The first thing to do is strip down the inkjet to the bare essentials. You should probably start by removing the covers and observing how it works. Print a few pages and see how the paper sensor works. On my lexmark there is a little plastic lever that is lifted by the paper as it is fed into the printer. This lever moves a plastic flag which is blocking an optical sensor on the circuit board. The sensor is blocked when there is no paper/ unblocked when paper is present. Once you have figured out how it works, you need to remove anything that is under where the paper would be. This includes any paper feed rollers, guides, or housing/framework. Don't forget to measure the distance between the print head and the paper (I did!). The paper feed motor on my printer is a stepper motor (On HP printers it is a dc motor with an encoder). I separated the motor and gearbox so they could be relocated to a stationary location. Some people remove the pcb so it can also be relocated. The the idea is to lighten the carriage but I decided it would be too much hassle to extend the ribbon cables to the print heads so I left it where it was. What I was left with was a carriage that I could mount on some linear slides so that instead of feeding a piece of paper under the print head, the printer would move over a bin of the build medium.