Update 29-07-17 The full parts tray .stl did not contain the tensioner - fixed.
Update 01-Jul-17 - Revised motor mounts have been added. These have be updated for use with the linear rail conversion. I have removed the smooth rod clamp, and importantly made a 1.5mm shift of the motors towards the centre of the printer which improves the geometry of the belts from y-slides to motors. This geometry relies on using 608zz/f608zz bearings and 16t pulleys. The right mount has a 2.5mm hole to tap a screw for an endstop, if you wish to place on here. Please if you only read one thing and remember it - attach the motors BEFORE attaching the mounts to the printer or trying to get the bolts (please use plain hex headed m3 bolts, not cap headed allen key screws, or you will go mad).
Update 04-Feb-17 - I realised that the R y-slide has not got enough cut-away for the higher-plane belt not to rub, as I had mirrored it from the left side y-slide during the design. This is now corrected in the stl's above. Been working really well since installation.
Description: This is a kit to convert your SCALU printer to linear rail (MGN-12H) Hiwin or their Chinese equivalent getting rid of x and y smooth rods. The intention is for it to be as minimal to fit, and smartrap derived as possible.
You should be able to keep your rear pulley holders or preferably a version which is better supported such as these http://www.thingiverse.com/thing:1655402. As my printer has f608zz bearings the geometry wrt the belts needs to be considered if you also use these motor holders you get the correct geometry http://www.thingiverse.com/thing:1741525.
You will need 3 MGN-12H rails two for the y axis are 275mm and one for the x axis is either 340mm or 440mm depending on whether your machine is the standard 200x200 print bed or extended like mine in x to 300mm. It is definitely worth buying slightly longer rails than you need and then cutting them (they're hard so I used an angle-grinder).
Also at least 4 m3 half t nuts and m3 bolts, plus a selection of mainly short 6 and 8mm M3
I printed the parts in petg they are strong and the slight elasticity allows it to grip screw threads well. Print them at 90 or 100% infill there is a reason for this. The only fiddly bit in assembling it is the x rail. It's tricky as the hole spacing on the rails is not exactly the same for every manufacturer. So I have not included holes to mount the x rail, this is why you need high infill carriages.
The x carriage is my design with balanced belt tensioning, you'll need a long 60mm-ish m4 bolt to connect the moving belt clip. More details can be seen here in the original listing. http://www.thingiverse.com/thing:1582049
So attach the y axis rails to the frame with the t nuts. Then attach the y slides. Now you'll need to decide where to cut your rail to allow for reasonable screw positioning into the underside of the y slide. Now cut the rail, then mark the holes and drill the y slides to 2.5mm. You can then attach the rail to the y slides with m3 bolts. I wasn't totally convinced so I also bonded it with epoxy.
Press or heat-press 4 m3 nuts into the adaptor plate which is screwed to the x linear rail carriage, use short screws to attach it to the carriage and to the printed x carriage. Then just a case of reattaching your belts, hot end etc...
Definitely less play at the nozzle, I expect when I try grid levelling there will not be the characteristic sag in the middle due to the x rods bending.
I accept that there are probably better designs for a corexy gantry for this printer using linear rails, but if you want to keep your machine as close to the SmartRapCore, just with improved function this might be the way to do it.