機械畢業(yè)設計-基于在線式PCB清洗機機械結構管線路設計

機械畢業(yè)設計-基于在線式PCB清洗機機械結構管線路設計,機械,畢業(yè)設計,基于,在線,PCB,清洗,結構管,線路,設計 密 級 分類號 編 號 成 績 本科生畢業(yè)設計 (論文) 外 文 翻 譯 原 文 標 題 Ultrasonic Cleaning 譯 文 標 題 超聲波清洗 作者所在系別 機電工程學院 作者所在專業(yè) 機械設計制造及其自動化 作者所在班級 作 者 姓 名 作 者 學 號 指導教師姓名 指導教師職稱 完 成 時 間 教務處制 譯文標題 超聲波清洗 原文標題 PCB Cleaning Technology and Application of Semi Aqueous Cleaning 作 者 Amanda Stuart. 譯 名 阿曼達·斯圖爾特 國 籍 中國 原文出處 Aircraft Engineering 超聲波清洗 超聲波清洗是工業(yè)領域一種廣泛應用的新方法，可以去除工件表面的磨削，研磨，拋光后表面殘留的碎屑，去除工件表面殘留的油污，甚至可以去除油漆層。超聲波清洗能夠應用于從大到小的工業(yè)零件，大到波音 747 飛機的引擎大修，小到手表的部件制作，都有超聲波清洗的用武之地，目前廣泛應用超聲波清洗的行業(yè)涉及電子，精密機械，照明工程，光學，冶金，醫(yī)療儀器設備等諸多領域。 超聲波清洗對工業(yè)的推動和影響是顯而易見的，要真正理解超聲波的價值，我們需要進一步了解超聲波的原理。 超聲波清洗原理 超聲波清洗的作用主要是一種叫做“空化效應”的現(xiàn)象造成的，每分鐘數(shù)以十億計的空泡向內(nèi)爆裂，撞擊到工件的表面，將工件表面的附著物剝離，分散開來。對于一些手工清洗難以達到的位置，（例如深孔，死角等）超聲波清洗也可以有很好的清洗效果，這也是超聲波清洗的一個優(yōu)點。 超聲波清洗常用頻率在 20 千赫到 50 千赫之間，常用清洗溫度在 50 -80 ℃ 之間。 在一個超聲波清洗系統(tǒng)中,空化效應是由于一系列超聲波換能器把聲波導入清洗槽中的清洗液而產(chǎn)生。這個聲波傳遍整個清洗槽, 在液體中產(chǎn)生了波的壓縮和擴張。 在壓縮波時，清洗液中的分子被緊密的壓縮在一起，相反，在擴張波時，分子被快速的拉開了。 擴張是那么戲劇性，以至于分子被裂開了，形成了精微的氣泡。氣泡里是局部真空的。當氣泡周圍的壓力變大時，周圍的液體就涌過來，并使氣泡爆裂。當這個發(fā)生時，就產(chǎn)生了液體的噴射，導致溫度高達 9032華氏度 (約為太陽的溫度)。這個極高的溫度，伴隨著液體噴射的速度，產(chǎn)生了一個非常強烈的清洗作用。然而，因為氣泡的擴張和爆裂周期是那么短暫，伴隨在氣泡外的液體迅速吸收了熱量，從而在清洗過程中防止了清洗槽和清洗液過熱。 影響清洗效果的因素 有 7 個主要影響清洗效果的原因: 1.清洗時間 2.清洗液溫度 3.采用的清洗液 4.工件的外形設計 5.超聲波頻率 6.超聲功率密度 7.清洗裝夾方式 清洗時間 是影響超聲波清洗效果的一個主要因素，清洗時間取決于工件的污染程度以及清潔度要求，典型的清洗時間是 2-10 分鐘，只有少數(shù)工件能夠在很短的時間里面清洗干凈。 實際操作中可能在精細清洗前需要一個預處理過程，一些工件需要一道以上的超聲波清洗工序，在一些時候，需要布置超聲波清水漂洗槽去除（前道工序）殘留的清洗劑。 溫度和清洗劑 是兩個緊密相關的因素。一般來說，使用水作為清洗劑，超聲波作用范圍最好在 60 ℃ ，一些 PH 較高的溶液需要更高的清洗溫度。討論化學藥品的 PH 值是一個好的開始，但是深入的討論化學知識不是這篇文章要涉及的內(nèi)容。 簡要的說，下面所列的是水基超聲波清洗液的主要組成成分水（硬水，軟水，純水，或者蒸餾水） B.酸，或者堿 C.表面活性劑 潤濕劑 分散劑 乳化劑 皂化劑 D.可選成分 螯合劑 抗化劑 緩沖劑 消泡劑 化學藥劑的作用必須充分考慮上面的因素。一些為水射流清洗設計的化學藥品，包括一些防銹劑，不適合用于超聲波清洗作業(yè)中。 工件的裝夾設計 通常超聲波清洗的程序是這樣：把工件裝入工藝料框，經(jīng)過 3-4 個工序（例如：超聲波清洗，噴淋漂洗（可選），浸泡漂洗，干燥），在清洗料框中，有時候超聲波輻射會被工件遮擋住。 大多數(shù)超聲波清洗設備都被設計為專門用途。 在設計階段，要重點考慮超聲波換能器的布置方式，可以采用底置，側置。對于自動超聲波清洗設備，必須準確的布置換能器以保證清洗效果的一致性。一些工件對超聲波清洗和其他工序需要采取不同的裝夾方式。一些工件需要在清洗過程中旋轉或者微動以保證清洗效果。 超聲波輸出頻率 目前大多數(shù)工業(yè)清洗應用中把 40 千赫作為基礎頻率 , 較低的工作頻率。例如 20-25 千赫 , 常用于超聲波空化腐蝕少的金屬，或者極大阻礙或吸收超聲波傳播的場合。 功率密度（每加侖的瓦數(shù)）（ 1 加侖 = 3.8 升 ） 通常，小的工件需要較高的功率密度以達到要求的清洗效果。大多數(shù)工業(yè)清洗設備需要的功率密度在 50-100 瓦 / 加侖。不過，容積超過 50 加侖 的水槽，通常只需要大約 20 瓦 / 每加侖的功率密度，因為超聲波系統(tǒng)水箱容積越大，通常需要的功率密度呈下降趨勢。 工件的清洗載入方式 在清洗設備的設計階段。必須充分考慮工件清洗時候的載入方式，一些較大的工件，內(nèi)部比較難以清洗的工件（例如一些鑄造件），一個原則是只能載入清洗液的一半重量的工件清洗，例如，在 5 加侖 的水中 ( 大約 40 磅 ) ，一次只能載入 20 磅 的工件清洗，在大多數(shù)案例中，分兩次載入較少的工件清洗比一次載入較大的工件清洗效果要好得多。 上面提到的相關因素，在設計一個高品質的超聲波清洗系統(tǒng)式需要綜合考慮，忽視了某一項可能會造成不必要的麻煩。 Ultrasonic Cleaning Ultrasonic cleaning is a good fit for a wide range of applications, from removing swarf and grinding and polishing residue to treating parts covered in oil, grease, or layers of paint. Ultrasonics can be used to clean miniature watch parts or to support the overhaul of jumbo jet engines. And from an industry perspective, the fields of electrotechnics, precision mechanics and light engineering, optics, metal processing, and medical equipment have proven particularly receptive to the ultrasonic concept. So the impact of ultrasonic cleaning is clearly recognizable. But to truly understand the value of ultrasonics, one must understand how ultrasonic cleaners really work. Ultrasonic Cleaning Explained The cleansing effect of ultrasound is the product of a phenomenon called cavitation. Billions of minute gas bubbles implode, causing shock waves that undermine dirt and blast it off a part’s surface. One of the key advantages of this process is that it allows users to clean part surfaces that are completely inaccessible to a manual cleaning process. Ultrasound frequencies generally range between 20 kilohertz and 50 kilohertz, depending on application requirements. Ultrasonic cleaning is typically performed at temperatures between 122 F and 176 F . In an ultrasonic cleaning system, cavitation is produced by introducing sound waves into a cleaning liquid by means of a series of transducers mounted to a cleaning tank. The sound travels throughout the tank and creates waves of compression and expansion in the liquid. In the compression wave, the molecules of the cleaning liquid are compressed together tightly. Conversely, in the expansion wave, the molecules are pulled apart rapidly. The expansion is so dramatic that the molecules are ripped apart, creating microscopic bubbles. The bubbles contain a partial vacuum. As the pressure around the bubbles becomes greater, surrounding fluid rushes in and collapses the bubble. When this occurs, a jet of liquid is created, resulting in temperatures as high as 9,032 F (roughly the temperature of the surface of the sun). The extreme temperature, combined with the liquid jet’s velocity, provides a very intense cleaning action. However, because the bubble expansion and collapse cycle is so short, the liquid surrounding the bubble quickly absorbs the heat, preventing the tank and cleaning liquid from becoming overly hot during the cleaning process. Secrets to Ultrasonic Success There are seven major concerns related to successful ultrasonic cleaning: 1. Time 2. Temperature 3. Chemistry 4. Part Fixture Design 5. Ultrasonic Output Frequency 6. Watts Per Gallon 7. Loading TimeCleaning times can vary tremendously in an ultrasonic process, depending largely on how dirty the part is and how clean is clean. A normal trial period is two to 10 minutes, since very few parts are sufficiently clean in a shorter period of time. Precleaning may be required to remove gross contamination or to chemically prepare the parts for a final clean. Some applications require more than one ultrasonic treatment to complete the required cleaning. Ultrasonic rinsing may also be required in some cases to more thoroughly remove wash chemicals. Temperature & ChemistryTemperature and chemistry are closely related. Generally, ultrasonic cleaning in an aqueous solution is optimized at 140 F . Some high pH solutions require higher temperatures. The chemical pH is a good place to start; but a thorough examination of chemistry is beyond the scope of this article. In brief, the following should be considered the main components of aqueous ultrasonic cleaning chemistry: A. Water (hard, soft, DI, or distilled) B. pH C. Surfactants Wetting agents Dispersants Emulsifiers Saponifiers D. Optional Ingredients Sequestrants Inhibitors Buffering agents Defoamers The chemical formulation must consider all of the above characteristics. Some chemicals designed for spray cleaning — or that include rust inhibitors — are not suitable for ultrasonic cleaning. Part Fixture DesignThe procedure for ultrasonic cleaning is generally as follows: Put parts in basket and place basket through three or four process steps (i.e., ultrasonic wash, spray rinse (optional), immersion rinse, dry). Some parts loaded in baskets can mask or shadow from the radiated surface of the ultrasonic transducers. Most ultrasonic cleaning systems are designed for specific applications. Bottom-mounted transducers or side-mounted transducers are important considerations during the process design stage. Automated systems must specifically address the location of the transducers to ensure cleaning uniformity. Some parts require individual fixturing to separate the part for cleaning or subsequent processes. Some parts require slow rotating or vertical motion during the cleaning to ensure critical cleanliness. Ultrasonic Output FrequencyThe majority of the ultrasonic cleaning that is done in industrial applications today uses 40 kHz as a base frequency. Lower frequencies, such as 20-25 kHz, are used for large masses of metal where ultrasonic erosion is of little consequence. The large mass dampens or absorbs a great amount of the ultrasonic cleaning power. WattsPer GallonIn general, smaller parts require higher watts per gallon to achieve the desired level of cleanliness. Most industrial ultrasonic cleaning systems use watt density from 50 to 100 watts per gallon. However, tanks over 50 gallons usually require only about 20 watts per gallon because ultrasonic processes traditionally have shown diminishing returns in large tanks sizes. LoadingLoading of the parts to be cleaned must be considered when developing an ultrasonic cleaning process. A large dense mass, for example, prevents internal surfaces from being thoroughly cleaned (i.e., metal castings). A rule of thumb is that the load by weight should be less than the weight of half the water volume. So, for example, in five gallons (approximately 40 lbs .) of water, the maximum workload should be less than 20 lbs . In some cases, it is better to ultrasonically clean two smaller loads rather than one larger load. Each of the factors outlined here must be considered when specifying an ultrasonic application to ensure a high level of cleaning success. Neglecting any single factor can have a negative impact on the overall cleaning process. 指 導 教 師 評 語 外文翻譯成績： 指導教師簽字： 年 月 日 注：1. 指導教師對譯文進行評閱時應注意以下幾個方面：①翻譯的外文文獻與畢業(yè)設計（論文）的主題是否高度相關，并作為外文參考文獻列入畢業(yè)設計（論文）的參考文獻；②翻譯的外文文獻字數(shù)是否達到規(guī)定數(shù)量（3 000字以上）；③譯文語言是否準確、通順、具有參考價值。 2. 外文原文應以附件的方式置于譯文之后。