Ok, that is a very different problem.
What you are running into is a result of calibration problems. The errors caused
by calibration are nowhere near consistant, they are curves that are going to be
different in different places on the workpiece. If you were to make a grid of
holes at a nominal 300mm spacing across your entire workpiece, you will find
that the errors are very different in different areas of the workpiece.
there are a LOT of things that can result in location errors (there’s a topic I
created a while ago, something like “sources of errors” that covers a lot of
The fundamental problem is that we don’t have a good way to measure small errors
over large distnces, and a 1mm error in the measurement of the distance between
motors can result in a 2mm error of vertical position in some places (and far
less error in other places) a 1mm error over the standard motor spacing is 0.1%
tape measures are not that accurate (see
Tape Measure Accuracy (class 1 / class 2) ) for
a discussion on tape measure accuracy)
So the calibration routine tries to setup cuts that you can measure that result
in maximizing and isolating specific errors in motor spacing and ring rotation
radius (as they are the most common sources of error) and correct for them. But
if there are other sources of error (say the machine flexing, which was a much
bigger problem on the 1st generation of machines that had a much worse
calibration routine) the result is not that accurate
Holey calibration takes more measurements and does more complex calculations, so
it seems to result in a more accurate machine.
1st check that your machine is not flexing as it moves to the different
locations (and as noted above, even a mm or so of flex is significant). This
includes checking that your motors are not moving on the beam.
Then get a decent tape measure (class 2 tape measures are not that expensive,
and even class 1 tape measures are dropping in price) and measure very carefully
(we really need to setup a routine to measure chain stretch, but that’s a
long-term problem). Try holey calibration, see if it works better for you.
Some people throw their machine together and report good accuracy, others
agonize over the details and struggle to get acceptable accuracy, we really do
not understand why there is so much of a difference.