Making the Tarantula the best it can be while spending the least amount on aftermarket parts. I re-framed it with all stock extrusions, I've color coded them to show where I moved them (see the 8th picture).
Some of the advantages: lighter X rail with 20mm more travel (or support wider X carriage), more stable and Wider Y rail, more stable Z rail with 20mm more travel.
Disadvantages: Y travel shrinks 20mm (will only affect 280mm beds)
UPDATE 1/18/2020: Make sure to check out the Remix of this design: https://www.thingiverse.com/thing:4082685
(It made sense to remix my own design at this point)
UPDATE: A new part has been added to support the Z rod with an additional bearing, this will help stop some flex in the shaft, and get smoother prints: "Bearing-Support-Center.stl"
The entire printer has been printed and tested (and modified and retested if needed) several have been built by users, one posted a build. It seems this project is for people who can print fairly well, and have their machine dialed in tolerance wise and layer adhesion wise.
Definitely run a tolerance test before starting this build, some good ones:
The extruder mod works great for feeding flexible material
Some parts need to be printed twice: ( print individually for smoother finish)
Z axle spacer (can be printed in vase mode)
Z drive pulley
Z idler pulley
Z idler pulley mount
Bed leveling knob (4)
Belt tensioning nut
Belt tensioner inner slider
angle-20mmx40mm (as many as you want to brace it)
The Z axis will be a little faster than stock, so change your z steps per mm from 1600 to 1382 (easier to change in firmware) and calibrate from there, mine is within 0.1mm over 200mm using 1382.
In cofiguration.h find this line:
#define Z_STEPS 1600 // Stock lead screw
Change the 1600 to 1382, then reload the firmware.
Making the Z axis faster was a design decision and you will still have plenty of z resolution.
The small_idler_pulley goes next to the X motor, the large pulley goes in the belt tensioner, they both use the bearings from the stock wheels, 2 each pressed in. The Y idler pulley is the stock pulley, only 1 instead of 2.
The Z adjustment knob is press fit onto an M5 hex cap head (from one of the stock wheel bolts) and should self tap into the hole.
The stock leadscrew is repurposed to be the Z axle.
You'll need about 2 meters of gt2 2mm x 6mm belt for the Z axis, might as well get 5M and replace the stock rubber bands.
M4 Set screws from the stock L brackets can be re used with M4 nuts in the top and bottom diagonal braces that use 8mm rods (threaded or solid, also 5/16 inch rods will work) they need to be 480mm +-5mm long.
Bolt or screw it to a base that is at least 515mm X 460mm
All the pulleys and gears use nut traps and set screws size M3.
The top two large bearings are 608zz (skate / fidget spinner type)
I recommend printing the worm gears at 0.1mm layer height, or less if your printer and material of choice can handle it. PETG is hard to print at 0.1mm so do the lowest you can.
I know some of my design choices are controversial, especially the 3d printed worm gears, but read the first sentence of this summary again, that was my objective all along. If this turns out to be less quality than I expect, then I will find a better way, but I think this design will surprise those who give it a try. Also it's not an all or nothing deal, you can put the stock X carriage on it if you want, or a dual lead screws like the Prusa i3.
Update: 12/26/2018 Z-slider-left has been replaced with Z-slider-left-2, it had a clearance problem with the X belt tensioner cage, if you already printed this you can cut off the piece that's in the way, see the new file.
Changed the X-carriage to X-carriage-2 added nut-traps for the fan duct mount and adjustable height for the fan duct (to tune it to various hot end lengths).
Update: 1/4/2019 Added a radial fan duct option for a 5015 fan "5015-Radial-Duct-optional"
Update: 1/9/2019 Added ribs to the Z sliders to prevent cracking under wheel pressure. Also adjusted some clearances for a better fit after printing. Holes in e3d fan duct were enlarged.
Update: 1/10/2019 Changed the top bearing holders to allow 8mm axle to be all the way through and not touch the plastic.
Update: 1/14/2019 Changed the X-belt-Large_Idler_Pulley for a better fit, strengthened X-Y-belt-tensioner-inner.
Update: 1/15/2019 For those using a stock X carriage: Added a small part to press the endstop switch on the X axis of a stock carriage (or compatible location) "X-endstop-switch-press-stock-location-OPTIONAL"
Helpful tip: use a hair dryer if the worm gear is slightly off (wobbly) while the gear is turning, and it straightens it out really well.