HP Officejet 6310 making grinding noise ...

You can't fix grinding without opening up the printer and checking where it's coming from, probably need a new gear. It's very hard to find service manuals for printers, most places do no release them except to certified techs that pay for the classes. And very few people want to deal with repairing InkJets.

I did a web search and could not find any service manuals for your model, you either have to contact HP (they may not help if the printer is not in warranty) or bring it to a repair shop which may cost as much as a new printer.