Which offers stronger ABS-to-ABS bonding, ultrasonic welding or use of solvent (acetone)? 1

[TheRingSmith]

Hello,
I have an ABS part with a standard energy director profile (per ultrasonic welding equipment maker Dukane's recommendation) that the plastic injection molder indicated that they cannot produce. The profile is a right triangle, where the base is 0.5mm and the height from center of base to apex is 0.25mm. The molder suggested that due to machining limitation, that the height be 0.5mm, creating an equilateral triangle profile instead. This would deviate from Dukane's suggested profile.

Would this taller energy director make it more or less optimal for sonic welding? I'm contemplating using acetone to bond the parts if sonic welding would not be possible if I use the molder's recommendation. The solvent would melt the ABS plastic together, similar to what sonic welding would do, but I'm not certain whether this bonding method would produce a weaker bond or not. Any advise? Thanks in advance.

Howard

 

[MintJulep]

I'd think the solvent bond would be stronger.

But why compare it to ultrasonic? What you really need to determine is if the solvent bond is strong enough for your application.

 

[TheRingSmith]

MintJulep,
Thanks for the reply. The ultrasonic welding would be preferred because it's a cleaner process, even though capital investment is significantly greater. However, as mentioned, if the energy director cannot be correctly molded, then it would defeat its purpose. I'm weighing between the two alternatives and would want to defer to the one that yields the best bonding strength. If sonic welding is not feasible, then I would have to use the other method. I have not been able to find any data to support that one method yields a stronger bond than the other.

Howard

 

[Duwe6]

It is a tossup; both processes constitute "welding", thus both are equal in strength. Solvent is 'traditional' still, because it works well, and the process is 'forgiving', albeit messy. Unless you are making thousands of identical parts, stay with solvent. If you go with Ultrasonic, get a copy of AWS D1.1 and look at the testing scheme for Stud-Welds. You should use that same testing scheme with your production UT welds. And yes, it will require destruction of the parts tested.

 

[ornerynorsk]

Perhaps an opinion from a second or third molder would yield different results in terms of ability to correctly produce the tooling. A single vendors limitation should not necessarily dictate a design limitation.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

 

[TheRingSmith]

Ornerynorsk,
We're actually inquiring with two ultrasonic welding equipment makers, since they would know best whether the taller e/d profile would be suitable. Thanks.

 

[tomwalz]

I would tend to advise solvent because the flushing process aids cleanliness.

You can get the same level of cleanliness otherwise with welding, but will it be done consistently.

Again, not sure what you need and particulate inclusion in a join may not be a problem.

Thomas J. Walz
Carbide Processors, Inc.

http://www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.