See final update. Do not make this yet. It has a problem.
This is a total remix of the Mostly Printed CNC to use bushing. It also simplifies many of the parts to make it an easier assembly. This is a work in progress and can and will change.
The original designer (Allted) did a awesome job on this and my design should in no way take anything away from his great work. It is merely an alternative for those that want to try it.
To build the unit:
Print 4 corner's (stand upright with supports)
Print 4 roller1's (lay on motor mount. No support)
Print 1 resizedcnccenterforbushings88 (stand upright with supports)
Print 14 endcap's (no support)
Print 1 zaxismotormount231 (no support)
Print 4 feet
Print 1 nutlock
The bars are held in place by drilling holes into to the bars and using a 3mm tap and then screw together will 3mm screws.
This unit works with bunting bearing or bushing if you will. They are 15/16" x 1 1/2" long.
You will need at least six of these. You can find them here: https://www.zoro.com/bunting-bearings-sleeve-bearing-id-1516-l-1-12-pk3-cb151812g3/i/G3982474/
This design also uses nema 23's.
You are also going to need a nema 23 to 5/16" screw coupler. My nema 23 shaft size is 8mm so I am using an 8mm to 8mm coupler and it works well.
You can find it here: http://www.ebay.com/itm/5-16-inch-to-8mm-Set-Screw-Shaft-Coupler-By-Actobotics-Part-625194-/281957727216?hash=item41a5fd7bf0:g:hZQAAOSwT6pVsV4I
Other than these special items all the other hardware for this unit is basically the same as the original design by Allted. You will still need 8 608zz bearings. 8 5/16" screws 2" inches long and 8 5/16 Fender Washers and a bunch of 3mm screws which you can find here: http://www.amazon.com/gp/product/B005DZZC4G?psc=1&redirect=true&ref_=oh_aui_detailpage_o01_s00
Update - 3/20/2016
I am currently in the process of building this thing and when I find things that could make it easier I am modifying them as I go. I will also provide any helpful advice as well.
Update - Added a channel guide for better wire management to the roller unit. No you can hide all the wires coming out of the bars.
Update 3/21/2016 - Added feet to unit and also added an alternative center that has bushing for the tool head at the request of a couple of people. These bushings are not necessary but if you want it all to have bushings here you go.
Just to be clear the file called -
resizedcnccenterforbushings88.STL is without the tool head bushings and the file called
cnccenterforbushingswithtoolbushings.STL is with the bushings. Either one should work fine.
Update 03/22/2016 - Added a lock cap to the nut assemble to prevent nut from sliding up.
Update - I have now tested the x and y axis bushing and they work great. Very smooth.
Update 4/1/2016 - I have now tested the z axis and I am sorry to say it is not going to work as I had hoped. It is way to loose. I need to find some bushing that will fit a little snugger. These are 15/16" and they are very close but they do have a bit of play. I am putting the project on hold to explore another option. Do not make this yet. It does not work. I will post again when I devised a solution to the problem.