Scientific method

Question

What is the best way to use acetone to process ABS printed parts?

Research

Acetone is a solvent for ABS and makes it pliable. Bathing parts in acetone vapor will soften them.

Hypothesis

The more acetone in a chamber will produce faster results but in small amounts there will be a limit to the softening.

Test

Video evidence showed the results of the tests.

Analyze

The first part of the hypothesis was wrong, having large amounts of acetone in a chamber didn’t result in softer parts, the acetone had to be diffused. The second part of the hypothesis was correct, a small amount of acetone, readily diffused, would soften parts a given amount then stop.

Report

Paper towels provide a repeatable and disposable diffuser well-suited to acetone vapor bathing. Small amounts of acetone will process parts to set softness then stop. High amounts of acetone will process parts quickly but the process must be halted to avoid over processing the parts.

It is advisable to use a flat bottom in the chamber so parts do not take the shape of an irregular container.

Step 1: Equipment and Explanation of Steps

Five experiments were run to determine the effects of acetone on ABS prints. These were all scraps of a failed batch with particularly rough surfaces, perfect for acetone smoothing.

Equipment was simply

a glass bowl. I used a one quart bowl
a glass plate
two neodymium magnets coated in nickel
acetone
paper towels

For demonstration purposes an LED light was used to keep heat to a minimum.

I mentioned that the magnets were coated in nickel, this is what neodymium magnets are usually coated in so if they are the inexpensive off-the-shelf rare earth magnets you have the correct ones. Don't use rubber coated ones.

This experiment was performed in a well-ventilated room. Be sure to follow all safety guidelines on your acetone.

Step 2: Control Experiment

The first experiment was the control experiment. No acetone was used. No video recording was made because this was a time to establish a repeatable method. Time-lapse photos were taken but the result was too large so changes were made. An explanation of this can be found on the blog but the result was that nothing happened. As expected.

Step 3: 4 Inch Square Test Results

A small section of paper towel was cut, 2" by 2". Using paper towel area, as opposed to volume, makes measuring easy for anyone else who wants to repeat this experiment. The paper towel was soaked in acetone and allowed to fully saturate. Acetone won't dissolve paper the same as water so the paper towel won't soften as it would when dampened with water. Magnets were used to hold the paper towel to the top of the chamber, one magnet outside the chamber and the other touching the paper towels.

Time-lapse video was taken to show the acetone working on the plastic. Unfortunately a lens was not used to magnify the plastic while it processed so it's not clear what happened or how fast. However the end result shows that the rough surface had become shiny after processing overnight.

This technique is great to get a little bit of a shine without having to worry about a timer. Just pop the plastic in the vapor chamber with four square inches of acetone soaked paper towel and let it sit overnight.

Step 4: 8 Inch Square Test Results

For the third experiment eight square inches, 2" by 4", of paper towel were soaked in acetone. This doubled the acetone from the last experiment. Additionally, a lens was added so the experiment could be seen better.

Most of the processing happens in the first two hours which can be easily seen in the video. The effects were more dramatic than before but the pieces should be taken out after two hours so they aren't damaged. Fifteen minutes more or less won't hurt the print.

This technique is great for taking the rough spots off your print and adding a shiny finish but it should be timed.

Step 5: 16 Inch Square Test Results

Sixteen square inches of paper towel material were soaked with acetone and processed with the plastic parts. Time-lapse video showed the plastic softening then becoming weak with the high concentration of acetone. After processing the plastic piece wouldn't come off the glass plate because it was "soggy." There is video on the blog showing how pliable the piece was. After being removed from the acetone vapors for a few hours the plastic was back to the same hardness as before.

This technique will produce a very smooth surface but it must be removed from the acetone in less than two hours. Do not handle the pieces for eight hours or they may be damaged.

Step 6: Open Container Test Results

The last experiment used a shot glass filled with acetone which was set inside the chamber. Oddly, no effects could be seen on the printed pieces. Perhaps the acetone vapors were too heavy to leave the shot glass.

This technique does not work.

Step 7: Results and Conclusion

For an easy to follow recipe use four square inches of paper towel soaked in acetone. Let it process overnight and don't sweat the details.

if you need quick results douse 16 square inches of paper towel in acetone but stop after two hours.

A plate with a flat bottom is best. As the parts soften they can take the shape of the container. Any glass will work, even a mirror with no frame.

Step 8: About Me

Thank you for reading this Instructable. If you like it check out my site where I blog incessantly about my projects. There is a day-by-day write up of this project including videos not shown here and I explain the reason I didn't post a video of the control experiment.

I have lots of 3D printed projects and lots of projects which don't use a 3D printer.