See the new and improved V2: https://www.thingiverse.com/thing:2591848

*** COMMENTS WELCOME ***

This is a printer I've been designing, which I've borrowed a couple things from the Hyper Cube Evolution. This will probably take a long time to gather the parts together, due to price, but I have some parts already. Things that are missing is a part cooler and which board to use.
More info:

Design Goals:
Minimum maxium speed of 100 mm/s (150 mm/s would be great, 300 would be awesome) with decent precission and accuracy.
350x350x500 build volume.
Extra space to make sure the carriage completly clears the bed.
100 Micron resolution

Features:
Core XY kinematics.
3030 based frame.
6mm thick aluminum bed
24V 350x350 mm silicone heater (300-325W)
120V 350x350 mm silicone heater
Polyurethane Steel Core 2GT belts.
Easier A&B belt tensioning (stolen from the Hyper Cube Evolution project).
Hiwin linear rails, becuase round rods and the bearings are not that great.
Proper bearings, meaning that toothed bearing should be used when the tooth side is against a bearing.
Boden setup, less weight on the XY = more speed.
Real E3D hotend, less issues with filament jamming.
Olsson Ruby nozzle, print a wider range of filament with out having to replace.
32-bit controller, faster processing with better precision.
Designed for higher amperage 12V setup, but use a 24V supply. Lets keeps the fires out of this.
Solid state relay for hotbed. Just because we can and, well, less fires.

Better wiring:
GX12-6 Connectors.
HE0-HE1
1 Thermistor +
2 Thermistor -
3 GND
4 Heater +
5 Heater -
6 GND

FANS (12V)
1 HTB+
2 HTB-
3 NC
4 NC
5 PRT+
6 PRT-

E0-E1
1 BLK
2 YEL --- Not used?
3 GRN
4 RED
5 WHT --- Not used?
6 BLU

Probe
1 5V
2 12V
3 GND
4 Signal
5 GND
6 Z Min

GP0/X Endstop - GP1/Y endstop
1 5V
2 12V
3 GND
4 End Stop
5 GPO
6 GPI

BOM:

    Screws:
        M4x30:
            8   for Pillow Bearing Mounts
            
        M4x15:
            8   for Z Axis Motor Mounts
            8   for Bed Linear Rail Mounts
            40  for Feet
            12  for Corner Idler Brackets
            12  for Coner Motor Mounts
            1   for Y Axis End Stop
            2   for Connector Board

        M4x10:
            8   for Lead Screew Bed Mounts
            1   for Badge
            136 for corner brackets

        M3x50:
            2   for Corner Idler Brackets
            14  for Gantry Sides
                
        M3x30:  
            2   for E3D V6 Hotend J12A3-4-Z

        M3x15:
            2   for Y Axis End Stop
            2   for X Axis End Stop
            12  for Gantry Belt Adapter
            2   for E3D V6 Hotend J12A3-4-Z
            26  for 12 645 Rail

        M3x10:  
            8   for Z Axis motor mount
            8   for Corner Motor Mounts
            2   for X Axis End Stops
            64  for 15 630 Rails
            34  for 15 670 Rails
                
        M3x8:   
            16  for Bed Linear Rail Mounts
            2   for Gantry Rail Mount

        M3x8 Counter sunk:
            4   for Bed
    Nuts:
        M3:
            2   for Corner Idler Brackets
           
    Inserts:
        5x5x3:
            5   for Gantry Mount
            10  for Gantry Belt Adapter
            2   for E3D Hot End v6
    Spacers:
        5x20x3.2 Harin:
            20  for Gantry Sides

        5x5x3.2 Harwin:
            6   for Corner Idler Brackets
            10  for Ganrty Sides

        5x6x3.2 Harwin:
            4   for Gantry Sides

    20T Toothed Bearing Idlers:
       4  for Corner Idler Brackets
       2  for Gantry Side

    20T Smooth Bearing Idlers:
       2  for Gantry Sides

    Misc:
        4   NEMA 17 Anti Vibration Damper
        68  3030 Corner brackets
        2   5mm to 8mm couplers
        4   KP08 Bearing
        2   Opto endstops
        1   LJ12A3-4-Z/BX Inductive Sensor
        1   E3D V6  (24V 60W)
        4   Hiwin MGNR15R630CM Rail + MGN15CZFC Block
        2   Hiwin MGNR15R670CM Rail + MGN15CZFC Block
        1   Hiwin MGNR12R645CM Rail + MGN12H Block
        2   20T 5 mm bore Gears
        27  GX12-6 Male/Female Connectors  
        1   6x30x802 Carbon Fiber Bar 
        10  3030x800
        12  3030x740
        8   3030x640
        2   2020x802 
        4   2020x518  
        2   8mmx8 Lead Screws
        2   8mmx8 Anti Backlash Nuts (screw hole threaded)
        2   8mmx8 Lead Screw Nuts
        1   406x406x6mm Custom Aluminum Bed
        225 3030 M4 T-nuts 136 40 24 12 12 1 
        98  3030 M3 T-nuts 64 34
        24  2020 M4 T-nuts