Re: Engine Turning by CAD/CAM methods

Message: 11
Date: Mon, 31 Oct 2005 10:14:25 -0700
From: "Tim Goldstein" <timg@...>
Subject: RE: Engine Turning by CAD/CAM methods

> I think it could be handled as a hole drilling program, but
> use the tool instead of a drill.

---Snip---


Bill,

My guess is that the person posting this question was not thinking about
what we refer to as engine turning (like the design on the cowl of the
Spirit of St Louis), but what I would refer to as ornamental turning.

[To me, it sounds like he's talking about "jeweling", which produces a
fish-scale effect with a pattern of overlapping disc-shaped marks. These
patterns are typically created by charging the end of a dowel with grit and
running it in a drill press, although a CNC machine would simplify the
process greatly - a hole-drilling routine would probably work well for this.
Engine turning is different, although there seems to be some widespread
confusion on the nomenclature. It requires more complicated machinery, like
the Holtzapffel lathes or rose engines you refer to below. Of course, CNC
makes this sort of thing much easier; instead of using complicated
mechanical gearing, we can use our CAD and CAM programming.]


The
designs are far more complex and were produced on rose turning machines and
Holtzapffel lathes. Here is a link to a site with some good photos of the
types of designs.
http://home.vicnet.net.au/~pwguild/o-rosego.htm

Interesting approach, hi-res images and use with DeskArt:
http://members.aol.com/tukuvectors/

I have pondered how to program these types of designs and come up short. The
math is over my head. Would love to see a discussion on how to use a 3 or 4
axis CNC machine to do this type of ornamental turning.

Tim
A2Z CNC
1530 W Tufts Ave Unit B
Englewood CO 80110

tim@...
www.A2ZCNC.com

USA made accessories for desktop mills & lathes.
Specialized tools for the jewelry industry.

[You may be over-thinking this one, Tim. With CAD and CAM, it's pretty
simple to generate and cut patterns like the ones you point out, without
getting into any advanced mathematical equations. Most of them resolve into
linear patterns that are polar-arrayed around a central point; much of the
interest is in the overlappings that occur. Some others can be done by using
the offset function; starting with the outer ring and offsetting inwards to
the center, or progressively scaling down a figure towards a central point.
Even a simple sine curve looks interesting if repetitively arrayed in a
linear manner - it starts looking like one of Faberge's cigarette cases,
which were originally produced on a "straight-line" machine that combined
mechanical motion (following a template) with a hand-guided graver.]

Andrew Werby
www.computersculpture.com