RepRec orienter

This page is part of the RepRec project. Short for Replicating Recomposer Systems. For an index of all pages of this project, see the category page RepRec.

(wiki-TODO: Scan and add sketches in here.)

It provides the 3 rotative DOFs.
The "orienter" (also called "wrist") is the part in the motion stage / kinematic chain
that is tasked with imparting the orientation (3 rotative degrees of freedom)
on everything further downstream the kinematic chain. <nr>

Downstream the kinematic chain:

• RepRec poser to tool interface (the orientier is the downstream patt of the poser thus poser)
• RepRec tool to poser interface
• RepRec end-effector
• end-effector to picked part interface

Upstream the kinematic chain:

• RepRec positioner
• The motion system of the RepRec cawler (possibly indirected to a dedicated RepRec unit carrier unit)

It is desirable to have the orienter/wrist
being agnostic to the choice of the RepRec positioner

Crossing rotation axes

If the three rotation axes are not crossing through a single common point then the delineation to the RepRec positioner
is not as good and the RepRec positioner needs to compensate for motions caused by the rotations with some math.
The centers of the pick-n-placed of different sizes will be off even if there is a common rotation center any way
so it's nit that severe for the pick-n-place application case.

Motion threading as especially hard problem for the section through the orienter/wrist

Since one likely wants at least one actuated DOF
for the RepRec end-effector there is a need for
– RepRec through joint motion threading
– (= rotative RepRec action transmission)
which makes the already hard problem even harder.

Motors on the end-effectors are a non option for RepRec systems.

• macroscale: bad motor mass, nanoscale: crippling motor volume
• macroscale: messy cable wiring; nanoscale: bending nanowires changes electrical properties & one gets ballistic electron transport & chemical is physical just like mechanical is

Related: Through joint mechanical motion threading

Inspiring sources

⭐ Goniometer stages but stacked.
(Side-note: These are positioning stages not measurement devices despite the name.)
These seem especially suitable as
– they provide very high stiffness and
– they allow for high angles with accordingly adapted designs (unlike e.g. very stiff Steward platforms)
– slightly easier mechanics in gearing (unlike the conical gear differential wrist below)
Related: Assembly line orienting stage

One axis goniometer stage (Zaber Technologies Inc.)

⭐ 90° differential gearbox inspired robot wrist like in this robot:
CC-BY-3.0 paper: https://iopscience.iop.org/article/10.1088/1757-899X/294/1/012079/pdf

conical gear differential wrist mechanism

⭐ Fanuc robot wrist:
2021-04-19 –– 0.5mm pencil lead insertion M-1iA/0.5A (6 axes)
https://www.youtube.com/watch?v=QjVjQOvG33E
Due to the RepRec no small parts design restriction the design would likely need to be modified quite a bit …
Basically RepRec axle onion where at every turn the outermost tubular axle ends in driving all of the downstream kinematics.

Fanuc deltabot robot wrist

The last points to a class of RepRec nested axles based RepRec orienters

Related

• Up: RepRec & RepRec pick-and-place robots

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• RepRec nested axles
• RepRec inspiration sources
• Up: RepRec system topology

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Most important pages:

• RepRec pick-and-place robots (GemGum)
• RepRec pick-and-place robots (RepRap)

Page started (off wiki): 2018-10-28 Thursday.

External links

• https://commons.wikimedia.org/wiki/File:Positioning_goniometer_stage.jpg
• https://commons.wikimedia.org/wiki/File:Tracta_Constant_Velocity_Joint.jpg