Akimbo - A redesign of the Mendel Frame
Description
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.
Instructions
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:
J1 - 290mm - length of triangle sides, measured between the inner sides of the vertex brackets.
J2 - 234mm - length of bottom horizontal rods, measured between the inner sides of the vertex brackets.
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 thingiverse.com/derivative:38617
You must be logged in to post a comment.
For me, the main problem of the Prusa is the location of the Z motors; moving them at the bottom would be a major improvement (no more problem with sliding coupling, less shaking because of a lower gravity center...)
My first parallelogram frame actually did just that, without widening the top. It had a few disadvantages.
1) With a standard Prusa 1 or 2 X axis, build height was not improved, because the belts still run outside the frame, and still interfere at the top of the build height.
2) Having the Z screws be under compression instead of under tension may be a disadvantage when using more flexible (i.e. M5) Z
screws.
3) Moving the motors to the bottom requires the use of longer Z screws, which reduces the number of Prusa frame parts that can be reused.
Are you sure the parallelogram frame does increase the stiffness? Intuitively, it seems like that would just add a rotational component to the resonance induced by the x axis vibrations. Could an engineer chime in and give their opinion?
Sounds like a good idea.
Now, how to get this commited into the Reprap trunk to become part of the next generation?
License
More from raldrich
More from 3D Printers
iam missing some screw holes for the Z motor mount, only 2 of them are useable :D
time to drill
Yeah - I found that after several hours of printing - for now, I'm simply going to bolt motor down with two screws.
by the way, there's a worse bug in the bottom z mount - not enough space for all of the nuts and bolts.
hopefully I'll manage an update for it tonight - I've got the geometry fixed, but I'm not happy with how much plastic it's using.