Though this answer relates to an OfficeJet 8710 too big to fit in a carry-on, it does warn:
But more importantly, there was a bomb threat a few years ago that involved toner cartridges and thus the TSA has treated them in the past like potential bombs. While the ban is officially lifted, it just takes one zealous TSA officer to make a mess of your printer. Not advised.
What if my grandparents pack a smaller OfficeJet 3830 in a carry-on, without ink cartridges?
They can happily remove the printer from their carry-on and place it on an Airport Security Tray. Is this necessary though? Is it sufficient simply to notify the airport screener that their carry-on contains an inkjet printer?
Will they face any difficulties with airport screeners?