RepRec end-effector

Concept of an end-effector assembling an other end-effector by adding in one of the spanning jaws.

(wiki-TODO: TODO split up this page in smaller sub pages ...)
(wiki-TODO: add sketches old and new)

Less precisely toolheads or just tools.

The end-effectors essentially are
adapters between the toolhead-flange and the handled part

A RepRec must (per definition) have exchangable/switchable EndEffectors.
Reason for this hard constraint:
As a single end effector will not be sufficient for the broad variety of tasks needed
for pick and place of modular robotics and eventual self replication.

A RepRec systems end-effectors are a set of several different RepRec part manipulation devices that
can be coupled and decoupled to and from the tip of
the 6DOF positioning mechanism (the tip of the RepRec poser at the end of the kinematic chain)
which we will refer to with RepRec tool to poser flange or "stump" for short.

Zero or one end effectors can mount onto the ToolToPoserFlange
(mounted on the mobile end of the 2D parallel mechanics - whichever type is chosen)

Just like a RepRec part adapter a RepRec end effector mediates between a more standardized interface (the stump)
and a less standardized Interface (the manipulated parts).

All RepRec end-effectors should grip parts in a sufficiently SelfCentering way to yield reliable and predictable outcomes
When picking up the parts they are designed to handle. ReMec avoid inviting murphies law.
Both in case of standardized surfaces (e.g. ReChain base-crate) or special part shapes.

In general robotic end-effectors can use any means for picking things up not just gripping.
That includes magnets, air pressure, electrostatics, surface tension force, and whatever works.
With focus on self replication and scale transposed prototyping one will like to add further constraints.
Though one may want to still allow for RepRec vanishing vitamins.
Like to fake an analog of nanoscale vdW forces at the macroscale:
– vaccum suction cups and polished flat spots on the parts
– iron filled PLA and magnets (probably too heavy)

End-effector types & geometries

See RepRec end-effector geometry types

Basic ones:

• clutch style spiral driven (as found in lathes)
• counter screw style (steep multi-start threads for fast action)
• ReChain inspired force-divider clamping ((wiki-TODO: elaborate & add sketches))

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Specialized EndEffectors:
See page: RepRec specialized end-effectors

First prototype plans

Plans for a first EndEffector Prototype ...

• desired: fast acting
• much preferable: parallel acting
• probably not going for a clutch style (big & bulky, spiral, ...)

Number of RepRec end-effector types

The optimal number of RepRec end-effector types is an optimization problem.
Too few end-effectors and there's the aforementioned RepRec spacial overhead
which can render a RepRec design (and all its products!!) inefficient.
Too many EndEffectors ⇒ much more head swapping movements ⇒ slower operation.

If the product in assembly is big enough to make distances to the RepRec end-effectorRepRec stowage area increase
and there are so many RepRec end-effectors that they can't be carried around with the RepRec crawler but need a separate magazine unit for them.
then algorithmic complexity goes from O(n) to O(n^2). The street marking painter joke.

Storage of RepRec end-effectors

The ReChain clamp-board would provide "passive locking" of EndEffectors on other places than the RepRec head-flange.
(wiki-TODO: Add ideas on how to do end-effector storage.) This allows for transferring RepRec end-effectors away from the RepRec tool to poser flange.

That is: All the unused end-effectors can be kept on a ReChain clamp-board inside the RepRec working area for quick access.
If too many are present some can be kept on a clamp-board outside the working area
(in a cache extension area) that can be dragged in (by a special clamp-board dragging end-effector?)

All RepRec end-effectors are RepRec multi part assemblies and thus need to be assembled themselves.
Assembly of an end effector may involve the usage of the same type oof end effector that is being assembled.
And as the usage of RepRec assembly helper jigs that themselves may also be RepRec multi part assemblies needing pre-assembly.

The end-effector constituent parts need their own specialized RepRec stowage RepRec part magazines.
RepRec part magazines may come in vastly different sizes.
– Bigger ones be located outside the RepRec working area in a separate RepRec unit.
– Really small ones might even fit onto a RepRec clamp-board withing the RepRec working area.
Related: RepRec working zones

Keeping the RepRec end-effector DOFs in RepRec machine phase

Related to this section: Machine phase

When the RepRec end-effector is attached to the RepRec poser via the RepRec poser to tool interface
its internal DOFs are ultimately linked to and constraint by the driving system.

• (0) Locking at the RepRec tool to poser interface from the RepRec poser to tool interface side.
  

When an RepRec end-effector is transferred over to a RepRec clamp-board in RepRec stowage
then its internal DOFs need to remain constraint at all times.
(relying on friction self locking is not an option, it must be an energy barrier or positive locking)
Thus a different additional locking mechanism is needed.

The EndEffector could be locked from several places.

• (1) Locking at the RepRec tool to poser interface from the RepRec tool to poser interface side.
• (2) Locking at the RepRec tool to clamp-board interface from the RepRec tool to clamp-board interface side.
• (3) Locking at the RepRec tool to clamp-board interface from the RepRec clamp-board to tool interface on the RepRec clamp-board.

For convenience of macroscale operation one might want to be able to
take off the end-effector completely by human hands.
I.e. it is no longer attached to the machine but still preserves its position state reliably
That would motivate to put the locking mechanism inside the RepRec end-effector ⇒ (1) or (2) — eliminating (3)
Eventual active actuation of the locking mechanism may motivate to put the locking mechanism at (1).
Much more likely is simpler locking by spring though.
Nice, we have the winner (1) for now giving us a starting point for design.

More concrete design idea :
Assuming the interface is an axial hirth joint then
a partial radial slide on splined joint that is activated via an integrated spring
might lock the angular position into a known state.
Locking the RepRec end-effector to the RepRec poser to tool flange pushes the lock away in such a way
that at no point in time the rotative DOF in the RepRec end-effector loses its angular constraint.

Different tension for hull and bearings inside:
Additionally the moving elements in side the RepRec end-effector should (via that flange locking)
receive just the right tension to become properly self centered but not excessive in wear/friction.
The housing of the RepRec end-effector should be fastened
much more strongly via separate tensioning mechanisms.

Recursion: end-effectors gripping (assembled) end-effectors

(wiki-TODO: discuss)

Related

• Up: RepRec

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• RepRec specialized end-effectors
• RepRec general purpouse end-effectors being RepRec big part specialized end-effectors
• RepRec small part specialised end-effectors

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• RepRec starting points for RepRec system design
• RepRec fir-tree-clamp end-effector

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• RepRec tool RepRec toolhead RepRec end-effector

Page started (off wiki): 2027-03-23 Thursday.
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