玻璃透鏡模壓成型的工藝分析
夾層玻璃鏡片模壓成型法，是將熔融狀態(tài)的光學鏡片毛胚倒進高過夾層玻璃轉(zhuǎn)換點50℃之上的超低溫磨具中充壓成型。這類方式 不但非常容易產(chǎn)生夾層玻璃黏連在磨具的模表面，并且商品還非常容易造成出氣孔和冷模印痕（皺褶），不容易獲得理想的樣子揉面形精密度。之后，選用材料精密機械加工成的壓型板磨具，在無空氣氧化氛圍的自然環(huán)境中，將夾層玻璃和磨具一起加溫提溫至夾層玻璃的變軟點周邊，在夾層玻璃和磨具大概處在同樣溫度標準下，運用磨具對夾層玻璃施加壓力。接下去，在維持所施壓力的情況下，一邊制冷磨具，使其溫度降至夾層玻璃的轉(zhuǎn)換點下列（夾層玻璃的變軟點時的夾層玻璃黏度約為107.6泊，夾層玻璃的轉(zhuǎn)換點時的夾層玻璃黏度約為1013.4泊）。這類將夾層玻璃與磨具一起執(zhí)行等溫充壓的方法叫等溫加壓法，是一種較為非常容易得到 高精密，即非常容易高精密地將磨具樣子表層拷貝出來的方式 。這類夾層玻璃電子光學零件的生產(chǎn)制造方式 缺陷是：加溫提溫、制冷減溫都必須較長的時間，因而生產(chǎn)制造速率比較慢。以便處理這個問題，因此對于此事方式 開展了成效顯著的改善，即在一個壓模設備中應用多個磨具，以提升生產(chǎn)率。殊不知非球面磨具的工程造價很高，選用好幾個磨具必然導致成本費過高。對于這類狀況，進一步科學研究開發(fā)設計出與原先的鏡片毛胚成形標準較為相仿一點的非等溫加壓法，進而提升每一個磨具的生產(chǎn)制造速率和磨具的使用期。此外，也有人已經(jīng)科學研究開發(fā)設計把由熔化爐中流出去的夾層玻璃立即高精密成形的方式 。夾層玻璃毛胚與模壓成型品的品質(zhì)有立即的關聯(lián)。按大道理，絕大多數(shù)的光學鏡片都可以用于壓模成成形品?？墒?，變軟點高的夾層玻璃，因為成形溫度高，與磨具略微一些反映，導致磨具的使用期很短。因此，從模具材料非常容易挑選、磨具的使用期可以增加的見解考慮，應開發(fā)設計合適超低溫（600℃上下）標準下模壓成型的夾層玻璃。殊不知，開發(fā)設計的合適超低溫模壓成型的夾層玻璃必不可少合乎可以廉價地生產(chǎn)制造毛胚和不帶有環(huán)境污染的化學物質(zhì)（如PbO、As2O3）的規(guī)定。
Process Analysis of Glass Lens Precision Molding
The glass lens precision molding method involves pouring molten optical glass blanks into low-temperature molds that are heated to a temperature 50°C above the glass transition point. Pressure is then applied to shape the glass. However, this method has several issues:
1. The glass tends to adhere to the mold surface.
2. The products are prone to defects such as air bubbles and cold mold marks (wrinkles).
3. Achieving the desired shape and surface precision is difficult.
To address these challenges, precision-machined molds made from specialized materials were introduced. The process involves heating both the glass and the mold together in an oxygen-free atmosphere to a temperature near the softening point of the glass. Under these conditions, where the glass and mold are at nearly the same temperature, pressure is applied to the glass using the mold.
Afterward, while maintaining the applied pressure, the mold is cooled to a temperature below the glass transition point.
? At the softening point, the viscosity of glass is approximately 10?.? Poise.
? At the transition point, the viscosity is approximately 1013.? Poise.
This process, known as the isothermal pressing method, allows for high precision and accurate replication of the mold's surface.
Disadvantages:
? The heating and cooling steps require a significant amount of time, resulting in low production efficiency.
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Improvements to Increase Efficiency
To improve production efficiency, multiple molds were incorporated into a single molding device. However, the high cost of aspheric molds makes this approach expensive.
Development of Non-Isothermal Pressing:
A non-isothermal pressing method was developed to address this issue. This method adjusts the conditions to be closer to those used for molding lens blanks, increasing production speed and extending mold lifespan.
Direct Precision Molding from the Melting Furnace:
Research is also being conducted to develop a method where glass flows directly from the melting furnace into precision molds, bypassing intermediate steps.
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Glass Blanks and Molded Products
The quality of glass blanks is directly related to the quality of the molded products. In theory, most optical lenses can be molded into finished products.
Challenges with High Softening Point Glass:
? High softening point glass requires high molding temperatures, which can react slightly with the mold, shortening its lifespan.
Solutions:
To address this, glass suitable for low-temperature molding (around 600°C) is being developed. Such glass must meet the following criteria:
1. It must be cost-effective for blank production.
2. It must not contain environmentally harmful substances such as PbO or As?O?.
