Ultrasonic Welding Help - PC Troubleshooting

[Overflowing]

I'm exploring Ultrasonic Welding as an alternative to solvent welding of some polycarbonate parts...looking for someone with some knowledge in this arena. I'm very familiar with solvent welding acrylic, but PC is giving me troubles. Anyone willing to help me out?

 

[Tom.G]

As you probably already know, Ultrasonic Welding is just thermal welding with the heat supplied by the friction between the two parts being welded. So you have to figure out how to Ultrasonically move one of the pieces, perhaps a filler rod, while applying a fair amount of pressure to increase frictional heating.

I hope some more knowledgeable folks will come up with more specifics.

Talk to some of the manufacturers. A Search returns 145 000 hits.
https://www.google.com/?gws_rd=ssl#q=ultrasonic+welder+plastic

 

[Mech_Engineer]

Your best bet is to talk to a manufacturer of ultrasonic welding machines. They can guide you regarding your specific application.

For example: http://www.emersonindustrial.com/en...ultrasonic-plastic-welders/Pages/default.aspx

 

[CalcNerd]

Ultrasonic welding is a very expensive approach for the prototype project. Large companies can afford to put aside an expensive welder for trial work. Then their R&D staff have to design a horn and jig to concentrate the wave onto the joined surface ie the sonic horn is designed to concentrate the wave and the jig is designed to reflect the wave (like a mirror) back into the joined part and actually combine the initial and the reflected waves at the depth distance of the joint where the ultrasonic energy is focused and heats up the material to its melting point. If you try to use any old jig and horn, you will simply pump lots of ultrasonic energy into the whole part and simply warm one or both pieces up, but without concentrating the energy, no melting will take place.
.
This is excellent technology to seal electronics, no mess, no excess glues, the product is sealed from repair by unauthorized tinkering. It's an expensive method, but cheap in volume. Tuning an engineered horn (one specifically designed for the housing) still needs to be done by a floor technician with experience. ie often you still need to make several adjustments to the welding machine, even though YOU know the jig and horn are supposed to weld. Often, even an experienced tech will burn the surface of the item (smooth out or melt the exterior) until he gets the welders settings and proper pressures to weld at the depth of the joint.

 

[Overflowing]

Yes I've heard it's a bit of a "dark art" technique to get it just right - @CalcNerd what you are saying helps me a lot.

Right now I'm exploring a few other possible options as UW seems a bit cost-prohibitive, and without being able to find someone locally who has one that I can experiment with, the up front cost for something that may not work is a bit of a gamble. So I'm looking at either a combination of UV cured adhesvie + solvent welding (to keep the joint blushing to a minimum) or switching to PETG injected parts which don't have the blushing issue and are solvent weldable.

 

[Nidum]

Have you considered mechanical joints ? Snap together joining systems eliminate many of the problems of glued and welded part assemblies .

 

[Overflowing]

This is not an option for me. 1) would require re-tooling at quite an expense 2) joint needs to be sealed water tight (but not pressure tight) 3) joint needs to be durable

 

[rowell]

what is the cause of over heating or cracking of ultrasonic horn?
thanks!

 

[berkeman]

what is the cause of over heating or cracking of ultrasonic horn?
thanks!

Welcome to the PF.

Can you say where you have seen these issues?

 

[rowell]

In plastic ultrasonic welding process.

 

[berkeman]

You have seen overheating and cracking? Who did the fabrication of the horns and holding fixtures?

http://www.ultrasonicsolutions.in/images/ultrasonic_tech3.jpg