If your Titan is grinding filament then the first thing to check is your filament tension, rotate the thumbscrew clockwise to increase the tension, you will know if you have applied too much tension because the motor will begin to skip steps. (make a clicking sound)
The second reason could be you are trying to print too cold, all-metal HotEnds such as ours often require a slightly higher printing temperature than other HotEnds.
If after trying this the filament grinding is still occurring then there may be a jam in the nozzle, try doing a cold pull to see if there is any residue in the nozzle causing a blockage.
*If you are using the Nozzle X on your HotEnd please find cleaning methods - https://e3d-online.zendesk.com/hc/en-us/articles/360016177978-Nozzle-X-Cleaning-Guidelines