I'm officially abandoning the whole nylon slider idea. It might work if you used POM, but nylon is not suitable, and I'm not willing to sink any more time into it. I've switched back to wheels.
I have improved the sliders. There are now Y and Z sliders and a sliding X direct drive carriage based on croadfeldt's work (modified source code is available on github). For the extruder use a bowden adapter of your choice (I used the C-Bot bowden adapter).
Use Taulman 645 or Bridge for the sliders, and make sure you get as little warping as possible. I have had great results using Printbite at 95C for the first layer and 105C for all other layers.
I'm currently running the printer completely without wheels with no discernible loss of quality. Pictures coming soon once I clean it all up.
This is a collection of modifications for Carl Feniak's C-Bot. Many of the parts are redesigned for increased rigidity, reduced cost, and reduced build time requirements.
The latest code is always available on github (the code pretty ugly at the moment.. This project has been my learning project for OpenSCAD).
The corner brackets, stepper mounts, and perpendicular brackets are all tested and provide an extremely rigid frame for the printer. I have done full prints at 150mm/s with a heavy direct drive stepper on the carriage. Attempts to go higher fail only because my steppers are not up to the task -- the frame remains rock solid.
Currently I would recommend avoiding the sliders unless you are feeling adventurous, as I have encountered a few issues trying to get them to function adequately.
A secondary benefit is that the tolerances are so tight that being able to assemble the printer virtually guarantees that it is square -- assuming the printer you used to print the brackets is also square. This allows you to get to an assembled and squared frame in a matter of hours.
Make 100% sure your printer is square and dimensionally accurate in X, Y, and Z directions.
I recommend having a piece of 2040 V-Slot on hand before printing everything. You'll want to test fit each piece.
The bottom corners only need minimal supports, and I have printed them entirely without supports.. I have found setting the support angle at 60 degrees does the best job for those pieces.
Start with the bottom extrusions. There are two different bottom brackets, one of each for the front and back. You want to form a "U" shape with the front, right, and left bottom extrusions and the 2 front brackets. Then place the rear 2 brackets on the rear bottom extrusion, and slide them together with the "U" shape formed by the other extrusions. Now place the vertical extrusions in each of the 4 brackets and push everything together. Don't use any screws at this point -- everything should hold together without it.
Now take the stepper brackets and place the top front extrusion between them. Place the brackets and front bar on the front vertical extrusions. Separately assemble the rear top corners, the rear top extrusion, and the top side extrusions into another "U" shape. Push the U shape into the stepper bracket openings. If you are using the large T nuts make sure to insert as many as you need before fitting everything together.
Take the Z gantry and bed support extrusions and assemble them into a U shape before placing the Z wheel mounts on the sides.
Assemble everything else as normal per the C-Bot instructions. Measure each side and ensure that it is exactly the same length at the top and bottom as its opposite, and measure the top diagonally and ensure that the left-bottom-to-right-top distance is the same as the left-top-to-right-bottom. Make adjustments if necessary (if your parts are straight and your cuts are accurate it shouldn't need much adjustment).
Now only once everything is square should you start putting in screws. Put in just enough to hold it together at first, starting with the top pieces. Double check all 4 sides and the diagonals are straight before moving to the bottom. Check all the dimensions again after assembling the frame with minimal screws. Once you are satisfied that everything is square, you can add the rest of the screws and tighten everything down.