[Robotgroup] Ferrocement Plotters (Was Menage a Tux)

[Bruce Waters]

brooks,
http://createthefuturecontest.com/pages/view/entriesdetail.html?entryID=977
has some additional info on my intentions to create a crew of ferrocement
plotters as a Rapid Manufacturing (RM like rapid prototyping but full scale)
technique for architectural objects such as single family dwellings and
other
low profile structures.

A crew of plotter vehicles of different sizes and resolution capabilities
would
lay down layer upon layer of dry mortar mix (no aggregate) where there
should
be structure and dry sand where there will eventually be voids.   These
mobile
bots will travel directly on the surface of the previously plotted layers on
low
disruption (perhaps large rubber tires with no tread)  plotting subsequent
layers.
Every layer plotted will completely tile the plane (no voids remaining.)
Automatic wire feed-and-cut bots will insert short, fine wires into the dry
mortar mix to create the steel mesh within the ferrocement.   Each inserted
wire segment would be injected into previously plotted layers with no part
sticking out of those layers.   There is no need to interconnect these wire
segments.

After all patterened layers are completed, additional sand will be piled-on
to the mound to compact the dry materials.   Soaker hoses or fine misters
would wet down the entire mound to cure the ferrocement within the mound
of sand.   The mound will be kept wet for a month or two to allow curing
of the cement.   Front end loader bots, air blower bots, and power washer
bots will remove the sand at the end of the curing period.

This technique does not involve gantries so there is not a fixed limit to
the area covered by the structure.   The vertical dimension is limited by
the huge volume of dry sand required for structures of significant height
since the mound should taper to the ground surface unless a wall is used
to restrain the dry materal from collapsing on the periphery.   Tall objects
might be manufactured horizontally and raised after cured.

One type of plotter bot could fit in a cube four feet on a side.   It might
have  a beer keg sized cement mixer style dry material feed drum with
a small internal spiral to feed material in a controlled manner down chutes
to the plotting area.  A vertically mounted laser rangefinder might measure
the material deposited.   Two laser rangefinders pointing forward from
either side of the vehicle and another pointing to one side could easily
keep the vehicle travelling in a straight line indexed precisely to each
subsequent stripe of material deposited.    Two sides of the work area
would have a reflector surface for precise distance measurement with
the laser rangefinders.

All plotterbots would have wifi communication with the command
and control server.   Some bots might be as large as a real cement
mixer for depositing huge amounts of plain dry sand in large areas
which have very coarse resolution.  Some bots might carry expensive
laser rangefinder(s) and be capable of very high resolution plotting.
Other bots might have simple, cheap sensors to track breadcrumbs
(figurative) left by the more capable bots.   One extreme might be
a line follower bot with wheel encoders laying down the next stripe
of material just behind a high dollar sensor bot.

One mental model of a crew in action might be a lidar bot followed
by a number of same sized line-follower bots each laying down the
next stripe.  The bots would travel in a moving oval over the work
site depositing material one after another until a layer is complete.
More practical crews might have a spectrum of sizes, resolutions,
sensor capabilities with more complicated paths based on the
variation of the data across the active area.   Other models might
have the same appearance as diagonal lines of agricultural harvest
machines in action.

The active area must be protected from moisture and wind during
plotting so a fan-inflated plastic film tent could be used to provide
this protection.   These techniques should radically reduce the labor
required to build a residence and greatly increase the flexibility of
design by going directly from a CAD description of the structure
to the actual item.   Pick and place robots should also be employed
to embed items of small vertical extent (horizontal pipes, wires,
anchor bolts, ....) as construction proceeds.

Bruce Waters