a fine grinding stage.

[0042] The air pressure in the rough grinding stage is 0.15 MPa, and the spindle speed is 300 r / min.

[0043] After the surface of the mold steel reaches the surface shape accuracy, fine grinding is performed. The fine grinding stage also uses a pitch polishing disc with a grinding pad, and the air pressure is also 0.15 MPa, and the speed is 300 r / min.

[0044] The entire grinding process is repeated until the surface of the optical mold reaches the accuracy that can be polished. The roughness of the mold steel surface after grinding is less than 100 nm, and the surface shape accuracy PV value is less than 2 μm, as shown in Figure 4 .

[0045] Step iii: polishing.

[0046] The polishing process is similar to the grinding process, and a pitch polishing disc is also used, but the polishing pad is made of cloth, and the abrasive is made of alumina, which is different from the grinding stage.

[0047] The entire polishing process includes a rough polishing stage and a fine polishing stage.

[0048] In the rough polishing stage, the abrasive is 3-micron alumina polishing paste, the polishing pressure is 0.1 MPa, and the rotation speed is 250 r / min. After rough polishing, the surface roughness of the mold steel is less than 20 nm, and the surface is scratch-free, and then, fine polishing is performed.

[0049] In the fine polishing stage, the combination of pitch polishing disc and flannel is also used, but the abrasive is finer 0.05-micron alumina polishing paste, the polishing pressure is 0.06 MPa, and the rotation speed is 200 r / min. After fine polishing, the roughness is better than 5 nm, the surface shape accuracy PV value is <1 μm, and the surface is scratch-free, as shown in FIG. 2, at this time, the surface of the mold steel meets the accuracy requirements of high-end optical molds, and the mold pressing process can be performed. Figure 5

[0050] Experiments prove that the large-size optical mold rapid and low-cost manufacturing method of the application is effective, and the required surface roughness and surface quality of the mold can be obtained.

[0051] The large-size optical mold rapid and low-cost manufacturing method of the application is not only limited to the rapid and low-cost manufacturing of large-size high-end optical molds, but also applicable to the high-precision and high-surface quality processing of optical assemblies with other mold steel materials as the base.

[0052] The large-size optical mold rapid and low-cost manufacturing method of the application directly processes the optical mold with mold steel as the base material to the required surface shape accuracy and surface roughness through the mechanical arm small grinding head, without the process links of surface nickel-phosphorus modification, single-point diamond turning, and manual grinding and polishing, simplifies the manufacturing process, and improves the manufacturing efficiency. Compared with the optical surface after nickel-phosphorus modification, the optical surface with mold steel as the base has stronger anti-wear and anti-scratch ability, prolongs the service life of the mold, and reduces the manufacturing cost.

[0053] Obviously, the above embodiments are only examples for clearly illustrating, and not limiting the embodiments. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description. Here, all the embodiments need not and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present application.​

Claims

1. A method for rapid and low cost manufacturing of large size optical molds, characterized in that, The mechanical arm small grinding head is used as a machining tool system to grind and polish the surface of the mold steel which is rough formed by numerical control machining. The profile detection is used to feedback the surface error. The polishing liquid is replaced to directly reach the required precision. The small grinding head polishing module is integrated at the end of the main shaft of the six-degree-of-freedom industrial robot. The polishing tool is connected at the end of the small grinding head polishing module. The polishing tool is divided into three parts from top to bottom, including a polishing pad / grinding pad, an asphalt layer and a base. The base is made of aluminum alloy, the asphalt layer is made of polishing asphalt, the grinding pad is made of polishing leather, and the polishing pad is made of flannel. The method comprises the following steps: Step i: obtaining a machining numerical model of a mold; Point coordinates are extracted by using MATLAB, the surface shape of the mold is fitted by using Zernike polynomials, three-coordinate detection paths are generated according to the fitted theoretical surface shape to obtain surface error data of the mold, and a machining path of a machining device is designed based on the three-coordinate detection results and the position of the machined optical element; Step ii: grinding; The polishing tool has a grinding pad outside the asphalt layer. The grinding pad is made of polishing leather, and the abrasive is 14-18 micron diamond powder. The air pressure during grinding is 0.15 MPa, and the spindle speed is 300 r / min. The surface of the mold steel is ground to a roughness of less than 100 nm, and the surface accuracy PV value is less than 2 microns; Step iii: polishing; The polishing tool has a polishing pad outside the asphalt layer. The polishing pad is made of flannel, and the abrasive is aluminum oxide. The abrasive used in the rough polishing stage is 3 micron aluminum oxide polishing paste. The polishing pressure in the rough polishing stage is 0.1 MPa, and the speed is 250 r / min. The abrasive used in the fine polishing stage is 0.05 micron aluminum oxide polishing paste. The polishing pressure in the fine polishing stage is 0.06 MPa, and the speed is 200 r / min. Firstly, the mold steel surface is rough polished to a roughness of less than 20 nm and no scratches on the surface by using the rough polishing stage. Then, the mold steel surface is fine polished to a roughness of less than 5 nm, a surface accuracy PV value of less than 1 micron and no scratches on the surface by using the fine polishing stage.

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