光学镜片厂家对光学透镜的成型有着独到的认识和研究，下面就给大家分享一下相关的成型方法。
1、成型方法：玻璃之所以能够精密模压成型，主要是因为开发了与软化的玻璃不发生粘连的模具材料。原来的玻璃透镜模压成型法，是将熔融状态的光学玻璃毛坯倒入高于玻璃转化点50℃以上的低温模具中加压成形。这种方法不仅容易发生玻璃粘连在模具的模面上，而且产品还容易产生气孔和冷模痕迹（皱{TodayHot}纹）不易获得理想的形状和面形精度。后来，采用特殊材料精密加工成的压型模具，在无氧化气氛的环境中，将玻璃和模具一起加热升温至玻璃的软化点附近，在玻璃和模具大致处于相同温度条件下，利用模具对玻璃施压。接下来，在保持所施压力的状态下，一边冷却模具，使其温度降至玻璃的转化点以下（玻璃的软化点时的玻璃粘度约为107。6泊，玻璃的转化点时的玻璃粘度约为1013。4泊）这种将玻璃与模具一起实施等温加压的办法叫等温加压法，是一种比较容易获得高精度，即容易精密地将模具形状表面复制下来的方法。这种玻璃光学零件的制造方法缺点是：加热升温、冷却降温都需要很长的时间，因此生产速度很慢。为了解决这个问题，于是对此方法进行了卓有成效的改进，即在一个模压装置中使用数个模具，以提高生产效率。然而非球面模具的造价很高，采用多个模具势必造成成本过高。针对这种情况，进一步研究开发出与原来的透镜毛坯成型条件比较相近一点的非等温加压法，借以提高每一个模具的生产速度和模具的使用寿命。另外，还有人正在研究开发把由熔融炉中流出来的玻璃直接精密成型的方法。
2、玻璃的种类和毛坯{HotTag}玻璃毛坯与模压成型品的品质有直接的关系。按道理，大部分的天文望远镜的光学玻璃都可用来模压成成型品。但是，软化点高的玻璃，由于成型温度高，与模具稍微有些反应，致使模具的使用寿命很短。所以，从模具材料容易选择、模具的使用寿命能够延长的观点出发，应开发适合低温（600℃左右）条件下模压成型的玻璃。然而，开发的适合低温模压成型的玻璃必需符合能够廉价地制造毛坯和不含有污染环境的物质（如PbO、As2O3）的要求。对模压成型使用的玻璃毛坯是有要求的：a.压型前毛坯的表面一定要保持十分光滑和清洁；b.呈适当的几何形状；c.有所需要的容量。毛坯一般都选用球形、圆饼形或球面形状，采用冷研磨成型或热压成型。
Molding Technology for Optical Glass Lenses
Manufacturers of optical lenses have developed unique insights and research into the molding process for optical lenses. Below are some of the main methods for shaping optical glass lenses:
1. Molding Method
The reason why glass can be precision molded is primarily due to the development of mold materials that do not adhere to softened glass. The original method for molding glass lenses involved pouring molten optical glass blanks into a low-temperature mold, heated to a temperature 50°C above the glass transition point, and applying pressure to shape it. This method not only made it easy for the glass to adhere to the mold surface but also caused issues such as air bubbles and cold mold marks (wrinkles), making it difficult to achieve the desired shape and surface precision.
Later, precision-processed molds made from special materials were introduced. In an oxygen-free atmosphere, both the glass and mold were heated together to a temperature near the softening point of the glass, with the glass and mold at approximately the same temperature. Pressure was applied to the glass using the mold. Subsequently, while maintaining the applied pressure, the mold was cooled, lowering its temperature below the glass transition point (the viscosity of the glass at its softening point is approximately 10⁷.⁶ Poise, while at its transition point, it is approximately 10¹³.⁴ Poise).
This method of applying isothermal pressure to the glass and mold together is called the isothermal pressing method, which is relatively easier for achieving high precision, as it allows the mold surface's shape to be accurately replicated.
However, the downside of this manufacturing method for optical glass components is that both heating and cooling require a significant amount of time, resulting in slow production speeds.
To solve this problem, improvements were made by using multiple molds within a single pressing device to enhance production efficiency. However, the cost of aspheric molds is very high, and using multiple molds inevitably increases the overall cost.
In response to this issue, further research has led to the development of the non-isothermal pressing method, which has conditions closer to those of the original lens blank molding process. This method improves the production speed of each mold and extends the mold's lifespan.
Additionally, efforts are being made to develop a method where glass flowing directly from a melting furnace is precision-molded without intermediate steps.
2. Types of Glass and Blanks {HotTag}
The quality of glass blanks is directly related to the quality of molded products. In theory, most optical glass used in astronomical telescopes can be molded into finished products. However, glass with a high softening point requires high molding temperatures, which may cause slight reactions with the mold and significantly shorten its lifespan.
Therefore, from the perspective of easier mold material selection and extending mold lifespan, glass suitable for low-temperature molding (around 600°C) should be developed. However, the glass developed for low-temperature molding must meet the following requirements:
1. The blanks must be inexpensive to manufacture.
2. The glass must not contain environmentally harmful substances, such as PbO or As₂O₃.
Requirements for glass blanks used in molding:
• a. The surface of the blank must be very smooth and clean before pressing.
• b. The blank must have an appropriate geometric shape.
• c. The blank must have the required volume.
Blanks are generally spherical, disk-shaped, or hemispherical and are produced through cold grinding or hot pressing.
