when i use the encoder with the printer switched off the other equipment works fine through the Arduino but when the printer is on and running then i get interference and my other stepper motor chatters.
What is your application and why?
What is powering the encoder when the printer is turned OFF?
What is the other equipment?
Can you please post a copy of your sketch, using code tags.
Can you please post a copy of your circuit, in CAD or a picture of a hand drawn circuit in jpg, png or pdf?
Can you please post a picture of your project.
You have the project in-front of you, we don't.
You know how it is wired, we don't.
You know how you are powering the stepper motor and arduino, we don't.