CN106826463A - A kind of complex-curved processing method - Google Patents

Abstract

The present invention disclose a kind of complex-curved processing method, and one, treat processed complex curved surface and carry out material removal using strain disc, until face shape error peak-to-valley value is better than 30 μm；2nd, error analysis is carried out to complex-curved face shape, low order error for entire surface shape better than 30 μm is processed using strain disc, medium-high frequency error for entire surface shape better than 30 μm is processed using small abrasive nose, until the RMS value of face shape error is better than 100nm；3rd, error analysis is carried out to complex-curved face shape error, low order error of the RMS value better than 100nm is processed using strain disc, local medium-high frequency error or annulus error under to the precision are processed using small abrasive nose, and the medium-high frequency error to the entire surface shape under the precision is processed using magnetorheological；Until the RMS of complex-curved face shape error is better than 30nm；4th, material removal efficiency high can be obtained to demand, the present invention is met to complex surface machining using ion beam fabrication technology, obtains shape convergence efficiency in face high.

Description

A Machining Method of Complicated Curved Surface

technical field

The invention belongs to the technical field of optical system processing, and in particular relates to a processing method for complex curved surfaces.

Background technique

With the continuous development of modern optical technology, the requirements for optical performance indicators of optical systems continue to increase. High-precision large-aperture aspheric mirrors are the core components of modern optical systems and are widely used in high-resolution modern optical systems. With the increase of mirror diameter, higher requirements are placed on the efficiency of optical processing.

At present, there are many processing methods for aspheric optical elements, such as CCOS small grinding head sub-aperture processing method, stress disk processing method, magnetorheological processing method, ion beam processing method, etc. These methods have been practically used in the processing of large-aperture aspheric mirrors. However, these methods have their limitations. For example, CCOS small grinding head sub-aperture polishing and stress disk polishing can increase the size of the grinding head to improve the material removal efficiency. The ability to control the surface error decreases, that is, the efficiency of surface convergence decreases. Magneto-rheological processing and ion beam processing are more deterministic processing methods, and the grinding head will not wear out during the processing, and a more stable removal function can be obtained, so their surface shape convergence efficiency is higher, but the two The size of the grinding head of this method is small, so the material removal efficiency is low, and it cannot meet the requirements of processing efficiency in large-aperture aspheric mirrors.

Contents of the invention

In view of this, the present invention provides a processing method for complex curved surfaces, which can obtain high material removal efficiency and high surface shape convergence efficiency, thereby realizing high-efficiency and high-precision processing of large-diameter complex curved surfaces.

Realize the technical scheme of the present invention as follows:

A method for processing complex curved surfaces, comprising the following steps:

Step 1. Grinding stage

For the complex surface to be processed, use the stress disc to remove the material until the peak-to-valley value of the surface shape error is better than 30 μm;

Step 2. Rough polishing stage

To analyze the error of the complex surface shape, use the stress disc to process the low-order error of the whole surface shape better than 30μm, and use the small grinding head to process the medium and high frequency error of the whole surface shape better than 30μm, until the RMS of the surface shape error Value better than 100nm;

Step 3, fine polishing stage

Perform error analysis on complex surface shape errors, use stress disc processing for low-order errors with RMS values better than 100nm, use small grinding heads for local mid-high frequency errors or ring zone errors under this accuracy, and use small grinding heads for processing under this accuracy The medium and high frequency errors of the entire surface shape are processed by magnetorheology; the RMS of the surface shape error of complex curved surfaces is better than 30nm;

Step 4. Ion beam processing stage

Ion beam processing technology is used to process complex curved surfaces to meet requirements.

Beneficial effect:

The present invention analyzes the existing mature processing technology, complements the advantages of different processing methods, and establishes a combined processing strategy according to the surface shape characteristics of complex curved surfaces in different processing stages, such as PV value, RMS value and medium and high frequency distribution, so as to carry out more targeted processing. The processing can effectively improve the material removal efficiency and surface shape convergence efficiency in the processing of large-diameter complex curved surfaces.

Description of drawings

Figure 1 is a schematic diagram of the qualitative analysis of the material removal efficiency and surface shape convergence efficiency of the main processing methods.

Figure 2 is a flowchart of the rough polishing stage of combined processing technology.

Figure 3 is a flow chart of the fine polishing stage of combined processing technology.

detailed description

The present invention will be described in detail below with reference to the accompanying drawings and examples.

The processing methods mainly used in the combined processing technology in the present invention include: CCOS small grinding head aperture processing method, stress disk processing method, magnetorheological processing method (MRF), ion beam processing method (IBF). The qualitative analysis results of material removal efficiency and surface shape convergence efficiency are shown in Fig. 1.

It can be seen from Figure 1 that the material removal efficiency of different processing methods is inversely proportional to the surface shape convergence efficiency, that is, the highest processing efficiency cannot be achieved with a single processing method. In order to solve this problem, the invention provides a kind of processing method of complex curved surface, comprises the following steps:

Step 1. Grinding stage

As shown in Figure 2, for the complex curved surface to be processed, use the stress disc to remove material and detect the surface shape error until the peak-to-valley value of the surface shape error is better than 30 μm, and enter the rough polishing stage.

The large-diameter complex curved surface needs to be ground first after milling. The surface shape error at this stage is characterized by low surface shape accuracy and large material removal. In this stage, the PV value is used to evaluate the surface shape, and the stress disk machining method is used for rapid material removal.

Step 2. Rough polishing stage

As shown in Figure 2, the error analysis is performed on the complex surface shape. At this stage, the surface shape error usually includes two components. The first is the low-order component, which mainly includes defocus, astigmatism, spherical aberration, etc. covering the entire surface shape. large-scale error. For the low-order error of the entire surface shape better than 30μm, the stress disc is used for processing. The second type is medium and high frequency components, mainly including ring zone error, edge error, and small-scale local error. For medium and high frequency errors whose overall surface shape is better than 30μm, use CCOS small grinding head to process the surface shape error until the surface shape error The RMS value is better than 100nm into the fine polishing stage.

Step 3, fine polishing stage

As shown in Figure 3, the error analysis is carried out on the surface shape error of the complex surface, and the low-order error whose RMS value is better than 100nm is processed by stress disk. For the medium and high frequency surface error, further analysis is required: The high-frequency error or ring-band error is processed by CCOS small grinding head, and the medium-high frequency error evenly distributed in the entire surface shape under this accuracy is processed by magnetorheology; the surface shape error is detected until the RMS of the surface shape error of the complex surface Better than 30nm into the ion beam processing stage.

Step 4. Ion beam processing stage

Ion beam processing technology is used to process complex curved surfaces to meet requirements.

Among the above processing methods, the ion beam method has the best certainty, but the amount of material removal is the smallest. Therefore, only when the surface shape accuracy is better than 30nm, the ion beam method is used for processing, and finally the required surface shape is achieved and the processing is completed.

In order to describe the above process in detail, the above process is introduced using an actual processing example: the actual processed workpiece is a SiC aspheric mirror with a diameter of 1450 mm. The PV value of the initial surface shape error is 72 μm. According to the combined processing strategy, stress discs are used for processing at this stage. As the surface shape converges to a PV less than 30 μm, the next step of processing is performed using a combination of a stress disc and a small grinding head. As the surface shape further converges until the RMS is less than 100nm, it enters the polishing stage. The surface shape errors at this stage are more complicated, including low-order surface shape errors, mid-to-high frequency errors, and local mid-to-high frequency errors. MRF is mainly used to remove the medium and high frequency surface errors distributed throughout the surface. Magneto-rheological processing until the surface shape accuracy reaches RMS of 30nm is mainly processed by ion beam processing. After ion beam processing, the surface shape accuracy meets the requirements and the entire processing process is completed.

To sum up, the above are only preferred embodiments of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (1)

1. A processing method for a complex curved surface, comprising the following steps: Step 1. Grinding stage For the complex surface to be processed, use the stress disc to remove the material until the peak-to-valley value of the surface shape error is better than 30 μm; Step 2. Rough polishing stage To analyze the error of the complex surface shape, use the stress disc to process the low-order error of the whole surface shape better than 30μm, and use the small grinding head to process the medium and high frequency error of the whole surface shape better than 30μm, until the RMS of the surface shape error Value better than 100nm; Step 3, fine polishing stage Perform error analysis on complex surface shape errors, use stress disc processing for low-order errors whose RMS value is better than 100nm, use small grinding heads for local mid-high frequency errors or ring zone errors under this accuracy, and use small grinding heads for processing under this accuracy The medium and high frequency errors of the entire surface shape are processed by magnetorheology; the RMS of the surface shape error of complex curved surfaces is better than 30nm; Step 4. Ion beam processing stage Ion beam processing technology is used to process complex curved surfaces to meet requirements.