AM8 - 200x300 buildplate - 350mm Z height

As I was considering to convert my A8 to AM8, I thought it should be possible to modify the build plate area as well.
These are the parts I created in order to accommodate an Y carriage for a 200x300 heated bed, without having to cut in the Y carriage to make space for the motor in the original mounting position (and not having to mount the motor on the back of the frame).
Also, I increased the Z axis to approx 350mm with the standard X axis carriage, by using 550mm extrusions (requires longer threaded and smooth rods).

The challenge of using a larger buildplate without cutting in it can be approached in 4 ways:

1. Raise the Y carriage using spacers on the bearing blocks on the Y carriage, and thereby reducing the printing height (Z axis)
2. Raise the Y carriage by using spacers on the Y rod holders (or design new Y rod holders), and thereby reducing the printing height (Z axis)
3. Lower the position of the Y motor - making tensioning the Y belt a bit more difficult, but does not reduce Z height.
4. Place the Y motor on the back of the frame

I decided to go for option 3, in order to avoid decreasing my printing height (Z axis) - and to keep the Y motor inside the frame.

I changed the Y extrusion aluminum profiles to 480mm, and I use 500mm long 8mm smooth rods for the Y axis and Z axis.
The back of the Z axis extrusions are located 195mm from the back of the printer when using the X carriage https://www.thingiverse.com/thing:2193695 (I think this measurement is 127mm on the original AM8).

The center of the heated bed need to be calibrated after build - check for example https://www.thingiverse.com/thing:2280529 on how to do it.

The Y motor and Y belt idler mount are mounted on the inside of the frame - and the belt holder/tensioner is located on the bottom side of the Y carriage. I know this makes tensioning the belt harder/more difficult - but again: how many times do you need to tighten the belt, if you use a quality-belt ?

The Y carriage I use for my modification: https://www.aliexpress.com/item/Large-Size-Aluminum-Y-Carriage-Plate-XL-300x200mm-Prusa-i3-RepRap-3D-Printer-Upgrade/32727730118.html

Y belt holder/tightener was inspired by https://www.thingiverse.com/thing:896911

I have added https://www.thingiverse.com/thing:2067676 as Z anti-wobble - which required me to lower the Z motor mounts all the way down, so that they touch the frame stabilizer plate for the Z axis.

Using the E3Dv6 hotend carriage from https://www.thingiverse.com/thing:2193695 it is possible to achieve a printing height of 350mm (that is what I am able to push the Z axis to - without running into problems).

Update 20170802:
Y motor mount v3 added - this one does not require screws/bolts in the top of the extrusion, but will hook into the slot in top of the extrusion for better stability.

Update 20170818:
Z rod holder (only included for left side, mirror it in your slicer for the right side version) was modified from the original to avoid the threaded rod from moving too much, as I also extended the Z axis during my modification.

Update 20170828:
New Y motor mount, new Y idler and new belt holder/tensioner. Position of belt raised 10mm higher - closer to the carriage, in order to minimize the risk of any wobble...
Y rod mounts added - with end-stops in order to be able to use 500mm rods with the 480mm Y extrusions.

Update 20170917:
Added Y belt holder/tensioner for 219x219 Y carriage (https://www.thingiverse.com/thing:2325206) - it has not been tested, feedback welcome. This part will probably need to be split up when printed - and supports are needed for the largest part.

Update 20171006:
Y endstop bracket /rod holder modified to pull endstop switch 4mm back.

Update 20171107:
New Y idler added (with a height, that will fit a 2020 extrusion). The idler pulley has been recessed/countersunk a bit into the mounting plate, giving 3 mm more room (less chance of collision with the Y belt holder/tightener).

Update 20171206:
On my original A8 I have had issues with the Z axis getting out of alignment. In order to avoid this, I have created two new Z rod mounts for the top with 22mm center distance (the original AM8 motor mounts have 22.2mm center distance - I will ass my own motor mounts later).
These Z top mounts will each be fitted with a KFL08 bearing on the bottom side of the bracket, and a 20T pulley mounted on the threaded rod. Besides this, a 20T toothed and a 20T smooth idle pulley will be needed on each side - and a GT2-900mm belt to connect the two sides.
The KFL08 bearing will be mounted from the bottom using 2 M5x12 screws with 2 M5 nuts on the top. The 20T idle-pulley (mounted to the center of the printer) with be installed using a M5x25 screw and a M5 locking-nut (and a nut on top to keep it in place). The 20T toothed idle pulley will be mounted in the "adjustment" position with a M5x35 screw and a locking nut (and a nut on top to keep it in place).
Mounting order:

1. Insert M3 nut to be able to tighten smooth rod
2. Mount the bracket on the AM8 frame
3. Mount the KFL08 bearing
4. Mount the smooth 20T idle pulley
5. Insert the threaded rod, adjust the X axis in height - then adjust the pulley in the top of the threaded rod to align with the smooth pulley and tighten the screws of the pulley.
6. Tighten the threaded rod in the flexible coupler in the bottom of the threaded rod
7. Tighten the screws in the KFL08 bearing to the threaded rod
8. Mount the toothed idle pulley - wait to tighten the screw
   Now mount the other side - same procedure - and then mount the 900mm belt. Now you can tighten the belt, and tighten the screws for the toothed idle pulleys.

I know some people will claim the will give Z wobble. This is true, unless you "mechanically" disconnect the threaded Z rods from the X carriages. That id why I use these (https://www.thingiverse.com/thing:2067676) on my Z axis.
Photos will be added later.

Update 2018-04-04: Added STL's for Z motor mounts and Z rod holders - with additional material added for better strength (I saw some like these somewhere - but cannot remember if it was on Thingiverse).