Re: Popcorn RP

From: Marshall Burns (
Date: Tue Feb 01 2000 - 12:54:39 EET

>RP-ML readers are familiar with the additive and subtractive methods of
>RP: respectively, the mass of the part increases or decreases during the
>process. Logically there must be a third method where the mass stays the


    Yes, this is called "formative fabrication." The three fundamental
fabbing processes, additive, subtractive, and formative are explained and
illustrated on the "What is a Fabber" page at

    I would not agree with you that biological growth processes are in this
category. Biological growth is generally a special kind of additive process,
which we can call "accretive." This is discussed in the article at, where I describe
accretive fabbing as a process in which the product grows by adding material
to itself rather than by the action of any outside influence. In this kind
of situation, there is no fabber distinct from the object being fabbed. The
fabber is fabbing itself. This is how you and I, as well as oak trees and
house cats, grow up from embryos.

    I understand why you think of this as formative, because it seems that
the organism injests a stock of nutrients, which you then consider to have
become part of the organism and then to undergo reorganization in order to
join the solid mass of the body. One can certainly argue for this
perspective. But I prefer to think of the nutrients in the stomach and in
the bloodstream as separate from the consuming body until the molecules of
the nutrients have been incorporated into the structural cells of the body.
It's pretty much a semantic distinction.

    One day, technology will learn how to imitate these magical biological
processes. When that has happened, fabbing will have merged into nanotech
and the limitations of what we can make will have been stripped away

    Your discussion of popping of corn is another interesting matter. That
definitely is formative. I've never studied this process, but the way you
describe it sounds akin to a foaming process. You are right that the
challenge in utilizing something like this is in achieving control of the
geometrical changes that occur. I have no doubt that this will be achieved
with future technology.

    Thanks for your creative and inspired thoughts on fabbing processes.

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

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