PRACTICAL ways to finish ABS parts (Page 1 of 2)

I sanded some parts of a flap wheel yesterday. Still a manual method, but easy to get into the contours.

Where I used to work we had a acetone vapor cleaner that we used on glass and silicone parts. It consisted of a stainless steel cylinder about 16" tall. It had a heater bonded to the bottom and a couple of coils of copper tubing soldered around the top lip. We used a swamp cooler water pump in a bucket of water and ice to circulate the cooling through the copper tube. when the heater was plugged in the acetone vapor would come up to the level of the copper tubes and condense on the side. we would lower the parts in a basket into the vapor and wait 30 seconds or so and slowly remove it. As long as you didn't move things fast and kept the air drifts away you wouldn't eve. smell the acetone. It was pretty cheap and wouldn't be too hard to recreate.

TiM

Some other fellow once posted about just using a paint can with a paper towel wet with acetone, and held the paper towel to the can sides with magnets. Works well for me, but I only use this method for finishing every now and then. I think it really depends on what your definition of finishing is. Are we talkin' bout just getting rid of the layer lines, or are we finishing the parts to be used in appearance models? If you need to finish them to use for appearance models then using regular bondo or glazing putty will work well enough to smooth out the surface for painting.

Never met this guy before - interesting models with the Solidoodle.

Wouldn't a Q-tip be easier and safer then a paper towel?

Yes, correct. If you used the qtip with acetone on the model, it leaves a white residue behind. I use the qtip to apply acetone when I need to weld pieces together. But then I put it in the vapor bath for about 5 minutes.

You guys are correct in understanding the method I was trying to describe. Unfortunately I do not have any before or after shots. I do have one item handy here that I used this method of finishing on and another of the same part that was left unfinished. I'll post the two pics in a bit.

Ian's method probably works way faster. I chose not to use his method though after trying it out outside, but the smell was worrying me as my house is on the main route kids take to walk to school, and I was worried the parents would complain to the city or something. The paint can method seems to work best when I put the part in for a few minutes then pull it out to dry. Then put it back in for a few minutes then pull out again. I do this until the surface is how I want it. You have to adjust the time the part sits in the vapor according to its size and/or features. What I like about this method is I have more control over how much the surface is altered by the vapor. I can also do this finishing in my room and not smell any vapor fumes as the paint can lid seems to do a decent job of sealing even if I don't push the lid on all the way.

First two pics are of part using the paint can method. The second pair of pics are of the part left unfinished.

How much acetone do you use per few-minute-session?
*I don't have a set amount that I use for time durations. I just put the paper towel inside the can held with magnets. Then pour in some acetone that would look like to be the right amount to get all soaked up into the paper towel. I try not to have any pooling at the bottom. So paper towel is soaked enough to be fully coated, but not so soaked that I get pooling at the bottom of the can. As long as the paper towel is good and wet I figure it's good to go. (roll the can around so that the liquid gets all soaked up by the paper towel)

Do you reapply acetone between pulling the piece out?
*I only reapply if the paper towel looks to be drying out. I tend to use the inside temp of the can to gauge this as well. So once you put acetone in the can and get the paper towel all saturated, reach your hand inside and without touching anything feel the temp. It'll be pretty cool in there. As long as the can feels that cool inside I figure it good to go.

On average how long does the process take?
I have no average really, I take a guess on the fly judging by how big the part is, if it has complex or thin features. For instance that extruder fan mount got left in the can for too long when I was first trying this out. The thin wall that separates the extruder nozzle from the fan had started to droop a little. I guess when I think about it maybe for complex things I'll put them in for about 5 to 8 minutes at a time, and for simple shapes 15 minutes at a time. I'll do this cycle of letting them sit in vapor and then in fresh air however many times until I get what surface I like, but you can cross the line of it looking good and going too far. So it really depends on the object you're sticking in there. If you really want to be cautious I would just put it in for 5 minutes at a time and adjust from your own results.

What do you mean by "drying"? Is this allowing the piece to dry or harden?
*I just mean pull out the part so that it sits in fresh air for a bit. This helps to keep the part from accelerating into a droopy state. If you leave the part in for too long it seems it become gummy like a gummy bear, then starts drooping, and then takes forever to dry out/harden. Letting it dry out every few minutes also makes it easier for you to get the surface you desire without overdoing it.

Is there any noticeable amount of drooping due to the process?
*Drooping will occur if you leave the part in for too long. You'll have to experiment with what's a good amount of time for letting your part sit in the vapor. Even the solid simple shapes will succumb to this if left in for too long at a time.

Is there any problem with the piece sticking to the bottom of the can?
*I put the piece on a metal bracket the keeps it up off the bottom of the can just in case excess pooling occurs in the can, even though I try to avoid putting that much in there. I don't have issues with the part sticking, but I suppose it could happen.

I use the rare earth magnets just because those are what I already have on hand. I imagine any magnet should be fine. The metal bracket was just some random bracket I grabbed from the wood construction section of home depot. It was just something I could place my printed part onto so that it was elevated from the bottom of the can. The bracket does seem to prevent the vapor from doing its job on the bottom side of the part since it's covered by the bracket, so you may want to try wire mesh or something to allow the vapors to reach the bottom-side, but then that may leave a mesh texture on the bottom of your printed part.

I like the paint can idea. Maybe a little simplier.

Can you use tupperware with acetone? Otherwise get a small pot, get a small kitchen strainer or soap rack wash rack etc from the dollar store flip it upside for your part stand.

pot
soak paper towel on bottom
flipped stand
place part in there
put lid on

That is NICE, vince!