Adam Seychell wrote:
>
> Hello group,
> Has anyone here thought about building or even built a drum
> photoplotter based on a red LED laser diode ? This would be used for
> making printing masks, et. There has been much discussion among amateurs
> on building a CNC mill/drill machines, however I am under the impression
> that this is definitely NOT an task for the beginner, even if he/she
> has access the right tools. A drum photoplotter appears simpler in
> construction as there is only 1 axis required to position the light
> head. Basically the drum plotter works by rotating a relatively large
> drum with a film sensitive to red light (available from Kodak)
> positioned around the outside of the drum. The drum spins at fairly high
> speed (> 10 rev/sec) and the light source (red LED laser diode and
> focusing lens) slowly and accurately moves along the length of the drum
> in a straight line. The spinning drum sounds relatively simple to build.
> The moving light source looks a lot more complicated / expensive. My
> only thoughts how to go about this is to use a ball bearing screw and
> linear bearing. I priced some ready to go ball screw guided assemblies
> but the costs were prohibitive. Is there no other option ? I own a drill
> press and a small lathe in my workshop. I am open to all comments.
I've thought of doing it, but my epson is good enough for the moment.
It's currently used for some high resolution printers.
As for crappy light sources, you just focus the light to a converging
beam onto a ∗small∗ pin-hole in shim metal, then re-converge the
diverging
beam from the other side. The pinhole cuts out rays that are not
following
the ideal lens 'ray-trace' path. By choosing suitable focal lengths, the
dot on the film will be smaller than the pin-hole size. Other tricks can
be done to make use of laser pointers too.
The mechanics are easy but fiddly. Mount a laser diode to a platform
that
moves along a finely threaded rod, driven with a stepper. An
anti-backlash
nut is made with two nuts with a spring in between. A printer mechanism
could be used.
http://pico-systems.com/photoplot.html