Re: RP-able robots

From: Marshall Burns (
Date: Mon Feb 07 2000 - 21:34:31 EET


    Thank you once again for contributing still more interesting ideas to
the RP-ML.

    On this subject of fabbed (or RP'd) robots, at the 1996 Austin
conference Ken Hayworth of Ennex Corporation showed a robot finger fabbed in
the then-new prototype Offset fabber. He took advantage of the fabber's
ability to stop in mid-process to allow him to lay control cables into
designed-in channels, which were then covered over and closed by continuing
the fabbing process over top of them. The paper includes a fairly detailed
description of how the finger was made, along with a picture of the CAD
design and a photo of the actual finger. At the conference Ken showed a
video of the finger operating. The paper from the conference proceedings can
also be found at (look in the
section, "Applications" towards the end of the paper).

    We absolutely agree with you that fabbers will allow the creation of
better robots that cannot be made any other way. Ken's robot finger was our
first attempt at demonstrating that fact.

Best regards,
Marshall Burns
President, Ennex Corporation
Los Angeles, USA, (310) 397-1314

-----Original Message-----
From: Jim Mallos <>
To: <>
Date: Monday, February 07, 2000 8:54 AM
Subject: RP-able robots

>Will we ever see a robot emerging full-formed from a stereolithography
>vat? This is a distant prospect if we imagine making the same robots as
>are now made.
>Suppose instead we just look for technologies that are easy to
>stereolithograph and see if we can make a robot from them? Our quest
>then becomes a matter of creative robot design and some new applications
>of today's stereolithography.
>Here are some easy-to-stereolithograph technologies that can form a
>Mark Tilden at the Los Alamos National Laboratory has shown that
>interesting robotic behavior can be attained with very simple control
>systems (for example a walking robot with just 12 transistors.) His
>approach uses force feedback to create a chaotic system comprising both
>the robot and its environment, see
> .
>Fluidic. The simple controls needed by Tilden robots can be provided by
>no-moving-part air fluidics. This is a developed technology, we just
>need to learn how to make the components by stereolithography.
>Pneumatic via flexible passageways.
>Biomorphic, probably walking. Wheels and wheel-like elements such as
>gears are banished from the design---they need too much precision.
>Flex joints. Journal bearings are banished for the same reason as
>Flexible pneumatic actuators. Figure 1 of U.S. patent 3981528,
> , shows a simple
>shape that combines flex joint and actuator in one.
>Flexible pneumatic actuators---they can be used passively as force and
>contact sensors.
>Any semi-flexible material with a wide temperature range. A
>semi-flexible material can be programmed to be fully rigid (with ribs)
>or fully flexible (with convolutions.) We don't need anything else---the
>air in the pneumatics does the hard part.
>Thermal storage, either hot or cryogenic. (Storage temperatures limited
>by the tolerance of the construction material.)
>Thermodynamic. Perhaps the easiest conversion method is simply to fill
>the robot's little belly with dry ice. Capturing the subliming carbon
>dioxide at a modest pressure can supply the fluidics and actuators with
>a steady stream pressurized gas.
>A more elegant technique for the long term is the Stirling amplifier. A
>Stirling amplifier is simply an air-filled chamber that has a hot wall
>on one side and a cold wall on the other. A porous, insulating divider
>called the regenerator separates the two sides of the chamber. If the
>divider is pushed all the way to the cold side, most of the air will be
>hot, and the air pressure in the chamber will be increased as a result.
>Similarly, the air pressure decreases when the divider is pushed back
>over to the hot side. Given a big enough temperature difference between
>the walls, the air pressure changes can do more work than it takes to
>move the divider. If the divider is itself actuated by pressure, this
>forms a signal amplifier that can perform control functions, or amplify
>a pneumatic output signal to drive an actuator. (Notice that this system
>works with reversing AC flows instead of a DC stream of gas.) The
>Stirling amplifier can be energy efficient because most of the
>tranferred heat comes from the regenerator, not the walls which are
>maintained at temperature using the thermal storage.
>How long do you think it would take to engineer such a robot?
>Jim Mallos
>For more information about the rp-ml, see

For more information about the rp-ml, see

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