Re: rp definition

From: Ronald Jones (
Date: Sat Feb 03 2001 - 21:22:17 EET


I have been reading the ongoing dialog on this subject and was wondering when someone would get it right. I concur with your definition and with your permission, I would like to use your definition and terms in our materials and in presentations.

Ron Jones
Shared Replicators
  ----- Original Message -----
  From: Nuno Reis
  To: Brock Hinzmann ; Elaine Hunt ; Jeff Katz ; RP-ML ; Terry T. Wohlers
  Sent: Saturday, February 03, 2001 7:51 AM
  Subject: RE: rp definition

  We may need more than one definition to include every single idiosyncrasy. Here is my contribution:
  1. I agree that a broad RP definition should include CNC machining but the words "arbitrary shape" cannot figure in any serious description. Semantic (adverbial) consideration aside, Elaine's definition is broad enough to include all sub-classes , i.e., subtractive, additive, formative, self-assembly ...
  2. Amongst the additive manufacturing community the terminology Solid Freeform Fabrication has gained popularity in recent years. It avoids the term "rapid", excludes machining, and could be defined along the lines of: "a set of techniques capable to grow a physical object directly from computer codes by the addition of material layer-by-layer, line-by-line or voxel-by-voxel, and free from confining surfaces other than a base".
  3. On the "rapid-being-quick-or-not" controversy I personally find useful introducing another dimension to the discussion which is part complexity (in terms of information content [bits]): SFF machines are indeed quicker above a certain threshold. Moreover they can make things which have traditionally been very difficult and in same cases impossible to obtain.

  The difficulty lies on defining boundaries such as the above threshold: Maybe we need to update the information of manufacturing processes selection databases! I have exercised a bit on this and welcome an open discussion with anyone interested.
  Nuno Reis

    -----Original Message-----
    From: []On Behalf Of Brock Hinzmann
    Sent: Saturday, February 03, 2001 12:31 AM
    To: Elaine Hunt; Jeff Katz; RP-ML; Terry T. Wohlers
    Subject: RE: rp definition

    The purpose of defining something will alter the definition you choose to use.

    From a practical point of view, Jeff's broader definition is good. Rapid should be that which is relatively more rapid than the alternatives, for the given application. Prototyping should create a prototype that fits the definition of a prototype for the end user, which much of what we consider on the RP-ML to be prototyping is not.

    From a market research point of view, Terry has to narrow the definition down to something he can get his arms around. Furthermore, from a consulting point of view, he must be able to point out what is new and what is changing and what his clients should do about it. Which isn't to say that nothing new is happening in CNC machining, but most people know what they can do with it (sic). What is different is the appearance of new methods for realizing arbitrary physical objects directly from virtual objects (CAD).

    For many years, people in this forum have argued that neither rapid nor prototyping are sufficient to describe the new machines (to Sheba's point), but they agreed on a term for the sake of continuing discussion and sharing of information. Perhaps that was a mistake. I am beginning to hear complaints that corporate managers use the technology to shorten the time for producing a model/prototype, but have failed to use it optimize the design of their products by realizing, in the same amount of time, a larger number of variations on the objects envisioned by creative people working in CAD. They can see and measure whether they are getting more rapid prototyping than they were previously, but they are not necessarily getting better products, however you define >>better<<.

    Perhaps the name and definition are partly to blame.

    Brock Hinzmann
    Technology Navigator
    SRI Consulting Business Intelligence

    Jeff Katz wrote:
>What's wrong with using CNC machining to do "Rapid Prototyping?" In some
>cases, depending on material and finish level, CNC machining is actually
>more "rapid" then RP. If the question is how do you rapidly produce parts
>directly from 3D CAD data, CNC should logically be included in the
>classification, otherwise it's an arbitrary distinction.
>We lump CNC and EDM in with all the others in our Rapid Manufacturing
>marketplace. If you really want to distinguish SLA, SLS, FDM, etc. from
>CNC, you really need to change the name from Rapid Prototyping to Additive
>Prototyping or even Fabbing. Right, Marshall?
>Jeff Katz
>773.477.7374 x203
>Fast, Free, Secure
>-----Original Message-----
>Message text written by Elaine Hunt
>>The Rapid Prototyping Report in 1992 defined RP as
>The Fabrication of a physical, three dimensional part of arbitrary shape
>directly from a numerical description (typically a CAD model) by a quick,
>highly automated and totally flexible process.
>Does this definition define what you do with rapid prototyping? Should it
>be expanded and if so how would you change it?<
>I've been using the following to briefly define/describe RP:
>Rapid prototyping (RP) is a relatively new class of technology used for
>building physical models and prototype parts from 3D computer-aided design
>(CAD) data. Unlike CNC machines tools, which are subtractive in nature, RP
>systems join together liquid, powder and sheet materials to form complex
>parts. Layer by layer, RP machines fabricate plastic, wood, ceramic, and
>metal objects based on thin horizontal cross sections taken from a computer

>Terry Wohlers
>Wohlers Associates, Inc.
>OakRidge Business Park
>1511 River Oak Drive
>Fort Collins, Colorado 80525 USA
>Fax 970-225-2027

For more information about the rp-ml, see

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