Welding forces can change mid-process to adjust for differences in materials without affecting overall weld time.
Often in medical part production, different materials have to be joined, like amorphous polystyrol (PS) and semi-crystalline polyethylene terephthalate (PET), such as in a dental applicator for treating caries at an early stage. Ultrasonic welding produces a controlled melt for a tight bond with minimal thermal load. The key to success is the variable programming of the weld force to uphold the desired joining velocity.
Because of the small dimensions, convex and concave shapes and thin film, the dental applicator was a difficult component to produce. Even the slightest dimensional variations in the injection-moulded parts could pose serious problems. The challenge was to design a weld joint that did not allow melt to escape laterally when welding the holder components, while simultaneously clamping the film. Also, the correct positioning of the delicate film during the production process had to be ensured. The already existing perforations in the film meant an additional challenge, since such “injuries” could have an effect on subsequent processing. They represent a disruption of surface, so-called notch effect points at which mechanical vibrations lead to stress peaks. Under certain circumstances, these can lead to undesirable plasticizing of the resin.
Herrmann Ultrasonics supported the dental company in designing the holder components in such a way that four locating pins and four small thin-walled joints ensured the best weld result. The thin-walled joint design (V-joint) is suited for small components with thin walls. The energy director has a clearly defined contact surface and facilitates self-locating.
通常，只能焊接类似的树脂或具有相似熔体指标的树脂。无定形和半晶树脂具有不同的熔体指标，并且更难加入。但是，对于牙科涂抹器而言，不同的树脂等级难以证明是有利的。由于机械振动，无定形支架很容易迅速加热，但半晶状膜的响应延迟，从而使其免受热降解。更确切地说，必须找到一个理想的操作点，在该操作点上，持有者上的无定形引脚成功地使其成功地塑造出来，而只有无定形成分在薄膜中做出了足够的响应，而晶体成分则没有。如果能量输入超过此值，则膜融化过多并被破坏。
Ultrasonic welding allows materials with two different melting points to be bonded without compromising their individual characteristics.
焊接涂抹器零件时，焊机在过程的最后三分之一（在焊缝末端末端的焊缝末端）为0.22毫米之前切换为第二个焊接力。切换到第二个更高的焊接力时，用第一焊缝产生的熔体会被压缩。结果，保留焊接操作的速度直到结束并允许焊接时间缩短。此外，还减少了机械振动的膜的负载。此外，在放置期间，将冷却熔体更加强烈地压在薄膜上，从而增加了焊缝的强度。
From the machinery standpoint, the prerequisites for such accuracy are a precise determination of the starting position for the ultrasonics (trigger point), controlled melt build-up, and quick and accurate termination.
触发点：仅在设备接触零件表面后停止后才触发超声波的接近运动，并且超声波被触发。参考点零确定零件的尺寸公差是均衡的。
融化堆积：控制允许在多达三个步骤中对焊接力进行编程，以优化线性连接过程。结果是控制熔体的堆积，是操作点的确切可重复性的条件。
终止：发电机在µ秒范围内运行。即使在快速焊接周期中，这也可以精确终止。
Herrmann Ultrasonics
www.herrmannultrasonics.com
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