fairly quick one here…..
Make sure your bed rails are parallel by slackening one screw and manually moving the bed……………..
The bed moves front to back on some parallel rails – those two in the middle.
It’s held on by two carriages as shown below, these hold the 3 wheels per carriage tight against the V Slot extrusion to form a fairly sturdy linear rail….
Those two V Slot extensions need to be parallel for the system to work correctly. …
I’ve been printing some test parts and, quite literally, overnight, I went from being able to print stuff….to not being able to print stuff – these things are darn finickitey!
During a quick check, I felt underneath and tried the wheels for wobbly-ness…Maybe a screw had come loose?…I found that one wheel (the back left one of the pair) was ‘freewheeling’ and not touching the v slot as firmly as the other five wheels….see the blue arrows below
This meant that the rails weren’t perfectly parallel….the left carriage was being pulled a tiny amount inwards, twisting and lifting twheel from the v slot when it traversed the rail
How to fix…..
Simple…see the screw right by the Wanhao Rhino below..the rails are held with 4 of them…Slacken one off, so the rail moves a little left and right…..Now, Move the bed manually and feel the wheels, if they’re all tight and moving, great, bring the bed closer to the screw and tighten it up.
you slackening the screw allows the rail to find it’s own parallel setting – if it’s running nicely, it’ll be parallel with the other rail!……
for me, the back left, as that’s the wheel that was clearly lifting – implying the back left was too much ‘in’ …making a narrower distance between the back of the rails than the front…
That should make your bed run nicely………….Of course, you’re stuffed if BOTH rails are off centre, you’ve now got a bed running perfectly on parallel rails that aren’t parallel to the frame…..which itself may not be paralllel….3D printer parallelogram inception!