你的超聲波焊接質(zhì)量怎么了？——塑料焊接技術(shù)

What Happened to Your Ultrasonic Weld Quality?
你的超聲波焊接質(zhì)量怎么了？
The most important factor in troubleshooting problems in ultrasonic welding is understanding the fundamentals of the process.
超聲波焊接中故障排除中，重要的因素是了解超聲波焊接過(guò)程的基本原理。

Sometimes poor ultrasonic welds can be traced back to the injection molding process. Injection mold wear can lead to a rounded energy director in the part (upper right), which produces a weak weld (lower right). A well-maintained mold produces a sharply pointed energy director (upper left), which produces a stronger weld (lower left) with lower welding amplitude and less flash.
有時(shí)不良的超聲波焊縫可以追溯到注射成型過(guò)程。注塑模具磨損會(huì )導致零件(右上)出現圓形能量指向，從而產(chǎn)生弱焊縫(右下角)。維護良好的模具產(chǎn)生尖銳的能量指示符(左上)，產(chǎn)生更強的焊縫(左下角)和較低的焊接幅度和較少的溢料。

The most important factor in troubleshooting problems in ultrasonic welding is understanding the fundamentals of the process. With this basic knowledge, most problems can be easily diagnosed and resolved. Even so, sometimes your time-tested weld recipe may suddenly fail for no discernible reason.
超聲波焊接中故障排除中重要的因素是了解超聲波焊接過(guò)程的基本原理。有了這些基本知識，大多數問(wèn)題都可以很容易地診斷和解決。即使如此，有時(shí)你經(jīng)過(guò)時(shí)間考驗的焊接配方可能會(huì )突然失效，沒(méi)有明顯的原因。

Perhaps your welder has been running the same application for months, maybe years, with no problems. Abruptly, this cheery continuity is disrupted. Has your weld strength decreased? Are you seeing excessive flash? Does your welder overload as soon as the cycle starts? Here, we will discuss a few unseen factors that can cause sudden changes in your weld quality and how to prevent and correct them.
也許您的焊工已經(jīng)運行了幾個(gè)月，也許幾年，沒(méi)有問(wèn)題，同樣的應用程序。突然間，這種令人愉快的連續性被打斷了。你的焊接強度下降了嗎？你看到太多溢料了嗎？你的焊工在循環(huán)一開(kāi)始就過(guò)載了嗎？在這里，我們將討論一些看不見(jiàn)的因素，可以導致您的焊接質(zhì)量突然變化，以及如何防止和糾正它們。

KNOW THE BASICS
了解基本知識
Ultrasonic welding works by applying a vibration at a frequency of 15 to 70 kHz to a plastic part. This vibration is generated through the use of piezoelectric ceramics in the transducer, that convert an electrical signal into mechanical motion. The transducer creates a vertical vibration that is then translated through the booster, and subsequently, the ultrasonic horn. The horn is typically designed to contact the part directly above the weld area so that the vibrations can travel though the upper part to the weld area.
超聲波焊接的工作方式是將頻率為15至70 kHz的振動(dòng)施加到塑料部件上。這種振動(dòng)是通過(guò)在換能器中使用壓電陶瓷產(chǎn)生的，這種壓電陶瓷將電信號轉化為機械運動(dòng)。換能器產(chǎn)生垂直振動(dòng)，然后通過(guò)調幅器和隨后的超聲波焊頭進(jìn)行轉換。焊頭通常被設計成與焊縫上方的部分直接接觸，這樣振動(dòng)就可以通過(guò)上部到達焊縫區域。

The ultrasonic vibrations create cyclical strain at the weld area, which generates heat that melts the plastic in a restricted area and welds the two parts. Because the ultrasonic vibration acts on the entire weld surface, an energy director is often added to control the melting and reduce the amplitude necessary to achieve a weld.
超聲波振動(dòng)在焊接區域產(chǎn)生周期性應變，產(chǎn)生熱量，在限定區域內熔化塑料并焊接這兩個(gè)部分。由于超聲波振動(dòng)作用于整個(gè)焊縫表面，通常會(huì )添加能量指向器來(lái)控制熔融，降低達到焊接需要的振幅。

It is important to prevent metal-to-metal contact on your horn to increase its longevity. Because the horn is a tool with acoustical properties, users should be careful to preserve its structural integrity. Any nicks or gouges in the surface of the horn act as stress concentrators that can rapidly lead to cracks when the horn is in use.
重要的是防止金屬與金屬接觸在你的焊頭上，以延長(cháng)它的壽命。由于焊頭是一種具有聲學(xué)特性的工具，用戶(hù)應該小心保持其結構完整性。焊頭表面的任何缺口或缺口都會(huì )起到應力集中器的作用，在使用時(shí)會(huì )迅速導致裂紋。

WARNING SIGNS警告
Many signs can indicate a change in your welding process. Some indications of a problem with your part include decreased weld strength, increased flash, and the appearance of cosmetic damage. Some things that signify a problem with the welder or ultrasonic horn are an increased wattage draw, a change in the sound of your weld (typically apparent on lower-frequency welders), and overloading.
許多跡象表明你的焊接過(guò)程發(fā)生了變化。你的部分出現問(wèn)題的一些跡象包括焊接強度下降，溢料增加，以及化妝品損壞的外觀(guān)。有些東西意味著(zhù)焊工或超聲波焊頭有問(wèn)題，比如功率的增加，焊縫聲音的變化(通常在低頻焊工上很明顯)，以及過(guò)載。

The first step in eliminating unseen problems is to record your welding setup. Make a “Weld Process” sheet that includes information such as your weld parameters (weld time, hold time, trigger mode, amplitude); manual settings (thruster height, pressure); and the critical dimensions of your part (diameter and energy-director/shear-joint size). Also include photos of the welder, showing the alignment and design of the horn and fixture. Refer to this document when problems arise—it may save you a lot of time and trouble.
消除未見(jiàn)問(wèn)題的第一步是記錄焊接設置。制作“焊接過(guò)程”表格，包括焊接參數(焊接時(shí)間、保持時(shí)間、觸發(fā)模式、幅度)；手動(dòng)設置(推進(jìn)器高度、壓力)；以及零件的臨界尺寸(直徑和能量導向/剪切接頭尺寸)。還包括焊機的照片，顯示了角和夾具的對準和設計。當出現問(wèn)題時(shí)，請參考這份文件-它可以為你節省很多時(shí)間和麻煩。

There are many not-so obvious factors that can negatively impact your weld quality. One of the most frequent causes of problems in a long-running process is wear on the mold that produces the parts to be joined. This is a slow, but sure, event in any molding process. Because most joint designs are relatively small compared with the size of the overall part, changes in their size or shape may go largely unnoticed. For many applications, a change in shear width from 0.016 in. to 0.020 in. can make a huge difference in weld quality. Such changes can be caused by just 0.002 in. of mold wear on each part.
有許多不那么明顯的因素會(huì )對你的焊接質(zhì)量產(chǎn)生負面影響。在一個(gè)長(cháng)期運行的過(guò)程中，常見(jiàn)的問(wèn)題之一是模具上的磨損，該模具生產(chǎn)要連接的零件。這是一個(gè)緩慢，但肯定的，事件，在任何成型過(guò)程。因為與整體的尺寸相比，大多數的連接設計都相對較小，所以它們的大小或形狀的變化可能在很大程度上沒(méi)有被注意到。對于許多應用程序，剪切寬度從0.016英寸改變。0.020英寸。會(huì )對焊接質(zhì)量產(chǎn)生巨大影響。這樣的變化可能是由0.002的。模具磨損的每個(gè)部分。

Another important factor is environmental changes such as ambient heat, cold, or humidity. Humidity is a particular concern if you are using a hydrophilic material such as nylon, polycarbonate, or polysulfone. Very cold temperatures can cause polymers to become brittle, which may cause them to crack rather than weld at a normal welding pressure. High heat can lead to longer solidification times, causing problems if you are working with short hold times.
另一個(gè)重要因素是環(huán)境變化，如環(huán)境熱、冷或濕度。如果您使用的是親水性材料，如尼龍、聚碳酸酯或聚砜，濕度是一個(gè)特別關(guān)注的問(wèn)題。非常冷的溫度會(huì )導致聚合物變得脆性，這可能導致它們開(kāi)裂，而不是在正常的焊接壓力下焊接。高熱量會(huì )導致更長(cháng)的凝固時(shí)間，如果你的工作時(shí)間很短，就會(huì )產(chǎn)生問(wèn)題。

Some materials are less sensitive to process changes. Try switching to an easily welded material, like ABS, to achieve greater consistency in your process.
有些材料對工藝變化不太敏感。嘗試切換到容易焊接的材料，如ABS，以實(shí)現更大的一致性在您的過(guò)程。

Probably one of the most overlooked factors contributing to welding problems is changes in the time from molding the part to welding the part. Proper ultrasonic welding setup can be drastically different when welding “cold” parts as opposed to welding “hot” parts. It is generally not a good idea to weld “cold” parts to “hot” parts.
可能導致焊接問(wèn)題的被忽視的因素之一是從成型到焊接的時(shí)間的變化。當焊接“冷”件時(shí)，適當的超聲波焊接裝置可能會(huì )與焊接“熱”零件大不相同。通常情況下，把“冷”部分焊接到“熱”部分并不是一個(gè)好主意。

If at all possible, leave plenty of time for the part to cool after molding before welding. “Hot” parts are more difficult to control and can cause inconsistency in your weld process. Also, try to perform the welding operation in a climate-controlled environment to eliminate seasonal effects on your process. This is especially important in humid regions.
如果可能的話(huà)，在焊接前留出足夠的時(shí)間讓零件在成型后冷卻?！盁帷辈糠指y控制，并可能造成不一致的焊接過(guò)程。此外，嘗試在氣候控制的環(huán)境中執行焊接操作，以消除對您的過(guò)程的季節性影響。這在潮濕地區尤為重要。

MORE FACTORS TO CHECK
更多的因素需要檢查
If you know it is not your parts causing the problems, it could be your ultrasonic tooling. Occasionally a horn will develop a crack. While most horns will not run at all after forming a crack, some do. Those will often emit a high-pitched ringing sound or run at a higher wattage than normal. It is very important to discontinue use of a cracked horn because it tends to put excess stress on the transducer and can lead to broken piezoelectric ceramics.
如果你知道不是你的零件造成了問(wèn)題，它可能是你的超聲波工具。有時(shí)喇叭會(huì )裂開(kāi)。雖然大多數角在形成裂縫后根本不會(huì )運行，但有些則會(huì )。它們通常會(huì )發(fā)出高音調的振鈴聲或以比正常更高的瓦特數運行.停止使用有裂紋的喇叭是非常重要的，因為它會(huì )對換能器施加過(guò)多的應力，從而導致壓電陶瓷的斷裂。

Probably the easiest diagnostic test is to mix-and-match your ultrasonic stack if you have multiple welders of the same frequency. Try the horn with a transducer and booster that have been working well. If all is good after this switch, then you know the horn is not the problem. Likewise, you can put a working stack in a questionable welding machine. This is a quick and easy way to locate the trouble spot in your machine without any special equipment.
可能簡(jiǎn)單的診斷測試是混合和匹配你的超聲波堆疊，如果你有多個(gè)相同頻率的焊工。用換能器和助推器試一下喇叭，它們一直工作得很好。如果這個(gè)開(kāi)關(guān)后一切都好，那么你就知道喇叭不是問(wèn)題。同樣，你也可以把一個(gè)工作的堆疊在一個(gè)有問(wèn)題的焊接機器中。這是一種快速、簡(jiǎn)便的方法，可以在沒(méi)有任何特殊設備的情況下找到機器上的故障點(diǎn)。

If you find that the problem is your horn, check it for cracks. To locate cracks in a horn, spray it with a foaming cleaner. Then use the test feature on your welder to introduce short bursts of ultrasonic energy into the horn. The cleaner will collect in the crack and turn a blackish color. WD-40 oil can be used if a foaming cleaner is not available.
如果你發(fā)現問(wèn)題是你的喇叭，檢查它是否有裂縫。若要找出喇叭中的裂縫，請用泡沫清潔劑噴灑。然后利用你的焊機上的測試特性，在喇叭中引入短脈沖超聲波能量。清潔工會(huì )在裂縫中收集，并使顏色變黑。如果沒(méi)有泡沫清潔劑，可以使用WD-40油。

Finally, the welding fixture has a significant effect on the accuracy and precision of your welds. Make sure the fixture is providing support to the entire joint area, and that there is no room for misalignment of parts during loading. When welding softer materials such as polyethylene and polypropylene, be sure that there is support around the joint area in both lateral and vertical directions. Soft materials tend to deform outwards, which will hinder or prevent proper welding.
焊接夾具對焊縫的精度和精度有著(zhù)重要的影響。確保夾具為整個(gè)連接區域提供支持，并且在裝貨過(guò)程中沒(méi)有零件不對齊的空間。當焊接較軟的材料，如聚乙烯和聚丙烯，確保在接縫區域周?chē)袡M向和縱向的支撐。軟材料傾向于向外變形，這將妨礙或阻止適當的焊接。

關(guān)于作者
米蘭達·馬庫斯，伊利諾伊州圣查爾斯杜卡內智能組裝解決方案的應用工程師，廣泛從事超聲波和旋轉焊接工藝，并為SPE年度技術(shù)會(huì )議(ANTEC)合著(zhù)了三份技術(shù)論文。馬庫斯還合著(zhù)了一本教科書(shū)的一章。她歡迎在internet或(630)797-4937上提問(wèn)。
ABOUT THE AUTHOR
Miranda Marcus, applications engineer at Dukane Intelligent Assembly Solutions in St. Charles, Ill., has worked extensively in ultrasonic and spin welding processes and has coauthored three technical papers for the SPE Annual Technical Conference (ANTEC). Marcus has also coauthored a chapter of a textbook. She welcomes questions at internet or (630) 797-4937.