[rescue] Vector Plotters

Carl R. Friend crfriend at rcn.com
Mon Oct 5 12:21:10 CDT 2015

On 10/05/2015 12:56 PM, Justin Haynes wrote:
> 1. Do any plotters exist with a mechanism for moving the pen in a smooth
> line rather than across a grid of discrete locations?  The pen still makes
> a relatively smooth movement, but this is simply a desirable artifact.

    If any such devices exist, they'll almost certainly be very old
and long-obsolete.  The accepted methodology for getting smooth curves
now is to reduce the step-size either through better stepper-motor
technology or gearing.  Also at play in this is that the tip of the
pen is likely some multiple of the smallest step size -- you won't
notice the stepping action, especially with felt-tipped pens.

> 2. In raster displays, lines look smooth, but I'd guess the line is still
> being created with many discrete movements, and they blend together for a
> similar reason as the pen on a plotter does - the electron beam cannot
> change directly quickly enough to make such tiny jagged edges.  Do raster
> displays exist which can accomplish an actual straight line?

    Raster displays, by nature, can only produce steps; get out a
magnifying-glass to see for yourself.  This is best viewed on a
monochrome display which won't have the colour-producing artefacts
present in colour tubes -- or worse -- LCDs.

    Vector CRTs, however do exist and typically, but not always,
make use of storage-tubes for the display.  These are capable of
producing perfectly true curves, but are long obsolete.

> 3. Finally, I think this has interesting applications for 3d Printers.

    3D printers will unquestionably use stepper motors with the
absolute precision down to motor-technology and gearing.  They
are too new for anything else.

> 4. I have no idea how a CDC machine accomplishes curves, but I suppose when
> you have a lathe or similar tool capable of smoothing edges it isn't
> critical.

    The answer is fine-grain steppers and large gear-ratios (lots of
turns on the stepper to produce one turn of the screw that moves the
tool).  In machining, time is not so much of the essence, but precision
is, and cutting metal happens in small increments anyway.

| Carl Richard Friend (UNIX Sysadmin)            | Boylston            |
| Minicomputer Collector / Enthusiast            | Massachusetts, USA  |
| mailto:crfriend at rcn.com                        +---------------------+
| http://users.rcn.com/crfriend/museum           | ICBM: 42:20N 71:43W |

More information about the rescue mailing list