Has anyone tried ultrasonic welding parts which have been printed? What resin would you recommend?
I see this approach as being useful to design and test energy director geometries prior to committing the part containing them to injection mould tooling. I appreciate that the resin will not exactly mimic the final injection moulded polymer, but if it could cut down on 85% of the iterative tool modification process it would be useful.
I would like to hear any thoughts, suggestions or experiences.
Our resins are acrylic based so I’m not sure that ultrasonic welding would be viable. Excessive heat tends to burn and crumble the materials rather than melting them. Chemical welding is my favorite technique for combining disconnected parts. Use a bit of resin at the interface between the parts and then a UV laser to cure the resin. This should create a strong, cross-linked bond. I like to throw parts in the UV chamber afterwards just to make sure all of the interface resin has cured.
I do a lot of injection mold design and a fair share of the parts I design have energy directors for ultrasonic welding. My experience is mostly with polypropylene, polystyrene, and polycarbonate. I have not tried to ultrasonically weld a printed part, but the idea hadn’t crossed my mind until reading your post of course. I find the idea intriguing, but anyone that knows energy director design knows it is a sensitive process. I am inclined to think that anything learned from experimenting with ultrasonically welding printed parts would ultimately not apply to a similar injection molded design.
It’s a great question though, and I think the next time I am working on an ultrasonic joint design I will print a part exactly like the molded part and experiment a bit. It would be worth the small effort to see if there are any similarities. The ability to prototype ultrasonic joints would be very valuable and would save a lot of time and money iterating.
This is a very good read on the subject of ultrasonically welding as it applies to SLS, FDM, and SLA. It is bad news for us but there is a lot of valuable information anyway.
Is there a specific UV laser you use for this? I’m very interested in trying this out, is there a certain mW or Nm sweet spot for getting the best results?
We’ve got a 405nm, 200mW laser here at HQ that cures things pretty quickly. Lower power lasers like the one @Chris_Estelow linked will work, but might take a bit longer to cure the resin. It tends to be a good practice to put any parts that have been resin welded in Form Cure, just to ensure that they’re bonded all the way through.
I’ve searched for 405nm, 200mW Lasers and it seems they are also used to cut objects. That sounds a little bit dangerous. Would be great if you could provide a link which model you are using for curing. Thanks.