On 2010-07-13, Jon Elson wrote:
Karl Townsend wrote:
This is where autocad is a great tool. Draw it and print full scale. check
paper against part.

laser printers have gotten a LOT better since the early ones, but they
are still very inaccurate. If you can get .050" accuracy over the whole
sheet of paper, I'd be amazed. I'd NEVER try to do precision work this
way. print a document twice, once with mirror printing on, and hold the
two up to a light to see how well they align.

In particular -- the linear dimensions across the short
dimension of the paper tend to be more non-linear because they are drawn
with a rotating mirror and the laser -- trying to convert angular motion
to linear motion -- (with optics which attempt to correct the linearity
-- but are not perfect). The other axis is defined by the paper being
advanced by stepping switches, and might actually be more accurate if
the advance rollers do not slip. (Some plotters actually have grit on
the advance rollers which form a track in the back of the paper, so it
moves the same distance for all the passes back and forth to draw the
whole image. Overall, a good plotter is more accurate (at least to
start with) though the paper can shrink or swell with humidity changes,
so use it as soon after plotting as possible.

Enjoy,
DoN.

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