one corner always different height to bed

just started to test on big print that very much utilize the whole bed, its 200mm x 200mm, and my model size is lat on the bed 160mm x 160mm, also tried 140mm x 140mm, same result

the 10mm/s on the corner of 0,0 always about 0.2mm or 0.3mm higher, which makes it 0.4 to 0.5mm with a 0.2mm first layer causing not stocking flat on the bed, I haven't let it print for long, 4 layers and I stopped it, there was no curling, everything flat, it was a test to see how well the first layer goes before I go off do other things and let the printer work on its 33hours print, all other area are very even except the one corner

my probe positions in firmware are

#ifdef AUTO_BED_LEVELING_GRID

#define LEFT_PROBE_BED_POSITION 35
#define RIGHT_PROBE_BED_POSITION 165
#define FRONT_PROBE_BED_POSITION 10
#define BACK_PROBE_BED_POSITION 190

offset x 31mm y 0mm z -1mm

any idea anyone? it couldn't be the bed since a 140mm/2 has the same last 10mm at the end of the same corner as the 160mm/2, that means what was lifted in the 140mm print is now flatten when printing 160mm/2

I have tried that same thing on 2 borosilicate glass as well, no differences, I put the 2 pieces glass and the aluminium bed together, the all flatten together, no gap....

Edited 2 time(s). Last edit at 10/01/2015 05:53PM by deaconfrost.

The gap at 0,0 is always there, even when you navigate the nozzle manually ?
I can only think of table wobbling during the print, which would cause the table to drop the first 10mm after the turning point.
Is you mechanic slop free and the belts have no backlash?
-Olaf

Yes all good and tight. Except I hear an occasional click sound from the z axi threaded rod. Which is the one over by 0,0 I replaced that with brand new rod and nut. After one print and it's doing the same, click click at certain height. Then I replaced both side. Again after first print, click click click, everything else are in good shape, smooh rods are straight no bend. I'm puzzled.

Ps. I even took out the spring 's of the bed. Using spacers to level that the best I could which should be fairly level. I checked before print. If there was any leveling offset on the bed, there wouldn't be anymore than .5 of a mm, there should be no problem for the auto bed leveling to compensate that, but just that one corner I always have trouble with. Added in an extra washer last night, nothing changed, same issue. At start I thought it was due to the servo arm has slight different angle every time it retracts and extend, but it's still the same after switching to inductive sensor, but all other area has improved dramatically, so the servo was causing some issue but that's no longer the cause of the problem.

Edited 2 time(s). Last edit at 10/02/2015 05:36AM by deaconfrost.

I played around in the firmware, got the probe to measure 0,0 with offset set on nozzle being -31 on y axis, now that corner is perfect, but the opposite corner in diagonal is slightly higher, WTF???

it actually seems ok, it is still printing the first layer, I open the door and try scrap off the corners while its doing the infill, they won't butch, couldn't lift them with a thin blade, thats good enough for me....

Edited 1 time(s). Last edit at 10/02/2015 12:01PM by deaconfrost.

Sounds like your bed is screwed down on all four corners...
This is a nightmare to level without making the bed uneven ( bulging ) even with springs. I´d say it is impossible to level it unstressed with washers.

A 3-point levelling system is the best way to keep your hair
-Olaf