Ultrasonic Welding Problem

[shelbycharged]

Hello All,
First off, thanks for reading this! Here is my problem:

I am using dukane servo driven sonic welders to join together plastic cassette components. They are relatively decent sized, about 5 inches X 3 inches. They don't weld the entire surface, but only on the mating paths. My problem is that the bottom of the cassette gets all scuffed up during the process. I would like to make some sort of pad to put underneath the cassette that will prevent the plastic surface from being scuffed up yet also not interfere with the welding efficacy.

Does anyone have any sort of experience in the subject that may suggest a good material that won't deteriorate (quickly atleast) from the welding? My initial thought were just get something softer than the material being welded, but having no experience I wanted to ask here first.

thanks!

 

[MikeHalloran]

I don't think you will find a material that will work in the way that you think.

As I understand it, the horn that delivers the energy and the anvil that backs up the part are necessarily rigid, so that the energy is transferred into the weld, and only the weld.

I think the best you can do is polish the hell out of the contact surfaces, and make sure they are in firm contact with the workpieces before the sound comes on.


My qualifications are very limited. I have made two serious attempts at ultrasonic welding, followed the manufacturers advice, followed the salesmen's advice, spent a lot of money, and couldn't get a good weld to save my soul. ... or my job.

I was at first going to suggest that you call your supplier's sales engineer, but my experience suggests that's a total waste of time after your check clears.



Mike Halloran
Pembroke Pines, FL, USA

 

[MacGyverS2000]

I have no experience with the items in question so I'm only guessing at their configuration, but...

Can you place some Kapton tape on the problem areas so anything sliding over it doesn't get scratched? It's cheap, easily replaceable when it starts to get worn, and pretty darn slick.

Dan - Owner

http://www.Hi-TecDesigns.com

 

[Compositepro]

Go ahead and try a thin rubber sheet. It will absorb some energy, but to prevent marring you have to reduce the contact pressure points on that side of the cassette. Kapton tape may also work but may not last long. After all the vibration comes from the other side and the welding occurs in specially designed high contact pressure areas on the parts and not elsewhere. It seems the marring must be occurring at pressure points with the support table due to lack of conformance of the part and table (or anvil).

 

[MikeHalloran]

I forgot to ask: Did it _ever_ work correctly?


Mike Halloran
Pembroke Pines, FL, USA

 

[shelbycharged]

@Mike: We tried polishing the lower surface. It improved the problem slightly.
@MacGyver: A good idea. We are trying to avoid anything with a adhesive. This is an automated assembly line producing medical surgical supplies.
@Compositepro: Any thoughts on pulyurethane? I know it is some times used as a vibrational damper.
@Mike: This product is bigger than the other ones we make of similar shape. We don't get the problem on our other products. However new one is a fully new product in a new automation line. We have passed our medical validation but would still like the looks of it cosmetically to be appealing.

We do have a much larger product, but for that we are using hot plate welders. Whatever we use will have to be very thin to minimize interference with the weld. Any changes will have to go through a validation. I wonder if we fixture the part tighter to prevent it from moving might that help also?