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Ultrasonic Welder Reject Limits

Hello everybody, 

I just joined this group and I'm not sure if this is to answer specific technical questions or if this to talk about ultrasonic welding in general, but here goes my question and you let me know:

I set up a reject limit for welding collapse distance, let's say I set it up to collpase 0.0004 in and set the reject limits between 0.0003 and 0.0005 in. I then monitor the weld results screen to check the values of each welding cycle. I notice the cycle is 0.00041, 0.00043, etc. but always within the limits, but anyways an alarm is generated. When I go to the alarm it says "Actual value = 0.0007", so the value on the result screen is different from the value on the alarm, and that happens on every cycle. I have not found a way to correct that, not even by calling Branson technical support. 

Can anybody help?

Thanks in advance!

  • Hi,

    I’m sorry for my delayed response. I’m the Ultrasonics Product Manager at Emerson and I’ve reviewed your problem with my technical team. Based on your summary and product symptoms, the system is working as intended but the root cause of your issue is a hidden factor – “Hold Force”. During the welding process, the ultrasonics energy will continue to be applied and weld your part until your target collapse of 0.0004 inches is achieved; however due to a hold force being applied to the plastic part, the molten plastic will continue to collapse under the hold force which ultimately delivers a final collapse of 0.0007 inches. What this means is that although ultrasonics ends at 0.0004 inches, the hold force continues to sandwich the plastic further whereby extending the collapse beyond the set limits.

    To address this, we recommend the following 2 options:
    1. The first option is to loosen the tight limits of 0.0003 – 0.0005 inches. By increasing the range of the limits, your actual value of 0.0007 inches will fall within the range and not cause an alarm.
    2. The second option is to reduce your target collapse distance so that your post hold dimension is within your intended limits. (i.e. set a collapse target of ~0.0002 inches with the same hold force so that the final collapse is at 0.0005 inches).

    I hope this explanation is helpful and if you have further questions, please feel to reach out to our application experts for further guidance.