Akimbo - A redesign of the Mendel Frame
by raldrich, published
Akimbo is a redesigned Mendel frame, designed with increased build area, dual extrusion, easier assembly and increased rigidity in mind.
The top of the frame is tilted outward, to increase the frame's rigidity, and to keep carriage and extruder parts from banging into the frame at the top of the build area.
The space between the top horizontal bars is increased to 100mm, to allow clearance for placing the motors on top, and to keep the belt on a horizontal X carriage from rubbing against the frame at the top of the build area.
The frame is designed to be squared entirely with simple jigs, and uses parts that enforce frame geometry whenever possible.
All axis use a hybrid design for their movement - LM8UU (or equivalent) on one smooth rod, to provide maximum constraint, and a pair of 683 (3mm x 7mm x 3mm) roller bearings on the other smooth rod, to prevent binding.
The design supports 2 separate tool carriages, which allows 2 extruders with different hot-end lengths to be used on the same printer, and allows one extruder to be parked offsides while the other is in use.
Sources are available at https://github.com/Lodran/Akimbo
Threaded and Smooth rod lengths are compatible with either Sells or Prusa (i1 or i2) designs, except for the Z axis screws, which are M5 threaded rod, 260mm in length.
Jig lengths are identical to Sells design, with a new jig added:
Â Â Â Â J1 - 290mm - length of triangle sides, measured between the inner sides of the vertex brackets.
Â Â Â Â J2 - 234mm - length of bottom horizontal rods, measured between the inner sides of the vertex brackets.
Â Â Â Â J2b - 304mm - length of top horizontal rods, measured between the inner sides of the motor mounts.
Version 0.2 put the parts on a diet, fixed a couple of bugs, and added Z axis smooth rod clamps.
Version 0.3 tweaks the parts for easier printing, strengthens the Z linear rod clamps, and makes measuring distances along the x axis a bit easier.
Version 0.4 adds X axis, Extruders, Carriages, and some of the Y axis parts.
Version 0.5 finishes the Y axis.
Note: The endstops I've currently designed for are non-standard - see http://www.thingiverse.com/derivative:38617