[rescue] Vector Plotters

Justin Haynes justin at justinhaynes.com
Mon Oct 5 12:48:39 CDT 2015

Thanks!  Actually for #2 I meant to say 'vector' not 'raster'.  How does
the mechanism work such that perfectly true curves (or lines) can be made?

I understand with analog computers or analog electronic music synthesis,
Voltages can correspond to values.  In a sense, calculations can happen
with electrons taking the place of numbers.

How then do we go from digital math to curves being represented smoothly?
Is there a notion of a matrix which lines can be drawn smoothly between?

What should I read?


On Mon, Oct 5, 2015 at 12:21 PM, Carl R. Friend <crfriend at rcn.com> wrote:

> 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.
>    Cheers!
> --
> +------------------------------------------------+---------------------+
> | 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 |
> +------------------------------------------------+---------------------+
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