Hi there, just wanted to share a quick trick I discovered.
Fine graphite powder from motor brushes can be cleaned from a plastic part by first covering the part with a spray oil (I used the standard Ballistol one), rubbing in the oil, then cleaning the part in soapy water. I suspect the same should also work for laser printer toner, though I haven't tried that one.
I was repairing a food processor today whose motor brushes had partially disintegrated, spreading a large amount of very fine graphite powder all over the inside of the case. I had a really hard time at first removing that graphite powder, as neither soapy water nor isopropyl alcohol seemed to do much to it. I suspect water can't get the graphite powder into suspension since water is polar and graphite is not, and isopropyl might just be too small molecules and thus too small van-der-Waals forces compared to the van-der-Waals forces sticking the graphite powder to plastic. So first covering the part in oil gets the graphite into suspension inside the oil, and then the soapy water washes off the oil with the graphite suspended in it.
Do you know any other tricks on how to remove graphite dust? I wasn't able to find much on the internet. Is there maybe even commercial cleaning agents for that?
At work, we have an ultrasonic cleaner. I wonder if that would help.