The first thing that I noticed while working to get my Solidoodle Workbench 3D printer operational is that the placement of the stock filament guides position the filament very close to the Z-axis rods. While printing, the filament was rubbing against the greasy rods. I searched Thingiverse and came across one entry for the Workbench series printers, a filament guide for the Workbench Apprentice, http://www.thingiverse.com/thing:627986, a good idea, but it wouldn't fit on the Workbench due to differences in the case. This is what I came up with. You have two choices, a snap-on filament guide, which slips onto the case between the rods and a bolt-on filament guide, which bolts on using the existing four bolts that support the top of the Z-axis carriage. Be careful to support the bed when removing these bolts, as the carriage will move forward. The bolt holes in the printed piece may need to be enlarged slightly. Both STL files have already been run through Netfabb to correct any problems.

I both of printed mine up with 100% infill, but the snap-on guide is non-structural, so lower infill would most certainly do. The bolt-on guide needs something solid for the Z-axis bolts to snug down on, so I would suggest not going too low on the infill with that one. I printed both in PLA, because that's my favorite at the moment, but ABS would work just as well. No support was needed.