Acetone Surface Finish Weakening ABS

[pyronaught]

I've noticed that when using acetone to smooth out the surface finish of an ABS part, the acetone seems to wick into the entire thickness of the part and weaken it. I've had press-fit parts split (perpendicular to the layer plane) and threaded parts pull themselves apart when surface finished with acetone earlier in the day, but those same parts have no problem without the acetone finish. Is there a certain amount of time that must elapse following acetone treatment before the part regains normal strength, or is this just a permanent defect? The surface is completely dry in just an hour, but the acetone that worked it's way down below the surface just seems to just stay there even several hours later. Perhaps this is like paint being driven in when the surface is force dried or the paint is applied too thick-- which can cause the underlying paint to take months to fully dry. Maybe the smoothness of the acetone finish combined with the rapid flash drying that occurs on the surface creates a barrier to internal evaporation just the way paint does.

[jimc]

its not permanent. acetone will flash off but it takes time. how much time depends on many things. temp, humidity, amt of acetone applied, duration of exposure and thickness of the part. as a general rule of thumb at room temp your looking at 24hrs. if its real cold, the part is thick and the exposure to it has been a long time where it can work its way deep into the part then it can take even longer.

[pyronaught]

That's good to know, using acetone to smooth out the surface is certainly a lot easier than sanding and produces a better looking finish. I'd hate to have to give that option up.

[hybridprinter]

Why not vapor smooth?

[pyronaught]

I've never looked into that method. If the vapor is acetone then I would imagine it still wicks into the plastic like brushing it on does.

[jimc]

yes it does. it just does it more evenly.

[hybridprinter]

There is another chemical that stratasys uses in their finishing touch vapor system.. Maybe that wont suck in?

[jimc]

there are many that will work with abs. all solvents that will attack and melt the surface will get into the plastic. thats really the whole point and how it works. even abs glue for pipes that you get in home depot is the same thing. its just solvent, usually mek and sometimes tetrahydrofuran with abs resin in it. it melts the 2 pieces together then after 24 hrs or so the solvents work their way out leaving a solid piece.