Re: [CAD_CAM_EDM_DRO] Breaking Printers

Dave Lantz wrote:

> this may be off topic, but i believe i've exhausted all other sourced, does
> anyone know how to calibrate a laserjet iii for precision. I have several
> here I need to make artwork PRECISELY, and would like to avoid modifying the
> files if posible, if it's simliar to a cnc setup, how can i calibrate it?

I hope this is close enough to on topic to be acceptable.

Most laser printers are horribly inaccurate at the mid-scale. To check this,
make up a regular grid of, say, 1" or 1 cm squares, and make several
copies. Turn one page 90 degrees to another and view them together,
or turn one over so the printed sides face together. You will find it
impossible to get the grids to overlap perfectly. Newer printers are generally
better than the older ones, but over a 2" square, you will often find cumulative
errors of almost .1"

I ran into this while doing printed circuit artwork, but the problem is the same
for all printing tasks. The errors are not consistant. There is paper 'squirm"
as well as highly repeatable errors in the laser lenses and the cosine error
from the rotating mirror. So, the axis that is swept by the rotating mirror (generally
the 8.5" dimension across the paper) has a very simple mathematical error that
is almost corrected by a lens, to form a very complex pattern of smaller errors.

A flat calibration factor won't do it.

Jon