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你的超声波焊接质量怎么了?——塑料焊接技术

你的超声波焊接质量怎么了?——塑料焊接技术


What Happened to Your Ultrasonic Weld Quality?
你的超声波焊接质量怎么了?
The most important factor in troubleshooting problems in ultrasonic welding is understanding the fundamentals of the process.
超声波焊接中故障排除中,重要的因素是了解超声波焊接过程的基本原理。


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.
有时不良的超声波焊缝可以追溯到注射成型过程。注塑模具磨损会导致零件(右上)出现圆形能量指向,从而产生弱焊缝(右下角)。维护良好的模具产生尖锐的能量指示符(左上),产生更强的焊缝(左下角)和较低的焊接幅度和较少的溢料。


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.
超声波焊接中故障排除中重要的因素是了解超声波焊接过程的基本原理。有了这些基本知识,大多数问题都可以很容易地诊断和解决。即使如此,有时你经过时间考验的焊接配方可能会突然失效,没有明显的原因。


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.
也许您的焊工已经运行了几个月,也许几年,没有问题,同样的应用程序。突然间,这种令人愉快的连续性被打断了。你的焊接强度下降了吗?你看到太多溢料了吗?你的焊工在循环一开始就过载了吗?在这里,我们将讨论一些看不见的因素,可以导致您的焊接质量突然变化,以及如何防止和纠正它们。


KNOW THE BASICS
了解基本知识
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.
超声波焊接的工作方式是将频率为15至70 kHz的振动施加到塑料部件上。这种振动是通过在换能器中使用压电陶瓷产生的,这种压电陶瓷将电信号转化为机械运动。换能器产生垂直振动,然后通过调幅器和随后的超声波焊头进行转换。焊头通常被设计成与焊缝上方的部分直接接触,这样振动就可以通过上部到达焊缝区域。


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.
超声波振动在焊接区域产生周期性应变,产生热量,在限定区域内熔化塑料并焊接这两个部分。由于超声波振动作用于整个焊缝表面,通常会添加能量指向器来控制熔融,降低达到焊接需要的振幅。


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.
重要的是防止金属与金属接触在你的焊头上,以延长它的寿命。由于焊头是一种具有声学特性的工具,用户应该小心保持其结构完整性。焊头表面的任何缺口或缺口都会起到应力集中器的作用,在使用时会迅速导致裂纹。


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.
许多迹象表明你的焊接过程发生了变化。你的部分出现问题的一些迹象包括焊接强度下降,溢料增加,以及化妆品损坏的外观。有些东西意味着焊工或超声波焊头有问题,比如功率的增加,焊缝声音的变化(通常在低频焊工上很明显),以及过载。


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.
消除未见问题的第一步是记录焊接设置。制作“焊接过程”表格,包括焊接参数(焊接时间、保持时间、触发模式、幅度);手动设置(推进器高度、压力);以及零件的临界尺寸(直径和能量导向/剪切接头尺寸)。还包括焊机的照片,显示了角和夹具的对准和设计。当出现问题时,请参考这份文件-它可以为你节省很多时间和麻烦。


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.
有许多不那么明显的因素会对你的焊接质量产生负面影响。在一个长期运行的过程中,常见的问题之一是模具上的磨损,该模具生产要连接的零件。这是一个缓慢,但肯定的,事件,在任何成型过程。因为与整体的尺寸相比,大多数的连接设计都相对较小,所以它们的大小或形状的变化可能在很大程度上没有被注意到。对于许多应用程序,剪切宽度从0.016英寸改变。0.020英寸。会对焊接质量产生巨大影响。这样的变化可能是由0.002的。模具磨损的每个部分。


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.
另一个重要因素是环境变化,如环境热、冷或湿度。如果您使用的是亲水性材料,如尼龙、聚碳酸酯或聚砜,湿度是一个特别关注的问题。非常冷的温度会导致聚合物变得脆性,这可能导致它们开裂,而不是在正常的焊接压力下焊接。高热量会导致更长的凝固时间,如果你的工作时间很短,就会产生问题。


Some materials are less sensitive to process changes. Try switching to an easily welded material, like ABS, to achieve greater consistency in your process.
有些材料对工艺变化不太敏感。尝试切换到容易焊接的材料,如ABS,以实现更大的一致性在您的过程。


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.
可能导致焊接问题的被忽视的因素之一是从成型到焊接的时间的变化。当焊接“冷”件时,适当的超声波焊接装置可能会与焊接“热”零件大不相同。通常情况下,把“冷”部分焊接到“热”部分并不是一个好主意。


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.
如果可能的话,在焊接前留出足够的时间让零件在成型后冷却。“热”部分更难控制,并可能造成不一致的焊接过程。此外,尝试在气候控制的环境中执行焊接操作,以消除对您的过程的季节性影响。这在潮湿地区尤为重要。


MORE FACTORS TO CHECK
更多的因素需要检查
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问题,它可能是你的超声波工具。有时喇叭会裂开。虽然大多数角在形成裂缝后根本不会运行,但有些则会。它们通常会发出高音调的振铃声或以比正常更高的瓦特数运行.停止使用有裂纹的喇叭是非常重要的,因为它会对换能器施加过多的应力,从而导致压电陶瓷的断裂。


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.
可能简单的诊断测试是混合和匹配你的超声波堆叠,如果你有多个相同频率的焊工。用换能器和助推器试一下喇叭,它们一直工作得很好。如果这个开关后一切都好,那么你就知道喇叭不是问题。同样,你也可以把一个工作的堆叠在一个有问题的焊接机器中。这是一种快速、简便的方法,可以在没有任何特殊设备的情况下找到机器上的故障点。


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.
如果你发现问题是你的喇叭,检查它是否有裂缝。若要找出喇叭中的裂缝,请用泡沫清洁剂喷洒。然后利用你的焊机上的测试特性,在喇叭中引入短脉冲超声波能量。清洁工会在裂缝中收集,并使颜色变黑。如果没有泡沫清洁剂,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.
焊接夹具对焊缝的精度和精度有着重要的影响。确保夹具为整个连接区域提供支持,并且在装货过程中没有零件不对齐的空间。当焊接较软的材料,如聚乙烯和聚丙烯,确保在接缝区域周围有横向和纵向的支撑。软材料倾向于向外变形,这将妨碍或阻止适当的焊接。


关于作者
米兰达·马库斯,伊利诺伊州圣查尔斯杜卡内智能组装解决方案的应用工程师,广泛从事超声波和旋转焊接工艺,并为SPE年度技术会议(ANTEC)合著了三份技术论文。马库斯还合著了一本教科书的一章。她欢迎在internet或(630)797-4937上提问。
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.


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