The CR10 has a single Z axis leadscrew and I have no issue with this it really produces superb prints. From an engineering point of view a better idea would be to have a leadscrew at both ends. There is an upgrade kit available which uses a second stepper motor but I understand these can get out of sync when power is switched off and on and the bed must be re leveled every time.
My solution links the screws with a toothed belt and is driven by the existing single stepper. It cannot get out of sync.
All the parts cost less that £12.00 ( US $16.00) including delivery!
There is a bit of metalwork involved but you only need a saw. file and drill. If you really cannot do metalwork I have designed a printed bracket with the same dimensions. Be warned though this has not been tried out but it should be OK.
Parts needed include
600mm leadscrew and nut https://goo.gl/fM8znL
GT2 Aluminum timing belt pulley 36 teeth : https://goo.gl/hv9dVU ( 2 required be sure to order the 36 toothed one)
GT2 852mm Timing Belt: https://goo.gl/iXa4sv ( be sure to get the correct length)
Flexible Shaft Coupling: https://goo.gl/qfUhEe
You also need
2 x M5 x 16 screws and Tee nuts.
2 x M3 x 16 screws and nuts.
A few washers.
2mm sheet metal for the bracket if not using the printed one.
Creality 3D printer: https://goo.gl/wXrkMi
Discount code 20%off for CR -10 3D printer: bg3dprinter
3D printer special page: https://goo.gl/xEdxVB (15%off coupon: bgprinter)
STL files https://www.thingiverse.com/thing:2569379
The existing leadscrew is replaced by a longer one so that a toothed pulley can be mounted above the printer frame.
The existing leadscrew is reused on the other side and a bracket added to connect the leadscrew nut to the right of the gantry.
The top bearing for the existing leadscrew is replaced by a new printed one. The ball bearing in this can be adjusted to line up with the screw and then locked in place.
A similar bearing block is printed to go on the right hand side.
The position of the leadscrew nut is also adjustable and is locked in place when everything has been aligned.
Print out the parts required.
The bracket is made to the dimensions shown below.
The 3 holes at the top are best marked from the printer itself as described later.
If you would like a full size copy of the plan send me an email.
With the gantry in the top position tighten the screws on the bracket printed parts to lock the nut in place.
Installation is complete.
If you have a digital caliper this can be used to set each side to the same height. As the travel will always be up when making a print make sure the gantry is moved in the up direction before taking measurements. It's easy to move the Z axis now, just pull on the belt.