FoldaRapX

FoldaRapX 0.1

Release status: in progress

Description	another folding reprap
License	GPL
Author	User:Emmanuel
Contributors
Based-on
Categories	RepRap machines; Traveling RepRap; Foldable RepRap;
CAD Models	Github
External Link	Flickr Photostream

Principle

Back to the concept of a foldable RepRap using a scissor-like mechanism for the Z axis.

The main advantage is that this time the folding mechanism is part of the movement, and don't require any preparation for the machine to function... it will unfold as much as the part to print is tall. And makes for an even more lazy foldable RepRap : open the case, plug, print.

Build notes

tensioning the z-belt should be done in the upward direction, in order to tension against gravity

To-Do

Version 0.2

change the aluminium flight case (not cheap) for a regular wooden flight case (easier to use and customize)
move the linear rail 5mm closer to the pivot, in order for the end rail (printed part) to play its role of mechanical stop
if the aluminium plate were made with a CNC instead of a laser-cutter, we could include the tapping of the holes (would save lot of time)
24v

Version 0.1

at the lowest Z height, the complete upper plate weight enough to move the z-motor (if motor off) : caution when using M84, or use a higher gearbox ratio (14:1 is good), or a worm drive.
Need help to implement a non-linear Z-axis in the firmware, see this post in the Duet forum
add LED lights

R&D

Determining the Z height at wich to print was tricky, a bit of play in the z-belt system allow something like 0.5mm of deviation, but here is a first test print. Without an adapted firmware or gcode post-processor to compensate for the non-linear z-axis, the 50mm test cube is 50x50x80mm (we can clearly see the gradually smaller progression in successive Z moves). Well, that was just to show it could be used and that I went as far as I could by myself :)
32 teeth pulley being bigger, it leave me not enough belt length to try, but the 14:1 motor is strong enough ! This time I can start from under the bed, as it is supposed to be parked here. But there is a little flex in the bottom plate (3mm alu) that still allow the belt to skip around the pulley sometimes (bad noise to hear).
This was the lowest height from wich the motor could start, 20mm away from the target... I bought a bigger pulley and the same motor but with a 14:1 reduction (also in case it is not enough, a worm driven one).
Almost one year after... [blade-fuse changed], Duet2 works, and it moves ! But with the full weight multiplied by the scissors at the lowest height, the belt skip some tooth on the classic 18 teeth pulley and/or the motor does not have enough torque (5:1 reduction). I could use a bigger pulley to have more teeth in contact or a greater reduction for the motor.
once open everything is ready to be used :)
few bolts were added to hold the components in the lid (Z-cable-chain, Duet, spool-holder, will add the power supply too)
configuring the Duet as far as possible, like a CoreXY machine, but will need to create a firmware for the scissor Z mechanic
implementing the extruder, cable-chains, sorting the wires, adding parts printed in flexible filament to position the lower plate in the case while also dampening the chocks when moving the case
removing the internal padding of the case
the wheels are taking more place inside the case than what I thought : I am changing the orientation and position of the electronic (the Duet will be in the lid instead of the base), it will also makes for a better path for the wires/cable-chains and better use the space.
in the aluminium case :)
once assembled there is more rigidity than what I feared to have, thanks to alternating the orientation of the scissors (good intuition here) the material works mostly in its horizontal plane, so even plastics seems fine (except that a scissor broke for pushing to far) - [video of a test move]
scissor movement, smooth and without play along the linear movement (thanks to press-fitting everything), but some angular play in one of the bearing (balls/cage).
press-fitting the 695zz bearings (5x13x4mm) and D5L10 spacers with a vise works (the spacer outer diameter is 5.1mm in fact)... but using D4L10 shoulder screws and 604zz bearings (4x12x4mm) instead will be easier, I will keep that in mind for the next iteration.
Fast forward 2019... 360x360mm footprint, almost the same as the FoldaRap with a roll of filament. 4mm aluminium frame, H-bot, linear rails, e3D-titan, geared-nema17 for the Z-belt. And should have a 150x150x150mm build area.
was imagined during the initial concept of the "FoldaRap2" mid-2012, then named "Mondrian" when it was not pursued at the time