Edit, read this post on my Ipad and it had all the wrong pictures including some from a future post. Cleared my cache on my PC and noticed the same thing was happening. Have now fixed the weird problem.
Creality got back to me about the unlevel c-slot, their response,
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I think it is unlikely that the frame is the problem. If you are not sure if it is square though you might be best to lay it on a flat surface then tighten up the bolts to make sure the base is flat. There is normally a bit of play in it that you can adjust a bit.
Once you have done this you should be able to assemble it again and it should go together fine. It might be worth checking the uprights and the top bar are not bent though.
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Anyway, to recap.
Rebuilt with perfectly square frame.
Dual extruder, esteps calibrated (and stored).
I've done the hot end fix, extrusion is working 100% perfectly (capricorn tubing)
Lock Nuts put on the end of the bed levelling screws so they don't turn when I adjust bed level.
Springs replaced with yellow springs.
Tightened yellow springs all the way, then undid then about 3 turns, then set my end stop (not needed now as have bltouch), the adjustment wheels are now quite stiff so I haven't got to worry about them vibrating around.
Replaced magnetic bed with glass bed, reset my z stop (although not needed now)
Added BLTouch (also using it to set my Z stop).
Installed correct firmware from Bigtreetech for BLtouch being used as Zstop
Homed with my BLtouch, then calibrated my z offset (and stored settings).
Did 4 corner paper levelling to get bed as level as possible.
Did BLtouch 25 point autolevel and stored.
Got a level test STL, sliced it in Cura and kicked off a print. I came into the room as it was near finishing and heard loud clunks where the head was smashing through the rear left of the print (retraction and z hop are enabled in Cura)
The file I was printing is the CHEP_bed_level_test.stl that I got from
https://www.thingiverse.com/thing:3235018
Here is the result
Here are my Cura settings
Most of the rest of the print looked OK except for a layer shift in the final layer (and can also see a layer shift about 1/2 way up everywhere. I'm not sure whether this may well have something to do with the nozzle clunking across the print rather than some other problem.
I started the print from scratch (after again running 25 point BLTouch leveling and storing it), I notice at the start of every square, it's over squished, then I stopped the print.
I downloaded another level test from someone else, only gcode no stl, so edited gcode in notepad++ and altered the nozzle to 205 and bed to 60, and added
M280 P0 S160 ; BLTouch alarm release
G4 P100 ; delay for BLTouch
G28 ; home
M420 S1 ;Load saved ABL Mesh for BL Touch
Here are pics of the left hand rear and the right hand rear.
It doesn't come out properly on the left hand photo, but the filament at the far left corner (not the circle) is much more translucent than the right hand
Also the filament on the left hand pic is almost double the width of the right hand.
I've just given it one more go, this time replacing the gcode line
M420 S1 ;Load saved ABL M
with
G29 ; auto bed levelling
so that it does the BLTouch 25 point levelling before doing the print.
It's just finished printing, it's 100% identical to the previous left and right hand pics.
I've run out of ideas of what to try next.