--- In
Homebrew_PCBs@yahoogroups.com, DJ Delorie <dj@...> wrote:
>
>
> Adam Seychell <a_seychell@...> writes:
> > Thats what I have observed too. If you look at it under a microscope
> > then you can clearly see that line edges parallel to the print head
> > travel axis are much less jagged than line edges perpendicular to the
> > print head travel axis.
>
> Actually, that's not what I see. There seems to be a gaussian
> distribution of off-bys in both directions (vertical and horizontal).
> If I enable bi-directional printing, there's an obvious duality to
> that direction, but I think it's either (1) the various print heads
> aren't aligned to each other, or (2) individual dots don't leave the
> print head at a true 90 degrees each time.
>
> One of these days I'm going to write a program to print my image with
> only one of the jets and see, assuming I can wait all day for it to
> print ;-)
Use the print head alignment check or nozzle check, that will print
one line using one nozzle. That should give you some indication of how
straight one nozzle can print, independent of software/driver dithering.
I suspect part of the problem may be that a lot goes into writing the
drivers to -hide- those straight lines that the print head would
otherwise print. So that gaussian distribution of dot placement is
most likely by design.
Early inkjet printers often suffered from banding caused not by clogs,
but by the fact that the image was drawn by placement of drops in
straight lines. A lot of work went into dithering patterns to hide this.
> > I'm sure most printers do not print at the resolution manufactures
> > claim. I see pixelation errors when printing 6mil (0.2mm) lines
from my
> > Canon MP810. This printer is rated at 1200dpi (7 pixels in one 8mill
> > line) yet I see some lines are significantly wider than others
> > indicating the printer software is down converting the image to a
lower
> > resolution.
Inkjet printers, from my understanding, are "faking" the higher
resolution by micropositioning the print head. That the print head
itself is really 300dpi or 360dpi.
> On my laser printer (600dpi) I don't use 6 or 8 mil lines. I use 6.67
> or 8.33 mil lines, which are exact(ish) multiples of the print
> resolution. Otherwise, yeah, some lines are wider than others by a
> pixel.
There you go.
I had tried making PCB patterns using a dot matrix printer (long ago)
and ran into that same problem only at much larger line widths.
Steve Greenfield