Full conversion of a CR-10 3d printer to linear rails. On each axis I have 2 linear rails, including the X-axis. This is not needed, however I decided to do it for more rigidity and to be able to attach heavier direct drives. Here are the linear rails I used:
Y-axis: 2x500mm MGN12 w. 2 H carriages
Z axis: 2x 500mm MGN12 w. 1 H carriage
X axis : 1x400mm MGN12H + 1x400mm MGN9H
I bought the rails from RobotDigg and Hiwin (MGN12 on the X axis) and I am very happy with their quality. There are cheaper rails and maybe they are OK for a 3d printer, but I didn’t want to risk with noname brands.
Check the linear rails prices:
Amazon: https://amzn.to/2WYLP3p (affiliate link)
Aliexpress: https://s.click.aliexpress.com/e/_d8x... or here for Hiwin: https://s.click.aliexpress.com/e/_d6a...

For black oxydized linear rails check the ones from RobotDigg https://s.click.aliexpress.com/e/_9yOk2s. I used them om my DIY Voron Switchwire 3d printer shown here    • Voron Switchwire - 3d printer review ...  , and they were quite cheap for the quality.

Other parts and printed parts:

Y axis:
2x460mm 2020 extrusion (buy 1m and cut it) https://s.click.aliexpress.com/e/_dUw...
Gates-LL-2GT 9mm belt 100cm (I bought 110cm to have some extra) https://s.click.aliexpress.com/e/_dVm...
2020 aluminum profile triangle connectors https://s.click.aliexpress.com/e/_dWy...
9 or 10 mm timing belt pulley (5mm bore) 20 teeth https://s.click.aliexpress.com/e/_dXq...
9 or 10 mm idler 20 teeth https://www.aliexpress.com/item/32738...
Printed spacers 7mm (link soon)
Printed Y endstop&stepper holder https://www.thingiverse.com/thing:426...
Drilling template https://www.thingiverse.com/thing:426...
Y tensioner for 9mm belt: https://www.thingiverse.com/thing:347...

Check also this alternative solution for the Y axis if you want to avoid drilling the hotbed support (comes with Hiwin rails at good price): https://s.click.aliexpress.com/e/_dTQ...

X-axis:
2xM3 idlers 16 teeth
1xM5 idler 20 teeth
Modified X tensioner, Carriage for MGN12 and MGN9 and modified “Tank” print head, Modified front X motor plate: https://www.thingiverse.com/thing:425...
This direct drive is for BMG or Trianglelab dual drive extruder: https://s.click.aliexpress.com/e/_dTb...

// Check also my adaptation of the Voron Afterburner direct drive for CR10 if you want different print head: https://www.thingiverse.com/thing:430... - see it in action here    • Afterburner direct drive on a CR-10   //

Z-axis:
Mounting elements for the right side of the gantry:
https://www.thingiverse.com/thing:297...
https://www.thingiverse.com/thing:374... (CR-10 only, alows to implement dual Z with one stepper)
Mounting element for the left side: https://www.thingiverse.com/thing:425...
Frame braces: https://www.thingiverse.com/thing:311... + modified top right part (for CR-10 and dual Z with 1 stepper) – https://www.thingiverse.com/thing:426...
You will need also some M3 bolts and nuts with various sizes, M3 T-nuts (buy at least 50) and M5 T-nuts (buy set of 20)