UPDATE 15/06/2018
Hare is a microswitch support that can replace the original one that need to be cut away.
It is necessary also to cut part of the top side of the backplate to allow the hotbed adjustment nuts and screws to pass over it (the cut size depends on your adjustment nuts).
With this last step you can gain more printing area going up to 270mm carriage excursion.

----------------------------------------- 17/5/2018 -----------------------------------------------
This is not really an extension, it is just a modification of the bearing position under the hotbed.
Originally the printing area on the Y axis is 200mm, changing position of the bearings increase this to about 250mm.
Just replacing the supports under the bed and putting everything back on the traks the increase is about 25mm.
You need to make the holes on the plate for the cable ties that holds the bearings.
You may need to replace the original screws with some with a lower profile. Nuts on the top side of the plate.
To go the further 25mm there is the need of changing place to the end stop microswitch of the Y axis and to check if there is clearance for the hotbed level adjustment wingnuts to pass over the backside frame.
This is not done yet as for the moment I don't need more printing area, so I didn't design a support for the microswitch, but it will be done as soon as I get a bigger glass for the hotbed ( I mostly print with PLA so it's not a big deal to have the glass bigger than the heatpad).
In my case the level adjustment knobs are too low to pass so when will be the time, I'll have to remove a bit of the frame.

It is necessary to change y_bed_size in "configuration.h".

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