Error: 3D Milling vs. 3D printing

From: michael rees (
Date: Fri Sep 08 2000 - 10:15:45 EEST

re: Your August 30 article "A Revolution in Robotic Evolution"
web sites referenced:

Dear Mr Boyle,

Thank you for your interesting article "A Revolution in Robotic

In that article on you state:

"When the selection was winnowed down to a handful of the fittest
survivors, the computer carved them from a block of plastic, using a 3-D

     The 3-D printer, also known as a plotter or milling machine, could
create the complete robot, joints and all, within its 8-by-8-by-12-inch
parameters. "

You also give a link to a page which discusses 3d milling machines.

This is incorrect. The machines that built these robots are called
rapid prototypers, 3d printers, fabbers or most accurately automated
additve layer construction devices. They build things up layer by layer
instead of carving them from a block of plastic.

This is an important detail. Milling machines work by winnowing down a
block of material. They are subtractive. Rapid prototypers or 3d
printers work by building up the part layer by layer. There are several
different strategies that companies have used to accomplish this, but
they generally employ this additive strategy. The ability to construct
things additively gives a host of constructive possibilites that are not
available with milling machines. The two most notable advantages are the
ability to model any geometry no matter its convolution or complexity
(without user intervention) and the ability to construct voids within
forms (and in some cases trapped volumes).

If you visit the Golem project website
(, you will see that these
parts couldn't be made as easily with milling machines and are only
possible in additive manufacturing techniques. (please see the image
I've enclosed which I got from the golem web site). To be fair, one
could mill some of these shapes automatically. But they would require
much human intervention to 1. program the tool paths and 2. create the
complicated fixtures needed to hold the work firmly in place. Rapid
prototyping allows the direct construction of the part without human
intervention after the original software parameters are entered.

If you would like to learn more about these exceptional machines or do
an article on them please visit the following page for details: Or post a querry on the
Rapid Prototyping Mailing List. (

If you would like to see sculptures made with these machines please
visit my website:




For more information about the rp-ml, see

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