Neptune 4 Printers - bed isn't level

Issue

You have disassembled & reassembled your Neptune 4 3D printer gantry for maintenance or parts replacement, went to level the bed, and found that you ran out of travel on the bed-height adjustment wheels on one side. You may also find your prints having layer issues, or the printer may make unusual noises when the printhead travels from side to side.

Cause

Your X-axis gantry is no longer parallel to the bed. The motorised screw shafts that move it up and down, which are kept in step by the belt at the top, have become out of step with each other, resulting in the gantry being higher one one side with respect to the bed.

Fix

You will need to "tram" your gantry. The process involves releasing the tension on the top belt, and turning the screw shaft on one side until the gantry is level again, before re-tightening the belt.

1. Use the Prepare menu to raise the gantry to around half-way to the top
2. Turn the printer off, and remove the model cooling fan assembly behind the print head
3. Wind the the plastic bed-height adjustment wheels under the bed all the way tight 
4. Back them all off all an equal amount by several complete rotations

5. Loosen the bolts in the red boxes on top of the gantry (not the ones the arrow points at)

   

6. You'll find the top belt is now loose - if it is not, loosen the other side's top bracket screws as well
7. Slide the print head horizontally to the middle of the gantry
8. Place a soft-drink can on either side of the print head so that the gantry will be directly above the cans

9. 

10. Turn both grey connectors on the bottom of the screw shafts until the gantry touches one of the cans

    

11. You should see a gap between the gantry and the other can - that side of the gantry is too high
12. Hold the grey connector on the low side, and turn the high side connector only until that side touches the can
13. You should hear or see the belt skipping on the low-side belt cog as you do this

14. Once the gantry is level on both cans, push the top bracket in the arrow direction & tighten the screws so the belt is under tension again

    

15. Run the gantry up and down by turning the grey connectors together and check there is no gap difference between the two cans when the gantry touches them
16. Remove the cans, turn the printer on, and level the bed using the Level menu