braille graph plotter discussion

From: John Miller (
Date: Tue Nov 22 1994 - 09:52:54 PST

The spur wheel approach to raised-line drawings seems to me to be the
best engineering solution. Volunteers have made thousands of raised-line
drawings on a rubber mat for me. The rubber mat is showing no signs of
wear. My parents purchased the rubber mat I use at an art store. It was
sold as a drawing mat. I will try to get its name for Mike Romeo.

 Volunteers tracing raised-line drawings prove the concept that a spur
wheel approach is plausible. No vibrating pin technology need be
developed. The process is quiet. A person can trace a graphic quickly;
a computer should be able to do so, too. The resolution is acceptable.

The metrics of speed and accuracy may shed some light on the question of
which is better for a graphic embosser, spur wheel or vibrating pin. I
question whether a vibrating pin could draw a line with a speed anywhere
approaching that of a rolling spur wheel. For the sake of fixing cost,
choose an assembly of the same order of complexity for both designs. The
spur wheel requires a constant applied force. This force would limit the
spur wheel's acceleration. The vibrating pin assembly would not have this
limit on its acceleration. It could easily direct the light weight
vibrating pin to move across the page. Instead, the vibrating pin must
travel slowly across the page in order to maintain a high resolution
line. This speed limits the emboss speed of the vibrating pin.

The applied force and the rotating of the spur wheel define the control
problem for the spur wheel design. The shimmying of the vibrating pin
defines the control problem for the vibrating pin design. Of the two,
controling the shimmy of the vibrating pin seems a more difficult engineering
challenge than controling the motion of the spur wheel.

Tim, you are an applied physicist. What are your thoughts on the matter?
Incidentally, I repeated Robert's experiment. He counted 16 dots per inch
for a spur wheel. I count 15 dots including an end point. So say 16 dots
per inch is the outside of the resolution one can achieve with a spur
wheel. I understand what I propose would likely disable the text mode of a
Braille Blazer, but is there a simple modification that could be done to the
Braille Blazer printing assembly to increase dot resolution? It seems
to me that it is the stairstep effect and not the dot size that limits the
resolution of braille graphics made with traditional braille embossers.
Increaseing the resolution of where one can put dots on a braille page
would go a long ways towards addressing the problem. Comments?

John A. Miller
                   (619) 658-3876
member, National Federation of the Blind

This archive was generated by hypermail 2b29 : Sun Dec 02 2012 - 01:30:03 PST