Ultrasonic staking stop limit and horn contact

[a_e]

Hello!

I am new to ultrasonics and plastic joining.

I am working on designing a fixture for ultrasonic staking of plastic part to a steel cover.

The Branson 2000ao welder we have does not have a weld by distance option with a linear encoder.

We plan to use a rectangular knurled face horn to strike the plastic bosses to form some head.
I am wondering about preventing the horn from hitting the steel cover and what could be done to prevent this.
I see this welder and many others come standard with a mechanical stop. The manual seems to suggest that this might not be a reliable or accurate enough way to prevent the horn from hitting the staked part.

I would expect only about 1 mm of head or so for my application.

I also see that common staking methods have the horn make contact with the metal surface. What are the implications of this? will it scream loudly and ruin the titanium horn?

Thank you all.

I know this is a small field so if anyone has any thoughts on this please let me know.

 

[3DDave]

Could you apply a barrier material to the horn where it might contact the metal? Kapton tape, for example.

 

[a_e]

I like the idea. For production that could be tedious, as we plan to have 23 different angular locations to stake on a circular part.

I wonder how good the mechanical stop is on the machine. At the moment I just have the actuator without mounting and pneumatic control system, so I cannot test this yet.

If the welder is reasonably consistent then a contact point or mechanical stop would really just be an emergency measure to not damage the horn or other components.

Thanks