Homebrew PCBs

When you look at the printhead mechanism, there is;

- a drive strap.
- a front and rear guide rail.
- a thin darkened transparency strip that passes between 2 'posts' behind
the printhead.

What's that thin transparency strip used for?  I figure it's for motion
control, but how does it work?  It seems uniform grey colour, but I think it
must be more than that, is it magnetized film with position markers?  Or is
it more of an optical device (my eyes can't make out lines, and I don't want
to touch it)?

I'm looking at what would be required to lift the printhead chariot by
1/16".  So far I've determined that the drive strap would most likely not
require displacement.  That darkened strip might still be within sensor
range, tests required.  The front guide rail just requires a 1/16" spacer on
the 'skate'.

The main obstacle is that rear guide rail, the printhead is clipped around
it.  One possible solution is to trim the bottom of the clip 1/16" and
adding a 1/16" shim at the top of the clip.  I haven't taken the chariot
apart yet, but the more I look at it, the more I think it would be possible
to modify this printer to accurately process 1/16" PCB.

Robert
:)



[Non-text portions of this message have been removed]

Hi Robert, that thin transparent strip is a linear encoder strip for 
the servo motor.  Yeah, I know, many folks in the CNC forums will 
tell you it is impossible to do, but it is VERY possible.  That's 
the funny thing about Epson printers, they use some pretty hi-tech 
stuff on their printers.

Anyway, the small DC motor moves the carriage back and forth. On the 
carriage, there is a quadrature encoder pick-up device that reads 
the lines on that strip.  This is resolved into the positional 
information to feed back into the motion control "Stuff".

It's really a neat little system - very closely mimics some of the 
very high-end optional features on industrial CNC machines.

Chris






--- In Homebrew_PCBs@yahoogroups.com, Robert Hedan 
<robert.hedan@...> wrote:
>
> When you look at the printhead mechanism, there is;
> 
> - a drive strap.
> - a front and rear guide rail.
> - a thin darkened transparency strip that passes between 2 'posts' 
behind
> the printhead.
> 
> What's that thin transparency strip used for?  I figure it's for 
motion
> control, but how does it work?  It seems uniform grey colour, but 
I think it
> must be more than that, is it magnetized film with position 
markers?  Or is
> it more of an optical device (my eyes can't make out lines, and I 
don't want
> to touch it)?
> 
> I'm looking at what would be required to lift the printhead 
chariot by
> 1/16".  So far I've determined that the drive strap would most 
likely not
> require displacement.  That darkened strip might still be within 
sensor
> range, tests required.  The front guide rail just requires a 1/16" 
spacer on
> the 'skate'.
> 
> The main obstacle is that rear guide rail, the printhead is 
clipped around
> it.  One possible solution is to trim the bottom of the clip 1/16" 
and
> adding a 1/16" shim at the top of the clip.  I haven't taken the 
chariot
> apart yet, but the more I look at it, the more I think it would be 
possible

> to modify this printer to accurately process 1/16" PCB.
> 
> Robert
> :)
> 
> 
> 
> [Non-text portions of this message have been removed]
>

--- In Homebrew_PCBs@yahoogroups.com, Robert Hedan <robert.hedan@...>
wrote:

> What's that thin transparency strip used for?  I figure it's for motion
> control, but how does it work?  It seems uniform grey colour, but I
think it
> must be more than that, is it magnetized film with position markers?
 Or is
> it more of an optical device (my eyes can't make out lines, and I
don't want
> to touch it)?

Chris is correct, it is an optical encoding strip. Clear plastic with
black lines printed on it.

> I'm looking at what would be required to lift the printhead chariot by
> 1/16".  So far I've determined that the drive strap would most
likely not
> require displacement.  That darkened strip might still be within sensor
> range, tests required.  The front guide rail just requires a 1/16"
spacer on
> the 'skate'.
> 
> The main obstacle is that rear guide rail, the printhead is clipped
around
> it.  One possible solution is to trim the bottom of the clip 1/16" and
> adding a 1/16" shim at the top of the clip.  I haven't taken the chariot
> apart yet, but the more I look at it, the more I think it would be
possible
> to modify this printer to accurately process 1/16" PCB.

Some people have modified their printers to accept CDs. That's roughly
the thickness of a PCB. I don't think they moved the print head up, at
least not in the way you are suggesting.

The C84 is hampered by not having a paper thickness lever.

Steve Greenfield