I'm having issues with the wheels on my z-axis. It's looking like there's just too much slop with all the weight on 3060 extrusion. The 3060 is not wide enough either, unless a more constrained bearing is used. Right now I'm going to put some effort into a couple different linear bearing designs at the same cost of the 608 bearings. The 608 wheels are viable, but there's too much room for variability. I'm going to play around with some zinc plated BBs or airsoft pellets.
Added design files for a MKII bed support that hooks to the z-axis carriage. It prints in two halves, with 4 extensions for the sides. The major issue though is the lever arm force on the bed. It's looking like I'm going to have to add another extrusion for stabilizing, or I'm going to have to utilize the front two extrusions in a "X" formation. Here's a test video of it: http://youtu.be/v4dTq7hZGCA. You can see how bad the wobble can be unfortunately.
Added some new carriage designs, which eliminate the need for 5 mm screws. Gained some build volume. Still working on the build platform.
I have redesigned the z-axis to be cable driven as opposed to screw driven. My threaded rod had way too much wobble. I will leave screw option for those interested. I still have to upload a modified z-axis carriage, I just drilled holes in the old one for the spectra line. Right now the cable driven axis seems promising. Granted there's no weight from the bed, but the motor won't have a problem when powered. It's similar to the belt driven z-axis mod I made for the Ord Bot. I'm using the motor bracket from SWFL3D: http://www.thingiverse.com/thing:15180. Just have to add the build platform now and extruder.
I am ready to introduce a project of mine. I now call it the Core-T (I found the previous name taken by another robot). It utilizes CoreXY kinematics and is spectra line driven. The frame is 30 mm extrusion that can be bought at a lot of different sources. Uses printed wheels only and no linear bearings or rods! My main design goal was to avoid linear bearings as well as openbeam, v-slot, or makerslide. While those are nice, a complete wheel/bearing package is around $4 a piece. This overcomes that with inexpensive, widely available 608 bearings and inexpensive printed wheels. I'm using M8 socket cap screws to hold up the corexy pulleys. This makes them strong and free of flexing.
Right now the x and y axes are functional and pretty smooth. Here's a video of them running: http://youtu.be/1-CuOnObo3k. I originally modded the carriages for belts, but ran out of belts. That's why I switched to spectra. I will update the carriages for spectra line. I also need to shorten them up a little bit so I can maximize build volume. I'm going to be using Wild Bill's extruder for now, until I upgrade it to use a Makerbot type extruder.
Credit goes to LoialOtter for the initial design of the carriages: http://www.thingiverse.com/thing:20659. Also I have to give credit to AndyCart for his spectra pulleys from his design: http://www.thingiverse.com/thing:313048. Finally credit to capitaenz for the side guides for my spectra 608 pulleys: http://www.thingiverse.com/thing:31216
Current frame volume is 350mm x 350 mm x 350 mm. Build volume is about 175 mm x 250 mm x 330 mm.
20 x 608 Bearings
24 M8x20mm Flat Socket Screws
8 x M8x20mm Socket Head Cap Screws
22 x M6x12mm Socket Cap Head Screws
8 x M8 30 Series T slot nuts
22 x M6 30 series T slot nuts
16 x 350 mm x 30 mm T slot
1 x 3060 T slot x 500 mm
16 x M4 x 14mm Socket head cap screws
12 x M5 x 25 mm Socket head cap scres
1X extruder body
1X z-axis bushing
1Xz-axis motor bracket
1 X cex-bh2
2Xz lift front