My extruder assembly is banging against the printer frame making a loud noise

If your extruder assembly is banging against your printer frame you most likely have a faulty Endstop Switch. The job of the endstop switch is to trigger a STOP command to the micro-controller so that your extruder assembly knows when to stop moving in that direction. You can compare an endstop switch to a stop sign that is hard-wired to your car's brakes...if it is triggered your extruder assembly is supposed to stop immediately. If the endstop switch is not working properly then your extruder assembly will not know to stop and thus it will continue moving and bang into the side of the printer until the printer is turned off.

How to check if your endstop switch is working properly:

In this example we will focus on diagnosing the endstop switch that sits on the right gantry mount (X-Axis Endstop Switch). Turn your printer off and manually move your extruder assembly to the middle of the printer so that it is not pressing up against any of the walls (left, right, rear, front of the printer frame). Now, look at your machine from the front view and locate the right gantry mount towards the right of the printer:

Take a look at the endstop switch on this gantry mount. Notice in the pictures below that there is a little metal wing clip that lights up the endstop switch with a red LED light when it is pressed:

Turn your machine back on and go ahead and push in the little metal wing clip and confirm that the LED is lighting up. If it does not light up then make sure that the connector to this endstop switch is firmly in place. If everything looks correct and the LED is still not lighting up then you may have a bad endstop switch. If you do not see the metal wing clip at all then it may also be possible that the metal wing clip has fallen off during shipping and this is the reason you are experiencing the problem.

In addition to this endstop switch, there is one behind the build platform wall (Z-Axis Endstop Switch) and also another at the upper rear on the left side (Y-Axis Endstop Switch) of the printer. You should periodically check that all three of these endstop switches are lighting up when the metal wing clips are pressed.

If you need a replacement Endstop Switch for your D4 series printer you can find them HERE.